SRP Fired Up Over Natural-Gas Plan

Coolidge site offers supplemental power on demand
by Ryan Randazzo -The Arizona Republic May 3, 2011

A new $500 million natural-gas-burning power plant in Coolidge fired up for the first time this week, providing "peaking" electricity to Salt River Project when needed.  The Coolidge Generating Station was built and is owned by Calgary, Alberta-based TransCanada Corp.

(picture: Shannon Rasmussen,project engineer for the plant)  

SRP has a 20-year contract to dispatch the plant as needed for power on hot summer afternoons, cold winter mornings, or to balance out the power on its system when wind and solar power plants succumb to the whims of nature.

"When we went out to look for this particular facility, we really had two purposes in mind," said John Coggins, manager of resource planning and development for SRP. "One was peak capacity needs over the summer months or over peak winter mornings. Secondly, we needed a new resource that could respond well to the intermittency of renewables we are bringing on the system."

The plant went live Sunday and was sending power to the grid briefly on Monday.

The plant is only expected to run about 10 percent of the year, if that, and even less for the first few years of operation because SRP has much less electricity demand than forecast when the plant was planned, Coggins said.

Demand dropped off so much during the recession that SRP has put on hold three other power plants planned southeast of Phoenix.

The Coolidge plant has 12 small generators, which can produce about 48 megawatts of power each. If all generators are turned on at once, the power plant can supply electricity for about 144,000 homes.

The benefit of the plant is that, unlike big coal or nuclear power plants that are not efficient to run at anything less than 100 percent power, the small gas generators can be turned up and down to match power demand.

"We can dispatch just the amount we need at a moment in time," Coggins said.

For example, SRP gets power from two wind farms near Snowflake that provide about 127 megawatts of electricity when the wind is just right.

If the wind suddenly dies in northern Arizona, the Coolidge power plant can fire up two of its generators at full capacity and a third at partial capacity to make up the difference.

SRP also is building a 20-megawatt solar project southeast of Phoenix. If a cloud passes over that facility and diminishes its power output, one of the Coolidge generators can be fired up part way to make up the loss.

SRP pays a set, undisclosed price to TransCanada to have the plant ready to go. If and when the plant is turned on, the cost of natural-gas fuel and operations is passed directly to SRP customers.

The gas generators also can "regulate" the power put out by wind and solar facilities.

"For example, if the wind turbines are running, but the wind speed is variable, the power output is actually moving around," Coggins said. "We have to have resources to respond to those smaller fluctuations."

Power plants already regulate output even without renewable power sources like solar and wind on the grid because they must match the customer demand, which fluctuates moment to moment.

SRP could have used the Coolidge plant Feb. 2 when it had several problems from cold weather at its coal-fired power plants and had to cut power to 65,000 customers in metro Phoenix during the cold morning.

"They actually called us that day and asked if we were ready," said Shannon Rasmussen, project engineer for TransCanada at the Coolidge plant. "But we were not."

The Coolidge facility sits on 100 acres that formerly was farmed for cotton, and pumps groundwater for the plant. If called into action, the plant stores enough water on site to run full-tilt for 48 hours straight, Rasmussen said.

"We can run a minimum of 25 megawatts to a maximum of 575 (megawatts)," he said. "We can make any number you want."

The plant broke ground in August 2009 and had about 400 construction workers and TransCanada staff on site at its peak.

Now that it's complete, about 13 permanent employees will be needed to operate the plant.

Read more: http://www.azcentral.com/business/articles/2011/05/03/20110503srp-fired-up-over-natural-gas-plan.html#ixzz1LbWop4S9