We all know that the future of energy is in renewables. They were the world's cheapest source of power in 2020. This is very good news. But we've got just a small problem. How do we store all of it? It's not sunny all the time, nor is it windy 24-7, so we need a way to keep reserves. "We need better batteries, that's for sure." So far, the dominant battery solution for renewables has been the lithium-ion. But mining pollutes, exploits people, and the batteries have a habit of blowing up. They don't last long enough, and we're going to need a lot more capacity. So what are our options? Enter: Salt, water, gravity, really hot air, really cold air and enormous piles of sand. Sounds like a field day at kindergarten, but could these things
actually solve our energy storage problem? Before we get into the shiny new stuff, we've got to talk about the lithium-ion battery. It's the fastest-growing battery segment in the world. Scientists started developing it during the oil crisis of the 1970s. They hoped this could wean the West off fossil fuels. If this sounds vaguely familiar, it's because nothing has changed. But it took a while until you could actually buy one. Engineers Stanley Whittingham, Akria Yoshino and John B. Goodenough helped develop the first commercially available lithium-ion batteries that came to market in 1991. That's them winning the Nobel prize for that. "You work with nice people, and they do all the hard work, and you sit back and try to take as much credit as you can! Hahaha!" The lithium-ion battery is good at giving a lot of electricity in shorter bursts, so we've depended on it for consumer electronics and now electric cars. And it's also pretty much the only battery we use for storing grid-scale renewable energy. But mining lithium is problematic. The extraction process involves pumping underground water deposits to the surface. This uses roughly 70,000 liters to make one ton of lithium. More than half the earth's resources are between Argentina, Bolivia and Chile. Mining it consumes 65% of the region's already scarce water supply. Lithium-ion batteries also typically use cobalt, which is expensive and mined mostly in the Democratic Republic of Congo. News reports have covered the notoriously exploitative business, which uses child miners and devastates local communities. Lithium batteries can be flammable. If you can't bring them on a plane, you should definitely think twice about a giant one backing up your grid. And they lose capacity, so longevity really isn't their forte. So lithium-ion batteries work, but they can't be the only solution to store energy, especially on a grid scale. According to the IEA, we're going to need close to 10,000 gigawatt-hours of energy storage worldwide by 2040 to meet climate goals. That's 50 times the size of the current market. Today, it's actually another technology, pumped hydro storage, that comprises a whopping 96% of global storage power capacity. "It basically relies on pretty simple gravitational principles." This is Ramya Swaminathan. She's actually the head of a thermal storage company, which we'll get to later, but she has absolutely no problem with water. "You've got two reservoirs, or lakes, one high and one low, and when you have a lot of excess power, you use that excess power to pump the water uphill to the higher reservoir. When you want that power back, you let that water run downstream and turn a turbine generator. However, those projects are hard to build." These reservoirs take up massive amounts of space, and you need exactly the right geography: two lakes and a hill. A lot of them also work within conventional hydroelectric dams, which require lots of upfront capital and disrupt habitat. Storing renewable energy is going to need a lot more flexibility and modularity than these reservoirs. One promising alternative that's making headway comes from something you can find right on your kitchen table: Salt. "Sodium is much more abundant, and it's chemically similar to lithium. It's in the same group in the periodic table." This is Rosa Palacin. She's a battery researcher at the Institute of Materials Science in Barcelona. She says it's the most straightforward alternative because it basically mimics lithium-ion battery technology. Sodium has also got one valence electron - the number of electrons in the outermost layer. But sodium is a thousand times more abundant, is 20-40% cheaper, and isn't sensitive to temperature changes. So, no issues with blowing up. But it does have lower energy density, thus, heavier batteries, which is why it hasn't commercialized sooner. If it's for the grid though, this won't matter so much since everything is stationary. And right now, time is of the essence. "The sodium-ion is way higher in technology readiness level, so much closer to commercialization." While they're already on the market, analysts expect them to be produced at scale in the next few years. There's also research happening for calcium, magnesium, and zinc batteries, but for these, "The technology is really at the level of demonstration in the lab." Speaking of salt, what if we could store energy in the form of heat in really, really, really hot salt? That's what Swaminathan's company, Malta, is doing in the US. "We take electric energy, either directly from renewable generation, like wind or solar, or just from the grid, and
