On Sat, 4 Sep 2004 10:27:12 +0100, "IMM" wrote:


"Pete C" wrote in message
.. .
On Thu, 2 Sep 2004 21:56:59 +0100, "IMM" wrote:

In winter a heat pump may not be able to produce enough hot water at high
enough temperatures.

The alternatives a

* large solar panels storing water in
a large thermal store using very low
temp underfloor heating.

* Windpower, again using a thermal store and UFH.

You may find that either of the above may
come in cheaper than the heat pump.

CO2 heat pumps are coming available that do a good job of generating
hot water for DHW.

Expensive at the mo'. A full solar south facing roof (easier on a new
build), would be very effective. Simply as you have a very large area of
solar collector a lot of heat can be gained for the cost of running a pump.
Also the cost of converting, or building new, a full integrated solar roof
is not as much as you might think. Depending on the work done, etc, about
the same, or less than installing a heat pump. A heat pump still needs a
heating system, DHW, etc, etc, just like all the others. A wind genny, if
you can have one, is very effective. Just have a large thermal store to
store all the heat in water, for when . Then use low temperature UFH.

The best of heat pumps at the mo', in running costs, is the equiv to a
natural gas condensing boiler. A condensing boiler can be had for £500-700.
LPG may even work out cheaper too. As LPG condensing boilers are only
slightly more expensive than NG boilers, doing the figures, it may also be
more appealing than a heat pump. A condensing boiler is very low capital
cost compared to a heat pump. The extra 4-5K spent on a heat pump buys a
lot of LPG. If you are off the gas mains, and they may be run in the
future, then an LPG boiler that can be converted back to ng is the answer.

Hi,

Thinking about it, the best option for the OP if they go for a ground
source heat pump might be to use that to preheat DHW and then use
normal electricity or even Economy7 to heat it further to DHW
temperatures. For showers/baths you might get hot enough water from
the heat pump anyway.

The problem with solar is that in mid winter we average 2hrs/day of
sun, so you would need a huge collector and huge amounts thermal mass
to collect and store enough heat to rely on it alone for general
heating. This could be doable for a new build but would be hard to
retro fit.

However a vacuum tube solar collector could make a useful contribution
to DHW. For a new build it would be worth ensuring the south facing
side of the roof could take the extra weight of a solar collector.

In fact it would be nice if developers were required to make roof
trusses that bit stronger to make it easy to fit a collector, instead
of the usual minimal size.

cheers,
Pete.