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Cost goals met, the DoE is moving on to address grid reliability in solar (arstechnica.com)
166 points by vasili111 5 months ago | hide | past | web | favorite | 90 comments

This might actually work. A lot of of the dirty work can be done in places with solar /wind power and during the peak energy producing times.

Like for aluminum smelting which apparently needs ~10x the energy that steel needs https://theconversation.com/the-trouble-with-aluminium-7245

But they can do that right next to hydro-electric plants with much more reliability.. If I am not wrong, Alcoa did shutdown their plant in central Washington (crypto-valley), so aluminum smelting is probably not that rage anyway.

edit: Crypto-mining may be one alternative, you are converting energy into currency is the most straight forward fashion. Could be the way, who knows.

It's hard to build airplanes out of Bitcoin. That aluminium must be produced somewhere.

The point, If they are closing Aluminium smelting plants when they are being sold 2cents/kwh from a reliable hydro-electric plant. Wind and Solar's chances are slim to none.

I am not questioning the utility of Aluminium here.

You can smelt it in remote places. Iceland has a lot of Aluminium smelting because energy is so cheap. Doesn't mean that you need to produce the aluminium products there.

Aluminum smelting is still popular in Germany where they are being paid to offset the variability of wind/solar there by ramping production up and down.

I have a suspicion that this is being used by Germany to feed them a disguised subsidy.

That might be a good use of solar actually. Smelt the aluminum right at the site, which might have poor grid connectivity. Generate your own power ultra cheap & use it directly for smelting. Save on raw material transport costs. It would be interesting to see a cost / benefit analysis here.

Efficient aluminum smelting requires reliable, continuous power for weeks at a time.

Photovoltaics are cheap, but the diurnal variation makes them singularly inappropriate for aluminum smelting.

And could the economics eventually work of photovoltiacs + battery storage ala a tesla powerpack?

Why does it need to be continuous?

In a nutshell, allowing the aluminum to solidify gums the batch process up catastrophically.

Friends who used to work at aluminum plants were surprisingly happy when the plant was snowed in: it was more economical to keep workers onsite running rotating understaffed shifts at triple pay for the duration than to let the pots solidify.

From the Wikipedia page on aluminum smelting:

An aluminium smelter consists of a large number of cells (pots) in which the electrolysis takes place. [...] Smelting is run as a batch process, with the aluminium metal deposited at the bottom of the pots and periodically siphoned off. [...] However power must not be interrupted for more than 4-5 hours, since the pots have to be repaired at significant cost if the liquid metal solidifies.

In addition to Wikipedia, there’s a surprisingly good explanation here:



I'd love to see some napkin math on this.

Gasoline has an energy density of 13 000 Wh/kg. Lithium-ion rechargeable batteries have an energy density of ~250 Wh/kg, and LiMnO2 lithium primary (non-rechargeable) batteries have an energy density of about 300 Wh/kg. Let's assume energy density near the upper end of that Wikipedia page - say, 6 500 Wh/kg, we have half the energy density of gasoline, and 26x the energy density of lithium ion rechargeables. So your Tesla 100D with 540km range becomes a 14 000 km/8 500 mile range. You can get a battery swap a few times a year, a little less frequently as you'd get an oil change now.

But that's still half the energy density of gas. Instead of buying 12 gallons of gas every week or two, you're now buying 720 kg of aluminum every few months. All the gas tanker trucks you see on the road right now? They're replaced with twice as many aluminum-air battery carrying trucks. All the pipelines, supertankers, rail cars, etc? Replaced with aluminum carriers. And on top of all that, gas turns into CO2 and water, disappearing into the atmosphere. With this plan, you have to ship these aluminum batteries back to the manufacturer for rebuilding!

You'd have to build thousands of mostly automated battery reconditioning plants and scatter them across the country for that to work.

Awesome, thanks for that.

