[Mobile Master Tech]

I have always been bothered by the fact that many alternative energy sources, especially solar thermal, have the least output when you need it most. Most solar and process heat recovery systems have innovative and elaborate systems to throw away surplus heat that can't be used or stored when it is generated. Even large storage tanks, such as the one I describe in the solar storage tank thread, can't store a large amount of heat or for a long time. Phase change materials help, but have drawbacks (including $$$!). The problem is the sheer number of BTU's and how much deltaT there is between storage and environment. Concentrate the heat in one place at high enough of a temp to make the storage size feasible, and most of it has leaked out by the time you need it, plus you lose tons of efficiency getting it to that high of a temperature.

I have been inspired to design a cost-effective way of getting that heat back after researching the work of Don Stephens, who pioneered Passive Annualized Heat Storage (PAHS) back in the 80's, as well as John Hait and others.

My plan is to drill "reverse geothermal ground loops" under my basement slab to "inject" waste heat into the soil below the house, eventually raising all of the soil from its' natural 62F (in northern Georgia) to 70-73F, plus a hotter center section whose greater heat diffuses to the surface around 6 months after going in. Sources differ about exactly how far the heat diffuses in six months, but the lowest I have seen is 9ft, and AC Hacker seems to have found a source saying it is 16 ft. I have done the math from government logs detailing the time lag of underground temperature peaks at various depths compared to the peaks at other depths as well as aboveground temperature peaks. I came up with 10-11ft per 6 months for most soil types. This backs up what I gleaned while researching PAHS.

More info to come, but I wanted to get the ball rolling and get others in the dialogue! Google the Drake Landing Solar Community in Canada, as well as PAHS, ground heat storage, etc.

Craig
The MMT