Renewable Heating & Cooling in the UK

Space and water heating, and the growing sector of space cooling, are a significant source of energy demand in the UK. Currently, 27% of the UK’s carbon emissions come from the residential property market, and the bulk of this is from heat demand. Consequently, the application of renewable technologies in this area has the potential to make a significant contribution to UK and EU renewables targets.

Wood pelletsThe term ‘renewable heating and cooling’ covers a wide range of different technologies used in commercial and domestic applications, from biomass-fired CHP power stations to domestic solar hot water systems and ground-source and air-source heat pumps, geothermal heating, biomass boilers and solar air-conditioning.

Although long neglected in government policy, the potential impact of a widespread uptake of renewable heating and cooling technologies on the country’s carbon balance, security of energy supply and manufacturing sector, cannot be understated with heat responsible for 47% of UK carbon dioxide emissions and accounting for 60% of an average of domestic bill.

In September 2008, the Department for Business Enterprise and Regulatory Reform (BERR) released a study led by Element Energy Ltd designed to determine the potential for micro-generation (including renewable heating) in the UK domestic sector. A 14-member consortium was established to fund the study, which included the Ashden Trust, BERR, British Gas Services Ltd, Ceres Power plc, the Energy Saving Trust, E.On UK plc, the Micropower Council, National Energy Action, the Renewable Energy Foundation, and a number regional development agencies.

The report concluded that, assuming a typical operational life of some 15–20 years then between now and 2050, most primary heating systems in buildings will need to be replaced at least twice. With a rising population and smaller household size, the number of UK homes could rise from 25 million to perhaps 37 million in 2050 and there are also currently some 1.5 million non-domestic buildings. In addition to the vast replacement market, there is a growing discretionary demand for renewable heating and cooling technologies, such as roof-mounted solar thermal and heat pump systems.

As a result, over this period, the market for primary heating is immense.

Indeed, the report estimated that between 95,000 and 98,000 microgeneration systems had already been installed in the UK by the end of 2007, the vast majority of which were solar thermal units – which had the highest levels of sales of at least 5000–6000 units per year. By 2007, the cumulative number of renewable heating installations had reached an estimated 90,000 solar thermal systems, perhaps 1500–3000 biomass boilers, 745–2000 ground source heat pumps and at least 150 air source heat pumps, BERR says.

The study produced a baseline scenario for a total of some 1300 ground source heat pumps, 3200 air source heat pumps, 2300 biomass installations and 146,300 solar hot water systems installed in the UK by 2015. And, under various renewable heating
support scenarios – notably a favourable heat ‘feed-in’ or production tariff – the study concluded that air-source heating in particular has a very large potential for growth.

Nonetheless, demand for such systems remains heavily underpinned by government funding and other supporting initiatives. Professor John Chesshire OBE, chair of the microgeneration study Steering Group, highlighted other influential factors too, commenting: ‘Investment in manufacturing capacity for such systems and final users’ choices amongst them, will be affected by absolute and relative energy prices, consumer preferences, technological change, and government policies.’

Policy support

Most government funding for small-scale domestic renewable heating and cooling installations has so-far come through the Low Carbon Buildings Programme, a limited pot of money set aside for supporting all forms of micro-renewables and which is due to be phased out over the coming year.

However, the most significant UK policy event for the renewable heating and cooling sector is the government amendment to the Energy Bill to include feed-in tariffs and Renewable Heat Incentives (RHI). Although details of the support level have yet to emerge there is a clear intention for the scheme to be running by April 2011 and this bill, granted Royal assent in November 2008, finally offers the renewable heating industry the recognition it so richly deserves.

Industry and environmentalists welcomed the decision, but expressed concern at a lack of firm proposals. Philip Wolfe, director general at the REA, commented: ‘The devil will be in the detail and the coming year will herald key negotiations over the nature and size of the benefit each technology is to receive. The heat and gas tariff has no upper size limit and will be a pioneering measure that other countries would be expected to follow, but the industry is keen to see the heat tariff brought in in April 2010, not delayed to 2011.

