Building Services Engineering CHALMERS OPTIMIZATION OF GROUND COUPLED HEAT PUMP SYSTEMS Saqib Javed (PhD Researcher) Per Fahlén (Research Leader) Johan Claesson (Supervisor) EFFSYS 2 meeting Akademiska Hus Carrier CTC / Enertech Donghua University Fastighetsägarna Geotec Grundfos IVT LTH NCC Nibe SWECO TAC Thermia Värme Wilo ÅF-Infrastruktur

Building Services Engineering CHALMERS Identifying key optimization factors for Ground Coupled Heat Pump (GCHP) systems using modelling, simulations field studies and experiments. Developing simple and user-friendly models and calculation tools to facilitate designers and researchers interested in the complete system optimization. OBJECTIVE EFFSYS 2 meeting

Building Services Engineering CHALMERS LITERATURE REVIEW EFFSYS 2 meeting Single boreholes: Long term response can be modelled using simple existing analytical models with reasonable accuracy. Multiple boreholes: Shortage of analytical models for both long and short term response. Need of an analytical model which: -is capable of simulating both short-term and long-term response of GHE. -considers all significant heat transfer processes in GHE. -retains the actual geometry of the borehole.

Building Services Engineering CHALMERS CASE STUDY EFFSYS 2 meeting Astronomy-House, Lund University  Floor area: 5300 m 2  Heating demand: 475 MWh  Cooling demand: 155 MWh Ground system  20 boreholes  Rectangular configuration  Each 200 m deep Month Q h [MWh] Q c [MWh] Jan97.9- Feb89.3- Mar Apr May Jun-25.7 July-33.2 Aug-31.3 Sep-19.2 Oct Nov Dec77- Year475155

Building Services Engineering CHALMERS EFFSYS 2 meeting # Borehole wall temp (T w )Temperature penalty (T p ) 1Cylindrical SourceInfinite length line source 2Cylindrical SourceFinite length line source 3Infinite length line source 4Finite length line source 5Superposition borehole model (SBM) SIMULATING MULTIPLE BOREHOLES T b = brine temperature T w = borehole wall temperature T p = temperature penalty from neighbouring boreholes

Building Services Engineering CHALMERS MEAN BRINE TEMPERATURES EFFSYS 2 meeting

Building Services Engineering CHALMERS Load factor (l): the ratio of the net heating and cooling demands of the building to the sum of their absolute values. Geometry factor (g): the ratio of the volume V of the ground system to its heat exchange area A. CHARACTERISTIC KEY NUMBERS EFFSYS 2 meeting

Building Services Engineering CHALMERS CHARACTERISTIC KEY NUMBERS EFFSYS 2 meeting

Building Services Engineering CHALMERS Javed, S., Fahlén, P. and Holmberg, H., Modelling for optimization of brine temperature in ground source heat pump systems. Proceedings of 8th international conference on sustainable energy technologies; SET2009, Aachen, Germany. August 31- September 3. Javed, S., Fahlén, P. and Claesson, J., Vertical ground heat exchangers: A review of heat flow models. Proceedings of 11th international conference on thermal energy storage; Effstock 2009, Stockholm, Sweden. June Fahlén, P, Efficiency aspects of heat pump systems - Load matching and parasitic losses. IEA Heat pump centre Newsletter, vol. 26, nr. 3, , (IEA.). PUBLICATIONS EFFSYS 2 meeting

Building Services Engineering CHALMERS LITERATURE REVIEW EFFSYS 2 meeting Single boreholes: Long term response can be modelled using simple existing analytical models with reasonable accuracy. Multiple boreholes: Shortage of analytical models for both long and short term response. Need of an analytical model which: -is capable of simulating both short-term and long-term response of GHE. -considers all significant heat transfer processes in GHE. -retains the actual geometry of the borehole.

Building Services Engineering CHALMERS MODELLING EFFSYS 2 meeting Existing Analytical models: –Equivalent pipe / cylinder instead of a U-tube. –Thermal capacities of the water and the pipe are often ignored. –Response is a function only of the distance (r) from the centre of the equivalent pipe.

Building Services Engineering CHALMERS MODELLING EFFSYS 2 meeting New Analytical models: –Two pipes in the ground. –Accounts for the thermal short circuiting between the two legs of the U-tube. –Response is a function of both x and y. –Can predict the short time response accurately.

Building Services Engineering CHALMERS MODELLING EFFSYS 2 meeting New Analytical models: –Two pipes in the grout surrounded by the ground. –Accounts for the thermal properties of both the grout and the ground.

Building Services Engineering CHALMERS MODELLING EFFSYS 2 meeting New Numerical model: –Solved the heat transfer problem in 2D using conformal coordinate system. –Used for the validation of the analytical model.

Building Services Engineering CHALMERS LITERATURE REVIEW EFFSYS 2 meeting Single boreholes: Long term response can be modelled using simple existing analytical models with reasonable accuracy. Multiple boreholes: Shortage of analytical models for both long and short term response. Need of an analytical model which: -is capable of simulating both short-term and long-term response of GHE. -considers all significant heat transfer processes in GHE. -retains the actual geometry of the borehole.

Building Services Engineering CHALMERS Development of a test facility. Experiments to determine: –Thermal response for heat extraction and injection conditions. –Flow effects. –System effects. Validation of the developed models. EXPERIMENTS EFFSYS 2 meeting

Building Services Engineering CHALMERS LABORATORY DEVELOPMENT EFFSYS 2 meeting

Building Services Engineering CHALMERS LABORATORY DEVELOPMENT EFFSYS 2 meeting

Building Services Engineering CHALMERS BRINE & CHILLED WATER SYSTEM EFFSYS 2 meeting

Building Services Engineering CHALMERS HOT WATER SYSTEM EFFSYS 2 meeting

Building Services Engineering CHALMERS GROUND HEAT EXCHANGER SYSTEM EFFSYS 2 meeting

Building Services Engineering CHALMERS THERMAL RESPONSE TESTING EFFSYS 2 meeting

Building Services Engineering CHALMERS INITIAL RESULTS EFFSYS 2 meeting  Ground thermal conductivity: 3 W/m-K  Undisturbed ground temperature: 9 °C

Building Services Engineering CHALMERS CONCLUSIONS EFFSYS 2 meeting  Conducted a state-of-the-art literature review.  Presented different approaches to model multiple borehole systems.  Developing new analytical and numerical methods.  Carrying out experiments.

Building Services Engineering CHALMERS EFFSYS 2 meeting QUESTIONS / COMMENTS THANK YOU!