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Turbine Inlet Cooling Offers Power Generation Improvements and Can Help to Prevent Blackouts

The following is a September 2001 interview with Dharam V. Punwani, President of the Turbine Inlet Cooling Association, which was founded in 2001 to promote the effectiveness of gas turbine inlet cooling for enhancing power generation worldwide.

Mr. Punwani has more than 35 years of experience with power generation and natural gas technologies. He has authored or co-authored seven patents, more than 80 technical publications related to energy technologies, and is developing the first textbook on Gas Cooling Technologies and Economics.

Mr. Punwani can be reached at 630-983-0883 or dpunwani@avalonconsulting.com.

NOTE: This interview may be re-published. Please send notice of publication to: admin@turbineinletcooling.org.

Question: Why do rolling blackouts occur, and how can they be prevented?

Answer: Rolling blackouts occur when the demand for electric power exceeds its supply. Such situations usually take place when the weather becomes hot and power demand for air conditioning increases significantly. There are five alternatives for preventing blackouts in a region:

1. Reduce power demand by using higher efficiency electric air conditioners
2. Use other cooling technologies (absorption and engine-driven chillers) that require much less power than even the most efficient electric air conditioners
3. Buy more power in the open market
4. Build new power plants
5. Use turbine inlet cooling (TIC) to increase the output of the existing combustion (gas/oil) turbine-based power plants

Question: How does turbine inlet cooling make a combustion turbine system produce more power and improve its efficiency ?

Answer: Combustion turbines are great machines for producing electric power. They work by burning natural gas or a fuel oil with a fixed volumetric rate of compressed air. A turbine's power output is directly proportional to the mass rate of the compressed air that enters the system. When the weather gets hotter, the mass rate of the compressed air decreases because warmer/hotter air is lighter (lower density, i.e. for the same volume it weighs less), and therefore the turbine's power output decreases.

This one characteristic of combustion turbines is very unattractive for the power producers because they have less power to sell, just when the increase in outside temperature creates more power demand for air conditioning and the market price of power is also high.

Turbine inlet cooling involves reducing the temperature of the air used by the gas turbine in the combustion process. Cold air is more dense than warm air, and therefore cold air gives the gas turbine a production boost. Cooling inlet air to the compressor of a gas turbine system is a low-cost option for preventing the loss of output or even increasing gas turbine output in hot weather. When ambient temperature increases to 90F, gas turbine output drops. Cooling turbine inlet air to 50F increases output capacity by 15% to 40% over that at 90F, depending upon the turbine characteristics.

Question: What are the benefits of turbine inlet cooling over other options for increasing power supply, such as building new power plants?

Answer:

• TIC increases power output at much lower capital cost
  TIC increases power capacity at much less capital cost than installing an additional turbine.
• TIC systems can be put in place much faster than new equipment can be started up.
• TIC reduces NOx and other emissions
  Environmentally, TIC is much more friendly than building another power plant.

Question: Is the improvement really significant?

Answer: When the surrounding air temperature is 110F (for example in Phoenix, AZ), output capacity of a typical gas turbine drops to about 65% of its baseline capacity. Cooling the inlet air to 50F from 110F for such a turbine increases its capacity by over 60% of its capacity at 110F. Larger capacity industrial turbines are slightly less sensitive to inlet temperature, but the capacity improvement is still quite significant.

Question: If turbine inlet cooling offers such promise, why don't we hear more about it? Are power plant owners actually using this technology?

Answer: The reason we do not hear much about it is because there has been no concerted effort to publicize it. This is one of the reasons the Turbine Inlet Cooling Association (TICA), and its Web site at http://www.turbineinletcooling.org, have been established.

There many power plant users that are actually using TIC. No consolidated list of such users is currently available. TICA plans to establish a database of such plants. Some examples of the power plants using turbine inlet cooling are as follows:

1. Calpine Clear Lake Cogeneration, Inc., Pasadena, TX
2. Lincoln Electric Utility, Lincoln, Nebraska
3. SEI, San Diego, CA
4. Huntsman Chemicals, Houston, TX
5. Greenwood and Pleasant Hill stations of a Missouri electric utility
6. A utility's cogeneration plant in Gilroy, CA