Heat Pump Technology

A heat pump can raise the temperature of thermal energy. In practical terms, this means that it can take low temperature heat, for example sourced from groundwater or recovered from an industrial waste stream, and upgrade it to a higher, more useful temperature. Better use of waste and low cost heat sources can mean lower heating costs, and less environmental impact. Best practice in the application of heat pumps provides flexible and economic heating and cooling, and helps to minimise environmental impact.

What can heat pumps do for the environment?

Global warming emissions, in particular CO₂, can be reduced if less fossil fuel is burnt. Whilst alternatives are available, most heat pumps are electrically driven, and are competing with gas-fired heating systems in the UK.

However, when evaluating competing systems it is important to compare on a like for like basis. Whilst electricity is clean at point of use, fossil fuels are burnt to generate electricity which gives rise to CO2 emissions.

• With electrically driven equipment, for every electrical kWh consumed at point of use, nearly three times that amount of fossil fuels (in kWh terms) are burnt to generate and distribute it. The efficiency of the heat pump determines how much useful heat is delivered for each kWh of electricity consumed.
• For gas driven equipment conversely, production & distribution of gas does not involve so many losses (1.1 times the 'point-of-use' kWh figure), and boilers have their own associated efficiencies. Similarly for oil.

The easiest way to analyse the environmental impact is perhaps to consider the total mass of carbon dioxide emitted to deliver each kWh of heat.

This analysis leads to the following indicative hierarchy of year-round CO₂ impact for current typical domestic cases. Note - not all types of unit are included and many others are possible; also specific design factors may alter performance positively or negatively.

Figure 1. Hierarchy of indicative CO₂
impacts for domestic heating

It is far more difficult to generalise such a hierarchy for commercial and industrial cases due to the greater diversity of systems and applications.

It must be borne in mind that many factors affect the efficiency & economics of heat pumps, and decisions must be carefully assessed. Heat pump systems are getting more efficient, whereas fossil fuelled heating is approaching its efficiency limits. The environmental argument will therefore increasingly swing towards sensible application of heat pumps in the future.

Independent information about this technology is available through the periodic newsletters and workshops of the UK Heat Pump Network. For specific advice on commercial, domestic and industrial applications, call the Environmental & Energy Helpline 0800 585 794 or search http://www.actionenergy.org.uk

You can download copies of the UK newsletter from the publications section.