Beyond Batteries: Imaginative Alternatives for Grid Energy Storage

Solar and wind power are "intermittent," points out Slashdot reader silverjacket . "A feature in this week's issue of The New Yorker highlights current efforts to use gravity, heat, momentum, air pressure, and other methods to store large amounts of energy for the electricity grid." In other words, alternatives to massive lithium-ion batteries:Quidnet [has] patented a new kind of pumped hydro. Instead of pumping water uphill, the company's system sends it underground through a pipe reaching at least a thousand feet down. Later, the system lets the Earth squeeze the water back up under pressure, using it to drive generators. Wright and Craig are veterans of the oil and gas industry, and Quidnet's technology is like a green riff on fracking.... Initially, Quidnet encountered skepticism about its ability to form lenses of the right size and shape. By the time I visited, however, it had successfully completed multiple pumping cycles in Texas, Ohio, and Alberta. The company has received thirty-eight million dollars in private and government funding, including contributions from Breakthrough Energy Ventures, established by Bill Gates. The New Yorker science/technology writer also interviewed Bill Gross, a longtime investor in solar power and a co-founder of his own energy-storage company called Energy Vault. He points an inconvenient truth: "it actually costs more to store electricity than to make it." In many cases, solar and wind have become less expensive than coal and gas. But add the cost of storage, and renewables can lose to fossil fuels. But he's working on his own solution...Energy Vault's first attempt at a system was EV1, a looming, Transformer-like tower crane with six arms. The idea was that such a crane would stack blocks in a wall around itself, then unstack them.... [T]he company moved on to a new, enclosed design, called EVx. In renderings, it resembles a boxy automated warehouse forty stories tall. Elevators will use clean power to lift blocks weighing as much as thirty tons and put them on trolleys, which will move them toward the middle of the structure. When energy is needed, the blocks will be moved back to the elevators. As they descend, the elevators will power generators, producing new electricity... The EVx demo is being developed in a bucolic Swiss mountain valley in the shadow of EV1... [T]he company isn't alone in pursuing what's known as "gravity storage." Gravitricity, based in Scotland, recently concluded a demonstration that involved hefting a fifty-ton block up a tower, two stories at a time; it now plans to raise and lower single, thousand-ton blocks inside disused mine shafts. Two other companies, Gravity Power, in California, and Gravity Storage GmbH, in Hamburg, aim to place a massive weight at the bottom of a shaft and then pump water underneath to lift it. To withdraw energy, they'll let the weight push the water down into a pipe and through a turbine. RheEnergise, based in Montreal, has come up with yet another take on pumped hydro, centered on a fluid that the company invented called R-19, which is two and a half times as dense as water; its system will move the fluid between tanks at the top and bottom of an incline. The work is still at the crowdfunding stage. Just as you can store potential energy by lifting a block in the air, you can store it thermally, by heating things up. Companies are banking heat in molten salt, volcanic rocks, and other materials. Giant batteries, based on renewable chemical processes, are also workable. In so-called flow batteries, tanks can be used to manage electrolytes, which hold a charge. In hydrogen storage, electrolysis is used to separate hydrogen from oxygen in water; the hydrogen is then cached underground, or in aboveground tanks, as gas or liquid or part of ammonia. When it's recombined with oxygen in a fuel cell, it forms water again and releases electricity. The article's last line? "Nature can help us generate power. Maybe it can help us hold on to it, too."

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