Page 138 - Applied Photovoltaics

Chapter

7

DESIGNING

STAND-ALONE

PHOTOVOLTAIC

SYSTEMS

7.1 INTRODUCTION
Design of a stand-alone PV system centres on the selection and sizing of appropriate
components to meet the requirements of a particular load. Component costs and
efficiencies are required, in addition to load characteristics. Trade-offs can usually be
made between components to meet budget constraints, although system reliability and
life expectancy are likely to be compromised (Durand, 1994). Some information or
estimate of the solar insolation characteristics at the site is required, as is an
indication of the criticality of the power supply. Different design approaches are
outlined in this chapter.
Depending on the situation, major design criteria may include (Meyer, 2004):
x lowest life cycle cost—this can be three times the initial investment cost, with
extensions of battery life having a strong impact on its reduction
x tolerance of load and insolation variations
x modularity and flexibility
x ease of maintenance and repair
x quality of power supply
x reliability
x social factors.