Natural gas seen as stabilizing the Texas wind fleet 

Tightening reserve margins are increasing the need for additional quickstart power to provide bodi spinning and non-spinning generation reserves as well as voltage support and other ancillary services to grid operators. That need is exacerbated by the increasing volume of intermittent wind generation coming on line across the United States. The need may be especially intense in Texas, which now leads in wind generation and continues to add capacity. In partial response, Wartsila will supply 202.5 MW of gas- fired capacity to provide ancillary and other grid support services to the Electric Reliability Council of Texas (ERCOT) for South Texas Electric Cooperative (STEC), a non-profit generation and transmission power provider. The contract is valued at more than $100 million.

The Pearsall Power Plant will be 50 miles southwest of San Antonio on a brownfield site. It will be equipped with 24 Wartsila 20V34SG reciprocating engines fueled by natural gas. Burns & McDonnell is providing engineering, permitting and construction management services. The plant will be connected to ERCOT and supply power and ancillary services to STECs eight cooperative members helping serve their 750 MW peak load. Pearsall is expected to run about 4,000 hours a year. The first 75 MW is expected to enter commercial operation late this year with the remaining 128 MW beginning commercial operation by the end of 2010.

For the third consecutive year, Texas led the United States in wind capacity additions in 2007. Nearly $3 billion worth of wind capacity was installed there, increasing the state’s wind capacity by almost 60 percent over 2006 levels. The 1,618 MW of new installations was more than double the amount added in any other state. Texas now has 4,356 MW of the 16,818 MW currently installed in the United States. The need for ancillary services has intensified in Texas due to that rapid growth.

Wartsila began offering arrays of natural gas-fired reciprocating engines several years ago, marketing them primarily to small utilities, especially municipals. The initial appeal was to provide rapid backup power in times of grid problems. But an additional value emerged.

“We discovered that utilities that acquired these plants had learned that the quick start, variable loading, spinning reserve capabilities of these engines gave them the ability to provide services to enhance grid stability,” said Frank Donnelly, president of Wartsila North America. In some grids, those ancillary services are traded on an open-market basis. While all utilities must provide ancillary services, open markets reveal just how much monetary value they have. “Companies see they can actually sell capacity power to provide grid stability,” he said.

Wind power’s rapid growth has increased the need for additional ancillary services to support it. The influx of renewables in such states as Texas, California and Colorado has increased the need for these grid support services, said Donnelly. An unfortunate consequence of renewables is that they add instability to the system. “You may already have a certain level of instability because of things like a weak grid and load pockets where you can’t get enough power in,” he said. “Now we see the renewable wave coming in on top of that-and not just a couple hundred megawatts of wind in Texas but thousands of megawatts. And as it keeps growing, stability becomes a bigger challenge.”

The ability to provide capacity support is increasingly helping justify the capital investment to acquire it, Donnelly said.

Wartsila’s plants can reach full plant output in eight minutes and provide 25 percent power in two minutes, one of the highest simple cycle efficiency levels available. They also offer rapid response to varying grid conditions. Pearsall will be able to run at as little as 8 MW with a competitive heat rate. This feature also increases the amount of spinning reserve available to the customer, thereby increasing the plant’s value. Wartsila’s flexible power plant can supply many commercially traded ancillary services including black start capabilities.

By Steve Blankinship

Copyright PennWell Publishing Company Feb 2008

Source: Power Engineering

redorbit.com

18 March 2008