(Energy Research Centre, University of Cape Town, 2006) Brooks, M. J.; Mills, I.; Harms, T. M.
The performance of a South African parabolic
trough solar collector (PTSC) module has been
characterised using the ASHRAE 93-1986 standard.
The collector is designed for component testing
and development in a solar energy research programme.
Low-temperature testing was performed
at Mangosuthu Technikon’s STARlab facility using
water as the working fluid. Both an evacuated glassshielded
receiver and an unshielded receiver were
tested, with which peak thermal efficiencies of
53.8% and 55.2% were obtained respectively. The
glass-shielded element offered superior performance
at the maximum test temperature, desensitising
the receiver to wind and reducing the overall
heat loss coefficient by half. The collector time constants
for both receivers indicate low thermal inertia
and the measured acceptance angles exceed the
tracking accuracy of the PTSC, ensuring the collector
operates within 2% of its optimal efficiency at all
times. Off-sun thermal loss results and the behaviour
of the PTSC under increased angles of incidence
are described. A description of the test system
components is given.