So are batteries the only viable storage solution? Does any other storage compare in terms of price and scale? (allowing a dollar value to be put on efficiency)

If not I'd assume Tesla would be well positioned there, but I wonder if even it could scale that far.

You raise an important topic with somewhat unhelpful framing: "viable" is a boolean label for a continuous variable, the value of storage, which is context-dependent today and an important feedback element in ever-shifting complex systems.

Here's the frame I'd suggest: batteries, demand-response (to which efficiency contributes), grid management, and rate schedules are mutually supporting tools which allow us to continually improve our use of power along several axes, including GHG emissions, efficiency, end-user price, and reliability. There isn't one accurate and stable perspective from which to consider the "value" or "viability" of, say, compressed-air storage. Instead we have a web of complex local, regional, and global situations and concerns, and varying sets of goals to pursue within those situations.

Don't underestimate pumped hydro. It's already at about $125/kWh.

The Bath County Pumped hydro station stores about 35-40 GWh of power (35,000 MWh), cost $1.6 billion in 1977-1985 or so (so inflation-adjusted about $100-150/kWh).

Compare to the largest ever battery storage project, the Tesla 129MWh installation in Australia is "guaranteed" for $250/kWh, but that doesn't include a lot of extras (the storage facility has a pretty high discharge rate, able to dump its storage in roughly 1.3 hours vs like 4-8 hours for better battery life and lower secondary costs).

So in terms of cost and scale, pumped storage steal beats the best battery installation by a factor of 2 (not counting likely longer service life before replacement, although that depends strongly on how hard you cycle the lithium batteries), and scale-wise beats it by a crazy factor of 300.

Pumped hydro does have some geographical constraints, but there's a lot more opportunity to build them than many detractors suggest. (Obviously, the sweetest places to build them are by definition limited, but you can also build pumped hydro with a very low head, like on some of the Great Lakes projects, or with a very large head requiring very little water.... you don't need a nice canyon feature for pumped storage, a big round concrete reservoir on top of a hill works just fine, too. And with enough volume of water, you don't even need a hill.)

And I say this as a firm believer in the potential (heh) of the lithium battery and in Elon Musk. Pumped hydro should not be ignored.

Keep in mind those two solutions are on opposite sides of the world. I found this [1], which gives the projected Snowy Mountain 2.0 proposal in Australia at $250/kWh (AUD, presumably).

Regardless, I don't disagree that pumped hydro can still a viable choice in some places when it comes to large scale, I think South Australia made the best choice going with battery storage, even if driven from mostly political reasons.

The SA govt needed to show the federal govt they were capable of holding their own on their renewable policy, against the federal line of the Snowy Mountain 2.0 pumped hydro. Having something up and going in ~100 days with very few unknown factors (pour concrete, install batteries, hook up to grid), opposed to waiting 5-10 years for a solution from the federal government that hasn't even finished a feasibility study yet, and has so much more risk (geological survey, environmental survey, new transmission lines [0] etc)

The other advantage of battery storage I see is that it is immensely flexible for a rapidly changing market. Underprovision? Just buy more. Overprovision? Truck them somewhere else, lease them to a business with peaky loads, plenty of other options.

[0] http://www.illawarramercury.com.au/story/4681519/snowy-hydro... [1] https://bravenewclimate.com/2010/04/05/pumped-hydro-system-c...

I still hope Ares [1] will turn out to be competitive. The idea is sound and can be build in most areas in the world. You could potentially reach storage volumes within short time frames that only pump storage can rival.

Alternatively, there was a German experiment to use underwater concrete pump storage to provide storage close to production for offshore windfarms. Not sure where the project is at, but these ideas could well supplement batteries.

[1] http://www.aresnorthamerica.com/

I very skeptical that lithium-ion batteries are the end game for huge-scale energy storage.

Lithium-ion batteries are the "hot" energy storage. Efficient, powerful, and very light, but also expensive great for a laptop or a car, not so great for massive-scale "cold" storage.

