Most of my readers are aware that photovoltaic (PV) and wind turbine electric generation are (1) the most popular renewables and (2) intermittent. Although energy storage can be used to mitigate their intermittency, it would be better if they were not intermittent. Actually, there are two renewables that can be dispatched, these are still at least somewhat intermittent: small hydro and geothermal. The former is generally run-of-the-river (no reservoir) and thus dependent on stream-flow, and the latter is dependent on the amount of underground heat. Large hydro is not considered a renewable (mainly because of the large cost and secondary environmental impacts of building a large dam and the reservoir), but is considered “zero-greenhouse gas (GHG). There is one other zero-GHG electric generation technology, and from the above title, you can probably guess what that is, and that this is the subject of this post.