The key to a low carbon future

Although the industry appears to be holding its breath following the closure of the Low Carbon Buildings Programme and the scrappage of the Building Schools for the Future scheme, the UK has tough carbon emission reduction targets to hit and renewable heating technology such as heat pumps will have to play a major role.

Tempus fugit

It’s going to take all the resources we have at our disposal to meet the UK’s tough and legally-binding targets for reducing carbon emissions – a massive 34% reduction on 1990 levels by 2020, which is not far away. Think back to ten years ago; Y2K, the Millennium Dome, Ken Livingstone becoming mayor of London, and Venus Williams and Pete Sampras winning Wimbledon. The next ten years is going to fly by just as quickly and the UK is waking up to the fact that it needs to put measures in place to ensure those targets are hit.

Renewable heat has the potential to make a substantial reduction in energy demand for space and water heating. Last year’s Renewable Energy Strategy estimated that by 2020, 12% of our heat could come from renewable sources – that could be around 4 million homes in the UK. And DECC’s latest ‘2050 Pathways’ research goes even further, looking at various possible scenarios including one where UK heating energy demand could be supported by 20 million heat pump installations.

Support for heat pumps, in one form or another, looks likely to continue. The Renewable Heat Incentive (RHI), planned for introduction in 2011, will provide financial support for locally-harvested renewable heat at all levels, including solar thermal water heating and heat pumps. The new government is currently reviewing the scheme, but has recently confirmed in its first annual energy statement that it views renewable heat and the RHI as key to Britain achieving its carbon emission reduction targets.

Plus, of course, heat pumps continue to make sense from a building services point of view. Able to draw up to 75% of the warmth they produce from the environment, they offer insulation from fluctuating energy prices as well as a way to reduce carbon emissions in this CRC Energy Efficiency footprint year. Certain models also have the capacity to meet both heating and cooling requirements with a single system, so they tick all the boxes for all kinds of buildings up to large commercial and multi-dwelling developments.

Functioning as a whole

It’s important to remember that any heat pump is only as good as the system into which it’s designed. Installers and system specifiers need to be appropriately trained and qualified, since heat pump systems can be complex, and with so many variables, there’s a risk of underperformance if the whole system hasn’t been designed to work efficiently to meet maximum heat requirement.

The need for renewables training and installer education has been highlighted by the publication of a report by the Energy Saving Trust on a field trial of heat pumps in existing properties across the UK, which showed a wide band of performance results. While some installations delivered seasonal CoPs of around 3.5, others fell short of expectations.

All the installations in the study were carried out pre-MCS and the EST now hopes to extend the trial for a further 12 months to compare the improvements in the system following the initial results. While it’s expected that the measures the industry proactively put in place to address quality issues before the completion of this study, i.e. MCS, will have improved standards, the trial nevertheless highlights the need for the correct system design and application. No doubt industry training will be able to benefit from focusing on some of the issues brought to light.

Getting heat to where it’s needed

The good news is that heat pump systems offer great flexibility over system design. For example, there are now even more choices when it comes to heat distribution systems. In addition to oversized radiators or underfloor heating, neither of which are particularly easy to manage in retrofit installations, specifiers now have the option of fan convector radiators, like the Dimplex SmartRad range, which are easy to link into existing wet system infrastructure, allowing heat pump CoP to be optimised, as they offer excellent performance at water temperatures as low as 40°C.

Heat pumps are ideal for all kinds of installations, two of which are outlined below.

Heat pumps in action

At a large secondary school in Hertfordshire, a Dimplex LA 40 TU air source heat pump has been used as part of a low carbon system in a new building for the maths department. The school is one of the first in the UK to use this kind of high efficiency air source unit, which offers a CoP in excess of 4.0 – that’s comparable to ground source technology, but without the requirement for ground collectors.

The building was opened to students in January this year. The heat pump system had been specified to produce a 28kW output at an air temperature of -3°C, and the exceptionally harsh winter certainly put this to the test. However, the heat pump performed well, keeping staff and students comfortable in the most extreme conditions with gentle warmth from the underfloor heating.

A particular requirement of the system was that it had to be quiet in use, which this range of heat pumps achieves through the use of a casing for the internal compressor, which stands within the heat pump on anti-vibration feet, insulating the compressor and dramatically cutting sound transfer.

Cleverly, the environmental control system in the high-tech classrooms includes a carbon monoxide sensor system. When the CO2 concentration reaches a certain level, due to the breathing of the occupants, the windows open automatically, the fans hidden behind louvres start to operate and the air in the room is circulated to boost the students’ alertness.

Energy reduction

As part of a major conservation programme, one of Britain’s finest historic houses, Castle Howard, has reduced energy costs by over 60% following the installation of two 100kW Dimplex ground source heat pumps. Key objectives for the leading visitor attraction were to target and slash the annual £40,000 fuel bill, improve the carbon footprint and reduce overall expenditure to allow more investment in conservation.

Plans for a fast track installation were finalised during 2009 and the three-acre lake, designed to allow the beautiful house to be reflected on its surface, was drained for the installation of the coiled pipes which are connected via 1m deep pipes to the basement in the house. The system provides hot water and heating using the existing wet system for the main house, the estate office and four staff residential flats, generating four kilowatt hours of heat for every kilowatt hour of electricity the heat pump uses.

The six month long £200k project received a significant level of grant support from the Carbon Emissions Reduction Target scheme, as well as an interest free loan of nearly £60,000 from the Carbon Trust. Measurements taken since the heat pumps were switched on in September 2009, have shown the average fuel bills drop dramatically, giving an expected payback on the system of just six years.