page_title: Environmental impact of wind power
section_title: Findings when connected to the grid
hierarchical_section_title: Environmental impact of wind power / Basic operational considerations / Pollution and effects on the grid / Findings when connected to the grid
context_page_description: The environmental impact of wind power is relatively minor when compared to that of fossil fuel power. Compared with other low-carbon power sources, wind turbines have one of the lowest global warming potentials per unit of electrical energy generated by any power source. 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 depending on whether offshore or onshore turbines are being assessed.
  Onshore wind farms can have significant impacts 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 may be implemented to limit the impact. The land between the turbines and access roads can still be used for farming and grazing.
  Habitat loss and fragmentation are the greatest impacts of wind farms on wildlife.
context_section_description: 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 (CO
  2) emissions of wind power ranged from 14 to 33 tonnes (15 to 36 short tons) per GWh (14–33 gCO
  2/kWh) of energy produced, with most of the CO
  2 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.
  However these relatively low pollution values begin to increase as greater and greater wind energy is added to the grid, or wind power 'electric grid penetration' levels are reached. Due to the effects of attempting to balance out the energy demands on the grid, from Intermittent power sources e.g. wind power (sources which have low capacity factors due to the weather), this either requires the construction of large energy storage projects, which have their own emission intensity which must be added to wind power's system-wide pollution effects, or it requires more frequent reliance on fossil fuels than the spinning reserve requirements necessary to back up more dependable sources. The latter combination is presently the more common.
  This higher dependence on back-up/Load following power plants to ensure a steady power grid output has the knock-on-effect of more frequent inefficient (in CO
  2e g/kWh) throttling up and down of these other power sources in the grid to facilitate the intermittent power source's variable output. When one includes the total effect of intermittent sources on other power sources in the grid system, that is, including these inefficient start up emissions of backup power sources to cater for wind energy, into wind energy's total system-wide life cycle, this results in a higher real-world wind energy emission intensity. Higher than the direct g/kWh value that is determined from looking at the power source in isolation and thus ignores all down-stream detrimental/inefficiency effects it has on the grid.
  This higher dependence on back-up/Load following power plants to ensure a steady power grid output forces fossil power plants to operate in less efficient states. In a 2012 paper that appeared in the Journal of Industrial Ecology, it states.
  "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 [grid] 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% [of grid] 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."
  In comparison to other low carbon power sources Wind turbines, when assessed in isolation, have a median life cycle emission value of between 11 and 12 (gCO
  2eq/kWh). The more dependable alpine Hydropower and nuclear stations have median total life cycle emission values of 24 and 12 g CO₂-eq/kWh respectively.
  While an increase in emissions due to the practical issues of load balancing is an issue, Pehnt et al. still conclude that these 20 and 80 g CO₂-eq/kWh added penalties still result in wind being roughly ten times less polluting than fossil gas and coal which emit ~400 and 900 g CO₂-eq/kWh respectively.
  As these losses occur due to the cycling of fossil power plants, they may at some poi
caption: The Vattenfall utility company study found Hydroelectric, nuclear stations and wind turbines to have far less greenhouse emissions than other sources represented.
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