Many state and federal programs exist today to help offset the cost of developing and installing technologies that promote energy efficiency. These incentive programs are helping drive both new technology development and optimization of existing technologies. Recent advances and existing methods in turbine inlet cooling techniques are prime candidates for potential consideration for funding incentives in today’s climate of promoting energy efficiency.
As an example, the American Recovery Reinvestment Act of 2009 has provided $16.8 billion for the Office of Energy Efficiency and Renewable Energy (EERE) programs and initiatives. Numerous state incentive programs also are available and will be addressed later as part of this discussion.
- The Industrial Technologies Program (ITP), a division of the Office of Energy Efficiency, partners with industry to save energy and money, increase productivity and reduce environmental impacts through the following strategies:
- Sponsors research, development and demonstration of industry-specific and
crosscutting technologies to reduce energy and carbon intensityAdvertisement - Conducts technology delivery activities to help plants access today’s technology and management practices
- Promotes a corporate culture of energy efficiency and carbon management within industry
The ITP has embraced a goal to drive a 25 percent reduction in industrial energy intensity by 2017, guided by the Energy Policy Act of 2005. A review of available methods for turbine inlet cooling will demonstrate why this technology is a strong candidate for available incentive funding.
Turbine inlet cooling provides a means to reduce the impact of a turbine’s power loss associated with a rise in ambient temperature or due to locations at elevation. The sensitivity to inlet air density is a key factor in output power from the turbine. The gas turbine is a mass flow machine that has a volumetrically limited intake. Therefore, the available power is directly related to the density of the inlet air.
Currently available technologies that can be used to overcome the loss of available power at higher ambient temperatures include:
- Evaporative cooling
- Indirect evaporative cooling
- Mechanical chilling
- Hybrid indirect evaporative cooling (used in conjunction with supplemental chilling)
Each of these methods offers a solution to increasing available power. In addition, by delivering cooler and more dense air, the engine efficiency, or heat rate, also improves.
Available methods for turbine inlet cooling include:
- Direct Evaporative (Figure 1, process A–B): In this process, air is typically passed through a wetted media. This type of media offers a large surface area and a low pressure loss. These systems offer the ability to reduce the temperature from approximately 70 percent to 95 percent of the difference between the entering dry bulb and wet bulb temperatures. This process usually makes use of treated water on a case basis, as required by some turbine OEM water quality guidelines. Direct evaporative units also can often be added to an existing installation.
- Fogging (Figure 1, process A–C): This is another direct evaporative approach where de-ionized water is used to produce a fine mist. In this process, absolutely pure water is used to prevent any minerals from being ingested into the engine.
- Single Stage Indirect/Direct Evaporative Cooling (Figure 1, process A–D–E): In this process the air going to the engine is first cooled in a heat exchanger, where the evaporation of water takes place in a secondary air stream. The secondary air stream is used to extract heat from the primary inlet air stream, while not adding moisture to the primary air stream (it is a low energy process of refrigeration).
