The main task of a power plant is to convert energy from its other forms such as chemical energy, nuclear energy, gravitational potential energy, etc. into electrical energy. The main task in almost all power plants is the responsibility of the generator ; A rotating machine that converts mechanical energy into electrical energy. The energy required to run a generator is provided in different ways and generally depends on the availability of different energy sources in that area and the technical knowledge of the manufacturer. From a scientific point of view, the types of power plants are:
- Natural power plant: In this power plant, electricity is generated using natural factors such as wind.
- Nuclear power plant: In this power plant, electricity is generated using the energy hidden inside the atom.
- Mechanical power plant: In this power plant, electricity is generated using mechanical factors such as a mechanical motor whose rod rotates.
- Physical power plant: In this power plant, electricity is generated using physical factors such as light and heat.
- Chemical power plant: In this power plant, electricity is generated using the interactions of chemicals.
- Marine power plant: In this power plant, electricity is generated using sea water.
Combined cycle power
A combined cycle power plant is a power plant that includes a number of gas turbines and steam turbines. In this type of power plant, using a recovery boiler, the heat from the exhaust gases from the gas turbines is used to produce the water vapor required in the steam turbines. If the gas turbine is not a combined cycle, its exhaust gases, which can reach temperatures of up to 600 degrees Celsius, enter the air directly and waste residual energy. While in a combined cycle power plant, this energy is used and the steam turbine boiler produces water vapor without the need for fuel; Therefore, using this method, the efficiency of the cycle increases. Combined cycle power plants are a highly efficient, flexible, reliable, cost-effective and environmentally friendly solution for power generation. A combined cycle power plant is a combination of a steam turbine and a gas turbine, in which the gas turbine generator generates electricity, while the heat energy wasted from the gas turbine (by combustion products) is used to generate the steam needed by the steam turbine. In this way, additional electricity is generated. By combining these two cycles, the efficiency of the power plant will increase. The electrical efficiency of a simple power plant plant without heat dissipation typically has an efficiency of between 25 and 40 percent, while the same combined cycle power plant has an efficiency of about 60 percent. As mentioned, these power plants are made from a combination of steam and gas turbines and have different types depending on the type of turbines, heat recovery boilers, and recovery devices. By using steam turbines in combined cycles, its low efficiency can be eliminated and thus it can be used to provide the base load, but also its other advantages such as fast start-up and its flexibility in a wide range of loads. Benefited. Theoretically, the energy recoverable from the exhaust of gas turbines is about half the energy produced by the gas turbine itself; Therefore, the power of the steam turbine will be about half that of the gas turbine. In some designs, two gas turbines generate the energy required for one steam turbine, resulting in the production capacity of steam turbines being around that of gas turbines.
CHP power plant
In CHP power plants, the heat generated by the power generation in the generator actuators is used to provide the energy needed for heating. The cogeneration process can be classified according to the types of propulsion generators, including gas turbines, steam turbines, combustion engines and other generators. Whereas primary energy sources also include a wide range, including geothermal biomass fossil fuels or solar energy.
In fact, co-generation from a thermodynamic point of view means the production of two or more forms of energy using a primary energy source, and since the two common forms are energy, heat and mechanical, mechanical energy is often used to drive an electric generator. This process is known as the simultaneous production of electricity and heat. Now, if an absorption chiller is used to produce refrigeration and use the recyclable heat of a power plant, in order to supply the energy required by the chiller generator, it will be possible to generate electricity, heat and cold at the same time. Combined Cooling, Heat and Power).
Features and components of CHP power plant (cogeneration systems)
In contrast to centralized power generation systems (traditional thermal power plants), CHP is a decentralized and local generation method (District). This means that an independent power plant can be envisaged for each region and neighborhood. Thus, due to the proximity of the power plant to the place of consumption, the losses due to the transmission of electricity will be very small. While the rate of loss in the transmission networks of national networks is about 20% (of course, in some cities of Iran, such as Ahvaz, loss of electricity in the distribution network has been reported up to 30%). In addition, heat energy from heat recovery in generator actuators as well as in cooling systems of CHP power plants (cooling towers and evaporative condensers) can be used in two areas of high consumption and application:
HVAC: In order to provide the energy needed to produce the hot water needed to heat residential, office, commercial and other buildings.
Industry: In order to meet the need of many industrial processes for thermal energy, in various industries such as petrochemicals, paper mills and…
Therefore, in CHP power plants, due to the production of electricity locally and independently (decentralized) and the simultaneous use of wasted heat, the efficiency of power generators has increased significantly. As the efficiency of electricity generation in gas power plants is about 30%, which with the increase of investment costs and being equipped with combined cycle equipment, its efficiency can finally be increased up to 55%. However, by using the technology of simultaneous production of electricity and heat, independently, the energy efficiency of these generators will reach about 75 to 95%, which is a high efficiency compared to gas turbines and combined cycle, a great chance. Creates fuel in optimization. Meanwhile, in CHP systems, the amount of CO2 production per unit of electricity generation (kW) is much lower than other conventional methods, which will be very interesting in terms of reducing greenhouse gas emissions and CO2 tax. To the extent that many European governments, the United States and even some Asian countries such as Japan, have established policies and laws to encourage the use of CHP power plants, and this shows the importance of the CHP in reducing energy consumption.
