I'd say its quite inaccurate to say that Stirling engines will get you 'off the grid'. You are exchanging one grid, electricity generation and distribution, for another, natural gas production and distribution. Your engine may be physically connected to a residential gas distribution network, or practically connected to the gas industry 'grid' if you are expecting large gas bottles to be trucked to your door every few weeks...
To me the cool thing about a Stirling engine in the abstract is that it doesn't have to run on natural gas, it can run on anything combustible. They allude to that later on in the article, but it seems like maybe we're not getting the super-flexible versions in the US. If they were selling that, I would definitely consider getting one for my house (when I have a house)
That actually confused me. I understand how they can run off of any heat source, but then why is it touted in this article as a heat source? It mentioned that it might be a good idea for a laundry that needs a lot of hot water. But if that's the case, don't you just need an efficient furnace to heat the water regardless? Or is it that this thing can recapture a lot of the energy you're already expending heating up the water by some other means?
AFAIK, a Stirling engine is basically a heat pump, it mopved heat from the heat source to some heatsink using the expansion and ocntraction of air. If you were to run water over the heatsink, you'd probably both heat the water and increase the efficiency of the machine by giving a greater heat differential and greater heat conduction rate. S you could use the heat twice basically; one to move the engine's piston and a second time to heat water.
stirling engines are also known as hot air engines. there are different models and systems but i have one that already works with the temperature difference between room temperature and my hand temperature. Awesome. There is a german manufacturer under www.boehm-stirling.com that makes really nice stirling motors in different forms like cars, machines and so on.
Any (significant) temperature delta is fine? It doesn't have to be capable of running a boiler or whatever? Just curious about the feasibility of geothermal.
'off the grid' has gotten very overloaded because some people take it to mean the power grid, some people take it to mean all utilities, and some people take it to mean self-sufficiency for extended periods.
An engine that could run off a wood-burning fire and was built to last a couple decades would strike me as really neat - this not so much. I suppose other places have more issues with the power grid reliability, but it's presumably more efficient to maintain the current infrastructure than to get one of these into every house.
Natural gas is also going to get much more expensive if they ever push fracking regulations through - the current pollution from gas leaks is actually worse than burning an equivalent amount of petroleum.
> Natural gas is also going to get much more expensive if they ever push fracking regulations through - the current pollution from gas leaks is actually worse than burning an equivalent amount of petroleum.
Interesting. Do you have links to further reading?
Something you can stick in a cabin to power odd appliances or a computer and not have to worry about carrying fuel in (not very practical I admit).
Simple thermoelectric generators are tricky because you have to maintain the temperature difference - generally only good for brief use or with a battery.
> Interesting. Do you have links to further reading?
To be honest, it's information I got second hand from some climate researchers I used to work with. I wasn't planning to weigh in with google results, but this blog does a very impressive job of documenting the back and forth with links to papers - http://www.carbonbrief.org/blog/2013/08/shale-gas-more-or-le...
However in quite a few places the practicality of prepaid metal gas cylinders beats installing electric utility lines & meters, ensuring efficient transformers, preventing pilfering/meter tampering, etc.
This is traditionally called "micro CHP". It has potential in places without district heating infrastructure, otherwise DH CHP is much more efficient.
These aren't really new. Eg here is an article looking at an existing commercial gas powered Stirling micro CHP that's quiet and designed for your house: http://www.f09.fh-koeln.de/imperia/md/content/personen/somme... - there's also a comparison to an ICE based equivalent and it has much better electricity generation efficiency.
The total efficiency is going to depend a lot on where you use it. The heating output is locked to the electrical output so you're always going to generate the 5 kW of heat per each kW of electricity, so you have to stop the plant when your hot water tank and house is heated up - or start throwing away all the heat and just run it as a low efficiency genset.
The large pool case sounds like a fit, but from another perspective it's just greenwashing the huge energy sink of the pool. The laundries & restaurants case sounds better here. Or regular houses in climates where a lot of heating is needed most of the year.
Admittedly, the biggest news is that they might produce a cogeneration heater for <$10K.
A nice thing with cogeneration is that it works best when photovoltaic panels work the least. My case isn't typical, I live on a boat in Europe. She has panels which could push 5-6kWh/day on average in summer (they don't because our batteries are full long before that), but only 1kWh/day in december. We need 2-3kWh/day to be comfortable. So, we need more than what PV panels provides exactly when we also need to heat the boat, so a cost-effective CHP solution would be great.
