Jun 28 - McClatchy-Tribune Regional News - Leslie Brooks Suzukamo Pioneer Press, St. Paul, Minn.

Goodbye, coal. Dirty but cheap, for the moment at least.

Hello, natural gas. Cleaner, but suddenly more expensive than anyone imagined.

Xcel Energy's new natural-gas-fired High Bridge plant is built where tons of sooty coal used to sit beside its 85-year-old coal-fired predecessor, just up the Mississippi from downtown St. Paul.

At 7:30 a.m. today, a planned implosion should topple the old plant's 570-foot smoke stack, erected in 1972. For three decades, it has pierced the sky like a concrete finger testing the breeze.

The $349 million replacement plant can crank out up to 570 megawatts of electricity, compared with the old plant's 250-megawatt capacity. Though a dedication ceremony is set for July 21, the new plant already has been pressed into operation.

This week, as the plant's director, Jim Zyduck, led a reporter through the new plant, he had to shout to make himself heard as the gargantuan turbines poured out megawatts of electricity on a hot summer day.

A massive turbine generator fed on natural gas howls like a jet engine, sending hot exhaust gases to a boiler. That heats water into pressurized steam that turns two more generators a couple of floors up.

As a source of "intermediate" power, the plant won't run all the time -- just when the operators of the Midwest power grid deem its power the cheapest available.

"When it's off, it's so quiet you can hear crickets," Zyduck joked.

The new High Bridge plant is the product

of Xcel's plan, approved in 2003, to tear down two coal plants -- the other is Riverside in Minneapolis -- in exchange for more-powerful natural gas plants built on the same sites. The replacement Riverside Plant is to be completed in May. The plan also allowed Xcel to expand a coal plant in Oak Park Heights last year after it was fitted with better pollution controls.

Minneapolis-based Xcel Energy is under a state mandate to produce 30 percent of its electricity using clean, renewable sources such as wind by 2020, and the state's other utilities must raise their renewable-based energy production to 20 percent by the same year. Other states have similar mandates or are considering them.

The natural gas plants produce no mercury, reduce emissions of sulfur dioxide and nitrous oxides to nearly nothing and slice the amount of CO2 typically emitted from a fossil-fuel power plant in half. They can be turned on and off quickly to even the flow of power from intermittent sources such as wind turbines.

"This signals a major shift in the way we produce energy," said J. Drake Hamilton, the science policy director of Fresh Energy, a St. Paul nonprofit that advocates use of renewable energy.

Although coal is cheaper now, many utilities expect national regulations on carbon dioxide to raise the cost of coal-produced electricity to the point where it no longer is economical.

At the time Xcel's plans were approved, natural gas was much cheaper.

The price of natural gas this spring hovered between $12 and $13 per million British thermal units, while it was as low as $3 per million Btu a few years ago.

The fuel's higher cost will be passed to consumers, but the true cost of the transition to natural gas is almost impossible to calculate so far.

If the government taxes carbon dioxide emissions at a low rate, the transition may seem costly, said David Morris, vice president of the Institute for Local Self-Reliance, a Minneapolis advocacy group for alternative energy sources.

But if carbon emissions are taxed highly, or if one places a very high value on reducing harm to the environment, the cost difference is negligible or even insignificant, he said.

Xcel said it isn't vulnerable to natural gas price hikes, because it has a highly diversified portfolio of energy sources. Natural gas contributes 21 percent of its power, while coal and nuclear power contribute 65 percent of the load, said Tim Carter, Xcel's director of natural gas supply. In the future, renewable energy sources such as wind are expected to take a larger role.

This diversified mix of Xcel's resources mean the price hikes will add only a few cents a month to consumer bills for the High Bridge and Riverside switch, though commercial consumers could feel a heavier burden.

Xcel would have needed to spend a lot of money anyway to retrofit its old coal plants with pollution-control equipment to bring them up to air quality standards if it wanted to stick with coal, said Bill Grant, associate executive director of the environmental advocacy group the Izaak Walton League and a leader in the negotiations that led to the replacement plants.

Some utilities still are trying to add more coal power. The proposed Big Stone II plant just over the South Dakota border would be coal-fired, and two Minnesota-based utilities are fighting to get state approval for transmission lines to their grids.

But more utilities around the country may start to build natural gas plants to reduce their carbon footprint, and the increased gas demand worries the industry, said Diane Moody, director of statistical analysis for the American Public Power Association, which represents municipal and state-owned utilities.

"Any kind of climate change bill will push people to natural gas, and that will push up the price," she said.

Leslie Brooks Suzukamo can be reached at 651-228-5475.