Environmental impact of wind power

The environmental impact of wind power when compared to that of fossil fuel power, is relatively minor. Compared with other low carbon power sources, wind turbines have some of the lowest global warming potential per unit of electrical energy generated. According to the IPCC, in assessments of the life-cycle global warming potential of energy sources, wind turbines have a median value of between 15 and 11 (gCO2eq/kWh) depending on whether off- or onshore turbines are being assessed.The thermal efficiency of fossil-based power plants is reduced when operated at fluctuating and suboptimal loads to supplement wind power, which may degrade, to a certain extent, the GHG(Greenhouse gas) benefits resulting from the addition of wind to the grid. A study conducted by Pehnt and colleagues (2008) reports that a moderate level of wind penetration (12%) would result in efficiency penalties of 3% to 8%, depending on the type of conventional power plant considered. Gross and colleagues (2006) report similar results, with efficiency penalties ranging from nearly 0% to 7% for up to 20% wind penetration. Pehnt and colleagues (2008) conclude that the results of adding offshore wind power in Germany on the background power systems maintaining a level supply to the grid and providing enough reserve capacity amount to adding between 20 and 80 g CO2-eq/kWh to the life cycle GHG emissions profile of wind power. The environmental impact of wind power when compared to that of fossil fuel power, is relatively minor. Compared with other low carbon power sources, wind turbines have some of the lowest global warming potential per unit of electrical energy generated. According to the IPCC, in assessments of the life-cycle global warming potential of energy sources, wind turbines have a median value of between 15 and 11 (gCO2eq/kWh) depending on whether off- or onshore turbines are being assessed. Onshore wind farms can have a significant impact on the landscape, as typically they need to be spread over more land than other power stations and need to be built in wild and rural areas, which can lead to 'industrialization of the countryside' and habitat loss. Conflicts arise especially in scenic and culturally-important landscapes. Siting restrictions (such as setbacks) may be implemented to limit the impact. Land between the turbines and access roads can still be used for farming and grazing. Habitat loss and fragmentation are the greatest impact of wind farms on wildlife. Wind turbines, like many other human activities and buildings, also increase bat and bird deaths. A summary of the existing field studies compiled in 2010 from the National Wind Coordinating Collaborative identified fewer than 14 and typically less than 4 bird deaths per installed megawatt per year, but a wider variation in the number of bat deaths. Like other investigations, it concluded that some species (e.g. migrating bats and songbirds) are known to be harmed more than others and that factors such as turbine siting can be important. However, many details as well as the overall impact from the growing number of turbines remain unclear. The National Renewable Energy Laboratory maintains a database of the scientific literature on the subject. Wind turbines generate some noise. At a residential distance of 300 metres (980 ft) this may be around 45 dB. At 1.5 km (1 mi) distance most wind turbines become inaudible. Loud or persistent noise increases stress, and stress causes diseases. Wind turbines do not affect human health from noise when properly placed. However, when improperly sited, data from the monitoring of two groups of growing geese revealed substantially lower body weights and higher concentrations of a stress hormone in the blood of the first group of geese who were situated 50 meters away compared to a second group which was at a distance of 500 meters from the turbine. The energy return on investment (EROI) for wind energy is equal to the cumulative electricity generated divided by the cumulative primary energy required to build and maintain a turbine. According to a meta study, in which all existing studies from 1977 to 2007 were reviewed, the EROI for wind ranges from 5 to 35, with the most common turbines in the range of 2 MW nameplate capacity-rotor diameters of 66 meters, on average the EROI is 16. EROI is strongly proportional to turbine size, and larger late-generation turbines average at the high end of this range, are by one study, approximately 35. Wind turbine manufacturer Vestas claims that initial energy 'pay back' is within about 7–9 months of operation for a 1.65-2.0MW wind turbine under low wind conditions, whereas Siemens Wind Power calculates 5–10 months depending on circumstances. Wind power consumes no water for continuing operation, and has near negligible emissions directly related to its electricity production. Wind turbines when isolated from the electric grid produce negligible amounts of carbon dioxide, carbon monoxide, sulfur dioxide, nitrogen dioxide, mercury and radioactive waste when in operation, unlike fossil fuel sources and nuclear energy station fuel production, respectively. With the construction phase largely to blame, wind turbines emit slightly more particulate matter (PM), a form of air pollution, at an 'exception' rate higher per unit of energy generated(kWh) than a fossil gas electricity station('NGCC'), and also emit more heavy metals and PM than nuclear stations, per unit of energy generated. As far as total pollution costs in economic terms, in a comprehensive 2006 European study, alpine Hydropower was found to exhibit the lowest external pollution, or externality, costs of all electricity generating systems, below 0.05 c€/kWh. Wind power externality costs were found to be 0.09 - 0.12c€/kW, while nuclear energy had a 0.19 c€/kWh value and fossil fuels generated 1.6 - 5.8 c€/kWh of downstream costs. With the exception of the latter fossil fuels, these are negligible costs in comparison to the cost of electricity production, which is approximately 10 c€/kWh in European countries. A typical study of a wind farm's Life cycle assessment, when not connected to the electric grid, usually results in similar findings as the following 2006 analysis of 3 installations in the US Midwest, where the carbon dioxide (CO2) emissions of wind power ranged from 14 to 33 tonnes (15 to 36 short tons) per GWh (14–33 gCO2/kWh) of energy produced, with most of the CO2 emission intensity coming from producing the concrete for wind-turbine foundations. By combining similar data from numerous individual studies in a meta-analysis, the median global warming potential for wind power was found to be 11–12 g CO2/kWh and unlikely to change significantly.