A gas turbine is a type of internal combustion engine that has a rotating compressor in its upstream side, coupled to a turbine in its downstream side. In between, in the combustion chamber fuel is mixed with air, ignited, heats and expands with the added energy. In the high pressure environment of the combustor, the temperature is increased by the combustion of the fuel. The combustion exhaust is forced into the turbine section. From there, high volume and velocity of gas flow straight through a nozzle over the blades of the turbine, spins the turbine that powers the compressor and for some turbines, drives the mechanical output. Energy given to the turbine is from the reduced temperature and pressure from the exhaust gas. Energy is then extracted in the form of compressed air or thrust, shaft power, or any combination of these. This energy is used to power aircraft, trains, generators, power generators, ship and tanks.
Gas turbines are thermodynamic. Air is isentropically compressed, at constant pressure combustion occurs, and expansion through the turbine takes place isentropically back to the starting pressure. Modern technology engineering and manufacturing processes keep the parts of the turbine cool. They are used for production of electrical power. Industrial gas turbines vary in size from simple mounted mobile plants to complex and enormous systems. They are at least 60% efficient when the waste heat from the gas turbine is to power a conventional steam turbine in a combined cycle configuration. They are run in a cogeneration configuration up to 80% efficient. Cogeneration configuration is where the exhaust is used to heat space and water and / or drives a chiller for refrigeration or cooling.
One of the most critical areas of consideration for any nation is power generation. Countries around the world are looking into the importance of energy conservation, production and employing ways and means to create energy. One such consideration is the funding of building gas turbine power plants. In Nigeria, currently they have four major sources of electricity. These are thermal, hydro, gas, and coal. Among these, gas turbines have the edge over the others. Its four factors that makes it ideal:
Peak Load Machines.
Gas turbines are very flexible, thus they are deployed as peak load machines especially that they come in handy during peak period when generation is needed in the grid system. It is when consumers are using maximum power from the grid that they work effectively like a peak load machine.
Installation cost is very minimal.
Installation cost of any power plant is a crucial factor when selecting the type of turbines to be installed in any power system. A gas turbine of 400 megawatts with three units can be commissioned and built at a cost no more than 300 million dollars.
Low cost maintenance.
They are basically low maintenance machines, because of the low maintenance costs that are involved. Maintenance costs are connected to the fact that most of the gas turbines’ functions are automated. That alone reduces the running costs of the machine.
Quick machine start up.
To make it start, it takes only an average of five minutes to run up to full speed, no load and finally synchronized to the grid. That feature is very important more especially when the system power is need to reach developmental purposes.
Gas turbine technology is continuously evolving since its humble beginnings. Research is working on producing these into smaller, more efficient combustions, better cooling engine parts, reduced emissions and more powerful. On the emission side, technology is working on a combustor that will properly run to achieve no emissions. In the 1990’s compliant foil bearing were introduced to gas turbines. These can withstand more than hundreds of start / stop cycles and do away with the need for an oil system.