How many types of heat pumps are there?
Heat pumps are extremely versatile and hence there are many types. They can use a variety of motive sources: Electricity and gas (natural and LPG). They can extract heat from the air, ground, water and processes. The heat can be delivered via air or water as the medium. The delivery temperature can vary from 35°C to 85°C in some circumstances.
See Types of Heat Pump.
Do heat pumps really save money and emissions?
Although heat pumps still require some form of driving energy input which is usually from a fossil fuel source (electricity or gas) because they are extracting heat from renewable sources (ground, water or air) which all ultimately get their energy from the sun, and this heat is a multiple of the transporting/pumping energy put in, they can, when designed and installed correctly, contribute to significant reductions in running cost and environmental emissions. With electrical driven equipment as the grid is decarbonised the renewable contribution from heat pumps will increase even more.
See Facts About Heat Pumps.
See Facts About Heat Pumps.
What does the Energy Savings Trust trials demonstrate?
The EST trials well demonstrated the effect of installing heat pumps in existing thermally poor buildings, with heating systems not suited to the optimum performance of heat pumps, with no quality standards for the proper design, installation and operation of the system. This was a major step forward in proving the need for comprehensive and robust quality standards and the positive result was the Microgeneration Certification Scheme document MCS 007 and Microgeneration Installation Standard MIS 3005.
How are dehumidifiers classed as heat pumps?
Dehumidifiers use exactly the same components as a heat pump and their method of operation is to operate simultaneously cooling unit and a heating unit, although ultimately they positively contribute to the heating effect whilst also removing moisture. This is in stark contrast to full loss air systems which also impose a thermal heating load.
Dehumidifiers: Firstly the air is cooled (evaporator) to below its dew point so that water condenses out of the air, removing moisture from the air stream. The same air is passed over the condenser coil where hot refrigeration gas re-heats the cold air. The result is that the air is reheated to beyond its original temperature (because the compressor energy is added to the process) with much less moisture in it than it originally had and hence the air is significantly dehumidified without losing heat.
This is a very energy efficient method of dehumidification which also results in supply temperatures being greater than inlet temperatures. It should be the default primary solution for applications such as Swimming pools etc but is often side lined by the short term view of cheaper but much less efficient solutions such as full fresh air.
What is the difference between a Ground Source Heat Pump and a Water Source Heat Pump?
Both devices themselves have water passing through the source heat exchanger and hence themselves are described as water-to-water or air heat pumps. The distinction tends to be the temperatures they are designed to operate at with Ground Source Heat Pumps typically meaning closed loop with source temperatures circa 0°C and water source referring to Open Loop (water extracted from the ground) source at circa 10°C. However water source can cover other wet sources such as lakes, rivers and sea which will have temperatures between these limits.
See Types of Heat Pump.
Are all heat pumps also air conditioning/cooling units?
It requires very few components and relatively minor software changes to convert a heat pump from heating only to reverse cycle (heating and cooling) however not all heat pumps are designed to reversible in practice. Even though air source heat pump units need the outside coil de-frosting during low ambient conditions and have a reversing valve fitted for this purpose it does not necessarily mean they are designed, suited or purposed to be reversed and there are many Heating Only Heat Pumps available. On occasions where both heating and cooling may be required it can make a lot of sense in terms of both capital and running cost terms to combine the function. Some reverse cycle heat pumps are even able to utilise the coolth or heat they create and recover this to different systems or areas of the building where it is required (e.g. heat recovery VRF systems).
Heat Pump Efficiency
The efficiency of a heat pump system can be expressed purely for the unit itself and no external power requirements (e.g. pumps) or for the wider system whole or part) at a single standard operating point. In addition the efficiency can be expressed over the season and hence a range of source and/or delivery temperatures.
The table below summarises this in principle.
When considering the wider system there are various system boundaries that can be used.
See Glossary of Terms for CoP, CoSP, SCoP and SPF.
For more information about work undertaken by the Association,
please email info@heatpumps.org.uk or call us on 0118 940 3416
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