Also, I'd like this to run on wood pellets, or diesel fuel: replacing the electrical grid with the natural gaz one is a bad idea, especielly considering that the expected yield of non-conventional extraction methods is continuously and rapidly adjusted down.
If you run the number on based on an assumed 30% efficiency and retail gas costs of $0.8 - $1.50 a therm (I think that's reasonable), then you come up with a cost per kWh of electricity within the $0.09 - $0.12 range many US utilities charge. That is, on a cost-of-electricity basis it's a wash.
Mind: gas delivery networks likely would crumble (hopefully not literally) under the increased demand.
Depending on system costs, this could be viable as a back-up power generation option (blackouts, etc.), where electrical service might fail but the gas supply would still work.
Capturing and making use of waste heat could indeed be useful. I see the possibility of full grid independence as very slim, and not particularly compelling (with distributed small, renewable, and intermittent generation, the grid is a useful way to move surpluses and deficits around). Though being somewhat immune to major grid disruptions is a possibility.
I'd also keep an eye on natural gas trends. Supplies aren't endless, though the US EIA's estimates suggest a reference resource case of increasing extraction through 2040 at least, the less optimistic low resource case suggesting a peak by 2030. With fracked oil extraction very likely to peak before 2020, a transfer of fuel and energy uses onto natural gas will change market dynamics considerably. I've got my doubts as to how long gas will remain cheap. And suspect that its increased use in transport (EIA sees a large role in trucking) other uses may be limited.
Dean Kamen is one of my heroes, actually. In particular, his effort to make water purification machines for poverty-stricken areas is likely to have more health impact than anything currently doable. Given that some significant fraction of diseases are water-borne.
Yes and his work in FIRST. It may not be as philanthropic, but I've seen it save lives in the US. Kids who otherwise would turn to substance abuse/vandalism/crime, FIRST teams (at least my team) provided a safe, loving, and an actually exciting/engaging/educational experience to kids in not-so-nice homes and families. That man is doing something really great.
The approach is not entirely new. A company called Sunmachine in Germany built a similar device producing 3KW and fed by wood pellets made from saw dust - so even more carbon friendly. Sunmachine had to file for bankruptcy as it couldn't find the working capital to produce the neccessary machines it had in its order books to bridge the gap before getting paid after installation of the units. It was aimed at the residential property market.
it was during the 2008/2009 credit crunch - banks just wouldn't loan. It was eventually auctioned off. They also had a technology to run the stirling engine via a solar dish that tracked the course of the sun...pretty cool stuff
Stirling Engine combined heat and power appliance the size of a dishwasher. About 10,000 Euros for 1KW of electricity output. I don't think it made it in the marketplace.
Tangentially related - Anybody know anything about the progress or success of the BloomBox from Bloom Energy? They were billed as a close-to-magical way to produce energy when they were first announced, but I haven't heard much about them since then.
Maybe I'm just failing at finding the info, but does anyone know how much natural gas is used to create that 10kw of power? As the Stirling engine is a heat engine, my first thought is that one could potentially have a dual-mode generator here, using solar thermal, etc, to help generate power in those areas where it's amenable to do so.
Stirling (and other thermal-cycle engines) are about 30-35% in converting heat energy to useful work. In this case electricity. So dividing 10 kW by 30% will give you the rough energy input. Casting that in therms/hr. (usual natural gas billing unit in the US is therms), it's about 1.14. Residential price is on the order of around $0.80 - $1.50/therm, so you're looking at about $25/day for 10 kW of continuous power. Which isn't far from what you'd be paying for electricity: $21 - 29 at $0.09 - $0.12 per kWh.
In terms of volume, 1 ft^3 is about 1025 btu, a therm is 10,000 btu, so you're looking at 97.5, let's call it 100 ft^3 of natural gas consumption per day.
As for running a Stirling engine on solar energy, or another heat source, yes, you could do that. Again, you need 33 kW of input power, which means a 33m^3 collecter surface -- that's 5.8m on a side, or 19 feet.
Because the Stirling's hot end is a point, you'd need tracking systems or a working fluid to deliver heat to it from your mirrors.
Incidentally, you can answer a lot of these questions using GNU units, written by Adrian Mariano. The great thing about it is conversion between different units and relationships, e.g., energy per hour per unit area. I find it invaluable in looking at energy, renewable, and related issues.
