Onsite RE Generation for Vermont Wastewater Plant

The Essex Junction Wastewater Treatment facility in Essex Junction, Vermont has selected Northern Power Systems to engineer, build and install a US$245,000 on-site power system that will burn methane gas produced by wastewater processing to generate electricity and heat for the facility.

Waitsfield, Vermont – March 5, 2003 [SolarAccess.com] The new cogeneration system will produce over 400,000 kWh of electrical output per year, equivalent to 41 percent of the facility’s current annual demand. At the same time, the system will reduce the plant’s CO2 emissions by over 500,000 pounds – the equivalent of eliminating 42 cars from the road per year. As part of its commitment to removing financing obstacles to such environmentally sound systems, Northern helped the Essex Junction facility obtain grant and rebate assistance for the project from various outside sources. The Essex Junction Wastewater Treatment system (EJWTS) will employ a new controls method – the first of its kind for use in a biogas cogeneration application – developed by Northern Power Systems for the project. The controls method will enable the facility to conduct peak shaving (reducing metered demand by boosting output kW during short, higher demand times) while monitoring the power and heat requirements of the site. The system is expected to yield a total annual electric utility savings of about US$30,000. The EJWTS facility processes approximately 1.7 million gallons of wastewater per day from the suburban Burlington communities of Essex Junction, Essex and Williston. The facility also runs a biogas anaerobic digester plant, which produces 56,500 therms of methane gas per year. The plant flares 45 percent of this methane gas and burns the other 55 percent in a boiler to heat the digester tanks, accelerate decomposition of the solid waste, and kill off pathogens in the process biosolids. The new system will dramatically increase efficiencies by employing microturbines to burn 99.8 percent of the methane gas, a design that will eliminate the need to flare the previously unused portion. The electricity produced will power pumps, grinders and other process equipment. The average cost per kWh produced by the system will be US$.0246 cents (including annual maintenance expenses), yielding a US$.0637-cent savings when compared to the current utility rate. In addition to the energy savings, peak shaving will accrue US$4,500 in savings, thereby yielding a total annual electric utility savings of about US$30,000.

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