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Solar energy and ground source heat pumps for Swedish multi-family housing (completed)

Ground source heat pumps (GSHP) have a relatively small market share in multi-family houses in part due to the limited land space available for drilling. The rapidly growing market for solar photovoltaics (PV) provides an opportunity for GSHP by acting as a secondary heat source and regenerating the ground via a heat exchanger fixed to the rear of the panel. The hybrid PV/thermal collectors, called PVT, have higher efficiencies than PV only, but also come with a significant additional cost.

Solar energy and ground source heat pumps for Swedish multi-family housing

Funded by: The Swedish Energy Agency (Energimyndigheten) under the Effsys Expand program (project number 40936-1)

Time period: January 2016 – June 2018

Project partners:

  • KTH Energy Technology
  • Danfoss / Thermia Heat Pumps
  • Bengt Dahlgren Stockholm Geo
  • Solhybrid i Småland
  • Skånska Energilösningar
  • Avanti
  • Nowab Consulting
  • BRF Moranviken

Background

To increase the efficiency of solar collectors, self-consumption of PV generation, and heat pump efficiency, the integration of hybrid solar PV/thermal modules on the source-side of the heat pump can be interesting. A PV/thermal hybrid collector affixes a heat exchanger to the back of PV cells, which can increase electricity production by cooling the cells as well as capture thermal energy normally lost to the ambient air. Connecting to the source side of the heat pump will reduce the electricity needed for the compressor and enable storage of excess heat in the boreholes. The stored heat increases the borehole temperatures such that the compressor runs more efficiently in winter as well. The configuration also opens up interesting possibilities for converting PV over-production into stored heat rather than dumping it into the network.

Aim and Objectives

This study explores the technical and economic potential of PV/thermal + GSHP systems in Swedish multi-family houses. While not a new concept, much of the previous work has been focused solar thermal systems and the addition of PV can make for unique configurations and control strategies. The primary objective of this research is to identify the technical and economic potential of PVT integration into multi-family house GSHP systems with borehole energy storage. This is achieved through a comprehensive technology review, dynamic complete systems modeling, construction of a detailed test site, and a qualitative assessment of commercial opportunities.

Outcomes

The results show that PVT collectors can adequately support a significant undersizing of boreholes, but that it is economical only in specific conditions. One is where the heat pump shuts down due to the excessive low source temperatures and runs on the backup auxiliary heater. The savings from drilling and the increase in seasonal performance factor (SPF) is enough to justify the additional cost of the PVT. In cases where a heat pump has been running for several years and the ground temperatures are low, PVT can lift and stabilize temperatures at a lower cost than additional drilling (assuming it is possible to do additional drilling). In cases where land area is not a limitation, the highest efficiency and lowest cost option is to drill a traditionally sized borehole field and install a PV-only system.

Read the full final report .

Academic Publications

Sommerfeldt N, Madani H. In-depth techno-economic analysis of PV/Thermal plus ground source heat pump systems for multi-family houses in a heating dominated climate. Solar Energy 2019; vol. 190, pp. 44-62. doi:10.1016/J.SOLENER.2019.07.080.

Poppi S, Sommerfeldt N, Bales C, Madani H, Lundqvist P. Techno-economic review of solar heat pump systems for residential heating applications. Renewable & Sustainable Energy Reviews 2018, vol. 81, pp. 22-32. doi:10.1016/j.rser.2017.07.041.

Sommerfeldt N, Madani H. A Techno-Economic Comparison between PV and PVT Integrated Ground Source at Pumps for Multi-Family Houses. 12th ISES Eurosun Conference, Rapperswil, Switzerland, 2018. doi: 10.18086/eurosun2018.02.19.

Sommerfeldt N, Ollas P. Reverse engineering prototype solar PV/thermal collector properties from empirical data for use in TRNSYS Type 560. ISES Solar World Congress and IEA Solar Heating and Cooling Conference 2017, Abu Dhabi: 2017, pp. 1121-32. doi:10.18086/swc.2017.18.11.

Sommerfeldt N, Madani H. Review of Solar PV/Thermal Plus Ground Source Heat Pump Systems for European Multi-Family Houses. 11th ISES Eurosun Conference, Palma de Mallorca, Spain: 2016, pp. 1382-93. doi:10.18086/eurosun.2016.08.15.

Pressiani M, Sommerfeldt N, Madani H. Investigation of PV/thermal collector models for use with ground source heat pumps in transient simulations. 11th ISES Eurosun Conference, Palma de Mallorca, Spain: 2016, pp. 1360-71. doi:10.18086/eurosun.2016.08.19.

