CCGT power station refers to a combined cycle gas turbine power station. In this station, a gas turbine and steam turbine are used to generate electricity. We know that in a simple cycle gas-fired power plant, a large amount of highly heated gas is released from the gas turbine and comes out to the environment. In that case, massive air pollution occurs, increased fuel costs, large amounts of heat losses, etc.
To reuse that exhausted gas, reduce per unit cost, and increase plant efficiency, a combined cycle gas turbine CCGT power plant is used in the gas power station. So, let’s go into deep and discuss combined cycle natural gas power plants operation, working process, technology, advantages and disadvantages, energy efficiency in power plants, and many more things. So, here we go.
What Is a Combined Cycle Gas Turbine Power Station?
At any location, if a gas turbine and steam turbine work together and generate electricity by special plan to meet the load demand. In that case, it is called a combined cycle gas turbine power station or CCGT power station. In combined cycle gas power plants (CCGPP), two main cycles are used: The Brayton cycle (for gas turbines) and the Rankine cycle (for steam turbines).
The combination of two thermodynamic cycles, the Brayton cycle, and the Rankine cycle, a combined cycle has been built. This Combined cycle step has been taken in gas power plants to enhance the efficiency by more than 60%. Nowadays this CCGT power plant is extensively used worldwide.
How Does a Combined Cycle Gas Turbine Work?
The combined cycle power plant working process is similar to an open cycle gas power station. But this fuel or heated gas is reused. A combined cycle power plant (natural gas, coal, or another fossil fuel) is burned to produce high-pressure steam. High-pressure steam drives a gas turbine to generate mechanical energy to convert it into electrical energy using a generator.
A large amount of gases is exhausted from the turbine. These hot exhaust gases are sent to the heat recovery steam generator (HRSG) to produce steam. This steam drives a steam turbine for electricity generation. In a combined cycle power plant, or combined heat and power CHP plants, some additional equipment is integrated with open cycle or simple cycle gas power plant, such as
- Heat Recovery Steam Generators (HRSG)
- Steam Turbine
- Cooling Tower
- Alternator
Heat Recovery Steam Generators (HRSG)
HRSG is crucial equipment for a combined cycle gas turbine power station. A Heat Recovery Steam Generator (HRSG) is a type of boiler. HRSG recovers heat from the exhaust gases of the gas turbine. These exhausted gas temperatures become very high around (800 to 900 degrees F) or (400 to 500 degrees C). HRSG receives that high heat exhausted steam. There are three main components installed in the HRSG:
Superheater
The superheater receives the exhaust gas that comes from the gas turbine. This gas temperature is slightly higher (maybe 535°C or more) by superheater. This high-heat steam is sent to the steam turbine to rotate. Now high heat steam hits the turbine and the turbine starts rotating and the alternator or generator also starts rotating and generates electricity.
It is noted that whenever the steam turbine starts rotating then some steam is released as exhaust steam. This steam is sent to the condenser. Condenser condenses or cools that high-heat steam. After that, this steam becomes cold water and this water is sent to the feed water heater through a condensate extraction pump.
Economizer
An economizer is an essential device for a gas based combined cycle power plant. The condensed water comes to the economizer and the economizer sends this water to the boiler drum to boil the water. Because we have to create steam again to continue that cycle or generating process. From the boiler drum, heat water comes to the evaporator.
Evaporator
The evaporator sends that steam to the superheater. The superheater enhances that heat again to more than 500 degrees C and sends that steam to the steam turbine also. This process continues, and the generator generates electricity by accepting mechanical energy from the steam turbine.
Note: This layout of combined cycle power plant shows a low amount of steam that comes out into the atmosphere that is not controllable. However, the combined cycle gas turbine power plant operation or working process relies on two main thermodynamic cycles: The Brayton cycle and the Rankine cycle. These two cycles are also used to maximize efficiency and electricity generation capacity.
