Application types of small wind turbines
The most common application of small wind turbines is parallel operation, i.e. the power supply of a building with simultaneous connection to the public power grid. Even if the excess wind power is fed in and paid for, the focus of power use is on self-consumption. A large part of the self-produced wind power is self-consumed. With the increasing spread of battery storage, the self-consumption rate is increasing.
One speaks of stand-alone systems when there is no connection to the power grid. As a rule, a battery then serves as a power storage device in order to be able to guarantee a permanent power supply. In remote areas, off-grid systems are often more economical than connecting these settlements to the distant power grid.
In addition to generating electricity, a small wind turbine can contribute to the water supply by driving a pump. For example, the so-called western wheels, which were used as wind pumps for water supply on farms, were widespread in the USA. The photo shows a wind pump on an island off Sardinia that has been reliably pumping water from a well for over 50 years. The piston of the pump is driven by the rotor, no electric pump is used. Using the mechanical energy of a pinwheel was used in windmills to grind grain hundreds of years ago. Another option is the generation of thermal energy. Either by using the electricity generated in an electric heater or directly by converting the mechanical energy into heat.
With grid-connected systems, the small wind turbine is connected to the local power grid. The direct current is converted into an alternating current by an inverter. Systems with an output of up to 30 kW usually feed the electricity that is not directly consumed into the low-voltage grid, either single-phase (110 – 230 V) or three-phase (400 V). Systems with an output of between 30 and 100 kW feed the electricity into the medium-voltage grid (20 kV) in one phase or into the low-voltage grid in three phases (400 V).
Small wind turbines are ideal for supplying energy to remote systems or settlements that are not connected to the power grid. These can be e.g. holiday homes, mobile homes, emergency telephones, mobile phone poles,s or sailing ships. In remote areas of developing countries, entire settlements are powered by off-grid systems.
In the private sector, systems with an output of less than 1.5 kW are usually used, which feed direct current into a battery with a voltage of up to 48 V. In addition to DC-based systems, small AC island grids are an option. This is advantageous since most electrical devices work on alternating currents. The wind power is fed into the AC or three-phase side of the stand-alone grid via an inverter for grid coupling. The grid is formed by a bidirectional battery inverter.
In order to increase the reliability of the power supply, hybrid systems are used, some of which also include diesel generators in addition to wind turbines and photovoltaic systems. The higher the share of electricity provided by renewable energies, the lower the cost of fossil fuels. Depending on the location, this can improve the profitability of the hybrid system.
The wind turbine as heating
A large part of the energy generated by wind turbines falls in Central Europe during the cold season. In autumn and winter, the wind is particularly strong, coinciding with the high demand for heat for service water and heating. A decisive advantage over solar systems, which can hardly provide any energy in winter. In very windy regions such as Brittany, there are small wind turbine operators who use the systems solely for heat generation.
Theoretically, there are various technical options for providing heat with wind energy. For example, wind power could be used to power a heat pump. The usual method of “wind heating” is to direct the direct current into the heating rod of the hot water tank.