Wrenching in L.A. [RE-wrenches]

[Todd Cory, Mt. Shasta Energy Services]

William,

Most solar thermal systems around here (where it freezes) are closed (glycol)
loop, so by their very nature (the pump pushes and pulls at the same time) the
circulation pump's energy requirements are very low. Most people spend a bit
more and use a DC pump and small PV next to the thermal panels, so that
eliminates the need for grid power for the pump and a differential controller.
The other type of system that works well in freezing weather is the drain back
style. This design uses much more power as the water circulation loop is open
to the air, but it does not use glycol so efficiency is slightly better.

Hope that helps,

Todd


William Miller wrote:

> Graham:
>
> How about the cost of electricity to pump water to a rooftop panel?  I know
> little about water systems, but that won't stop me from showing my
> ignorance!

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