"With solar wind sources to run pumps and fans it become a little closer to Zero Emission. The cooling side has to be miserable unless you add fans to circulate air within the conditioned space, and without some form of evaporator in more humid regions it will feel like you are living in a cave. Payback? Even though I would like to be removed from the fossil fuel accounts, the payback for this thing 1. isn't in my payback period, and 2. its useful life isn't even within the payback period. "