Across the globe, wind turbines seem to be popping up everywhere; in our cornfields, off the shores of our beaches, and even on some of our rooftops. Wind energy is sweeping the nation on big and small scales and is currently one of the most cost-efficient renewable or alternative energy systems. Wind turbines are essentially electrical generators that utilize the kinetic energy of the wind to produce emission-free electricity. This increasingly popular and simple technology can generate substantial amounts of electricity for homes and buildings, which in turn reduces electricity bills by offsetting electrical consumption from the grid. For these reasons, residential wind turbines are an excellent option for generating power in almost any off-grid living application.
Residential wind turbines are typically mounted on a tower to increase exposure to stronger winds. The entire system typically includes a tower, the turbine unit itself, and several additional components often referred to as “balance-of-system” components.
- Towers: Because wind velocity increases with altitude, residential wind turbines are usually mounted on a tower. The higher the tower, the more electricity the wind turbine will tend to generate.
- Turbines: Most residential wind turbines have a horizontal axis that points upwind, and includes three or more blades, which are typically composed of fiberglass.
- Balance-of-System Components: The balance-of-system, sometimes referred to as a stand-alone system, controls the storage, conversion, and distribution of electricity for domestic use. The parts of this system may include an inverter (power conditioning unit), electrical disconnect switch, wiring, charge controller, storage batteries, grounding system, and foundation for the tower.
Types of Small Wind Turbine
1. Horizontal-Axis Wind Turbines (HAWT)
HAWTs consist of a horizontally-oriented rotor shaft, which transfers the kinetic energy from the blades to the gear box and generator. Small wind turbines utilize a small wind vane to orient themselves in the optimum direction. Because wind speeds are often too slow to produce sufficient rotational velocity of the generator components, most modern designs include a gearbox that converts the slow rotation of the blades into a rotational velocity that is sufficient to drive the electrical generator.
2. Vertical-Axis Wind Turbines (VAWTs)
The main rotor shaft of a VAWT is oriented vertically. Because a vertical-axis wind turbine can collect wind from any direction in 360 degrees, they do not need to be pointed in any particular direction to be effective. This is advantageous on sites where wind direction is highly variable and when legal or physical restrictions require that the turbine be fixed to the building. The gearbox and generator are located at the base of the unit, improving accessibility for maintenance. Modern designs have solved the problem of relatively low rotational speed with higher torque present in old designs by reconfiguring the blades into a helical design.
How Residential Wind Turbines Work
After the wind turbine has been installed, typically mounted on a rooftop or in a nearby yard, the motion of the wind spins the blades of the turbine and the rotor captures the wind’s kinetic energy. This kinetic energy is then converted into a rotary motion that drives the generator, converting it into 100% carbon-free electricity. In very high winds, many turbines have an automatic overspeed-governing system that prevents the rotor from spinning out of control. The output is then connected to the wiring system of the house via a breaker panel, or to the balance-of-system components (inverter, charge controller, batteries, etc.)
Wind Turbines vs. Solar Panels: Which Should I Choose?
In many off-grid living applications, it is advantageous to utilize both wind turbines and solar panel systems. Depending on location and the quality of the equipment that is installed, wind turbines can be an excellent supplement to your off-grid power production setup. At locations with a very low average wind speed, however, wind turbines may not prove to be cost-efficient enough to be installed. It is therefore wise to consider as many factors as possible before investing in a new electricity generation system.
Advantages of Small/Residential Wind Turbines
- Electricity can be generated during day or night under windy conditions
- Wind turbines generally occupy less rooftop or land area
- Available for purchase in a wide-range of sizes/output, making it relatively simple to select the most appropriate equipment for individual spending budgets and electricity needs
- Wind turbines, on average, are currently slightly more cost-efficient than solar panels and range between 4-6 cents/kWh
Disadvantages of Small/Residential Wind Turbines
- Moving parts require occasional maintenance and replacement in some cases
- Adding more wind turbines to one property is often considered obstructive or an “eye sore”
- Moving blades are potentially hazardous to birds
- Can be susceptible to lightning damage depending on surrounding elevations
- Cost efficiency (in terms of $/kWh) is highly dependent on local average windspeed
Advantages of Solar Modules
- Solar panels require little to no maintenance
- More panels can be easily added; better for scaling-up off-grid power production
- Often more reliable and covered by longer warranties
- Cost efficiency (in terms of $/kWh) is more stable for any location with sufficient sun exposure
Disadvantages of Solar Modules
- Panels need to be cleaned occasionally
- Maximum electricity production requires clear conditions during the day (less optimum for regions that experience frequent or prolonged overcast)
- Solar panels occupy more rooftop or land area
- Solar panels, on average, are currently slightly less cost-efficient than turbine systems at approximately 11 cents/kWh