There’s a degree to which, from my perspective, watching for new developments in power storage feels a bit like watching for new developments in fusion power. There’s a promise, both explicit and implicit, that if we just wait a little longer, we’ll innovate our way out of the environmental crisis.
To start with, I want to address that last bit – even if we dealt with climate change, there would still be problems like the “insect apocalypse” (more on that in the coming days), “forever chemicals”, wasteful water use, and so on. Climate change is the most urgent environmental issue, but it’s not the only one poised to end human life as we know it. Multiple systems are in the middle of collapsing, and all of that spells Bad News. That’s why we need a holistic approach to dealing with how humanity interacts with this planet, so that we take care of the world that we hold in trust for those who come after us.
The most common response I see to the intermittency of wind and solar power is the use of various technologies for grid-level storage. I divide these into four basic categories: kinetic energy, potential energy, fuel, and batteries. Obviously fuel and batteries are both forms of chemical energy storage, but they’re used differently, so it feels right to separate them. Given my lack of expertise in this field, there’s a very good chance that my classification is bad, but I think it works well enough for this article.
Power storage using potential energy comes in a few different forms. One of the most everyday examples is winding up timepieces that run using springs or weights. I’m reasonably certain that placing giant watch springs all over the world would not help much, but all potential energy storage relies on the same basic principle – use power to apply force to something from which it can be released, to set it up for later power generation. The most common method at the grid level is probably pump storage. This generally uses either water or air. In the case of water, it’s pumped uphill to a reservoir of some sort, so that it can be released at need through a hydropower generator. For air, it’s similar, except the air is stored in massive tanks at high pressure.
The other method I’ve seen is to literally to lift heavy objects, so that gravity can be used to generate power at need. My favorite version involves putting train tracks on a slope, and having an electric engine move a heavy train car uphill, so that it can roll back downhill and run a generator.
Kinetic energy storage involves making a large object move, and then using that motion and momentum to generate power. The obvious downside is that for this to be useful, it needs to have very large objects, and they need to be moving very fast, without changing location. Pretty much any time energy is stored this way, it’s using what’s called a “flywheel“. There have been efforts to set up grid-level flywheel power storage, but it seems to be a technology with very, very narrow margins for error. If the flywheel is unbalanced by even a tiny bit, the high rotational speed and high mass of the wheel will cause a wobble that could be catastrophic. Think an unbalanced top-loading washing machine in a spin cycle, but it weighs thousands of pounds. If that starts to wobble, you’re in trouble.
The most straightforward use of fuel for power storage is probably hydrogen. Use electricity to split water molecules, producing hydrogen, which can be used either in fuel cells, or for combustion. The downside is that it’s a volatile gas, which can cause problems for safe transportation and storage.
And then we have batteries.
Basically batteries store energy in the chemicals used to build them, in such a way that the energy is released as electricity when a circuit is connected.
There are a lot of different chemical combinations that will get this result, some of which can be recharged, and some of which cannot. When it comes to grid-level power storage, rechargeable batteries are all that really matter. There are also two basic approaches to storying power in batteries. I’ve seen interesting proposals for a distributed model using car batteries, combined with a “smart” grid, to allow power to be directed to where it’s needed, based partly on where it’s not. An electric car connected to the grid, for example, could be partly drained (with the owner’s permission) during a period of peak demand, and then re-filled when demand is lower and/or supply higher. Divided between the tens of millions of batteries you’d get from switching to electric cars, and there’s far less need for dedicated grid storage batteries.
Of course, the practicality of such a system may fall off if we shift more towards mass transit (which we should), so there’s still the question of big grid batteries. There’s a lot of worry that the materials for battery production – lithium in particular – could end up replacing oil as the biggest focus of war and exploitation. We’ve seen the beginning of that already.
