The claims are pretty amazing. High efficiency, efficient over a wide range of temperature difference, high temperature differences possible.
The operating principle is totally different. It is based on acoustic waves. Not using phase-changes but just the ideal gas law (pressure and temperature are proportional). I tried to get my head around it, and I got it with a standing sound wave. But they use a traveling wave, for which I could not find explanations I understood.
The general idea is "lower air pressure and move gas to cold side so the gas heats up" followed by "raise air pressure and move gas to warm side so the gas cools down". That means the low pressure needs to be low enough that the gas gets colder than the cold side, and the high pressure needs to be high enough that the gas gets hotter than the hot side. Luckily that is 'just' a matter of amplitude of the sound wave. I think this is how they achieve their wide range of efficient temperature deltas.
That wide range is the main difference with a phase-change based unit. The phase change happens at a much more difficult to change temperature.
Really curious what kind of COP this technique can achieve. Cool tech if real, since it doesn’t need any refrigerant. Wondering if there are other downsides.
Non phase change systems are inherently more efficient because every heat exchanger (air/air, air/coolant and coolant/water) can be counterflow, allowing substantially greater efficiency.
In phase change systems, the 'hot side' and 'cold side' are all at the same temperature, which means any gradient in whatever you are heating/cooling is lost energy.
> The general idea is "lower air pressure and move gas to cold side so the gas heats up" followed by "raise air pressure and move gas to warm side so the gas cools down".
This sounds like Maxwell's Demon, where the work required to prevent the system from reaching thermodynamic equilibrium is equal to or greater than the extra energy. How does this differ from that?
Maxwell says that the effort you put in is more than the work you can get out. So the heat difference you get, even if converted perfectly to other kinetic energy, will always be less than the electricity input.
But we aren't after kinetic energy, or work. We are after heat.
I thought heat was a form of kinetic energy? Specifically, it is a measure of the kinetic energy of an object's particles, independent of the kinetic energy of the object as a whole. That not accurate?
Makes sense. I was thinking of it in context here. Seems the distinction between kinetic and thermal inside a heat pump is less useful that other places.
This is how a refrigerator works. No it does not violate the "Maxwell's Demon" thought experiment. Yes it does consume electricity, it's not for free. Efficiency gains are still good though.
Can you explain in more detail how it sounds like Maxwell's Demon? There's nothing that sounds like it sorts the air particles, so I don't see the connection.
Counterarguments to Maxwell's Demon is not that such chambers with a microscopic door cannot be fabricated, but that the Demon and his door cannot run without some entropy/power source outside to the chamber thereby negating the "negative energy" created by it. The Demon works if you don't mind feeding him and maybe adding fuel to the chamber as well, but then you're not getting the supposed free energy.
Another non-phase change method is the reverse Brayton cycle. Kind of like running a gas turbine in reverse. I think it is somewhat widely used in cryocooling, and in jet airliner cabin AC, but it seems to not have caught on for domestic heat pump applications. Presumably the traditional phase change approaches are more efficient in the relevant temperature ranges.
There is plenty of opportunity in being more efficient. To give an example, houses in the Bay Area has gray/black roofs. In the summer such roof receives about 10kW of energy and readily converts it into heat. Heat, which we are trying to evacuate from the house with our super-efficient heat pumps in the air-conditioning units.
If only we'd painted these roofs with white reflective roof paint (~92% reflection). We would have removed ~8kW of heating from such roofs! And then, maybe, we wouldn't have to pump all that energy into air-conditioning. So the surrounding air would be cooler, less noise would be heard from air conditioning, less energy would be spent. And the cost? 4 gallons of white reflective paint and a couple of hours of work, painting the roof...
> To give an example, houses in the Bay Area has gray/black roofs.
Those are no longer legal. Title 24 requires a “cool roof” *
When I had my roof re-covered a couple of years ago the roofer apologized and said he had to use a light color. Which wasn’t a problem for me so no apology was needed.
That's strange. We just built a house in the Bay Area with a black roof, and have never heard of this. It passed planning/inspection, and the thing you linked says we are in a title 24 zone.
We hadn't thought about it, and would likely have opted for a lighter roof, had someone pointed it out to us.
My understanding is that you can insulate your way to Title 24 compliance. You just have to have a total ingress performance over some level.
Now that said, it would still be better for our communities to reflect this energy back out into space to reduce environmental heating. Houses in my area at solar noon have almost half a megawatt of heating potential. By municipal code they are not allowed a roof reflectivity of more than 40%.
I guess having mirrors on all the houses could cause problems for other people, even for flat roofs. But I agree: reflecting the incident beams is important: when it emerges as heat (IR) it can be trapped by GHGs.
I had been thinking of the reflectivity benefit rather than the reduction in air comditioning.
Specular reflection (a mirror) would be ideal for sending energy back out into space most of the time but would occasionally death-ray your neighbors. White paint isn't quite as good (some of the diffuse reflection will hit non-reflective things) but it also won't incinerate anything. Feels like a good compromise.
Unfortunately, we are losing some of this cumulative knowledge due to it not being documented, and due to the looks of alternatives (although the grey buildings in the US are as ugly as it can get)
We're not losing the information that light colors heat less in the sun. Neither could anyone who spent five minutes on a black roof in the sun forget that tidbit. It's just that other factors than the energy required to cool a building took precedence in the past.
Anecdotally it seems like we are. The rad thing to do in my area of california is to paint your white washed spanish style home mud brown or ozzy osbourne black. Then you have to install a much more powerful AC system when in the past maybe just opening windows and getting crossbreeze was enough. All these houses used to have awnings over sun facing windows when they were build in the 1920s but at some point that must have been seen as ugly and its now pretty rare to see.
They're only cheaper in the short term. Long term energy costs and replacement costs factor in strongly, and chances are that once you make that calculation you'll end up with old fashioned terracotta roofs being cheaper over the life of the house.
I don't really like how the old fashioned terracota roofs behave during the summer. They heat up during the day and release that heat in night time, driving the inabitants crazy with heat. Maybe with some kind of ceramic coating to increase the albedo they'd be okay.
If the roof assembly is decently insulated, then relatively little of that 10kW heats the house. So, while improvement is available, it’s not nearly that large.
Still, though, I have to wonder what the equivalent "CO2 reduction" would be considering that a white roof is likely to radiate most of the incoming sunlight back into space, where if it is radiating in infrared then that heat is more likely to be trapped on Earth.
For now, everyone is free to pump out kilowatts of heat with their roofs, parking lots, air conditioners into the surrounding air. It is not considered pollution, even when it is already 100 °F outside.
On the days when there is an inversion in the atmosphere, the hot air stays trapped. People have to run ACs in their houses, stores and offices. And that results in even more heat routed to the place, with ACs units, literally pumping energy from the solar arrays somewhere in the desert into the city.
At this time last year, this region was subjected to a 'heat dome'. Luckily this building has a 'cool dome' in the basement. Spent a few days listening, reading and solving down there (12-16°C cooler).
Much cooler temperatures (13°C) are found just a few feet below ground. (Memorable to those who've visited 'root cellars.) Before long those mysterious 'underground cities' in Anatolia may not seem so mysterious. It's a low-cost, low-tech, zero-energy solution, used by native communities in many regions of the world.
> Much cooler temperatures (13°C) are found just a few feet below ground. (Memorable to those who've visited 'root cellars.) Before long those mysterious 'underground cities' in Anatolia may not seem so mysterious.
When the London metro was built (over a century ago), the clay was at 14 degrees C. But over time, it heated up from all the power dissipated by the metro system. Now it is around 20 to 25 degrees C and doesn't really act as a heat sink anymore. The same happened in the NY subway.
So soil can act as a great heat sink for a while, but not forever. I suspect the same would happen if you'd put a modern city underground and relied on the temperature of the soil instead of pumping heat out somehow.
This and geo-thermal. The crazy megalomaniacs pushing solar are as bad as the rest of oil/coal kingpins, unsustainable and another ecological train-wreck in progress.
You can look at how much space roofs cover in the suburb in the Bay Area. It'd be roughly 25% streets, 40% roofs, 30% backyard, 5% front-yard. Adding white reflective coating increases "Solar Reflectance" and decreases "Thermal Emittance" and absorption. Most dark roof materials reflect 5 to 20% of incoming sunlight, while light-colored roof materials typically reflect 55 to 90%. A white roof coating that you can purchase at your regular home improvement store would do that 90%.
So effectively, in the suburban area there is an opportunity to change our average solar reflectance by ~32% [(90% - 10%) * 40%]. If we just abandon the idea that a good house should look like a house in Normandy and have a black roof.
[edit: I've opened a section of sat map (in Sunnyvale, near Reed Ave/Sequoia Dr.) and estimated roof/street/backyard/front-yard by area, for a lot of 2 houses and adjacent street. The numbers above are from that estimate. Heat and noise of ACs is somewhat local (urban heat island effect, etc), so that local estimate is what counts. It is not surprising that we can have 40% roofs. Land is expensive in the suburb like that.]
As per: https://en.m.wikipedia.org/wiki/Reflective_surfaces_(climate... - "If all urban, flat roofs in warm climates were whitened, the resulting 10% increase in global reflectivity would offset the warming effect of 24 gigatonnes of greenhouse gas emissions, or equivalent to taking 300 million cars off the road for 20 years. So it seems, there is not only local/urban heat island effect, but even some global effect. To put this into perspective, Tesla sold 2 million vehicles. No idea, if the Wiki numbers are correct...
I'm not aware of any stats, but I've experienced the difference between hot neighborhoods and cooler neighborhoods, right next to each other in Houston. It would be great to have a quantitative measure for this effect, similar to a walk score (which isn't perfect, but can be occasionally useful).
Are you sure it’s because of AC and not the amount of concrete pathways compared to green areas, vegetation and shade from trees? Also various thermal properties of the ground?
Even if houses were 50% of the land area, they take up a miniscule amount of air volume. Also, hot air floats up, so there is little chance you could feel the heat from an AC outside.
On the other hand, if the earth is hot because you have few trees, you will feel it everywhere when walking on a sidewalk.
In Europe at least it’s common knowledge that you need to have trees and greenery everywhere to make heat bearable outside. If you replace trees and grass with concrete you get an island of heat that will be unbearable during summer to walk through.
Yes this. It helps but it isn't a magic bullet because the roof is already airgapped from the roof and the house insulated from the attic. If the roof was directly insulated shingles would curl up and start failing within one or two summers due to the heat. That is why there are roof vents, gable vents, and soffit vents, to let air freely flow into and out of the attic/roof cavity.
As far as I know, it’s important to have outdoor air that flows under the roof in cold climates to avoid ice dams. Otherwise insulating the roof deck is just fine and possibly even advantageous.
An unconditioned attic is not so great because it’s difficult or impossible to do a good job of avoiding leakage into the living space. Also, any mechanical equipment in the attic would like to be in conditioned space.
