Pete C wrote in message . ..
On 30 Apr 2004 05:52:31 -0700, (N. Thornton) wrote:
"Rick Dipper" wrote in message
...
Some info about heat pumps:
Electrically powered compression type pumps can do 3x to 4x heat
transfer, but this is a max figure, and drops as outdoor temp falls.
Thats the gotcha.
Hi,
There are ones available in Japan that have a heat transfer of around
6 or above:
Toshiba:
http://www.excite.co.jp/world/english/web/body?wb_url=http%3A%2F%2Fwww.daiseikai.com%2Findex _j2.htm&wb_lp=JAEN&wb_dis=2
http://www.excite.co.jp/world/english/web/body/?wb_url=http://www.daiseikai.com/eco/index_j.htm&wb_lp=JAEN
Hitachi:
http://www.excite.co.jp/world/english/web/body?wb_url=http%3A%2F%2Fkadenfan.hitachi.co.jp%2F ra%2Faircon%2Fproducts%2Frase22s.htm&wb_lp=JAEN&wb _dis=2
Daikin:
http://www.excite.co.jp/world/english/web/body?wb_url=http%3A%2F%2Fec.daikinaircon.com%3A809 0%2Fecatalog%2FDKCA001%2Findex.html&wb_lp=JAEN&wb_ dis=2
Mistubishi:
http://www.mhi.co.jp/aircon/cs/products/home/catalog/04srac_a_1/pdf/p007.pdf
Although they are less efficient towards 0°C, they are more efficient
in milder weather and when run at less than the rated capacity, so it
evens out more.
The capital cost of a ground source heat pump is horrendous. The payback
period is looooooooong.
Good refs there.
Air source is way cheaper, and sounds diyable. Does someone here know
more about it?
The biggie for air source is that when the temperature drops to 0°C
frost can form on the evaporator outdoors, which needs to be thawed
off and reduces efficiency.
Has anyone tried mechanical frost removal? Would seem far more energy
efficient.
Also solar reflectors pointed to the cold element would reduce this at
least a bit, and presumably help with efficiency. Cant say I've tried
any of this though. Solar space heating is cheaper and pays back ok.
It might be possible to have a semi-ground loop. Air would be used
when it's temperature is above 0, and the ground loop at other times.
A smaller pipe in the earth or large pond could be used as the ground
loop.
Also when the air temperature is above that of the ground loop, the
ground loop could be warmed using the air. This could all be done with
a normal outdoor unit with a small pump to circulate liquid warmed by
the ground loop over the coils when required. The liquid could be
distilled water maybe with some potable antifreeze.
extra complication, extra cost, thats the problem.
Regards, NT