Publication type: Conference other
Type of review: Peer review (abstract)
Title: Merging photovoltaic panels and solar thermal collectors : how photovoltaic thermal (PVT) hybrid collectors boost environmental performance
Authors: Itten, René
Sabina, Manatschal
Stucki, Matthias
Brottier, Laetitia
et. al: No
Conference details: 37th European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC), Online, 7-11 September 2020
Issue Date: 10-Sep-2020
Language: English
Subjects: Life Cycle Assessment; Photovotlaic; Hybrid; Solar thermal; Greenhouse gas emissions
Subject (DDC): 333.79: Energy
621.3: Electrical, communications, control engineering
Abstract: 1. Aim and approach used Increased solar energy supply is crucial for the decarbonisation of the European energy system in order to limit climate change. A technology to produce solar electricity as well as heat are photovoltaic thermal hybrid solar collectors (PVT). PVT modules are a promising technology since they not only allow for the generation of heat in addition to electricity but they also increase the solar conversion efficiency due to the cooling effect of the heat exchanger on the photovoltaic panel. The aim of our analysis was to quantify the environmental impact of a PVT system in comparison to other systems for the provision of electricity and hot water. Therefore, we collected information on the production of PVT modules from the producer DualSun and established corresponding Life Cycle Inventory models for the full life cycle of PVT modules. As comparison systems for electricity and heat production we used (1) photovoltaics in combination with a solar thermal system, (2) European electricity mix at grid in combination with a natural gas-fired boiler and (3) European electricity mix at in combination with an air-water heat pump. The functional unit is defined as the energy yield of 1 kWh of electricity and 0.97 kWh of hot water over a life time of 30 years. The PVT module is modelled as combination of photovoltaic module and a heat exchanger as well as mounting system, electrical components including inverters and thermal components including hot water storage, pipes and circulation pumps. The Life Cycle Impact Assessment includes greenhouse gas emissions, primary energy, ReCiPe 2016 Endpoint (H) as well as the recommended midpoints for PEF. 2. Scientific innovation and relevance Our research focuses on the application of Life Cycle Assessment methodology to novel photovoltaic thermal hybrid solar collector produced by DualSun. The main advantage of PVT modules is the potential to produce heat as an additional by product while simultaneously increasing the electricity yield. This co-production of electricity and heat poses challenges for Life Cycle Assessment methodology since it would either require allocation or system expansion. For this study, we avoided allocation with the use system expansion in the context of electricity and heat supply in buildings, using comparable systems for electricity and heat supply in residential buildings as reference. The major scientific innovations are: 1) the Life Cycle Assessment of novel photovoltaic thermal hybrid solar collector (PVT) and 2) the comparison of PVT modules to different systems providing electricity as well as heat in buildings without an allocation of the impacts to either electricity or heat generation. 3. Results and conclusions In Figure 1 the life cycle greenhouse gas emissions from a PVT installation are visualized. The production of 1 kWh of electricity as well as 0.97 kWh of heat using a PVT system causes greenhouse gas emissions of 65 g CO2-eq according to the IPCC 2013 GWP 100a. The components electricity (yellow) include the inverter, the cabling and all electrical equipment up to the grid connection. The components for providing hot water (blue) include all pipes, circulation pumps, valves and a hot water tank. 61% of all greenhouse gases origin from the production of the PV panel. The contribution of the mounting structure and the electrical as well as thermal balance-of-system (BOS) components to the total greenhouse gas emissions is very similar with about 12% each (see Figure 1). The PVT modules have lower environmental impacts than the combination of separate PV and solar thermal collectors. When compared to the conventional electricity and heat supply with electricity from grid as well as natural gas boiler, the use of PVT modules would cause considerable savings of greenhouse gas emissions. The contribution of the heat exchanger as well as the components for the use of heat (thermal storage, pipes, etc) have a contribution below 20 % for all midpoints analysed (see Figure 2 and Figure 3) except for human health cancer (54 %), eco-toxicity (28 %) and land use (21 %). This means that PVT modules can produce renewable heat in addition to electricity with a rather small investment in additional impacts for most midpoints. If we compare this investment to the potential savings possible due to the use of renewable heat from PVT modules instead natural gas (or oil) boilers as common heating systems in central Europe, this reveals significant potentials for carbon savings as well as savings for other environmental impacts. The electric and thermal yield of PVT modules depend on the temperature at which the hot water is discharged from the heat exchanger: with lower temperature, electric and thermal yield are increased and therefore environmental impacts per kWh harvested energy are decreased. In this study, we used a rather low thermal yield of 186 kWh of heat per square meter of PVT module, since hot water is generally used at higher temperatures. However, if the desired temperature level of the usable heat is lower, the thermal yield of PVT modules would increase significantly up to two times as much usable heat. In conclusion, the comparison of PVT modules with other systems to provide electricity and heat revealed significant potentials for reduced environmental impacts even for the conservative case of low thermal yields.
Fulltext version: Published version
License (according to publishing contract): Licence according to publishing contract
Departement: Life Sciences and Facility Management
Organisational Unit: Institute of Natural Resource Sciences (IUNR)
Appears in collections:Publikationen Life Sciences und Facility Management

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