> If the roof was directly insulated shingles would curl up and start failing within one or two summers due to the heat.
This is an old school carpentry trope and yet I've never actually seen any statistical evidence indicating that roofs over vaulted ceilings which are directly insulated must be replaced more often than non-vaulted.
In every vaulted ceiling ive ever seen or worked on it still has had a significant air gap between the insulation and the roof and it was still vented with roof and soffit vents. Also the areas that tend to leak before any other part of the roof because it is hard to vent enough air through such a small space.
And nearly every roof ive worked on that had curled shingles lacked proper roof ventilation. That isn't direct evidence, but ive never seen curled shingles on a well ventilated roof either and the only common factor in curled shingles is heat buildup in the attic/roof cavity.
Anecdotally we have about 1/3 of our roof with a vaulted ceiling and the other 2/3 with an attic. The side with an attic is the side that would be suitable for solar panels (more sun at the right angle) or adjacent to the vaulted ceilings. The leaks that came up were all on the insulated vaulted ceiling side; starting about 25 years old, and we had another every couple years for about five years until replacing the roof. The attic parts never had any problems.
We have a vaulted ceiling and there is still an air gap under the roof. The ceiling "vault" is separately framed; there is still a foot or two of air space between the top of the vault and the roof deck.
Black / dark tile roofs across the south are completely ridiculous. I doubt people understood this when shingles were first developed but we do now and we should adjust accordingly
That’s not it in Australia - we don’t use asphalt roofing. Normal roofs are tile, steel or (more rarely) zinc here.
I think the US is fairly unique in that regard. I’m so used to our houses here that the idea of using shingles made of asphalt just seems bizarre to me.
The main reason they are dark is because they are made with oil.
Asphalt tiles are fairly cheap, and that's a good thing. It's the labor that makes up most of the cost of a roof.
I'm trying to get up the nerve to shingle my four bedroom home, and it's not the cost of materials I'm worried about. It's my body.
My fear with global warming measures is the poor, and middle class, will be required to bear the brunt of the preventative measures.
I guess the race is on to develop a 50 year life expectancy, but reasonably priced, white shingle? They might be out there? I really haven't researched them.
If anyone knows a cheap roofing contractor in the Bay Area, please divulge?
Twenty years ago I had a estimate of $25,000. I think that's too much now. I'm a ex General Contractor.
Yea, but trying to squeeze more out of the lower middle class, and poor, dosen't seem kind at this point in history.
I see a lot of virtue signaling out there.
Most of us can't afford a electric vechicle, and those federal credits seemed to just go to people whom could afford any vechicle.
I can't even afford the smog check, and registration, on my 4 banger toyota. A Truck I've keep going 20 years. It uses very little gas. (My vechicle has always been tuned up properly. I thought by now we would have had free smog checks for the poor? In CA we have a low income deal that was enacted when CA decided to require smog checks. It's so complicated most people don't use the "gift". You need to bring your car to a mechanic in order to get any money back. Shade Tree mechanics are out of luck.
My point is the corporations/government will pass any Global Warning measures down to us.
We are already tapped out.
If we are really serious about Global Warming lets go after the wealthy boys first. Take away their private jets.
And enough with their Globalization. If they can make a product that dosen't need to be shipped long distances, have them make it here.
I'm a Democrat, and winced when Biden pretty much gave a FY to the oil companies in order to sound Progressive. I knew at the time, the poor can't afford to pay more for gas, and natural gas.
Now--I don't blame the president for this spike in gas prices, but I would have rather have him say this is a big problem, and we can't just do away with oil.
Be it my PG&E bill that just seems to go up, and the $6.69 gas at my Chevron station, the poor are already paying to much of their income on a complex problem. (My gas station raised their prices the minute they started talking about inflation, and the Russia sanctions. It is pure greed. They made a record profits in the past few years.
Sorry about my rant. I just don't like being squeezed so much, while my wealthy neighbors buy crap from Amazon, and think they are doing their part by driving a Tesla.
When I left California I was driving a ‘67 ford galaxy which, being over 25 years old at the time, wasn’t required to be smogged anymore and was fully surprised when they made me do it when I registered it in Arizona (where it is anything post-66 has to have smog). Even my motorcycle had to be smogged (which, I believe, California doesn’t require) and that thing couldn’t help but get really good gas mileage.
So, fear not, a couple more years and you will be smog exempt.
My daily driver is a 1955 and I'm exempt from safety inspections at this point. I also have a one-time(!) $175 registration fee in my state. If you can keep up with the basic maintenance (grease certain joints every couple thousand miles, etc)the lack of regulatory oversight on these older vehicles can sometimes push them back into being more affordable than driving a 10-15 year old car. Just don't get in a wreck in them, crumple zones weren't really invented until the 90s.
No--in CA it's 1975, or earlier. It's a rediculious law because the old cars do not put that many miles on the road. I wish it was 30 years.
While I'm on my soap box; Neusome (a guy I went to high school with (Redwood, and voted most Fashionable, a liberal Marin county boy) has a bill on his desk that would do away with fees associated with Parking Tickets. As of today, he has not signed off on it. The only reason I can think of is he's getting more middle of the road for a run at the big office?
These extra fees and fines are not fair to the poor. A parking ticket in SF is running $80 bucks without fines. $5-6 an hour if you find the right spot.
Neusome knows this personally.
He barely graduated from Redwood High School, and dropped out of college due to some nebulous learning disability. He opened some coke dens in SF, and a few Bootjack liquor stores with family money. The SF bars went up in flames because they were poorly managed. Oh yea, his cousin Brendan has a DUI that disappeared? I might write a book on this guy one day. While I seem pissed, he's better than the alternatives.
If he wasn't born wealthy, he would be in the Embarcadero in SF with a needle stuck in his arm.
You can easily do it yourself, I did it first on a chicken coop to practice and once I got the hang of it I did a 145 square meter roof on top of a two story building in relatively short time. The clock was ticking because we were about to have frost and that makes working on the North side of such a roof next to impossible. If you have to remove the old stuff first use a flat shovel, that works the fastest compared to more fancy tooling.
Make sure you invest in a proper safety harness, they're not that expensive and even if I really hope you won't need it you'll be very happy you did that in case you do...
We recently paid thirty for asphalt, simple design, under US average size.
I once knew a handyman that swore by painting over black membrane roofs with some sort of white rubber patch paint. It was probably a terrible idea, but I wonder if such a product exists for asphalt roofs.
Seems like a better idea to cover the roofs with PV panels, to be honest. This would reflect heat and provide power for the cooling / travel / regular house electricity.
I have photovoltaics on my roof. I won't be doing it again.
I'm almost certain that putting the money that they cost into making my home more efficient in the first place, by doing things like sealing leaks, upgrading the insulation, and, yes, making the roof a lighter color, would have reduced our energy consumption by more than the amount that the PVs are generating.
The PVs absorb a lot of thermal energy, too, more than the shingles themselves do. So they make the roof hot. You can actually feel the difference inside the house - the rooms that are underneath the solar panels get warmer in the summer than the ones that aren't. So some amount of that electricity we're generating would seem to just be undoing the effects of the PVs on the house's thermal situation. There's still a net benefit, but probably because we're people who are inclined to accept that summer is hot in the first place. Trying to keep those rooms at or below 80F/26C might be an expensive endeavor.
Also, I've discovered that one does not simply have a roof leak fixed when there are solar panels on the roof, because they are in the way. So maintenance has been rather more expensive than I expected.
In general, I'm sanguine about solar as a renewable option. I'm just increasingly inclined to believe it's better implemented as an industrial technology, and that homeowners probably have better options for greening their houses.
Interesting. My PVs have made the house substantially cooler. There is an air gap between the panels and the roof itself - they effectively shade the roof.
Same. This statement is bizarre to me. You can’t bolt solar panels directly to a roof. There is an air gap from the rails and also the edges of the panels.
Are you in a mobile home or something?? I have solar too and I absolutely love it. I’m not sure how anyone could feel warmer in a room with panels above as i’ve never seen a stick house without attic spaces and i’ve used my IR camera to look for hot spots and i see nothing out of the normal where any panels are… also, panels tend to cover the entire surface area where the sun is shining the most too not just rooms so it makes no sense to me read what you’re saying.
To make solar worthwhile we did an energy audit so we also replaced windows, got new siding and installed new doors. Energy efficiency doesn’t have to be mutually exclusive. I got a bigger rebate from the city with proof of energy audit.
as far as roof repairs… why would solar matter and why so many roof repairs? I’ve been through tropical storms, down pours and many a hail storm and not a single problem and my roof is 23 years old..
I could never go back. I charge my Tesla at home and my electric bill averages about 70 a month over a year after solar. That’s less than a weeks worth of gas for my Jeep.
year 6 on panels and 0 maintenance with a 20 year guarantee on efficiency and install warranty if i had problems i’d call my installer for service.
>> The PVs absorb a lot of thermal energy, too, more than the shingles themselves do. So they make the roof hot. You can actually feel the difference inside the house - the rooms that are underneath the solar panels get warmer in the summer than the ones that aren't.
I've actually read the opposite: most PVs don't sit directly on the roof, but rather a few inches above it. And that air gap further limits the amount of solar energy that makes it onto the roof and into the attic.
That claim doesn't really add up. I have solar panels as well and yes - not only is their an air gap, but pretty obviously the rooms they're over are north facing (I'm in Australia) with north facing windows and obviously get hotter anyway due to that.
I came across a forum thread for Baja California, where thay have and discuss off-grid air conditioning in a very hot area of Mexico. Interesting discussion.
> The PVs absorb a lot of thermal energy, too, more than the shingles themselves do.
I've found this to be interesting going back as far as middle school, where we're taught renewable energy sources like solar panels can help reduce global warming by replacing greenhouse gas emitting alternatives. Yet fundamentally, they are designed to turn the only external source of energy our planet receives (sun light) into heat and other forms of energy that will eventually become heat rather than reflecting it back out into space (albeit through the atmosphere). Seems so backwards to me.
The problem we're trying, broadly, to solve right now isn't "we're directly heating up the planet" but "we're trying to stop trapping heat in the atmosphere through a potentially self-propagating greenhouse process".
This is why carbon neutrality is the focus and not just purely energy usage.
A better argument for solar panels is that per kwh of useful energy, a solar panel traps less solar energy (in kwh) than the CO2 produced by coal or gas or w/e. But I've never see this particular argument made and therefore couldn't even guess at HOW much better a solar panel is than coal and HOW much worse it is than nuclear or geothermal (which could actually be net energy loss for earth, by dispersing some thermal energy locked deep within the earth out to space).
> A better argument for solar panels is that per kwh of useful energy, a solar panel traps less solar energy (in kwh) than the CO2 produced by coal or gas or w/e.
