Gas turbine units: current status, operation principle and growth options

Gas turbine units (GTUs) are highly ranked in the structure of global energy and transport thanks to the combination of high specific power, compactness, environmental efficiency and the ability to operate in peak conditions.
According to the IEA and the World Energy Data, in 2023-2024, the share of gas generation in global electricity production was about 21-23%, for many countries it is the gas turbines and combined-cycle gas turbines that are the main technology for generating the electric power and/or thermal energy from gas.
In Europe, cogeneration (including based on gas turbines and combined-cycle gas turbines) provides about 20% of electric power generation, while the industrial sector has the largest share of capacity, since the combined power and heat generation plants are predominant. The interest to this matter is growing against the background of the global restructuring of the energy sector, striving to reduce emissions and improve the efficiency of energy technologies, and also the expansion of gas transportation and gas production infrastructure in the countries possessing large natural gas reserves. In the context of the transition to low-carbon energy, the GTs are still an important component of both traditional and greenfield power plants, including combined-cycle gas turbines (CCGTs), cogeneration plants and hydrogen turbines.
Historical development of gas turbine units.
The foundations of the gas turbine cycle were laid in the 19th century thanks to the works by J. Joule and G. Brayton. The first experimental turbines were characterized by low efficiency, since the materials of that time could not withstand high temperatures. Appearance of jet engines for aviation (Frank Whittle, Germany — Hans von Ohain) became a revolutionary step. In the 1940s, the mass production of gas turbines has started, stimulating the development of heat-resistant nickel alloys and blade cooling technologies. By the 1960s, the gas turbines were widely used in the electric power industry. Appearance of combined cycles has increased the efficiency from 25-30% to 55-64%.
Thermodynamic basics of GTs operation.
The gas turbine engine operates as per the Brighton—Joule cycle, which consists of as follows:
Adiabatic compression of air in the compressor.
Isobaric heat supply during fuel combustion.
Adiabatic expansion in the turbine.
Isobaric cooling (in case of an open cycle, it means the gas release into the atmosphere).
The main parameters of the cycle:
Pressure ratio: 10-30 (ratio of compressor outlet pressure to inlet pressure); up to 40 for aviation.
Turbine inlet temperature (TIT): 1300-1700 °C.
Exhaust temperature: 450-650 °C.
The higher the compression ratio, the higher the turbine inlet temperature, the lower the turbine outlet temperature, the higher the cycle efficiency. However, there are constraints:
compressor heating,
mechanical and thermal strength of materials.
Also, the recuperators can increase the efficiency by 5-12% by heating the air with exhaust gas heat.
The global leading manufacturers of GTs nowadays are as follows:
GE (USA) — 9HA series with an efficiency of the CCGT cycle of more than 64%;
Siemens Energy (Germany) — SGT5-9000HL series with an efficiency of the CCGT cycle of more than 64%;
Mitsubishi Power (Japan) — M701JAC and M701J turbines with an efficiency of the CCGT cycle of more than 64%;
Ansaldo Energia (Italy) — GT36-S6 turbines with an efficiency of the CCGT cycle of about 63%.
Distribution of the global GTU market by manufacturers, with the long-term prospect, is shown in the Figure 1.
Figure 1. Global GTU market share by manufacturer for 2024-2033 [6]
Figure 2. The cross-section of the MHPS GTU [10]
The structural components of a gas turbine unit are as follows:
Compressor: it is the main purpose of the compressor is to compress the air. There are two types of compressors: axial — the most efficient with 10-20 stages, and centrifugal, which is used in microturbines.
Combustion chamber: modern chambers ensure equal temperature distribution, reduce emissions of nitrogen oxides (NOx) thanks to dry low NOx technologies, and the ability to burn mixtures of gas with hydrogen.
Gas turbine consisting of a nozzle box, blade, cooled single-crystal elements, and heat-resistant coatings.
Cooling system – internal air cooling, film cooling, TBC (thermal barrier coatings) are applied.
Gas turbine units are characterized by high fuel flexibility and can be powered on various types of fuel. Natural gas is most widely used, however, given the design features and operational requirements, the gas turbine units can run on diesel fuel, aviation kerosene, LPG, associated petroleum gas, synthesis gas and biogas. Application of hydrogen is a promising area: modern pilot and commercial samples demonstrate the possibility of partial or complete replacement of natural gas with hydrogen. Application of hydrogen-containing fuel mixtures makes it possible to reduce the CO₂ emissions by 10-40%, which makes such solutions especially relevant in the context of the transition to low-carbon energy.
Figure 3. General view of Siemens GTU [7]
Technical properties and efficiency of gas turbine units.
