Spain's extreme heat shelters: The Reengineer Monitor #54

Thermoacoustic heat pump, US solar 'rush' - and more!

Photo by Nasa Goddard Space Flight Center. CC BY 2.0.

Merry Christmas, everyone! This is a bumper edition of The Reengineer Monitor partly because it is the last of 2025. But fear not, Monitor will return on 9 January.

Friends, if you’ll allow me, I’d like to begin by highlighting two stories of mine published this week. First, this piece for BBC News on the biggest heat pumps in the world – which are used to power district heating systems. And second, a feature about pumped hydro technology for Wired, including detail about an emerging technology called high-density pumped hydro, which could be easier to deploy than traditional versions of this energy tech.

Heating and cooling

An experimental thermoacoustic heat pump – which uses sound waves to step up heat rather than traditional compressor devices – has reached outputs of 200C, according to scientists in China. “A loud sound in a specially designed tube makes air molecules vibrate, creating pressure changes that move heat from one end to the other. With no moving parts, they are quieter and more durable than conventional systems,” explains PV Magazine.

TechXplore has a good takedown of the various clickbait internet ads for “miracle heaters” and why they won’t heat your home for pennies.