Sep. 17—TRAVERSE CITY — Solar panels and storage batteries could help Traverse City Regional Wastewater Treatment Plant shave its peak power use.
City commissioners last week approved a $257,892 contract with Jacobs, the company that operates the plant, to design and manage the rooftop solar and storage battery project. The Michigan Public Service Commission granted the city $1,685,479 toward the $2 million project.
Interim City Manager Nate Geinzer told commissioners the battery energy storage system — capable of storing 1,750 kilowatt-hours of power, documents show — is what makes the project make sense.
"As the city commission knows, we already receive 100 percent of electricity generated from renewable resources," he said, referring to power for city operations. "What makes this particular project viable is with solar and with the battery, we can potentially leverage those for peak shaving."
By using energy stored in the battery system during peak demand periods, the wastewater treatment plant can cut its energy demand and avoid paying for energy when it's most costly, Geinzer said.
Prices of electricity on the grid fluctuate throughout the day, said Tim Werner, a city commissioner and Traverse City Light & Power board member. Storing electricity in the battery system when it's cheaper then using it when prices are very high will give the utility a chance to see how solar panels, paired with battery storage, can cut peak use at a major power consumer.
Werner said as much in response to Bill Twietmeyer, a Traverse City resident and the city's former treasurer. Twietmeyer wanted to be sure city sewer ratepayers wouldn't have to completely foot the remaining cost of the project not covered by the grant. Instead, it should be split among the plant's other users according to a master sewer agreement between the city and Acme, East Bay, Elmwood, Garfield, and Peninsula townships.
Twietmeyer also wondered whether the battery energy storage system — priced at $1,067,000, according to a memo from Jacobs — would sit idle since the solar array paid for by the grant would only generate about 10 percent of what the wastewater treatment plant consumes.
Jacob Hardy, TCL&P's sustainability and key accounts manager, said these systems typically work by using the solar panels to charge the battery system, then using solar power to offset part of the plant's consumption once the batteries are charged.
Then, the plant can use power stored in the battery system during peak energy usage times when power is most expensive, Hardy said. The price of power bought on the grid fluctuates as demand and supply does.
"The wastewater treatment plant is a big user of electricity, so it's going to help them for sure ... it will definitely help them bring down their utility bill," he said.
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