Exergy in Hybrid Gas Turbines- A Review

Objectives: A review of Exergy based analysis in Gas Turbine-Hybrid systems for power generation has been presented. The purpose of the review is to understand the work carried out earlier and to identify the areas which are not sufficiently addressed. Conventional hybrid systems like Gas Turbine-Steam Turbine systems were considered along with nonconventional systems involving fuel cells, renewable energy systems like solar hybrid, and gasifier based systems. Methods/ Statistical Analysis: It is noticed that a huge body of work is available on the Gas turbine-steam turbine systems and relatively low amount of work is available in systems involving renewable energy sources. Several end-use applications such as heat generation, chilling and electricity production is possible based on the heat availability in the gas turbine. Optimization techniques were useful in the many of the Exergo economic studies that are reported in this review article. Findings: This studies show that more exergetic destruction happened in combustion chamber and fuel cell stacks owing to the high temperatures involved. Turbine inlet temperatures, compression ratio and air fuel ratio had a major say in the exergetic efficiency of the system. Innovative techniques like steam injection, inlet fogging, partial oxidation were useful for better system efficiencies. Most researchers have pointed at the commonly known parameters like the turbine inlet temperature, compression ratio and turbine exit temperature to be crucial for better exergy performance. However, there are a few researchers who pointed at much more specific areas like the combustion chamber and the HRSG to be the culprits where most exergy destruction happens. Improvements: Various techniques of hybridization of gas turbines by conventional and renewable energy systems were suggested by different authors towards capitalizing the benefits of both the systems irrespective of irreversibilities but more work is still needed to reduce the exergy destruction which would be of immense help in improving the energy efficiency and availability of low cost energy.