grk more expensive than nuclear, page-37

Tawny,

Just being the devils advocate here and pointing out that it is much easier to create surface area with hotter rocks and surface area is what is required.

You quote:

"the concept of the underground heat exchanger is fairly static between projects. All operations (except PTR) will be stimulating the natural jointings and fractures in the granite. Then a large reservoir must be established to ensure adequate surface area for heat exchange, and increase flow rates."

Agreed, but the hotter the rocks the easier to fracture, thereby giving more surface area, which is the most important component of this technology as you state.

See my following example;

1 rock @ 3km^3 = Surface area of 14km^2

Crack same rock with 10 vertical cracks giving 10 = sized rocks, now surface area = 23km^2

Crack above 10 pieces with 10 horizontal cracks, now you have 100 = sized rocks, now surface area is 140km^2.

Although by making smaller rocks, stored energy (heat) will dissipate faster from these rocks, so there are some trade offs, but the net effect of creating more stored energy is far greater by cracking the one large rock.

Without real testing and or going into complex mathematical equations it is difficult to define exactly the "crackability" of individual rocks. Crackability will be assisted by the greater numbers of fissures in the rocks.

Roo