Long-term high frequency monitoring of a large borehole heat exchanger array

• Published in: Renewable energy 2020-01, Vol.145, p.1528-1542
• Main Authors: Naicker, Selvaraj S., Rees, Simon J.
• Format: Article
• Language: English
• Subjects: Borehole heat exchanger; geothermal; Monitoring; Validation
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2019.07.008

Borehole heat exchangers are a key technological element of geothermal energy systems and modelling their behaviour has received much attention. The aim in the work reported here has been to produce a reference data set that can be used in analysis of large borehole heat exchanger systems and validation of models of such. A monitoring exercise to collect high frequency data from a large ground heat exchanger array consisting of 56 boreholes over 38 months since the start of operations is reported. The system is associated with a mixed-use university building that has both heating and cooling loads. Ground heat exchange was found to be dominated by rejection of heat over the monitoring period and modest seasonal increases in temperatures. The ground heat exchanger installation has been additionally characterised by analysis of thermal response test data to estimate the effective ground and grout thermal properties. The utility of the measurements as a reference data set by presenting a model validation study is furthermore demonstrated. This has highlighted some features of the data that are more significant in systems of larger scale. These reference data are being made openly available for further work on performance analysis and model validation. •A large scale geothermal heating and cooling system has been monitored.•A detailed data set has been developed with high---frequency measurements.•Data is being made available from 38 months of monitoring.•Discussion of characterisation by TRT analysis is presented.•Application to a model validation exercise is presented and unique features of large system behaviour identified.