Article,
Partial shadowing of photovoltaic arrays with different system configurations: literature review and field test results
Solar Energy, (2003)
DOI: 10.1016 /S0038-092X(03)00155-5
Abstract
Partial shadowing has been identified as a main cause for reducing
energy yield of grid-connected photovoltaic systems. The impact of
the applied system configuration on the energy yield of partially
shadowed arrays has been widely discussed. Nevertheless, there is
still much confusion especially regarding the optimal grade of modularity
for such systems. A 5-kWp photovoltaic system was installed at K.U.
Leuven. The system consists of three independent subsystems: central
inverter, string inverter, and a number of AC modules. Throughout
the year, parts of the photovoltaic array are shadowed by vegetation
and other surrounding obstacles. The dimensions of shadowing obstacles
were recorded and the expectable shadowing losses were estimated
by applying different approaches. Based on the results of almost
2 years of analytical monitoring, the photovoltaic system is assessed
with regard to shadowing losses and their dependence on the chosen
system configuration. The results indicate that with obstacles of
irregular shape being close to the photovoltaic array, simulation
estimates the shadowing losses rather imprecise. At array positions
mainly suffering from a reduction of the visible horizon by obstacles
far away from the photovoltaic array, a simulation returns good results.
Significant differences regarding shadow tolerance of different inverter
types or overproportional losses with long module strings could not
be confirmed for the system under examination. The negative impact
of partial shadowing on the array performance should not be underestimated,
but it affects modular systems as well as central inverter systems.