Simpler things like flywheels, compressed air, reverse hydro, other cheaper battery types all seem like more plausible options.

Adiabatic, compressed air, looks to have some of the best, most realistic, future potentials.


Like a sister comment it's worth pointing out that there are many different batteries besides the tesla like


Is an example - from Donald sadoway at MIT who presents easily my top 5 TED talks on the idea as well (molten salt storage)

But we already have good examples of electricity storage by pumping water uphill to reservoirs in Scandinavia etc

Storage is probaly not a problem - mobile storage might be

Batteries, Jim, but not like we know them: https://arstechnica.com/information-technology/2017/07/germa...

Also, big maglev centrifuges are being looked at, and of course pumped storage, which is pretty old-fashioned.

Heat bricks are distant possibility, seems lot of work to be done, need to store higher temperature than currently possible, only useful immediately for industrial heat if temperatures met and then possibly electricty generation.


I wonder how much lower it can get over the next decade.

The same project published goals last year, for 2030.

2011 goals targetting 2020:

$0.09 per kilowatt hour for residential photovoltaics (PV)

$0.07 per kilowatt hour for commercial PV

$0.06 per kilowatt hour for utility-scale PV

2016 goals for 2030:

$0.05 per kilowatt hour for residential PV

$0.04 per kilowatt hour for commercial PV

$0.03 per kilowatt hour for utility-scale PV

This slightly older piece from 2015 make some projections based on a 16% learning rate and suggests various large orgs have estimated similar levels:


$0.03 per kWh for utility-scale PV in Dubai, will go online in 2020 (https://pv-magazine-usa.com/2016/11/29/worlds-cheapest-solar...)

I believe the Sunshot numbers are specifically about the USA. The amount of sunshine, cost of finance and installation costs are three big factors that vary by location, all three of which are probably contributing to that particular bid, but yes the general trend is looking very good.

What’s it going to take before US homeowners start putting solar on their roofs en masse? With all the power outages in Florida after the hurricane, rooftop solar would have been useful.

Rooftop solar only helps in scenarios like that if you also have an attached storage system. You're not going to power your fridge/oven/dryer directly from the panels.

I would also like to see rooftop solar become widespread in the near future. But I think for most people to get on board, they'll need to be able to break even on the investment within something like 3 years.

Storage makes it better, but even just being able to charge your laptop, phone, car and run your air-con during the day would be a win.

I don't think most solar installations are designed to operate without a grid connection though, and even not all powerwall installations can run off grid.

Though I'm not sure that they beat a generator (diesel or connected to your gas line) if you really anticipate regular grid outages and probably won't for a while.

>Storage makes it better, but even just being able to charge your laptop, phone, car and run your air-con during the day would be a win.

You mean the car that is parked during the day in your office parking lot a few tens miles away and the laptop and phone that you are carrying with you?

Seriously, without some form of (efficient) storage system, the whole thing depends on exchanges on the grid.

Off grid - as I see it - is a very nice solution (still with some minimal storage) for a hut in the woods, where everything is specifically designed for low power (and where you don't have a dishwasher, a washer, etc.), replacing - in a more environment friendly way - the noisy generator, but still it remains something good for youe being there on - say - every other weekend.

Having an el-cheapo (diesel or gasoline) small generator for emergencies is handy, but only for those hopefully very rare emergencies, the cost for a good quality (suitable to run often and in several hours stretches) generator and for the fuel is not competitive with solar (though of course the initial cost of solar is still higher).

I was talking about in the "hurricane just hit your state" situation, in which you may not be commuting to work as usual, though in future two car families with one car at home during the day will not be unusual.

In the normal run of things though, I agree, the correct and sensible thing is to be grid connected, and have sane regulations that ensure that excess from generating customers gets redirected to their neighbours and that everyone gets compensated fairly for their contribution to a well running grid so that incentives are correctly aligned.

