ground source heat pumps DOMESTIC & SMALL SCALE COMMERCIAL
Ground Source Heat Pumps
The sun warms the ground temperature
A renewable energy source Heat is distributed through underfloor heating, radiators or air ducts
What are heat pumps? More and more homes in the UK are being heated by heat pumps. This little understood concept has been around for many years, but has only recently become of interest due to the current concerns over global warming and other environmental issues. A heat pump is a device that moves heat from a low temperature heat ‘source’ to a higher temperature heat ‘sink’. Put simply, it moves energy from one place to another. By using this process, ground source heat pumps remove energy from a source and transfer it into a building. The sun naturally replenishes the energy removed from the ground. The use of heat pump systems is becoming commonplace in many parts of the world such as in the USA and in much of Europe.
What are the benefits? Efficiency - The efficiency of a ground source heat pump system is measured by the coefficient of performance (CoP). This is the ratio of units of heat output for each unit of electricity used to drive the compressor and pump. Average CoP over the year is around 3-4. This means that for every unit of electricity used to pump the heat, 3-4 units of heat are produced. This compares favourably to a conventional electric resistance heater that has a COP of 1 – whereby one unit of electrical energy will produce only one unit of heat. Greenhouse gas emissions - Heat pump systems only generate around 55% of the greenhouse gas emissions associated with energy efficient ‘A’ rated domestic gas boilers. Maintenance - There is no need for regular servicing or annual safety checks such as with a gas or oil boiler; therefore, heat pumps are very low maintenance. Crestra uses full systems or components manufactured by respected companies. Location - Heat pump systems do not require the use or storage of external fuel. The systems instead run on electricity, which eliminates the need for a gas connection or storage of oil/ solid fuel. Crestra can also offer a complete service in the supply and installation of renewables and other energy saving measures. This can include air source heat pumps, photovoltaics, solar hot water, cavity/external wall insulation and loft insulation. Our customers include homeowners, local authorities, housing associations, businesses and schools. If you would like to visit our offices to see a working ground source heat pump, photovoltaic system or solar hot water system, please contact us.
Liquid in the pipes underground absorbs the heat
How do ground source heat pumps work? Ground source heat pumps use a buried ground loop of pipes or ‘collectors’ to transfer heat from the ground into a building to provide heating. Ground source heat pumps are usually more efficient than air source heat pumps because groundwater maintains a relatively constant temperature (around 10°C) all year round. This means that the heat pump will have to work less hard and consume less power to achieve the same heating effect. Pipes can also be placed in a nearby water source such as a stream, river or pond. There are three major components to a ground source heat pump system: The ground loop - Closed circuit pipes filled with a water/ antifreeze mixture are buried in the ground, either in a horizontal trench, boreholes, or in a water source. The mixture is pumped around the pipes absorbing heat from the ground as it goes. Spiral, coil or 'slinkys' are often used to save on space and reduce trench lengths required. A heat pump - A ground source heat pump has three main parts: The evaporator that absorbs the heat from the liquid in the ground loop; the compressor that circulates the refrigerant round the heat pump and compresses the gaseous refrigerant to the required temperature for the heat distribution circuit; and the condenser which provides heat to a hot water tank to feed the distribution system. Heat distribution system - Usually under floor heating pipes or radiators for space heating and sometimes water pre-heating of stored water in a cylinder for hot water supply.
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The main benefits of a ground source heat pump
There are no on-site emissions, flammable oil, LPG or gas, and they require no unsightly pipelines, no flues or chimneys and no ugly and expensive fuel tanks.
Ground source systems are predominantly used to provide space heating; they can also be used to heat domestic hot water by utilising immersion heaters installed in high efficiency indirect water cylinders which is best done utilising night time off peak rates.
The initial higher capital cost of a ground source heat pump compared to a gas or oil boiler is offset by the lower energy and running costs. If electricity, oil, LPG or coal are replaced the savings will be more favourable than gas.
Since the majority of the heat requirement is derived from the ground around a property it is under the control of the property owner and is free from future price rises – offering greater energy security.
Reverse-cycle heat pumps are available that can deliver both heating and cooling.
Factors to consider Ground source heat pumps typically have higher efficiencies than air source heat pumps. This is because they draw heat from the ground or groundwater which is at a relatively constant temperature all year round. This means that the temperature differential is lower, leading to higher efficiency. The trade off for this improved performance is that a ground source heat pump often has higher costs to install and needs more land due to the need for the drill bore hole or trenches in which to place the pipes that carry the heat exchange fluid. Planning permissions are Heat pumps provide one of the most cost and energy-effective forms of exploiting also needed. renewable energy. A typical 8 – 12 kilowatt ground source heat pump from Crestra costs £6,000 - £10,000 installed (not including the price of a distribution system). This can vary with property, system size and location. Boreholes for vertical ground loop systems are considerably more expensive to install than horizontal ground loops. Crestra will advise on all the options available. According to the Energy Savings Trust (EST) the prospective financial and carbon savings from installing a ground source heat pump in a detached property to provide 100% of space heating requirements are as follows:
Fuel Displaced
Ground source (also providing 50% of hot water requirement) Potential saving per year
CO2 saving per year
£410
1.2 tonnes
Electricity
£1000
7 tonnes
Oil
£750
1.8 tonnes
Solid
£350
6.5 tonnes
Gas
These are historical figures and need to be treated as conservative financial savings.
ground source heat pumps
Costs and savings
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Sustainable drainage and ground source heat pumps Sustainable Drainage is an environmentally-friendly way of dealing with surface water runoff which avoids the problems associated with conventional drainage practice. Conventional drainage exacerbates flooding, causes pollution and is generally more expensive to install and to maintain than Sustainable Drainage schemes. Crestra uses the Hanson Formpave Aquaflow Sustainable Urban Drainage System which allows rain to infiltrate through a permeable block paving surface into a unique sub-base and collect in a tanked area. This can then be combined with piping connected to a ground source heat pump. In effect, this creates a water source heat pump on land which is potentially the most efficient type of heat pump available.
Will it work for you? For new buildings - A ground source heat pump system would be appropriate for most new buildings in the UK that meet or exceed the 2006 Building Regulations that require higher levels of insulation and draft control; which means that the size of heat pump can be smaller with shorter ground loops. For older properties - Heat loss is major issue in the case of older buildings where increasing the levels of insulation can then allow significant savings on the capital cost of a heat pump system. Unfortunately, many older buildings present difficulties in terms of access to lay the ground loop, they may be difficult to insulate and it may be impossible, or at least prohibitively expensive to introduce low temperature underfloor heating, or low temperature radiators.
Why Crestra?
Crestra Ltd is a wholly-owned trading subsidiary of Groundwork Creswell, Ashfield and Mansfield (GCAM), an environmental regeneration charity
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dedicated to helping generate and sustain vibrant, healthy and safe communities. GCAM has been actively working to improve the environment since 1990 and now
ground source heat pumps
annually carries out around £4 million of environmental work.
Our systems are designed with a long lifetime and low maintenance requirement.
We are a quality orientated company that cares about the environment and as such we are accredited to BS 8555 Environmental Management.
Our trained engineers will offer an efficient installation service with as little disruption to the household as possible and no mess left behind.
Crestra Limited 96 Creswell Road Clowne Chesterfield Derbyshire S43 4NA Tel: 01246 570977 Fax: 01246 813200 Website: www.crestra.co.uk O
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