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The 3 rd edition of the International Conference on Microgeneration and Related Technologies. Naples 15-17 April 2013. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE. Nick Kelly University of Strathclyde, Glasgow Adam Hawkes, Imperial College, London. Overview.
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The 3rd edition of the International Conference on Microgeneration and Related Technologies. Naples 15-17 April 2013 LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE Nick Kelly University of Strathclyde, Glasgow Adam Hawkes, Imperial College, London
Overview LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE • in UK heat pumps (HP) promoted as low-carbon heating source and potential replacement for gas boilers • problem for low voltage network at times of peak demand • load shifting a possible solution • HP load shifting requires use of buffering • presentation covers performance assessment of buffered domestic HP subject to load shifting • buffering with and without PCM • performance compared to unconstrained, unbuffered operation
Why Load Shift Heat Pumps? LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Previous Work LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE • Hong et al. looked at ‘flexibility’ of HPs in UK dwellings • ability to time shift HP • without affecting end user • time shifts of 0-1.5 hours with no buffering • 6 hours possible but only with 500 L buffer and passive house insulation levels • Arteconi at al. found even larger volumes required for conventional UK housing – 800 L per hour of ‘autonomy’ • Key questions: • could the use of PCM improve the situation? • how does load management and buffering affect performance? Hong J, Kelly N J, Thomson M, Richardson I (2013) Assessing heat pumps as flexible load, Proceedings of the IMECHE Part A: Journal of Power and Energy, 227 (1), pp 30-42. Arteconi A., Hewitt N.J., Polonara F. (2013) Domestic demand-side management (DSM): Role of heat pumps and thermal energy storage (TES) systems, Applied Thermal Engineering, 51, pp 155-165
Model LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE • Basis of work ESP-r model of a UK detached dwelling • 136m2 of floor area • thermal upgrading (floor, loft, cavity wall insulation) • family of 4 • equipped with buffered and unbuffered ASHP heating system • replaces gas boiler heating system (retrofit)
Heat Pump System Unbuffered LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Heat Pump System Buffered LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Model - Storage LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE hot water for heating/DHW tank stratification PCM modules HP return heating/DHW return HP flow Padovan R and Manzan M, Development of a stratified tank storage component for ESP-r with embedded phase change material modules, Proc. of the IMECHE Part A: J of Power and Eng. 2013; v227;1: pp 53-61.
Model PCM LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE • commercial inorganic PCM PCM Products, 2012. http://www.pcmproducts.net/Phase_Change_Material_Products.htm
Method LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE • to assess load shifting • operating time of heat pump fixed to off-peak UK Economy 10 periods • size of tank and % of PCM (by volume) varied • performance simulated over different seasonal weeks and for “extremes” of UK climate • delivered space temperatures and DHW temperatures compared to no load shift case (% occupied time below 18oC and 40oC, respectively) • tank size and PCM % identified for near identical end user service provision (same service provision as no load shift case)
Method LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE Heat Pump Operating Periods Ref. 6-9hrs Reference 16-23hrs Economy 10 0-5hrs 13-16hrs 20-22hrs Time 0 12 24
Technical Performance LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Technical Performance LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Technical Performance LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Technical Performance LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Technical Performance LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Overall Performance LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Overall Performance LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Overall Performance LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Conclusions LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE • the heating demand of a typical UK detached dwelling could be completely shifted to off peak periods • significant amounts of buffering required (1200 L) • the use of PCM more than halved the volume of thermal buffering required for effective load shifting • but … • energy use was significantly higher than in the reference case (no buffering, no load shifting) • emissions are higher than with no load shifting • running costs are higher than in the no load shifting case
Caveats! LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE • one case and one HP configuration • NOT an optimised system • scope for improvement in buffered system energy performance • emissions results based on 2011 CO2 intensity data • financial results based on existing Economy 10 tariff
Thank You! LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE The simulation work described in this presentation was done with the support of the SUPERGEN Highly Distributed Energy Futures research consortium (HIDEF). The authors gratefully acknowledge the funding and support provided by the UK Research Council’s Energy Programme under grant EP/G031681/1. The authors also wish to acknowledge the assistance of members of IEA ECBCS Annex 54 for their help and useful input to this work.