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Gas turbine technology is becoming increasingly popular in the Middle East and North African region as countries scout for means of boosting power generation without putting a heavy cost on the environment.
Seizing the opportunity, GE Energy has over the past year made available its gas turbine technology for projects where power is primarily used by its customers for industrial processes.
Using natural gas as its primary fuel, GE's power plant will be in operation at the world's largest single site aluminum processing complex in Abu Dhabi and feature specialised gas turbines, steam turbines, heat recovery steam generators and condensers.
GE Energy gas turbine technology has also been selected to help meet Egypt's energy demand, which is growing at an annual rate of seven per cent.
GE and its partner Techint Cimi Montubi will supply two Frame 9FA+e gas turbine-generators, auxilliary equipment and training services to the Upper Egypt Electricity Production Company, which is owned by the Egyptian Electricity Holding Company.
The machines will be used for an expansion of the El Kureimat Power Plant, located about 90km south of Cairo.
In combined-cycle operation, the new El Kureimat III plant will add 750 megawatts of power to Egypt's electricity grid.
Gas turbines are a mature and economically efficient technology with broad acceptance in the electricity market place. The installed capital cost of a gas turbine cogeneration system varies between $800-$1,800/kwh. This is due to large variations in turbine size from a few kw to many hundreds of megawatts. The operation and maintenance costs range from $0.3c-$1.0 c/kwh.
Gas turbines are currently the favoured prime mover in larger-scale cogeneration wherever natural gas is available at costs less than three to four times the equivalent energy cost of solid fuels. For operation, intake air passes through a compressor before being heated by the combustion of the fuel.
The expanding air is then used to drive a turbine before exiting through the exhaust and heat processes.
Compressors require a large amount of energy, making the choice of compressor crucial to the overall efficiency of the turbine.
The electrical efficiencies of modern gas turbines range from 28 per cent to 42 per cent simple cycle efficiency, with typical efficiencies of 32 per cent. For systems larger than 3mw, the gas turbine exhaust, typically around 540¼C, can be used to produce high-pressure steam, which then powers a second generator.
Such combined-cycle gas turbines (CCGT) have electric efficiencies of 35 per cent-55 per cent. The pass-out steam from the steam turbine can be used to meet on-site heat requirements increasing overall efficiencies to 75 per cent to 90 per cent. This lowers electricity production, but improves overall economics.
To improve electrical generating efficiency and reduce nitrous oxide (NOx) it is possible to inject steam into the combustion chamber. Current production gas turbines have NOx emissions from 2 to 25 ppm, before external controls. Additional NOx reduction methods have been successfully developed for gas turbines, so where very low emission levels are specified, it is possible to attach end of pipe solutions such as Selective Catalytic Reduction (SCR).
"Gas turbine technologies are the cleanest techniques within systems that use fossil fuels and are favoured in GCC countries due to the low cost of available natural gas," says Abdullah Al Amiri, chairman of the Emirates Energy Award.
He says calls to use alternative energy resources across the world are increasing and these have taken priority on the agendas of research centres, energy industry conventions and parliament sessions - all because of spiralling global oil prices.
Because of this and the dependence on one energy source, Al Amiri says, the GCC countries are also increasingly searching for alternative energy sources.
As for the other available alternative energy sources, he says: "There is the coal-fired power plant, which is burned by coal gasification, a very efficient method for extracting energy from coal, and the best solution to help reduce emission and pollution. The GCC countries are continuously confronted with the issue of depletion of natural gas resources in the region."
Al Amiri, however, holds the view that wind energy is not feasible for the UAE as wind speeds in the country are not adequate.
A study conducted in the emirate of Fujairah showed that the wind speed level in the country is only 25 per cent of the level required for a windmill to generate power. Solar power generation techniques continue to be expensive.
Coming to the question of nuclear power, Al Amiri says this remains a topic for debate as the low cost of power generation is offset by the high initial investment required.
However, there are some distinct disadvantages that come with using gas turbine technology. Firstly, gas turbines require premium fuels, often natural gas, which have high price volatility.
Secondly, the high temperatures involved requires heat-resistant materials, raising production costs.
Thirdly, small system costs are relatively high and efficiencies are lower than with some other generation systems.
Finally, gas turbines offer reduced efficiencies at part load and turbine performance is significantly reduced at high altitudes or high ambient temperatures.
