Challenger-
I don't think there's an issue with molds in a geothermal system. I don't know a lot about them, but I think they use a heat exchanger with the fluid that's cooled/heated in the ground which then exchanges with your house system.
there's a good article in the feb. issue of Journal of Light Construction. (tried to get a link to it on the web, but I think you have to pay to download it, or find a copy at the library)
back to fuel:
went to a trade show last week and listened to Steven Amendola, a chemist discuss how to use waste heat energy of power plants (something like 60% of a natural gas plant's energy is given off in waste heat in the stacks!) to make hydrogen and recombine that & other waste gases (ammonia) into urea, which is a harmless, stable solid that he says has the potential fuel energy of gasoline.
He's already made a fuel cell vehicle with borax -
http://www.sciam.com/article.cfm?art...A8809EC588EEDF
(I don't know if this link will work but you can search his name)
anyway - it's exciting to know the technology and ideas are coming together - now we just have to get the corporations to build the infrastructure: $$$$$$$. how much will it cost to convert a coal or gas plant into recapturing waste energy & gases (and reducing atmoshperic pollution) and producing additional fuel sources??
it took the gas crisis of the 70's to get car manufacturers to start considering mpg. maybe if gas goes up to $80/barrel the hybrids will get ALOT more popular - and there will be a renewed push for other energy ideas - aside from, lets just dig somewhere else for more oil.