Stand-alone or grid-connected system?
Small-scale wind power is particularly suitable for remote off-grid locations
where conventional methods of supply are expensive or impractical. Most
small wind turbines generate direct current (DC) electricity. Off-grid
systems require battery storage and an inverter to convert DC electricity
to AC (alternating current - mains electricity).
You also need a controller to divert power to another useful source (e.g.
space and/or water heaters) when the battery is fully charged.
It's common to combine this system with a diesel generator for use during
periods of low wind speeds. A combined wind and diesel system gives greater
efficiency and flexibility than a diesel only system. It allows the generator
to be used at optimum load for short periods of time to charge batteries
when there is little wind, rather than by constant use at varying loads.
Wind systems can also be installed where there is a grid
connection. A special inverter and controller converts DC
electricity to AC at a quality and standard acceptable to
the grid. No battery storage is required. Any unused or
excess electricity can be exported to the grid and sold
to the local electricity supply company.
Connecting a residential wind turbine to an electrical
grid allows homeowners to produce their own electricity but still have
access to electricity even when the wind isn't blowing. This option eliminates
the need for batteries by allowing a homeowner to use energy from the
grid when not enough energy is provided by the wind turbine. It also allows
homeowners to sell excess energy back to the utility. The technical and
economic issues of connecting to the grid varies depend on the state and
utility's policy. According to the Michigan Wind Energy System Sitting
Guidelines Draft #5 the rules for connecting a residential wind turbine
to the grid are as follows:
"Utility Notification and Interconnection: No small wind energy
system shall be installed until evidence has been given to the local government
that the utility company has been informed of the customer's intent to
install an interconnected customer-owned generator. An interconnected
customer-owned generator shall comply with Michigan Public Service Commission
and utility requirements. Off-grid systems shall be exempt from this requirement."
There are 4 components to most grid-tie systems: the wind turbines, the
tower, the Whisper Link™ controller, and the power inverter. In
addition, optional items such as battery banks and remote controls are