Windmill water pump - Guanajuato Mexico (C) Daniel FriedmanWind Turbines & Wind Generator Systems
Homeowner's guide to renewable energy systems: wind

  • WIND ENERGY SYSTEMS - home - CONTENTS: description of wind energy system parts, controls, circuits, history. Lists of wind turbine generator equipment suppliers, designers, installers. Photos of wind energy systems, wind energy how-to books. Examples of wind powered equipment, photos, windmills, water pumps.Life expectancy & maintenance costs for wind energy systems. Windmills used as well pumps for water supply. Windmills used as electrical generators. Speed control and governors for wind generators and windmills. Aer-Motor Company of Chicago, IL & San Angelo TX - antique windmill photographs
  • POST a QUESTION or READ FAQs about buying, installing, using, maintaining wind energy systems: wind turbines
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Wind generator guid for homeowners:

This article describes common types of windmills used for water pumping and electrical energy generating, from Cretan wind sails to Dutch Windmills to modern wind turbine electrical generator systems. Our page top photo shows a wind generator installed by Aero-Solar in San Miguel de Allende, Mexico where by 2010 many local solar & wind power companies offered wind turbine and solar power generation installation services.

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Wind Energy Systems & Wind Turbine Controls & Circuits

What is Wind Energy and How is Wind Power Generated?

Wind generator in San Miguel de Allende Mexico (C) Daniel Friedman 2010

[Click to enlarge any image]

According to the Pennsylvania DEP who provide a brief introduction to wind power, wind energy systems are mechanical or electro-mechanical equipment that turn the force of moving air (wind) into mechanical energy (such as operating a mechanical pump to lift water from a well into a reservoir) or into electrical energy (operating a wind turbine or motor that converts the rotation of a wind-turned shaft into electrical energy). The text below is adapted from that source:

Wind power, in its most basic form, is taking the breezes and winds that you feel on your face or that cause a flag to flap and converting it into energy that can be used in other processes. The sail on a boat is among the most common examples. When wind hits the sail, it's converted into motion that carries the craft over the water.

Here for reasons of historic interest we include wind-operated mechanical windmills that traditionally were used as water pumps or to mill grain. But consonant with modern interests, our focus is on using wind for electricity generation.

Electrical energy is produced from wind by wind turbines mounted on towers, similar to the small unit in the photograph shown below. On a wind turbine, the large blades, or rotor, of the turbine capture the wind's energy and begin turning.

The wind turbine rotor, rotating as the blades are pushed by the wind, drives a shaft inside the nacelle (shell) of the wind-turbine (or electricity-generating motor that is located directly behind the blades). The nacelle contains the drive train (including the electrical generator).

The rotor and nacelle rest on top of a tower that can range from 30 feet to over 200 feet tall. The remainder of the turbine consists of equipment to control the turbine and connect it to the electricity grid so that the power can be used.

Wind speed is an important variable in determining how much electricity a turbine produces. The energy in wind is a cube of its speed. A wind speed of 11 miles-per-hour will produce 30 percent more energy than a wind speed of 10 miles-per-hour. Areas of the commonwealth have received different classifications based on wind speed. To see the wind speed for your area, check out wind speed maps for your local area. In PA wind speed maps are provided by the PA DEP.

Modern wind generators (such as the small model shown in our page to photo) use advanced propeller designs whose blades maximize lift and minimize drag. Some propellers bend in high winds to avoid overspeed or damage. Both two-bladed and three-bladed propellers are used. On large wind generators the propellers may be more than 125 feet in diameter.

Wind generating towers, Oxaca, Mexico (C) Daniel Friedman

Above: wind generators at a wind energy generating station on the coast of Oxaca, Mexico in the Isthmus area of Southern Oxaca.

In January 2010 the New York Times reported that the U.S. is close to producing 2 percent of its electricity from wind turbines, and that wind power production grew in the United States during 2008 and 2009 by a total of 57%. [2008 (18%) and 2009 (39%)]., adding 9,900 megawatts of electrical energy in 2009 alone (according to the American Wind Energy Association).

Use of wind power and its increased growth may help reduce emissions of gases that cause the increasingly rapid worldwide problem of global warming. In January and February 2010 the New York Times reported that most of the wind turbines and wind energy being installed in the U.S. as well as most of the solar panels being used in the U.S. are being produced in China, and that G.E. (General Electric) makes nearly half the wind turbines used in the United States. U.S.

Most of this wind power growth was in large wind turbines delivered to wind farms primarily in Texas, Iowa, California, Washington, and Minnesota, and aided by President Obama's economic stimulus package.

Put in context, this was about the same amount of energy production increase in the U.S. as was provided from growth in production of natural gas, and the combination of those two energy sources accounted for 80% of all new electricity generation capacity in the country. By 2020, experts report, energy derived from wind power could be about 180,000 megawatts. - The New York Times 1/26/2010.

