Research progress on heat pumps and mchp at Northumbria

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1 31 st HEXAG Meeting Research progress on heat pumps and mchp at Northumbria 20 th May 2014 Chris Underwood (Professor of Energy Modelling for the Built Environment, Faculty of Engineering & Environment, University of Northumbria at Newcastle)

2 Ground source heat pump design 1. Domestic ground source heat pump performance gap, focusing in particular on Array capacity Heat pump sizing Typical encapsulated medium tank

3 Context

4 Heat pump with vertical ground loop simulation tool

5 Badly sized arrays

6 First and fifth year minimum daily array inlet temperatures

7 Fifth year array fluid inlet temperature comparisons

8 Ground source heat pump control and integration 2. Detailed domestic-scale heat pump modelling to investigate variable speed drives, improved controls and thermal storage Macarthur & Grald s distributed parameter dynamic thermal model New variable speed compressor model New expansion device model and electronic control More robust refrigerant property routine Typical encapsulated medium tank

9 Well established 1 st and 2 nd generation technologies Brazed plate condenser (typical pinch 2-3K) Mechanical thermostatic expansion valve Working fluids azeotrope R134a or zeotropic blends R407C, R410A OR Scroll compressor Water source - brazed plate evaporator (typical pinch 2-3K) Air source fin-and-coil Evaporator (typical pinch 3-5K)

10 Detailed modelling to investigation VSDs, improved control and thermal storage Compressor identification Heat exchanger modelling [pars] m, W W W Goal elec min m, W subject to: pars pars elec lowerbound pars pars upperbound t t A r rc m r 0 (refrigerant, continuity) z 0 (refrigerant, energy z h A m h U L T T r r rc r r r rp r w L V dl 1 dl M r rg rl 0 0 L 0 dl L (mass flux; no-slip condition) T w w Awccw Uf Lfp Tw Tf UrLrp Tr Tw 0 (HX wall) t Tf T f f Afc cf mf cf Uf Lfp Tf Tw 0 (source/sink liquid) t z

11 THERMAC Outlet Sink Water Temperature Outlet Sink Water Temperature Outlet Sink Water Temperature 60 Celsius Measured Simulated Time Sample Celsius Measured Simulated Time Sample Celsius Measured Simulated Time Sample 10 5 Coefficient of Performance Measured Simulated Time Sample Coefficient of Performance Measured Simulated Time Sample Coefficient of Performance Measured Simulated Time Sample Thermostat setting 38 o C Thermostat setting 42 o C Thermostat setting 50 o C

12 Advanced ground sourcing methods 3. Development of a new laboratory to investigate advanced methods of ground sourcing Open loop standing column wells (with or without bleed) Conventional and deep slinky trenches Gas-fired absorption cycle heat pump Typical encapsulated medium tank

13 Standing column well concept

14 SCWs results of modelling

15 6m-deep slinky horizontal loop 1m-deep slinky control loop 150m-deep SCW head 120m-deep SCW head Northumbria s advanced ground source heat pumps test facility

16 6m-deep slinky horizontal loop 1m-deep slinky Advanced GSHP sourcing control loop laboratory (under construction) 150m-deep SCW head 120m-deep SCW head Northumbria s advanced ground source heat pumps test facility

17 Improved method for ground thermal property testing 4. Ground thermal property testing Traditionally, line source theory is used to find the gradient of the late log-time response to a step heat input of a test heat exchanger The method leads to a mean ground thermal conductivity and borehole thermal resistance but other key parameters have to be estimated Here, multiple-objective function optimisation is used to find the above plus the grout thermal capacity and surrounding rock thermal capacity important parameters for use in ground source simulation The method can also be used with disturbed/faulty test data Typical encapsulated medium tank

18 Flat-plate and evacuated-tube solar collectors at Northumbria s Low Carbon Systems laboratory Mobile geothermal response test rig

19 Ground thermal properties NCL (RMSE 0.249) GHD-1 (RMSE 0.227) o C 18 o C Time (h) Time (h) o C GHD-2 (RMSE 0.314) Time (h) o C HLS-1 (RMSE 0.310) Time (h) o C HLS-2 (RMSE 0.410) Model + Measured min f ( x) k, Rbhx, C, C g Time (h)

20 Domestic thermal storage 5. Development of hybrid thermal storage systems using phase change materials Coil-encapsulated salt hydrates Shape-stabilised paraffin wax balls PCM wrapped heat pipe - THERMAC Typical encapsulated medium tank

21 Northumbria s Low Carbon Systems laboratory

22 Typical encapsulated medium tank Coil-encapsulated PCM (6.8% salt hydrate in a 300L (nom) water tank coil)

23 Typical encapsulated medium tank Heat transfer to local space heating

24 Simulation with a larger PCM inventory Simulated charge/discharge: 300L water tank & 150L/150L hybrid water/pcm tank Heat transfer kw Hybrid tank Water tank Time (hours)

25 Domestic thermal storage and heat-led mchp 6. Modelling and integration of micro-combined heat and power mchp Using thermal storage to reduce domestic scale (heat-led) mchp module starts Load matching and economics of larger (power-led) mchp including trigeneration Typical encapsulated medium tank

26 Simulation of Stirling cycle based mchp modules Empirical model based on WhisperTech s Whispergen module Northumbria s Simulink HVAC Blockset

27 Simulated module starts vs thermal storage (January) 1000 Simulated module starts in a typical January for Stirling cycle mchp 800 Starts per month Storage in litres

28 Simulated module efficiency vs thermal storage (January) 70 Efficiency of Stirling cycle mchp as a function of thermal storage capacity Percent Storage in litres

29 Larger (power-led) non-domestic CHP including trigeneration Efficiencies: heat heat = p p 2 = p p Part load ratio: p Northumbria s bespoke software CHPSim has been used to help develop energy strategies for many building estates including Newcastle Airport and Darlington Memorial Hospital

30 Hospital in Northern Ireland: Power 2005/ kw Bottling plant in Morpeth: Power 2005/ MW Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec One week One week One week 3 International Airport: Power (2004/05) 2,800 2 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7... kw 2,400 2,000 1,600 1, J F M A M J J A S O N D 2,400 2,000 1,600 1,200