Solar electric technology involves the direct conversion of sunlight
to electricity. For a wide variety of applications, it is a compelling
alternative to conventional sources of fossil fuel-based power.
It is:
- silent
- non-polluting
- renewable
- extremely
durable
- virtually
maintenance- free
Typical applications
for photovoltaics today:
- lighting
and security
- water
pumping and irrigation
- communications
- remote
monitoring equipment
- aids
to navigation
- remote
refrigeration
- portable
power
- village
power
- electricity
for individual buildings or entire communities
- supplementing
the utility grid
Cells,
Modules and Arrays
Photovoltaic electricity is produced by an array of individual
PV modules electrically connected in series and parallel to deliver
the desired voltage and current. Each PV module, in turn, is constructed
of individual cells also connected in series and parallel. Dozens
of solar cells are connected together to produce a PV module.
The number of cells determines a module's size and power. Modules
are typically available in ratings from less than 10 watts peak
(Wp) to 300 Wp.
There are several basic types of PV modules commercially available
today--those made from crystalline silicon, those made from amorphous
silicon and those made from other thin-film PV materials such
as copper-indium-diselenide (CIS) and cadmium telluride(CdTe).
While crystalline silicon modules have dominated the market since
the 1970s, CdTe modules appear poised to offer solar electricty
at substantially reduced costs in the near future.
Stand-alone versus Utility-interactive
PV systems from buildings can be either stand-alone or grid-connected.
In a stand-alone system, the building has no connection to the
utility grid and often relies on a bank of batteries to store
power for use at night and during times of limited sun. In a utility-interactive
system, the building receives electricity from both the PV array
and the utility grid.
In many utility-interactive systems, surplus electricty from the
PV array is exported to the utility grid, turning the electric
meter backwards. This "net metering" arrangement--when
the utility is paying PV producers at the same kilowatt-hour rate
they're charging--is the law in many states and will likely soon
be available in Hawaii as well. With net metering, the utility
grid becomes the storage medium in place of on-site batteries.
Market Trends
Over the past 11 years, the global PV industry has enjoyed a compounded annual growth rate of over 40 percent. Over that period, crystalline silicon has remained the dominant semiconductor used by the industry. Crystalline silicon has established itself as the most efficient element in converting sunlight to usable electricity and, since the 1950s, the most durable and reliable PV material. However, with all the newcomers into the PV manufacturing industry in recent years, thin films (e.g., cadmium telluride, amorphous silicon, copper indium gallium selenide) seem poised to cut into the 85+ percent market share that crystalline silicon enjoys. The sunlight-to-power efficiency of thin films has been as little as half or less compared to crystalline silicon. The promise of thin films has always been the potential for significantly lower production costs. Will this promise come closer to reality in 2009?
PV Industry Growth
Graphs courtesy of Paula Mints, Principal Analyst, Navigant Consulting PV Services Program.
|
