What Is a Ground Source Heat Pump?
A Ground Source Heat Pump or a Geothermal Heat Pump is an eco-friendly and energy efficient central heating/cooling system for meeting the households demands in terms of thermal capacity that these require. If you are interested in installing a GSHP at home, you can fill in the contact form on the right to receive customized quote from our qualified suppliers, for free.
The principle behind the functioning of a geothermal heat pump is based on a heat exchange process, where the soil’s accumulated heat is being transferred to the pump. The solar energy that heats the Earth’s crust is being absorbed by the ground’s upper layer, which most of the time registers constant temperatures, regardless of the weather conditions outside. A network of underground pipes collect the soil’s heat, which later through a process of compression, evaporation or condensation is being transferred and released into people’s houses.
Information About Ground Source Heat Pump Borehole
When considering installing a ground source heat pump one could choose between a network of horizontal collectors laid in the immediate proximity to the ground’s upper layers at small depths, or opt for vertical boreholes instead, which are also known as vertical closed-loop geothermal heat exchangers. Selecting between these two systems, conceptually similar but structurally different, comes down to the available space for a geothermal pump installation, the square footage that requires heating and the budget allowance one can sanction for carrying the installation works.
Vertical boreholes are good for small or limited areas, and although it bears high installation costs, borehole heat collectors produce a higher heat yield per metre, compared to horizontal collectors, which entails a better energy efficiency rate. Thus, if you are considering drilling a borehole in your backyard, you’ll have to make sure that the ground is suitable for digging a deep-seated ditch and that the designated area is accessible for fitting in the drilling equipment.
What is a Ground Source Heat Pump Borehole?
A borehole type heat pump represents a closed loop system which comprises a set of polyethylene pipes that are vertically inserted into the ground and which circulate water to and from the geothermal heat pump. In most cases, the borehole size will range between 15m and 122 m (50-400 feet) deep.
The space between the pipes and the borehole wall is filled up with a special grout mix that typically contains a combination of bentonite, sand and potable water, which is being pumped from bottom to top. Bentonite is preferable to other grouting materials, since it is waterproof and a good thermal conductor. Therefore, by retaining a considerable amount of moisture it rarely dries out which ensures a proper heat transfer from the ground to the pipe and vice versa. At the same time, due to its low permeability properties, the bentonite grout provides a self-sealing barrier to groundwater intrusion. The boreholes are drilled at 5-6 m apart from each other and at 6-7 m from the nearest building. The depth is conditional on the property’s characteristics (size, insulation, heating capacity) that requires heating. A house that needs around 10 kW of heating capacity, most probably will need three boreholes of 80 to 110 m deep.
Borehole Collectors Installation and Operational Costs
The costs associated with a borehole heat pump installation are directly proportional on such factors as borehole depth, borehole casing and sealing materials dimensions. In order to make sure that you will make the most out of the boreholes you are planning to drill, you can order a geotechnical survey to be carried out beforehand.
In so doing, you’ll be able to minimise the degree of uncertainty when it comes to the soil’s thermal properties assessment and it will make sure that the heating capacity you are looking to obtain by installing a ground source heat pump will pay off the initial investment. At the same time, a survey like this will provide a reliable amount of data that will be instrumental in planning the right length and diameter of the borehole loop, that will correspond with the ground’s characteristics.
The smaller the system, the higher the cost per kW output will be. As mentioned earlier, for all the types of ground source heat pumps that use a borehole as their main heat source collector, the setting up costs (planning, equipment utilisation and the commission of works) are a substantial part of the total costs. Thus, the capital cost measured in pounds per borehole meter that is being drilled, will decrease as the collector size increases.
This means that, for a group of ten houses which are located on the same site, the borehole collector costs per house will be around 20% lower than for an individual house. Meanwhile, the overall costs of the heat pump that determines its’ output in terms of pounds per kW, will drop as well, provided that the heat pump output gets larger.
If you wish to receive customized information about the cost of a ground source heat pump for your specific property, fill in the contact form at the top of the page. Our team will contact you for further information and will connect you with our qualified suppliers, for free.