There are many solutions that can be considered for power generation applications. If gaseous fuel is available, many customers today are weighing the pros and cons of reciprocating gas engines, gas turbines and other gas-fired solutions. In this article, Jenbacher experts provide our thoughts on what you should consider when selecting power generation equipment.
First, however, here’s a little background on reciprocating engines: They are used in a wide variety of power generation applications across different industries, from food and beverage applications that use less than 1 MW to industrial segments of up to 100 MW. And then there are even bigger projects for major utilities, such as the recently commissioned 190 MW project for the Stadtwerke Kiel in Germany. This large combined heat and power (CHP) project uses Jenbacher J920 FleXtra gas engines.
As a company that produces dependable Jenbacher reciprocating gas engines with electrical efficiency usually ranging between 40% and 50%, we know that gas engines often can be compared with gas turbines or any other conventional power generation technology. Moreover, gas engines can work in combination with other types of equipment, renewable energy sources or battery storages, increasing the efficiency and flexibility of the overall system. Finally, gas engines are used successfully to modernize or repower current power generation infrastructure.
Important aspects to consider when selecting power generation equipment
Because we share your desire to find cost-effective, technically reliable and greener power generation solutions, we urge you to pay attention to the following factors when comparing different technologies:
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Capital expenditures
This is one of the most important considerations for our customers. Gas engine solutions offer very competitive installed costs/kW for projects that are just a few hundred kWs to those with multiple MW installations.
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Electrical and overall solution efficiency
You’ll want to determine how much gaseous fuel your power plant will consume. Typically, 75% of the cost of energy produced is the cost of fuel, so efficiency is very important.
Jenbacher* gas engines are highly efficient, with the maximum electrical efficiency reaching well over 45%. Jenbacher equipment works in cogeneration solutions, efficiently converting the primary energy of the gas fuel into electricity and heat. In cogeneration mode, overall efficiency can reach even higher than 90%.
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Equipment production and commissioning timeline
The total production time of Jenbacher gas engine power plant components plus the time for construction and commissioning usually falls between 8 and 16 months (time to Commercial Operation Date). Your time to COD could be even shorter if units are in stock. That means you can start receiving the economic benefits of onsite power generation with gas engines in a fairly short time.
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Modularity and availability of ready-to-use solutions
When INNIO designs our solutions, we take into account our equipment’s eventual delivery to the installation sites. Our solutions can be installed in buildings or can be packaged into easily constructed modular structures. For example:
- Jenbacher Type 2, 3, 4 and 6 engines are packaged in standard containers measuring 2.4 and 3 meters wide.
- Jenbacher 920 FleXtra engines typically are built in a very modular design.The modularity of our solutions makes project logistics easier. In addition, ready-to-use solutions allow you to accelerate the commissioning of the project and effectively scale up your power plant in the future.
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Operational expenditures (OPEX)
Another very important factor in determining the choice of technology for a power plant is operational expenditures associated with the installed equipment.
You should consider such aspects as: maintenance intervals, works and spare parts cost, downtime during repairs, and equipment lifecycle duration before overhaul. We recommend customers compare the cost of the equipment’s entire lifecycle.
To minimize equipment downtime during major repairs, Jenbacher has developed long block and short block solutions that deliver overhauled engines that meet the quality and performance standards of our new units. Reach out to one of our experts to learn more.
Jenbacher also offers multi-year service contracts and Asset Performance Management tools. These help to reduce the need for spare parts and can predict service events, lowering costs throughout the engine’s lifecycle.
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Limitations on start/stop events frequency
Definitely take this factor into account, especially if you are not going to operate your equipment 24/7 and plan to stop it periodically.
Make sure to check the maximum possible start/stops within the equipment’s lifecycle, which is stipulated by some equipment manufacturers. When such limits are surpassed, the actual equipment lifecycle can be shortened, meaning you’ll need an earlier overhaul. In some cases, power generation equipment manufacturers might even require additional service payments for every start.
If you consider using gas engines, our experts can advise you whether this factor is applicable for your particular project depending on planned start/stop events frequency.
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Time to full power output and maneuverability
Our experts can help you select equipment that suits your requirements by analyzing your project’s load profile. Jenbacher's gas engine product line covers a wide range of power outputs—from 0.3 to 10.6 MWs—we can help you find a solution that fits your specific application.
You also should determine how quickly you need your power generation equipment to reach a given capacity—a factor that is especially relevant for such applications as data centers, medical institutions, oil & gas, and grid firming/peaking applications.
