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Water Reclamation Plant Recovers Energy from Engine Generators

Minnesota Energy Resources (MERC) awarded the Rochester Water Reclamation Plant (WRP) with a rebate check for adding energy-efficient equipment to collect heat. The WRP uses two 1-megawatt engine generators for supplementary power for the plant, which can be powered by either natural gas or methane collected from the anaerobic digestion process of the wastewater. In 2008/09 WRP installed a heat recovery system to collect heat from the water jacket of the engine and the exhaust system to be transferred into the plant hot water loop to heat the buildings and various processes.

Heat is needed year round in the buildings and used especially in the summer to keep the anaerobic digester at 98 degrees F. Heat provided by this system would otherwise need to be supplied by natural gas-fired boilers.

The project included replacing the existing exhaust system with a Cain exhaust heat recovery silencer and reconfiguring the process piping that tie into the plant hot water loop along with updating the controls to optimize the system performance.

Under the Minnesota Energy Custom program, the plant qualified for a rebate of $99,000.00. Chet Welle, assistant plant manager, commented about the help from Franklin Energy, “You made the process of procuring a rebate very manageable. You were concise as to what information we needed to supply. Again thank you for your assistance and direction.”

Though testing continues on the new system, at this point it is expected to save the plant 6,600 MCF annually. Under the Minnesota Energy’s Turn Key custom program, The Water Reclamation Plant qualified for a rebate of $99,000.00. Year over year, WRP will save $100,000 in energy costs.

Welle said, “This system has worked well for WRP so we decided to install a similar system on generator #1 where the exhaust heat is currently exhausted without heat recovery.”

More information on rebate opportunities through the Minnesota Energy Resources' website.

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