Solar energy, both thermal and photovoltaic, is not the only
renewable source of electricity generation at home, the office or in
public buildings, in both rural and urban environments.
Wind
energy, previously associated with large installations using giant
generators installed in non-urban places where wind strength ensures
its economic viability, is now taken seriously to provide a regular
flow to any electrical grid.
Domestic wind turbines,
or small wind, have been designed to generate energy from wind gusts
more modest than those required by a large wind installation.
There
are dozens of different designs in the growing market for home
windmills, although most models of small wind are similar to large
generators powered by giant wind blade manufacturing companies such as
Danish Vestas or Spanish Gamesa.
Wind turbines up to 100 kilowatts
Microwind mills
are defined as those models with a wind capacity of 100 kilowatts or
less. In 2008 the total installed electric micromills in the world had
38.7 megawatts of capacity.
These wind turbines for the home
environment can be as small as a conventional 50-watt generator, like
the ones used in a small boat or caravan.
The mills use smaller
wind generators and incorporate direct drive and direct current (DC)
output, blades that adapt to the wind and a wind vane for orientation
into the wind.
There are also small wind turbines with larger
and more expensive parts that optimize power generation, output (AC)
and sensors that guide the active position of the mill to take
advantage of any gust of wind.
The microwind windmills installed in the United States alone can generate up to 17.3 megawatts of electricity. One study (access to the document)
of the American Association of Wind Energy shows the increase of 78% in
the market for small wind turbines, due to increased production
volumes, a greater number of distributors of the devices, increased
electricity prices and a greater public awareness of wind technology and its possibilities.
It
is expected, however, that growth will multiply by 30 in the United
States over the next 5 years, despite the global recession.
The
U.S. windmill industry is benefiting from the world market more than that of any other country, now controlling half the market share for these devices
in the world. U.S. manufacturers billed $77 million of a total of 156
million.
Installation and types
It is recommended to install most models of microwind turbines on towers or rooftops that are high enough, at least 9 meters (30 feet) higher than any other element in a 150 meters (500 ft) radius.
Several commercial models can be installed on any type of roof, but the
installer should take into account the stability of the location and the strength
of the wind. It is crucial to install the windmill on a solid and stable surface to avoid the generation of vibrations or sounds that could potentially disturb a home or community
owners.
While microwind mills designed for installation on roofs avoid noise or vibration, electrical generating capacity is also limited.
Despite
their lack of market share, sales are growing for smaller-scale turbines,
designed for residential use; their diameter ranges from 2 meters (7
feet) to 8 meters (25 feet) and can produce from 900 watts to 10,000
watts, if one gets wind with the speed in which they were tested.
Some
models are particularly lightweight, weighing 16 kilograms (35 pounds)
and have increased sensitivity to take advantage of breezes imperceptible
to large scale wind turbines. Assembly is equally simple, more comparable to a
television antenna than to the installation of a set of photovoltaic
panels.
The lightest models, designed for their use in urban settings, deliver a hardly perceptible noise emitted a few feet below the facility.
Their
dynamic braking, also ensures that the turbine will continue to
generate electricity when wind gusts are too strong; the device
that provides resistance to ensure the brake works can be installed
inside the building to provide heating.
The company WindTronics, based in Michigan, has developed a turbine for installation in homes and flats that can operate at speeds of 3.2 kmh (2 mph).
This mini windmill will be priced at $4,500, weighs 43 kilos, has a
diameter of 1.8 meters and can be installed on any roof or
hanging from a chimney, and it does not require the use of professional operators.
Expanding the possibilities of domestic wind: wifi microwind mills
Andy
Kruse, director of Southwest Windpower, believes technologies that
provide connection to the Internet wirelessly, such as WiMax, can boost domestic electricity generation from renewable sources.
Permanent access to web applications and real-time information would
help both consumers and installers to obtain more accurate data on the
quality and quantity of the wind or the sun in a particular location.
In
addition, wireless receivers that could start to be installed in microwind mills could turn any electrical or photovoltaic panel into a small
electric generation plant with a sensor capable of reporting on local
conditions that affect power generation at any location.
The
advent of web applications that promise to facilitate the measurement
of energy in a home environment in real time, such as Google PowerMeter,
Microsoft Hohm or Tendril, enables anyone to quickly generate energy in
their environment and measure the quantity of electricity discharged on
the network.
The so called “smart grid” could not only
facilitate the purchase and sale of energy in a deregulated free market
for big players in the sector (companies that require large amounts of
electricity, electricity suppliers and distributors), but anyone who
wants could become a potential seller of their surplus electricity
produced from their microwind mill electrical installation or their solar
photovoltaic panels.
WiMax networks could make the decentralized smart grid grow with a design more similar to that of the Internet than to a traditional centralized power distribution system, still dependent on
natural gas and coal.
The potential of small wind
The
United States is not the only country where domestic wind power is
taking off. In the United Kingdom, a study by the Energy Saving Trust
(EST) concludes that microwind mills can supply the energy needs of 800,000 homes.
This is a prediction that until recently would have been seen as too positive in comparison with more well-known reports that simply stressed that domestic mills generate so little
power that their installation is not even justified.
The EST report
estimated that installation in homes in densely populated urban environments
does not reduce the performance of these devices; however, it identifies
450,000 locations in the United Kingdom where small wind performance is optimal. The growth potential is huge, since in this country
there are only 2000 small turbines in operation.
In total, it
is estimated that microwind mills installed in home environments could
provide up to 3.1% of total energy consumption in British
households. The study is not just based on estimates; the EST based its calculations on their one year analysis of
wind turbines of 500 watts to 6 kilowatts installed in 57 urban and rural
locations in the UK.
Winds for the microwind turbines
Research carried out in the United Kingdom (the Warwick Microwind Trial project)
by the consulting firm Sustainable Encraft has studied in depth the
performance of domestic mills installed on roofs, and
therefore susceptible to widespread adoption in urban environments.
The researchers chose 26 locations in the
United Kingdom where the micro-turbines connected to the grid had been
installed in homes with the intent to compensate for their daily
consumption. Most buyers of microwind mills recognize they install them to reduce the ecological impact of their electricity consumption.
The Encraft study also highlights that many of the turbines don’t produce the electricity advertised by their manufacturers and some of them
had to be disconnected for repairs.
To Matthew
Rhodes of Encraft, “the gap between average performance (or expectation) and reality is much larger than people could reasonably expect.” Manufacturers of wind mills should strive to improve the
performance of their generators.
A new landmark for the skyline?
Nevertheless, the expectations for the sale and installation of domestic windmills are increasing rapidly.
In Paris, city authorities are planning to install small turbines on several of its highest public buildings to take advantage of the strong winds that often sweep through some of the city at a certain elevation, such as Montmartre.
Denis
Baupin, responsible for sustainable development in Paris,
has made it clear to Le Parisien that the generators will have a sober
design and installation to avoid conflicts with the aesthetic of one of the most
visited cities in the world.
“If the plan is to install 15-meter high wind turbines on the roofs, I think we are destroying Paris’ historical heritage and I fear these are utopist solutions,” says Boutros. The models chosen are small and specially designed for an urban environment.
London is a step ahead of Paris and had installed wind turbines on the outskirts. The British capital also plans to install a largescale wind turbine before hosting the 2012 Olympics.
If the manufacturers of domestic windmills are able to
control costs and improve performance of these devices, small wind seems unstoppable.
In the United States, neither home users nor manufacturers are wasting time. The firm General Electric has invested aggressively in Southwest Windpower to ensure a place in a market with promising growth potential.