Gas turbine units have a wide range of operational properties that define their efficiency and economic feasibility. The efficiency of the GTU of a simple cycle averages 30-44%, while combined-cycle gas plant is of significantly higher efficiency, which is about 55-64%. Maximum energy efficiency is achieved through cogeneration schemes, where combined generation of electric power and heat makes it possible to use up to 90% of the primary energy of the fuel.
In terms of power parameters, the gas turbine units are divided into several categories. The low category is the microturbines with a capacity from 30 to 250 kW, which are widely applied in distributed power generation. The middle category refers to the units with a capacity of 1-25 MW, which are optimal for industrial facilities. The industrial GTUs with a capacity of 25-200 MW are applied in power plants and compressor plants. The heavy-duty units that reach a capacity of 250-600 MW, are applied in large-scale power systems and combined-cycle gas units.
The prospects for GTUs production, with the view of the unit capacities, are shown in the Figure 4.
Figure 4. The global GTU market by capacity categories for 2024-2033 [2]
The environmental performance of modern GTUs has been significantly improved due to application of low-emission combustion technologies. The nitrogen oxide (NOx) emissions are reduced to 15-25 ppm (1 ppm ≈ 1 ml of gas per 1 m3 of air) thanks to the DLN burners, the concentration of carbon monoxide (CO) usually does not exceed 10 ppm, and the content of sulfur oxide (SO₂) is determined by the composition of the fuel used.
The areas of gas turbine units application.
The gas turbine units are used in a wide range of industrial sectors, though they are most spread in the electric power industry. Such units are used in the gas turbine power plants for both base and peak generation, and provide high maneuverability and the ability to quickly increase the power. The combined-cycle gas turbine is the most rapid developing area, which in recent years have become the main technology in the construction of greenfield highly efficient power plants due to their high efficiency and reduced emission rate.
The mobile gas turbine units such as "Siemens SGT-A65" and "GE TM2500" are also crucial, since they allow to quickly supply temporary or emergency power into the grid, which is especially important when load increases and when the change in demand should be handled promptly.
Application of gas turbine units as part of cogeneration and trigeneration plants is widespread. Such systems ensure simultaneous generation of electric power, heat and cold (if absorption refrigerating machines are used). This makes GTU as effective solution for industrial companies, logistics centers, medical institutions and other facilities with a year-round demand for combined energy resources.
The gas turbines are a key component of power plants in aviation industry, and serve as the cornerstone of turbojet and turboprop engines. High specific power, compactness and the ability to operate in extreme conditions make the GTU indispensable for aviation equipment of all classes - from commercial aircraft to military aviation.
The gas turbine units are extensively used in the oil and gas sector as the drive units for compressors on main gas pipelines and gas pumping stations.
In marine transport, the gas turbine engines are used as part of the power plants of ships due to their compactness, high capacity and the possibility of rapid acceleration.
Modern-day problems and development trends.
The modern development of gas turbine units is simultaneously determined by technological advances, environmental requirements and aspiration to increase the efficiency of thermal cycles. One of the key dimensions is to increase the temperature of the turbine inlet temperature (TIT), which directly affects the level of thermal efficiency. Thanks to application of new heat-resistant materials, single-crystal blades, thermal barrier coatings and advanced internal and film cooling systems, it is possible to increase the turbine inlet temperature to some 1700-1800 °C. Such an increase in temperature ensures an annual increase in the efficiency of gas turbine cycles by 1-2%, which makes GTU competitive compared to other types of thermal units.
The most important trend is the development of hydrogen gas turbine technologies. The manufacturers predict that by 2030, a significant part of new units will be able to run on hydrogen-containing fuels: from mixtures with a concentration of 30-50% H₂ to fully hydrogen turbines, which is confirmed by publications by "Mitsubishi Power", "Siemens Energy" and "GE Vernova" addressed to development of hydrogen-capable gas turbines [3,5,7]. Hydrogen adaptation makes it possible to significantly reduce the carbon footprint and contributes to development of low-carbon energy. In parallel, combined cycles of a new generation are being introduced, including hybrid schemes with steam superheating and combined cycles using the organic Rankine cycle (ORC). Such solutions allow more extensive use of the heat of the exhaust gas and increase the overall efficiency by several percent.
Digitalization has become an integral part of the modern development of GTU. Digital twins are actively used in the energy sector, as they allow to simulate the operation of the unit in real time, predict the life cycle and prevent accidents. Predictive diagnostic systems include vibration characteristics analysis, temperature control of blade rows, pressure monitoring and operation modes optimization. With this, there is a growing demand for decentralized solutions, primarily for microturbines with a capacity of 30-250 kW, manufactured by such companies as "Capstone" and "Kawasaki". Compactness, high durability and the ability to operate in distributed power generation make microturbines highly-demanded by industry, commercial buildings and local power grids.
Economic efficiency of gas turbine units.
