Andreas Ramsauer of landscape company Earth Heat Landscapes explains ground source heat pumps and their numerous benefits
To reach the new Government targets on reducing UK carbon dioxide emissions there will need to be a major shift in the way we heat our homes and move away from gas and fossil fuels to alternatives such as heat pumps. This article will propose how the landscape industry could play a vital role and take advantage of the potential new boom in designing and installing the ground source heat pump systems.
The Ground Source Heat Pump Association says there has been, up to now, a much lower uptake of low carbon technology than expected and by the end of 2019 only 4.5% of domestic properties use a low carbon source. The market is still dominated by gas boilers, with 1.6m being installed in a year against 50k heat pumps since 2014. This is despite the technology being around for 20 years.
Why has the uptake been so slow? This can possibly be explained by high capital costs and installation being potentially disruptive internally and externally. Uncertain returns as historically Government policy and strategy unclear with people only installing renewable technology if there is a strong financial incentive to do so. There is also a large amount of initial survey and upfront costs.
The market for low carbon technology is about to change with some strong incentives.
From 2025 new gas boilers cannot be installed in new homes, so alternatives will need to be considered fairly soon. One alternative are air source heat pumps but these may require planning or have restrictions on installation, are considered noisy, less efficient and attract a lower incentive from the Government. The ground source heat pump, however, attracts a larger government grant, is more efficient, and is installed in the ground. With the heat pump inside the house it may well assist in more favourable planning application outcome than an air source pump. Also, with a property that has a GSHP already installed, this could well increase the value of the property as the market changes.
How does a ground source heat pump work?
The sun has heated the ground for hundreds of thousands of years and this low grade heat can be transferred by the use of heat pumps to provide the heating and hot water for the home. The temperature in the ground is constant throughout the year at depth, providing heat energy even in the winter. The heat is collected from the ground by a variation of methods including horizontal loops in trenches, vertical boreholes, lakes or even rivers and streams, depending on space and location. This heat is passed to a heat pump which will convert this to a usable heat and then to the emitters in the house such as under floor heating, enlarged radiators and hot water.
The only electrical energy being used is for the pumps and the compressor in the heat pump (very much like a fridge) and in a well designed system the performance can be as much as four units of heat to one unit of electricity.
The heat pump can also be used in reverse which can then be used to cool the house and heat can be returned to the ground.
Where does the landscape industry come in?
Is it time we re-thought how we look at our landscapes and landscape design? Instead of just looking at the aesthetic or the practical, we should view our landscape and gardens as a resource for heat and even carbon capture. As well as a nice place to be, the landscape can be a used to help with our battle with climate change and the reduction of carbon dioxide emissions.
By involving a knowledgeable landscape designer at the early stages to include the collection loops or boreholes these can be incorporated in the overall landscape design. This will create a more efficient collector system and improved construction process. Also, if considered at the planning stage this could very likely provide a more favourable application outcome.
Landscaping is often overlooked during a refurbishment or in new build projects and can perhaps be just lawned areas, possibly new trees or patios. There is usually a much smaller budget given to this part of the works and it is one of the last trades on site. The landscape design should however be considered at the beginning of the process. As well as the usual aspects of landscaping we should also be looking at the heating of the house itself as part of the landscape design and planning process.
Heat pump technology is well established in the UK but is not always installed as it is either considered too late in the project, not thought of at all, too disruptive or even too expensive. However, to overcome the barriers associated with the installation, the landscape designer needs to be consulted at an early stage of the project. With thoughtful design, the collector system can be incorporated into the available space required for the ground loop array, positioning of boreholes and trenches, or even the construction of a lake. There may also be the possibility in developments of more than one house to install communal boreholes or ground arrays to maximise space efficiency. If the collector system is considered at the end of the project it may be too late, as the house might already be built or the ground works completed. It would be far less disruptive and less costly to undertake the collector construction at the same time as the ground works.
Apart from the horizontal ground loops shown in the photographs there ae the options of vertical boreholes, lakes and ponds as well as possibly rivers and streams as heat collectors.
Process and surveys
The heating engineer will calculate the heat load requirements for the house which is based on heat loss calculations and will measure the size of rooms, building fabrics, insulation and building location. From these calculations the collector system can be designed to match the heat load requirements given by the heating engineer. The design of the collector will vary according to the site’s location in the country as ground temperatures can vary depending where you are. The ground and geology plays a major part in the design consideration as different ground types will give different heat transfer. For example, dry sand or chalk will give a much lower heat than clay or saturated sand. The presence of water in the ground will also significantly affect the heat transfer to the collector system as heat conducts better in saturated ground. The landscape designer will also need to look at the area of the plot and will be able to assess at an early stage whether a ground loop or vertical boreholes are to be installed. It may also be possible that the area already has a lake in place or there is sufficient space to construct one from which heat can be extracted. The design of the garden can therefore form part of the overall design.
Detailed surveys will be required to come up with the optimum collector system. The surveys will consist of the production of area plans and topography, thermal probe tests at various positions, desktop study of geology and potential heat conductivity, position of utilities, access consideration for plant such as drilling rigs, thermal response tests for borehole installations. These detailed surveys can be used to overlay the ground loop array or position of boreholes.
There are cost savings from shared survey work, design work, mobilisation of groundwork crews. The making good of the installation can also be in the design and to cover the trenches but also look at the position of paving, paths, driveways and planting to maximise heat collection. The design will also need to consider maintenance of the system over it’s lifetime and access maybe required to the pipes and manifolds so positioning of trees and shrubs will need be part of the design.
Position of trees and canopy cover, drainage, area of hardstanding, access to manifolds, area of paving, streams, rivers and lakes can all be incorporated within the scheme. Areas of open space and even playing fields can also provide excellent areas that can provide heat and have a dual function.
Ground source landscape designs
At Earth Heat Landscapes, we will give the landscape designer the assistance or produce schemes which will incorporate the ground collector part of the ground source heat pump design. We can assist with initial survey work including land surveys (which need to be accurate), heat probe surveys for horizontal ground loops, overlay and positioning of ground array to fit space, advice on options for heat, look at borehole and ground information, understanding heat loss calculations from heating engineers. We also have connections with Hydrologists, Heating Engineers and Installers who will be required during the design and installation process.