Decarbonizing with a box of hot bricks

Big chemical plants run on heat conveyed by steam, and they run 24 h a day. Most of them operate with the greatest efficiency when they are cranking for months on end without pause. They don’t like to be turned on and off—or even turned up and down.The output of renewable energy from wind turbines and solar panels, by contrast, swings wildly over the course of a day and is literally as changeable as the weather. That divide is a big part of why the chemical industry’s greenhouse gas emissions are among the hardest to abate. Even as solar and wind become, on average, the cheapest electrons on the grid, the price and availability of the power is too volatile for chemical makers. And, especially in the US, natural gas is still cheaper than electricity as a way to generate heat. So most chemical plants power their boilers with gas or other steady and reliable petroleum sources.Thermal batteries offer a way to stockpile renewable energy when it’s cheap and use it later. And because they store that energy as heat—which chemical plants and many other industrial facilities need—thermal batteries can beat lithium-ion batteries and other means of energy storage intended to decarbonize heavy industry. The first few installations are running now, and the industry seems poised to expand if the results—and the cost savings—live up to the promise.The concept of thermal batteries is straightforward: they’re giant, well-insulated toasters filled with bricks. Electricity carries energy to resistive heating elements when renewables