Three years ago, Dennis Quinn, president of what was then Seattle-based Celerity Energy, proposed to San Diego Gas & Electric Co. (SDG&E) that it develop a “Clean Gen” program designed to upgrade 25 MW of existing backup generators to support the grid during times of peak demand. Recognizing the value of the Clean Gen program, in terms of both an operating cost perspective and its ability to positively affect SDG&E’s environmental impact, the utility accepted Celerity’s proposal.
In May 2006, Celerity was acquired by Boston-based EnerNOC Inc., a demand response aggregator that has more than 900 MW of demand response capacity under management.
Nonsmoking engines
The Clean Gen program aggregates existing backup generators and operates them during periods of peak demand to support the electric grid and minimize blackout risk. Shortly after partnering with SDG&E, Quinn and the EnerNOC team signed contracts with several end users to enroll their backup generators in the program. However, before it could move forward, emissions had to be addressed with San Diego County’s Air Pollution Control District (APCD).
The APCD had concerns about 25 MW worth of backup generators operating more hours than their then-current permits would allow because of the potential negative impact on San Diego’s air quality. The APCD and EnerNOC worked to identify filters that would allow the generators to emit the same amount of particulate matter or less in 200 hours as they would have emitted in the normally permitted 30 hours of operation per year.
Quinn and EnerNOC agreed to install California Air Resources Board–approved diesel particulate filters (DPFs) that would reduce particulate matter emissions by over 85% (Figure 1). Another important benefit of the DPFs is that they significantly reduce carbon monoxide and hydrocarbon emissions. In addition, recent California regulations require the exclusive use of ultra-low-sulfur diesel fuel.
1. Nonsmokers only please. EnerNOC installs a California Air Resources Board–approved filter on each generator to reduce emissions. Both generators are running in this picture. The generator on the left shows post-installation air quality; the generator on the right shows pre-installation air quality. Courtesy: EnerNOC
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