Siemens, in partnership with Fougner Engineered Sales, a supplier of electric equipment and supplies, has been selected by Otter Tail Power Co. to provide two variable frequency drives (VFD) for environmental upgrades at the Big Stone Plant, a coal-fired power plant that the company operates in Big Stone City, S.D.

In May, plant owners Otter Tail Power, Montana-Dakota Utilities Co., and NorthWestern Energy approved a plan calling for $490 million in environmental retrofits, including a new air-quality control system to be commissioned within five years of the Environmental Protection Agency’s approval of the South Dakota Regional Haze State Implementation Plan.

Two Siemens Robicon Perfect Harmony WCIII drives will support a new dry scrubber to reduce sulfur dioxide. Plans also call for a selective catalytic reduction (SCR) unit to reduce emissions of nitrogen oxide. According to an Otter Tail Power Co. spokesperson, these retrofits are expected to reduce both nitrogen oxide and sulfur dioxide by 80 to 90 percent.