Feasibility Study for a GSE System

Case Study

A property owner was seeking to realise the benefits of a ground source energy (GSE) scheme for heating and cooling a house in Somerset. ESI was commissioned by Isoenergy to review the geological, hydrogeological and thermogeological conditions of the site and to assess the feasibility of such a scheme. Geological and hydrogeological data was obtained from relevant authorities and institutions. The data was used to develop a hydrogeological and thermogeological conceptual model of the site.

ESI’s client was seeking to realise the benefits of a ground source energy (GSE) scheme for heating and cooling a property in Somerset. ESI was commissioned by Isoenergy to review the geological, hydrogeological and thermogeological conditions of the site and to assess the feasibility of such a scheme. Geological and hydrogeological data was obtained from relevant authorities and institutions. The data was used to develop a hydrogeological and thermogeological conceptual model of the site.

 

The site of the property lies to the north of Bath, in a geologically complex area where the Foundered Strata is found. This geological environment is known to be challenging from an engineering point of view and there have been landslides along the valley sides.

 

The instability arises where the very strong Jurassic limestone (Great Oolite) strata overlies weaker calcareous mudstone (Fuller’s Earth). The hydrogeology of the area was identified as being of relatively high groundwater vulnerability due to the presence of several springs and groundwater abstraction boreholes used for public water supply. Consequently, a potential risk to groundwater was identified, resulting from the discharge of refrigerants from the borehole heat exchanger. However, the site is located on less permeable formations and it was anticipated that the hydrogeological conditions were unlikely to represent any unacceptable risk to these receptors.

 

Significant borehole instability was also identified due to the risk presented by Foundered Strata. To compensate for this instability, suitable drilling methods were recommended. The conclusion of ESI’s review was that the geological formation would not sustain the groundwater yields required for an open loop GSE scheme, and a closed loop GSE scheme was therefore recommended.

 

One of the issues identified by the feasibility study was the lack of good geological, hydrogeological and thermogeological data. Geological borehole logging and a thermal response test were proposed as the main data priorities that needed to be addressed before the GSE design could be finalised.

 

Following the release of the final report for the feasibility study, the client commissioned ESI to carry out a thermal response test.