The economic component is one of the key factors when gas turbine technologies is selected. The average cost of gas turbine power plants construction ranges from USD 600 to 1,400 per kilowatt of installed capacity. Gas turbines are characterized by high reliability, long service life, reaching 100,000-200,000 hours, and relatively low maintenance costs.
The cost of electricity generated is also an important parameter. For simple cycle gas turbine units, the LCOE value is usually varies from 40 to 80 USD/MW/h, while for combined-cycle units it is 25-50 USD/MW/h. This makes CCGT one of the most cost-effective technologies in modern thermal power industry.
The prospects for development of gas turbine technologies are primarily related to integration into the hydrogen energy industry. Thanks to its high efficiency and adaptability to various types of fuels, the GTU is considered as one of the key technologies of the transition period, contributing to the gradual reduction of carbon footprint. The environmental burden reduction is an essential dimension. This is achieved by the introduction of CO₂ capture technologies (CCS), application of low-temperature burners that ensure minimal emission of nitrogen oxides (NOx), and blended fuels with a low carbon footprint. Compact gas turbine units capable for rapid transportation and commissioning becomes more highly-sought for temporary facilities, remote industrial sites and regions with a weak power grid.
Conclusions.
Gas turbine units continue to be one of the most technologically advanced, versatile and promising components of modern energy. Their relevance is attributable to a combination of high efficiency, flexible operation modes, ecological suitability and wide power variability. The ability to integrate with hydrogen, combined and cogeneration cycles makes GTU a key component of the future energy industry. The further development of technologies will be based on the improvement of heat-resistant materials, application of digital monitoring systems, expansion of the use of renewable gases, and the increasing needs of industry, transport and energy infrastructure. Together, those factors ensure a stable position for gas turbine units in the global energy structure of the 21st century.
Such trends are of particular importance for Uzbekistan. According to data from "Thermal Power Plants" JSC of the Republic of Uzbekistan on commissioning of gas turbine and cogeneration plants in 2021-2024, the cogeneration gas turbine units (GTU CHP) with a total capacity of 64 MW were commissioned at the Tashkent CHPP in 2024, which is designed for annual production of about 515 million kWh of electric power and 690 thousand kWh Gcal of heat. Earlier, a 17 MW gas turbine unit was launched at the "Fergana Thermal Power Plant" in 2021, which enabled to save about 3.2 million m³ of natural gas annually. These projects demonstrate the way in which the introduction of modern GTU contributes to energy efficiency improvement, replacement of fuel oil with natural gas, and development of cogeneration solutions at the local level. High efficiency is achieved due to the year-round heat recovery of the exhaust gas of the GTU with heat supply to the consumers in the form of heating and hot water.
According to the Ministry of Energy of the Republic of Uzbekistan, "Aksa Enerji" company implements several gas turbine and combined-cycle generation projects in Uzbekistan. For example, the combined-cycle power plant in Tashkent (240 MW) was implemented with the participation of "Aksa Enerji". Another plant – "Tashkent B", with a capacity of 252 MW, operates with an upgraded configuration of gas engines and steam turbines. The company plans to increase the installed capacity of its facilities to 1,170 MW, and at the end of 2023, a contract was signed for construction of a 400 MW gas-piston power plant in the Kashkadarya region [12].
All the global leading GTU manufacturers are active in Uzbekistan. A number of CCGT projects based on high-capacity GTU have been implemented and are under construction in our country: M701F (Mitsubishi Hitachi Power Systems, Ltd., MHPS), M701JAC (MHPS), MS9001FB DLE (GE), SGT5-9000HL (Siemens) and others. These are the most advanced GTUs in the world, and thanks to it, Uzbekistan is one of the "top leaders", surpassing other countries, including the CIS. The experience gained in Uzbekistan in construction and operation of GTUs is extremely valuable on a global scale.
Given the active natural gas production in the country and the energy sector modernization policy, gas turbine and combined-cycle gas units become more important tool to improve the energy security, reduce the carbon footprint and ensure reliable energy supply.
Thus, Uzbekistan not just follows global trends, but also creates conditions for its own technological advancement in terms of gas turbine generation.
References:
Boyce M. Gas Turbine Engineering Handbook. Elsevier, 2020.
Cengel Y., Boles M. Thermodynamics: An Engineering Approach, 2019.
GE Energy. Technical documentation for HA-class turbines, 2022.
International Energy Agency (IEA). Gas 2023 Market Report.
Mitsubishi Power. Hydrogen Capable Gas Turbines Report, 2022.
Palmer C., Worldwide gas turbine forecast 2025, Turbomashinery International Handbook 2025
Siemens Energy. SGT5-8000H Technology Overview, 2021.
Ansaldo website. URL: www.ansaldoenergia.com
GE website. URL: www.gevernova.com
MHPS website www.power.mhi.com
Siemens website. URL: www.siemens-energy.com
Ministry of Energy of the Republic of Uzbekistan. URL: https://minenergy.uz