Constructing a Community Wind Farm
Most wind energy produced in the U.S. comes from large, independent power producers. Lately, however, small landowners, rural municipalities and utility companies have shown interest in a smaller scale approach known as community wind (CW), an emerging segment of the renewable energy development market.
By Robert Crowell
Most wind energy produced in the U.S. comes from large, independent power producers. Lately, however, small landowners, rural municipalities and utility companies have shown interest in a smaller scale approach known as community wind (CW), an emerging segment of the renewable energy development market. Focused on developing smaller, distributed wind projects with local ownership, CW resonates with the entrepreneurial spirit of communities and independent landowners across the country to develop sustainable sources of clean, renewable energy in which they are invested and maintain an ownership stake.
While there are many similarities in building large wind farms and CW farms, some important differences exist at the front and back ends of the process. Zoning and permitting issues tend to be directly proportional to the size of the project, so a CW farm is often much faster to approve. Resident landowners who are partners in the project can also help ease the zoning process and avoid the kind of not-in-my-backyard backlash that sometimes plagues absentee-owned farms. After construction, transmission and connection to the grid can also follow different courses. But essentially, ground breaking and construction follow similar lines for all wind farms.
Before breaking ground and erecting wind turbines can begin, the complex work of finding an appropriate site for a CW farm needs to be undertaken. Determining a site for a CW farm is far less labor intensive at this stage than for a big wind farm because much less land area and fewer parcels of land are needed. Still, not only will there need to be enough wind for a farm to be financially viable, it also needs to be determined that there are no factors that would rule out the prospective site. Potentially limiting factors include environmental impact—possible disturbance to wetlands, bird migration patterns, etc. Aircraft flight paths and local zoning ordinances—mainly proximity to housing—also needs to be considered. Various state, local and federal offices make the ultimate determination of these questions in the permitting stage of the process. Developers, however, can save time and money by doing much of their own homework by leveraging their own expertise and experience with other resources that, in many cases, are available online.
In selecting a site, maps showing average wind speed for the area can help identify a promising locale. The best wind farms have an average wind speed of 13 miles per hour or more. But, far more specific measurement also needs to be taken. A carefully positioned, 200-foot meteorological (MET) tower with wind gauges at various heights will record actual wind speeds and direction for a period of six months to a year. With these figures as a starting point, a specialist can estimate the long-term average wind speeds at the location and optimal height of the proposed turbine—generally between 300 and 500 feet. In general, the higher the turbine, the more power it can generate; to give some perspective, the Eiffel Tower is over 1,000 feet high.
By combining MET tower readouts with data about the specific turbine, a person can calculate the expected energy to be produced at the wind farm, taking into account certain expected losses. Downtime for annual maintenance reduces output equivalent to about one week per year, and it is estimated that one technician is required for every 10 turbines. Losses in wind speed caused by one turbine blocking the wind from another, known as tower shading, is another source of lost efficiency.
Taken all together, one arrives at the net energy expected to be produced. This will be the key to determining the value of the site. There has to be a certain amount of wind for a functional farm, but there is no one minimum figure that can be used for every location in every circumstance. Because electricity is sold locally, the potential viability of a wind farm will depend not just on the availability of wind there, but also on factors such as:
- The availability of wind in the overall region,
- Additional considerations affecting the cost of energy from the particular site, and
- The cost of energy in the overall region.
While all these levels of risk assessment, measurement, financing, and official and community approval might take years to complete, the actual construction of a CW farm can be done in a few months. The site has to be prepared with road access to haul in the wind turbines and other equipment and building materials.
Placement of multiple turbines in relation to one another will have been thought through in terms of potential noise impact, flickering shadows from the blades, tower shading and other community concerns.
Each wind turbine requires an excavation for the reinforced concrete foundation. The foundation for a wind turbine is far less specialized than the foundation of a building, which has to conform to more constraints and also be functional. Nonetheless, putting the foundation in place can be challenging if the terrain is rocky or if the soil is not structurally sound.
Once the concrete foundation is in place, the actual erection of the turbine takes only part of a day—somewhat anticlimactic after the years of preparation and study that have preceded this moment. A specialized crane has to be brought to the site, along with the mostly-prefabricated wind tower. Much like buying and installing a giant floor lamp, a wind tower does not require much assembly. The floor lamp only needs a light bulb and to be plugged in. Similarly, once the base of the turbine is positioned and the wind turbine is lifted into position, the wiring and electrical systems are installed and connected to the unit. Tests are run to ensure all functions and elements of the turbine are operating properly. These evaluations can run several weeks before all equipment has been properly tested and any identified problems have been ironed out. Only then can the wind farm achieve its full commercial capacity.
It was mentioned earlier that connection to the grid can be a different process for a CW farm than for a large wind farm. The cost advantage is on the side of the smaller project with transmission and connection to the local grid. Smaller projects can be located much closer to the cities they support. Also, the electricity produced by a CW farm of less than 80 megawatts can frequently be carried over lower voltage lines, while larger farms typically connect to the grid at more costly, higher voltages and require significant grid upgrades to reliably deliver power.
Connection to the grid is one of the major cost advantages CW farms have over large wind farms. Mega-farms usually need substantial upgrades to the transmission system to ensure reliability. Smaller wind farms, however, are able to use lower voltage lines, avoiding system overloads and costly upgrades to the systems required by the large wind farms. A series of wind farms, therefore, can use 69-kilovolt lines that are easier and less expensive to connect than a project that needs to connect to the grid at higher transmission voltages such as 230 kilovolts or 345 kilovolts. Factor in construction costs, developer fees, etc., and the end cost for a CW farm project can be lower per megawatt.
About the author: Robert Crowell is head of development at OwnEnergy, a wind development company that partners with landowners to help them develop and have an ownership stake in CW farms. He can be reached at email@example.com.