Wind Energy: Impacts for the Future
Wind energy transforms energy in the wind for generating electrical or mechanical energy by conversion of kinetic energy. The wind turns the blades, converting wind into a rotational shaft which is connected to a generator making electricity available. Typically turbines are either composed of two blades or three blades. The first is called a downwind turbine and the latter an upwind turbine. The amount of energy generated is dependent upon the size, number of turbines and the speed of the wind through the rotors. Generally, wind turbines today have power ratings ranging from 250 watts to 1.8 megawatts (MV). An average household requires approximately 10,000 kWh of electricity annually. For comparison, a 10-kW wind turbine generates approximately 16,000 kWh annually, more than enough to power a typical household. An elementary school in Iowa uses a 250-kW turbine providing approximately 350,000 kWh of electricity annually. Many turbines placed together form wind farms (figure 1) which is an economical approach for supplying large quantities of electricity. Wind speed and resource is also an essential factor in the equation. Power generated from the wind speed is 3 times the speed. Thus, a small difference in wind speed can equate to huge differences in power. While conventional utility power plants run on fuel and operate continuously unless manually idled, wind farms are dependent upon wind, which at times blows steadily and other times not at all. It is therefore important to note that a wind turbine is typically not a sole source of power but is often used in conjunction with conventional methods as backup. Energy supply estimates range from 20% of the nation’s electricity (AWEA, 2000) to 1.5 times the current consumption (Elliot et al, 1993). The estimates are exceedingly varied and thus it is difficult to determine the validity of any statistics without further research. That being said, each statistic does indicate that wind power has the potential to become a huge source of renewable energy for the world and is the fastest growing.
Wind energy has been harnessed throughout history and was one of the earliest known resources. Windmills began to appear in Islamic civilization during the 7th century and spread into Western Europe by the 11th. By 1850, America began using windmills to pump water. After WWII, the Rural Electrification Act was passed, closing down the major wind generators by 1959 as resources were directed toward urban power companies. Since then, our society has increased it’s dependence on fossil fuels, thus allowing fossil fuels to become our primary energy source. Unlike wind, fossil fuel is not a renewable form of energy. Consequently, our society now struggles to find renewable sources of energy to compensate for decreasing resource availability, increasing damage to the environment and increasing prices. This realization has spawned what is known as the “energy crisis” beginning in the mid 1970’s. The energy crisis sparked a renewed interest in wind energy and other forms of green power. Thus began modern wind energy efforts in 1981 with first turbines installed in Denmark and California. This industry was driven initially by tax credits. Environmentalists, conservationists and the general public supported the re-development of wind energy as it was environmentally friendly and a long term cost saving method of energy. Wind power seemed like the perfect alternative until deaths of birds and bats among other environmental impacts were discovered.
In the mid 1980’s, turbine related avian deaths in Altamont, California forced environmentalists to take a closer look at the impacts of wind turbines when roosting birds made their home in the lattice towers. Later, the first dead bats were found on Backbone Mountain in West Virginia. These early warning signs were mostly ignored since fatalities were initially low and thought to be fluke events. These early warning signs brought about both a mixture of surprise and disbelief from the environmental community. What was thought to be a perfect solution, was producing results that no one wanted to deal with because they thought it would go away. As additional data and subsequent concerns surfaced, scientists began attempting to understand the relationship between birds/bats and turbines.
The most obvious impact on birds results from direct collision. Not unlike collision mortality found with other man-made structures such as buildings, windows, power lines and communication towers, birds have been found injured or killed upon collision with the turbine blades and towers. Additionally, vehicles accessing the sites as well as wires play an indirect role in collision mortality rates. While collision mortality is a direct impact to birds, there are several indirect impacts such as habitat loss and fragmentation, disturbance and displacement. Avoidance of turbine sites and the surrounding habitat are of concern as well as the overall turbine footprint including site roads and buildings. In fact, findings out of Europe wind farms indicate that displacement has a greater impact than collision mortality (AWEA,2004). Another environmental dynamic resulting in bird fatalities could be caused by increased bird attractants such as burrowing mammals, which are prey species for golden eagles and other raptors. Construction around turbine sites has led to an increased presence of ground mammals such as gophers, squirrels and rabbits. Mortality rates subsequently increase as birds are attracted to turbine sites. It is important to note that in this case it is not just the turbine structure alone producing fatalities but the surrounding ecosystem.
Initial studies tended to focus primarily on avian impacts until wind farms migrated east and bat mortality rates were exceeding those of birds. The highest rates of bat mortality have been found along the East Coast with the highest in West Virginia. Like avian impacts, mortality upon collision is the most common and well known. However, unlike avian impacts little data exist on bat impacts primarily because it is a much more recent phenomenon. Additionally, bird fatality as a result of man-made structures such as communication towers have been well documented. Lessons learned from the communications industry have resulted in the wind industry adjusting turbine technology to mitigate avian impact risks. It is known that migratory bats comprise approximately 90% of all bat fatalities (AWEA et al, 2004), indicating that turbine sites are placed in migratory corridors. Of the unknown, several hypotheses exist although have not been studied. The migratory behavior of bats is unknown in addition to any sensory cues bats use at night. One theory is that the turbine structure actually attracts bats whether it is misperceived as roosting trees or insect entrapment, since bats feed on the insects attracted to the night time light on the turbine structure. Another hypothesis states that rotating blades emit low frequency sounds picked up by the bats. Despite a variety of unanswered bat questions, sufficient data exist to indicate the relationship of birds and turbines that can be used to hypothesize similar results for bats. Cumulative impacts are less understood. The ability for a variety of species to withstand current rates of mortality at both national and regional scales has yet to be addressed.
