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TEP’s Sundt Plant to Use Piston Engine Tech

Conrad Spencer, head of the Sundt generation-modernization project, says piston generators can produce power in five minutes. Credit: Mike Christy/Arizona Daily Star

By David Wincher for Arizona Daily Star

Tucson Electric Power Co. is turning to an age-old technology to back up new renewable-energy resources.

A hint: It’s essentially the same technology you use every time you drive your car.

The company plans to build a new power plant using giant reciprocating natural-gas engines — similar to internal-combustion engines that have been around since the 1800s — on the grounds of its mainly gas-fired H. Wilson Sundt Generating Station.

“This is called ‘back to the future’ because this is a reciprocating engine, it’s the engine out of your car — but it’s a V-18 with 24-inch pistons,” said Conrad Spencer, director of the Sundt generation-modernization project for TEP.

In July, TEP issued a request for proposals to build the eventual 200-megawatt gas-engine power plant, which is expected to cost north of $200M and be one of the largest of its kind in the U.S.

TEP and other utilities are looking to use the fast-starting gas engines as a flexible resource to handle peak power loads, especially to supplant power from renewable solar and wind resources, whose production drops off when clouds move over or the wind stops blowing.

Nearly 11 percent of the power delivered last year to TEP’s retail customers came from renewable resources, and TEP is working toward boosting that to at least 30 percent by 2030, doubling the state’s 2025 goal.

TEP also recently added 20MW of battery storage at two local sites, partly to provide fast, on-demand power to manage intermittent renewable resources.

Sundt’s four large gas-fired steam generators can take up to four hours to start up, and its two gas turbines — similar to jet engines — take about 10 minutes to start.

Ten minutes sounds fast, but every second counts as system operators constantly monitor and control the system to balance generation with demand, Spencer said.

The latest generation of utility-sized reciprocating natural-gas engines takes just a few minutes to start and reach full output, and they are much more fuel-efficient than gas turbines, Spencer said.

At Sundt, TEP’s plan is to replace two of the plant’s steam generators, Units 1 and 2, which burn gas to produce steam that spins an electrical generator, with two sets of five, 20-megawatt reciprocating gas engines, improving the plant’s overall efficiency.

Besides supplying on-demand power, one of the gas engines will run nonstop to meet requirements that utilities constantly generate some minimum amount of power, Spencer said, more economically replacing Sundt’s Unit 4 generator for that duty.

TEP plans to build the reciprocating-engine power plant in two phases, bringing half of the units online by mid-2019 and the remaining units into service by mid-2021.

Final bids are due Oct. 2, and the successful bidder will be announced in November, TEP says.

Read more at Arizona Daily Star.

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