C-Mc Energy

Leading the Way to a Sustainable Future

Introduction to Heat Pumps

Our environment is a natural source of heat. There is heat in the air, in the ground and in water (rivers and wells). Heat pumps are designed to harness this free and renewable heat and use it to provide our central heating and hot water requirements.

This is done by extracting the heat from the air/earth. This heat is then upgraded to a higher temperature, before being delivered to the central heating system and hot water cylinder. Heat pumps also have the ability to do the reverse and provide a cooling system at warmer times of the year.

They are most efficient when linked to a low temperature heat distribution system such as underfloor heating, providing a constant steady temperature. The pump requires electricity to function, so it is more cost effective to programme it to use night rate electricity. Heat pumps are very economical, capable of cutting your heating bill by up to 70%. For every unit of electricity used to drive a heat pump, you can expect to produce 3-5 units of heat energy. The ratio between the heat produced and the electricity used to produce it, is referred to as the coefficient of performance (CoP).

With a heat pump, you can expect to achieve a water temperature of between 35 -45 C, very efficiently. This is lower than that achieved by a domestic boiler. The units are capable of achieving much higher temperatures but the CoP suffers meaning the economic and ecological benefits are compromised. In a well insulated house you can expect a heat pump to provide all of your space heating requirements, except perhaps in extreme conditions.

The two most common types of heat pump available are:

Geothermal Heat Pump

The first 12 metres of the earth maintains a constant temperature of between 10-16 C.

Similar to a cave, this ground temperature is warmer than the air in winter and cooler than the air in summer and so can be used to provide heating or cooling as required.

A geothermal heat pump extracts heat from the ground and converts it to a higher temperature. A network of pipes (collectors) is buried in horizontal trenches or vertical boreholes. A mixture of water and anti-freeze is pumped through the pipes. As it travels underground the heat from the earth is transferred to warm the fluid. The fluid returns to the heat pump where it is converted to a higher temperature through the refrigeration process. The heat can now be delivered to the heating system and hot water cylinder.

Air to Water Heat Pump

An air to water heat pump extracts heat from the air outside. The air passes through an evaporator where its energy is used to vapourise a refrigerant. Refrigerants have a very low boiling point. Even very cold air can provide sufficient heat to cause vaporization. The vapor is then compressed to increase the temperature. The heat is delivered to the hot water and central heating system.

The only space required for this type of heat pump is an outside wall, making them ideal for apartments and homes with limited outside space. With no need for groundworks, they are an ideal solution in areas where it is not possible to drill boreholes or dig trenches for ground collectors. With this more straight forward installation, costs are kept to a minimum and the payback period is shorter.