It's not a better argument because the solar panel doesn't "trap" the energy. At most it borrows it, eventually it will radiate back out if allowed to do so, just as it would if it were absorbed by a rock. Humans do not occupy enough of the surface of this planet to make a dent in that.
The thing that will keep it from radiating back out is greenhouse gases in the atmosphere. And unlike some brief capture of energy, the greenhouse cycle is essentially a chain reaction.
But it is radiating it 'back out' less efficiently than a white roof. Thus black solar panels may indeed be a net negative if every building otherwise would have had a white roof.
In a land of mostly dark roofs it's probably a net positive.
Unless you pump the energy deep in to the ground it will still eventually find its way to radiate back out in the form of infrared blackbody radiation. The timescale we're talking about isn't very long in the grand scheme of things, and the entire surface of the planet is doing this to some extent or another.
Even if we did one of those megasolar projects people like to talk about like paneling the whole Sahara or Mojave, we would still only be absorbing a tiny amount of the petawatts per second the sun is constantly bombarding the planet with, much of it being absorbed by plants, the ocean, darker rocks, etc.
Our solar panels just don't hit the scale that the melting ice caps do, and the only thing we can do to stop that is reduce the flow of new ghgs into the atmosphere.
That doesn’t follow. Consider the alternatives - thermal generation (including nuclear) must reject massive amounts of waste heat into the atmosphere, before the electricity is used and heat is generated from that use. That’s what cooling towers are designed to do.
That’s even before thinking about the effect from CO₂ or methane from gas fugitive emissions.
The earth has the ability to radiate away quite considerable amounts of heat luckily, and solar produces considerably less waste heat than thermal. So solar and wind can only make things better.
Minimising waste heat is of course good, which is why energy efficiency is so important, and heat pumps are doubly so - because they are extremely efficient, but also because they don’t produce as much heat but transfer most of it!
Yeah, it’s a little counterintuitive, I’d just keep in mind that the amount of energy we use is tiny compared to the amount that the sun bombards the earth with. The absorption and generation is going to be insignificant compared to the amount trapped by the addutional greenhouse gasses.
That’s not correct - nuclear power plants only have efficiencies of about 33-37%, so 63 to 67% of the energy that nuclear reaction is producing is dumped into the atmosphere which wouldn’t have otherwise (obviously there would have otherwise still been some radioactive decay of the material in the ground if it wasn’t used as nuclear fuel, but nothing like refining it and bringing it to a critical mass in a reactor).
Meanwhile, 100% of the energy that a solar panel receives (and radiates some back as heat) would have hit the earth anyway.
More of it is reflect back into space from many natural surfaces than from solar panels. Not scientific but look how black this solar farm appears compared to the surrounding land
It's mainly the visible wavelengths that can get through the atmosphere. You should see the absorption spectrum for water, it's remarkably transparent in the visible! That's how the greenhouse effect works - longer wavelength thermal radiation is blocked by greenhouse gasses.
It also heats up dark surfaces. One way to remove that heat would be to have some kind of combined PV + solar thermal panel. The other lower tech option is to cover your roof with soil and plants, which release the heat back during the night. Vegetation is esentially a heat buffer.
Right and so to follow this logic through, how do you think we get energy out of fossil fuels? Or nuclear reactors? Or a hypothetical fusion power plant?
> they are designed to turn the only external source of energy our planet receives (sun light) into heat and other forms of energy that will eventually become heat
How does a steam turbine work? By heat: we burn things to get heat, and use steam to turn it into work which..turns it into heat.
Your own statement is arguing against using energy in the first place, yet trying to frame it as a "renewable energy" problem as though the 60% of energy in gasoline isn't being thrown off into the environment, and 30-50% of energy in coal isn't the same, or as if literally every last bit of that - all of it because of the laws of thermodynamics - isn't eventually turned into heat.
Total estimate energy consumption per year [1] is about 14420 TWh as of 2021. The total solar energy we would've received in that same year [2] is 1,515,480,000 TWh. Or 0.00095%.
The amount of thermal emission from human activity on Earth is negligible. The idea that the amount of solar panels to power human civilization would have any non-local effect on the temperature of the planet is absurd.
I wasn't arguing against the use of solar panels, just pointing out that they don't reflect light as much as the natural environment that would have been in their place. This whole discussion is purely academic because the proportion of earth covered by solar panels is negligible.
Actually, I was looking into installing solar, to offset $400/month of air-conditioning costs, during the summer. I could have had around 1.5kW of solar. But the cost of this is north of $25k, plus all the hassle to get the permits, plus all the extra complexity. While the cost of painting the roof is $100 + work. And now it is very rare that I have to run the AC.
I think your math is off my an order of magnitude somewhere. Your $25k can buy a 40Kw kit according to this¹ South African retailer (excl installation, but my point still stands.
Also, don't unferestimate painting a roof. I recently had my ~400m^2 roof painted, and the final bill was 50k ZAR (~3k USD), and this is in a country with dirt cheap manual labour costs. It's a very labour intensive operation if done properly.
I was looking at installing a very small solar array, just to offset the AC costs. The quote for the solar kit that could produce ~1.5kW (2170W Solar Kit: 7xURE NSP 310W - Mono 60 Cell - All Black Panels + 7xEnphase IQ7
60-Cell Microinverters w/QCables + 1x Enphase IQ Combiner 3 + Wireless Monitoring) was $6.5k.
But, I was also considering having a 10kW battery to store that energy and to have a backup power, like Tesla Powerwall - $10k. And then there was work to install, permits, my time. Overall my estimate was, realistically it'd be ~$25k. Maybe I was wrong.
On my house I have two sections of roof that are flat/horizontal. Roof is pretty thin there and although there is insulation, on hot days ceiling was getting worm in the 2 rooms under these sections. I also was hoping that an extra layer of solar would insulate my roof a bit more. So I wouldn't have to run AC that much. So the hope was to stop wasting annoying $400 on AC in the hottest months. But the cost of installing solar felt prohibitive. So I've made a quick calculation and spent $100 on the reflective roof paint instead...
We have an enphase system with a solar array that's a bit under 10x that size. We paid about $60k (ignoring tax credit) in the bay area, and I think we overpaid.
We have about 2.5 watt hours of battery per watt of solar panel, which seems about right around here. (The battery is fully charged by the end of day about 95% of the time.)
Your quote has 6.6 Wh/W, and the PV bit is small, so fixed costs are also biting you.
Edit: we have electric heat, and you probably don't. Our worst case days are cold and cloudy, so perhaps the battery sizing makes sense, though if you want AC at night, you'll want enough solar panels to charge the battery and run the AC.
I didn’t get the battery but paid 28.5K (without rebates) for a 12.8kW array. I think that’s very reasonable. Heating, cooling and car charging are covered with around 6mWH capacity left a year. Thinking of converting my water heater now.
I like our Ruud/Rheem hybrid heat pump water heater. (The two brands are the same company. The only difference is whether you pay someone to install it.)
However, it was not trouble free:
The time of day scheduling feature is useless. Once or twice a month it gets stuck in "lower temp" mode. The app reports kWh used and displays alerts, which is nice. Otherwise, there's no reason to give it WiFi access.
Pay for the leak detector option. It's relatively cheap, but not included for some reason.
You're likely to have condensation issues unless you use a good installer, or do it yourself and follow directions.
The power lead on ours wore through due to vibration too, so pick someone that's experienced/conscientious enough to route wires carefully.
Solar panels are $2-$3 per watt depending where you live. 4x300watt panels is just the ticket, depending where you are and whether you can get a 30% tax credit that's about $2000.
Whole thing all together would be about $5000. It would generate about $1 of electricity a day. Would eventually pay for itself over its lifetime if you don't mind faffing about with it to get started.
> On my house I have two sections of roof that are flat/horizontal. Roof is pretty thin there and although there is insulation, on hot days ceiling was getting worm in the 2 rooms under these sections. I also was hoping that an extra layer of solar would insulate my roof a bit more.
That’s insanely cost prohibitive, tbh. No wonder more people aren’t jumping at the opportunity. You would need 14 years just to pay back the cost of installation, and that’s assuming zero maintenance simultaneous with magically sustained like-new performance.
After those 14 years, you “make” an annual non-compounded 7% ROI (again in 2022 dollars).
Spending some of that money on insulation and sticking the rest in a savings account somewhere is a much wiser bet.
The batteries are often rated for 20 years, after which you're down to 80% capacity, they don't simply stop working. Solar panels are rated for 30 years. So yeah, pretty hands off.
As for why do it, well, a right sized system allows you to be independent from the utility company so if monthly financing for it falls to the same ball park you're paying for electricity already you've simply locked in a rate and hedged against further price hikes.
If I was paying on average $99/mo to PG&E or whomever I'd eyeball a $12,000 system financed over 10 years. That would get you about 20kWh storage and enough panels to keep it full which may or may not be enough for your house.
That crossover point obviously varies from house to house and what's available to you locally. I think it makes a lot of sense for new houses, that way they might avoid a potentially very costly hookup to the grid which in some locations is tens of thousands of dollars in itself.
I’ve never understood the calculations people make to justify that solar roof panels save them money.
Every time I do the calculations, it’s money loss.
If you want to install them for environmental reasons, great. But don’t kid yourself that’s is a great investment. It’s not. Putting the money into an S&P 500 index fund for 14 years is a better investment. It will double about twice in that time.
If everyone does that, all your stock won’t be worse much when the world will be either at war or starving. People have kinda forgot to think long term clearly. Also, you must live in a country where the politics are very anti climate. In my country it’s a good investment to install solar power.
It shouldn’t cost you more than $2/Watt. Obviously if you only do 5 panels, you still have all of the interconnect cost and it’s not nearly as efficient.
> The quote for the solar kit that could produce ~1.5kW (2170W Solar Kit: 7xURE NSP 310W - Mono 60 Cell - All Black Panels + 7xEnphase IQ7 60-Cell Microinverters w/QCables + 1x Enphase IQ Combiner 3 + Wireless Monitoring) was $6.5k.
Remember to take 23% off for the federal tax credit.
> But, I was also considering having a 10kW battery to store that energy and to have a backup power, like Tesla Powerwall - $10k.
That's a not-so-small detail, accounting for $18.5k of the bid! A battery is also pretty unhelpful for reducing the A/C portion of your electric bill, especially since most traditional A/Cs require more than the 20A that the Enphase 10kWh battery can output and will pretty quickly drain any home backup battery that could support that current demand.
> So I've made a quick calculation and spent $100 on the reflective roof paint instead...
$100 in reflective roof paint, while a great measure to take, isn't going to reduce A/C electricity usage more than PV, which has the added benefit of offsetting your other electricity usage when you are not in the cooling season.
The enphase batteries are stackable to get more amperage. However, we were definitely amperage limited when we sized ours. We have a few high amp / low duty cycle devices.