The standard startup time for Jenbacher gas engines is 5 minutes from initializing the start to reaching full output. Some Jenbacher Type 4 engines can reach full output in less than 2 minutes and a special version of our J620 engine achieves a full 3 MW of electric output in less than 45 seconds. The J920 FleXtra, our 10.6 MW engine, can reach full power in less than 3 minutes.
Time to full power output may vary depending on technology and model. In some cases, it could take longer than 10 minutes to reach full power and for complex application it could take even more than 30 minutes. We suggest to look closer at this aspect if maneuverability is an important factor for your project.
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Partial load efficiency
If you plan to run equipment at partial load for significant periods of time, you’ll want to seriously consider potential efficiency reduction issues. Equipment usually reaches the nominal efficiency parameters at rated power output, but at partial load, efficiency may be lessened. For Jenbacher gas engines, this efficiency decrease is quite moderate, while for other types of power generating equipment, it can be much more significant.
Moreover, our experts can consult with you about selecting engines that best fit your load profile, thereby decreasing periods of partial equipment load.
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Power output tolerance to ambient parameters
The ambient conditions under which you will operate your equipment can have a big impact on its actual power output capacity. In other words, under certain conditions your power output may be much lower than the rated power level. Pay attention to this factor if you plan to operate the equipment at high temperatures and/or at an altitude significantly above sea level.
Our gas engines typically provide full output up to 86°F and more. Our gas engines keep rated power outputs at high altitude above sea level. Contact our experts to find out more.
Why on-site power generation?
In addition to these factors, onsite power generation may provide you with significant benefits, such as:
- Decreased energy-related operating costs. When energy is produced at the place of its end use, costs can be lower than when energy is supplied by a third party via grid and central systems.
- Avoided energy losses due to electric power distribution from central power stations to distributed consumers.
- Avoided expensive power transmission and distribution upgrades due to increased local demand.
- Prompt access to electrical and thermal energy. This is especially important for energy-deficit regions and for locations that don’t have the ability to connect to centralized energy sources.
- Improved reliability of the electric power source for locations with unstable grid infrastructure and for facilities with increased requirements for energy supply reliability.
Learn more about on-site power generation here.
Gas engine and gas turbine technologies: Overview
Comparing 2 power generation technologies
In the ever-evolving landscape of power generation, two decentralized power generation technologies stand out for their efficiency and reliability: gas engines and gas turbines. Both offer the advantage of reducing reliance on long distance electricity transmission and distribution, but each technology offers distinct advantages and specific applications. Understanding the major differences can help you make informed decisions on decentralized power generation technologies.
Gas engine technology
These internal combustion engines operate on gas fuels to generate electricity. They are widely used in power plants, industrial facilities, and other sectors where reliable, on-site power generation is needed.
What is the typical gas engine power plant scope?
- Gas engine: The heart of the generator set (genset), it operates on the principle of internal combustion, where either a gas-air mixture is ignited or fuel is injected via a direct air-injection system into the cylinders to produce mechanical energy.
- Generator: Coupled with the engine, the generator (or alternator) converts mechanical energy produced by the engine into electrical energy. It consists of a spinning rotor within a stator that creates an electromagnetic field, inducing a current.
- Control system: The control panel, along with associated software, monitors and controls the genset operation. It enables the genset to operate safely, efficiently, and reliably – starting and stopping it, regulating the output voltage, and protecting the genset from overloads and other faults.
- Heat exchangers: By capturing the waste heat produced during electricity generation, the system’s overall efficiency is improved significantly. This otherwise wasted heat is repurposed for on-site heating, district heating, industrial processes, or even cooling (via external absorption chillers).
- Auxiliary equipment: This includes cooling, exhaust, fuel, start-up, and other systems.
These components work together to enable the genset to operate efficiently and reliably, providing a steady supply of electricity and heat, if necessary.
How does the gas engine work?
The process begins with the intake of a mixture of air and fuel – such as natural gas, biogas, or other gas fuels – into the engine’s combustion chamber. The mixture then is compressed by a piston and ignited by a spark plug. The resulting explosion drives the piston downward, turning the crankshaft and generating mechanical energy. This mechanical energy then is converted into electrical energy by an alternator. Dedicated engine versions also use direct port injection technology to improve both the combustion of fuels such as hydrogen and the engine’s transient performance.
INNIO Group offers a wide range of gas engine solutions that are designed for excellent efficiency, reliability, and flexibility. These engines can be used in a variety of applications, including power generation; CHP or cogeneration; and combined cooling, heat, and power (CCHP) or trigeneration.
