An alternative way to heat

Heat Pumps supply more energy than they consume by extracting heat from their surroundings, consequently, they now form an essential part of the solution for reducing energy consumption and reducing carbon emissions and also provide their heat from renewable sources such as the ground and solar heated ambient air.    

A heat pump is an efficient and space saving means of heating a wide range of premises. It can also provide cooling to these premises should there be the requirement.   

Where heat pumps are used for heating, they are capable of highly cost-efficient energy applications because they tap into a limitless supply of ‘free’ heat – either the surrounding air or heat captured in the ground or water (such as a lake).

How they work
The vast majority of heat pumps work on the same principle as the domestic refrigerator utilising a vapour compression cycle, but for heating the heat pump utilises the ‘hot end’ of the process. The vapour compression process utilises low grade heat that is normally too cool for human or process requirements and lifts the same quantity of energy to a higher temperature that is then suitable for human comfort.   

This process is remarkable because the thermodynamic cycle occurs at constant energy content throughout even though the temperature has been increased from say 5ºC to say 35ºC. A refrigerant acts as the transfer medium and the only prime energy required is the energy to circulate the refrigerant.   

Depending on the application and type of heat pump, gains of 300 per cent to 500 per cent are normal.    

When dealing with heat pumps, and because efficiency cannot be defined as above 100 per cent, the term used is actually Coefficient of Performance (COP), so the COPs for the above example would be 3 to 1 and 5 to 1.
In its simplest form a COP is calculated by taking the heating output divided by the power input. For example, with a COP of say 4 to 1 the heating output relates to 4kW and the power input 1kW.

Saving carbon emissions

As well as being highly efficient in their use of energy, heat pumps emit considerably less CO2 to the atmosphere than gas or oil fired heating systems so they are more environment friendly, and the low grade heat source is considered to be a renewable energy source.   

Due to the technology of heat pumps their capital cost tends to be higher than conventional heating systems, however, the savings delivered in energy efficiency allow for very low operating costs. When utilised in commercial buildings, that also require cooling, additional cost benefits occur as there is no need to expend further capital on a second system for such cooling.

Main types of heat pumps
Heat pumps are normally classified by their heat source and means of delivery, for example, ‘air to air’ means air is used as the low grade heat source and air is also how the heat is delivered to the space.         

The main types of heat pumps are ‘air to air’ which is extensively used in commercial buildings as reverse cycle heat pumps (those that can provide both heating and cooling).

‘Air to water’ is used in many applications.  In conjunction with fan coil units in commercial buildings, for heating swimming pools, for providing domestic hot water and space heating for dwellings.

‘Water to air’ can use wells or boreholes, but can also be configured as many units connected together on a common closed water loop to enable energy transfer from hot to cold points in a building.   

‘Ground to air’ uses the stable ground temperature to provide the heat source with warm air being delivered to the space.   

‘Ground to water’ works as above but utilised with underfloor heating systems, medium temperature radiators or fan coil units.    

The lower temperature requirements of underfloor heating systems make heat pumps particularly efficient in this combination.
In addition, products may be single package, split package, ducted, rooftop, part of a central system, zonal system, or stand alone.

As we have seen from the above, heat pumps are typically used for commercial space heating, process heating and domestic heating and provide effective heating solutions for all types of building applications such as dwellings, commercial and retail premises, including hotels and residential complexes.

Commercial Applications

‘Air to air’ and ‘air to water’ heat pumps are frequently used in office and retails spaces, they are often installed in ceiling voids or alcoves and offer very favourable cost comparisons against conventional boiler systems when measured against installation and running costs.   

Heat pumps are used in many industries to recover heat, or as an integral part of the particular industrial process they are applied to. Swimming pools can use heat pumps as the primary source of heat for the water in the pool, for showers or to augment an existing fossil fuel system.    

In enclosed swimming pools, dehumidification is necessary and the heat recovered from the vapour in the air by a de-humidifier is easily employed to heat the incoming fresh air.    

The commercial market for heat pumps in the UK has been well established for more than a decade with a value in 2007 of circa £300,000,000.

Domestic Applications
Many homes can now benefit from a variety of Heat Pump installations, including ground source, water source and air source, generally providing warm water to underfloor heating matrices or upgraded radiator systems. The majority of these heat pumps will also be able to provide domestic hot water at temperatures up to 55ºC with some heat pumps able to provide 60ºC.   

The domestic market in the UK, unlike in other parts of Europe, is still in its infancy. However, initiatives such as the Microgeneration Certification Scheme (MCS) and most importantly the Renewable Heat Incentive (once the full details are released) will act as a catalyst for growth in this potentially large market.

Help is at hand
The Heat Pump Association is the UK’s leading authority on the use and benefits of heat pump technology and includes in its membership the majority of the country’s leading manufacturers of heat pumps, components and associated equipment.   

The Association was formed in January 1995 to promote the use of heat pumps through education, public relations and lobbying and to increase awareness of the technology through liaison with other relevant bodies and to promote the benefits and proper use of heat pumps and heat pumping technology.   

With the UK Government departments viewing heat pumps as part of the mix to reduce CO2 and to meet renewable obligations, the future is looking extremely good for the technology.

The HPA is an incorporated association of the Federation of Environmental Trade Associations (FETA).

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