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Electric Power and Natural Gas Synergism OPEN ACCESS

[+] Author Notes
Lee S. Langston

Professor Emeritus, Mech. Engr. Dept. University of Connecticut

Mechanical Engineering 139(03), 76-77 (Mar 01, 2017) (2 pages) Paper No: ME-17-MAR8; doi: 10.1115/1.2017-MAR-8

This article explains research and development in the field of gas turbine power plants. Natural gas fueled gas turbines driving generators are proving to be the most versatile and effective energy converter in the engineer's arsenal of prime movers. Continued research and development are making these gas turbine power plants even more effective, flexible, and efficient. Gas turbine plants can operate under either base load operations or in quick start/fast shutdown modes. The reliable and dispatchable backup capacity of fast-reacting fossil technology to hedge against variability of electrical supply was a key to successful renewable use in the 26 countries studied. The article concludes that the use of versatile electric power gas turbines fueled by natural gas will continue to grow in the world. In the United States, with recent shale discoveries and fracking of natural gas, such use should increase, with or without the emphasis on renewables.

As an electrical power producer, natural gas fueled gas turbines driving generators are proving to be the most versatile and effective energy converter of any in the engineer's arsenal of prime movers. Continued research and development have and are making these gas turbine power plants even more effective, flexible and efficient.

Seven years ago [1] I started this quarterly Global Gas Turbine News column with an inaugural piece on the bright future of land-based gas turbines, fueled by natural gas. During the years since, as predicted in this first column, the number and use of these power plants has increased greatly. In 2010 the worldwide value of production (in 2015 US dollars) of electric power gas turbines was $13.5B while in 2015 it was $17.5B, an increase of 30% in five years [2] — and it's still growing.

Also, based on US Energy Information Administration (EIA) data, in 2015, 33% of the US four trillion kilowatt hours of electricity was generated using natural gas, most of which was used in gas turbine plants. Where I live in New England, 40-60% of our electricity currently comes from gas turbine/natural gas plants. The EIA projects that almost 60% of new US electric power generation capacity in the next 20 years will be provided by natural gas fueled gas turbine plants.

These plants exist in natural gas burning simple cycle or combined cycle (possessing gas turbines whose exhaust powers a steam power plant), using gas turbines with outputs up to 510 MW and thermal efficiencies up to 44%. Combined cycle (CC) plants with a single gas turbine and steam turbine currently have an output as high as 764 MW and a current proven thermal efficiency up to 60-62%. (This proven performance makes CC plants the most efficient heat engines in mankind's thermodynamic history.)

Currently, gas turbine power plants have the lowest capital costs. They range from $700-$1,000/kilowatt, compared to coal-fired steam plants at about $2,000/ kilowatt, fuel cell plants also at $2,000/kilowatt and nuclear at $5,000/kilowatt.

Gas turbine plants can operate under either base load operations or in quick start/fast shutdown modes. At my institution, the University of Connecticut at Storrs, we have a 25 MW power plant, fueled by natural gas, with a backup of fuel oil. It has three gas turbines that run in base load operation, supplying campus power (and heat and chilled water) since 2006.

Many gas turbine plants are set to run intermittently, in some cases to start up to full load in a very few minutes. If the wind velocity suddenly dies in a wind turbine farm, a backup gas turbine plant can quickly pick up the grid electrical load. One 100 MW gas turbine plant we have in Waterbury, Connecticut, can quickly go online in late afternoon to take advantage of higher cost electricity rates.

Natural gas as a fossil fuel (extensively dealt with by Smil [3]), is composed mostly of methane, CH4. It is the most environmentally benign of hydrocarbon fuels, with impurities such as sulfur (hydrogen sulfide) removed before it enters pipelines. Methane has the highest heating value per unit mass (21,520 BTU/lbm = 50.1 MJ/kg, LHV) of any of the hydrocarbon fuels (e.g. butane, diesel fuel, gasoline, etc.).

Roughly 40% of the world's electricity is generated in Rankine cycle coal-fired power plants. On an energy input basis, coal produces more carbon dioxide – a greenhouse gas – than natural gas by a factor of about 1.8. In addition, if these coal plants, which operate at about a 30% thermal efficiency, were replaced by gas turbine CC plants at 60%, CO2 emissions would be reduced by almost a factor of four, resulting in a substantial 75% reduction in CO2 production [4], for 40% of the world's electricity.

Lastly, the US also has a robust and growing natural gas pipeline system (as long as 14,463 system miles for just the case of the Tennessee Pipeline Company). Pipelines are the most efficient means of bringing fuel to electric power gas turbine power plants. As Smil [3] notes, gas pipelines can have power transmission capacities of up to 10-25 GW. Contrast that to the electrical transmission lines leading away from power plants, where a single line can only have a maximum of 2-3 GW, an order of magnitude lower than that of a pipeline.