Meanwhile, Friends of the Earth’s executive director, Andy Atkins also noted: ‘Britain’s renewable energy potential is enormous. The inclusion of a feed-in tariff in the Energy Bill will hopefully encourage homes, businesses and communities to install green energy systems and play a key role in cutting emissions. Ministers must ensure that payments are high enough to make this happen.’

Furthermore, Kevin Brennan, head of Sustainability at Velux Company Ltd, ventured: ‘One of the big challenges we currently face is how to measure the heat generated at a single household level. Following this recent amendment, I look forward to hearing further details from government on how it plans to ensure accurate measurements are taken.’ Even so, previously Brennan had commented: ‘Currently only 0.004% of the UK’s housing stock have solar water heating, yet over 76% of homes in this country could successfully make use of this technology. While installing solar thermal in all homes across the UK could prove a challenging task, a commitment from house builders to incorporate this technology into all of their new builds could still have a significant impact on reducing the UK’s carbon emissions. Within 30 years, the new homes being built today by house builders will be approximately 30% of the entire housing stock, so even small gains today will be significant gains in 30 years time.’

In February 2009, the government further announced plans for all UK homes to be near zero carbon emissions by 2050, under an ambitious long-term Heat and Energy Saving strategy.

The draft plan includes proposals for whole-house improvements to be available to householders in every home by 2030, as well as finance packages to install energy efficiency measures and low-carbon heat and power sources offered to householders, with repayment from part of the savings on energy bills linked to the property, rather than residents. This would be combined with guaranteed cash payments by way of the Renewable Heat Incentive.

Commenting on the announcement, Energy and Climate Change secretary Ed Miliband said: ‘We cannot afford not to act. Every home must be able to access the help and technology it needs, whether it be the installation of a ground or air source heat pump, solar heating, solid wall insulation, or access to a district heating scheme.’

Housing minister Margaret Beckett added that social housing must be at the forefront of such developments.

The UK Green Building Council said in its response to the consultation, that the strategy needs to be supported by financial mechanisms to enable people to meet the up front costs of refurbishment; fiscal incentives to galvanize action; training and accreditation for installers; information and support for occupiers and landlords; and a long-term timetable for minimum energy efficiency standards for all existing homes and buildings.

Vacuum pipesSolar thermal heating

With the potential to provide an average UK household with up to 70% of domestic hot water needs as well as space heating, solar thermal heating systems can make a real difference to domestic energy demand.

The technology involved in solar thermal systems is relatively simple, with two main types of collectors. Flat plate collectors are glazed, insulated panels containing a solar radiation absorber surface. This collector is connected via a flow and return pipe to a heat exchanger in the hot water cylinder.

The second main type of solar thermal collector is the evacuated tube. These consist of a series of tubes each containing an absorber and a pipe surrounded by a vacuum. The vacuum, being better at minimizing heat losses than standard insulation, is generally more efficient but is also more costly to produce. Both types of collector are typically supported with a conventional fossil or bio-energy-fuelled boiler central heating system to guarantee year-round supply.

Currently the UK is home to several manufacturers of solar thermal systems, including one of the major producers of evacuated tube devices. Thermomax is based in two locations in the UK (Northern Ireland and Wales) with a third location in Italy, and produces a series of collectors along with control systems and data loggers. It is now owned by Kingspan.

There are also several UK-based flat plate manufacturers, including Imagination Solar, Solar Twin, MTS Ltd, Genersys, Velux and AES Solar. In addition to manufacturers, there are a range of companies such as Baxi, Dulas and Riomay, which install complete solar thermal hot water systems, as well as manufacturing some of the components; while early in 2006, Vaillant introduced a solar thermal boiler package onto the UK market.

As with solar PV, compared with many of its northern European neighbours, the market for solar thermal heating systems in the UK is underdeveloped. This is partially due to a lack of support schemes and awareness, coupled with a common belief that solar thermal will only work in hot countries. In fact, solar thermal can be more efficient at saving energy in colder climates where the baseline water temperature is lower.

Despite the lack of rapid growth in the UK, there are signs emerging that solar thermal is becoming a more recognized source of energy and although the house building sector is suffering during the economic downturn, a number companies, notably Barratt (one of the UK’s largest) have announced residential development projects which are to incorporate solar thermal technology.

