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Introduction to Gas Turbine Power Plants

The demand for Gas power plants is increasing because of certain benefits. Natural gas is used as a fuel, other fuels can be synthetic gas (syn-gas). Just like steam power plants in which operating fluid is water and steam mixture, in gas turbine power plants, air mixture is used as a derivative fluid. In a jet engine, one side has a turbine and one side has a compressor, the air is entered in the compressor, it mixes up with the fuel, it ignites, and then it ejects it from the turbine. The turbine converts the pressure and velocity into electrical power through the generator. A major problem in the operation of gas turbine power plants that when the fuel is being ejected, its temperature is 400-500 °C, which can cause atmospheric pollution, and a lot of energy is wasted. Because of this wastage of energy, the efficiency of normal gas turbine power plants and open-cycle gas turbines is around 20-25% which is way less than its potential, even steam turbines have greater efficiency than this. The compressor and turbine are on the same shaft mostly. Compressor drives and compresses the air 15-30 times and then the fuel is mixed and when that mixture passes through the gas turbine at high pressure, the energy is converted. The energy required to drive the compressor is delivered to the compressor from the same shaft through the turbine, which means the major portion of the energy is utilized by the compressor to drive and the rest of the energy is utilized in the turbine. The compressor has multiple stages, low-pressure compressor, intermediate pressure compressor, and high-pressure compressor. The compressor is the opposite of the gas turbine. The turbine uses kinetic energy and converts it into rotational kinetic energy, however, the compressor uses the rotational kinetic energy to convert it into potential energy of air and fuel mixture.

Major Parts of a Gas Turbine Power Plant

Operation of a gas turbine power plant Gas Turbine A gas turbine is used to convert the kinetic energy of hot gases into rotational energy, which in terms is used to drive the synchronous generator. It also has multiple stages, High-pressure stage, intermediate pressure stage, and then low-pressure stage. The combustion process takes place in the turbine, so, in order to save the blades from melting, the cooling process also occurs here. Most of the time, a cooling fluid is constantly passing through the blades. Compressor It is mounted on the same shaft, it compresses the normal air and delivers it to the combustion chamber. It also has multiple stages, low-pressure stage, intermediate pressure stage, and then high-pressure stage to increase the efficiency. Combustion Chamber The compressed air is entered here and it mixes with the fuel. It is then ignited here, which causes an increase in temperature and pressure. The temperature can go as high as up to 1400 °C. At this very high temperature, the nitrogen can combine with oxygen to produce nitrogen oxides, but this is controlled such that all the oxygen is utilized in the combustion process. Auxiliaries for the operation a gas turbine power plant Different starting devices, Fuel system, Oil system, Lubrication Pump but they are not the parts of our focus.

Thermodynamic Cycle of a Gas Turbine

Gas turbines operate on Brayton Cycle. 25% of energy production in the world is based on gas-turbine power plants. This percentage will increase further when there is a decrease in energy production using fossil fuels. The efficiency of open-cycles can be increased by up to 38%. Small scale gas turbines can be used to obtain 35-45 MW of energy.

Thermodynamic cycle of a gas turbine

Open Cycle Gas Turbine

If the exhaust is dispersed in the atmosphere, this is called the open-cycle gas turbine, the energy of exhaust cannot be recovered. 50-55% of energy is wasted in the exhaust. 1. Combined Cycle Gas Power Plant In a combined-cycle, exhaust gases are used in the steam turbines and their energy is recovered and utilized. Larger gas turbines have less efficiency but due to modern research, its efficiency is increased up to 38.7% and its unit size is also increased. Previously 50 MW of gas turbine units were used but now, up to 265 MW units can be used. The efficiency of the gas turbine plant depends on the inlet and outlet temperature of the turbine portion. The inlet temperature is around 1400-1600 °C, and the exhaust temperature is about 400 °C. So the lower efficiency is due to this temperature difference. In future, if good quality material is used, the temperature of combustion chamber can be increased, which can cause our overall efficiency to increase. ENERGY CYCLE:

Energy Cycle of a gas power plant Inlet energy is due to ambient temperature, so it is minimum.The compressor compresses the air 30 times, then it is mixed with fuel and burned, so, the major portion of the energy is from the fuel mixture.Compressed air energy + fuel energy is the inlet energy.It is converted into rotational energy.It is converted into electrical energy.Around 80% of energy is wasted in open-cycle gas turbines, but it can be recovered if we use combined-cycle gas turbines.

Methods to Increase Efficiency of an Open-Cycle Gas Turbine Power Plant

There are two techniques available to improve the efficiency of n open-cycle gas turbine power plant: Combined Cycle Power PlantIntegrated Gasification Gas Turbine Power Plant 1- Combined Cycle Power Plants The exhaust waste is used in heat recovery steam generator. Mainly 2 turbines are used, 1 is gas turbine whose exhaust is utilized by the heat recovery steam generator and generate steam and run the steam turbine. So, in 1 unit, there are 2 turbines and 2 synchronous generators. Efficiency can be increased by 50-60%.

Combined Cycle gas power plant 2- Integrated Gasification Cycle Power Plants When fuel is not available, other fuel is gasified, boiler (gasifier) is used to gasify the low quality coal, waste material or bio mass by partial combustion. After it is gasified, the hot gases produced are CO, H2, CO2 which are used.

