As currently deployed, wind power is a supplementary power source whose role is to reduce fossil fuel use by displacing thermal generation. The Irish situation is typical in the sense that it has rapidly growing wind penetration embedded in diverse portfolio of thermal plant. A detailed empirical model of operational CO2 savings was developed for 2011. It is found that savings of 0.28tCO2/MWh were achieved, versus a zero-wind emissions intensity of 0.53tCO2/MWh. This estimate is at the lower end of expectations. In particular, it is significantly lower than the emissions intensity of the CCGT plant which play the primary role in balancing wind generation. Effectiveness is likely to fall further as wind penetration increases.[10, 11]
Assessments of the economic or environmental benefit of wind power are not credible unless they are based on accurate emissions (and fuel) savings. This study suggests that savings may be lower than contemplated by public agencies to date. The Irish government has an ambitious target of meeting 37% of domestic electricity demand using wind power by 2020. It is a concern that at 17% wind penetration, the system is already in a regime where effectiveness is approaching 50%, even before significant curtailment and/or exports of wind power begin to occur.
Finally, life-cycle estimates of CO2 emissions involved in construction and installation of wind power are sensitive to assumptions about the capacity factor, economic life of wind turbines, infrastructure requirement etc. Estimates are in the range 0.002-0.08 tCO2/MWh. At the upper end of this range, life-cycle emissions are a significant fraction of operational CO2 savings.