"Bruce L. Bergman" wrote in message
...
On Sun, 15 May 2005 08:50:00 -0400, "ATP*" wrote:
"Steve Smith" wrote in message
...
Bruce L. Bergman wrote:

Should I be looking for a heat pump system?

Definitely - Heat pump is vastly more efficient than electric
resistance heat. Exception being an air-to-air system when it gets
below freezing outside - anything below 25F and the unit is useless,
even if it could get any heat from the air the outside coils would
frost over and never defrost. Then the system has to shift over to
resistance heat or propane.


OK, someone is going to have to explain this one to me. At least two of
you have claimed heat pumps are more efficient than resistance heaters.
I
don' t see how.

Converting electricty to heat through a resistance element is pretty
much
100% in my mind. The only "losses" are due to needing some fans. The
inefficiency of the fans shows up as....heat, so I don't think those
matter. How in the world can a heat pump be more efficient?

They really move heat from the outside air into your house, just like your
refrigerator extracts heat from the refrigerated compartment. see-
http://www.eco-hometec.co.uk/Heatpump.htm

That's a good explanation page. Instead of turning 100KwH of
electricity into resistance heat, you can use 20KwH to move the same
amount of heat inside from the outside.

Where the efficiency of using Propane, Oil, Natural Gas or other
fuels directly for space heating comes in is through the transmission
losses in the electric grid. The average fuel-fired power plant is at
best 50% efficient, and you lose another 10% to 20% in transmission
losses. Meaning the same amount of oil or gas that would get you
100KwH of heat when burned in the furnace at your house is only going
to get you 30KwH after it's converted to electricity and shipped to
your house.

Those losses didn't do you any good - they dumped a lot of waste
heat up the cooling towers at the powerplant, and a lot of waste heat
off every step-up and step-down transformer and each less-than-perfect
splice in the power distribution chain, all of which you can't
harness.

The only reason it is not more efficient to buy the raw fuel, run
your own generator and make your own electricity at home is the
equipment costs and basic economies of scale. Paying for the 70%
losses is usually still cheaper than buying and maintaining your own
set of generators (you need two so you can stop one for maintenance)
and running one of the pair all day every day.

-- Bruce --

Your own set of generators will also be quite a bit less than 50% efficient,
IIRC. Cogeneration can recoup some of that loss by using the heat for
heating or cooling, but even those schemes depend on reducing the peak
demand to make the numbers work. If you're not a demand customer it just
doesn't make sense. In general cogeneration plants have not been a good bet
for small to midsize commercial/municipal entitities, even in downstate NY
with our high electric rates. They've worked out on some big university
campuses, the rest have been abandoned for the most part. Another flop so
far is microgenerators, small turbines that were supposed to decentralize
power distribution.