Cogeneration systems use only one process to generate electricity, heat or cold; Therefore, the required heating / cooling capacities and electricity should be well estimated and the system equipment should be selected accordingly. This choice must be accompanied by great care. In such a way that in a certain area and range, only a part of the required thermal or electrical power can be supplied through the constructed CHP power plant; In a situation where it is possible that in another region, more heat and electricity is generated than needed. In any case, a cogeneration system will have four basic elements and components:
- Propulsion generator: a mechanism that produces mechanical force
- Electric generator: mechanism for generating electricity
- Heat recovery system: lost heat recovery mechanism
- Proper control system: management and control mechanism of all sensors and actuators
In general, due to the simultaneous production and consumption of electricity in cogeneration systems, it is necessary to set up such systems in places with the following special characteristics:
Demand for energy consumption (electricity and heat) is constant.
The demand for thermal energy is high.
If possible, the ratio of electricity demand to heating should be balanced. In other words, the conditions for the operation of the system during the day and night and throughout the year, should be such that continuous (permanent) operation of the system can be achieved.
Due to the dependence of the capacity of CHP systems on the heating needs of each complex and consequently their low capacity, CHP can be placed in the category of distributed power generation systems. In the current situation and despite the future potentials until 2030, the types of CHP technologies in distributed electricity generation, considering natural gas as a primary energy source, are as follows:
- Reciprocating engines
- Gas turbines
- Micro turbines
- Steam turbines
- Fuel cells
The importance of CHP in reducing energy consumption
Given the importance of energy saving issues and the high share of energy consumption in industry, the use of effective methods in this regard will have significant effects on the progress and development of any country. Co-generation of electricity and heat (CHP) as an efficient method to reduce energy consumption is currently on the agenda of many developed countries and a significant share of electricity and heat production required in these countries, using this method Is provided.
In CHP (CHP) technologies, excess heat generated by power generation or mechanical power is recycled to reuse energy for various uses. The use of these technologies is due to the large amount of losses when converting thermal energy into mechanical or electrical energy. These losses usually enter the chimney in the form of heat, its temperature is controlled and released into the atmosphere. By recycling some of the heat in the heat exchangers, the efficiency of the whole system increases significantly, and while electricity is generated, the heat required by commercial, industrial and public centers is also provided. Simultaneous generation of heat, cold and electricity (CCHP) systems also provide the required heat and cooling loads with the help of waste heat recovery in addition to generating electrical power. The increasing development of gas turbines and internal combustion engines of gas burners has made the use of production systems simultaneously with the primary propulsion of gas turbines and combustion engines very common. In these systems, using an absorption chiller as well as a heat recovery steam generator (HRSG), the excess heat released from the turbine (or combustion engine) can fuel the thermal and refrigeration load of the desired location without separate fuel consumption, in addition to electricity consumption. Provide. This reduces fuel consumption and also reduces the emission of pollutants.
The usual way to meet the electrical and thermal needs of consumers is to buy electricity from the grid and generate heat by burning fuel in furnaces and boilers. But by using simultaneous production technology, fuel consumption and energy consumption in general can be significantly reduced. At present, most of the world’s energy consumption comes from fossil fuels, especially oil, gas and coal. Combustion of fossil fuels causes the release of various pollutants such as sulfur oxides, nitrogen, carbon monoxide and carbon dioxide into the environment, and when they enter the Earth’s atmosphere, human health and all living organisms are endangered. In addition to emitting harmful gases, fossil fuels have limited resources, so that in the near future their reserves will end, which will face the world with a serious energy crisis in the 21st century.
The high efficiency of cogeneration units has made these units an acceptable solution for energy conversion. Also, the high efficiency of these units reduces the production of carbon dioxide and other pollutants such as sulfur compounds and nitrogen oxides. On the other hand, in countries where strict environmental laws are applied, by reducing the number of fuel conversion units to useful heat, it will be easier to control polluting production units.
Design and feasibility of construction of CHP power plant
Relying on its knowledge and expertise, Dena Turbine Engineering Company is ready to cooperate with companies and customers who intend to set up and build a CHP power plant.
Dena Turbine, with its technical and economic and geographical feasibility study, thoroughly studies the justification for the creation of a CHP plant so that dear customers do not suffer from technical errors and financial losses.
Contact Dena Turbine Engineering Company in order to cooperate and receive advice.