Dave Liquorice wrote:
On Thu, 16 Jul 2009 13:11:42 +0100, dennis@home wrote:

If this is from a river, how fast does it flow, is there a fall across
the land?

It might be better to put a turbine in, generate electricity and use
that.

An idea, but to get a few 10's of kW of electricity you need a good
head and a hefty flow. IIRC 3kW of lecky needs a 20m head and 20l/sec
flow, if that is available it could drive the heatpump of course...

There is absolutely no doubt that in terms of energy input versus useful
house heating out, a heatpump is the no. 1 technology.

The only problems are cost of installation and the heat exchanger.

And of course where the energy comes from, BUT with a heat pump in a
typical situation providing about 3:1 uplift in terms of heat output to
electrical input, it means that even a 30% efficient power station
matches a 90% efficient boiler.

If the electricity is at least partially carbon free (nuclear) then its
also a huge carbon reducer.

Likewise, with UFH in winter, you can use off peak electricity when the
outside temps are coldest, to get the house up to temperature - a
temperature it may well keep (if well insulated and reasonably massive)
for the whole day.

I would 100% use it in a new build, if adequate land area or pond volume
is available, but its a bitch to retrofit. Air source might work in a
small flat installation in urban environments where temperatures are
constantly high because of heat leakage from buildings, but its crap in
rural locations.