G-Functions for multiple interacting pile heat exchangers

Pile heat exchangers – where heat transfer pipes are cast into the building piled foundations – offer an opportunity to use ground energy systems without the additional construction costs related to the provision of special purpose heat exchangers. However, analysis methods for pile heat exchangers are still under development. In particular there is an absence of available methods and guidance for the amount of thermal interaction that may occur between adjacent pile heat exchangers and the corresponding reduction in available energy that this will cause. This is of particular importance as the locations of foundation piles are controlled by the structural demands of the building and cannot be optimised with respect to the thermal analysis. This paper presents a method for deriving G-functions for use with multiple pile heat exchangers. Example functions illustrate the primary importance of pile spacing in controlling available energy, followed by the number of piles within any given arrangement. Significantly it was found that the internal thermal behaviour of a pile is not influenced appreciably by adjacent piles.

[1]  Fleur Loveridge,et al.  Pile heat exchangers: thermal behaviour and interactions , 2013 .

[2]  Rui Fan,et al.  Theoretical study on the performance of an integrated ground-source heat pump system in a whole year , 2008 .

[3]  Saffa Riffat,et al.  An investigation of the heat pump performance and ground temperature of a piled foundation heat exch , 2010 .

[4]  Xu Zhang,et al.  Thermal performance and ground temperature of vertical pile-foundation heat exchangers: A case study , 2008 .

[5]  Saffa Riffat,et al.  Comparison of a modelled and field tested piled ground heat exchanger system for a residential building and the simulated effect of assisted ground heat recharge , 2010 .

[6]  Fleur Loveridge The thermal performance of foundation piles used as heat exchangers in ground energy systems , 2012 .

[7]  Daniel Pahud,et al.  Mesures et optimisation de l’installation avec pieux énergétiques du Dock Midfield de l’aéroport de Zürich. Rapport intermédiaire , 2006 .

[8]  G. Hellström,et al.  EXPERIENCES WITH THE BOREHOLE HEAT EXCHANGER SOFTWARE EED , 2004 .

[9]  YaoYang,et al.  Theoretical study on the performance of an integrated ground-source heat pump system in a whole year , 2008 .

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

[11]  Fleur Loveridge,et al.  Performance of piled foundations used as heat exchangers , 2013 .

[12]  Alvin C.K. Lai,et al.  New temperature response functions (G functions) for pile and borehole ground heat exchangers based on composite-medium line-source theory , 2012 .

[13]  Enzo Zanchini,et al.  Long-term performance of large borehole heat exchanger fields with unbalanced seasonal loads and groundwater flow , 2012 .

[14]  Michele De Carli,et al.  Long-term performance of an irregular shaped borehole heat exchanger system: Analysis of real pattern and regular grid approximation , 2012 .

[15]  Yasuhiro Hamada,et al.  Field performance of an energy pile system for space heating , 2007 .

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

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

[18]  Fleur Loveridge,et al.  Temperature response functions (G-functions) for single pile heat exchangers , 2013 .

[19]  Göran Hellström,et al.  Comparison between theoretical models and field experiments for ground heat systems , 1983 .

[20]  Hongxing Yang,et al.  A new model and analytical solutions for borehole and pile ground heat exchangers , 2010 .

[21]  John W. Lund,et al.  Direct utilization of geothermal energy 2010 worldwide review , 2011 .

[22]  Louis Lamarche,et al.  A new contribution to the finite line-source model for geothermal boreholes , 2007 .

[23]  Andreas Zell,et al.  Optimization of energy extraction for closed shallow geothermal systems using linear programming , 2012 .

[24]  Atsushi Okamoto,et al.  Calculation algorithm of the temperatures for pipe arrangement of multiple ground heat exchangers , 2009 .

[25]  Daniel Pahud,et al.  PILESIM2: Simulation Tool for Heating/Cooling Systems with Energy Piles or multiple Borehole Heat Exchangers , 2007 .

[26]  Yu Yue-jin,et al.  Research Status and Progress of Ground-Coupled Heat Pump System Simulation , 2009 .

[27]  O. J. Zobel,et al.  Heat conduction with engineering and geological applications , 1948 .

[28]  Andreas Zell,et al.  Geometric arrangement and operation mode adjustment in low-enthalpy geothermal borehole fields for heating , 2013 .

[29]  G. Hellström Ground heat storage : thermal analyses of duct storage systems , 1991 .

[30]  Katsunori Nagano,et al.  Method of Calculation of the Ground Temperature for Multiple Ground Heat Exchangers , 2008 .