This value will in most cases be more than utilities would be prepared to pay if left to choose a number themselves and they will unfortunately generate propaganda to make solar installations seem like free riders rather than go by actual studies of how much they reduce the peak demand. In both Australia and the USA studies have found Billions (with a B!) in savings thanks to solar installations.

How do solar panels behave with 150mph+ winds? I could imagine that they'd see significant damage in a storm like this. I believe roofs in parts of Florida have to be prepared to withstand high winds, not sure if that can be accomplished with solar panels.

I have a house down in Florida and it has solar, but not on the roof. When storms come, the caretaker hits a switch and they rotate to be upside down. They don't have a broad cross-section, so they should do okay in some pretty strong winds.

I have the same thing here, up in Maine. I live in one of the windiest places around and it hasn't been a problem. It gets flipped for blizzards, mostly.

If windows can be built to survive it, so can PV. Might be prohibitively expensive, but wouldn't a potentially sacrificial layer of plastic or wire reinforced glass a few cm above the PV panels suffice?

As I understood it it's not against damage but so that they wouldn't get lifted from the roof and become projectiles. Since they're probably light compared to their surface area, I can imagine that they'd fly around at least as easily as shingles. But maybe they can be attached well enough to prevent this.

Everyone seems to be forgetting that you can get paid to transmit your extra power back to the grid during the day. Air conditioning, for example, is high during the day. You might not need it at home but someone else will.

>Everyone seems to be forgetting that you can get paid to transmit your extra power back to the grid during the day

The idea in my previous post was:

>the whole thing depends on exchanges on the grid.

and anyway we were talking of off-grid setups.

Some states/locales still don't allow resale back to the grid. I wish Texas did.


There are some inverters on the market that can directly power a load with no battery or grid connection.

I guess this was one of the first: http://www.smainverted.com/how-to-explain-secure-power-suppl...

At $500 additional cost, calling it a design issue is probably the correct thing.

Of course an auxiliary plug is way less convenient than whole house power, but a couple thousand watts is way more convenient than no electricity.

We have one of these, and if the power goes out it's got enough power to run e.g. the fridge/freezer so your food doesn't go bad. It can't handle even momentary overloads, so it's not good for powering motors, but I've run our fridge on a UPS powered by the inverter and that works fine.


We need to decentralize energy generation (solar) AND cellphone signals (mesh networking).

Here I expound on it at length:


>hey'll need to be able to break even on the investment within something like 3 years.

???? That's a 33% discount rate. Kind of insane expectations... I put solar on my house in 2014, after doing a bunch of analysis showing the breakeven point was 8-12 years. After having it and checking the utility bills, it looks like it's going to be 10-11 years. Maybe less if they raise their rates.

"Rooftop solar only helps in scenarios like that if you also have an attached storage system."

These exist nowadays [1]

[1] https://www.tesla.com/powerwall

Unless there is a some level of prepper in you, those powerwalls do not make any economic sense. Most of the Solars that SolarCity installs are grid tie-in, means no power at substation means no power even with those panels on roof.

Customer located storage solutions do make economic sense in many situtions, that's why some utilities will pay you to have one in your home and let them control it's charge/discharge when they need to. Usually that economic benefit is left on the table due to the utility being poorly regulated but that's subtly different from the thing itself not making economic sense.

Can you provide a link to these any of these utilities?

Most are so focused on reliability they are quite resistant to pushing the limits. There must have been some cost savings such as avoiding building or upgrading a substation

If US utilities were focused on reliability, they would have stopped putting power lines above ground a long time ago.

The power grid in the US is way more unreliable than any other country I've experienced, and I can only think that it's because the utilities are so profit-focused that they put lowering infrastructure costs above losing a little revenue due to power outages here and there. After all, the real societal costs due to unreliable power are completely externalized onto their customers.

The utilities are fine talking about reliability when it comes to newfangled competitors like solar, but that's mostly because they're a threat to their bottom line, not because they actually care about reliability.

the cost for overhead distribution might be $10,000 per km whereas best case underground (easy digging) is $30,000-$40,000.

whatever your connection fee on your monthly bill is (mine is $10 CAD), would you like it to be 4x higher?

