Wind turbines are generally divided into two broad categories based on their rated capacity and their intended applications. Small wind turbines are typically less than 50 kW in size, but can be as large as 250 kW and are designed for use in residential, agricultural, small commercial and some industrial applications. In all of these applications, the turbine(s) are providing energy for the end user to offset the use of grid power.
Large wind turbines have rated capacities ranging from 660 kW to 1,800 kW (1.8 MW) and are designed for use in electricity generating power plants. Large turbines are typically deployed in wind farms and are intended to provide wholesale bulk electricity production for delivery on the local transmission network
Small wind turbines can be grid-connected for residential or industrial electricity generation or they can be used in off-grid applications such as water pumping or battery charging. Small turbines are typically installed as a single unit or in small numbers. The smallest turbines (with power ratings less than 1 kW) are normally used to charge batteries for sailboats, cabins, and small homes. Turbines with power ratings between 1 kW to 20 kW are normally used for water pumping, small businesses, residential power, farm applications, remote communication stations, and government facilities.
They are often found as part of a hybrid system that can include photovoltaic cells, grid power connections, storage batteries, and possibly back-up diesel generator sets. Turbines rated at 50 to 250 kW are used in light commercial/industrial, larger farms, and village power applications.
Large wind turbines are most commonly deployed in large arrays of multiple turbines. Less common, but increasingly of interest to municipalities or electric cooperatives, large turbines are also installed in distributed generation applications that consist of a single or a few turbines connected directly to a distribution line. Many large wind turbine manufacturers are offering models in the 1 MW range.
Wind turbines as large as 1.8 MW are available for land-based applications in the U.S. For offshore environments, manufacturers are testing designs in the range of 3-5 MW.
Examples and information pertaining to both large and small wind turbines are included in this guide. Although there is some overlap, the majority of the technical issues, permitting requirements, and operating procedures are different for large and small wind turbine applications. Therefore, it is important to differentiate and address the large and small wind turbine applications separately rather than trying to address them with the same set of regulations or review processes.
Large-scale applications are likely to have more impact on a community.