Residential Windpower (a.k.a Small Wind)
Small scale residential wind power systems are continuing to increase in popularity. There are several reasons that account for this movement. They include:
1) Energy costs have risen causing home owners to seek relief from high energy bills.
2) Compared to solar, the technology is much simpler to understand and implement.
3) Advances in technology have increased the efficiency and affordability of implementing this type of power station.
4) Many states/utilities have adopted and implemented net metering programs that pay the home owner for the surplus power their system generates
5) Many states have very effective incentive programs to help home owners implement a small scale power generation system
Why is residential windpower needed?
For some homeowners it's mainly a financial need. Each day the world finds its reserves of fossil fuels a little more strained driving up costs. Even renewable sources such as hydro-electric are starting to fall behind. New sources need to be developed, to keep pace. The source needs to be renewable, cost effective and leverage the current power grid infrastructure. Residential windpower is such a source. This means today a homeowner can have the best of both worlds with a residential windpower system that is grid-tied. The system will drive down energy costs without requiring the homeowner to be completely reliant on it for power.
This can be a very attractive proposition, given both the tax treatment and rebate benefits of various incentive programs. Until recently (2009), there were almost no federal residential wind power incentive programs (numerous commercial incentives existed). Almost all were administered at the state level. On February 17th, 2009 the American Recovery and Reinvestment Act (ARRA) was signed into law. The act specifies federal incentives that cover residential wind turbines directly (tax incentives). See the residential energy provisions here at the U.S. Department of Energy website.
On the other hand, some homeowners select wind power because they see it as sort of a moral imperative. Responding to environmental concerns, they set implementing wind renewable energy as a priority above other merely financial matters. Still. having the financial ability to make the initial investment is, of course, paramount.
What's the best system to implement?
Today, homeowners can select from an ever burgeoning set of options for implementing a small scale wind power station in their yard or on the roof. Residential wind power systems range in configuration from the mundane to the exotic. A single system may only produce enough energy to power a few emergency bulbs. At the other end of the spectrum, larger systems can produce enough energy to meet all the energy needs of several city blocks. When considering the best type and size of system to implement, first carefully consider your objectives. (see the Residential Solar Systems Pt. 2 page. It applies equally to residential wind power systems). Then begin the design activity getting advice from experts as needed. Most equipment suppliers are only too happy to help. Properly designed and implemented, a residential wind power system can economically far outperform even alternate renewable energy options such as solar or geothermal.
Critical Factors
The most critical factors in establishing residential windpower are understanding the wind resource at the site and site zoning feasibility. How much wind is available on average? Generally, air closer to the ground moves more slowly. This is because close to the ground (below 20ft.) there are obstructions the air has to move around. Objects such as trees, houses, hedges and cars, cause sudden direction changes (turbulence) and back pressure. The net is, slower forward movement. This is why turbines are placed on top of towers (or at least rooftops) to get above the "slow chop" and into strongly unidirectional high speed air flow.
A Matter of Wind speed and Volume
A viable residential windpower site should have a considerable amount of wind. In fact, the site should be exposed to sustained wind volumes more often than not. One way to tell is to look for wind pressure "footprints". For instance, look for the amount of vegetation "flagging" at the site. This is where trees, tall bushes and the like have grown with their branches and leaves pushed to one side, pointing in the direction of a constant wind. In extreme cases, where the air movement has been very consistent, the vegetation will lean with its foliage extended in one direction as if the wind is currently vigorously blowing, even on a calm day. Such sites are ideal for residential wind power.
The reason speed and volume are so important is because the energy in wind is proportional to the cube of its speed. This geometric relationship between wind velocity and energy content is constant and expressed by the following formula:
Energy available in wind (in Watts for a given swept area) =
½ x air density x swept area x wind velocity**3
Stated simply, every time wind speed doubles, the amount of energy it carries increases by a factor of EIGHT. This means that, all other things being equal, a wind turbine in 20 mph of wind will generate approximately EIGHT times the energy of the same turbine in a 10 mph wind. In fact, the wind can generate dangerous amounts of energy for a wind turbine, as we'll see later. Most manufacturers design their turbines to operate optimally between 10 - 33mph, with shutdown satiety protocols automatically activating when wind speeds reach much above that range. Turbines are designed to operate in the 10 - 35mph range because that's where most wind activity occurs. Significantly faster (+40mph) winds are relatively rare. It's worth noting that this relationship allows parallels to be drawn between wind energy and solar energy. For instance, wind is similar to sunlight in that there is a constant amount of energy per sq. meter, at a steady velocity. To harvest that energy, all that is needed is the proper, hopefully highly efficient "collector". All other things being equal, the larger the collector surface area (for turbines, its swept area), the more energy is harvested. Obviously, swept area is therfore very important for wind turbines (see the page on Residential Wind Turbines, for more information).
Sustained speeds (volume) equal reliable power. Therefore, ideal locations for residential windpower are coastal city areas with steady sea breezes, relatively higher altitude locations (hills tops, possibly mountain tops) or wide flat open tracts such as valley floors where winds are channeled by topography.
Site Regulation
The second critical factor to consider is site regulation. It's important to understand the nature of zoning for the area. This cannot be over-emphasized. For instance, it might be municipally acceptable to erect a 40ft tower on an eight acre lot 2 miles from the nearest road. However, that same tower might be cited because of building/zoning code violations if erected in the middle of a single family housing development. There may be more than ample wind resource at 40ft., but if the city says the sites' lot can't have a tower that high, it doesn't matter. This is a common problem with suburban residential windpower sites.
Generally speaking, rural sites have fewer restrictions. In fact, acquiring the needed permits and approvals for a home wind power system can be fairly problematic. For instance, some cities won't allow any structure higher than the "tree line" even for semi-rural locations. Or possibly the covenants, conditions and restrictions for a development simply don't allow wind turbine installations in any form. In addition, depending on the locale, there may be noise pollution issues, avian flight path issues and/or environmental code issues. Admittedly, for large scale windpower production these are very real concerns and very much less so for small scale home systems. Just the same, the permitting process for a site can be arduous, expensive and annoying. Be prepared. This is one area where the help of an experienced wind power contractor for your locale can be of immense value (it could even save your sanity).
The Bottom Line
As a renewable energy resource residential windpower is inexhaustible and can be very usable for the everyday homeowner. It's important to keep in mind though, its effectiveness depends greatly on the energy extraction method employed and the amount of wind resource available at the site.
A Word of Caution:
The residential windpower industry is fairly young. This is especially true in the area of small scale wind power markets. There are no standards for product comparison, no licensing bodies to designate quality workmanship standards, no real watchdog groups. The situation is an attractive opportunity for the unscrupulous to prey upon and take advantage of the unwary. On the other hand, there are situations where some manufacturer's products are simply superior to others, for a specific application. Where the strongest quality materials are used for the demanding environments of industrial/commercial applications, some manufacturers use less robust materials for residential markets, to trim costs. Will the bearings hold up? Are the rotor blades strong enough? Does the equipment come with warranties? Which manufacturers stand behind their products? Separating the wheat from the chaff can be problematic at best (are you buying a "Honda" turbine or a "Yugo"?). How then to steer clear of situations involving poor quality equipment? We suggest your best defense is knowledge. On our Special Home Sources page, we continuously gather reference materials that contain help in selecting the best equipment for the job.Visit when you get a chance or contact us if you have additional information to contribute.
