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Photo of a heat collector in a trench Ground Source Heat Pumps | How it works | Is it suitable for my home? | FAQ

Ground Source Heat Pumps

Converting energy in the ground into low cost heating and hot water for your home.

A ground source heat pump is an electrically powered system that taps into the natural energy stored in the earth to heat your home. The systems we supply can provide all of your heating and hot water needs. The principle is simple, and the result is low-cost comfortable heating that uses sustainable energy and causes no direct emissions or other damage to the environment. For every single kilowatt of electricity used to power the heat pumps, this system could generate four kilowatts or more of heat for your home.

The different types of ground source collectors:

Horizontal CollectorCompact CollectorBore Hole Collector

What's more, it also helps to conserve the earth's dwindling supplies of non renewable fossil fuels; coal, gas and oil. Heat pumps are extremely reliable and long lasting with a typical system lasting up to 25 years and the ground pump lasting up to 50 years. We are also giving a free 5-year part and labour manufacturers warranty on all systems fitted by F.G.Welch Central Heating & Gas Services Ltd.

There's more good news. You could also qualify for a government grant towards the cost of installation under its Low Carbon Buildings Programme.

The benefits

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 for the ground loop. Average CoP over the year, known as seasonal efficiency, is around 3-4 although some systems may produce a greater rate of efficiency. This means that for every unit of electricity used to pump the heat, 3-4 units of heat are produced, making it an efficient way of heating a building. If grid electricity is used for the compressor and pump, then you should consult a range of energy suppliers to benefit from the lowest running costs, for example by choosing an economy 10 or economy 7 tariff

Costs and savings

A typical 8 - 12kW system costs £6,000 - £12,000 (not including the price of distribution system). This can vary with property, system size and location. Vertical ground loop systems are significantly more expensive to install than horizontal ground loops, due to the higher cost of drilling a borehole. When installed in an electrically heated home a ground source heat pump could save as much as £1000 a year on heating bills and almost 7 tonnes of carbon dioxide a year. Savings will vary depending on what fuel is being replaced.

Fuel Displaced£ Saving per yearCO2 saving per year
Gas£4101.2 tonnes
Electricity£10007 tonnes
Oil£7501.8 tonnes
Solid£3506.5 tonnes

Savings above assume ground source heat pump installed in a detached property and provides up to 50% of domestic hot water as well as 100% of space heating.

How it works

There are three important elements to a ground source heat pump:

1) The ground loop

This is comprised of lengths of pipe buried in the ground, either in a borehole or a horizontal trench. The pipe is usually a closed circuit and is filled with a mixture of water and antifreeze, which is pumped around the pipe absorbing heat from the ground. The ground loop can be:

  • Vertical, for use in boreholes
  • Horizontal, for use in trenches
  • Spiral, coil or ‘slinky', also for use in trenches

2) A heat pump

In the same way that your fridge uses refrigerant to extract heat from the inside, keeping your food cool, a ground source heat pump extracts heat from the ground, and uses it to heat your home. A ground source heat pump has three main parts:

  • The evaporator, (e.g. the squiggly thing in the cold part of your fridge) absorbs the heat using
  • the liquid in the ground loop
  • The compressor, (this is what makes the noise in a fridge) moves the refrigerant round the heat
  • Pump and compresses the gaseous refrigerant to the temperature needed for the heat distribution circuit
  • The condenser, (the hot part at the back of your fridge) gives up heat to a hot water tank which feeds the distribution system.

3) Heat distribution system

This consists of under floor heating or radiators for space heating and in some cases water storage for hot water supply.

Is it suitable for my home?

You should consider the following issues if you're thinking about installing a ground source heat pump. An accredited installer will be able to provide more detailed advice.

  • You will need space outside your house for the ground loop.
  • The ground will need to be suitable for digging a trench or borehole.
  • What fuel is being replaced? If it's electricity, oil, LPG or coal the savings will be more favourable than gas. Heat pumps are a good option where gas is unavailable.
  • The type of heat distribution system. Ground source heat pumps can be combined with radiators but these will normally be larger than with standard boiler systems. Under floor heating is better as it works at a lower temperature.
  • Want to further reduce your home's carbon dioxide emissions? Install solar PV or some other form of renewable electricity generating system to power the compressor and pump.
  • Is the system for a new building development? Combining the installation with other building works can reduce costs.
  • Have you installed insulation measures? Wall, floor and loft insulation will lower your heat demand and make the system more effective.

Frequently Asked Questions

What is sustainable energy?

Sustainable energy is best thought of as energy which can be replenished within a human lifetime and which causes no long-term damage to the environment.

Solar energy, wind energy and geothermal energy, amongst others are all self sustaining. They all have sources that cannot be depleted. Extended use of these energy aids the conservation of other non-renewable energy sources such as fossil fuels.

How does a heat pump work?

The technology inside a heat pump works on similar principles to those of a domestic fridge. Heat pumps take advantage of the principles of thermodynamics in order to achieve their results. A water and glycol mixture is pumped around the collector circuit and causes the refrigerant in the evaporator to turn into a gas. This refrigerant passes through the compressor, causing the temperature to rise significantly. The hot gas moves to the condenser, where it condenses and the latent energy is released into the heating circuit.

How is energy collected from the ground?

There are three options to obtain energy from the ground. In a horizontal collector, lengths of pipe are buried underground to a depth of 1 metre. This is a good solution if the property in question has enough land to accommodate the collector. Worcester offer compact collectors which reduce the amount of space required for the collector by increasing the amount of pipe work in a given area. An alternative to the horizontal collector types is the vertical collector. A bore hole is drilled to a depth of between 60 and 200 metres, and the collector is fed into the hole. A vertical collector minimises the amount of land required on the surface of the collector.

What type of heat pumps will be available?

Worcester will launch a range of three system heat pump models for use with an external cylinder.

Will I also need a boiler with the system?

In the majority of circumstances, the answer is no. Worcester's system is all you need to satisfy your total heating and hot water requirements. However, F G Welch Central Heating & Gas Services Ltd will advise you on your individual situation.

Can I keep my existing radiators?

Ideally, for maximum benefit and efficiency, a heat pump is best used with underfloor heating, but oversized radiators are also a practical option.

What is COP?

It stands for Coefficient of Performance and it relates to the amount of energy extracted from the ground for each unit of energy used to run the pump.

A heat pump could provide between 3-5kW of heat for each kW of electricity used. The return varies according to the temperature of the heat collected and the heat required to heat your property.

For example; 3kW of heat is provided by the pump and 9kW of heat is provided by the ground source, making a total of 12kW. To calculate the COP, divide the total (12kW) by the amount provided by the heat pump (3kW). This gives a COP of 4.

Am I entitled to a grant towards the cost of installing a heat pump system?

The government is actively encouraging the use of sustainable energy domestic heating systems, and under the Low Carbon Buildings Programme you can apply for a grant.

For more information call F.G.Welch Central Heating & Gas Services Ltd on 01257 421 660 today.

photo of a boiler and the three methods of installing collectors