A typical modern wind turbine has a capacity of two megawatts (MW) and is expected to avoid emissions of over 2,200 tonnes of CO2 in an average year.
Calculations
The simplest formula to estimate the amount of energy generated by any electricity generating station is:
(Power x Time) x capacity factor = Energy (electricity) generated
The units of energy normally used are megawatt hours (MWh) and kilowatt hours (kWh) but sometimes Joules (J), Kilojoules (kJ) or Megajoules (MJ).
A wind turbine’s output varies with the wind speed and an average modern wind turbine has a capacity factor of around 30%. This figure should not be confused with the amount of time a wind turbine is generating energy which is much higher.
Worked example for a 2MW (2000kW) wind turbine over a year
Energy = (2000 x 8760) x 0.3 = 5,256,000 kWh
The electricity generated by a wind turbine reduces the need to generate electricity from other sources. In the UK these other sources will almost certainly be fossil-fuelled (i.e. coal, oil or gas).
Carbon Dioxide Emissions Reductions: Scenario 1 – conservative estimate
Electricity generated by the mix of all UK generating stations results in average emissions of 422 gCO2/kWh of electricity generated (Part L2A: Conservation of fuel and Power (New buildings other than dwellings) building regulations 2006 -Table 2 page 15). This includes ‘base-load’ sources which will not reduce their output when demand varies and/or other sources are generating.
5,256,000 kWh of clean energy displacing electricity generated from this generation mix will result in the displacement of 2,218 tonnes of CO2 ((5,256,000 x 422)/1,000,000).
Carbon Dioxide Emissions Reductions: Scenario 2 – likely situation
Electricity generated only by those stations which are ‘flexible’ and will reduce their output when demand varies and/or other sources are generating. These are almost entirely fossil fuel installations and this mix ‘fossil-mix’ results in average emissions of 568 gCO2/kWh of electricity generated (Part L2A: Conservation of fuel and Power (New buildings other than dwellings) building regulations 2006 -Table 2 page 15).
5,256,000 kWh of clean energy displacing electricity generated from this generation mix will result in the displacement of 2,985 tonnes of CO2 ((5,256,000 x 568)/1,000,000).
Carbon Dioxide Emissions Reductions: Scenario 3 – coal stations
Electricity generated only by existing coal-fired stations. These can have emissions of 860 gCO2/kWh of electricity generated.
5,256,000 kWh of clean energy displacing electricity generated from this generation mix will result in the displacement of 4520 tonnes of CO2 ((5,256,000 x 860)/1,000,000).