Environmental Engineering Reference
In-Depth Information
Solar collector cycle efficiencies are usually between 20 and 50 per cent in
temperate climates. Next to the build quality of the system, the solar fraction
is the dominant factor on the cycle efficiency. The solar collector cycle
efficiency decreases significantly with increasing solar fraction.
To calculate the
saved primary energy E
PE
, the electrical energy demand
E
pump
of the pump and the control unit for the solar cycle, the primary energy
efficiency
η
E
of the public
electricity utilities must be considered. Hence, the amount of saved primary
energy is:
η
aux
of the auxiliary heater and the efficiency
(3.61)
if the energy demand for the production of the solar thermal system is
neglected. The primary energy demand of the solar collector pump is between
2 and 15 per cent of the collector output. To keep the pumping energy demand
low, the diameters of the pipes and the design of the pump must be estimated
carefully. The simulation programs on the CD-ROM accompanying this topic
can provide further advice for this task.
