|Analysis of Indirect Emissions Benefits of Wind, Landfill Gas, and Municipal Solid Waste Generation
A number of techniques are introduced to calculate the hourly indirect emissions benefits of three types of renewable resources: wind energy, Municipal Solid Waste (MSW) combustion, and Landfill Gas (LFG) combustion. These techniques are applied to each of the EPA's eGRID subregions in the continental United States in order to derive hourly, seasonal, or annual (as appropriate) coefficients for use in evaluating the indirect emissions benefits of such projects in each region.
For wind power impacts, simulated wind project power profiles are derived using publicly available wind data scaled to a typical turbine height for new wind projects and transformed through a power curve for a proxy turbine. The results for one region are compared to the output of an existing project, although the limitations of this type of comparison, as well as the limitations of representing large areas of the country with single proxy curves, are discussed. LFG and MSW are found to have flat, "always on" profiles based on the limited data available.
The regional, hourly power profiles for each type of resource are combined with the hourly indirect emissions coefficients to yield annual indirect emissions benefits for each type of resource for each eGRID subregion.
For each GWh of renewable energy produced each year, the indirect CO2 emissions benefit is found to be between 600 and 1100 tons of CO2 depending on the region, with coal-dependent regions having the highest indirect emissions benefit. The indirect NOx and SO2 emissions benefit also depends on the regional fuel mix, as well as the stringency of environmental regulation in each region. These indirect emissions benefits vary between 500 and 5,000 pounds of NOx per GWh, and between 200 and 1,300 pounds of SO2 per GWh. With some exceptions, these results are robust regardless of whether the renewable resource has a base load profile (such as MSW and LFG) of output which varies diurnally and seasonally (such as wind). However, as the calculated benefits do vary in some cases depending on the analytical approach, care must be used in selecting an appropriate calculation methodology for each application.
This report was submitted in fulfillment of Order Number EP07C000079 under the sponsorship of the EPA.
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