The model is used in order to evaluate the annual generation of electrical
energy along with the provision of domestic hot-water (DHW) from the thermal energy output, by using
real climate-data at high temporal resolution. The model considers the effect of a non-uniform temper-
ature distribution on the surface of the solar cell on its electrical power output. An unsteady 3-dimensional
numerical model is developed to estimate the performance of such a collector. The model allows key
design parameters of the PVT collector to vary so that the influence of each parameter on the system
performance can be studied at steady state and at varying operating and atmospheric conditions. A key
parameter considered in this paper is the number of glass covers used in the PVT collector. The results
show that while the thermal efficiency increases with the additional glazing, the electrical efficiency de-
teriorates due to the higher temperature of the fluid and increased optical losses, as expected. This paper
also shows that the use of a dynamic model and of real climate-data at high resolution is of fundamen-
tal importance when evaluating the yearly performance of the system. The results of the dynamic simulation
with 1-min input data show that the thermal output of the system is highly dependent on the choice of
the control parameters (pump operation, differential thermostat controller, choice of flow rate etc.) in
response to the varying weather conditions. The effect of the control parameters on the system’s annual
performance can be captured and understood only if a dynamic modelling approach is used. The paper
also discusses the use of solar cells with modified optical properties (specifically, reduced absorptivity/
emissivity) in the infrared spectrum, which would reduce the thermal losses of the PVT collector at the
cost of only a small loss in electrical output when the selective coating is applied.
© 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license