Gas turbine technology
A standard gas turbine power plant has a scope similar to that of a gas engine plant. However, in this case, the gas turbine unit converts the energy from burning gas into mechanical energy to spin the turbine. This technology is widely used in power plants and industries due to its efficiency, flexibility, and reliability.
How does the gas turbine work?
- Air intake: The process begins with the intake of air, which is compressed, usually with a centrifugal or axial compressor.
- Fuel combustion: The compressed air then is mixed with fuel – typically natural gas or diesel – in a combustion chamber. The fuel-air mixture is ignited, producing high-temperature, high-pressure gas.
- Power generation: This high-pressure gas then is directed toward the turbine blades, causing them to spin. The spinning turbine is connected to a generator, which converts the mechanical energy into electrical energy.
- Heat recovery: Exhaust heat from the turbine can be used in heat exchangers to generate hot water or steam for various applications, a process known as cogeneration. In combined cycle gas turbine (CCGT) power plants, heat from the exhaust gas is used to produce steam, which drives a steam turbine to generate additional electricity. These processes significantly improve the power plant’s overall efficiency.
Gas engine vs. gas turbine comparison table
| Parameter | Gas Engine | Gas Turbine |
| Electrical efficiency (simple cycle) | 39 – 49% | 30 – 42% |
| Electrical efficiency (combined cycle) | N/A | 50 – 63% |
| Total efficiency (electrical + heat) | 80 – 95% | 75 – 85% |
| Exhaust heat available | 400 – 500°C | 450 – 650°C |
| Required gas pressure | < 500mbar - 12bar | 20bar - 50bar+ |
| Start-up time | 45 sec – 5 min | 5 – 10 min; 30 – 60 min (CGT) |
| Start limitations | not restricted | 1-hour operation window needed |
| Time to load acceptance | < 15 sec | > 2 min until synchronization |
| Footprint | + | + |
| Mobility | ++ | ++ |
| Overhaul interval | 60,000 – 80,000 oph | 100,000 – 150,000 oph |
| CAPEX | +++ | +++ (simple cycle); ++ (combined cycle) |
| OPEX | ++ | + (simple cycle); +++ (combined cycle) |
| COD | Several weeks | Several months |
| Ambient temperature and altitude flexibility | +++ | O |
Choosing the right power generation technology
The specific requirements of your power generation project will determine which technology – gas engine or gas turbine – you ultimately choose. Each has its own strengths and weaknesses. A thorough analysis is essential to identify the best solution for your power generation needs. Use the table above and consider the following factors in your decision:
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Efficiency
While gas turbines can achieve higher efficiencies than gas engines in combined cycle applications, gas engines offer higher electrical efficiency in simple cycle applications. CCGT setups typically require longer start-up times, which may make gas turbines a good choice for continuous base load power generation. On the other hand, gas engines tend to have better efficiencies at partial load, making them more suitable for applications with variable load profiles or for peaking power plants that need to ramp up and ramp down quickly. By cascading gas engines, plant efficiencies close to the nominal value can be achieved across a very large plant load range.
Source: INNIO Group
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Flexibility
Gas engines can start and stop quickly, and they can ramp up and ramp down their power output rapidly. This makes them a good choice for applications requiring a high degree of flexibility, such as grid balancing or integration with renewable energy sources. Gas turbines, especially larger units and CCGT applications, require longer start-up and restart times.
Source: INNIO Group
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Fuel type
Gas engines offer greater fuel flexibility and can operate on a wide range of gaseous fuels, but the specific fuel handling requirements can vary.
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Size and scalability
Gas turbines are available in various sizes, from small microturbines to large industrial units. This makes them suitable for a wide range of power generation applications, from distributed generation to large central power plants. Although gas engines generally are found in small and mid-size power generation applications, they can be easily scaled up in size thanks to their modularity and are therefore also suitable for larger central power plant applications.
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Gas pressure
Gas turbines, in general, are more sensitive to changes in fuel gas pressure. If the pressure is too low, it can affect the combustion process and reduce the efficiency and power output of the turbine. On the other hand, gas engines usually operate effectively over a wider range of gas pressures. Absolute gas pressure requirement is higher for gas turbines, especially at locations with low gas pressure (e.g. at distribution grids) the need for a gas compressor greatly increases parasitic loads for gas turbines.
