System design and feasibility of trigeneration systems with hybrid photovoltaic-thermal (PVT) collectors for zero energy office buildings in different climates

Significance 

Imminent climatic ramifications can be averted by adoption of renewable energy resources so as to limit global temperature rise by 1.5°C. Amongst the proposed approaches and energy efficient systems, the zero or plus energy office buildings have shown promising results. Nonetheless, research has shown that such plus energy office buildings ought to attain very high building standards in addition to calling for highly efficient energy supply systems due to space limitations for renewable installations. Conventional solar cooling systems use photovoltaic electricity or thermal energy to run either a compression-cooling machine or an absorption-cooling machine in order to produce cooling energy during daytime, while they use electricity from the grid for the nightly cooling energy demand. With a hybrid photovoltaic-thermal collector, electricity as well as thermal energy can be produced at the same time. These collectors can produce also cooling energy at nighttime by longwave radiation exchange with the night sky and convection losses to the ambient air. Such a renewable trigeneration system offers new fields of applications. Unfortunately, the technical, ecological and economical aspects of such systems are still largely unexplored.

To address this, German researchers from the University of Applied Sciences Stuttgart: Maximilian Haag, Jonas Stave, Nermeen Abdelnour and led by Professor Ursula Eicker (currently Canada Excellence Research Chair in Next Generation Cities at Concordia University) in collaboration with Reiner Braun at the Reutlingen University investigated the potential of a PVT system to heat and cool office buildings in three different climate zones. Their objective was to assess the use of hybrid collectors (PVT) for trigeneration of electricity, heat and cold. Their work is currently published in the research journal Solar Energy.

For this purpose, the research team undertook a parametric simulation study so as to evaluate the system design with different PVT surface areas and storage tank volumes to optimize the system for three different climate zones and for two different building standards. The team investigated the PVT collectors act as a heat source and heat sink for a reversible heat pump.

The authors reported that due to the reduced electricity consumption (from the grid) for heat rejection, the overall efficiency and economics improved compared to a conventional solar cooling system using a reversible air-to-water heat pump as heat and cold source. In addition, the annual costs for such a system were seen to be comparable to conventional solar thermal and solar electrical cooling systems.

In summary, the study demonstrated the applicability of PVT collectors as a heat source and heat sink for a reversible heat pump (rev. HP) in three different climates. In order to analyze the potential of PVT systems to achieve net zero energy, passive building standards were compared to more conventional construction standards. Overall, their work showed that through their new approach, a specific system dimensioning could be found at each of the investigated locations worldwide for a valuable economic and ecological operation of an office building with PVT technologies in different system designs.

System design and feasibility of trigeneration systems with hybrid photovoltaic-thermal (PVT) collectors for zero energy office buildings in different climates - Advances in Engineering
Fig. 1 Floor plan and north-south view of the building model based on the IEA Task 38 (left) and 3D model (right)
System design and feasibility of trigeneration systems with hybrid photovoltaic-thermal (PVT) collectors for zero energy office buildings in different climates - Advances in Engineering
Fig. 2 Hydraulic scheme of the PVT system, operation mode cooling in summer at night-times (top) and heating in winter during day-times (bottom)
System design and feasibility of trigeneration systems with hybrid photovoltaic-thermal (PVT) collectors for zero energy office buildings in different climates - Advances in Engineering
Fig. 3 TRNSYS simulation model of the system
System design and feasibility of trigeneration systems with hybrid photovoltaic-thermal (PVT) collectors for zero energy office buildings in different climates - Advances in Engineering
Fig. 4 System behaviour for 5 hot summer days in Stuttgart passive building, storage tank V=1m³ and three representative PVT collector areas
System design and feasibility of trigeneration systems with hybrid photovoltaic-thermal (PVT) collectors for zero energy office buildings in different climates - Advances in Engineering
Fig. 5 System behaviour for 5 hot summer days in Moscow passive building, storage tank V=1m³ and three representative PVT collector areas
System design and feasibility of trigeneration systems with hybrid photovoltaic-thermal (PVT) collectors for zero energy office buildings in different climates - Advances in Engineering
Fig. 6 System behaviour for 5 hot summer days in Dubai passive building, storage tank V=1m³ and three representative PVT collector areas

System design and feasibility of trigeneration systems with hybrid photovoltaic-thermal (PVT) collectors for zero energy office buildings in different climates - Advances in Engineering

About the author

Reiner Braun is a senior scientist at the Herman Hollerith Zentrum (HHZ) at Reutlingen University, Germany. He finished his bachelor studies for building physics at the HFT Stuttgart focusing on theoretical building physics and acoustics. In addition, he holds a M.Sc. in building restoration from the Karlsruhe Institute of Technology (KIT, Germany). Before joining Reutlingen University, he worked for the University of Applied Sciences Stuttgart (HFT) as managing director of the Centre for Sustainable Energy Technology (zafh.net).

Mr. Braun is the head of the Smart City Living Lab at the HHZ where his research activities are concentrated on the development of energy and mobility concept for regions and cities, IoT networks, data analytics and the development urban data models to characterize the food, energy and water nexus on an urban district level.

About the author

Prof. Ursula Eicker is the new Canada Excellence Research Chair (CERC) for Next Generation Cities at Concordia University Montréal. A German physicist, Eicker has held leadership positions at the Stuttgart University of Applied Sciences and its Centre for Sustainable Energy Technologies. She coordinated many international research projects in the fields of energy efficiency in buildings and sustainable energy supply systems for more than two decades.

Since June 2019, she leads an ambitious research program to establish transformation strategies toward zero-carbon cities. The 7 year research program receives 10 million CAD government funding and is supported by a further 10 million Dollars by Concordia University, who invests in the city cluster research with five professor positions in buildings and electrical engineering, biodiversity, philosophy and design. The Concordia Next Generation Cities Cluster addresses the challenges of the urban transformation with a transdisciplinary approach and develops tools and strategies for a sustainable future.

Prof. Eicker has published 7 Books, 23 book contributions, 77 Peer Reviewed Papers and 317 Conference Papers.

Reference

Reiner Braun, Maximilian Haag, Jonas Stave, Nermeen Abdelnour, Ursula Eicker. System design and feasibility of trigeneration systems with hybrid photovoltaic-thermal (PVT) collectors for zero energy office buildings in different climates. Solar Energy, volume 196 (2020) page 39–48.

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