Floating Windmills: Interesting wind power developments in 2014 included Japan's construction of a new 350 ft. high wind-generating station 12-miles off Japan's cost near the (radioactive leaking) Fukushima nuclear reactor station. The project intends to construct 140 wind turbines and to be capable of generating a gigawatt of electricity by 2020. - The New York Times 10.25.13

Examples of Wind Generators & Windmills for Power Generation or Water Pumping

Traditional Dutch Windmills and Vertical Axis Wind Powered Water Pumps

The Dutch windmill (below left) is a traditional horizontal-axis slow-speed windsail - suitable for pumping water. The split-barrel windmill (below right) is a low-cost home-made water pump system.

Antique horizontal axis Dutch windmills

Old windmill on the city rampart at Montfoort, Holland (C) Daniel Friedman

Our photos show two wind power systems: the old four-arm classic windmill on the city rampart at Montfoort, Holland (far left). Four-arm slow-speed windmills had propellers as large as 100' in diameter. Some have been converted to production of electrical energy, producing as much as 8 KWH in 20 mph. winds.

Vertical axis windmills

Oil-barrel otor wind generastor (C) Daniel Friedman

A home-built vertical-axis barrel rotor wind energy system in El Charco, in San Miguel de Allende, Mexico is shown here.

The vertical axis windmill has the advantage that it does not have to be oriented towards wind-direction.

The slow axis speed and the 20% efficiency of the split barrel design means that like the Dutch windmill above, these two wind energy systems are most often suitable for water pumping applications.

Other more efficient vertical axis windmill designs have been used or experimented with since the 1930's in the U.S., including the Darrieus vertical-axis rotor that looks like an oval embroidery hoop to a wind power novice.

Vertical axis wind turbines (in the 1970's) were not self-starting and needed an electric motor to begin activity.

Alternative vertical axis wind generator designs include the variable-pitch Cyclo-turbine (4KW at 25MPH wind) and a double-rotor helical wind generator.

Sail Windmills

Other than the Dutch traditional windmill (above left) originated in Crete and other Mediterranean countries where they have been used for water pumping for generations, a Cretan sail windmill is also a slow-speed system (tip speed ratio 0.75:1) but this inexpensive wind system is made of wood and sailcloth, turning at a maximum of about 50 rpm. In high winds the sails are reefed.

Sail windmills for electrical energy have been produced as home-made systems capable of generating about 200 watts at 15 mph winds. - McGuigan.

Multi-blade Windmills or "Fans" used for Pumping Water

Our page top photo shows a multi-blade water pumping windmill in use in Guanajuato, Mexico - these fans have been in widespread use in North American since the 1800's where on ranches and farms they have been used to produce water for both human and livestock use.

Water Pump Windmills: Photos of Windmills Used as Well Pumps & The Aer-Motor Windmill Company of Chicago, IL

Wind generator Atascadero San Miguel de Allende (C) Daniel Friedman

The windmill in our photograph was used for decades to pump water into a local reservoir tank for distribution in the Atascadero neighborhood of San Miguel de Allende, Mexico.

For speed control traditional windmills of this type were able to adjust the direction of the tailpiece to divert the fan blades from the oncoming wind direction if wind speed was excessive.

This windmill was built by the Aer-Motor Windmill Company (of Chicago, IL in our photo, presently in Texas), and served as a water source for decades. Aer-Motor Windmill has been producing windmills since 1888. Here is a close up of the windmill top, showing the company's name and "Chicago" on the tail. Quoting from the Aer-Motor Windmill company's literature,

Aermotor Windmill has a very interesting 118 year business history. However, one simple truth stands undiminished by time or geography. Aermotor Windmill has continuously manufactured windmills since 1888 and is the only windmill manufacturer in the USA. There is only one genuine Aermotor windmill.

Aer-Motor windmills are still produced and are available with wheel diameters from 6' to 16' and on towers from 21' to 60' in height.

Water pump windmills of this type use a cylinder pump operated by an eccentric crank. As the windmill wheel rotates the eccentric crank raises and lowers a rod. At the bottom of the rod a cylinder pump lifts a column of water from the bottom of the well up into a water reservoir.

Recently this water mill was converted to use an electric water pump instead of the windmill and the wind machine has been retired, remaining principally as a local landmark. Here is a photograph of the pump motor used to convert this water source to electric rather than wind power.

Wind Generator Rotor Speed Control

Aer Motor Tailpiece (C) Daniel Friedman

Rotor or Sail Speed Governors are required on all high-speed wind generators and pumps to avoid both damage and danger from excessive rotor speeds that otherwise occur in high winds.