It can definitely run our 60+ amp HVAC system, but not overnight. (We didn't buy it for that, but it's nice that we don't even notice our frequent, short outages until enphase and pg&e email us...)
Changing how roofs are approached (color, materials) may also have a (possibly beneficial) hydrological effect, even better would be some form of vegetation grown on roofs (likely called 'green roofs' to some) to help with evapotranspiration for facilitating a small water cycle (helping water vapor travel inland) and reduce the 'urban heat dome' effect.
This is one of the reasons metal roofs a nice, they reflect heat and you don't need to paint them white, they make special paints for metal roofs that help reflect the heat and also look nice.
I'm in the UK and in the process of installing underfloor insulation in a house built around 1890. It is a flooboards-up job involving a windproof one way moisture permeable membrane above the joists, with hygroscopic insulation on top, and then a vapour control barrier on top of that, with all edges of layers taped to the joists where possible, all holes for wires, pipes etc. sealed with tape, and finally membranes brought up to wall behind the skirting boards. It's going to cost around £1k for a room of about 25m2. We have double glazing, the walls aren't particularly cold in winter, and the roof is insulated. I'm convinced most of our cold is coming through the floor and I reckon this job (along with the rest of the house in time, ugh) will make a huge difference.
But I'm having to do it myself because there are literally no specialist fitters where I live, and there are no government incentives that I am aware of. Why aren't the government going hell-for-leather for insulation etc.?
What happens to the "heat" energy that gets reflected by white/reflective roofs? It seems like it'd stay in the relative vicinity of the house, heating up the outside air further (even by a small amount), right? If that's the case, are there diminishing returns to worry about with effectively just moving heat from one place to another, assuming the (hotter) outside air will probably continue to warm up the house anyway? Do we just bank on something else absorbing the energy instead? Does it leave the area/atmosphere if nothing absorbs it?
(Please don't take this as a rhetorical "this is why X solution doesn't work" -- I'm no expert here and am just curious where all that reflected heat/energy goes!)
All that energy started at the sun, we call it "light" when it's visible and "radiation" when it's outside our visual range, but it's the same stuff.
The fact that it reached the roof in the first place means the atmosphere is transparent to it. So with a white roof, the wavelengths being reflected are the same ones being received, it'll reflect right back through the atmosphere and back into space. Effectively it just increases the Earth's albedo a tiny bit.
Any wavelengths which were gonna heat the air by absorption, were absorbed on the way in and didn't reach the roof in the first place.
HOWEVER.
In the case of dark/black roofs, the heat DOES stay in the vicinity of the house, at least for a while. The radiation was absorbed by the roof, and now two main things happen to it:
One, the hot roof heats the nearby air by convection. This is the main contributor to the "urban heat island" effect. Eventually this warmed air mass will affect weather patterns, but even before that, it just makes the place feel hot.
Two, the hot roof emits its own radiation, in a whole range of wavelengths determined by its absolute temperature, according to Planck's law. This includes infrared wavelengths that the atmosphere is not transparent to (the absorption region between 5 and 8 microns), so that radiation IS absorbed by the atmosphere and heats it as well. And just like convective transfer above, the warmed air contributes to heat-island and weather effects, etc.
(The phenomenon of a hot object emitting its own radiation is why thermal cameras work, by the way. And if you get the object even hotter, the Planckian locus shifts into our visible range and you get an object that is "red hot", or even hotter still and it's "white hot", etc. This is why the "whiteness" of lightbulbs is expressed in Kelvin, that's the temperature of an object that would glow the same color as the bulb emits. The "warm white" and "cool white" are misnomers; the so-called "cool" color represents a much hotter blackbody source.)
> Any wavelengths which were gonna heat the air by absorption, were absorbed on the way in and didn't reach the roof in the first place.
What is the basis for this? Intuitively (I am no expert) it seems more likely that the amount of thermal energy produced would be a function of the distance light travels through a medium and the amount of energy carried by the light in the first place. So I would expect that the "inbound" light would produce more thermal absorption energy than the reflected "outbound" light, but it wouldn't arbitrarily all be absorbed on the way in.
It was a bit of an oversimplification on my part, since for a given wavelength, the atmosphere isn't binary, completely transparent or completely opaque (i.e. the radiation would go a very very short distance before being absorbed), but for _most_ wavelengths it's _very close_ to binary. Either it's absorbed or it isn't, to a first approximation.
Yes, some wavelengths are absorbed very weakly, and some are scattered rather than absorbed. But these represent a tiny fraction of the spectrum, the nuance would've overcomplicated the post, and they don't change the result much.
For wavelengths that are not absorbed, they can be reflected back out just as easily as they came in. For wavelengths that're strongly absorbed, they heat the first parts of the atmosphere they encounter, and this is why the thermosphere is called that.
For those few wavelengths that're weakly absorbed, yes they produce some heating on the way in, and if you reflect them back out, they do produce some heating on the way out. But as you've said, because the intensity of the radiation is decreasing along the whole path, the "outbound" contribution is weak indeed. It turns out to be basically a rounding-error in the thermal contribution, which is overwhelmingly dominated by blackbody absorption and re-emission, which often does produce wavelengths that're strongly absorbed. On a perfectly-white planet (or snow-covered region), you might have to start caring about weakly-absorbed wavelengths, but for most types of ground cover, other effects swamp it.
“Heat” from the sun that we feel is mostly IR/Visible light. Mix of stuff happens if we reflect it with white surfaces. Some of it does go back into space. Some of it will get reflected by the atmosphere back towards the ground. IR light is also directly absorbed by the air molecules, but very little. Air is mostly transparent at visible wavelengths so it absorbs very little energy. Solids are much better at converting IR to thermal energy. Realistically air conditioning is just moving heat from one side of a wall to another. Overall painting buildings white won’t change the temperature of Earth, but it does help the building in question, which is all air conditioning cares about anyways.
I would assume those light rays reflect off the roof instead of getting absorbed…in that case the heat is absorbed into the atmosphere, I have a hard time believing it sits around the house and lingers there for any significant amount of time (doesn’t heat rise?)
With a light or reflective surface, a lot of the energy is reflected as light so it's not converted to heat. Relatively little will be absorbed by the air near ground level, heating the air only a little.
In northern New England, we see a lot of homes using heating oil and woodstoves. These create a lot of local emissions and can be expensive or use a lot of time/effort (woodstoves). Heat pumps that work especially well in cold climates would be a huge efficiency gain over oil, woodstoves, and electric resistive space heaters which are also commonly used as stop-gaps in the region.
Hell most of the 1950s and 1960s Bay Area housing stock is worse - it’s tar and gravel roofs without any significant insulation thereby turning houses into ovens. The right answer to most of them is a new foam roof which both provides insulation and reflectivity being white but people get quite upset about the foam roof thing, especially with Eichlers.
I always wondered why in such climates we don't simply stick mirrors on the roof (cheap) but solar panels would seem to be the best option in the longer term (much more expensive than either mirrors or white paint). But you are absolutely right: black or dark gray roofs are quite silly in a hot climate.
I have the same question, it would seem a quick win to have optimized house colors for the current temperatures. Many hot countries do it right, but especially northern architecture hasn’t adapted as well. Also, too much unshadowed windows. There’s a lot to win with well thought architecture.
For my house the problem is that the sun's energy is converted to radient heat which makes its way hours after the air has cooled. The HVAC people have said no amount of insulation or attic fans will help. They suggest radiant barrier roofing of varoius types. The simplest being reflective paint, which the HOA won't allow.
“Lennox International… developed the first prototype that achieved the Technology Challenge’s standards about a year ahead of schedule. The prototype delivers 100% heating at 5°F at double the efficiency, and 70% to 80% heating at -5°F and -10°F.”
The release goes on to say they expect commercialization and deployment in 2024.
Perhaps I missed it skimming the article, but my question is, double the efficiency compared to what? To the current state of the art cold climate hear pump? Or to a resistive heater?
COP of 2 at 5F is good. But... Mitsubishi has one that is 3.13 at 5F and LG has one at 2.65 at 5F, so this isn't really the breakthrough that the press release claims, the breakthrough is that a US company is doing it.
What they probably meant is that at 5°F the pump can supply 100% of the heat required to keep a house (of certain size) warm, with no other form of heating required. At -5 and -10, it can still extract enough heat from the outside to supply 70-80% of what's needed but you will need other means of heating such as resistive electric radiators to complement the heat pump.
Surely not engineering way of thinking but that's a common heat pump metric for ordinary people.
Efficiency is a misleading word for heating, because the units don't match; they are both energy, but different "type".
The denominator is fuel energy lost, but the numerator is thermal energy change within an area of interest.
A heat pump moves thermal energy from outside, changing unimportant thermal energy into good thermal energy.
This just seems like unnecessary hair splitting to me. Obviously the efficiency of something is subject to the important inputs and outputs involved.
If someone asks: "how efficient is this heat pump at heating my house?" And you start digressing about how that's the wrong question to ask you'll be giving them an impression opposite reality, which is for most people: it will use less electric energy than heat energy it puts into your house, almost all the time.
There are theoretical upper bounds on the COP though. As heat pumps get better, it may some day make sense to say things like "this heat pump is 95% efficient, so there is no point in replacing it".
No OP but yeah heat pumps are very efficient some >300% efficient since you're just "pumping heat" from one place to another not generating it.
Even electric heat alone is 100% efficient no incomplete combustion or degradation over time. Efficient bu much more expensive than just moving heat already in the air.
Ground-source are better for now since they are moving heat from a relatively consistent source the Earth. It's about 15C to 25C one meter down where the ground-source heat pump lines are run.
Generating vs moving heat I think is misunderstood by people or really more likely they just don't care. As long as the bill is low!
If you could really move heat 300% more efficiently than using a resistive heater to generate heat, couldn’t you just move a bunch of heat to power a steam turbine and get a perpetual motion machine?
It's not entirely clear what you mean. But, you say "if you could really ..." as if ground-source/air-source heat pumps don't do this exact thing; do you think they don't work?
Running a steam turbine by pushing water down a borehole to come into contact with a high-temp (>100°C) source has been done; it's not perpetual motion. Energy pumping the water is << energy output from the steam produced. It's solar energy that's being used, ultimately.
No, first of all perpetual motion machines don't exist, will never exist.
The 300% efficiency means if you had 1 Watt you could use it to power a fan and coolant lines to move heat. Or use 1 Watt to generate heat and then once made to move that heat.
The moving of heat already existing in the air (or in the ground) is more efficient than generating the heat and then moving it.
Slightly more precisely: you're using less energy (in the form of electricity used to run the heat pump) than you are moving into/out of the heated/cooled space.
Yeah take the energy you pump from Reservoir A to Reservoir B divided by the energy requires to do that and that's COP. Which you can think of as an efficiency.
