A collaboration between the University of North Carolina at Charlotte and Lehigh University recently completed a project, funded by the U.S. Department of Energy (award number DE-FE 0031886). The project was aimed at improving dry cooling technology for power plants where, according to the second law of thermodynamics, heat needs to be rejected to the environment to generate mechanical work (power). Dry cooling is an important heat-rejection technology poised to mitigate the energy-water nexus associated with power plants. The results of this project are applicable to fossil, nuclear, and concentrated solar power (CSP) power plants.
The project developed an innovative technology based on a Cold Thermal Energy Storage (CTES) concept, where low-temperature (enthalpy) heat is stored in an energy storage media during the nighttime, when temperature of the ambient air is low. The stored low-enthalpy heat is used during the hot period of the day to reduce temperature of the air using for dry cooling. The modular CTES concept is also applicable to the simple and combined Brayton power cycles, and for the industrial, commercial, and residential applications.
Due to the large amount of low-enthalpy heat that needs to be stored for a large power plant, a low-cost heat storage medium is needed. A storage media based on pervious concrete and commercial-grade, low-cost phase changing material (PCM) was engineered in the CTES concept. Several heat storage module designs were developed and tested at the laboratory and prototype scales. Experimental data were compared to the results of numerical simulations obtained using numerical models developed for modeling of fluid flow, heat transfer, and phase change. The project results have demonstrated validity of the CTES concept and performance of the developed heat storage materials and concepts.
The 3.5-year project was led by faculty and researchers from both universities who were assisted by graduate students. The students were trained in the disciplines of material development, power plant modeling, numerical analysis, rig design, and conduction of experiments and data reduction. Four graduate students obtained their Ph.D. degrees from this project. Results from this project have been published in different technical journals. A professional engineering company, Worley (formerly known as Worley-Parsons), developed a preliminary design of the CTESS system for a 650 MW feference power plant selected for the project and performed techno-economic analysis (TEA) using a Pre-FEED approach.