Five interesting details about combined cycles

Combined-cycle power plants are efficient and environmentally- friendly because they release less pollutants than other fossil fuel plants such as oil and coal.

But what is a combined-cycle plant?

Thermal power plants require a force that moves the blades of a turbine, which drives the generator rotor to produce electricity. In this way, the mechanical energy captured in the turbine is converted into electrical energy. The initial force required to move the turbine may be provided by fuels like coal, fuel oil, diesel, gas, natural gas, or uranium.

Combined-cycle plants fall in the category of thermal power plants; however, their process combines two cycles that work on a consecutive basis – one with a natural gas turbine and the other with a steam turbine. The first turbine is moved by natural gas combustion, which allows to drive the generator. This energy produces the heat needed to create steam that moves the second turbine which also drives the generator.  Please click here for more details about these plants.

What are the advantages of a combined cycle?

Flexibility. Combined-cycle plants can adapt to electricity demand or production needs. This type of plants can operate at full capacity with high demand and can bring its operation capacity down to a 45% partial load. This allows the infrastructure to produce what is necessary, avoiding market imbalances or production surpluses.

This flexibility is vital to electrical production from renewable sources like wind and sun. These are intermittent energies that depend on changing conditions from primary sources: wind and sun. Consequently, a combined-cycle power plant is ideal as backup. It can operate at low capacity under proper wind or sun conditions or to full capacity when weather conditions so require. Thus, continuous energy supply is guaranteed in places where production is mostly fueled by renewables.

Efficiency. Undoubtedly, this type of technology allows to raise generation capacity at a lower cost, thereby increasing available energy. Combined-cycle power plants performance is over 60% compared to a conventional or fuel oil power plant. This means that a higher production of electric energy is achieved with a lower primary energy (natural gas) consumption. Obviously, this has both environmental and economic benefits for the places where these plants are installed, at better prices for end consumers.

Lower emissions of pollutants that are highly harmful to the environment and human beings, such as carbon dioxide (CO2), nitrogen oxide (NOx), and sulfur dioxide (SO2), because natural gas is a cleaner fuel than coal, fuel oil, diesel and other petroleum derivatives used to produce electricity in many cases.

In this respect, the benefit is not less important for the environment and human beings since, compared to conventional fossil-fuel plants, combined-cycle plants reduce 100% of SO2 emissions, 80% of NOx emissions, and 50% of CO2 emissions.

Furthermore, transportation and supply of the main fuel (natural gas) to these plants is made through a buried pipeline, so the traffic impact from coal or fuel oil supply trucks or trains is avoided.

Lower water use. Because combined-cycle power plants require water only for steam condensation, they only use one third of the water required for conventional thermal power plants. None of Iberdrola México’s plants use municipal water for power generation. Sewage, treated, salt or sea water is used, i.e., water that is not for human consumption. If it is not available, air is used through air conditioning condensers.

Installation and operation. Combined-cycle power plants require a minor infrastructure compared to conventional plants. Furthermore, they are modular with light structures. Therefore, these plants can be built approximately in 37 months near the places where the electricity will be used. This reduces the amount of electricity lines, and thereby the unavoidable electricity losses and visual impact.

Additionally, this characteristic allows to enhance the cogeneration model by installing combined-cycle plants near other industries that can use electricity surpluses and the energy used to produce it. This is possible because electrical energy and useful heat are generated in the same process, which can be used practically across industries and facilities that use any of these energies.

In conclusion, it should be noted that Iberdrola México, at the forefront of clean energy generation, has seven combined-cycle plants in the states of Baja California, Durango, Nuevo León, San Luis Potosí, Tamaulipas, and Sinaloa. In total, these plants add up to a capacity of more than 9,146 MW. To get an idea of the importance of this capacity, let us just say that one MW/hour allows to supply electricity to an average 330 homes every hour.

We bet on Mexico and won the future.

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