Heat Pump and CHP

Heat Pumps

Ground source heat pump pipe installation

Ground source heat pumps transfer heat from the ground to a building via water-filled pipes in trenches or inserted down a borehole. Air- and water-source heat pumps take their heat energy, respectively, from the air or a body of still water or a mill leat. These ground, ambient air or water temperatures are sufficient to evaporate a refrigerant with a very low boiling point. A compressor raises the temperature of this gas by up to 80°C and it condenses as it transfers this heat to a radiator system and/or to hot tap water. As the cooled fluid then passes through a pressure release valve it drops again to below 0°C and the cycle is repeated. Heat pumps work most efficiently at lower temperatures and therefore tend to be better suited to new-build installations than to replacing conventional boilers.

Whilst heat pumps use significant amounts of electricity in their operation, the heat transferred from the environment is considered renewable and the combination represents an efficient use of electricity which, in a well-designed system, reduces carbon emissions as well as heating costs. They should last for decades and require very little servicing and maintenance.

A typical ground- or water-source heat pump system may cost between £16,000 and £30,000. An air-source heat pump may cost £8,000 to 18,000. This can be returned by the Renewable Heat Incentive (RHI) over 7 or 20 years depending on the situation. Whilst heat pumps can be successfully retro-fitted into older buildings, great care must be taken in their design and all possible energy efficiency measures implemented if they are to be cost-effective.

Combined Heat and Power (CHP)

Combined heat and power, whether from natural gas or renewable energy sources such as biogas and biomass, represents a great increase in energy efficiency compared to conventional electricity generation where two thirds of the primary heat applied to the process is wasted up a chimney. Good quality combined heat and power systems, where ALL the heat generated can be used to heat buildings or provide heat for a production process, can be very cost-effective although renewable fuel systems require a considerable amount of maintenance. These should benefit from both feed-in tariff and the Renewable Heat Incentive. They are placed to become increasingly popular, as they already are in many European countries.