The Minnesota Pollution Control Agency is taking comment until Aug. 4 on a draft air permit sought by Rochester Public Utilities so it can construct and operate a new power station, called the Westside Energy Station (WES), adjacent to its Westside substation in Cascade Township, Olmsted County, Minnesota.
The facility will be made up of five Wärtsilä 20V34SG non-emergency natural gas-fired engines with a total generating capacity of 48 MW, and it will operate as a peaker.
The Wärtsilä engines will fire on natural gas only. The engines have ported gas admission and a prechamber with a spark plug for ignition. With lean combustion (high air to fuel ratio) the peak temperature is reduced and less NOx is produced. The engines come equipped with an Engine Control System that monitors the engine load, speed, and cylinder exhaust temperature and controls the air-fuel ratio and ignition timing in each cylinder individually. The engines will also have startup air, lubricating oil, compressed air, and cooling systems. The exhaust temperature will be approximately 700⁰F and will exhaust though the control equipment and an exhaust silencer before entering the atmosphere via the stack.
The control equipment for each engine will be selective catalytic reduction with urea injection for control of NOx emissions, and an oxidation catalyst for control of CO, VOCs, and HAPs. Maximum output is about 9.6 MW for each engine, for a total of 48 MW for the facility.
The project also includes installation of a diesel-fired emergency/black start engine and a diesel-fired fire pump. The fire pump may or may not be installed. The emergency engine will be used to provide power for startup of one non-emergency engine during times when there is no power available from the grid. Installation of one or more natural gas-fired heaters with a total capacity up to 9 MMBtu/hr would also authorized by this permit action.
A project contact is: Craig Diekvoss, Rochester Public Utilities, 4000 East River Road NE, Rochester, MN 55906.