Dave Liquorice wrote:
On Fri, 29 Feb 2008 21:16:33 +0000, Andy Champ wrote:

Doesn't it get a bit less efficient (possibly 0%!) when you're pumping
water at 47.5 into a panel on the roof?

The losses are higher but you still get the same delta T (more or less).

Assuming the energy input to the panel and the flow through is constant
then it doesn't matter what the inlet temp of the flow is. The water still
collects the energy and thus the same delta T. True, the whole thing gets
hotter so losses rise which ultimately limit the maximum temp that a given
energy input can acheive.


On a day like today, which is probably a fairly average day - bright but
not much sun, temp. about 10 - what's the equilibrium temperature of the
panel?

Mary,

The PV pump will only mean I don't waste electricity running the pump.
It won't help if the panel is doing no heating.

Andy