Abstract:
In order to predict accurately the performance of solar-thermal
or hybrid PVT systems, it is necessary that the steady-state
and dynamic performance of the collectors is understood. This
work focuses on the testing and detailed characterization of nonconcentrating
PVT collectors based on the testing procedure
specified in the European standard EN 12975-2. Three different
types of PVT collectors were tested in Cyprus under outdoor
conditions similar to those specified in the standard. Amongst
other results, we show that that poor thermal contact between
the laminate and the copper absorber can lead to a significant
deterioration in thermal performance and that a glass cover improves
the thermal performance by reducing losses as expected,
but causes electrical losses that vary with the glass transmittance
and the incident angle. It is found that the reduction in electrical
efficiency at large solar incidence angles is more significant than
that due to elevated temperatures representative of water heating
applications. Dynamic tests are performed by imposing a
step change in incident irradiance in order to quantify the collector
time constant and effective heat capacity. A time constant of
8 min is found for a commercial PVT module, which compares
to <2 min for a flat plate solar collector. The PVT collector time
constant is found to be very sensitive to the thermal contact between
the PV layer and the absorber, which may vary according
to the quality of construction, and also to the operating flow rate.
Description:
Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .
