as for capturing the waste heat into the electricity this is a bit difficult due to the ‘low grade’ heat miners produce and the fact that heat to electrical energy conversion is less efficient at lower temperatures. But I’ve given this considerable though. There are basically two ways
1.) using TEC’s (thermo-electric cooler) which are a solid state device, normally used for cooling, but can also generate electricity if you put the cold side on the heat source, and sink the heat out of the hot side. But these are ~5% efficient at best so you’d have to have a way to get a good temperature detla across it, maybe with liquid cooling and having the TEC’s between the ASIC chips and the heat sink whether air cooled or liquid.
2.) using and ORC (organic rankine cycle) this one is not as easy and requires special equipment and possibly a custom designed solution. An ORC is basically a steam engine except the fluid inside Isn’t water and is something with a boiling point around 80C. Based on my research these could convert low grade waste heat to electricity, by using the expanding gas to drive a turbine, with about %35 efficiency.