Germany is a renewable energy powerhouse. In the past years, they've been breaking all kinds of records, and while others are now bigger drivers of clean energy adoption (China, U.S.), the country still has a huge installed base of wind and solar power. The challenge is now to better integrate these intermittent sources of power with the rest of the grid. Intermittent doesn't mean entirely unpredictable (it's possible to have fairly sophisticated wind and solar radiation forecasts a few hours in advance), but it does mean that they can't be controlled directly at will.
That's where molten lakes of aluminum, among other things, come in...
Smelting aluminum takes a lot of electricity. Trimet Aluminium SE, Germany’s largest producer of the metal, uses about 14 megawatt-hours per ton produced, or the equivalent of about 500 euros at the price that they're paying for electricity. They produce 500,000 tons last year, so that's about 7 million megawatt-hours!
What if we could use Trimet's molten aluminum lakes as a kind of virtual battery to help absorb supply volatility from the grid? That's exactly what is happening:
By varying the rate at which the metal is produced, the plant will be able to adjust the power consumption of the 290-megawatt smelter up and down by about 25 percent. Trimet can soak power from the grid when energy is cheap. It can then resell the power when demand is at its peak. The company can temporarily reduce its power consumption by slowing the electrolysis, cutting the energy drain.
It's the same principle as other demand response projects that are enabled by smart grids. Add a lot of them together, like by varying the temperature in water heaters or refrigerated warehouses by a few degrees to absorb extra energy or free some up when there's a shortage, and you get significant control over how much demand there is on the grid, making it easier to match supply.
Trimet things that eventually it will be able to store the aluminum equivalent of 3,360 megawatt-hours of energy over a two day period, with energy conversion at around 90%. That's the equivalent required to power more than 300,000 homes for a day, so it's not an insignificant amount, especially for a single company.