Integrated gasification gas power plant

Choice of Fuel in a Gas Turbine

Based on the characteristics of the fuel gas, gas turbines are designed. Only then, the designers can guarantee the proper working of turbine. The design of combustion chamber is of prime importance for efficiency. Similarly, the temperature and pressure are also continuously monitored.

Advantages of a Gas Turbine Power Plant

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Final Words

This is the second article in Wind Power Plants Course. This article discusses the development and early history of wind turbine. Wind turbines have gone tremendous change from crude wind trubines to the modern horizontal axis wind turbine. Human existence without technology is unthinkable. Already in primaeval times, humans discovered how to adapt and exploit what nature had to offer, and started producing tools to satisfy their needs. Humans learnt how to modify materials in order to produce items such as ceramic pots, steel articles, plastic parts, medicines and much more. They also came up with possibilities of communication ranging, for instance, from cave paintings 20,000 years old through Greek torch telegraphy right up to modern cellular phones. So is the history of the wind turbine. Not least of all, humans learned to harness the energy of fire, water and wind.

Development and History of Wind Turbine

This section describes important stages in the evolution of wind power plants The first windmill Utilization of wind energy began with sailing boats and ships more than 5000 years ago. As early as the 7th century A.D. the first windmills were built in Persia, or modern-day Iran, for the purpose of grinding grain.

First Wind Turbine in History A perspective of the mill from above (top view) reveals its operating principle.

Flow of Wind in Early Wind Turbines The force of the wind turns the fabric-lined rotor horizontally, causing the vertical shaft to drive the millstone directly. The wind collecting walls guide the wind toward one half of the rotor wheel while the other half is in the lee. This prevents the wheel from blocking itself. The wind wheel's position is fixed, i.e. suitable only for one particular wind direction. Tower windmill

Tower Wind Mill This also applies to the more advanced tower windmills. Present in the Mediterranean region for the last 1000 years or so, these windmills have operated in regions with prevailing winds. In some countries, such windmills remain in use to this day. Furnished with sails, the wind wheel rotates on a brick tower and moves the millstone via a gear mechanism. German windmill

German Wind Turbine From the Middle Ages to the 18 century, German windmills were the most commonly found type of windmill in central and eastern Europe. This design was able to follow changes in wind direction, the entire mill house being rotated via the tail. The mill house is mounted on a substructure or base. Dutch windmill

Dutch Wind Turbine Windmills reached their most advanced stage in the 17th century with the development of the Dutch windmill which incorporated an elegant solution for following changes in wind direction. Only the roof crown on which the windmill vanes are mounted turns on rollers installed along the tower's edge. As in the case of the German windmill, a tail is used to turn the superstructure, with a wind rose serving as orientation. The mill house as such remains fixed, which makes it more stable and capable of enlargement. History of Modern Wind Turbine So far, wind wheels have supplied energy for driving: mills of various typesirrigation and drainage systemshammer, stamp and saw millselectric generators

Modern Wind Turbine for Wind to Electrical Energy Conversion Development of high-speed wind turbines with aerodynamically shaped vanes began about 50 years ago. These turbines achieve higher efficiencies than conventional, low-speed wind wheels. The development of wind turbines is by no means over: Research projects involving wind power plants of various capacities are in progress worldwide.

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Introduction to Wind Power Plants

Welcome to the course titled Wind Energy Conversion Systems. The EE Power School team wishes you lots of fun and success in working through the course topics and understanding the basic concepts that lie behind the renewable energy resources. This course will provide you with a basic understanding of the functioning and working of the basic wind turbine and the grid interconnection of the wind power plants to the national power grid. The general prospects for the global wind-energy market are bright: Due to their rapidly growing energy needs, emerging economies such as China and India also need to rely on renewables if they want to catch up with industrialized nations in times of rising raw material shortages. At the end of February 2005, for instance, China passed a law promoting renewable energies. According to the Danish management consultancy BTM, annual growth in the wind power sector may rise to 115,000 MW by 2025. And a Windforce 12 study by Greenpeace and GWEC forecasts a market volume of 160,000 MW of newly installed capacity by 2020.

Wind Turbines

Wind Turbine for Wind to Electrical Energy Conversion This course on wind turbines systems describes the design and function of modern wind power plants. The control of variable-speed wind turbines is studied using a doubly-fed asynchronous generator or induction generator as an example. Wind Plant emulation tools are also discussed which can be used to emulate the behaviour of the plant realistically with a servo-machine test stand and "WindSim" software.

Learning objectives of the Wind Power Plants Course

Understanding the design and operation of wind power plantsLearning about the physical principles whereby wind power is transformed into shaft powerLearning about various wind power plant concepts Studying the design and operation of a doubly-fed asynchronous (induction) generatorInvestigating generator operation at various wind intensities, as well as control of output voltage and frequencyDetermining optimal operating points under various wind conditions

The Course Contents

This course on wind power plants cover: History of wind power plantsWind power plants in Energy MixWind power plant designComponents of a wind power plantConstant and Variable speed wind turbinesOperation of a Doubly Fed Induction Generator (DFIG)Regions of High and Low Wind ProfileThe mechanism behind wind blowingWind Speed ProfilesPhysical Principles of a Wind TurbineOperation and Power conversion of a Wind TurbinePower Calculation and Mathematical Relations

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