I wish governments worldwide would boost this industry and get these heat pumps in the hands of people as fast as possible.
I live in the Netherlands that has one of the highest use of rooftop solar and generally energy conscious government and people. I bought a house recently and while doing some changes before moving in, my top priority was to get rid of Gas for heating and replace it with an all electric solution and supplement the power by as many solar panels as possible. As good as my intent is, I literally have €25K in the bank waiting to be spent for this, and the government gives a subsidy for essentially halving the cost of a heat pump, I could not get one until day mid next year!!! It is such a disappointment.
The intent is in the right place to encourage people to buy heat pumps, people are also willing. However, the chip shortage, and the insane labour crisis of qualified people who could install this is making the end result unattainable.
My wish is for the European Union to use any emergency powers it has to subsidise/mandate/beg the companies to mass manufacture heat pumps and solve the installation problem- train more people on this trade for free? Make it tax free to earn money by working as a heat pump installer? Anything…
Now, there is added incentive in the form of the need to get rid of Russian Gas. The time is now. Heat pumps already makes economic sense, it helps with climate goals, it boosts economy. I wish things happen sooner than later.
I'm actually surprised to see heat pumps gaining so little traction in Europe over time, perhaps excluding Baltics. I'm in Russia myself and I have a heat pump installed in my house for about a decade and a half already. In the long run, it was far cheaper than gas in my case. Not to mention it was faster to install; the gas pipeline bureaucracy alone would have taken several months.
That said, there are environmental concerns about geothermals at scale (see the earthquake in Landau). Not sure how much of it carries over to residential heat pumps, though.
The "In the long run" bit is the problem. Here in the UK people stay in a house for about 10 years before moving. It's impossible to get payback on many investments in that time, and when you sell your house the improvements aren't valued high enough to return the money you spent.
> I wish governments worldwide would boost this industry and get these heat pumps in the hands of people as fast as possible.
> …
> My wish is for the European Union to use any emergency powers it has to subsidise/mandate/beg the companies to mass manufacture heat pumps and solve the installation problem.
Can’t speak to other governments, but earlier this month the US invoked the Defense Production Act to do exactly this:
It's crazy to me that in the west; geo politics, national defense, people's budgets, and the economy are all in alignment, but no one in power seems to be capitalising on that.
Here in the UK we've had nothing like that and seem to be going the other way with things like fuel duty cuts.
Another issue here at least is that it seems financially better to pair standard heating with battery storage than invest in a heat pump.
Technology Connections on Youtube has a great video series on how heat pumps work, why they're important environmentally and what kind of power cost savings they can bring. The second video is a longer guide for people who want to get a heat pump.
Mitsubishi's products seem to be mini-split systems[1].
--> EDIT: Or maybe not... they seem to offer forced-air too. <--
The DOE challenge is for ducted systems. Their site[2] says:
> The Challenge is currently focused on residential, centrally ducted, electric-only HPs.
The DOE challenge also has other requirements[3] that I don't know if the Mitsubishi systems satisfy. It requires certain levels of efficiency and "grid interactivity" (meaning Energy Star "demand response"[4] where your utility can temporarily tweak your thermostat settings).
Many of the Mitsubishi heat pumps work with central ducted systems just fine. I have one (replaced a central gas heat, electric AC system).
It’s just a different air handler but the heat pump was the same as would have been used in a mini-split install.
When cross shopping the Mitsubishi vs Trane, the Mitsubishi was miles ahead. I didn’t even get the most cold weather efficient option (not needed for my climate).
I see a few in Portland and several in nearby zip codes. Hopefully one can work for you. There are different tiers of “diamond” so you can compare if the difference matters to you.
One thing that’s a bit different is the air handler and outside compressor run on one circuit (mine is a 3 ton unit). So there’s a power line between the 2 units. That threw off our city inspector. But it works out nice since I now have an extra 20A breaker free :)
Thanks! Do you have the technical docs with the efficiency curves for the Mitsubishi ducted systems? I can’t find the materials amongst all the marketing.
For reference, here’s what we have: 36KBTU AIRHANDLER/HEATPUMP HI-STATIC M SERIES DUCTED SYSTEM
INDOOR MOD# SVZ-KP36NA
OUTDOOR MOD# SUZ-KA36NA2
It’s a slightly older model as we had height restrictions to work around. This prevented us from getting a newer or hyper heat model. IIRC ours had good efficiency into the 20F range which was plenty for us.
In comparison, the Trane dropped efficiency at 50F and needed heat strips at that temp (so pretty crap).
I found it in their catalog. You’ll need your model or series. After all the specs there were some efficiency/temp tables. It was under Pros (vs homeowner) -> USA -> product support -> catalog -> m and p series.
I wonder why ducted systems were part of the requirements, is it because it's just aimed at the USA and then mostly at adoptability for existing systems (which seems to be ducted mostly)? I only have anecdotal experience and no numbers to back that up, but it's the only reason I can come up with that would put such a restriction in place.
I'd say rip the ducts out and just use split systems but I imagine other people have thought about that and figured it's not the best way to go. (or at last not in the US)
Yes, because nearly every house in cold climates is ducted, and we’re trying to get people off oil heating quickly, easily, and cheaply. Popping a new heat exchanger in an existing furnace is stupid simple compared to running coolant lines to new, wall-mounted exchangers all over the house.
I think that's true, if the ducts exist already that's simplest and cheapest. If they don't mini-split type systems are. But I suspect that long term those are going to be a pain in the butt because you have a lot of failure points.
Mini splits seem to be pretty reliable. They’re very common outside of North America. Most of the leading manufacturers seem to be from Japan (Mitsubishi, Fujitsu, Daikin)
> The prototype delivers 100% heating at 5°F at double the efficiency, and 70% to 80% heating at -5°F and -10°F. DOE’s Oak Ridge National Laboratory validated the performance and efficiency of Lennox’s prototype.
Usually when people talk about efficiency of heat pumps they are comparing to electrical resistance heating (which is 100% efficient). If that's what they mean then they are saying 200% efficient at 5℉, which is not as good as Mitsubishi, which is better than 200% at 0℉.
But in the first paragraph they say:
> The U.S. Department of Energy (DOE) today announced that American heat pump manufacturer Lennox International became the first partner in the U.S. Department of Energy’s (DOE’s) Residential Cold Climate Heat Pump Technology Challenge to develop a next-generation electric heat pump that can more effectively heat homes in northern climates relative to today’s models.
It could be that they are stating efficiency compared to current heat pumps, not compared to resistance heating, in which case they would be claiming quite a bit higher efficiency than Mitsubishi, which would certainly justify calling it a breakthrough.
Another possibility is that what they could be claiming as the breakthrough is the 100% heating at 5℉ part. The Mitsubishi cold weather heat pumps start losing capacity below 23℉, falling from 100% at 23℉ to 76% at -13℉.
I don't think that would be as big a breakthrough as double the efficiency of current heat pumps, because it wouldn't make it so heat pumps are feasible in climates too cold for Mitsubishi. But it would make it so that in places you can use a heat pump you might not need as big of a heat pump with the new technology as you would need with a Mitsubishi. That could lower up front cost making converting from something else to a heat pump more feasible for many.
We recently converted our house to 100% heat pumps. The models we have are efficient down to like 0F and continue to work down to -15F (lower than the record low here). So this tech is novel but already consumer available. We have Fujitsu Halcyon XLTH models and commercial units that are less common for residential.
They all “continue to work” at cold temperatures but the question is with what and how much you’re going to supplement their insufficient heat with when it gets that low.
COP is still decent at low temps. That is the point. They are 80% efficient at their lowest temp rating. And, at least where we live 99.9% of days will be 100% efficient.
I guess 80% efficiency for a few days a year is OK. In The Midwest we can go below zero Fahrenheit for a month or more at a time and while I happily live with 80-90% furnace efficiency with natural gas as a fuel, I certainly would never want to do that with electricity as a power source (given the historic price difference between the two).
You need a separate hot water tank and a 3-way valve, when hot water is requested the hot water from heat-pump will get diverted into the hot water tank (puffer).
No idea how the Lennox units in TFA do it, but the Mitsubishi "hyper-heat" units do it by diverting a small amount of their output back into heating up the refrigerant at very cold temperatures. It starts to get a bit "slushy" at the low end of the performance range, which impacts the ability to move heat. By warming it back up to the bottom of its ideal operating range, the whole system functions more efficiently.
It can operate efficiently at lower temps. Current air source heat pumps see degraded performance and below freezing temps and will not be able to effectively heat a home at the lowest temps that can occur in the northern hemisphere.
The "secret sauce" of the increased efficiency is that they're using thermoacoustics, which previously had been a technology used in one-off applications with a large budget (e.g. the James Webb telescope uses it to stay cool). Prior to now there were no manufacturers providing the technology to be widely available at scale.
That's great news. I have a heat pump in my house, but still need to use the gas furnace when the temp drops below 40 degrees Fahrenheit.
A repair person goofed the settings last January, and I didn't notice the furnace wasn't kicking in until the end of February. My electric bill went from $150-ish for Feb 2021 to $450-ish for Feb 2022.
It’s not about ‘working’, it’s about the cost of electricity when it gets colder and the efficiency drops. Gas is pretty cheap for heating in most of the US…
Lab vs typical observed performance differs quite widely for many home heating systems.
Thats because typically each appliance is tested at optimal conditions (eg. water flow rates). Then, in a real deployment, every parameter differs a little from optimal (eg. the water may circulate slower than expected because you have longer pipes around your home than the lab ones, and your hot water tank is hotter than expected because you like it set hot, and your airflow is less than expected because the filter is a bit blocked, etc.). Each knocks a few percentage points off the efficiency, but the overall impact can be dramatic.
We really need 'smarter' heating systems which can detect and correct for such things. For example, water and air pumps which measure temperatures and flow rates of air/water, and adjust speeds up and down to maintain the optimal efficiency point.
“Tapping into the emerging clean energy market is a huge economic opportunity that will bring a bolstered manufacturing sector, good paying jobs, and a brighter, cleaner future to Texas and communities across America.”
If anyone else is confused by this, it's because Lennox is headquartered in Texas.
what's not straight forward is understanding why the statement lists a single state and everyone else falls under 'communities across America' which the comment above clears up.
I wonder if the ideas used here can make low temperature geothermal systems more efficient. An example is the 760 kW system at Chena Hot Springs, 50 miles east of Fairbanks, Alaska. The system there uses hot water from said springs to generate power using repurposed refrigeration technology.
Chena Hot Springs geothermal is a heat pump. It's an absorption chiller used partially (primarily?) to keep an ice house chilled as a tourist attraction. It works for such relatively low geothermal temperatures because the average Carnot Delta T is pretty good (because Alaska).
As to whether or not thermo-acoustic technology could work, that's a good question.
