MODELING SOLAR ASSISTED HEAT PUMPS WITH

Transcription

1 MODELING SOLAR ASSISTED HEAT PUMPS WITH BOREHOLE RECHARGING IN MULTI-FAMILY HOUSES Nelson Sommerfeldt KTH Royal Institute of Technology, Stockholm, Sweden Svenska Kyl & Värmepumpdagen 2017

2 What is a solar assisted heat pump? 1. Start with a heat pump system 2

3 What is a solar assisted heat pump? 1. Start with a heat pump system 2. Add some solar panels 3

4 What is a solar assisted heat pump? 1. Start with a heat pump system 2. Add some solar panels 3. Connect the two 4

5 Our System Configuration Serial configuration Unglazed, uninsulated PVT collectors Design motivations Simplicity Flexibility Cost Storage 5 Sommerfeldt, N., Madani, H. Review of Solar PV/Thermal Plus Ground Source Heat Pump Systems for European Multi-Family Houses. 11 th ISES Eurosun Conference, Palma de Mallorca, Spain, October 2016

6 Research Challenges Collector design Borehole design Building application System control Key performance indicators 6

7 Why go for a solar HP? Increased renewable fraction of buildings* Increased heat pump efficiency* Increased solar collector efficiency* Reduced borehole length* Diurnal energy storage* Seasonal energy storage* Reduction in energy costs* *It depends on perspective and objectives 7

8 Boundary Levels for SHP Boundary Level 1: Individual Components Boundary Level 2: Solar and HP Systems Boundary Level 3: Building Energy System Boundary Level 4: Urban Energy System Solar Collector / Module Heat Pump Storage Tank Balance of system Solar and HP Integration HVAC System Electricity Loads Districts and Cities Power Grids 8

9 GSHP Design goal use less electricity SPF 4 definition remains the same 9 SSSSSS 4 = QQ SSSS + QQ DDDDDD EE HHHH + EE AAAAAA dddd dddd

10 GSHP + Solar Thermal Design goal use less electricity SPF 4 definition remains the same 10 SSSSSS 4 = QQ SSSS + QQ DDDDDD EE HHHH + EE AAAAAA dddd dddd

11 GSHP + Solar PV Solar electricity replaces grid SPF 4 is missing information SPF 5 considers PV generation free 11 SSSSSS 4 = QQ SSSS + QQ DDDDDD EE HHHH + EE AAAAAA dddd dddd SSSSSS 5 = QQ SSSS + QQ DDDDDD dddd EE HHHH + EE AAAAAA EE PPPP HHHH dddd

12 An example in conflicting definitions PV Generation MWh/yr HP Load MWh/yr Apt Load MWh/yr 12

13 An example in conflicting definitions PV Self-Consumption Apt Priority HP Priority 0% 25% 50% 75% 100% PV to HP PV to Apt PV to Grid 3,6 3,5 3,4 3,3 3,2 3,1 3 SPF 5 Variants No PV HP Priority Apt Priority 13

14 An example in conflicting motives Normal Operation PV Driven Operation 14 Fischer, D. et al. Smart meter enabled control for variable speed heat pumps to increase PV self-consumption. 24 th IIR International Congress of Refrigeration, DOI: /RG

15 Limitations of SPF 5 Electricity flows across boundaries System boundaries are for accounting Common definition is needed, but Conflict with other control strategies 15 SSSSSS 4 = QQ SSSS + QQ DDDDDD EE HHHH + EE AAAAAA dddd dddd SSSSSS 5 = QQ SSSS + QQ DDDDDD dddd EE HHHH + EE AAAAAA EE??? dddd

16 Optimization Approach and KPI Design goal minimize TLCC Supporting KPI SPF 4 Self-consumption Solar/RE fraction PVT eff. & cost BH eff. & cost 16

17 Systems modeling in TRNSYS Complete system model Three-minute time steps 20 year simulations 17

18 Preliminary Results Example Year One Performance 3,0 3,2 3,4 3,6 3,8 4,0 BL1: SPF1 BL2: SPF4 BL3: SPF5 Year Ten Performance 3,0 3,2 3,4 3,6 3,8 4,0 BL1: SPF1 BL2: SPF4 BL3: SPF5 GSHP GSHP with PV GSHP with PVT GSHP GSHP with PV GSHP with PVT 18

19 Preliminary Results Example Core Temp ( ) Year of Operation Boreholes with PVT Boreholes without PVT 19

20 Immediate Research Activities Model Construction Incorporate state-of-the-art climate and borehole models Design control strategies for minimizing TLCC Generate multiple building and market scenarios Research Questions What is the potential for seasonal solar storage? What is the potential for borehole length reduction? What is the potential for borehole area reduction? What is the marginal benefit of PVT over PV? 20

21 Conclusions Defining system performance in SAHP is non-trivial Objectives and KPI change with system boundary level PV+HP has different design challenges from ST+HP TRNSYS is the state of the art software for SAHP analysis 21

22 Thank you for your attention! Nelson Sommerfeldt Hatef Madani BRF Moranviken