Designing an Open Loop Ground Source Energy System
A successful Ground Source Energy (GSE) system provides a renewable energy solution to a buildings heating and cooling needs. These benefits depend on a reliable and efficient design of the ground loop energy source.
For the system to be successful it is important that the ground loop design and size matches the profile of energy use for the building. ESI can provide the specialised skills and knowledge to ensure that the proposed ground loop size matches these needs, taking into account the balance between winter heating and summer cooling.
At sites with adequate groundwater flow beneath them, or a sufficiently large stream or lake, open loop ground source energy systems can offer significant efficiency gains over closed loop systems.
Initial Site Check
ESI’s initial Site Check can identify the options available for an effective system to be developed. This initial low cost desk study based on a postcode and site plan will provide typical values of key hydro-geological and thermo-geological parameters for the site's location. At this early stage it is likely that ESI will give an indication of the closed loop or open loop options available for the site and an indication of the size of ground loop required. If an open loop solution is chosen, it is strongly recommended that further specialised hydrogeological advice is commissioned.
The main objectives associated with the technical design of open loop schemes are:
- Confirmation that the required flow rate can achieved from the abstraction well and discharged back to the aquifer
- A borehole design that is appropriate for the abstraction and reinjection to minimise the risks of borehole clogging and loss of performance
- For the wells to be spaced sufficiently far apart to reduce the risk of thermal breakthrough
A hydrogeological conceptual model is a key foundation to good open loop Ground Source Energy design. ESI has many years of experience working in all the UK aquifer settings and is ideally placed to develop appropriately detailed site models. Detailed modelling of the long-term performance of the system will then inform and support ESI's system design, ensuring the objectives are met through the appropriate location and specification of boreholes and their flow rates.
Regulatory approval will also be required from the Environment Agency to investigate the aquifer, abstract groundwater, and discharge groundwater back to the aquifer. Whilst the Environment Agency is supportive of renewable energy schemes, they will need to be satisfied that appropriate precautions are being taken to ensure no pollution or derogation of the aquifer occurs. Details of the well design and the thermal impact of the scheme must be presented to the Environmental Agency to obtain regulatory approval. ESI’s track record of working with the Environment Agency will help ensure a smooth and efficient regulatory process.
It is likely the following services will be required prior to the design and installation of an open loop scheme, by completing each stage in the right order any potential problems are identified at an early stage allowing an informed decision on how to proceed can be made.
