City of Missoula Cogeneration System Upgrades
The City of Missoula, in its continued quest to meet the goals of their Conservation and Climate Action Plan, hired Morrison-Maierle to determine how they could turn excess methane gas into a form of energy to power the city’s Wastewater Treatment Plant (WWTP). The study found that installing a cogeneration system would generate electricity and useful thermal energy for the plant from the biogas that is produced as part of the solids stabilization process at the plant. Eager to become more efficient and provide clean energy solutions, Missoula contracted Morrison-Maierle to design and provide construction administration for the installation of a new cogeneration system at the WWTP.
This new system is gas-fired with a reciprocating engine. Additional gas filtration and dehumidification were added to the manufacturer’s stock system to ensure the biogas was dry, and corrosive compounds were removed before being burned in the engine. A natural gas blending system was also added to even out the fluctuations of the biogas production at the plant. The electrical output of the cogeneration system is connected to the larger of the two utility services at the plant. The heat output of the unit is connected through a glycol/water loop and a heat exchanger to the plant’s hot water heating loop that currently supplies the building and process heat for the plant.
With this upgrade, the cogeneration system is producing over 24 percent of the WWTP’s electricity and almost all of the plant’s heat on an average winter day. In the past, if there was no demand for this heat at the facility, the biogas was burned off. With the new upgrades in place, the cogeneration system now provides useful electrical energy for the plant year-round, and heat when required.
Services provided: Feasibility study, pre-selection of the cogeneration system, electrical and mechanical design, bidding, construction oversight, project coordination with supplier design team and subcontractor for controls design and programming.