But an air-to-water heat pump does different things. More popular in Europe than in the US, these types of heat pumps are built, as the name implies, to warm up water.

A prototype based on the model, the study said, promises “5.826 liters” of water per day, but admits “this comes at a substantial energy,“ and suggested using “high-density waste heat ...

The compressor and generator systems live close by on dry land, and when there's excess energy to be soaked up, the compressor feeds ambient air down to these tanks through long hoses at 20-70 bar ...