GROUND SOURCE HEAT PUMPS Energy extracted from the earth to provide central heating & hot water
What is a ground source heatpump?
A ground source heatpump is a device which extracts naturally produced energy from the ground and converts it into useful heat warm enough to provide your central heating and domestic hot water.
How does it work?
The key ingredient in all heatpump technology is a refrigeration circuit. Energy is extracted from the ground using buried pipework (see different collection methods) and circulated through a heat exchanger called an evaporator. In the other half of the evaporator is the refrigeration circuit which is heated by the energy collected from the ground. The refrigerant is then compressed which produces a superheated refrigerant and this superheated refrigerant then passes through a second heat exchanger called a condenser. On the other side of the condenser is our central heating water. The heat produced from the compressed refrigerant gas is transferred through the condenser into the central heating water, heating it enough to run your radiators / underfloor and provide domestic hot water.
As the heat transfer takes place, the refrigerant is cooled and then passes through an expansion valve which changes its state back to a vapour and the pressure is reduced. The process can then begin again.
Ground Collection Methods
There are many ways to collect energy from the ground. The most common used are either closed loop collector pipes or boreholes.
Closed Loop Collector Pipes
This method is the most common way of extracting heat however will require a large area of ground to accommodate the collector pipes. The pipework is laid in trenches 1mtr deep and 1mtr apart. The pipework is filled with a mixture of antifreeze and water and circulated through the pipework absorbing the energy required to heat the refrigerant circuit.
It is vital that the collector pipework length is correctly sized and installed to the correct depth and spacing as an incorrectly installed loop can result in ground freezing and high running costs.
Where there is not enough space for a ground collector, the borehole method could be considered. The depth of borehole needed will depend upon the type of ground to be drilled and the size of the building being heated. A geological survey will allow the designer to correctly size the amount of borehole depth required.
There are many factors to consider before proceeding with a borehole such as ground conditions, water table level and containment. As such this work is always completed by a specialised borehole contractor and a geological survey must always be carried out.
COP (Co-efficient of Performance)
The heatpumps design efficiency is usually stated as the Co-efficient of Performance or COP and is calculated at a specific operating condition. The industry standard conditions are Brine Temperature (water and antifreeze) in the ground loop of 0Deg c and the output water temperature at 35Degc. Typically at these conditions a ground source heatpump would normally have a COP of around 4 (400% efficient). This means that for every kilowatt used to power the heatpump 4 kilowatts is delivered into the building. This figure will vary depending upon the heatloss of the property.
Other Changes to Factor into Your Decision
For a heatpump to work efficiently and for it to live up to expectations, it is essential that the buildings fabric insulation is taken into consideration. As a minimum, the property ideally needs to be double glazed with a decent level of roof insulation, cavity wall / internal/external wall insulation and if possible floor insulation.
When in heating mode, the heatpump works on low water temperature ideally around 40 - 45Deg c and therefore all heat emitters need to be sized accordingly.
This generally does not present too much of an issue where underfloor heating is concerned, however if the property had existing radiators and was previously fed from a gas or oil boiler, the chances are they will need to be replaced and upsized to cope with the heatpumps lower water temperature.
The same is required where the hot water cylinder is concerned. If existing hot water cylinder was previously heated by a gas or oil boiler, this will also need upgrading to one with a larger internal coil suitable for the heatpumps lower water temperature. The heatpump will naturally heat the water in the cylinder to around 55Deg c with no additional back up.
Please Note: All ground source heatpumps are fitted with a 3kw element (like an immersion heater). This is generally used for pasteurisation (Legionella protection) whereby the water in the cylinder is taken up to 60Deg c and held for a period of time (generally up to an hour) before switching off.
Finally, is there sufficient space to site the internal ground source heatpump components. The heatpump is the physical size of a fridge freezer and most installations have a buffer cylinder fitted alongside the heatpump and the cylinder sited next to the buffer. Ideally a minimum space of 1500mm x 600mm is required to house all equipment, although it is possible to separate if insufficient space is available.
So Why Purchase a Ground Source Heatpump?
If you are building or renovating a property and live in an off grid location with a decent amount of garden, then a ground source heatpump is the perfect solution.
Its High Efficiency
Low on Energy Consumption
Low Running Costs
Low Carbon Emissions
Low Noise (lower than an air to water heatpump as no fan)
Long Life (ground collector should last a minimum of 50 years)
Government Financial Incentives available
Air Management Solutions also offer a competitively priced maintenance package which covers your annual service (Please contact the office for more details). We will automatically contact you when due to arrange a suitable time and date to attend.
We also offer a standard and emergency breakdown service for heatpumps installed by us and also by others.
Our fully certified and qualified team are committed to ensuring all our customers needs are met offering a highly skilled, professional, efficient and cost effective service tailored to your individual needs. And you can rest assured that all work is fully guaranteed.