Shuttered Coal Power Plants Find a Second Life

Gita Subramony for Zondits, August 16, 2014. Image credit: James St. John

The EPA’s Clean Power Plan and competition from clean energy sources will likely cause approximately 30% of U.S. coal power plants to be shuttered over the next 5 years. That’s great for reducing greenhouse gas emissions and pollution, but it has the potential to hamper voltage control in many markets. However, derelict induction generators from these coal power plants can be repurposed using synchronous condensers. Several closed power plants have undergone this transformation, helping areas such as Southern California avoid rolling blackouts.

Zombie Coal Plants Reanimated to Stabilize the Grid

IEEE Spectrum, July 24, 2015

Environmental regulations and competition from gas-fired turbines and renewable energy sources are shutting down dozens of older coal-fired power plants across North America and Europe. But some of these aging plants’ induction generators will go on spinning for years after their furnaces and turbines are scrapped. That’s because operators need new ways to stabilize grids deprived of big power plants, and huge, free-­spinning generators synced to a grid’s AC frequency—synchronous condensers—are becoming an increasingly popular option.

The most recent such conversion is under way at the 62-year-old Eastlake coal-fired power plant near Cleveland. Here, Akron, Ohio–based utility FirstEnergy­ has repurposed three large generators and has two more conversions in process, due to start operating by June 2016. Several other conversions have recently been completed in California and Germany, and newly built synchronous condensers are now appearing on power grids, too.

Synchronous condensers are dynamic controllers of reactive power—AC whose current wave leads or lags the voltage wave and whose presence determines local grid voltage. Adding current to the spinning condenser’s coils produces reactive power—measured in volt-amperes reactive, or VARs—and boosts grid voltage. Reduce the current and the machine absorbs VARs, depressing voltage.

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