Photovoltaic-thermal (PVT) panels combine solar thermal and photovoltaic technologies and generate simultaneously both heat and electricity. This paper looks at the potential of integrating these systems into small domestic prosumer households for the climates of Bucharest, Romania, and Strasbourg, France. First, some brief background information on PVT systems and the concept of prosumers is introduced, highlighting their features as well as the solar energy market setting in Romania and France. Next, a PVT system is proposed for a given household consumer in Strasbourg and Bucharest with the variable weather conditions corresponding to the two locations. The PVT system and the coupled consumer are modelled in TRNSYS (v17, Thermal Energy System Specialists, Madison, USA). A performance analysis is carried out in order to establish the daily instantaneous energy output and the annual energy production. The results indicate a 10–12% better performance in Bucharest compared to Strasbourg due to slightly better weather conditions. The system efficiency was assessed through various methods (first law efficiency and primary energy saving). Depending on the method used, the location and time of year, the results vary from 15% for the first law efficiency to 90% for the primary energy saving efficiency. The most suitable efficiency assessment method for this study was found to be the primary energy saving method, as it takes into account the regional differences in energy production. This study concludes that the Romanian PVT market has a good potential for adopting the technology, especially since it is currently less mature than in France.

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Photovoltaic-thermal panels are hybrid systems that combine the two types of conventional solar energy technologies (photovoltaic and thermal panels) and simultaneously generate both thermal and electrical energy in a micro-cogeneration system. Like any co-generation system, there is an optimal balance that can be achieved between the thermal and electrical energy produced. For this reason, it is important to establish the relationship and inter-connection between the two. Limited research is available on the cogeneration interaction in a PVT system, so the novelty of this article lies in the consideration of the entire energy system connected to the PVT panel, including the storage tank and the consumer demand curve, and the investigation of the thermal parametric variation. This study analyses the impact of the variation of some thermal parameters of a domestic hot water tank on the electrical efficiency of a photovoltaic-thermal panel. A model of a system of photovoltaic-thermal panels is built in a transient systems simulation program (TRNSYS) and a one-factor-at-a-time analysis is carried out for the cold-water main temperature, tank size, tank outlet flow and consumer demand curve. The results show that the variation of the outlet flow to the consumer has the highest impact on the electrical efficiency, of about 6.8%. The next highest impact factor is the size of the tank with a variation of 4.7%. Matching the profile of the consumer is also an important aspect. It was observed that the peak electrical efficiency occurs during peak consumer demand. Finally, the instantaneous variation of the thermal and electrical power of the system was analysed as a function of the temperature at the inlet of the photovoltaic-thermal panel.

This work is published under the responsibility of the Secretary-General of the OECD. The opinions expressed and arguments employed herein do not necessarily reflect the official views of the OECD member countries or the European Union. This document, as well as any data and map included herein, are without prejudice to the status of or sovereignty over any territory, to the delimitation of international frontiers and boundaries and to the name of any territory, city or area.

A micro-cogeneration biomass-based Stirling engine unit developed by the ÖkoFEN company has been tested to characterize its energetic performances. The stages of functioning have been described using polynomial equations in function of time, to accurately simulate ON-OFF regimes of functioning, in the context in which the micro-cogeneration unit would be part of a multi-country grid in accordance to the ACA-MODES Interreg program.

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