Ah, I see. I figured they'd keep the input energy constant because otherwise you're not saying much at all (you could figure that the efficiency plummets and you'd be better off with a space heater).
The energy input goes down because it physically can't run a differential high enough to get full heating output.
They could choose the lowest temperature, find it's power input, then fix it at that amount. But at low temperatures the concern is usually less "efficiency" and more "am I going to freeze to death", because in most of the cold areas temperatures aren't usually that cold for that long (though in others it definitely is, and if you're running at 1.6 COP for a significant amount of time, you're better off with more insulation than a heat pump).
It's possible. Also possible it's barely outperforming the space heater at the lower temperature and input power has increased. They've not told us enough.
It says "double" the efficiency, so I assume they mean 2x the COP of the previous model at 5F, and 1.7-1.8x the old COP at -5 and -10F.
A COP of 2 @ 5F isn't a "breakthrough" vs. the first commercially available model I could find numbers for, and a COP of 1.5 at -10F seems implausible:
Interesting to see heat pumps come up more and more these days. As a lot of comments here point out, heat pump technology is already pretty good, even in cold climates.
It seems to me a lot of the barriers to adoption in the US are lack of awareness from consumers and widespread support from installers. The equipment for a heat pump shouldn’t be much more expensive then an air conditioner since they share so many parts, but that isn’t the case in practice.
I think government regulations that encourage heat pumps manufacturing and installation are part of the solution. For examples, Biden administration recently issued orders to use the Defense Production Act to produce heat pumps [0] or NYC banning new natural gas hook ups for heating [1].
The other part of heat pumps adoption is making them exciting for consumers. It feels like if you get the right combo of all of that, heat pumps could be the next electric vehicle.
I only recently learned about heat pumps and found it difficult to understand how they worked and potential benefits. Towards that end, I started hacking on this tool for others to get that info: https://www.heatpumpswork.com
Once again the headline does not match the claim in the article. This is not a breakthrough in terms of technology. This is the announcement of a partnership. There was no "breakthrough". This is government advertising for a private sector company that frankly is beginning to resemble corporate fascism.
You probably should not wait: it will be 2 years of testing according to the announcement, and if you’re doing a retrofit most the cost of installation will be installing the transfer lines inside, mounting the unit, etc (opening walls and closing them back up). Transferring from an old outdoor unit to a new one should be a fraction of the original install cost (basically just the new unit cost plus the cost of hooking it up).
But, if you’re willing to wait or pay extra for the efficiency gains, you might be even better off getting set up with a ground source heat pump now. The install cost is more up front, but because ground temperature is higher than air temperature in winter and lower than air temperature in summer, the differential you need to pump in or out is a lot less, and therefore much more efficient. I don’t think any air to air heat pump in the next 20 years will be as efficient as a ground to air system you could install now. The air to air systems just have lower up front install costs.
In the US, there is still a 30% federal tax credit for ground source heat pumps as well. Many of the other energy credits have sunset (such as solar, I think)
I just bought a Mitsubishi mini split system to replace our oil furnace and bring A/C to our house here in New Jersey for the first time. Their high end outdoor units heat down to -13 F, which is colder than I've ever seen here. It arrives in august.
Gree has a system that claims to have full heat down to -31, so I'd say just keep researching and you'll probably be fine.
What is the plan for when it gets colder than -13? Do you do a hybrid with your furnace? Some other solution? Thinking of getting some heat pumps myself.
I’ve looked into heat pumps pretty extensively for my upcoming boiler replacement (looking at an air-to-water in my case, but very similar principles apply).
In my case, the 99% design temperature is high single digits Fahrenheit. For the 3.5 days/year colder than that, the plan is to have the house “coast” on thermal mass.
That’s for cases where the ambient temp is below design (where the heater can make heat but just no longer enough to keep up with the building heat loss), not for when it’s below a cutoff (where the heater shuts off entirely). In my case, that’s so far below design temp that I’d expect to never see it. (We hit -9°F in 2016 and would have to go all the way back to 1943 to find a low of -14°F.) If it happened, thermal mass would start to carry us with electric space heating keeping the house from totally freezing.
I might invest in some backup propane heaters as well (a buddy heater at Walmart is pretty affordable and is safe for indoor use). I feel like in blizzard-like conditions having electricity be your backup plan might not be too wise.
In nearby Philadelphia, it rarely gets that cold, and not for extended periods of time, but when it does, we bust out blankets and space heaters to make up the difference.
We usually switch to the wood stoves once winter sets in. Our forced air furnace is incapable of making the house warm and cozy because duct reasons that I can't really fix.
I'm planning on getting rid of it altogether and doing the heat pump(s) most of the year, the wood stoves in winter and reclaiming a lot of headroom in the basement and an entire utility room that the furnace currently takes up.
They way it works in practice is that the air handler that comes with the heat pump will contain a backup emergency heat element in case it gets too cold or there is a problem with the heat pump. The cost to run it is much higher, but it should only run in the most extreme cold temperatures.
FTA, they already measured it and will deploy in 2024:
> The prototype delivers 100% heating at 5°F at double the efficiency, and 70% to 80% heating at -5°F and -10°F. DOE’s Oak Ridge National Laboratory validated the performance and efficiency of Lennox’s prototype.
> Lennox is one of nine manufacturers competing in the CCHP Technology Challenge. Its product and others that meet the CCHP Technology Challenge will undergo trials in cold climate regions over the next two years to demonstrate performance, efficiency, and comfort when applied in the field throughout a winter. Deployment and commercialization are planned for 2024.
One tip from my install, is to go with single zone units. I did a multi-zone and the way the control system works is kind of weird. They also don't have as good of a turndown ratio[0] as smaller/single zone systems, making it less efficient.
One thing I do t see many mentioning is the low temp heat pumps currently available are pretty expensive last I checked (think $15k), that’s simply not feasible for most people. We need something in the 4-8k range so the average joe can justify it. Perhaps this new set will be cheaper.
I just got a quote: $30K to upgrade a 1000 sq ft. apartment from oil fired steam (59% efficiency boiler from the 40s) and hot water to heat pumps near Boston. Includes removing oil tank, radiators and installing resistance electric hot water heater.
Or I could upgrade from oil to gas for $14K (to an 82% efficiency boiler). I have a strong incentive to do this since the cost of heating with gas will be 1/3.5 compared with heating with oil.
I think these are insane prices, but that's what contractors get around here. There is a $10K incentive for the heat pumps, but it requires a home inspection and probable upgrade of the insulation. IMHO, the incentive is not enough- it needs to make the heat pumps the cheapest option.
As far as fuel costs, the gas would definitely be cheaper. The electricity comes from gas (especially in the middle of the winter). The price is more because you are paying someone to convert the gas to electricity. The efficiency of getting the heat from gas via electricity is only a little more with heat pumps (when accounting for generation and transmission loss and much higher heat pump efficiency).
Maybe in the future the electric supply will be greener, but it isn't today. They are trying to build a HVDC line from Boston to Quebec for more hydropower, but Maine and NH are not allowing it due to NIMBY (a referendum in Maine, financed by gas companies, killed it).
When I read the title, I wonder why air to water and air to ground heat pumps aren't more common in cold climates. Where it is 0°f on the surface, a few feet deep and you're back to 46°f.
So we could have had efficiency 10 years ago instead of today?
Ground source heat pumps are 2-3x the cost of air source, and require a decent sized piece of land for installing the ground loop. Vertical installations use less surface area but are even more expensive since you’re drilling holes 400’ deep for the loop.
Water source heat pumps are easier installations but require houses sited near a specific type of fresh water source that does not fully ice over in the winter or dry up in the summer.
Any studies in what these things do to the frostline?
Heat pump is better than burning fossil fuels, but we also stop needing to treat system after system like it’s a bottomless well. We did that with real wells, then rivers, then the sky, then the ocean, then carbon dioxide and next up will be ground heat.
There was a house last year that I think people were complaining about on Reddit, giant house out I’m the woods, all glass walls and heat pumps, labeled as green. It’s not a green building if you are 2x as efficient as fossil fuels but your house needs four times the BTUs of a reasonable design and 6 times a green one.
Twice as efficient and half the heat loss is green. Blowing the surplus is not.
Ground source heat pumps have become popular in the past 10-20 years. Natural gas has historically been cheap enough that replacing it may not be cost-effective if your house is connected to a gas grid. When replacing other heating sources, a ground source heat pump typically pays itself back in 5-10 years.
Based on a quick search, the typical costs for installing a vertical system to a single-family home are 15k to 25k euros in Finland. The contractors I found seem to discourage horizontal installations unless the bedrock is unusually deep. Drilling bedrock is cheap, while horizontal pipes have to be much longer, because the ground gets cold in the winter.
Odd, here drilling far eclipses excavation costs. Horizontal systems just need a backhoe to install, as you only need to dig below the frost line (we also get down to about -40 in winter). Vertical drilling requires more specialized equipment and so is more costly. Vertical systems are about $10k more expensive than higher end horizontal systems.
"can save families as much as $500 a year on their utility bills".... ehhh, people affected by an extra 500 per year arent going to fork over 20k for a new system that will save only 500 per year.
Overall the cost may not be that much but the bigger shift is to electrification of heating instead of a gas burning boiler, as electrical systems can take advantage of power from offshore wind / solar etc. another way of looking at it is most people will replace their boilers in the next 20-30yrs, if they can get a electrical heat pump system they should (and the governments should make this economically advantageous to do so).
> Cold climate heat pumps (CCHPs) can provide high-efficiency heating in freezing temperatures without producing greenhouse gas emissions and can save families as much as $500 a year on their utility bills.
That's like one month of heat for free. A welcome respite, but hardly revolutionary. Slashing emissions is awesome though.
Can you use the same tech to cool a house? That would seem to be much more needed given the climate trends (warming) and demographic trends (moving to Southern US States).
Yes; many EVs already use heat pumps, so if this has a higher coefficient of power (and is not much heavier), and it can be scaled down to automobiles, then it will be a win.
(None of those details can be inferred from the press release.)
So 10k+ outlay to save under $500/year. That would take only 20+ years to pay off. The wall units are kind of flimsy. Expect at least one to break. And that $500 in savings is probably $300/year in reality. Its still a great option for some places, just not really to switch over from a gas furnace.
Seems more reasonable to compare the typical initial cost vs the increased initial cost for the higher efficiency unit that saves $500/yr.
My house was built in 2000 with a regular AC unit for the main floor and heat pump for the 2nd floor, both Payne, a builder grade of Carrier. The inside coil went first, at the 9-yr mark with a 10-yr warranty, so I did get a new coil at no expense but it cost $600 to install it.
A couple years later, the outside heat pump went out, and because of the system's age (about 11 years), they recommended replacing the furnace and heat pump.
A couple year later, the main floor furnace exhaust gas blower mechanism went out, and again, the outside unit was replaced because it was 14 years old.