That, combined with the hope for an easier transition through cheaper materials, has had scientists around the world trying to find alternative battery builds. If you follow this research a little, you’ll see headlines promising that a newly developed battery tech will revolutionize the power grid and make renewable energy the obvious choice. I think the first one that really caught my attention was the “gravel battery” a few years ago:
The only economically viable way of storing large amounts of energy is through pumped hydro – where excess electricity is used to pump water up a hill. The water is held back by a dam until the energy is needed, when it is released down the hill, turning turbines and generating electricity on the way.
Isentopic claims its gravel-based battery would be able to store equivalent amounts of energy but use less space and be cheaper to set up. Its system consists of two silos filled with a pulverised rock such as gravel. Electricity would be used to heat and pressurise argon gas that is then fed into one of the silos. By the time the gas leaves the chamber, it has cooled to ambient temperature but the gravel itself is heated to 500C.
After leaving the silo, the argon is then fed into the second silo, where it expands back to normal atmospheric pressure. This process acts like a giant refrigerator, causing the gas (and rock) temperature inside the second chamber to drop to -160C. The electrical energy generated originally by the wind turbines originally is stored as a temperature difference between the two rock-filled silos. To release the energy, the cycle is reversed, and as the energy passes from hot to cold it powers a generator that makes electricity.
Isentropic claims a round-trip energy efficiency of up to 80% and, because gravel is cheap, the cost of a system per kilowatt-hour of storage would be between $10 and $55.
This is a thermal battery, rather than a “chemical” one, but it sure seemed like a wonderful thing back when I heard about it in 2010. It promised effective large-scale power storage at a low price, and as far as I can tell, it hasn’t really gone anywhere since. The company discussed in that Guardian article is no longer in business.
Research continues, though, and now there’s another one, this time promising to use “iron flow” technology:
Flow batteries, however, look nothing like the battery inside smartphones or electric cars. That’s because the electrolyte needs to be physically moved using pumps as the battery charges or discharges. That makes these batteries large, with ESS’s main product sold inside a shipping container.
What they take up in space, they can make up in cost. Lithium-ion batteries for grid-scale storage can cost as much as $350 per kilowatt-hour. But ESS says its battery could cost $200 per kWh or less by 2025.
Crucially, adding storage capacity to cover longer interruptions at a solar or wind plant may not require purchasing an entirely new battery. Flow batteries require only extra electrolyte, which in ESS’s case can cost as little as $20 per kilowatt hour.
And so we have yet another “game-changing” power storage technology, and it feels like in another 10 years I’ll be wondering whatever happened to that.
This used to confuse and frustrate me, back before I started studying politics and economics. Back then, even Republicans had been admitting the need for climate action, and I kept being told that the only real obstacle to renewable energy was the “inconsistency”, and the lack of affordable power storage.
I’m still frustrated, but I’m less confused. I honestly don’t know how viable any of these technologies are. Various people who are better than me at math have made various claims about this stuff, and I don’t have ability to parse those directly. The one thing that everyone who cares about climate change seems to agree on is that we already have the technology to make the changes needed, what we lack is the political will. For some, that’s about renewable energy, for some it’s about nuclear, and for most, I think, it’s about a combination of the two.
Are these iron-flow batteries enough to make the transition away from fossil fuels easy? No. Because lack of storage technology has never been the primary obstacle to that transition. Would they be useful if we actually went all-in on dealing with climate change? I don’t know, but trying does seem to be the best way to find out. The same is true of the gravel/thermal system, and the distributed car-based system. It’s even an area in which some level of competition could yield good results for humanity, but despite what neoliberals might tell you, that competition is being blocked by capitalists, not by “the government”.
I guess the point of this post is this: We have tools to deal with climate change that we are currently not using. We are also constantly developing new tools that also don’t get used. We need to organize, to train, and to take power out of the hands of oligarchs and their ilk. Only then will we be able to use the collective might of humanity for the benefit and survival of humanity.
All we have is us, but if we work together, that should be plenty.
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