In preparing its long-term integrated resource plan (IRP), Seattle City Light has outlined three alternatives that could mean increased integration of wind energy.
According to the utility's draft environmental impact statement (EIS), part of its 2012 IRP, it is forecasting electricity load in its service territory to grow at an average annual rate of 0.8% during the 2012-2031 period considered under its 2012 IRP. Annual system energy load reached a high of 1,154 average MW in 2008, falling recently due to the economic recession but rebounding to 1,134 MW in 2011.
The municipal utility evaluated three combinations of resources that could meet its growing electricity needs during the 20-year planning period, noting it has not yet identified a preferred alternative. One involves renewable energy and ‘base’ conservation, another involves wind and natural gas-fired generation, and the third involves renewable energy and increased conservation.
While all alternatives rely on conservation to add 237 MW to the resource portfolio, the base conservation renewable alternative consists of cumulatively adding 125 MW of wind energy, 20 MW of solar photovoltaic energy, 40 MW of biomass energy, 20 MW of geothermal energy, 8 MW of landfill gas energy, and 5 MW of hydro efficiency from a proposed second power tunnel at the Gorge Dam.
Looking at the wind and gas alternative, the new resources include 125 MW of wind energy and 93 MW of combined-cycle gas generation. ‘The wind and gas portfolio is a straightforward portfolio with base case conservation and contracts for wind and the output of a natural-gas combined-cycle turbine. Wind enters the portfolio in 2022, while the first natural-gas generation enters in 2024,’ according to the draft EIS. ‘By the end of the planning period, there is about 34 percent more wind generation than natural gas generation.’
The utility says the draft IRP will be completed this summer and expects to submit the final plan the Washington Department of Commerce in September.