In addition to residential schemes, there remains a consistent market for solar thermal in large commercial applications, typically those with a large thermal demand such as hospitals. In addition, renewables focused companies have also taken more interest in solar thermal technology.

Solar energy also has the potential to provide a usable low-carbon solution for the growing area of space cooling, particularly for large systems of 50 kW or more.

Like solar heating, solar air-conditioning units use heat to drive one of two cooling cycles (either thermally driven water chillers or desiccant cooling systems). While this technology has yet to achieve any significant presence in the UK, there is a good opportunity for solar cooling to ‘get in on the ground floor’, before more traditional fossil-fuel driven forms of air-conditioning become well established.

Ground, water and air source heat pumps

Heat pump systems already operate in every home – in our refrigerators and freezers. To provide space heating, such systems effectively cool a large external mass of, say, air or water at ambient temperature and expel the heat extracted into the living space. In ground source heat pumps this is achieved by running a water/antifreeze mix through a long coiled pipe buried underground. These pipes may be laid horizontally at a depth of 1–2 metres or vertically in boreholes 15–100 metres deep. Some of these systems can also be used for cooling by reversing the pump.

As the heat found in the ground, water or air is derived largely from the earth’s core and sun, the only non-renewable energy involved is used to operate the pump or compressor. If this power is sourced from renewable electricity, then the heat pump is effectively an entirely renewable resource. Even if this is not the case, ground source heat pumps can generally deliver three times as much energy as they require to operate.

Such ground source projects can supply significant quantities of energy. For instance, in spring 2009 a 100 kW ground source system was installed on behalf of the Norfolk & Waveney Mental Health Foundation Trust, at a new mental health unit at the Hellesden Hospital in Norwich. Developed by local firm Econic, with its geotechnical partners Lankelma Green Energy, the 120 boreholes at the site were produced using hydraulic rams rather than conventional drilling – reportedly a new method for heat pump systems. The hospital has two 50 kW heat pumps working to extract the heat from the 25 metre-deep boreholes.

Heat pumps are also found in some novel applications. For instance, pharmaceuticals giant GlaxoSmithKline (GSK) has developed an on-site cooling system at its global headquarters in west London, using water from the Grand Union Canal and heat exchange technology. The system is primarily designed to cool the company’s computer data centre and as well as cut energy costs, the move is expected to cut the equivalent of 920 tonnes of carbon emissions from GSK’s head office. GSK spokesman Duncan Learmouth, said the development made good business sense, ‘with a five year pay back of more than £100,000 (€116,000) of annual energy savings.’

With some 2200 miles (3540 km) of canals and rivers across the UK under its control, British Waterways – which partnered GSK in the project – estimates that a further 1000 waterside businesses nationwide could also use water-source heat pump technology for heating or cooling.

The University of Nottingham is also using heat pump technology as part of a new building programme. Building company Rok SOL used the so-called ‘Slim Jim’ heat exchange technology, supplied by Geothermal International, to provide both heating and cooling for new buildings on the University’s Jubilee campus.

While ground and water source heat pump technology is suitable for domestic-scale installations too, it is the air source heat pump market which appears to hold the most promise. ‘It’s become increasingly clear over the past two years that air source heat pumps are the future of mass market, low carbon heating for British homes,’ commented John Kellett, general manager of Mitsubishi Electric’s Heating Systems.

There are a number of UK-based suppliers and installers of ground source heat pump technology operating in the UK, such as Cornwall-based EarthEnergy, Coventry-based Geothermal International, Clivet UK and Baxi, as well as some manufacturers like Calorex, Dimplex and ICE. A large number of overseas boiler manufacturers such as Vaillant, and Worcester Bosch, which has UK manufacturing plants, also supply air and ground source heat pump equipment. Furthermore, established renewable energy companies are also entering the heat pump sector. For example, Kingspan Solar, part of Kingspan Renewables Ltd, launched its new Aeromax range of air source heat pumps in 2009. Specifically designed for external use in Northern European climates, the company says its heat pumps can supply the demands of space and domestic hot water to UK homes year-round.

