The issue is user friendlyness, vaccum tubes dont lose heat quickly
so the system would be useable in the dead of winter without requiring
the use of cumbersome manual bypass systems or expensive and failure
prone automatic ones. Unlike normal vaccum systems it wouldnt require
an expensive tank and the efficiency would actually be higher than
normal vaccum systems since the delta T is lower. The actual
delivered BTU should be more than enough to justfiy the cost,
especially when account for the fact that the pumps and control
equipment are already included in the cost of the geothermal
Without the tank that means the only addition cost would be the array
itself. That means I get the same square footage of array with the
advantages of the vaccum tubes at the same price that a flat panel
would cost when you account for the more complicated installation and
the addition of a thermostat and fan system.
While I would have to cover the system during the summer, the
transition here is Ohio is slow enough to make that easy.