> "...and I can only think that it's because the utilities are so profit-focused that they put lowering infrastructure costs above losing a little revenue due to power outages here and there."

There is more that goes into transmission line engineering than cost. "Agility" is important, and it is a lot harder to tap underground transmission lines than overhead lines. Outages, while less likely for underground, are actually, on average, longer than overhead line outages.

the PG&E project is a technology demonstration which is a nice first step

green mountain power appears to be a retailer of electricity and not a distribution company; they don't own any power lines. The distribution co. will have to be on board to safely accept power flowing in the opposite direction (from the load), and for the most part they have no incentive for this so don't really care.

Wikipedia says they own 21,000Km of power lines:

Green Mountain Power (GMP), a subsidiary of Gaz Métro, is the largest electricity distributor in Vermont, serving over 70% of the market and more than 260,000 customers. GMP’s core business includes the distribution, transportation, generation, purchase and sale of electricity in Vermont and, to a lesser degree, electricity transportation in New Hampshire and electricity generation in the states of New York, Maine and Connecticut.

The GMP network comprises over 1,500 km of overhead transmission lines, 18,000 km of overhead distribution lines and 1,600 km of underground distribution lines, located mainly in Vermont but also extending to New Hampshire and New York.[17]


You may be confusing them with Green Mountain Energy, which got spun off and bought by someone else:


At least up here in the PNW, grid-tied solar systems are actually required to shut down in the event of power grid failures (sending power back into "dead" lines is a good way to get people killed), so while I definitely would like to see what you're talking about, I'm not sure a selling point of it is resiliency for power outages.

Safety disconnects let you keep the house powered without sending power onto the grid, though.

Are these safety disconnects you're talking about at the home, or are you talking about the utilities circuit breakers?

I'd still see that posing problems for crews of electricians. A customer home safety disconnect could fail to operate in which case you'd be feeding the supposedly "dead" distribution line.

Serious question does US have underground cables?

Some are. Manhattan is a noticeable case where pretty much the entire power grid is buried.


>All told, the Edison Electric Institute estimates (pdf) that some 18 percent of the country's distribution lines are buried. For the transmission system, only about 0.5 percent of lines sit beneath the surface. "Undergrounding an entire power system," says EIA, "is considered cost prohibitive." Instead, most utilities will just try to bury a few key lines.

Some places, yes. Unfortunately, in most places we don't. Usually wealthier neighborhoods get underground cables, but even then most long distance cables are up in the air, so if a hurricane destroys a long distance cable, you are screwed even if you have underground cables in your local neighborhood.

The low population density makes underground cables very expensive in many parts. Even where you have underground cables for neighborhoods, longer range transport will be done above ground (as in many parts of Europe). It's probably cheaper to rebuild poles every few years than laying underground.

Long distance lines are usually so large you don't have to worry about trees falling on them, though.

They can still be damaged by debris flying around. Happens less often but just two damaged lines can cause blackouts for huge areas. And repairing them takes much longer. But not sure if any of those got damaged during the hurricane.

> "And repairing them takes much longer."

Repairing underground lines takes longer than overhead lines.

Price of storage and ease of installation isn't there yet net metering allowed a large number of home solar installations. Blocking those has slowed it down. The price of panels etc is less than half of a home installatons so panel prices coming down is unlikely to fuel much morenhome solar growth

In most places unless there are huge subsidies (e.g. net metering) commercial scale solar should be less expensive overall. Solar owned by the homeowners might help in niche scenarios but overall it's often just not a good investment for many individual homeowners

Net metering technically isn't a subsidy since they are being compensated for a benefit they provide, it's just forcing utilities to not pay less than they're benefiting, and solar is a good investment for individuals when sensible regulation ensures they get a share of the benefits they provide to the grid.

