Why aren't heat pumps placed indoors ? The big unit that is installed
outside, I mean.
Could you do something where the heat pump could be placed in a stall
(or in the garage) attached to the house. In the winter, close the
outside stall door and open it up to the house, so the heat pump is
inside the house. The pump would then pull already-warmed air from
inside the house. All the heat generated would stay in the house.
In the summer, change it around so the pump is outside, since it
creates heat that needs to be release outdoors.
What am I missing ?
<snip>What am I missing ?
The first law of thermodynamics for one thing:
You can't take air, remove heat energy from it, add the same energy
back to the same volume of air (after loosing some due to
inefficiencies), and expect to have warmer air. It's true, you are
adding energy to the system by using electricity, but it's still not
going to be a net gain until the backup heat kicks on - and, if you're
going to do that, you might as well scrap the heat pump and just use
the backup as your primary heat source.
The space would eventually heat up without the backup, very slowly,
but it would heat up. No change in tempeature that would imply a
perfect, lossless system. If there were a drop in temperature then
that would mean that energy was being destroyed.
True, but only because the energy lost due to electrical and mechanical
inefficiencies will be lost mostly in the form of heat, so in that way,
I guess it would gradually heat the house. However, if you wanted to
heat the house with electrical resistance, it would be a lot cheaper
just to install electric heaters instead of using the motor windings as
You are missing the same reason the A/C cycle has to be outside.
Expecting the unit to produce more heat by using the heat it already
produced is the classic over-unity problem. It can't be done.
Heat pumps basically MOVE heat from onew location to another. In the
winter they gather what they can of heat in the cold and move it
indoors. aboiut 30 degrees they become ineffective and turn on
resistance heat, thats really expensive.
in the summer they take heat out of the indoors, and move it outside.
sadly theres no free lunch:(
This is a region specific temperature. Different parts ofthe country
have WILDLY different ground water temps. Some areas around the Great
Lakes have winter temps that hover very near freezing, while regions
along the Gulf Coast have year round water temps of 75 degrees.
Generalizations are DANGEROUS.
And yes, GSHPs are located indoors.
Modern systems are designed to be efficient. The sealed motor/compressor is
insulated. The electrical energy is converted to work used to compress the
working fluid (freon or whatever) which heats it and heat which also heats
the gas. In winter the gas goes into your house where it is cooled by the
air of your house causing it to and condense to a liquid, the liquid flows
to the evaporator outside where it expands into the lower pressure in the
evaporator forming a gas. This cools the outside air. Little would be
gained by putting the system inside.
Modern heat pumps can deliver 2 to 2.5 times as much heat as electrical
energy to run them using a seasonal efficiency rating. I believe less than
1/3 of the energy of combustion in an electrical power plant makes to your
home. Thus a 90% efficient gas furnace will use less net energy. The
colder the climate the better for the gas furnace. The most efficient
heating is to use cogeneration where you have your own electrical generator
running a heat pump and also waste heat to heat your building.
For those interested in what science tells us about this--
Thermodynamics tells us that efficiency of a heat engine is the (high
temperature-low temperature) divided by the high temperature. You need to
use a temperature scale where zero equals absolute zero. Assume your inside
condenser is at 100F (310 Kelvin) and outside is 32F (273 Kelvin) then
efficiency is (310-273)/273 or about 13%. This means that a heat engine can
only convert 13% of the heat energy to work operating at these temperatures.
But a heat pump is the opposite so an ideal heat pump could pump (100%/13%)
or over 7 times as much heat as work (electrical energy consumed).
Unfortunately we can't come anywhere near this number or we would all use
heat pumps to heat our homes.
The above equation shows why we want to operate systems that convert heat to
work at as high a temperature as possible to have the most efficiency. This
why a diesel engine is more efficient than a gasoline engine.
heh... this is something that i had been thinking about.
I've been looking for an efficient cogen gas appliance for the house,
but when i got the grid tie requirements, it kinda went out the
So, I'm thinking to myself: What if i just converted the electrical
output into heat, and treated the thing as emergency generator and
boiler for domestic hot water and heating. It would get most of it's
use in the winter, of course. I hadn't thought of using a heat pump
since we have hydronic heat. (although I suppose they make heat pumps
that use a liquid exchange instead of air...)
May no harm befall you,
Ich habe keine Ahnung was das bedeutet, oder vielleicht doch?
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