The performance of the 30-tube water-in-glass system
used as a single-tank system is similar to a 300-L flat-plate
system with a 3.7 m2 collector. The annual solar fraction of
the flat-plate system is 77.6%, out-performing the evacuated
tube collectors because of the larger collector area.
The purpose of this investigation is not to compare the performance
of flat-plate and evacuated tube collectors of the
same absorber quality and size, since an evacuated tube
collector of the same size (3.7 m2
) as the flat plate collector
would overheat during summer periods. Instead, it aims to
provide a reasonable evacuated tube collector size as an
alternative to the typical flat-plate collector used in
Australia. The single-tank system operates with a heater
element located half-way up the tank. The hot water storage
regulation, AS1056 (1991), requires the top (boost)
portion of the tank to exceed 60 C at least once a day to
avoid legionella growth. During the TRNSYS simulations,