-- This project is inactive --
The University of South Florida, under the Baseload CSP FOA, developed a thermal energy storage system based on encapsulated phase change materials (PCM) that meets the utility-scale baseload CSP plant requirements at significantly lower system costs.
Approach
Previous thermal energy storage (TES) concepts cost about $27 per kilowatt hour thermal (kWhth). The University of South Florida proposed a TES system concept that could potentially reduce the cost to as low as $3.54/kWhth to make it competitive with fossil fuels and allow for a capacity factor increase to 75% or greater. Specific objectives included:
- Developing an encapsulated PCM for thermal energy storage in the temperature range of 300°–450°C with a cyclic performance (charge/discharge heat transfer) capability of at least 1,000 cycles
- Designing a one-tank storage system using spherical (or other shape) PCM capsules immersed in synthetic oil with an integrated heat exchanger for charge/discharge testing.
Proposed TES system with packed-bed configuration.
Innovation
The University of South Florida's project employed a latent heat storage system that used a phase change material (salt) encapsulated by a shell (metal) to overcome the barrier of low thermal conductivity. Capsules were placed in direct contact with the heat transfer fluid to achieve the highest heat transfer rates. There were two major challenges to the success of this concept:
- Forming porous macrospheres of the PCM material at optimum size and pore volume to account for the volume change from solid to liquid phase
- Encapsulating the macrospheres of PCM in a higher melting temperature material, preferably a metal, at low cost.
The research team also developed a two-dimensional numerical model to look at diffusion-natural, convection controlled heat transfer in an encapsulated sphere.
Conclusion
This project successfully developed encapsulated PCM with provision for expansion/contraction during melting/freezing:
- Characterized the PCMs of interest
- Tested capsules for thermal cycling
- Exceeded the 1st Phase milestone of 50 cycles
- Successfully completed 200 cycles (continuing)
- Developed a numerical model for melting/solidification
- Developed a manufacturing plan for capsules
- Cost estimate of a TES system based on the developed PCM capsules – $14/kWhth
- Preliminary discussions with companies on further testing and development for commercialization
Final Report
Goswami, D. Yogi. Development and Demonstration of an Innovative Thermal Energy Storage System for Baseload Power Generation. No DE-EE0003590, 2012. doi:10.2172/1049940.
Publications, Patents, and Awards
- S. Kuravi, J. Trahan, M.M. Rahman, D.Y. Goswami, and E.K. Stefanakos, "Analysis of Transient Heat Transfer in a Thermal Energy Storage Module for Baseload Solar Power," Paper No. IMECE2010-40773, in Proceedings of the ASME 2010 International Mechanical Engineering Congress & Exposition, Vancouver, BC, Canada, November 12-18, 2010, ISBN 978-0-7918-3891-4.
- A. Ramos, C.A. Asselineau, J. Gonzalez-Aguilar, M.M. Rahman, M. Romero, D.Y. Goswami, and E.K. Stefanakos, "Transient Numerical Analysis of PCM-Contained Spherical Capsules for Heat Storage in Concentrating Solar Power Plants," in Proceedings of the 12th International Conference on Energy Storage (Innostock 2012), Lleida, Spain, May 16-19, 2012.
- J. Trahan, S. Kuravi, D.Y. Goswami, M.M. Rahman, E.K. Stefanakos, "Thermal Characterization of High Temperature Inorganic Phase Change Materials for Thermal Energy Storage Applications," Paper No. ESFuelCell2012-91475, in Proceedings of the ASME 2012 6th International Conference of Energy Sustainability, San Diego, CA, July 23-26, 2012.
- S. Pendyala, P. Sridharan, S. Kuravi, C.K. Jotshi, M.K. Ram, M. Rahman, E.K. Stefanakos, and D.Y. Goswami, "Macroencapsulation of Sodium Nitrate for Thermal Energy Storage in Solar Thermal Power," Paper No. ESFuelCell2012-91447, in Proceedings of the ASME 2012 6th International Conference of Energy Sustainability, San Diego, CA, July 23-26, 2012.
- A. Ramos, M.M. Rahman, D.Y. Goswami, and E.K. Stefanakos, "Parametric Investigation of the Melting and Solidification Process in an Encapsulated Spherical Container," Paper No. ESFuelCell2012-91435, in Proceedings of the ASME 2012 6th International Conference of Energy Sustainability, San Diego, CA, July 23-26, 2012.
- Ram, Manoj Kumar, et al. "Method of encapsulating a phase change material with a metal oxide." U.S. Patent Application No. 14/159,874.
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