DSM Pocket Guidebook Volume 5: Renewable and Related ... - NREL

R E N EWABLE B R I E F 1 0
PHOTOVOLTAICS
.INTRODUCTION
Today, photovokaics (PV) is quite competitive with many low-power
utility applications where the actual amount or cost of energy involved
is less important than reliable and trouble-free remote operation. More
than 70 utilities today ore saving significant capital and operational
costs by using PV modules and arrays in low-power service applications,
including warning signs; beacons, buoys, and security lighting; waterlevel
sensors; communication links; back -up genemtor starters; special
switches on tmnsmission lines; and remote customer loads. The economic
advantage of using a PV-battery unit to serve a remote, lowpower
load mther than extending a utility distribution line depends on
the application load level and the distance from an existing load. As
a general rule, distribution line extensions of more than 500ft (152m)
for low-power loads will be less economical than apping PV. According
to the Electric Power Research lnstiMe, ''The smaller the load and the
farther it is from an existing distribution line, the more like that a PV
system will be cost-effective for the application."
• TECHNOLOGY DESCRIPTION
PV direct converts radiant energy from the sun to direct current (DC)
electrical energy. The smallest unit of a PV system is the individual PV
device or solar cell. Individual PV cells are connected together to form
a PV module. PV modules are the basic solar collectors for PV power
systems. Modules are connected together to form arrays. The total area
of modules used for an array or field of arrays is determined by the
overall PV system power level desired.
Solar cells are made from semiconducting materials, typical silicon,
doped with special additives. As long as they are exposed to sunlight,
PV devices produce an electrical current that is proportional to the
amount of light that it receives. Because electrical energy may be
needed when the sun does nat shine, stomge is often required. Batteries
are the most common form of storage. If the load requires akernoting
current (AQ, an inverter is used to convert the DC power to At By
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