Meanwhile, Mitsubishi Electric has launched a three-model air source heat pump range, Ecodan, which has been specifically designed for the UK market. In May 2009, the company revealed results of over-winter testing in the UK. ‘We saw temperatures drop to -9ºC and -10ºC at times throughout the country, which is exactly what we were hoping for as it meant we were able to put theory into practice,’ explained Max Halliwell, product manager for Mitsubishi Electric Heating. He added: ‘All too often, different heating systems manufacturers make different claims based on technical data or lab tests under very favourable conditions, and this presents a confused message to the public.’

Biomass stoves and boilers

The modern, high-efficiency version of the log fire, pellet and woodchip stoves and boilers are small domestic biomass systems are used to provide hot water and space heating. Designed and operated along similar lines as conventional gas and oil boilers, they may use processed wood waste to provide a clean and manageable form of energy.

Modern burners are commonly fully automated and use advanced electronic systems to control the amount of fuel and air. Such systems span a huge range of capacities from small and compact pellet stoves – typically heating a single space or room although room heaters also can have back boilers or water jackets that can run radiators – right up to industrial biomass boilers supplying process heat.

Renewable heat from biomass also includes systems which use bio-liquid-fired appliances as well as those relying on anaerobic digestion to produce biogas, which is in turn is used to supply heat. For example, in 2009 Scottish Water Waste Services signed a contract for the design and construction of an anaerobic digestion plant at their Deerdykes facility, outside Cumbernauld, in Scotland, which will process some 30,000 tonnes of food waste annually. Material from the digester will be supplied by the local authority under its Landfill Directive obligations, together with waste from local food retailers and producers. Gas generated by the facility will be used in reciprocating engines to supply electricity to the grid and the heat is to be used on-site and potentially in neighbouring industrial estates. A nearby company has a heat demand with a good match to the planned facility’s output, and Scottish Water is examining the feasibility of making a connection to the heat network, with confirmation on the decision due in June 2009.

On the domestic scale, pellet boilers for hot water and central heating are widely used in some European countries, such as Austria and Germany, although they are not currently widely employed in the UK. Nonetheless, a growing number of developments are installing biomass heating systems, typically at community level under the LCBP scheme, through the Bioenergy Capital Grant Scheme or through utility projects such as E.ON’s SOURCE programme. For example, utility group Scottish and Southern Energy (SSE) are running a Carbon Emissions Reduction Target (CERT)-funded biomass community heating and CHP programme for community and social housing schemes. The programme, managed by CWP Ltd is likely to provide thousands of homes with heat from biomass over the coming few years.

As with a number of other renewable technologies, most of the existing domestic boiler manufacturers also supply biomass boilers too.

There is a growing supply chain for pellets – one of the most convenient fuel sources for consumers as the fuel can be mechanically fed into the boiler and almost no supervision of the system is required (about once a month the small quantities of ash generated must be removed).

Two major UK manufacturers of wood pellets in the UK are Welsh Biofuels and Balcas; they are joined by several smaller manufacturers such as Premier Waste in Durham, Renewable Heat and Power Ltd in Devon and Puffin Pellets in the north east of Scotland. The UK also imports pellets from a number of European and North American manufacturers.

A market heating up

Renewable heating and cooling represents one of the most exciting and (until recently) most overlooked areas of the renewable energy picture. With the potential to provide cost-effective alternatives to fossil-based resources in one of the most emissions-heavy and intractable sectors (domestic water and space heating) efforts to more fully recognize this sector are encouraging.

However, while there is little doubt that the introduction of a renewable heat incentive will do much for the industry, there are also signs that such measures may rapidly become less important. In 2009, Good Energy, the UK’s only 100% renewable electricity supplier, launched its Good Energy HotROCs programme. The country’s first renewable heat incentive, it pays domestic solar generators money for the heat energy they produce.

As part of this scheme, the company launched a trial gas product which charges a small premium to finance the solar thermal reward scheme.

Juliet Davenport, Good Energy CEO, noted: ‘HotROCs is a simple effective reward and … we are confident it will succeed and be copied by other UK energy suppliers.’ Should this confidence come to be rewarded, renewable heating and cooling will undoubtedly make one of the single largest contributions to the UK’s renewables targets. n

The inclusion of a feed-in tariff in the Energy Bill will hopefully encourage homes, businesses and communities to install green energy systems and play a key role in cutting emissions.

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