Does this seem like a step backward to anyone else? We want to generate electricity with renewable sources instead of fossil fuels. Also, I'm skeptical that a small in-home generator of any type could compete with the efficiency of a commercial power plant, even if that plant burns natural gas.
I'm skeptical that a small in-home generator of any type could compete with the efficiency of a commercial power plant, even if that plant burns natural gas.
A small local generator will certainly be behind what a big commercial generator will do, but if the waste heat is also being harnessed ("Combined Heat and Power," or CHP), combined efficiencies of 60%-80% are possible. Commercial electrical generation is typically around 40% efficient, so CHP really can offer very big benefits.
Of course, there's nothing fundamentally efficient about a single family living in a huge mansion with a 10KW energy demand and a big heated swimming pool.
I would have guessed these things would be most attractive to hotels, universities, airports, truck stops, apartments and condos, and other institutional-scale places that have a significant round-the-clock demand for electricity and hot water.
I wonder what it says about the device and the market that they're planning to sell to well-heeled homeowners first.
> I wonder what it says about the device and the market that they're planning to sell to well-heeled homeowners first.
I think the key is in where he says a unit with a fifth the output wouldn't be a fifth the cost. If he can use the luxury end of the market to drive the manufacturing costs down, I'm sure general retail won't be far behind.
Renewables like wind and solar need EITHER enormous storage capacity, OR baseline supply to work with modern consumption patterns. Storage is both expensive and environmentally destructive - these engines could be a good fit for baseline generation to dramatically reduce the need for storage in a renewable system.
This is the first product, and is targeting areas where cheap natural gas is plentiful. However, because it's an external combustion engine, I imagine it wouldn't be too difficult to build a future product where the heat differential is created from a different source, like solar tiles, or through geothermal differences.
The electrical generation probably isn't more efficient, but the household/facility is, at least during times it has a use for the waste heat.
The waste heat will be roughly 50% of the energy involved. The difference between the generators won't be that big. So each unit of fuel provides more energy to the end user (which is what I am calling efficiency, the energy utilized for something vs the energy consumed making it available).
> So in 10 years will everyone have one?
> “I’d say yes. Ten years from today the probability that you are depending on wires hanging on tree branches is as likely as that you’ll still be installing land lines for telephones. Close to zero.”
Well this seems out of touch with reality. This is how I read it: "Why maintain 1 power plant when you can instead ship and maintain 100000 instead?"
I remember when Kamen was going on all the morning shows saying that he was going to change the world and transportation. Many speculated that it was a Sterling Engine. It was the Segway.
Why do they keep talking about pool heating? If I just want to heat up something up and have natural gas on hand, I'm just going to burn the gas, not run it through some engine and use the electricity.
Cogeneration is a great way to increase the efficiency of these systems. It's not that you would buy one to heat your pool, it's that you can heat your pool from the waste heat of the power generator. The power plant that generates your grid-delivered electricity also generates waste heat, but it's many miles away so that heat is discarded.
A sterling engine isn't the only type of generation that works for co-gen. Most of these micro generation proposals involve some form of waste heat recovery in the form of warm water.
The engine's waste heat heats the water. That's why it's efficient; some of the "waste" heat is recovered and put to use.
A Stirling engine in particular needs an explicit heat sink to cool some parts of the mechanism; shuttling a working fluid (and its heat) back and forth between a hot end and a cold end is how it works. In this case, the cold end is the swimming pool.
Yes, I know that, but in familiar cases (like an internal combustion engine) the heat sink is mainly just venting exhaust to the atmosphere. The heatsink exists as a part of the environment, almost an accident of the design. It's a sort of implicit heatsink as opposed to an explicit one.
Genuine question: if we wrap an IC engine with a heat sink that captures the excess heat for re-use, what do we get? And is overall more or less efficient than using the sterling engine in article?
Yes. It's less efficient, but not significantly so. The term you want to punch into Google for more information is "micro CHP" (combined heat & power).
An interstitial, a popover to explain the site's navigation, then an ad which scrolls over the content? You've got to be keen to want to read this stuff.
> "Kamen believes that aside from mansion owners, the Beacon 10 is just right for businesses like laundries or restaurants that use a lot of hot water. With commercialization partner NRG Energy, he’s so far deployed roughly 20 of the machines."
If the primary use for a potential customer is going to be heating water, essentially doing heat->generator->electricity->heat->water, how is this a good idea? Surely people who want to heat lots of water would do better if they cut out the middlemen and just did heat->water.
