the vattenfall utility company study found hydroelectric, nuclear stations , wind turbines have far less greenhouse emissions other sources represented.
a typical study of wind farms life cycle assessment, when not connected electric grid, results in similar findings following 2006 analysis of 3 installations in midwest, carbon dioxide (co2) emissions of wind power ranged 14 33 tonnes (15 36 short tons) per gwh (14–33 gco2/kwh) of energy produced, of co2 emission intensity coming producing concrete wind-turbine foundations. combining similar data numerous individual studies in meta-analysis, median global warming potential wind power found 11–12 g co2/kwh , unlikely change significantly.
however these relatively low pollution values begin increase greater , greater wind energy added grid, or wind power electric grid penetration levels reached. due effects of attempting balance out energy demands on grid, intermittent power sources e.g. wind power(sources have low capacity factors due weather), either requires construction of large energy storage projects, have own emission intensity must added wind power s system-wide pollution effects, or requires more frequent reliance on fossil fuels spinning reserve requirements necessary more dependable sources. latter combination presently being more common.
this higher dependence on back-up/load following power plants ensure steady power grid output has knock-on-effect of more frequent inefficient (in co2e g/kwh) throttling , down of these other power sources in grid facilitate intermittent power source s variable output. when 1 includes total effect of intermittent sources on other power sources in grid system, is, including these inefficient start emissions of backup power sources cater wind energy, wind energy s total system wide life cycle, results in higher real-world wind energy emission intensity. higher direct g/kwh value determined looking @ power source in isolation , ignores down-stream detrimental/inefficiency effects has on grid. higher dependence on back-up/load following power plants ensure steady power grid output forces fossil power plants operate in less efficient states. in 2012 paper appeared in journal of industrial ecology states.
thermal efficiency of fossil-based power plants reduced when operated @ fluctuating , suboptimal loads supplement wind power, may degrade, extent, ghg(greenhouse gas) benefits resulting addition of wind grid. study conducted pehnt , colleagues (2008) reports moderate level of [grid] wind penetration (12%) result in efficiency penalties of 3% 8%, depending on type of conventional power plant considered. gross , colleagues (2006) report similar results, efficiency penalties ranging 0% 7% 20% [of grid] wind penetration. pehnt , colleagues (2008) conclude results of adding offshore wind power in germany on background power systems maintaining level supply grid , providing enough reserve capacity amount adding between 20 , 80 g co2-eq/kwh life cycle ghg emissions profile of wind power.
in comparison other low carbon power sources wind turbines, when assessed in isolation, have median life cycle emission value of between 11 , 12 (gco2eq/kwh). more dependable alpine hydropower , nuclear stations have median total life cycle emission values of 24 , 12 g co2-eq/kwh respectively.
while increase in emissions due practical issues of load balancing issue, pehnt et al. still conclude these 20 , 80 g co2-eq/kwh added penalties still result in wind being ten times less polluting fossil gas , coal emit ~400 , 900 g co2-eq/kwh respectively.
as these losses occur due cycling of fossil power plants, may @ point become smaller when more 20–30% of wind energy added power grid, fossil power plants replaced, has yet occur in practice.
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