A methodology is developed for calculating the correct size of a photovolta
ic (PV)-hybrid system and for optimizing its management. The power for the
hybrid system comes from PV panels and an engine-generator - that is, a gas
oline or diesel engine driving an electrical generator. The combined system
is a stand-alone or autonomous system, in the sense that no third energy s
ource is brought in to meet the load. Two parameters were used to character
ize the role of the engine-generator: denoted SDM and SAR, they are, respec
tively, the battery charge threshold at which it is started up, and the sto
rage capacity threshold at which it is stopped, both expressed as a percent
age of the nominal battery storage capacity. The methodology developed is a
pplied to designing a PV-hybrid system operating in Corsica, as a case stud
y. Various sizing configurations were Simulated, and the optimal configurat
ion that meets the autonomy constraint (no loss of load) was determined, by
minimizing of the energy cost. The influence of the battery storage Capaci
ty on the solar contribution is also studied. The smallest energy cost per
kWh was obtained for a system characterized by an SDM = 30% and an SAR = 70
%. A study on the effects of component lifetimes on the economics of PV-hyb
rid and PV stand-alone systems has shown that battery size can be reduced b
y a factor of two in PV-hybrid systems, as compared to PV stand-alone syste
ms. (C) 1999 Elsevier Science Ltd. All rights reserved.