Heat Pump

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Heat Pumps

www.leonardo-energy.org

What is a heat pump?

A heat pump enables energy-efficient heating

It does not produce energy

It ‘pumps’ heat at a relatively lower temperature from air, water, or soil and gives it off at a higher temperature into a building

Pros and Cons

Advantages– Lower life cycle cost due to high efficiency – Reduction of final energy demand by a factor 3– Reduction of CO2 emissions by 25 – 65%

(depending on baseline)– Business opportunity for contractors

Disadvantages– To be combined with low-temperature heating in a well-

insulated building– High initial investment cost– Requires large soil surface or water volume

(in case of a high efficiency water or soil heat pump)

Basic principle (1/2)

Refrigerator:Heat is withdrawn from inside a

refrigerator (low temperature)

Temperature inside refrigerator drops

Extracted heat is given off to environment (higher temperature)

Negligible temperature rise of the environment

Heat pump:Heat is withdrawn from

environment: air, soil, or water (low temperature)

Negligible temperature drop of the environment

Extracted heat is given off into building (higher temperature)

Temperature of building’s interior rises

Principle is similar to refrigerator:

Basic principle (2/2)

Four main components

Evaporator: – contains work fluid at lower temperature than environment.

Heat is extracted from ground, air, or water. Pressure is low, so the work fluid evaporates

Compressor: – brings gas to higher pressure, the temperature rises

Condenser: – gas temperature is higher than fluid temperature of heating

system. Excess heat is transferred to fluid. The gas cools and condenses

Pressure relief valve: – causes pressure reduction, the temperature drops, and the

cycle begins again

Also used for cooling

Has to be equipped with reverse valve to change circulation of the work fluid

This application is becoming popular

High efficiency

To obtain 100% useful energy:

Traditional system on fossil fuel:– 120% combustion heat (paid for) – Coefficient of performance = 0.8

Heat pump:– 30% electrical energy to drive compressor

(paid for); 70% taken from nature– Coefficient of performance = 3

Competitive life cycle cost

Should be combined with low-temperature heating

Lower temperature of heating fluid

Compensated by larger heating surface Large radiators Floor heating Wall heating Ceiling heating (ideal in combination with

reversible heat pump for cooling)

Round-up

Transfers available heat from air, water, or soil at lower temperature into higher temperature for a building

Also used for cooling High efficiency– Competitive life cycle cost– Lower environmental impact

Only effective in combination with low-temperature heating and adequate insulation

Investment cost is still high

Further information

Heat Pump Centre: www.heatpumpcentre.org

Green Building: www.greenbuilding.com