A coincidence that two days after Britain experiences the highest temperature since records began Nick from HVAC UK Ltd installed the Fujitsu inverter supplied by Orion Air Conditioning. This project has been underway, off and on, since 2009 and was mooted 5 years before that in the CarbonFree report Watts in Store – Storing Renewable Energy. Now we are at stage three, linking the passive solar chimney with a heat pump. The next stage, once all the remaining ducting has been installed will be storing excess heat under ground in the summer and retrieving it during the winter.