In Fig. 6c the effect of providing heating to the hot water cylinder is considered for the ETC system. In the case being demonstrated here, 100% of the solar fluid flow is passed through the cylinder heating coil, downstream of the ORC evaporator, before being returned to the collector (see Fig. 1).
This results in a further decrease in the enthalpy of the solar fluid stream before it is returned to the collector inlet, which in turn gives rise to the intermittency
of ORC operation being more exaggerated than in Fig. 6b.
The cumulative work output from the ORC is reduced considerably
while the cylinder is being heated (i.e. until 12:30 p.m.). From the
time instant when the upper temperature limit for hot water storage
in the cylinder (80 C) is reached, the work output from the
ORC engine increases again. Nevertheless, the early penalty in
work generation means that the total cumulative work output over
the course of the day is lower than in Fig. 6b.