The Southeast Alaska Power Agency Board approved $97,750 to replace the backup battery bank at the Tyee Lake hydro facility at a regular board meeting last Thursday.
Early last month, Petersburg and Wrangell were providing their own power for about a week while the Tyee Lake Hydro facility was offline for annual maintenance. During the maintenance period, SEAPA conducted a battery capacity discharge test of the hydro project's nickel-cadmium batteries. Three hours into the test, one of the batteries began to decay. Another battery also began decaying after eight hours of testing. The batteries are meant to operate the plant for 10 hours in the event of a generation outage without any issue, according to Project Manager Robert Siedman.
"We got nearly 15 years out of them, which is good for batteries," said Siedman. "It's not unreasonable to expect them to be in the condition that they are, but now is the time to do a replacement."
The Tyee Lake hydro facility supplies power to both Petersburg and Wrangell, while the Swan Lake hydro facility provides power to Ketchikan. The project is estimated to cost $97,750 and be completed by June 2020.
Siedman recommended SEAPA replace the nickel-cadmium batteries with industry standard lead acid batteries. The lead acid batteries will be cheaper and more reliable than the current batteries. Siedman said the batteries will last for about 20 years, but have the potential to last 30 years.
The batteries typically lie in wait for an incident to happen, otherwise the only time they discharge power is during the five year capacity discharge test.
"They sit there for 15 years just waiting for the day, but we need them to be there," said Siedman. "Our DC is the backbone of our operations. When we have a trip or a relay that picks up or anything that happens on the system, the first thing that goes down is the generator and you lose AC power, so the DC is there to save the day."
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