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Air-source heat pumps typically deliver 1 1/2 to three times more heating energy to a home than the electric energy they consume. This is possible because heat pumps move heat rather than convert it from a fuel (as combustion heating systems do). 
In a typical air-source heat pump, air flows over two refrigerant-filled heat exchangers (known as coils): one indoor and the other outdoor, both of which have metal fins to aid heat transfer. In the heating mode, liquid refrigerant within the outside coil extracts heat from the air and the refrigerant evaporates into a gas. The indoor coil releases heat from the refrigerant as it condenses back into a liquid. A valve near the compressor can change the direction of the refrigerant flow for cooling. 
Heat Pump Technologies
- ISAAC Solar Ice Maker - The ISAAC Solar Icemaker is an Intermittent Solar Ammonia-water Absorption Cycle. The ISAAC uses a parabolic trough solar collector and a compact and efficient design to produce ice with no fuel or electric input, and with no moving parts. (Energy Concepts; 2002)
- Closed Loop Ammonia Turbine - The return of Tesla's solar (and other low heat input) design for home and commercial power systems using inexpensive technology discarded last century due to then cheap oil prices.
- Kokhala: Electricity from Low Temperature Heat & Storage in PCS - Technology harnesses 120+ degrees from a wide variety of sources to generate electricity, for reliable, affordable, clean power for residential, commercial and industrial applications.
- Rauen Environmental Heat Engine - The Superclassical heat engine of Ken Rauen is designed to be able to tap the heat of the environment for energy generation. It is based upon the experimental evidence of the Proell effect, a macroscopic Maxwell’s Demon.
- Matteran Energy produces electricity and refrigeration from near ambient heat - An experimental small scale power plant is producing electricity and refrigeration temperatures fueled simply by the heat in warm water - typically 150 degrees Fahrenheit.
- Edwards Hot Water Heat Pump - is like a solar water heater without collector panels. It operates like a refrigerator only in reverse; transferring the heat in the surrounding air to the stored water. It is extremely energy efficient - using approximately one third the energy of a conventional electric water heater.
- Hallowell International - Air source All Climate Heat Pump has similar efficiency to a geothermal heat pump but at a fraction of the installed cost, cutting heating and cooling costs up to 60%. It uses a booster compressor and refrigerant subcooling to maintain comfortable indoor temperatures at outdoor temperatures well below zero, without back-up supplemental heat.
- Nyle Special Products - Heat Pumps have long been an environmentally safe, energy-efficient alternative to fossil fuels for warmer climates. The Cold Climate Heat Pump (CCHP) is the first and only air source heat pump that maintains high efficiency down to 0°F and below, generating savings of 40% or more.
- ICS Heat Pump Technology - Although the installation costs of ground source heat pumps can be greater than an air source heat pump so to can the long term efficiency and savings that are made. With a coefficient of performance (CoP) measurement of about 4% a high performance installation can potentially make a CO2 saving of up to 6 tonnes per year.
- Optimized Heat Pumps ‘Go With the Flow’ to Boost Output - National Institute of Standards and Technology (NIST) researchers are working to improve the performance of some heat exchangers even further by providing engineers with computer-based tools for optimizing their designs. (NewsWise; Jan. 25, 2008)
- Directory:Home Generation:Ground Source Heat Pump
- Directory:Home Generation:Space Heater
- Directory:Thermal Electric
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