The Importance of Thermal Storage in the Expansion of Renewable Energy

It's now well established that to mitigate the worst effects of climate change, we need to get to net zero carbon emissions as quickly as possible, which means getting more of our energy from renewable sources and finding ways to store energy for long periods of time to overcome the intermittency of wind and solar.

Giant battery farms and green hydrogen (using surplus renewable energy to split water) are often touted as the most promising storage solutions, and clever new ways to store excess electricity are emerging all the time (see “Giant CO2-filled domes could store surplus renewable power”), but the potential to store renewable energy as heat is often overlooked.

When we think of renewable energy, we tend to think of electricity. But heat is also a valuable commodity in its own right. About half of the world's total energy demand is for heat, whether it's to heat our homes or to power industrial production of food, medicines and materials. What's more, stored heat can be used to generate electricity when the sun stops shining and the wind dies down.

The good news is that, as we outlined in our feature “How Incredibly Simple Technologies Can Accelerate the Race to Net Zero”, a range of thermal storage technologies are emerging. Collectively known as thermal energy storage (TES), many of these innovations are incredibly simple, from baked bricks to molten salt. Crucially, they're affordable: early estimates suggest that these technologies could be as little as one-fifth the cost per kilowatt-hour of energy storage using green hydrogen. In a recent report, the International Renewable Energy Agency said TES offers “unique advantages”.

The problem is that awareness of TES is relatively low, and investment even less. Private backers are starting to pour big dollars into pilot projects in the US and Europe. But for TES to live up to its promise as a relatively easy way to make a big impact on the problem of renewable intermittency, governments will need to step up. And if the price is as reasonable as it appears, there's no reason not to.