Given that wind power is the fastest growing renewable energy alternative, concerns have subsequently surfaced about threats to bird and bat species. Collision mortality is only one of many threats that already exist outside the wind industry. Pesticides, global warming, development and other human-induced threats already test population stability. Will an exponentially growing industry such as wind energy drive populations over the edge? We already know that populations of species are sensitive to habitat fragmentation and other disturbances. It is highly unlikely that turbine structures will be an exception. Even with the uncertainties surrounding bat impacts, we do know that bat populations are declining. Two Federally endangered species like Indiana and Virginia big-eared are in serious trouble (AWEA et al, 2004). Modeling is the primary tool used for predicting cumulative impacts resulting from turbine structures and/or sites. Unfortunately results from modeling exercises are only partly useful since so much is still unknown. Because an ecosystem approach is essential in capturing cumulative impacts, including additional threats beyond collision are pertinent but difficult to quantify.
Research studies attempting to answer several unknowns described above are underway. Most studies follow the same procedures beginning with pre-development risk assessment. It is at this initial stage, candidate sites for turbine development are determined as a wind resource. This stage can take up to a year to assess the wind resource accurately as well as bird and bat migratory patterns. It is also during this risk assessment phase that land use, habitat, species identification and those of surrounding areas are assessed. Biologists, environmental groups, bird enthusiasts and other government and non-government agencies are consulted. Information specifically about bird and bat relationships to the site are determined, especially those species listed under the ESA. This is a critical step in the project as potential risks can be mitigated or avoided with site selection.
Monitoring impacts on birds and bats begins upon project start up. This is also perhaps the most difficult stage. Identifying causalities are especially difficult since most collisions are rarely observed. Counting carcasses is the primary method for collecting data but it is difficult as inferences must be drawn. Sites searched are based upon turbine size and are often down-wind where most carcasses tend to be found. It is thought that fatality could be artificially high since a cluster of feathers is often considered a decomposed carcass and a fatality resulting from the turbine. Conclusions resulting from monitoring studies tend to be adjusted for biases such as searcher efficiency. It is at this point in the project that industry misconceptions create setbacks for both environmentalists and energy companies. Monitoring studies require that scientists access turbine sites and surrounding fatalities to collect scientific, publishable data concerning species fatalities and other environmental impacts. Sufficient data collection can take years to establish a repeatable pattern. Often companies, especially smaller companies, do not have three years and will often times appoint their own Technical Advisory Committee (TAC) often leading to energy biased results. Insufficient funding and unidentifiable research grants prevent scientists from even collecting the data. Much of this setback is due to industry misconceptions driven by an energy industry fearful of negative publicity, backed by the idea that environmental scientists are set on finding harmful data that would slow down wind energy growth. However, my research indicates differently. Environmentalists would like to aid in the development of wind farms while minimizing the various environmental impacts. The only means to a solution is to research the causes, but without sufficient access and funding that is impossible. After all wind energy is an environmentally friendly technology. Environmentalists just want to ensure it remains so.
While findings tend to be skewed due to various uncertainties and biases, strategies have been outlined to mitigate potential bird and bat impacts. The U.S. Fish and Wildlife Service has documented several voluntary guidelines including but not limited to the following:
�Bury cable and use bird diverters
�Use minimal lighting in operation and maintenance buildings
�Alter operation schedules during peak migratory seasons
�Build fewer and larger turbines
�Access roads should be kept narrow and re-growth along roadsides encouraged
�Projects need to be situated on already disturbed habitat whenever possible
�Guys wires avoided
�Avoid sites with documented species listed under the Endangered Species Act.
�Orient turbines parallel to known bird movements
�Tubular supports should be pointed rather than lattice in design
�Adjust tower height according to local wildlife populations
Interestingly, these guidelines are voluntary and companies are not necessarily held to strict regulation. Despite the lack of enforcement, the guidelines do act as mitigation strategies for those impacts that are well understood. The list will likely increase as various questions are answered and wind technology increase.
One such recent development involved offshore wind farms, which began in Europe in the mid 1980’s and has been in operation since the early 1990’s (AWEA, 2004). With the U.S. currently starting to think about offshore wind farms there is much to be learned from the European experience. Prior to construction, a pre-construction Environmental impact Assessment is completed involving collection of baseline data and evaluation of environmental effects lasting approximately one year and half. Subsequent monitoring for three years is performed producing annual reports to the government. Monitoring and risk assessment focus primarily on disturbance and collision for birds, impact on mammals especially seals and porpoises, impacts to fish, bottom dwelling flora and fauna and lastly noise vibrations. Europe has found disturbance effects on local populations but have not been able to link them conclusively to turbine construction. Interestingly, no collisions have been found (AWEA, 2004) but carcasses are difficult to obtain given the offshore nature of the wind farm. The United States is using the European offshore wind farm experience as it sets out researching sites nationally. In addition to the same factors considered in onshore wind farms, offshore wind farms must collect sufficient data on noise/vibration, radar/radio communications and air traffic. Regulation is especially tricky because there are several jurisdictions for ocean activities. Currently, two projects in the U.S. are underway, one in Nantucket Sound and the other in Long Island Sound.
Despite the existing controversy surrounding wind energy the future is bright. The “green” image has been tarnished and there are red tape obstacles to overcome before comprehensive research will be available. As more and more data surfaces surrounding bird and bat impact, the focus will move toward ecological integrity and habitat impacts producing comprehensive results answering questions on larger scales. As turbine technology increases, harmful impacts to the environment will decrease. Already 2,000 tons of carbon dioxide greenhouse gases are avoided and 10 tons of sulfur dioxide and 6 tons of nitrogen dioxide with each 1.0 MW of energy produced. Current rates alone could prevent burning of 8.4 million tons of coal. It does appear to be an optimistic industry and one that will be a win-win for renewable energy and the environment.