Role of Heat Recovery Steam Generators (HRSG) in CCGT Plants
Heat Recovery Steam Generators (HRSGs) play a crucial role in Combined Cycle Gas Turbine (CCGT) power plants. HRSG steam generator recovers heat waste from the exhaust gas of the gas turbine to produce steam and feed it to the steam turbine. However, take a look at some crucial roles of heat recovery steam generators.
- HRSG captures the exhaust gas and utilizes it to produce steam to feed to the steam turbine to generate electricity.
- heat recovery steam generators use the recovered heat to boil water to create high-pressure steam.
- HRSGs significantly improve the overall efficiency of CCGT plants by recovering heat waste.
- heat recovery steam generators can be used in a combined cycle system with the gas turbine’s power generation.
- HRSGs offer flexibility in power generation operations.
- CCGT plants with HRSGs produce more power with a low fuel consumption.
- HRSGs can also complement renewable energy sources by providing backup power generation and grid stabilization services.
Combined Cycle Power Plant Schematic Diagram
CCPP is sometimes called a natural gas steam power plant. The combined cycle power plant diagram is very simple. So, let’s see the schematic diagram of CCPP or natural gas steam power plant.
Combined Cycle Power Plant Components
CCPP can be said to combined heat and power plants. An electrical power plant may have installed different types of equipment. A combined steam and gas turbine power plant has numerous equipment. So, take a look what are the main equipment installed in the combined cycle power plant CCPP.
- Heat Recovery steam generator
- Steam turbine
- Gas turbine
- Combustion chamber
- Compressor
- Combustion chamber
- condenser
- Boiler drum
- Cooling tower
- Alternator
- Exhaust tower
- Steam and water carrier pipe
Latest Advancements in Gas Turbine Technology for Power Generation
The gas turbine power generation process continues to evolve innovative technology. Engineers and scientists are tirelessly trying to figure out innovative and creative ideas to change anything. They also trying to improve plant efficiency, reduce environmental pollution, and minimize losses. Many advancements can be followed in the gas turbine power station, such as
- Additive Manufacturing (3D Printing).
- Advanced Materials.
- Gas turbine manufacturers are integrating digital technologies and artificial intelligence (AI) into turbine control systems.
- CCPP is used for maximum efficiency.
- Hybrid Systems Integration.
- Emissions Reduction Technologies.
- Flexibility and Grid Support.
- Decentralized Power Generation.
- Nowadays Gas turbine designs use a variety of fuels, natural gas, hydrogen, biogas, and synthetic fuels.
Final Thought
The power plant is a major thing in developing a country. That’s why all the country’s governments emphasize building electrical power stations. The combined cycle is one of the most popular ways to generate bulk electricity around the world. It can be integrated with any fossil fuel or renewable energy sources.
However, I have explained combined cycle power plant basics, combined cycle power plant working principle, and many more things about combined cycle gas turbine power stations. Hopefully, that will highly assist in knowing more about such power stations.
Frequently Asked Question
What Are the Key Considerations for Constructing a CCGT Facility?
Building a power plant requires standard, concise, and sharp planning. This is because heavy machinery will be installed and bulk electricity will be produced. It will meet the people’s load demand for a long time. The electricity supply system highly impacts to development of any country’s economy. That’s why some key consideration is required. Constructing a Combined Cycle Gas Turbine (CCGT) facility involves several essential considerations, such as
- Site selection.
- Permitting and regulatory compliance.
- Gas supply.
- Water availability.
- Grid connection.
- Plant efficiency.
- Technology selection.
- Construction and engineering.
- Environmental impact mitigation.
- Safety and security.
- Lifecycle cost analysis.
- Market and economic considerations.
Which Type of Turbine Is Used in a Combined Cycle Power Plant?
