Scholarship on the energy transition has given a good deal of attention to battery storage, because it can help make variable renewables more dispatchable over longer periods of time, and because it’s a core part of electric vehicles. Numerous models have projected that we’ll need a very large amount of battery storage starting several decades from now, when renewables approach 80% of grid power supply, meaning long-duration and seasonal storage will become more necessary. But what if that isn’t true? Many of those models assume that heating, ventilation and air conditioning (HVAC) loads, which account for about half of total power demand, will need to be met by electricity stored in batteries. But what if we could provide heat directly, by saving or recovering waste heat, and then using it as heat, without going through the conversions (and energy losses) of converting heat to electricity and then back to heat? What if using waste heat and other low-temperature sources were actually a far more efficient way to meet those demands? In this episode, we discuss thermal storage for the first time on this show, to understand the state of the art and its potential, as well as where much more research on thermal storage is needed. Our guest is Daniel Møller Sneum, a postdoctoral researcher from Technical University of Denmark, an expert on thermal and district energy who wrote his PhD about flexible district energy systems. We’ll only scratch the surface of the thermal storage topic in this episode, but we hope that it helps our listeners begin to learn about this important and badly under-studied sector.