As we are aware, for over a decade or two, there has been a concerted effort to replace nuclear and fossil fuel generated electricity with renewable sources (e.g., hydropower, wind and solar) that are sustainable and economically viable. Both Denmark and Germany have been leaders in the quest for renewables, using financial subsidies to support and grow renewable electrical generation.

According to EIA data, in 2015 the US generated 87% of its electricity by nuclear and fossil fuels (33% by natural gas), 6% by hydropower and just 7% by other renewables (about 70% of the 7% came from wind and 10% from solar). The EIA projects that this 7% contributed by renewables will grow in the future, especially by wind and solar.

This has led many writers of articles advocating renewables, to assign the role of natural gas fueled gas turbines as a “transitional technology,” with an assumption that all or most electrical generation will be taken over by renewables in the future.

This assumption of a gas turbine/natural gas phase-out strikes me as if someone in the early days of the automobile, said that the gasoline powered car was “temporary and transitional,” until the electric (or steam) powered car was perfected. When the sun doesn’t shine and the wind won’t blow, we all know we need reliable on-demand electric power at a reasonable cost. As Alonso, et al [5] point out, averaged over a year, wind/solar systems deliver 25% to 45% of their nameplate production capacity. Thus backup power plants (with rapid startups) or adequate energy storage facilities (which do not currently exist) would have to deliver the remaining 55% to 75% of electricity, based on the renewable nameplate deficit. Seasonal variability is another major impediment that adds to the unpredictability of an all-renewable scenario.

A recent econometric study of renewable electric power implementation was done by Verdolini, et al [6] of 26 OECD countries for 1990-2013. Their conclusion was that the use of fast-reacting fossil technologies (e.g., gas turbines) were more likely to result in the successful investment and use of renewables. The reliable and dispatchable backup capacity of fast-reacting fossil technology (i.e., gas turbines) to hedge against variability of electrical supply, was key to successful renewable use in the 26 countries studied.

As we highlighted in the first “As the Turbine Turns…” in 2010, the use of versatile electric power gas turbines fueled by natural gas will continue to grow in the world. In the US, with recent shale discoveries and fracking of natural gas, such use should increase, with or without the emphasis on renewables.

Langston, Lee S., 2010, “A Bright Natural Gas Future”, Global Gas Turbine News, February, p. 3.
Langston, Lee S., 2016, “Clear Skies Ahead”, Mechanical Engineering Magazine, June pp. 39– 43.
Smil, Vaclav, 2015, Natural Gas: Fuel for the 21st Century, Wiley.
Langston, Lee S., 2015, “Gas Turbines - Major Greenhouse Gas Inhibitors”, Global Gas Turbine News, December, pp. 54– 55.
Alonso, Agustin, Brook, Barry W., Meneley, David A., Misak, Josef, Blees, Tom and van Erp, Jan B., 2015, “Why nuclear energy is essential to reduce anthropogenic greenhouse gas emission rates”, EPJ Nuclear Sci. Technol., 1, 3, pp. 1– 9.
Verdolini, Elena, Vonda, Francesco, Popp, David, 20916 “Bridgine the Gap: Do Fast Reacting Fossil Technologies Facilitate Renewable Energy Diffussion?”, National Bureau of Economic Research, Working Paper 22454, July, < http:/www.nber.org/papers/w22454>.
Copyright © 2017 by ASME
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References

Langston, Lee S., 2010, “A Bright Natural Gas Future”, Global Gas Turbine News, February, p. 3.
Langston, Lee S., 2016, “Clear Skies Ahead”, Mechanical Engineering Magazine, June pp. 39– 43.
Smil, Vaclav, 2015, Natural Gas: Fuel for the 21st Century, Wiley.
Langston, Lee S., 2015, “Gas Turbines - Major Greenhouse Gas Inhibitors”, Global Gas Turbine News, December, pp. 54– 55.
Alonso, Agustin, Brook, Barry W., Meneley, David A., Misak, Josef, Blees, Tom and van Erp, Jan B., 2015, “Why nuclear energy is essential to reduce anthropogenic greenhouse gas emission rates”, EPJ Nuclear Sci. Technol., 1, 3, pp. 1– 9.
Verdolini, Elena, Vonda, Francesco, Popp, David, 20916 “Bridgine the Gap: Do Fast Reacting Fossil Technologies Facilitate Renewable Energy Diffussion?”, National Bureau of Economic Research, Working Paper 22454, July, < http:/www.nber.org/papers/w22454>.

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