1. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
The 3rd edition of the International Conference on
Microgeneration and Related Technologies.
Naples April 2013
LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Nick Kelly University of Strathclyde, Glasgow
Adam Hawkes, Imperial College, London

2. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Overview
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

3. Why Load Shift Heat Pumps?
LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Why Load Shift Heat Pumps?

4. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Previous Work
Hong et al. looked at ‘flexibility’ of HPs in UK dwellings
ability to time shift HP
without affecting end user
time shifts of 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
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

5. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Model
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)

6. Heat Pump System Unbuffered
LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Heat Pump System Unbuffered

7. Heat Pump System Buffered
LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Heat Pump System Buffered

8. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Model - Storage
heating/DHW return
hot water for heating/DHW
HP return
HP flow
PCM modules
tank stratification
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

9. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Model PCM
commercial inorganic PCM
PCM Products,

10. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Method
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)

11. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Method
Heat Pump Operating Periods
Ref.
6-9hrs
Reference
16-23hrs
Economy 10
0-5hrs
13-16hrs
20-22hrs
Time 12 24

12. Technical Performance
LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Technical Performance

13. Technical Performance
LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Technical Performance

14. Technical Performance
LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Technical Performance

15. Technical Performance
LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Technical Performance

16. Technical Performance
LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Technical Performance

17. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Overall Performance

18. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Overall Performance

19. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Overall Performance

20. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Conclusions
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

21. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Caveats!
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

22. LOAD MANAGEMENT OF HEAT PUMPS USING PHASE CHANGE HEAT STORAGE
Thank You!
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.