More serious than «flash burns» or thermal contact burns, electrical burns can cause permanent internal injuries. (peter-thompson-associates.com)
Air is light in weight and low in heat capacity, so a lot of air needs to be passed through an air heating collector, and it has to be done in a way that puts a lot of the air in good thermal contact with the absorber. (builditsolar.com)
There is a low temperature reservoir available (outer space), but the problem, or so it seems to me, is that our thermal contact with it is poor, being essentially limited to radiation from the upper atmosphere. (realclimate.org)