OPTIMIZATION OF GROUND COUPLED HEAT PUMP SYSTEMS

1. Akademiska Hus Carrier CTC / Enertech Donghua University Fastighetsägarna Geotec Grundfos IVT LTH NCC Nibe SWECO TAC ThermiaVärme Wilo ÅF-Infrastruktur OPTIMIZATION OF GROUND COUPLED HEAT PUMP SYSTEMS Saqib Javed (PhD Researcher) Per Fahlén (Research Leader) Johan Claesson (Supervisor) EFFSYS 2 meeting 2009-12-14

2. objective • 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. EFFSYS 2 meeting 2009-12-14

3. Literature review • 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. EFFSYS 2 meeting 2009-12-14

4. Case study • Astronomy-House, Lund University • Floor area: 5300 m2 • Heating demand: 475 MWh • Cooling demand: 155 MWh • Ground system • 20 boreholes • Rectangular configuration • Each 200 m deep EFFSYS 2 meeting 2009-12-14

5. Simulating MULTIPLE BOREHOLES Tb = brine temperature Tw = borehole wall temperature Tp = temperature penalty from neighbouring boreholes EFFSYS 2 meeting 2009-12-14

6. MEAN BRINE TEMPERATURES EFFSYS 2 meeting 2009-12-14

7. publications • Javed, S., Fahlén, P. and Holmberg, H., 2009. 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., 2009. Vertical ground heat exchangers: A review of heat flow models. Proceedings of 11th international conference on thermal energy storage; Effstock 2009, Stockholm, Sweden. June 14-17. • Fahlén, P, 2008. Efficiency aspects of heat pump systems - Load matching and parasitic losses. IEA Heat pump centre Newsletter, vol. 26, nr. 3, 2008-08, (IEA.). EFFSYS 2 meeting 2009-12-14

8. Literature review • 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. EFFSYS 2 meeting 2009-12-14

9. modelling • 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. EFFSYS 2 meeting 2009-12-14

10. modelling • 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. EFFSYS 2 meeting 2009-12-14

11. modelling • New Analytical models: • Two pipes in the grout surrounded by the ground. • Accounts for the thermal properties of both the grout and the ground. EFFSYS 2 meeting 2009-12-14

12. modelling • New Numerical model: • Solved the heat transfer problem in 2D using conformal coordinate system. • Used for the validation of the analytical model. EFFSYS 2 meeting 2009-12-14

13. Literature review • 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. EFFSYS 2 meeting 2009-12-14

14. experiments • 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. EFFSYS 2 meeting 2009-12-14

15. Laboratory development EFFSYS 2 meeting 2009-12-14

16. Laboratory development EFFSYS 2 meeting 2009-12-14

17. Brine & chilled water system EFFSYS 2 meeting 2009-12-14

18. Hot water system EFFSYS 2 meeting 2009-12-14

19. Ground heat exchanger system EFFSYS 2 meeting 2009-12-14

20. Thermal response testing EFFSYS 2 meeting 2009-12-14

21. Initial results • Ground thermal conductivity: 3 W/m-K • Undisturbed ground temperature: 9 °C EFFSYS 2 meeting 2009-12-14

22. conclusions • 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. EFFSYS 2 meeting 2009-12-14

23. Questions / commentsThank you! EFFSYS 2 meeting 2009-12-14