Heat pumps as a building-services technology

Published:  06 April, 2009

Terry Seward - FETA
Opportunities for heat-pump technology — Terry Seward.

Terry Seward explains why the age of the heat pump has come.

These are exciting times for all aspects of heat pump technology and, indeed, for all types of heat pump. There are few heating and cooling applications that cannot benefit from heat-pump technology and, in doing so, deliver significant energy efficiencies. Heat pumps are available to claim free or waste heat from a number of sources.

•Ambient air.
•Ground water and other water sources.
•The ground itself.
•Commercial applications where unwanted heat would be rejected.

Heat-pump technology can be used in applications as diverse as space heating or cooling for human comfort in offices, homes and all kinds of residential installations. They can also be found in applications for process drying, swimming pools and factory production processes.

Heat pumps increasingly lead the way as one of the solutions for a sustainable future. They are a low-carbon technology and, following the EU Parliament’s vote on 17 December 2008 on the Directive for the Promotion of Energy from Renewable Sources, are now a recognised renewable heating technology when utilising the solar-heated ground, ambient air, and water as a heat source.

Although many will have taken as read the fact that heat pumps have these positive attributes, a number of official ‘hurdles’ have had to be negotiated both at UK and European level. The Heat Pump Association has been involved in 11 separate consultations in the UK and Europe regarding both legislation and initiatives pertaining to heat pumps and their status within the low carbon and renewable agendas.

Irrespective of the ‘hurdles’ mentioned above, the heat-pump market grows unabated and steadily within the commercial sector and is starting to grow at a very fast rate in the domestic sector.

Although the term heat pump is now known by all levels of society, it is still often, erroneously, considered to be an emerging technology. In the commercial building-services sector, however, heat pumps have been specified and installed since the mid 1950s!

The technology has evolved greatly during the half a century since. It has progressed from being an emerging to a mature technology, which is realised by specifiers in the commercial buildings sector. The 2007 market for heat pumps in this sector in the UK was an over £300 million, relating to some 200, 000 products. The scope of the installations ranges from single units through to massive systems.

Most heat pumps supplied to the commercial sector provide heated air and utilise air as a heat source. Moreover, the vast majority of them will be reverse cycle and provide cooling to counteract heat gains during the summer. Although this sector is dominated by air-to-air systems, many applications use air-to-water or water-to-water. Ground-source to air or water are other possibilities.

The domestic market is responding to initiatives to reduce carbon emissions by investing in heat pumps. However, the domestic heat-pump market in the UK still remains slow compared with the rest of northern and central Europe. Thankfully the signs are that this particular market is now taking off. We predict 2000 to 3000 ground-source heat pumps being sold into the domestic market in 2009 and a similar figure for air-source heat pumps.

The predominant products for the domestic sector will be ground-to-water and air-to-water, as heated water systems are the traditional means of heat distribution in UK dwellings. However, ground-to-air and air-to-air products are also available for dwellings requiring warm-air distribution.

FETA diagram
This diagram shows the most common ways in which heat pumps are categorised by function, heat source and distribution medium. Absorption systems are also available, but the overwhelming majority of heat pumps applied worldwide utilise the vapour-compression cycle.

Why would you specify a heat-pump solution?

Heat pumps emit considerably less carbon dioxide to the atmosphere than gas- or oil-fired heating systems, so they are a low carbon technology, and the low grade heat source utilised is considered to be a renewable energy source.

However, the economics are important as well. The capital cost of heat pumps is higher than conventional heating systems, but their energy efficiency gives very low operating costs. There are additional cost benefits when reverse-cycle heat pumps are used in commercial buildings that also require cooling, as there is no need to spend further capital on a second system.

Heat pumps are normally classified by their heat source and means of delivery. For example, air-to-air means that 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 as follows.

•Air-to -air.
•Air-to-water.
•Water-to-air.
•Water-to-water.
•Ground-to-air.
•Ground-to-water.

In addition to this wide variety of types, heat pumps may be single package, split package, ducted, rooftop, part of a central system, zone system, or stand alone.

Consequently there is a raft of heat pump solutions for every conceivable type of application.

The future is looking good for the heat-pump industry and its customers!

Terry Seward is commercial manager with the Federation of Environmental Trade Associations, of which the Heat Pump Association is a member.



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