If you have never heard of Atmos clocks I wouldn’t be surprised… they are amazing… but expensive (cheapest one is about $5000). The clock pictured above is an 80th anniversary unit. The Atmos clocks run, in theory, forever with no batteries, solar bits, or electricity…. they are powered by temperature fluctuations. There is a mixture of gas and liquid ethyl chloride that expands and contracts when the temperature goes up/down. Each degree of (Celsius) change equals two days of free energy. Many details here.