There are two main types of turbines used in the combined heat and power CHP plants. In that case, the gas turbine is considered as the primary turbine, and the steam turbine is considered as the secondary turbine. However, I can show you a combined cycle power plant example where these 2 types of turbine are used. It is a Hubu Electric Nishi-Nagoya power plant Block-1 in Japan. Hubu Electric Nishi-Nagoya power plant is the world’s most efficient combined-cycle power station. It is based on achieving 63.08 percent gross efficiency.
What Is a Solar Combined Cycle Power Plant?
A solar CCPP combines two different technologies: solar power and a combined cycle power plant. The solar energy is integrated into this system by using solar collectors or mirrors. These mirrors concentrate sunlight onto the energy receiver. It heats a fluid (often a molten salt) to produce steam. This solar-generated steam is fed into the steam turbine of the CCPP.
The integration of solar power increases the overall efficiency of the power plant. It also reduces its carbon footprint. Solar combined cycle power plants are a form of hybrid power generation. Combining the benefits of fossil fuel-based power generation with renewable solar energy to create a more sustainable and efficient electric power.
What Are the Challenges Faced with Integrating Renewable Energy with CCGT Systems?
Before designing and implementing, power plant designers and planners may face some crucial problems. A combined cycle power station is a kind of mixed and recyclable power station. In that case, the designer must keep focus on some key factors. So, let’s see what kind of challenges may face in integrating a combined Cycle Gas Turbine (CCGT) system.
- CCGT system requires careful management and balancing. Renewable energy sources such as wind power plants and solar power plants are depending on weather conditions. This can lead to fluctuations in power output. In that case, load demand or expected generation capacity may fluctuate.
- CCGT systems need to provide a consistent power supply if integrated with any renewable power source. This is because renewable energy output depends on the weather conditions. So, it is a challenge to maintain grid stability and ensure a consistent power supply.
- Integrating combined cycle gas turbine systems with renewable energy sources requires technical compatibility between different types of generation technologies like electrical and control systems.
- CCGT systems are designed for base-load or mid-merit operation. CCGT provides steady power output over extended periods. Integrating renewable energy requires increasing the operational flexibility of CCGT plants to changes in renewable energy generation and grid demand.
- Market structures and regulatory frameworks will not always facilitate the integration of renewable energy with CCGT systems. In that case, policies and regulations need to be updated to support the deployment of renewable energy.
How Do Combined Cycle Plants Compare to Coal-Fired Power Plants?
Combine cycle power stations are more advanced than coal-fired power stations and diesel power stations. Indeed, combined cycle plants and coal-fired power plants are two different types of power stations. They different methodologies to generate electricity. After also that there are many similarities between them. However, I have given here a comparison between them. So, take a look in short.
| Combined cycle power station | Natural gas is used as fuel but other fuels like diesel or syngas can be used. |
| This power plant has advance efficiency (more than 50% to 60%). | Primarily coal is used as fuel. |
| Natural gas combustion produces lower levels of carbon dioxide (CO2), sulfur dioxide (SO2), and nitrogen oxides (NOx). CCPP emits fewer greenhouse gases (GHGs). | Coal power plants have lower efficiency and it ranges from 30% to 40%. |
| Coal-fired power plants are well known for higher emissions of CO2, SO2, NOx, and particulate matter compared to combined cycle plants. | This power plant has advanced efficiency (more than 50% to 60%). |
| CCPP has higher flexibility in operation compared to coal-fired power plants. | Coal-fired power plants have slower start-up times and are less flexible in responding to changes in demand. |
| Combined cycle plant requires higher initial capital costs due to the complexity of the technology and the cost of gas turbines. | Coal-fired power plants coal-fired plants have had lower initial capital costs compared to combined cycle plants. |
What Is the Useful Life of a Combined Cycle Power Plant?
The useful life of a combined cycle power station is around 25 to 30 years. If it manages technically and efficiently its life span may increase to 40 to 45 years. On the other hand, the nuclear power plant’s life cycle is around 20 to 40 years. Coal power plant lifetime is longer than others 60 years or more. Though its production relies on the coal storage and handling arrangement.