Cool Storage for Supplemental Cooling
In thermoelectric power generation, only about 40% of the energy in the fuel is converted into electricity. In other words, the power plant operates at about 40% efficiency. The remainder of the energy is converted to low-grade waste heat that must be removed to maintain the power plant’s efficiency. Most power plants use water from nearby rivers, lakes, or the ocean for cooling. The water may pass directly over tubes containing the plant’s heated condenser water, and then be returned, warmer, to the original source, or it may be evaporated to carry off the heat in water vapor. In areas with limited water or under drought conditions, dry-cooling systems use air to remove heat from the plant’s condenser water. However, present dry-cooling technology reduces the power plant’s efficiency and requires costly equipment. With water supplies becoming increasingly strained in many areas, economical dry-cooling approaches that do not reduce the efficiency of power plans are critically needed. Innovative methods to allow cooling below the daytime ambient air temperature and improve heat exchange between air and the plant’s recirculating condenser water will provide the keys to ensuring the continued efficiency of power generation while decreasing the burden on water supplies.
Project Innovation + Advantages:
Advanced Cooling Technologies (ACT) will work with Lehigh University, the University of Missouri, and Evapco, Inc. to design and build a novel cool storage system that will increase the efficiency of a plant’s dry-cooling system. During the day, the system will transfer waste heat from the plant’s heated condenser water via an array of heat pipes to a cool storage unit containing a phase-change material (PCM). The planned PCMs are salt hydrates that can be tailored to store and release large amounts of thermal energy, offering a way to store waste heat until it can be efficiently rejected. When temperatures are lower, such as at night, a novel system of self-agitated fins will be used to promote mixing and enhance heat transfer to air. The effectiveness of the fins will allow a reduction in the size of the storage media and the power required to operate it, both of which could lower costs for the system. Because the PCM materials are salts, their storage temperature can be tuned by changing the water content. Therefore, the storage system can potentially be customized to provide supplemental dry cooling for different climates, including regions with high ambient temperatures, such as the southwestern United States.
If successful, ACT and its partners will develop a supplemental cooling system for power plants that can facilitate dry cooling in hot climates without sacrificing power plant performance.
Power plants can maintain energy efficiency by using the team’s dry-cooling technology instead of water cooling when water use is restricted.
ACT’s storage system results in no net water consumption for cooling, and therefore eliminates the need to draw on local water resources.
By improving the performance of air cooling, ACT’s cool storage system reduces the capital costs of air cooling by 30%, while reducing the size of the system by 40%.