Operational Response of a Soil-Borehole Thermal Energy Storage System

AbstractThis study focuses on an evaluation of the subsurface ground temperature distribution during operation of a soil-borehole thermal energy storage (SBTES) system. The system consists of an array of five 9 m-deep geothermal heat exchangers, configured as a central heat exchanger surrounded by four other heat exchangers at a radial spacing of 2.5 m. In addition to monitoring the temperature of the fluid entering and exiting each heat exchanger, 5 thermistor strings were embedded in boreholes inside and outside of the array to monitor changes in ground temperature with depth. After 75 days of heat injection at a constant rate of 20  W/m, corresponding to 11.5 GJ of thermal energy, the average ground temperature in the array increased by 7°C. However, depending on the storage volume definition, only 2.43–4.86 GJ of thermal energy was stored attributable to heat losses. After a 4-month rest period the heat storage was observed to decrease by 60% owing to further heat losses. The trends in subsurface temp...

[1]  K. D. Murphy,et al.  Impact of Horizontal Run-Out Length on the Thermal Response of Full-Scale Energy Foundations , 2014 .

[2]  Michel Bernier,et al.  SEASONAL STORAGE OF SOLAR ENERGY IN BOREHOLE HEAT EXCHANGERS , 2009 .

[3]  Yu-Shu Wu,et al.  Efficiency of a Community-Scale Borehole Thermal Energy Storage Technique for Solar Thermal Energy , 2012 .

[4]  Per Eskilson.  Thermal analysis of heat extraction boreholes , 1987 .

[5]  Stanislaw Kajl,et al.  A review of methods to evaluate borehole thermal resistances in geothermal heat-pump systems , 2010 .

[6]  H. Brandl.  Energy foundations and other thermo-active ground structures , 2006 .

[7]  John S. McCartney,et al.  Development of a Full-Scale Soil-Borehole Thermal Energy Storage System , 2015 .

[8]  Bill Wong,et al.  The Performance of a High Solar Fraction Seasonal Storage District Heating System – Five Years of Operation☆ , 2012 .

[9]  R. Beier,et al.  Borehole thermal resistance from line-source model of in-situ tests. , 2002 .

[10]  J. Spitler,et al.  In Situ Measurement of Ground Thermal Conductivity: A Dutch Perspective , 2002 .

[11]  P. Mogensen.  Fluid to duct wall heat transfer in duct system heat storages , 1983 .

[12]  John P. Millhone,et al.  New Energy Conservation Technologies and Their Commercialization , 1981 .

[13]  L. Schiavi.  3D Simulation of the Thermal Response Test in a U-tube Borehole Heat Exchanger , 2009 .

[14]  B. Palm,et al.  Distributed thermal response tests on pipe-in-pipe borehole heat exchangers , 2013 .

[15]  L. Gosselin,et al.  Borehole temperature evolution during thermal response tests , 2011 .

[16]  L. Rosenhead.  Conduction of Heat in Solids , 1947, Nature.

[17]  N. Lu.  An analytical assessment on the impact of covers on the onset of air convection in mine wastes , 2001 .

[18]  J. Claesson,et al.  Model Studies of Duct Storage Systems , 1981 .

[19]  S. Gehlin.  Thermal response test : method development and evaluation , 2002 .

[20]  Göran Hellström,et al.  High temperature solar heated seasonal storage system for low temperature heating of buildings , 2000 .