The energy generation landscape is changing due to stricter emissions control and green energy generation regulations. The limitations of renewable energy sources necessitate the use of flexible energy production sources to supplement them. Micro gas turbine-based combined heat and power plants, which are used in residential applications, may be able to fill this void if they become more reliable. This can be accomplished by utilizing an engine monitoring and diagnostics system: real-time engine condition monitoring and fault diagnostics results in lower operating and maintenance costs as well as increased component and engine life.
Introduction
When it comes to energy generation, the share of renewable energy is steadily increasing, and the European Union aims for a 32% share of renewables by 2030, as well as a 32.5 percent improvement in energy efficiency compared to projected future energy consumption, and a significant reduction in greenhouse gas emissions compared to 1990 levels. The key targets for 2030 have been raised from those agreed upon in 2014, with an updated proposal due in June 2021.
Wind and solar power, whose generation is intermittent and unpredictable, may cause grid instability and a time lag between supply and demand for electricity. Energy storage solutions are required due to the difference in supply and demand; energy storage possibilities are now a hot topic of discussion. Pumped hydro storage accounts for the vast majority of energy stored globally, but it is typically restricted to mountainous regions. The widespread use of short-term batteries could provide a solution, and research on various battery technologies is being conducted all over the world. Although battery energy storage offers quick response times, the cost remains a major production limiting factor. Long-term demand for battery storage is expected to rise.
Advancement in Micro Gas Turbine Technology
Work in the field of micro gas turbines (particularly those with low power output levels of 1-100 kW) has recently focused on the development of components and engines with efficiency levels comparable to larger gas turbines. Small-scale effects, such as low Reynolds numbers, which result in high viscous losses, high tip clearances due to manufacturing tolerances, a large area-to-volume ratio, which results in high heat losses, and relatively high auxiliary system losses due to the low power output level, limit efficiency levels. Until recently, overall costs were a barrier to the development of components that are critical for increasing overall engine efficiency.
However, the development of small turbochargers with efficiencies comparable to small gas turbines has enabled the development of micro gas turbines with practical efficiency levels, utilizing off-the-shelf turbocharger parts from the automotive industry. A turbocharger-based microturbine concept design for a heat demand-driven micro combined heat and power (CHP) unit with 3 kW of electric power, 15 kW for heating and hot water, and a target electrical efficiency of 16 percent was proposed. Domestic applications are a competitive market for these small CHP units, with the units replacing conventional boilers in larger houses as well as in small offices where the output of the unit can cover daily needs. Such systems can become even more competitive with an increase in electrical efficiency of up to 20% due to design optimization and anticipated technological development.
Market Analysis of Micro gas Turbines
Today’s micro gas turbines are available in a wide range of power outputs. The Erwin by MTT in the Netherlands, which produces 3 kW of electric power fueled by natural gas, and the MGT by Bladon in the United Kingdom, which produces 12 kW of electric power fueled by diesel and/or kerosene, are two of the smallest commercial solutions for distributed power generation. Ansaldo Energia with the 100 kW AE-T100, Capstone with a range of gas turbines starting at 30 kW, and FlexEnergy with the 333 kW GT333S have provided larger commercial CHP solutions. Recently, Aurelia Turbines in Finland introduced the A400, a 400 kW model with a stated electrical efficiency of 40%, the highest in the small gas turbine market.
Alternative Fuel Operations
Natural gas has been the most common operating fuel for these engines, but alternative fuels have become increasingly popular in recent years. Indeed, much research has concentrated on fuel flexibility for micro gas turbines. To meet the demands of lower-grade fuels, operation with a different fuel often necessitates the redesign of the combustor, and some manufacturers opt for an externally fired configuration that can increase modularity. In an externally fired configuration, commercially available gas turbines from Ansaldo Energia and Capstone can operate with biogas as well as other fuels.
The Aurelia Turbines A400 is also capable of running on a variety of fuels, including hydrogen. MTT’s 3 kW micro gas turbine has been tested with fuel blends containing hydrogen and methane, with combustor modifications to allow for faster flame characteristics and prevent flashbacks. Because of its zero-emissions properties, hydrogen has long been proposed as an energy storage fuel. This pathway can use excess renewable energy from wind and solar to electrolyze water and produce hydrogen that can be stored for later use. This has the potential to solve the energy storage problem. However, the use of hydrogen is not without complications.
Alternative fuels derived from hydrogen can overcome some of these constraints because they have a higher energy density and are easier to store. By combining carbon captured from various sources with hydrogen, a hydrocarbon with zero net greenhouse gas emissions can be formed. The synthetic fuel can then be used in a variety of engines. Renewable synthetic fuels (e-fuels) derived entirely from renewable sources are being heralded as the path to sustainable transportation. E-methane, e-diesel, and e-methanol are examples of such fuels.
Ammonia is another fuel option that can be produced via the same pathways, but it is more toxic and has other drawbacks such as low flammability, high NOx emissions, and low radiation intensity.
Monitoring of Gas Turbines for Maintenance and Diagnostics
A monitoring and diagnostics system is required to improve the reliability of gas turbines. Monitoring a gas turbine’s condition, detecting anomalies in its operation, and diagnosing faults aim to reduce engine life cycle costs, both for operation and maintenance, and to increase safety. Avoiding unscheduled maintenance, detecting partial failures, improving repair schedules, and increasing overhaul are all ways to accomplish this.
Defects in engine components are detected based on deviations in component performance parameter values from the baseline values of a “healthy” engine. This necessitates measuring the engine’s operating parameters in real-time and using them to calculate key performance parameters. These can then be compared to those predicted by an engine model. A mathematical framework is known as Gas Path Analysis (GPA) detects changes in component health parameters by using measurable parameters in the engine’s gas path. The main principle is that hardware faults degrade component performance, causing changes in measurable parameters. The detection of these changes enables the isolation of the component whose performance has deteriorated as well as the correction of the faulty hardware.
Manufacturers like GE provides turbine Control systems that monitor and safeguard against dangerous situations. IS200EDCFG1A and DS2020FECNRX015A are some examples of such system components.
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