Combined Cycle Gas Turbine Plants And Mississippi Power -- September 13, 2014

This story is now tracked here. 

Background for a combined cycle electric power generating plant (wiki):

In electric power generation a combined cycle is an assembly of heat engines that work in tandem from the same source of heat to produce electricity.

The principle is that after completing its cycle (in the first engine), the working fluid of the first heat engine is still low enough in its entropy that a second subsequent heat engine may extract energy from the waste heat (energy) of the working fluid of the first engine. By combining these multiple streams of work upon a single mechanical shaft turning an electric generator, the overall net efficiency of the system may be increased by 50 – 60 percent.

Combining two or more thermodynamic cycles results in improved overall efficiency, reducing fuel costs.

In stationary power plants, a widely used combination is a gas turbine  burning natural gas or synthesis gas from coal.

This is called a Combined Cycle Gas Turbine (CCGT) plant, and can achieve a thermal efficiency of around 60%, in contrast to a single cycle steam power plant which is limited to efficiencies of around 35-42%. 

Press release:

Mississippi Power announced today (August 14, 2014) that the Kemper County energy facility's combined cycle has been placed into commercial operation marking the facility's most significant milestone to date.

Putting the combined cycle unit into operation means it will be available to serve Mississippi Power customers' energy needs during the remaining summer months.

The unit was originally synchronized to the grid on Oct. 5, 2013 during testing using natural gas as fuel. 

Another significant milestone – the first gasifier heat up – is scheduled for later this year.  

The gasifiers at Kemper are the core of the integrated gasification process, which will be used to convert lignite into synthesis gas. The use of Mississippi lignite adds fuel diversity at low costs and stable prices for Mississippi Power's customers.

So, if I got this right, the new plant will use natural gas in one "unit" and gas derived from lignite in the second "unit" to achieve an efficiency of around 60% compared with less than 40% efficiency for "conventional" gas generating electric power plants.

Question: what does North Dakota have a lot of? Natural gas and lignite.

PowerOfCoal.com is reporting:

Since 1988, North Dakota’s lignite production has consistently been about 30 million tons per year, making North Dakota one of 10 major coal-producing states in the United States.

It seems one could have a combined cycle gas turbine plant using natural gas OR lignite-derived gas in each unit, but there may be good reasons for using both. I can certainly think of some.