The windmill in our Aer-Motor water pump windmill photograph (above left) was used a hinged tailpiece or rudder to either face the wheel into the wind or in high winds, to "feather" the wheel at right angles to the wind to reduce or stop its rotation.

For speed control traditional windmills of this type were able to adjust the direction of the tailpiece to divert the fan blades from the oncoming wind direction if wind speed was excessive.

What are Typical Wind Generator Towers & Turbine Heights

Wind turbine installed in Herefordshire, England (C) Daniel Friedman

Above: a wind turbine installation in Herefordshire, England. Unlike the huge Oxaca wind turbine farm illustrated in other photos on this page, walking through Herefordshire we were more likely to find individual, isolated wind-turbine installations.

Tower height makes the most significant difference in wind generator output [taller is better], while site selection may be similarly important in avoiding turbulence or blocked winds.

Wind energy system heights vary significantly, from small rooftop mounted units on buildings in some areas, to common wind farm turbine heights of 80 meters (263 feet) to the turbine or, depending on blade length, a total height of about 112 m (370 feet) above ground.

Proven Energy who produce small scale wind turbine systems provides system masts are 11m (36 ft) and 15m (50 ft) tall.

Life Expectancy & Noise of Wind Generators & Turbines

Wind generating towers, Oxaca, Mexico (C) Daniel Friedman

Above: wind generators at a very large wind energy generating station on the coast of Oxaca, Mexico. Located in a famously windy area on the Oxacan coast, these towers were, to my ear, very quiet even on a particularly windy day. This is an area of high winds and low population density.

The expected life of any renewable power source will vary by many factors, as we list and describe here. We collect and describe some of them here, and we develop a chart of trends in the anticipated life of wind generators by age, type, etc. [Contributions welcome, CONTACT us.]

Wind generating towers, Oxaca, Mexico (C) Daniel Friedman

In a casual inspection of several kilometers of wind turbines as we drove along the coastal highway in the Isthmus area of Mexico (Southern Oxaca) it was easy to spot a few turbines that apparently had had lubrication issues, such as the unit above, an Acciona wind turbine. Subjectively it looked as if about 5% of the turbines were not in operation. Interestingly, lubrication failures were not among the common wind turbine life expectancy factors I found when researching industry sources.

Current estimated life for modern wind generator turbine designs range from 20 to 30 years. Here are some wind generator life estimate sources:

NWEA: 20 years

Proven Energy, UK: 20 - 25 years, extendable to 40 years with turbine refurbishing. Quoting:

Proven Energy wind turbines [3.2kW, 6kW and 15kW] have an estimated life and design expectancy of around 20-25 years. Throughout this time, the turbine may need some parts replaced, similar to replacing parts in a car throughout its lifetime. Regular servicing and maintenance will ensure that your wind turbine will have the best chance of achieving or even exceeding its life expectancy.

National Wind: 20 to 30 years

But there can be considerable variation in both wind system life and its operating cost, depending on the factors we list below.

Factors Affecting Wind Energy System Life & Operating Costs

Wind generator San Miguel de Allende, Mexico (C) Daniel Friedman

According to Mick Sagrillo, Sagrillo Power & Light , writing for AWEA, factors affecting and improving the typical (in 2010) 20-year life expectancy of a wind energy system include:

According to Proven Energy who describes the annual service for a modern wind generator,

The servicing procedure is very simple - once a year, the turbine is lowered to ground level (using the hinged tower), the covers are removed and a full service of parts is conducted before the tower is raised and secured.

Commonly-cited wear parts on wind generators include:

Wind generator too low (C) D Friedman

1 = significant costs to repair/replace

2 = usually minor maintenance cost items

Typical Maintenance Costs for Wind Energy Systems

AEWA recommends that while wind system maintenance and repair costs will not be uniformly distributed over the life of the system, installers should allocate one percent of the installed cost of a wind energy system [per year] for operation and maintenance expenses over the life of the system.

For wind generators using a gear box drive rather than direct drive generators, annual gear box lubrication changeout doubles the estimated maintenance cost.

Wind Generator Motors - Evolution of Efficiency, Reduction in Noise

Early electrical generators using wind power operated using a copper-wound electric motor and carbon-arc brushes. Older wind energy texts such as McGuigan point out that the life expectancy of early motor generators was quite variable, from 20 years to just a year or so. Modern wind generators and turbines use alternators, eliminating the brush design, combined with a AC to DC rectifiers to produce DC electrical energy that is stored in batteries.

The New York Times, describing the wind and solar energy project in Tocco de Casuaria, in central Italy, reported (29 Sept 2010) that Tocco was chosen for an early European Union wind power demonstration project in 1989. "It had two inefficient wind turbines installed that lasted about a decade (half the wind turbine life expectancy in 2010) and were not replaced, meeting at best 25 percent of the town's electricity requirements.