Here's a respected centrist think tank's take:


"Nevertheless, by the end of 2015, regulators in at least 10 states had conducted studies to develop methodologies to value distributed generation and net metering, while other states conducted less formal inquiries, ranging from direct rate design or net-metering policy changes to general education of decisionmakers and the public. And there is a degree of consensus. What do the commission-sponsored analyses show? A growing number show that net metering benefits all utility customers"

It's a subsidy. Powerplants don't get paid retail rates.

Powerplants often get paid many multiples of retail rates at peak times. The retail rates are averages. And, in places with air-con usage, those peaks coincide to a high degree with solar production.

So it's not a subsidy.

What if we paid consumers like powerplants then?

The closer we get to the economically perfect solutions the better, but even powerplants have lots of weird regulations and "subsidies" around their pricing e.g. paying gas peakers to be on standby because it's not clear exactly how much power will be needed. At some point you have to accept simplicity rather than waste money on perfection. Net-metering is a pretty good solution by any measure.

Why would we do that?

The structure of how power plants generate electricity and are paid for it are idiosyncratic to their particular operating and economic conditions. It would make no sense to try to force something completely unlike that in to their regime.

Thus the many efforts that are designing a "value of solar" regime that encompasses the important aspects of solar, so that equitable and efficient cost schemes can be designed.

OTOH, what is the risk of a hurricane destroying your rooftop solar installation? Serious question.

Pretty significant, I'd imagine even without flying debris. There's often an air gap in between the roof and panel which is going to make things really exciting in 100+mph wind. Maybe building codes could be updated so that there's an airfoil on the outside edge of rooftop installations, like on your car's sunroof, to reduce the likelihood of liftoff?

I would guess the same as a hurricane destroying your roof?

Seems like it might be higher. Wouldn't all the 100mph debris crack the panels?

I don't think they're impact resistant ?

Hurricane prone areas have building codes that require hurricane-proof installations. Most panels are built withstand extreme conditions, e.g., 2-inch hail, etc.

I recently read that in parts of Florida the roof needs to be secured with concrete to avoid wind lifting tiles. Can this be done with solar panels? I always had the impression that there's space between the panel and the roof. In this case, couldn't wind of a hurricane lift the panel?

But does "withstand" mean "continue to function at 100%" or "probably not kill anyone nearby"?

The building codes are mostly the latter - maintain integrity of the roof, don't become projectiles. The manufacturing standards are more the former, such as "withstand 2 inch hail at X mph and maintain at least 95% of rated capacity"

Any more useful than a generator?

Generators already have the inverter built in. "Storage" is your tank of gasoline or whatever fuel it uses.

Generators are cheaper and more reliable for emergency situations right now.

I think installation costs still have to come way down.

Outbrain? Et tu, Ars?

Get ready for 8c or 9c per kwh, courtesy of Trump's solar tariffs.

Actually, please get ready to fight these tooth & nail.


Chinese solar tariffs came in under Obama, not Trump.

It was also pretty clearly done at the behest of the fossil fuel industry and "greenwashed" by pretending to be done to protect US solar jobs. US solar manufacturing (as opposed to installation) is a pretty tiny industry with no political muscle.

The justifications were cringeworthy too. I took a glance at the US trade dept documents accusing China of protectionism and the first one I saw made accusations of "free advertising" because Chinese local government promoted a local solar company on its website.

Sorry, to be clear, the ITC is now considering a case which would bring a minimum import price to solar cells. Meaning this would be applied to ALL imports from ALL countries.

I can still hear many Conservatives saying: "But SOLYNDRA!!" :)


$5 trillion/year global fossil subsidies is nothing to sneeze at [1]. And that's not counting indirect fossil subsidies such as $2T wars on fossil/defense's behalf.

It suddenly makes a few $20 billion storm cleanups pale by comparison.

[1] http://www.sciencedirect.com/science/article/pii/S0305750X16...

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