Stand-alone Wind and PV Solar Electric Systems
Stand alone
wind or PV-solar systems are mainly used in homes,
communities and farms located far away from utility lines.
In these cases,
grid connection is typically expensive: running a power line to a
remote site from the utility grid can involve prices in the
range $15,000 to more than $50,000 per mile (prices depend on the type of
ground) and that may impose stand-alone solutions.
Energy independence
In some cases,
a strong interest in gaining energy independence may also be an explanation for stand-alone wind or photovoltaic systems.
Grid-tied systems are always, even if in a low degree, dependent
on politic and strategic decisions of the utilities and electric
provider companies, which can explain the option for stand-alone
systems.
Wind conditions
Living in an
area with sufficient wind speeds are crucial, when planning a stand-alone wind electric system:
a minimal annual average of
4.4 meters per second (10 miles per hour) is a common
reference.
Solar resources
The electrical
energy produced by a PV array depends upon several elements that
should be considered when making a decision about a stand-alone
system: the solar resources (the annual average of hours of full
sun), the collector orientation or the tilt angle module
efficiency.
Solar resources
are important. If a site receives, say, an annual average of 5
hours of full sun, while another receives only 2 or 3 hours, the
annual energy produced by those systems will differ
significantly. PV systems are less productive in non-sunny
areas. Differences of 30% due to different solar resources are common.
See
graphic
below, to assess the impact of solar resources:
Source:
Montana Green Power
Stand alone systems & Other
energy resources
Solar and
wind power are - in most climate zones and areas -
usually intermittent by nature, and a stand-alone system should
take that fact into account. A plan involving other energy
resources is often required, in order to surpass the electric energy
power deficit during down times. Batteries or a hybrid wind and
solar systems may be part of the solution, but grid-tied systems
– whenever possible and economically viable - are the easiest
and truly definitive solution to those deficits...
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