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Development of highly efficient, glazed PVT collectors with overheating protection to increase reliability and enhance energy yields

: Lämmle, M.; Hermann, M.; Kramer, K.; Panzer, C.; Piekarczyk, A.; Thoma, C.; Fahr, S.


Solar energy 176 (2018), pp.87-97
ISSN: 0038-092X
ISSN: 0375-9865
Journal Article
Fraunhofer ISE ()
Thermische Systeme und Gebäudetechnik; stagnation temperature; hybrid photovoltaic/thermal PV/T collector; low-emissivity; Solarthermie; Thermische Kollektoren und Komponenten

PVT collectors are an emerging technology which combines the generation of solar electricity and heat within a single component. Low heat losses and a high thermal efficiency are essential for the application in conventional solar thermal systems with fluid temperatures up to 90 °C. Glazed PVT collectors with low emissivity coatings offer highest energy yields. However, excessive stagnation temperatures require an adapted collector design to avoid material aging and collector failure. Two innovative PVT collectors with overheating protection are built and tested, and the effect on temperatures and performance is studied. Venting the PVT collector with ambient air reduces the maximum absorber temperatures from 148 °C to 102 °C. An innovative switchable film insulation renders an unprecedented switching range of thermal losses resulting in an uncritical maximum absorber temperature of 87 °C. Thus, conventional PV modules and inexpensive materials can be employed in collector and system, which might offset the additional costs for the overheating protection. Next to the improved reliability, also the electrical efficiency benefits from a lower temperature load.