Comparison of Gas Turbines and Gas Engines for Distributed Power Generation
Manufacturers of distributed power generation systems have two primary options: gas engines and gas turbines. Both technologies have been successfully utilized worldwide in thousands of combined heat and power (CHP) installations. These systems are applied across various sectors, including electric utilities, hospitals, universities, district heating, seawater desalination, food processing, textiles, petrochemical refining, chemical processing, pharmaceuticals, pulp and paper production, and general manufacturing.
Over the years, both gas engines and gas turbines have seen consistent improvements in efficiency, reliability, emissions control, and operational costs. Each technology offers distinct features that cater to specific user requirements. This comparison will outline the differences between gas turbines and gas engines to help users determine the most suitable option for their needs.
Gas Turbine
A gas turbine is an engine powered by the combustion of compressed air mixed with fuel. Often considered the core of a power plant, it converts liquid fuels, such as natural gas, into mechanical energy. This mechanical energy drives a generator that produces electricity. During the process, the air-fuel mixture is heated to high temperatures, causing the turbine blades to spin rapidly.
Gas turbines are commonly used to power aircraft, ships, trains, electrical generators, pumps, gas compressors, and tanks.
Gas Engine
A gas engine operates by producing, expanding, or burning gas to generate power. Unlike large, custom-built central power plants, gas engines are mass-produced and relatively inexpensive. Multiple gas engines are often linked to form generating sets, each connected to its shaft and electric generator. These sets are available in standardized sizes of up to 20 MW.
Gas engines contribute to reducing CO2 emissions through efficient operation using natural gas, city gas, or low-calorie gases produced by processes such as gasification melting furnaces.
Comparison Between Gas Turbines and Gas Engines
Factor | Gas Turbine | Gas Engine |
Electrical Efficiency | 29–33% | 48.5–49% |
Energy Ratio (Cogeneration) | Electricity (33%), Steam (50%), Loss (20%) | Electricity (49%), Steam (15%), Hot Water (13%), Low-Temperature Water (10%), Loss (13%) |
Type of Heat Needed | Mainly steam | Hot water and some steam |
Total Efficiency (Cogeneration) | 80–83% | 63.5–77% |
Electrical Efficiency (Partial Load) | Good | Very Good |
Exhaust Heat | High temperature and volume | Low temperature |
NOx Emissions (O2=15%) | 15–25 ppm | 57 ppm |
Vibration | Ultra-low | Low |
Machine Size | Smaller machines | Larger machines |
Start-up Time | 20 minutes | 10 minutes |
Maintenance Interval | Very long | Very long |
Additional Considerations
The increasing availability of larger gas engines (above 3 MWe) with higher electrical efficiency and improved flexibility is creating competition for gas turbines.
Peaking power plants require flexible operation, often involving rapid start-up and shutdown. Gas engines excel in such scenarios, though gas turbines continue to dominate larger plants where electricity and high-temperature heat are required.
Although 30 MWe gas turbines remain popular in medium-to-large industrial sites, gas engines ranging from 100 kWe to 20 MWe are gaining market share due to their flexibility and efficiency.
Gas Turbine Control Systems
Gas turbine control systems play a critical role in ensuring the efficient and safe operation of gas turbines, which are widely used in power generation, aviation, and industrial applications. These systems regulate various parameters such as fuel flow, air intake, and turbine speed to optimize performance, maintain stability, and prevent damage. They enable real-time monitoring and adjustments to accommodate changing load demands, environmental conditions, and system requirements. With advancements in technology, modern control systems incorporate sophisticated algorithms, sensors, and automation features, enhancing overall efficiency, reliability, and operational flexibility of gas turbines.
GE gas turbine control system components include Speedtronic Mark VIe controllers, HMIs, sensors, actuators, fuel control valves, and protection systems, all working together to ensure precise operation, monitoring, and safety of the turbine.
IS200SCNVG1A, IS215UCVFH2A are examples of GE gas turbine control system spares.
Conclusion
Both gas turbines and gas engines are valuable technologies in the field of distributed power generation, each offering unique benefits that suit different applications. Gas turbines excel in high-temperature, large-scale industrial settings, providing consistent power output with high cogeneration efficiency. On the other hand, gas engines offer superior electrical efficiency, faster start-up times, and greater operational flexibility, making them an ideal choice for peaking power plants and smaller-scale installations.
As the demand for efficient and reliable power generation continues to grow, both technologies will remain essential in meeting the diverse needs of various industries. Choosing between a gas turbine and a gas engine depends on factors such as efficiency requirements, operational flexibility, emissions targets, and heat generation needs. By carefully evaluating these aspects, power producers and industrial users can make informed decisions to optimize performance and achieve their energy goals.
