Stirling engines like ours can go at cryogenic temperatures too :) They are used to reliquify natural gas at LNG terminals, but we decided to focus on industria

Stirling engines like ours can go at cryogenic temperatures too :) They are used to reliquify natural gas at LNG terminals, but we decided to focus on industrial heat for now. You are correct. In our case, we can go from ambient air to the desired process temperature, but the coefficient of performance will be much better if we have access to a waste heat source (the higher temperature the better).