Andersson, M. (2018) Comparison of solar thermal and photovoltaic assisted heat pumps for multi-family houses in Sweden. KTH Royal Institute of Technology, MSc Thesis.

Razzetti, E. (2018) Potential for Seasonal Electricity Storage in Borehole Thermal Energy Stores with Heat Pumps. KTH Royal Institute of Technology, MSc Thesis.

Schön, G. (2017) Numerical modelling of a novel PVT collector at cell resolution. KTH Royal Institute of Technology, MSc Thesis.

Pressiani, M. (2016) Photovoltaic and thermal hybrid solar collector: TRNSYS analysis and possible improvements. Politecnico Milano, MSc Thesis.

Project contact persons

For more information about the project or partnership opportunities, please contact:

PARMENIDES – Plug & plAy EneRgy ManagEmeNt for hybriD Energy Storage
HYSTORE - Hybrid services from advanced thermal energy storage systems
Open-source models for holistic building energy system design at scale
Tank to Grave Management of new Low-GWP Refrigerants (Hantering av nya låg-GWP köldmedier från installation till destruktion)
Novel tool and guidelines for designing ground source heat pumps (GSHPs) in densely populated areas
Data driven lab for building energy systems
Long-term performance measurement of GSHP systems serving commercial, institutional and multi-family buildings
RE-Park
Smart Control Strategies for Heat Pump Systems
Open-source models for holistic building energy system design at scale
Control systems for hybrid solutions based on biomass fueled Stirling engines, solar and wind for rural electrification
Prosumer-Centric Communication for Solar PV Diffusion (completed)
Towards Sustainable (Fossil-free) Heating System in Small Residential Buildings
Solar energy and ground source heat pumps for Swedish multi-family housing (completed)
Solar photovoltaic systems in Swedish cooperative housing (completed)
Smart Control Strategies for Heat Pump Systems (completed)
Creating and Understanding Smart Innovation in Cities
Building heating solutions in China
Accelerating innovation in buildings
High-Resolution GIS District Heating Source-Load Mapping
Digitalization and IoT technologies for Heat Pump systems
Sustainable combined systems for heating of buildings (completed)
Cost- and Energy-Efficient Control Systems for Buildings
Situation of Opportunity in the Growth and Change of three Stockholm City Districts (completed)
Wuxi Sino-Swedish Eco-City Project (completed)
Smart Renovation Strategies for Sustainable Electrification
Future Secondary Fluids for indirect refrigeration systems
Smart Fault Detection and Diagnosis for Heat Pumps
Performance indicators for energy efficient supermarket buildings
Magnetic Refrigeration
High-Resolution GIS District Heating Source-Load Mapping
Smart Solar Hybrid Solutions for Sustainable European Buildings (completed)
Building state-of-the-art (SotA) supermarket: Putting theory into practice
Efficient utilization of industrial waste heat by low temperature heat driven power cycles – an integrated approach for Swedish Industry
Cooperation between Supermarkets and Real Estate Owners; Energy Efficiency and Business Models
Digitalization and IoT technologies for Heat Pump systems
Capacity control in Heat Pump systems
Alternative secondary fluids
Functional surface coatings for energy efficient heat pumps
Two-phase flow in flat channels
Two phase heat transfer & pressure drop with new environment friendly refrigerants in minichannels (completed)
Numerical Study on flow boiling in micro/mini channels (completed)
Distributed Cold Storages in District Cooling
Integrating Latent Heat Storage into Residential Heating Systems
Simulation of temperature distribution in borehole thermal storages supported by fiber optic temperature measurements (completed)
Solar energy and ground source heat pumps for Swedish multi-family housing (completed)
Neutrons for Heat Storage, NHS, (completed)
4D Monitoring of BTES (completed)
Aquifer Thermal Energy Storage (completed)
Deep Borehole Heat Exchanger (completed)
Combined Heat and Power plants in combination with borehole thermal energy storage (completed)
Improved borehole technology for Geothermal Heat Pumps development (completed)
Compact Minichannel Latent Energy Storage for Air Related Cold Storage Applications
Building heating solutions in China
Toward Sustainable (Fossil-free) Heating System in Small Residential Buildings
Renewable Energy Park, RE-Park (completed)
Efficient use of energy wells for heat pumps (completed)
Efficient design of geothermal heating systems (completed)
SPF (completed)