In contrast, my previous house had an American Standard AC and furnace that was installed in 1970 when the house was built. I had to replace the furnace blower motor one year - about $500 I think - but the original AC and furnace were working like a champ when I sold the house in 2003.
In summary, you aren't getting 20 years out of any modern, shitty system anymore. They're designed to fail after 10 years. You might get lucky and have something fail after 9 years; then you'll only have to pay for labor. But because there are 2 major independent components, the outside compressor and inside furnace, it's unlikely they'll both fail within the warranty.
My AC guy told me the main reason they fail is because the new coils are made of very thin aluminum and so fail sooner than the old systems. If a coil fails, either in the furnace or the outside condenser, you're screwed. They can sometimes fix them, but good luck with that. Most HVAC dealers don't want to bother doing that; they just want to sell a new system.
Which is always the problem when you ignore the negative externalities. One would hope those externalities might start to be internalised to the cost of burning fossil fuels for heat, then heat pumps might become a better prospect.
(Tbh, I recently did a high level analysis of a heat pump in a temperate climate, and in light of climbing fuel bills and the potential for low price electricity from renewables at low demand plus batteries, heat pumps start to make a lot of sense. You need to think about using them differently to gas though)
I think it also ignores the fact that one of the big energy suppliers entered a war of territorial expansion and it may take a while until it's business as usual - I'd expect this to also affect energy prices.
Does anyone know why there has never been any breakthroughs in air conditioning for 50 years? Windows air conditioners have been incredibly heavy, loud, expensive, and resource-intensive for so long. Even a small room needs one that is back-breaking to install. And pretty much everyone in the world (except those with central air) needs a couple of air conditioners now.
Sure the "efficiency" is improving but it's mainly tricks for turning it on/off at better times. I know there are some U-shaped ones now, but it's just a slightly different styling.
Edit: two commenters pointed out examples of air conditioners which are 77 lbs and 56 lbs. As a comparison, the OSHA recommended lifting weight is 50 lbs. I would love to see someone apply Apple's obsession with thinner, lighter, "revolutionary new design" to ACs.
Check out the inverter type ones such as this one [1] It isn't light but it is quiet and adjusts the amount of power it uses depending on cooling needs much better than a typical window unit making it more efficient.
The Midea U window AC units are a really good product. I am easily cooling a roughy 1,200 square feet space with only one of the 12k BTU units and a few ceiling fans, and it typically gets into the 90’s F here in the summer with significant humidity.
No affiliation to Midea just a satisfied customer.
I agree. The U shape is a gimmick, but a good one. It helps it be quieter inside, but even outside they are quite quiet. I have whole house AC, but I like the windows open, I like being hot. Just not when I’m sleeping. Basically only downside is a truly terrible app that is the only way to access just a few features.
Terrible doesn't begin to describe that app. Honestly what does the turbo button in the app even do?
I have one in a room on the far end of the house that the main AC can't reach, it helps reduce power usage since I can keep the rest of the house warmer.
Window units really only exist at all because of buildings that can't accommodate better designs for either practical or legal reasons. There's just no amount of innovation that can make it so that having the intake and the outtake right next to each other without a nearly perfectly sealed box on one side (ie. a fridge or a freezer) is gonna be anything but a big ugly noisy energy gobbler.
If you can't have central, you should have mini-split, and that's where all your problems get solved. If you can't get mini-split because your landlord won't let you drill conduit to outside then you're just kinda stuck and the laws of thermodynamics are your enemy, not a lack of innovation.
Idk this "toshiba" AC has a built in heat pump and operates at super quiet levels.
Would I call it a "breakthrough", likely not. But it is a meaningful improvement over an AC released decades ago.
Mini splits are widely used and have become dramatically more economical and popular over the last decade or so. They are much quieter and more efficient than window units.
Some areas (cough nyc cough) may need some regulatory breakthroughs but the technology is there.
"Lisa, in this house we obey the laws of thermodynamics!"
It's physics and thermodynamics. It's basically the same as with any heat engine, internal combustion engines included.
There is a certain maximum theoretical efficiency that is not 100%. When we build real machines (not theoretical ones) there are real world losses like heat loss, fluid flow friction, moving part friction, electrical inefficiencies, etc. Those real world losses van be gradually worked on over time, improved incrementally to yield small gains in efficiency. But never large ones, and never more than the theoretical max efficiency, which is not 100%.
It's like hybrid cars (not plug in hybrids, but just gas powered hybrids), they've doubled or trippled the mileage compared to a comparable regular car, but they will always need gas, they will never be 100% efficient.
Same with this. There will always be some fundamental electrical losses in the copper in the motor, air gap losses in the motor, friction in the bearings and fluid, heat losses to the environment, etc. It's the cost of doing the work. There is no free lunch, so we can only incrementally improve the little losses over time.
My understanding is that heat pumps can be over 100% efficient because they're actually moving heat from A to B where one side is the outside environment. It doesn't violate thermodynamics if you view the Earth as a closed system. The heat pump itself is not a closed system.
Thanks for highlighting this because it's a common misconception.
"The coefficient of performance or COP (sometimes CP or CoP) of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work (energy) required.[1][2] Higher COPs equate to higher efficiency, lower energy (power) consumption and thus lower operating costs. The COP usually exceeds 1, especially in heat pumps, because, instead of just converting work to heat (which, if 100% efficient, would be a COP of 1), it pumps additional heat from a heat source to where the heat is required. Most air conditioners have a COP of 2.3 to 3.5. Less work is required to move heat than for conversion into heat, and because of this, heat pumps, air conditioners and refrigeration systems can have a coefficient of performance greater than one. However, this does not mean that they are more than 100% efficient, in other words, no heat engine can have a thermal efficiency of 100% or greater. For complete systems, COP calculations should include energy consumption of all power consuming auxiliaries. The COP is highly dependent on operating conditions, especially absolute temperature and relative temperature between sink and system, and is often graphed or averaged against expected conditions."
In short, a heat pump is more efficient when compared to using the energy to directly generate heat because it's more efficient to move heat than generate it.
That means you need somewhere to move the heat to, and the thermoynamics of heat capacity are not forgiving if you are trying to make something lightweight. You need atoms and lots of entropic states to store heat :)
Thermodynamics are harsh mistress... Add that to limitations on what can be used as refrigerants. The reality that these systems need to operate with rather long duty cycles for decade+ at minimum. And the reality is that there isn't much magic in how they operate. Compression and expansion of gas.
Computers are actually a very special case. They don't really do any physical work in sense other stuff does, thus miniaturization gives lot of gains there. I have long said that small drones are answer to flying cars. We have them and they are small, but lifting people is hard work.
AFAIK the physics of heat pumps is considered to have been fully figured out for ages and all that's left is the engineering. Maybe it wasn't considered a "sexy" enough topic to nerd out over and hyper-optimize?
Edit: it might also be an issue of diminishing returns of better efficiency compared to how difficult it is to produce and maintain a better unit. Thermodynamics can be a pain like that.
Patents, intellectual property, etc. It's why every appliance is trash nowadays. Big corps are IP holders, and there's only so many ways to engineer certain actions. Regardless even if you try to startup a company you'll be pushed out by the control big corps have over manufacturing.
We need to start nullifying IP if we ever hope to see innovation.
Probably not this, most IP can be worked around, and especially in the area of AC operations and thermodynamics, that hasn’t changed in almost a century.
We got a U-shaped one for a big open attic space and I'm a fan of it. It cost more and was a little bit more drama to install (came with a big support bracket thing), but it's very effective and quiet. We meant it as a stepping stone to eventually putting a mini-split setup on that side of the house, but it might end up just being the long-term solution.
EDIT: Oh lol, the unit we got was actually one of those Midea ones linked in a sibling comment.
As I mentioned elsewhere: https://news.ycombinator.com/item?id=31791936
there is a company that claims to use thermoacoustics for general heat-pump duty. I believe they are targeting European style hydronic heating. Aiming to be efficient whilst still producing the 80c water that many older hydronic systems here in Europe still require.
Interestingly, they aren't that loud because any sound lost is energy lost, so they try very hard to 'keep it quiet'.
Talk about moving the goalposts. You asked, people answered. The revolution is that you can now buy an 8000 BTU unit that weighs little, costs almost nothing, and can be installed anywhere in a few minutes.
> And pretty much everyone in the world (except those with central air) needs a couple of air conditioners now.
Absolutely not. Where I live we had 34°Ctoday but I would still never buy an A/C unit, which will ruin your health (heat/cold shock, bad air moisture levels, ...), waste immense amounts of energy and makes leaving the house a pain as the rest of the world becomes uncomfortable. Most of my friends here earn very well but I can't think of anyone that would see a reason to buy one. Live with the temperature and adjust - like the famous Iberian or Mexican siesta, where you simply accept that midday are low energy hours.
But even beyond this, the reason for A/C use is just bad architecture and city design. More trees in the streets can lower the temperature in the street itself and nearby residences easily by 1-2 degree. Less absorbing surfaces (asphalt, stone sidewalks, ...) make another difference.
And as regards the houses, there are plenty of ways for passive and energy efficient buildings that keep cool. In the middle east they have built self-cooling houses for centuries.
And in all this, even if you are stuck with bad streets and architecture, you can simply adapt, use efficient ways to keep cool (a fan can work wonders) and drink warm rather than iced drinks and your circulatory system will thank you as you don't switch regularly get shocked with 10-15° differences and you will sweat much less.
I'd been using a window unit for the bedroom but got sick of taking it in an out and decided to see how long I could manage without it. Now I prefer no air conditioning because of the reasons you state above - it feels much more comfortable being outside on hot days. I keep the windows and doors closed during the heat of the day then open them up when it's cooler outside than it is inside.
Let me guess, where you leave there are "serious" blinds outside the windows that help keeping sunshine out. I wonder when Central Europe will start installing them.
It doesn't really compare since ground-source/geothermal systems are designed to work with a smaller temperature difference (since the earth stays about 50F most of the year a few feet down).
Business wise, if this really works at 2COP at 5F, this might take over most of the market served by ground source heat pumps though.
I don’t believe in breakthroughs anymore until I see a shipping product. I don’t care if you are a scientist, company, government agency, or NGO same thing applies.
Tell me you’ve made an incremental improvement and I’ll believe you, tell me you’ve made a breakthrough and either you’re lying or something will prevent it from being realized before commercial availability. This is what decades of press releases and articles that might as well be press releases have taught me.
But there exist sooo many prototyping breaktroughs.