Of course electricity is more versatile than hot water, but if your primary focus is on heating lots of water and you are already committed to making heat yourself, it seems senseless to me to not just apply the heat directly to the water.
They wouldn't be using electricity to heat the water. Of course you would end up using less gas if you just heated the water directly like most of us already do for our morning shower.
The efficiency of any heat engine depends on the gradient between the input and output temperature. So if you have a constant supply of cold water the Stirling engine can operate very efficiently, and the cold water becomes hot water which you can use for other things.
Of course, like I said, this is true of any heat engine. You can do the same thing by heating a boiler and using the steam to drive a turbine, which also generates waste heat for other things.
I think the idea is that you're heating up water anyways [for laundry/dishwashers], you might as well get power out of it. It's kind of the same principle as if you're using an electric heater, you might as well run a bunch of bitcoin miners that generate heat to lower the amount the heater has to be on, since they're both resistive loads. And with the miners, you get some coin as well.
Kamen has demonstrated a great talent for generating media coverage of his products - think back to the incredible level of media attention around launch of "It"... which turned out to be the segway. If he's working on a new product, expect a similar level of media engagement.
There's a good book about development and launch of the segway "CODE NAME GINGER: The Story Behind Ginger and Dean Kamen's Quest to Invent a New World"[1]. It's in paperback as "Reinventing the Wheel: A Story of Genius, Innovation, and Grand Ambition"[2]. It also has some interesting coverage of what happened inside the company during that time.
As cool as this is. Even with the fact that in the US it's decided you'd hook it up to a gas line. There is still the issue of "leasing it" to the homeowner.
Seriously, why would anyone lease a home generator. Maybe I'm old school, but I can't see the benefits to the homeowner if you're undercutting your savings from installing one of these devices by paying "RENT" on the generator?
This article reminded me of a very log blog by some guy in south america who detailed building his own hydroelectric power plant. I wanted to find it so I could link it here but I cant. Help?
Let's look at who's behind it, what it is, how it can be used, and where the benefits accrue:
* Who: NRG, while not a utility, is an owner of utility-scale generation capacity. They wholesale electricity to utilities for distribution and resale. Their portfolio is largely fossil-fuel but increasingly renewables [1]. They see themselves in the "death spiral" some other generation suppliers do [3][4].
"A single unit can integrate natural gas, solar panels,
wind turbines and batteries for storage," NRG says. "The
device is connected to the grid, which allows the two to
work seamlessly together. But if the grid's power goes
down, the engine's energy stays up. Any excess generated
energy can be sent back to the grid and may be credited
for your benefit."
.
Aside from the 15 kW maximum electrical output, output
can be used for space heating (35 kW or 0.12 MMBTU) or
hot water (200 gallons per hour at 70° rise). Additional
uses include snow melt and spa and pool heating.
.
The technical specifications are subject to change.
.
When necessary, the unit seamlessly transitions to a
backup power system, to maintain continuous operations,
NRG says.
.
The Beacon 10 unit's dimensions are 3 ft. 8 in. long by 2
ft. 6 in. wide by 4 ft.high, which NRG says is slightly
larger than a washing machine.
.
The unit weighs 1,500 lbs.
* How it can be used: Disrupt the utility's business by selling or leasing equipment directly to end users, and by doing energy arbitrage with the utility.
The whole business of solar integration and battery integration is optional, and smells of "greenwashing-by-association" to me: The cheapest install of this machine would not include a solar component nor battery, each of which might be very expensive in addition to this machine. Who could afford all that? Certainly not everyone.
* Where benefits accrue: See [5] for the long story, but it looks like NRG mainly. If you lease it from NRG, you may not get as much of the benefit of energy arbitrage.
* What I think of it: Regulators should insist on a "connection charge" for this and accept energy sold at wholesale prices, while selling to the user at retail prices. Disclosure: I own a solar system with net metering, but believe a "connection charge" is entirely reasonable /for those who have their own generation capability/ and thus use the grid for sale of distributed generation, but /not/ for those who don't.
> The cheapest install of this machine would not include a solar component nor battery, each of which might be very expensive in addition to this machine. Who could afford all that? Certainly not everyone.
I've seen German stirling engines that use a fresnel lens focusing sunlight to supply the heat - and the most expensive part is the sun-tracking software and equipment.
I have serious objections to anything that increases reliance on fossil fuels. Or anything that releases more carbon to the atmosphere for that matter.
There are clean ways to get you off the grid. This is not one of them. At least not entirely.
