The global gas turbine market is expected to experience substantial growth in both the short- and long-term in response to a growing need for a reliable, cost-effective electric supply with few carbon emissions. Such growth is being spurred by increased investment in the replacement of conventional matured infrastructures.
Due to its abundant supply, ease of deployment, and relatively low cost, natural gas has become the preferred choice to fuel most of today’s gas turbines, although there is a growing movement to supplement natural gas with hydrogen.
Download our white paper Overcoming Operational Challenges to Improve Gas Turbine Efficiency and learn how engineers are adopting new technologies and tools to increase the output and efficiency of gas turbines.
The gas turbine industry has evolved a great deal in the past 100 years with some of the greatest advances being made in the areas of improved efficiency, lower emissions, and increased output. Recent innovations have focused on designs and materials that allow faster starts, quicker ramp-ups, increased efficiency, better, more reliable performance, and reductions in carbon emissions.
In the areas of efficiency and emissions control, combined cycle gas turbines have become more popular. Although more expensive, they provide an ideal means for capturing additional energy by extracting hot exhaust gases to raise steam and produce additional energy. Another recent design trend that is effectively increasing output and efficiency is the move toward larger turbines. As the size increases, the cost per kilowatt lessens. Bigger turbines are also in a better position to effectively replace coal or nuclear plant. A remaining challenge with the larger turbines, however, is that they require larger components that are harder to monitor, thus creating the need for additional sensors and analytics to avoid premature failures or added maintenance requirements.
Gas turbines will always be needed because more renewable energy sources, such as wind and solar, are not capable of producing energy 100% of the time. The challenge, however, is to develop flexible operations that can quickly respond to rapid changes in the grid. When more power is demanded, however, the industry most frequently turns to gas turbines to fill the void. The ongoing need to turn off the engines and start them up again presents its own set of challenges.
“These engines are designed to operate continuously at certain ranges. When they don’t run continuously, they are less efficient, and emissions increase. Turning them off and on is hard on the various moving components and causes more wear and tear on such things as start systems, fuel control valves, actuators, and the like. Since cycling is a harder mode of operation, there is a greater need to monitor components with sensors that can watch trending performance, efficiency decreases, and filter life”
Evan Berry, global account manager, Parker Hannifin
As engineers continue to upgrade older models to increase output and create designs that accommodate faster ramp-up, increased cyclic operation, and longer intervals of operation at low partial loads, they need to be mindful of increased deterioration of seals and bearings and a greater risk of blade flutter and fatigue damage. Temperature, fuel flow, fuel pressure, airflow, air pressure, exhaust gas flow, fuel quality, and exhaust gas particulates may also be indications that an engine is not running optimally, and that maintenance may be required.
Despite the industry’s focus on enhancing efficiency, most gas turbines today are only about 40% efficient, which means 60% of the heat generated is wasted if using a simple cycle operation that relies on a gas turbine alone. With combined cycle operations, a steam turbine uses the wasted heat from gas turbines and turns it into additional energy. The result is improved efficiency but at a considerable cost.
At the heart of efficiency, the battle is a need to run hotter. Due to the thermodynamics of the process, a gas turbine runs more efficiently and produces greater output as the temperature goes up. However, building a turbine with a higher firing temperature and efficiency is extremely difficult as there are few materials that can tolerate such high temperatures without melting.
Addressing those concerns, major improvements have been made to gas turbine components:
Superalloys with extreme temperature tolerance and durability.
Specialized seals and material solutions to handle higher temperatures assessed as critical to enabling combined cycle gas turbine efficiency beyond 65%.
Thermal coatings with improved durability to protect turbine parts from heat.
Sensors monitoring turbine performance and component life that are rugged enough to endure intense heat.
Turbine inlet cooling technologies that reduce the temperature of the intake air to mitigate reduced power output.
Although natural gas has been a preferred fuel for gas turbines for some time, the industry is undergoing a large-scale power sector shift toward decarbonization. The biggest downside of natural gas is that it is a fossil fuel that, when burned, produces various emissions, including carbon dioxide. With more companies implementing aggressive green initiatives, interest is growing in cleaner fuel sources, such as hydrogen which, when burned, produces only water as a byproduct. In response, several major power equipment manufacturers are developing gas turbines that can operate on a high-hydrogen-volume fuel that is a blend of natural gas and hydrogen.
Hydrogen, the most abundant and lightest of elements, is an attractive fuel alternative for multiple reasons:
Odorless and non-toxic, it has the highest energy content of common fuels by weight, to be used as an energy carrier in a full range of applications, from power generation to transportation and industry.
Emerging technologies to produce it are reaching technical maturity and economies of scale.
Concurrently, hydrogen is not without its problems. There are safety concerns such as:
Difficult in handling because it burns violently and, potentially explosive.
Highly combustible range, only requiring energy equivalent to static electricity to ignite.
Flashback, combustion pressure fluctuation, and NOx.
The unique characteristics of hydrogen and the mixing of hydrogen with air are chief causes of flashback, a phenomenon in which flames inside the combustor travel up the incoming fuel and leave the chamber.
Since it burns faster and hotter, materials with higher melting temperatures must be identified.
As it’s not as dense as natural gas, existing fuel lines will also need to be resized to make them larger.
Hydrogen molecules are so small that they can penetrate most metals. That requires the use of newer, softer seals and/or special metals to avoid hydrogen diffusion.
Storage problems- whether stored as a gas requiring high-pressure tanks, or as a liquid requiring cryogenic temperatures.
Gas turbines are only as good as their individual components. Today there is a greater understanding of the value of keeping components in prime condition and monitoring their performance in order to conduct maintenance before catastrophic failures occur. Yet, it’s not merely about preventing failures and scheduling maintenance during non-peak times. As a result, there has been a transformative shift from preventative maintenance to predictive maintenance. So instead of scheduling maintenance at predetermined times, regardless of remaining component life, today’s savvy maintenance managers are using sophisticated sensors and analytics to accurately measure service life and predict when worn components or contaminated fluids are at a point of adversely affecting turbine performance.
In recent years there have been major strides made in developing more sophisticated, remote condition monitoring and fault diagnostic systems. Some of the more critical areas of focus for monitoring include:
Despite some of the remaining challenges, the future of the gas turbine industry remains bright. There are several major players dedicated to developing the solutions that are necessary to make gas turbines more efficient, reliable, and green. While the market waits for the next big innovation, however, there are many improvements you can make in your own operation today to realize greater cost efficiencies and increase output.
Download our white paper Overcoming Operational Challenges to Improve Gas Turbine Efficiency and learn how to improve output from your gas turbine operations.
Article contributed by Evan Berry, global account manager, Parker Hannifin
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