Windmills have been around for a very long time. Relatively
short towers once hosted very large rotors with many blades to produce
the power and torque needed for things like grinding grains and
running machinery. During the 1930s, wind electric generators made their way into
rural areas where there were no electric power lines. These low-voltage machines
were primarily battery chargers and were used to power low-voltage DC home appliances.
Some were dedicated to pumping water.
Today there are a handful of manufacturers producing electricity-generating
wind turbines for both grid-connected systems and off-grid battery-charging applications.
The term turbine generally refers to the combination of blade set and
generator assembly, while the term generator refers specifically to the electricityproducing
unit.
Modern wind machines use high-efficiency generators or alternators and highly
refined blade designs and materials for maximum efficiency. There are also some
interesting and novel devices on the market that can capture energy in the wind.
These range from small rooftop wind machines to vertical axis wind turbine (VAWT)
designs. While there are niche markets and encouraging research in some new areas
of design, current best practices for harvesting wind energy center on the horizontal
axis wind turbine (HAWT).
Using Wind Energy at Home
W ind turbin esgenerate electricity by capturing the wind’s energy as it moves around two or three propeller-like blades. The blades are attached to a generator that produces electricity when it spins. The turbines sit high atop towers, taking advantage of the faster, stronger, and less turbulent wind at 100 feet or more above ground. Many locations have some potential for capturing wind energy, but the resource varies widely with location, season, and time of day.
Your neighbor down the road may have more wind available than you do, due to local conditions such as elevation, exposure, terrain, and trees or other obstructions. Most small wind turbines employ an “upwind” configuration, meaning the rotor (the blades) points into the wind and spins in front of the tower, and the assembly is oriented by a tail vane that is downwind of the rotor.
A notable exception are the Kingspan (formerly Proven) wind products (see Resources), which are downwind and do not have a tail. Downwind turbines may have an unconventional look, but they can perform just as well as their upwind counterparts.
Large, utility-scale generators and residential grid-tied systems produce alternating current (AC; the same current used by household electrical systems), but there are a number of direct current (DC) wind generators that can be used as battery chargers for off-grid applications. In either case the power must be managed and manipulated before it can be used.
Residential wind generators range in peak power generation from 50 watts to 10 kilowatts or more and may cost between $3 and $5 per peak “rated” watt to buy. As you’ll see, however, while the peak power rating of a wind generator may help you get your head around the relative size and capacity of the unit, it’s not the best measure for comparing different machines because it has little bearing on how much energy will be delivered over time.
Wind Energy
Energy, expressed in watt-hours for our purposes, is a quantity of power (wattage) produced over time. The energy produced by a wind generator is a function of:
• Average wind speed at the tower location
• Tower height (taller towers provide access to higher and more consistent wind speeds than those available closer to the ground)
• Wind speed frequency distribution, based on data showing how many hours during the year the wind blows within a certain speed range (this range of combined data points is called bin data)
• Wind turbine power curve, indicating the power produced by the generator at various wind speeds Kinetic energy, or power, available in the wind can be can be expressed by the following relationship:
Power = (air density ÷ 2) x swept area x (wind speed3)
Using Wind Energy at Home
W ind turbin esgenerate electricity by capturing the wind’s energy as it moves around two or three propeller-like blades. The blades are attached to a generator that produces electricity when it spins. The turbines sit high atop towers, taking advantage of the faster, stronger, and less turbulent wind at 100 feet or more above ground. Many locations have some potential for capturing wind energy, but the resource varies widely with location, season, and time of day.
Your neighbor down the road may have more wind available than you do, due to local conditions such as elevation, exposure, terrain, and trees or other obstructions. Most small wind turbines employ an “upwind” configuration, meaning the rotor (the blades) points into the wind and spins in front of the tower, and the assembly is oriented by a tail vane that is downwind of the rotor.
A notable exception are the Kingspan (formerly Proven) wind products (see Resources), which are downwind and do not have a tail. Downwind turbines may have an unconventional look, but they can perform just as well as their upwind counterparts.
Large, utility-scale generators and residential grid-tied systems produce alternating current (AC; the same current used by household electrical systems), but there are a number of direct current (DC) wind generators that can be used as battery chargers for off-grid applications. In either case the power must be managed and manipulated before it can be used.
Residential wind generators range in peak power generation from 50 watts to 10 kilowatts or more and may cost between $3 and $5 per peak “rated” watt to buy. As you’ll see, however, while the peak power rating of a wind generator may help you get your head around the relative size and capacity of the unit, it’s not the best measure for comparing different machines because it has little bearing on how much energy will be delivered over time.
Wind Energy
Energy, expressed in watt-hours for our purposes, is a quantity of power (wattage) produced over time. The energy produced by a wind generator is a function of:
• Average wind speed at the tower location
• Tower height (taller towers provide access to higher and more consistent wind speeds than those available closer to the ground)
• Wind speed frequency distribution, based on data showing how many hours during the year the wind blows within a certain speed range (this range of combined data points is called bin data)
• Wind turbine power curve, indicating the power produced by the generator at various wind speeds Kinetic energy, or power, available in the wind can be can be expressed by the following relationship:
Power = (air density ÷ 2) x swept area x (wind speed3)