Those who follow press releases for many years know that just a tiny fraction can transfer this in real world products that actually work
(so many more challenges to overcome compared to prototype situations!! I don’t even know where to begin… every ground is different, average person doing the manual work is not as skilled and has less support engineers, the guys setting/defining the dimensions of various recipients/pumps/conduits are often undeskilled and the efficiency often lacks tremendously for that reason…)
My thinking on it is: It'd better work, they're just trying to catch up to the state of the art. The bigger news would be if Lennox CAN'T make a COP 2 at 5F heat pump. :-
I agree with the general sentiment, but the article explains that this "breakthrough" is a product prototype that meets a government spec. It's hyperbolic wording, but they're trying to warm people up to the idea of eventually getting a heat pump to alleviate some energy issues.
The “save up to $500” in the presser is just so obviously fluff. $500 in what home?
And I suspect the magic here is also an air tight new construction home with a layout designed around this, not leaky everything with an old water heater tucked under the stairs, a 30 year old furnace, and R19 insulated walls.
Presumably the 30 year old furnace is replaced or supplemented with a new heat pump.
I have realized an approximately $500 yearly savings by replacing an older electric tank water heater with a hybrid electric (heat pump) water heater so I can believe that claim.
I recently installed a (quite large) heat pump for less than that, though it came close. A lot of the cost came from a few things:
- the Canada premium: these sorts of things are just more expensive here. The base price was just higher than I could find in the US, but obviously importing is too expensive. I think the reason for this is there's almost no stock.
- adapting my house: the house I live in was built to have central air added to it, but even so the pipes going from the furnace room to the outside had to be insulated both directions instead of only one for an AC. Ripping up our basement ceiling to do this added a lot to the cost. An unfinished basement would help a lot here.
- HVAC company confusion: I had to go through like five HVAC companies before I found one that would believe me that I really wanted it. The one I got is a commercial outfit, so their prices were just higher. Even they were skeptical but they were willing to work with us, and by the end they talked about doing more installs so that was nice.
I think the cost for the install and unit itself was $12k for a top of line carrier unit capable of working down to pretty low temperatures. But we already had a compatible carrier furnace and exchanger. Was another couple thousand for ripping up the basement, which we had other contractors do.
This was also literally during the heat dome last year. They had to ship the unit across the country.
All the quotes I got were for a day of install. I assume it'd be one tech, but let's be generous... 2 techs x 8 hours x $150/hour = $2400 for labour. So that means either the pump itself costs $15k, or somethings wrong in this market.
Or my alternate hot-take (or cold-take?): Great, now if someone can crack the engineering challenge of an air-to-water heat pump water heater that doesn't turn your basement into a walk-in refrigerator, that'd be great.
Depending on your market, Sanden and Mitsubishi make air-source DHW heat pumps where the evaporator/heat source source is remote (i.e., outdoor) rather than integrated with the tank. I can't speak to Mitsubishi's line but IIRC Sanden has the DHW go straight to the outdoor unit, but then you may need freeze protection, which I think Sanden provides via heat trace. When my current water heater bites the dust, I plan on getting a Sanden, and looking in to the feasibility of making a glycol loop between the outdoor unit and an indoor "indirect" tank to eliminate the need for freeze protection.
Thanks for the tip! Where I am Mitsubishis seem to only be available through big-name installers, and the only thing they offered me when I talked to them was the all-in-one style that cools your basement. Living in an old house with not great insulation between floors, that was a hard no-go. I'm now googling the Sanden ones and getting some promising results I hadn't seen before.
What you want is an "Ecocute". It is a air source heatoump supercritical co2 tanked hot water system. Designed for the Japanese market. Without install a 500l tank version costs about 1.5k usd in Japan. So you should be able to get one installed for about 20k usd in the US. If you beg the HVAC guy of course.
The all-in-one heat pump hot water heater pulls in warm air from its surroundings, pulls the heat out of it and puts that into its water. Then it lets out its "exhaust" colder air. Ducting to outdoors improves things, because it doesn't put that cold air back into your basement / utility closet, but you're still pulling heat out of the air - which your house heater now has to put back into the air - and unless your space is perfectly airtight, that's probably just going to be sucked in via the nearest air gap to outside.
It's a bad system. Split systems make sense, and I know they exist, but they seem weirdly rare.
The ducting brings the temperature drop to an almost unnoticeable delta. If you are worried, just install it near your furnace. It’ll eat radiant heat from that corner that would otherwise go into the walls, egress windows etc. Every other part of the year, you either don’t mind or benefit from the cooling.
I have the stats from my own Rheem to know I’m coming out ahead financially during winter and also haven’t seen a meaningful swing in the basement climate.
I’m a regular participant in that linked blog, too. :)
You can definitely do it for cheaper. There are $1000-$3000 single-head units available online for self-install, and you could hire an HVAC person to come out and do the high pressure line part of it (or all of it) for a similar range. It just gets expensive with the name-brand ones. For some reason that $2k-6k turns into 10k-20k when you switch to a name brand (e.g. mitsubishi). They're only available through specific installers, and using a non-authorized installer means your warranty is void.
This makes me idly wonder if we could use those rays of golden sun for heating more efficiently than we are. Pitch black panels facing the sun through which you pump some heat-transfer fluid? Hooked up to a heatpump?
But it delivers 100% words at 5°F at double the efficiency, and 70% to 80% words at -5°F and -10°F. DOE validated the performance and efficiency of the press release.
Spray foam is expensive. It’s considerably cheaper to install mineral wool or blown cellulose or fiberglass. And you can blow in insulation without removing the drywall.
> How does one blow in insulation without removing drywall?
We got blown insulation in the floors (ie between roof and floor), he drilled a 2 inch hole every two feet or so. We added our parquet floor right on top, with just some thin XPS sheets inbetween for noise.
Not sure about drywall, but I'd imagine it's similar. Easiest would be to just put some 6mm plasterboards on top to cover the holes, saves you handling each one individually.
You drill smallish holes in the drywall in each stud bay, blow the insulation in through the holes, and patch them. This is much less expensive and less messy than removing and replacing drywall. It can be done with cellulose insulation, with fiberglass (the loose fluffy kind, not batts), and possibly some other products.
Spray foam is expensive, but it pays for itself pretty easily. You can diy drywall hanging simply enough so you’re really just paying for the foam and someone to plaster, you can paint yourself.
A cheaper option is rigid foam with canned spray foam around the perimeter.
You really don’t. I’ve been in a house in Maine with spray foam in 20 degrees with no heat turned on and interior temp was around 65. It was pretty amazing actually.
A heat pump isn’t cost effective compared to Reno with spray foam. An average heat pump probably takes a decade minimum to pay off.
So much air in this statement, but almost zero raw numbers.
In the mean time, there are good quality air/water heat pumps on the market in Europe. Look at the Nibe F2120 for example. It blows this thing out of the water. It has a COP of 2.5 at -25C...
At some point, it would be great to use a natural gas powered engine to run a heat pump. You could then use the exhaust gas as a heat source for the heat pump, possibly eliminating the need for a pre-heater.
Cooling the output should increase the Carnot efficiency of the motor.
Heating the outside air intake with that heat should be sufficient to avoid the need for an electrical resistance pre-heater.
This combination could also run on propane, ethanol, gasified wood, etc. Anything that gets burned now could be used to create far more heat output than straight up combustion.
There's got to be a flaw in this idea, math/physics wise.
Why would you create new technology with natural gas these days. It seems such an energy source of the past. Europe is jus suffering from the dependency on it and seeks to get away from it as soon as possible.
Agreed. Just electrify everything in the home, then while we still have natural gas then just use it for electricity generation. Natural gas's only benefit is that it is currently cheap, when that stops being true, then it is just worse than electricity across the board.
The great thing about electricity is that it scales REALLY well with new generation and distribution technologies.
So, you burn natural gas in a powerplant to create electricity somewhere around 55% (hopefully) efficiency; in most of the US, the heat output is wasted. You then lose 6% to transmission, getting to 52% efficiency, to put it into a 2x COP heat pump (which we mandate use gases with GWP in the thousands) to get 104% of natural gas heating.
Or, spend the same amount on air sealing reducing heating needs by about 30%, pay workers instead of factories, and get the same reduction in natural gas use, also without the refrigerant bomb waiting to go off, and not needing more power plants built. Mandate every rental have lower than 6 ACH50, since misaligned incentives mean they're usually worse than homeowner-occupied units.
Efficiency percentages are the wrong way to look at it. If you instead frame it in terms of tons CO2 equivalent, then locking in the emissions every year between now and 2050 is going to be worse, compared to the alternative of burning a bunch of natural gas for electricity now but gradually phasing it out in favor of wind and solar.
Europe is resource poor and suffering from a dependency on Russia.
55 billion cubic meters annually were set to be added to this dependency as recently as February 21st of this year before yet another land war erupted on the continent, forcing them to suspend certification.
The flaw is that we need to stop using fossil fuels now in order to meet Paris targets.
Natural gas in particular is an issue because demand is increasing globally whilst large suppliers i.e. Russia, Australia for many reasons are not able to meet it. Which is pushing up prices and increasing unreliability over the short, medium and long term.
Now is the best time to bite the bullet and transition to a decarbonised world.
Apparently, all of us in the northern part of the US are supposed to build new houses that are super-insulated and run on renewable electricity. Which is a nice goal, but in the here and now, we've got a grid that couldn't possibly handle everyone going fully electric, and it's not reliable because most of it's above ground, where it'll stop working when we need it the most. (In the winter, when it gets icy, and power goes out)
All I'm suggesting is that we take an existing natural gas furnace out of service, and replace it with something that uses FAR LESS natural gas, with the same heat output to the home. It's not perfect, it it's better than what's there, and fits within the infrastructure in place.
Environmental impact or geopolitics issues aside, an electricity grid is much more convenient and cheaper than a propane/ethanol/gasified wood grid. Transporting gaz by trucks and storing it in individual houses is not very convenient too.
I think you’re basically describing a steam engine that mechanically powers a heat pump, pumping it’s own waste heat and whatever environmental heat it needs.
It’s pretty complicated. Direct hearing via heat exchanger is usually pretty good and much simpler, albeit less efficient. If burning thermal sources, raw efficiency is rarely all that necessary though. The heat output per unit mass is usually pretty high.
The claims are pretty amazing. High efficiency, efficient over a wide range of temperature difference, high temperature differences possible.
The operating principle is totally different. It is based on acoustic waves. Not using phase-changes but just the ideal gas law (pressure and temperature are proportional). I tried to get my head around it, and I got it with a standing sound wave. But they use a traveling wave, for which I could not find explanations I understood.
The general idea is "lower air pressure and move gas to cold side so the gas heats up" followed by "raise air pressure and move gas to warm side so the gas cools down". That means the low pressure needs to be low enough that the gas gets colder than the cold side, and the high pressure needs to be high enough that the gas gets hotter than the hot side. Luckily that is 'just' a matter of amplitude of the sound wave. I think this is how they achieve their wide range of efficient temperature deltas.
That wide range is the main difference with a phase-change based unit. The phase change happens at a much more difficult to change temperature.