Case study

Constantly optimized fan control resolves turbine tip clearance issues caused by overcooling

Industry: Electric power generation

ISSUE

Improving efficiency of existing plants is essential for carbon neutrality

More efficient and economical use of our scarce natural resources is a step we must take to achieve a sustainable and decarbonized society. Plant operators are facing a pressing need to review the operating conditions of gas turbines in their existing plants.

Overcooling hinders operating efficiency. Not being able to adjust the fan output is the biggest problem

One of the main factors hindering the operating efficiency of gas turbines is excessive cooling of the turbines. Many plants that need to use gas turbines cannot control the output (rotational speed) of their cooling fans. However, if the fan output is set to low or zero to avoid excessive cooling, it may lead to the risk of damage to the turbine components and secondary damage leading to reduced uptime.

SOLUTION

KEY POINTS TO THE SOLUTION

  • Work closely with the customer to assess their situation and find the best solution
  • Optimize fan cooling by switching to adjustable-speed fans to improve operating efficiency
  • Minimize costs with a pay-per-use pricing plan and constantly optimize operating efficiency

Work closely with the customer to assess their situation and find the best solution

The design of gas turbines varies from plant to plant. Mitsubishi Power assesses the situation including the gas turbines and the plant and works with customers to reach solutions. When a cooling fan's specifications require it to constantly run at full speed, excessive cooling will cause the turbine parts to shrink due to the temperature being lower than its design value. This causes an increase in the turbine tips' clearance, reducing the operating efficiency of the gas turbine.

Main effect image of tip clearance optimization

Optimize fan cooling by switching to adjustable-speed fans to improve operating efficiency

Mitsubishi Power offers solutions for optimized fan cooling based on our expertise of installation experience, advanced-level technologies, and historical plant operation data. In addition to switching cooling fan motors to ones with adjustable rotation speed, the modifications must also be made to the control and power supply systems. By controlling the fan motor in accordance with the ambient environment and turbine output, plants can avoid excessive cooling and optimize clearance at turbine tips, and thereby improving operating efficiency. Please note that the offer is made after estimating the installation cost and verifying the benefits to the customer. The initial cost of replacing the hardware will be covered by Mitsubishi Power.

 Image of the clearance at turbine tip optimized by switching adjustable-speed fans to avoid overcooling

Minimize costs with a pay-per-use pricing plan and constantly optimize operating efficiency

In addition, by implementing the TOMONI digital solution, operational information on turbine cooling air optimization is stored on the cloud, that allows to view the impact on operating efficiency online at any time. Because this is a pay-per-use system, you can turn the system on and off as needed and only pay for the time you use the application. You can review performance and choose whether to continue using turbine cooling air optimization, minimizing your cost burden while keeping turbines running efficiently.

Image of pay-per-use pricing plan with TOMONI Edge Enabler

EXPECTED OUTCOME

  • The Turbine Cooling Air Optimization improves gas turbine efficiency by more than +1.0% relative
  • Substantial reduction in fuel costs has been achieved in a plant which has adopted Turbine Cooling Air Optimization and Inlet Guide Vane Optimization for its three gas turbines
  • The Turbine Cooling Air Optimization has been adopted for 12 commercially operating units