Gas Turbine Efficiency Calculation: Avoid Higher Cost in Fuel Consumption

Power generation is largely still based on natural gas. The gas turbine technology has lately been rushing towards harnessing natural gas power more efficiently.  As a result, many users are now talking about efficiency of the gas turbine.

On the other side, major turbine manufacturers are competing to build the “most efficient” product. As the fight for bragging rights continues, the need to dig deeper into what efficiency has never been more appealing. In this article, we seek to define gas turbine efficiency calculation and review how to reduce fuel consumption.

Thermodynamics of a Gas Turbine

Gas turbines are devices for converting fuel energy into electric power (via electric generators) or mechanical power. They normally use the Brayton Cycle, which is a thermodynamic cycle that involves compression and expansion of a gaseous medium. An ideal cycle may offer 100% performance, but a real gas turbine will always have a certain level of losses and friction.

The overall balance equation looks like this in its simplified form:

Shaft Power =Fuel Energy–Power Required for Compression–Exhaust Energy- Mechanical Losses

From the equation, it means that profitability is based on the turbine’s output and the cost of fuel. The operator can only control the turbine’s output, as the cost of fuel is beyond his/her control. That is why the song about enhancing turbine efficiency is not about to stop any time soon.

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Expression of Gas Turbine Efficiency

Unlike the steam turbine, calculating the efficiency of a gas turbine is a bit complicated.  A GT presents vapor and vapor conditions that are very dynamic. These conditions are largely dependent on the atmospheric conditions and type of fuel. The conditions in the GT being variable, they must be expressed as thermal efficiency, heat rate, kilowatt-hour and BTUs per horsepower.

Performance Deterioration – Costly Effects

Every gas turbine suffers reduced performance during operation, with one of the causes of this deterioration being high ambient temperatures. Performance deterioration results in power output loss and higher fuel consumption. Both of these impacts can affect an organization negatively because they affect operation costs and revenue.

Overall, these factors can make the lifecycle costs of the gas turbine unbearable. When it comes to power generation, operating costs could exceed $1m for power loss of 3% and fuel consumption increase of 1%.

The gas turbine is composed of several components- turbine, combustor and compressor. When the characteristics of any of these components are altered, there might be increased heat rate and power output loss. This will increase fuel costs incurred by the power plant.

How can you avoid the higher costs?

There are several ways of achieving this, but we will outline one- Enhancing Power Plant Output.

GT power augmentation is ARANER’s specialty. Alongside that, we raise productivity to ensure that power plants sustain reliable performance. The company is renowned for inlet conditioning, which refers to reducing the inlet air temperature of GT. There are several approaches to this including inlet chilling, evaporative cooling and fogging.

ARANER offers inlet chilling in a technology it calls Turbine Inlet Air Cooling (TIAC). This ensures that the temperature entering the turbine does not exceed a preset temperature. TIAC provides optimal output through consistent cooling.  Moreover, the technology lowers maintenance costs and extends turbine life.

How Does Temperature Affect Turbine Efficiency?

The power output of a gas turbine is inversely proportional to temperature i.e. when the temperature decreases, the output increases. To explain this relationship, here are some insights:

  • Air density increases with decreasing temperature
  • The GT is a fixed volume device
  • Higher mass of air through the GT increases power output
Fig 1:  Gas Turbine Performance vs. Ambient Temperature

Fig 1:  Gas Turbine Performance vs. Ambient Temperature. Source

In hot climates, there is a specific problem whereby poor GT performance coincides with peak electricity demand. The engineer designing a system for such climates must make this important consideration for reliable gas turbine efficiency calculation.

Engineers at ARANER model the gas turbine system for a year, collecting ambient temperature data at regular intervals throughout this period. You can contact the team for more details about this process.

Conclusion

To reduce high fuel consumption in a gas turbine, one must first look at the different forms of gas turbine efficiency calculation.  Peter Drucker once said, “If you can’t measure it, you can’t improve it”. You need an experienced partner for thorough gas turbine efficiency calculations.

Team up with ARANER for the most comprehensive gas turbine service solutions. Services include diagnostics, monitoring and upgrades. The TIAC technology is a popular solution for reduced fuel consumption, but it does not have to stop there. Following a review of your system and the existing possibilities, other approaches could apply as well.

If you enjoyed this post, you may be want to read Ice Storage Tanks: cost effective solution for smaller footprints.

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