Dear Geoff: You win the hand-painted pot. Chamber that is. Accumulator is the word New Scientist used, but far more UK links used lead-acid battery. As for gas powered refrigerators, the refrigerator in medical lab I worked in while in the Philippines was a Servel, running I think on natural gas. They had tubing on rear just like conventional refrigerator. I thought they were just a different type of heat pump.It was very satisfactory despite high temperatures - much of the time in high eighties and nineties.. I guess that there just wasn't enough demand for them to compete in US, though I wonder if some mobile homes might not still have them. While in Manila, I used to see big bomber circling overhead for sole purpose of making ice for the officers' messes. That must have cost taxpayers a bundle.