According to the Times, Residents called the 1989 wind power installations 'sacks of noise' ". The Times article pointed out that recent improvements in wind turbine technology, quiet motors, and increasing costs for electrical energy prompted Tocco de Casuaria, to take a second look at wind power. Tocco (population 2700) installed two new wind turbines in 2007 and two more in 2009, now producing more electrical energy than the town consumes, and joining more than 800 Italian communities producing more energy than they consume.

Wind Generator or Turbine Noise Factors

According to National Wind, the following factors affect the [human-perceived] noise produced by wind energy systems:

National Wind describes the perceived noise of a modern wind generator installed to current standards as about that of a typical kitchen refrigerator. [We note that the noise of refrigerators itself varies quite widely depending on motor type, motor location, sound insulation, and fan use - Ed.]

Wind Generator Tower Height & Tethered Lighter-than-Air Wind Generators

Tethere wind generator, Amick, from U.S. Patent illustrations, adapted 2014

The relationship between wind generator power and wind speed is stated as

P = 1/2 d AV3

where P is power available at the turbine rotor, d is the density of the air, A is the swept area of the rotor, and V is the wind speed. At any given location, we have no control over air density, and for a given wind generator with the rotor diameter it was bestowed with, the only real variable is V, wind speed.

Therefore, we can rewrite the equation to say P~ V, or more appropriately P~V3. ... taller towers result higher wind generation. The reason is reduced ground drag. As you get away from the surface of the earth, ground drag (or friction) on the wi nd decreases, and V goes up. V3 amplifies that increase - Sagrillo (2005)

Illustrated at left is a sketch of a lighter-than-air wind turbine generator adapted from patent illustrations from Amick (2008).

Sagrillo continues to note that at comparatively lower wind generator tower heights common in 2005, [and probably as a general rule] increasing an example tower's height (for example studying data for a wind tower in North Dakota), from 42 feet to 84 feet increased the wind generator's available power by 188%. In a different example using a home-wind energy site in Illinois Sagrillo notes that increasing a tower height from 30 feet to 120 feet found an average wind speed increase of just 3 mph produced a 215% increase in available power.

What about achieving much higher effective wind generator heights than those practical with physical towers? In a wind industry development worth watching, in March 2014 The New York Times reported on the Buoyant Airborne Turbine or "BAT", a helium-filled donunt-shaped wind turbine under development by Altaeros Energies who are testing an airborne wind turbine in Alaska.

The Times article noted that wind turbines atop towers 300 to 400 feet high in Michigan, Ohio, and Indiana are able to produce electrical power at rates competitive with coal as an energy source - at prices close to $0.04 per kilowatt hour.

The Buoyant Airborne Turbine - BAT, in comparison, is designed to operate at a height of around 1000 feet, feeding its generated power to the ground through its tethering cable. The helium-supported BAT is designed to operate in high winds (100+ mph), to tolerate heavy precipitation, and to protect its equipment from lightning surges. In severe conditions the generator can be lowered and docked.

Another airbourne wind generator project is the winged turbine wind generator under development by Makani Power that "flies in circles".

Tethered airborne wind generator designs promise the advantage of the ability to adjust the operating height of the turbine to changing wind conditions, and a perhaps a second advantage of portability, permitting emergency power generation in disaster areas. The helium-lofted BAT can be deployed in a day and requires no crew for day to day operation. - The New York Times, Cardwell (2014) & Altaeros Energies website retrieved 3/24/2014

References for Lighter-than-Air Wind Energy Systems

Other Wind Generator & Wind Energy System Concerns

Wind Energy System Payback Time: according to Proven Energy,

Payback time [to return the original installation cost of a wind energy system] varies dependent on the wind regime, grants, incentives, existing energy consumption and costs. The standard timescales are between three and ten years. If you look at this as a percentage return it works out at a minimum of 12% year on year over the life 25 year of the product.

Wind Energy Tower Shadow flicker: excessive shadow produced by the wind turbine rotor in bright sunlight - depends on latitude, sun angle, and perceived shadow dependence on wind tower setbacks from homes

Wildlife impact of wind energy systems: according to National Wind,

According to a report released by the National Academy of Sciences in May of 2007, 20,000-30,000 birds, less than one percent of a total of one billion, died as a result of colliding with wind energy facilities. One reason modern towers are solid tubes and not lattice towers, is to prevent birds from trying to nest on the turbines.

Wind turbine electrical generators & Wind Generator Controllers, also packaged solar generators

Books & Articles Wind Generators and Wind Energy System Designs

List of Wind Turbine Generator & Solar Energy Companies, San Miguel de Allende, Mexico Guanajuato

Ace Lab (52) (47) 7740055 Blvd Hidalgo 2006 Col Sn Jos Consuelo Cp 371 Len, GT


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