Alphabet’s X lab spins out molten-salt energy storage project Malta

I'm interested to know what kind of heat pump they are using to get up to molten salt temperatures. The only off-the-shelf high temp heat pumps you can find are generally supercritical CO2. To get a high temperature differential with phase change heat pumps, you typically need to use multiple stages or have a very high compression ratio (read: quite expensive compressor). The picture in the background looks like maybe a ceramic turbine?

Anyone who has any information on this, I'd be interested to hear more about the details.

I like it. Conventional batteries are inefficient for grid level stationary energy storage. Battery packs should stick to their strengths in areas where portability is more important. With the aspect of not having to be moved, molten-salt storage is cheaper and more cost-effective with pretty much zero downsides.

Congratulations to the team that figured out how to build the corrosion resistant materials they're using for storing molten salt. This has been a defining bottleneck for decades now and is a huge accomplishment.

My memories of thermodynamics are old and full of gaps, but from what I remember both steps, if performed at "normal temperatures, necessarily produce a waste of energy. The first step, i.e. using electricity to drive a heat pump, is efficient only if the temperature differential between the cold body and the hot one is small. On the other side, conversion of thermal energy into electricity is efficient only if the temperature differential is large. How does Malta overcome this problem?

I am so curious about this project and really hope for it's success. But heat pumps and PV curves have been studies for centuries. I'm super curious what Alphabet has to offer that is cutting edge. That being said, I really hope they are going to use a Stirling engine to convert the heat back into electricity rather than a turbine. A large scale maintenance free Stirling pump has always been my dream.

How easy would it be to transport temperaturized salt compared to sending electricity through a grid? Or rather, could we use this to generate large amounts of renewable energy in remote but energy dense or low land cost locations and then ship it back to populous areas?