"Andrew Gabriel" wrote in message
...
In article ,
"IMM" writes:

BTW, is there a dc version of electric UFH, so roof PV cells can be used
directly on the elements with inverters?

You would be nuts because PV cells are so horribly inefficient.
You would do much better to take the thermal heat from a collector
and use that, with a heat pump if necessary, and a wet UFH system
(possibly the condensor of the heat pump).
I haven't done the calculations, but there may be better sources
to pump heat from that a sunlight collector, which isn't going to
be working all that well just when you need it.

While on PV cells. Alternative, with high capital cost, is a normal wet
UFH
system, fed from a large thermalstore/heat bank. Use roof PV cells to
heat
dc immersion elements in the water store. The thermal store will "store
energy" for use in DHW and UFH.

Again, avoid conversion of sunlight to electricity. Most of
the Sun's energy is lost at that stage. Collect and use the
heat directly.

Best use normal wet solar panels and a large thermal store with "very low"
temp UFH. Thee again a high capital cost. But, using very low temp UFH the
solar panels could heat the UFH on cloudy days.

For a superinsulated house the best is a Mechanical Heat Recovery System,
with the ducts made larger and a use either an electric or coiled wet duct
heater battery. A superinsulated house does not require a full heating
system, so providing heat via a heat/vent duct system makes sense.






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