We have just had a modified bitumen roof laid over our 45 square metre south facing extension, and it's a good thickness of bitumen that now thinking about it could have had water pipes buried for solar water heating purposes.
:-(
Would that even have been a sensible idea? Should I get the Tardis time machine out and see if I can get the pipes laid? Console me.
Todays sunshine certainly warmed the roof up a bit!
It could provide a preheated supply for the hot tank in summer, but annual HW spend usually isnt very high, so the saving potential's limited.
NT
On a related note, what happens with such heating during the colder months or on cold nights? Is there some automatic set of valves which shut the roof pipework off below set temperatures, or is this a manual process, or do people not bother and just run water through the pipework year-round (latter sounds like a freezing nightmare!)
PS3, Wii, or Xbox? (it's been one of those days)
You arrange the pipes to drain when the pump isn't running and it doesn't run when the panels are cold. You fill it with antifreeze.
3 methods: Antifreeze & exchanger, drainback or draindown.
On Wed, 18 Mar 2009 18:21:10 -0500 someone who may be Jules wrote this:-
Depends on the design. Properly designed and installed solar panels don't lose a great deal of heat to the air and so the outside temperature is irrelevant to their operation. They work in the Antarctic for example, they also produce useful heat during the winter months in the UK though obviously not as much as in summer. They don't need direct sunlight to do this by the way, indirect sunlight is enough.
If the system is not fitted with antifreeze, freezing tolerant, or draining then most controllers can be set to pump water to the panel when the panel temperature (not the same thing as the air temperature) is near freezing. Obviously this removes heat from the cylinder, but the pump runs for very little time in this mode (a minute or two every hour typically) and so the heat losses are not as severe as some imply/think.
Burying pipes in a flat roof is not a particularly good design due to winter considerations, that sort of system should either have antifreeze to allow it to work in winter without freezing (or use freezing tolerant pipes) or have one of the draining schemes under automatic control (it is generally far better to fit a purpose designed panel, though there may be specific reasons for adopting a low engineering approach).
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