Turbine Inlet Air Cooling (TIAC) is a fast-growing technology in hot and humid climates that hinder turbine performance, for example Saudi Arabia. Industrialization plans in such a region would be difficult, save for this amazing technology. In electricity generation, the gas turbine is a key feature. It is regarded as a constant volumetric flow system that relies on ambient air as a working fluid. This makes ambient pressure, humidity and temperature important factors in the performance of gas turbine power plants. In this post, we will outline the engineering and design process that revolves around the components of a TIAC plant.
Gas Turbine- Performance Capacity Matters
According to the standard reference conditions provided by the International Organization for Standardization (ISO) in ISO 2314, gas turbine rating for intake air is 101.3 kPaa pressure, 15 °C temperature and 60% relative humidity. Of course, this rating is assumed for a gas turbine installed at sea level or ideal conditions. The aspect of Turbine Inlet Air Cooling comes in when the ambient temperature is significantly higher than the recommended 15 °C temperature. Note that for perfect installation of a gas turbine anywhere on the globe, it is paramount to consider other site conditions too. Other than temperature, pressure and humidity, other considerations that may change from site to site are inlet losses, exhaust losses, fuel requirements and relative humidity. Temperature just happens to have the biggest impact on performance and energy efficiency.
Configuration of a TIAC Power Plant
The role of any gas turbine power plant is to convert fuel energy into mechanical energy for electricity production. Basic parts of this plant are gas line, oil storage, air intake and compressor. Others are transformer, generator, exhaust and the turbine itself. Now, for a TIAC power station, an interesting alteration happens- inlet air is cooled to or close to 15 °C. TIAC generally takes two approaches: mechanical type method and “wet” evaporative method. “Wet” methods tend to show problems in humid conditions, as the supply of demineralized water in such conditions may be unavailable or impermissible. Further, water must be of the highest quality always to avoid corrosion of turbine components. For mechanical chilling, heat exchanger technologies and modern water chillers are used to deliver the cooling needed by the gas turbine for optimal performance. The process happens in the following simplified steps:
- Ambient air enters the system via filters
- The filtered air enters the chilling coils
- Air losses heat through a thermo process
- Air, now at the desired temperature, enters the turbine compressor
Fig 1: ARANER TIAC System
ARANER has many years’ experience in industrial cooling using this technology. We have applied TIAC power solutions in many power plants globally, especially in the Middle East. As interest in TIAC for power plants increases, we encounter clients who want to understand more about the components used. The engineering and design approach for these power plants elicit a lot of excitement.
Design Conditions for the TIAC Plant
Design of a TIAC power plant can be problematic if you are not familiar with the natural steps needed. At ARANER, we follow FIVE design parameters:
- Ambient conditions
- Desired air cooling
- Heat rejection type
- Thermal energy storage
- Combined or individual plant
1) Ambient Conditions
To start the design process, the team performs annual analysis based on a proprietary developed software which provides hourly weather conditions data. In addition, it is a general practice to go to the field to obtain real weather data for final verification. In the preliminary study, the team defines dry bulb temperature and wet bulb temperature. With a view to optimizing the TIAC engineering solutions in terms of cost and energy, the next step is to engage the psychometric chart. Of utmost importance in this step is to avoid oversizing or under-sizing the system.
2) Desired Air Cooling
Weather data evaluation is followed by a determination of the amount of air intake into the gas turbine. Considering the unique case of each power plant, ARANER considers every desired cooling separately. The team seeks to know the Inlet Air dry bulb temperature downstream the TIAC system and the Air mass flow at the conditions downstream of the TIAC. Although the ISO conditions references the power output at 15.0 ºC ambient temperature, it is important to note that sometimes engineers are forced to cool further or even stop it at 20 or 25 ºC due to economic or technical reasons.
3) Heat Rejection Type
To reject heat from the refrigeration process, we have three options namely air cooled, water-cooled and effluent, usually seawater or river water cooled. Each of these has advantages and favorable factors. For instance, seawater cooled comes out as frontrunner for a TIAC power plant that is located close to the sea or water body. For a power plant that is not close to either a river or sea, then ARANER can design and install an air-cooled option or if water is available, a water cooled option using evaporative condensers, cooling towers and other components.
4) Thermal Energy Storage (TES)
Thermal Energy Storage (TES) integration into the TIAC solution is an important consideration for the engineering and design of the power station to be complete. Together, they form a TESTIAC system that produces cooled water (other forms are also available) during off peak hours and keep it in tanks. This water is then used to provide a constant cooling temperature for the gas turbine at peak hours, thereby achieving increased efficiency and output of the gas turbine.
5) Combined or Individual Plant
This consideration may not be as important as the other four, but it is worth checking nevertheless. A TIAC plant can be designed for each gas turbine or one large centralized cooling plant can be dedicated to all the gas turbines. If you ask a specialist, a centralized plant is better, especially if there is space limitation.
Gas turbine or combined cycle power plant performance depends largely on the quality of inlet air, specifically the temperature. In the design of the various components of the plant, this fact must always be prioritized. Modern power plants in the hotter and humid locations are using TIAC system to decrease the inlet temperature. Net power output increase is often impressive, making the payback period for installing the system only a few years. If you are interested in more about the engineering and design of a TIAC plant, get in touch with our TIAC Designers.