Wind - Micro

Short Cuts for:

Micro Wind

Micro wind turbines convert the kinetic energy from wind power to useful energy (either electricity or heat). The rated capacity of micro wind designs varies from 0.1 to 15 kW. They are available in two basic configurations: rooftop-mounted and pole-mounted.

The main components of a micro wind turbine are:

• An aerodynamic rotor – converts the kinetic energy in the wind to rotational motion
• A generator – generates electricity from the rotational motion of the rotor
• Electronic control – controls the electrical output from the rotor and the safe operation of the turbine
• Mechanical furl – typically fins which keep the turbine pointed into the wind in low wind speeds and move the rotor out of the wind in high wind speeds
• Inverter – safely converts the power to a compatible format to the national grid

Rooftop-mounted wind turbines (Fig. 1) require a solid section of building at the roof line to directly attach the turbine; generally they are bolted to an exposed side of a building or mounted on a stand on a flat roof. Sufficient clearance above the apex of the building should be provided to enable the wind turbine to take advantage of the wind resource around the building. The electricity generated by the wind turbine is fed to an inverter installed within the building which is typically connected to the grid via a distribution board. Alternatively, in applications where grid connection is not preferred or not possible, the electricity generated from wind power can be fed directly to immersion heaters in the hot water storage tank in the building.

Pole-mounted wind turbines (Fig. 2) require a small area of land for up to 5m2 of foundations and sufficient space to winch up the turbine. As a general rule of thumb, the tower for the turbine should be sized to ensure the rotor is sited 10m above the nearest obstacle within 100m of the turbine. The electricity generated by the turbines is fed down the tower, through the foundations and buried underground back to a building where it is connected to the grid via a distribution board.

Applications

Micro wind power turbines are applicable in locations where:

• The mean wind speed is greater than 5 m/s at hub height
• There is good exposure to the prevailing wind directions
• There are no planning constraints to development (designated areas and listed buildings can be an issue)

Rooftop or pole-mounted micro wind turbines can be used in low density domestic applications and could supply a good proportion of the total energy demand. Rooftop or pole-mounted micro wind turbines can also be used in commercial applications to reduce energy consumption and CO2 emissions.

Micro wind turbines can be used effectively in hybrid applications with solar PV, hydropower, solar thermal, heat pumps and biomass heating. With solar PV and hydro they are simply connected together through an inverter to supply a greater proportion of renewable electricity to a building. When used in conjunction with solar thermal, heat pumps or biomass, they can be used to supply (indirectly) the electricity required to run the pumps in the systems; thus supplying a significant proportion of renewable energy to a building.

Financial and Environmental Benefit

The current capital cost of a micro wind turbine is roughly £3,000 per rated kW installed. The annual energy yield is typically 1,000 kWh per rated kW installed at a location with a good resource and exposure to the prevailing wind directions. This gives a current payback period of between 12 and 15 years. Annual saving in CO2 emissions are 0.4 tonnes per rated kW in a grid connection application and 0.2 tonnes in a heating application