Drilling a borehole to install a ground loop.

Over half the energy used in commercial and public sector buildings in the UK is for heating and cooling. A heat pump is a low-carbon technology that extracts heat from a source such as the ground outside a building, and pumps the heat to the inside.

Geothermal International is one of the leading specialists in design and installation of heat pump systems in the UK, particularly for large commercial and public sector buildings.

The heat pump is just a wonderful system, keeping every space in the school at a perfect temperature, even on the coldest days. The children can pay more attention now they’re warm.

Lisa Sharratt, Head Teacher, Aldemoor School, Coventry

Background

Over half the energy used in commercial and public sector buildings is for heating and cooling. To reduce energy demand and carbon emissions, it is essential that buildings are  made more efficient, but there is still a need to use lower carbon sources of energy as well. A  heat pump, which works like a refrigerator, is one possibility for delivering lower carbon  heating and cooling. Geothermal International (GI) is one of the UK’s leading installers of  heat pumps, specialising in projects for the commercial and public sectors.

The organisation

GI Energy (formerly Geothermal International) was established by Brian Davidson in 2000. New investment from a number of private shareholders in 2006 led to the formation of Geothermal International Ltd. The energy supply company Scottish and Southern Energy (SSE) took a 20% stake in the business in 2008. GI’s turnover increased from £6m in 2006-07 to £14m  in 2008-09, when it employed 80 people. It also operates a growing network of accredited installers for domestic customers.

Drilling to install 'energy piles' for a new building in London.

The technology

How does it work?

A heat pump extracts low temperature heat from a source outside a building, and pumps it to provide heat at a higher temperature to the inside of the building. The external source of heat is usually the ground or a body of water, although air can also be used. The heat taken from the ground is renewable, because over time the ground is re-warmed by the sun, either directly or by heat conducted from adjacent earth. A further advantage in buildings where cooling is required is that the heat pump can operate in reverse, cooling the building by transferring heat back into the ground or water.

Electricity is needed to run the pump, and this may come from a renewable or non-renewable source. Using UK grid electricity, a well-designed ground- or water-sourced heat pump (GSHP or WSHP) can supply lower-carbon heating than using fossil fuels directly. The coefficient of performance (COP) is about 3.8, which means that for every unit of electricity used, 3.8 units of heat are supplied.

GI installs systems with heating and cooling capacities ranging from 6 kW to 6 MW. Large systems will include multiple heat pumps and can have many ground or water loops. GI usually uses heat pumps made by Water Furnace, a US-based company, and has exclusive rights to market these pumps in Europe. Sometimes other makes of pump are used for particular sites.

Drilling a borehole.

How much does it cost?

The installed cost for GI heat pump systems ranges from about £450/kW to £1,200/kW, depending on the size of the systems, the local geology and the complexity of the site. This initial cost is higher than for biomass heating systems (around £250/kW) but running and maintenance costs are lower.

How is it manufactured, promoted and maintained?

GI provides a complete service for installing a heat pump, including geological assessment of the site, engineering assessment, in-house design, borehole drilling and ground-loop, heat pump installation, system commissioning and maintenance. In most cases GI operates as a sub-contractor for the main building contractor and ideally is involved from an early stage in the building design, so that the best possible heat pump system can be provided for the particular site and building.

GI has a specialist maintenance and service division and offers either a five or 10-year maintenance contract for all its heat pumps. In addition, it gives a warranty on the output of the ground loop.

Installing ‘Energy piles’ at a new development in London. The ground loops are embedded in the building’s concrete piles.

Benefits

Between 2003 and 2009, GI installed 700 domestic heat pump systems, and 85 in commercial or public sector buildings. About 1,600 people benefit from the domestic systems, and probably 10,000-15,000 from working in buildings with large-scale systems.

The total installed capacity is over 100 MW, of which about 60% is for heating and 40% cooling. Over time, the GI market has moved to increasingly large systems, most of which combine heating and cooling. The largest system installed in 2009 was at Kings Mill hospital in Mansfield, where a nearby lake is used as the heat source for a closed loop system, providing 5.0 MW of heating and 5.4 MW of cooling.

Environmental benefits

Providing heat using a heat pump with a COP of 3.8, powered by UK grid electricity, gives emissions of about 0.11 kg CO2 per delivered kWh, a reduction of 49% on conventional gas heating systems. If the pump is used for cooling as well, then the increased COP (see box) means that the reduction in emissions during the heating season is about 60%. A cooling-only heat pump with a COP of 4.2 reduces CO2 emissions by 40%. If the pump is used for heating as well, the increased COP leads to emission reductions of about 57% during the cooling season.

Checking the ground loops, which are embedded in building foundations (Energy Piles).

The 100 MW heat pump capacity installed by GI avoids the emission of an estimated 25,000 tonnes/year CO2. The estimate depends on the building profile, how it is used and how much of the peak load is handled by the heat pump. The technology is quiet and produces no gaseous emissions at the point of use. Both these benefits are particularly valuable in urban areas.

Other benefits

Heat pumps provide a number of additional benefits to building owners. They give a straightforward way to supply a percentage of a building’s energy from a renewable source – often a prerequisite to gaining planning permission. Heat pumps are more compact than conventional boilers, and do not require intrusive, roof-mounted heat exchangers like conventional air-conditioning units. As most of the commercial buildings are new, many clients have also benefitted from the use of Energy Piles, which reduce installation costs and do not delay construction of the building.

Update: what happened next?

GI used part of their Ashden Award to fund a continuing programme of MSc research projects with Imperial College London. The funding enables students to undertake projects with a significant practical component. The Award also funded in-house research and development.

By November 2010, installed capacity had increased by about 50% to 150 MW, with a total of 900 domestic systems and 125 commercial systems installed. Total carbon savings are estimated at 37,500 tonnes/year CO2.

The company now supplies heat recovery, grey water recovery and PV systems for housing in the UK, and has started operations in the USA and Spain.