Information on Heat Pumps

What is a Heat Pump

A heat pump is a device that moves heat from one location to another using a small amount of energy. It is often used in moderate climates and uses the air temperature difference between indoor and outdoor air to cool and heat your home. While an air conditioning system generates heat, the heat pump moves heat, this way being more energy efficient. Heat pumps can provide up to four times more energy than they use.

Naturally, heat flows to a lower temperature from a higher one. With the use of a small amount of energy--electricity, fuel, high-temperature waste heat--a heat pump forces the heat flow into the other direction. A heat pump transfers hot air from sources like surrounding air, ground, water or waste into a building. When it cools a building, the heat is transferred into the opposite direction.

There are two main types of heat pump technologies used: vapor compression and absorption cycle.
A vapor compression system consists of the compressor, expansion valve and two heat exchangers (evaporator and condenser). The absorption system consists of the absorber, solution pump, generator and expansion valve.
The vapor compression process: the evaporated refrigerant liquid is transformed to hot vapors. The vapors enter the condenser and are transformed into hot vapors. The hot vapors give off the useful heat and are expanded to the evaporator pressure. Finally the working liquid returns to its original state.

The heat pump can be categorized according to the heat source used. The most commonly used type is the air-source heat pump. As the name suggests, it transfers heat from outside air. The disadvantage of this type of pump is that it can only be efficient in moderate climate conditions.
A more efficient type is the geothermal heat pump that transfers heat from nearby ground source or water source. The installation costs more for geothermal pumps compared with air-source pumps, but have lower operating costs, as the ground or water has a constant temperature. This type of pump can be used in more extreme weather.
Other types include the ductless mini-split heat pump--for homes without ducts--and the reverse cycle chiller pump--a type of air-source heat pump that generates hot and cold water.

The performance of a heat pump is the difference between the energy used and generated energy. A heat pump can generate 100 kWh (unit of power: kilowatts per hour) using just 20 to 40 kWh of electricity. An industrial pump can generate the same amount of heat using only 3 to 10 kWh of electricity, according to heatpumpcentre.org.
Due to the low consumption of primary energy, a heat pump reduces the gas emission that harm the environment --carbon dioxide, sulphur dioxide, nitrogen oxides.