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CAPEX and OPEX
Gas engines generally have a lower upfront capital cost compared to gas turbines. They may require more frequent maintenance than gas turbines, but these tasks generally are simpler, therefore less costly and require shorter downtimes. Gas turbines have a higher initial CAPEX, though can operate for longer periods between servicing, but the maintenance tasks can be more complex and more expensive with extended downtimes. With proper maintenance, both technologies can have a similar lifespan.
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Environmental impact
Gas engines and gas turbines typically have low emission values. However, further decarbonization is possible with additional emission control technologies such as SCR systems or by using carbon-neutral fuels like green hydrogen.
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Altitude sensitivity
As the altitude increases, the air becomes less dense, which can reduce the power output and efficiency of both technologies. However, gas turbines generally are more affected by changes in altitude than gas engines. The two-stage turbocharging technology of gas engines enables stable power output even at higher altitudes. A capability that presents challenges for turbine technology to achieve.
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Ambient temperature
Although higher ambient temperatures can reduce intake air density, which can, in turn, reduce the power output of both technologies, gas engines have significantly better performance than gas turbines at hot ambient temperatures. Gas turbines draw in large amounts of air for combustion, and temperature directly affects the density of this air. With control systems, the fuel-air mixture and ignition timing can be further enhanced to compensate for these changes, helping to maintain performance. Gas turbine power ratings are typically given as per ISO Standards at 15°C ambient temperature, and gas turbine technology specifies power output at ISO standard at 25°C. Two-stage turbocharging technology allows gas engines to run at full load power output at ambient temperatures well above 45°C. Through simple turbo charger adjustoment improved performance at high ambients can be achieved with gas engines whereas turbine technology needs to rely on active air inlet cooling, which involves additional costs and also consumes valueable resources like water.
The Jenbacher solution
Jenbacher 50 MW power plant
Advantages of Jenbacher engine technology:
- Efficiency: Gas engines can reach high levels of efficiency, particularly in combined heat and power (CHP) systems and high ambient temperatures and altitudes.
- Flexibility: Because they can be started and stopped quickly, gas engines respond efficiently to changes in power demand. In addition, gas engines can work in partial load mode as needed and are scalable in size.
- Environmental impact: Gas engines also can run on a broad range of energy sources, including renewable fuels such as biogas, industrial by-process gases, and even hydrogen of up to 100%.
- Modular solutions: The modular design and high engine reliability help increase uptime and low maintenance requirements of the power plant.
- Advanced digital solutions: myPlant AI-powered platform for remote monitoring and predictive analytics, helping to enhance performance and efficiency of gas engines fleet.
- Energy transition support: With the increasing share of renewable energy sources (RES) and decentralized power generation solutions, gas engines play a significant role in the energy transition by providing a flexible, efficient, and reliable power to the grid, ensuring stability in combination with variable renewable energy sources.
With more than 13,000 of our Jenbacher CHP systems delivered around the globe, INNIO Group is a global technology leader in engine-based power generation. Our Jenbacher experts can work with you to determine if gas engines are the right choice for your power generation project. And, with our wealth of experience, we can dive deeper into the costs and benefits of your project to find the solution that best meets your specific needs.
A Jenbacher cogeneration plant consists of the power generation unit with an engine and a generator along with heat exchangers to take advantage of the heat resulting from the combustion process. The energy systems use all related heat sources such as the engine cooling water, lubricating oil, the air/fuel gas mixture and the exhaust gas. Water temperature levels of 100°C and more can be achieved, making Jenbacher CHP and CCHP solutions highly flexible.
Our experts are ready to help you!
Looking for onsite power solutions?
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Want to lower your energy costs, or even sell electricity back to your local grid?
INNIO’s regional experts can help you figure out the Jenbacher solution that best meets your needs. With a free consultation, you can:
- Explore the advantages of onsite power generation solutions for your company
- Discover how to use economic modeling for added financial benefit
- Get answers on the technical aspects of your project—including fuel types, feasibility studies, and equipment and balance of plant selection
- Learn how to take advantage of regional incentive programs
- Review the delivery options for your project: purchasing, financing, leasing, and engaging a service provider, such as ESCO or BOO
- Find out how to meet emissions targets
Fill out the following contact form or send us an email to contact.en@innio.com. Let's get started!
Resources & Downloads
Jenbacher Webinars – Designing Your Power Plant (2022)
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Category: Webinars
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Whether your business is looking for onsite power solutions, access to electricity, decreased energy costs, or even to sell electricity back to your local grid/consumers, Jenbacher regional experts can advise you on which solution makes the most sense for you.