we convert that into thermal energy." Turns out that molten salt is a great preserver of heat. It looks kind of like water, and has roughly the same viscosity. Here's how it works: When there's excess electricity generated, the energy is used to heat a large, insulated storage tank of molten salt at very high temperatures. A high melting point means the salt can absorb a lot of energy. It loses little of that heat, and can keep it for 6+ hours. In comparison, lithium batteries can only manage under four hours. When the grid needs power, the plant reconverts heat back into electricity through a turbine. One of these plants would provide enough for a large town, for at least 10 hours. Malta's first commercial plant won't debut until 2025. While its material costs are relatively low and its system is pretty scalable, its efficiency still lags behind hydro and lithium. The hope is that the market will eventually make it feasible. You can do something similar with the piles of sand we mentioned earlier. A couple of Finnish guys decided to use some local piles to solve one of Finland's biggest energy issues: heating. Instead of converting the heat back into electricity, they just use it directly. "The storage capacity is in the order of 1,000 times cheaper than that of lithium batteries." That's Markku Ylönen. He co-founded a company that makes sand batteries. "We turn the electricity to heat. We can make it so cheaply that we can play with large volumes of energy." How much sand? "100 tons of sand." It can store heat at around 500-600°C for months. This heat then goes directly to warm municipal buildings. Most importantly, it could provide heat to the heavy industry sector, which is one of the biggest emitters of greenhouse gases. In cold countries, this solution makes a lot of sense. The company currently has one system that's heating Kankaanpää, a southwestern town with a population of 13,000. The 100-ton sand battery can technically stay hot for months, but they recharge this one in 2-week cycles to keep it efficient. The company is also trying to source sand that isn't used in the construction industry, since that's also scarce, and are aiming to make larger batteries. Let's keep in mind that these are just a couple of solutions. There are dozens of technologies out there right now, each vying for their place in the market. Flow redox batteries, for instance, are another big contender for grid-scale storage. They don't function all that differently from lithium-ion. In the latter, electrons travel between two electrodes through a liquid called an electrolyte, creating a current. In a flow battery, this liquid electrolyte is stored externally. The larger the tank, the more storage capacity, which means the flow battery can be scaled really easily. And what needs scale? You guessed it: the grid. So far, flow batteries made with the metal vanadium has been the most advanced ones out there, although there's also development in iron, bromine and sodium. Vanadium's advantage is that it's basically immortal. It can be cycled over and over without degrading. A battery can last about 30 years, but that's only because you'd have to replace the pipes and tanks. You can take the vanadium out and reuse it in a new one. "Chemical technologies, gravity-based technologies, mechanical technologies, flow batteries - all that stuff - this is a huge need that we're trying to solve. And I think we're going to need all of it." Each technology has advantages and drawbacks, so they have to find their specific application. Investment has been concentrated in new battery technologies, driven by the electric vehicle market. The global grid-scale market is expected to grow by 25% annually until 2027. And of those, redox flow seems to have the most promise. They're just not quite commercially mature yet. Truth is, we're not going to quit the lithium-ion anytime soon. The huge demand for electric cars means that some of the technologies and efficiencies in development there will spillover to the grid. But the fossil fuel industry is built into the economy. It's a huge challenge to adapt entire systems, including infrastructure and policy, to renewable alternatives. The good news? Investment is there. Spending on grid-scale batteries rose more than 60% in 2020. And at the end of the day, cost is the biggest factor limiting adoption of new technology. It'll be the market that dictates how far they've come, and how far they'll go. Did you know that even stones can be used as energy storage? Turns out nature has all sorts of solutions for us. We just have to figure out how to use them properly. If you like this video, don’t forget to subscribe and hit ‘like.’ See you next time.
