# Novel Thermal Energy Storage Systems for Concentrating Solar Power

The University of Connecticut, under the Thermal Storage FOA, is developing innovative heat transfer devices and methodologies for novel thermal energy storage (TES) systems for CSP involving phase change materials (PCMs).

## Approach

Specific objectives include embedding thermosyphons and/or heat pipes (TS/HPs) within appropriate PCMs to significantly reduce thermal resistances within the TES system of a large-scale CSP plant and, in turn, improve performance of the plant. The expected outcome of the research is generation of the necessary fundamental knowledge to enable full-scale design of a system that reduces the LCOE and increases round-trip efficiency of CSP. Manufacture of the proposed heat transfer devices presents a novel opportunity for economic development.

## Innovation

This work utilizes embedded thermosyphons or heat pipes in the PCM to reduce the thermal resistance between the location where phase change occurs and the working fluid of the power cycle. Either thermosyphons or heat pipes can:

- Provide an effective thermal conductivity that is up to 90 times that of copper
- Transfer large amounts of energy nearly isothermally
- Be custom-tailored for performance by carefully selecting the TS/HP working fluid and its operating pressure, as well as the wall material
- Be fabricated in a wide variety of shapes.

The intended outcome of this research is the development of a PCM storage system with the capability of achieving an energy cost of $15/kWth. This work aims to prove or disprove the ability of heat pipes to enhance heat transfer in PCM TES systems.

## Publications, Patents, and Awards

- S. Wang, A. Faghri, and T.L. Bergman, "A Comprehensive Numerical Model for the Melting With Natural Convection,"
*International Journal of Heat and Mass Transfer*, Vol. 53, Nos. 9-10, pp. 1986-2000, 2010. - H. Shabgard, T.L. Bergman, N. Sharifi, and A. Faghri, "High Temperature Heat Pipe Thermal Energy Storage,"
*International Journal of Heat and Mass Transfer*, Vol. 53, Nos. 15-16, pp. 2979-2988, 2010. - S. Wang, A. Faghri, and T.L. Bergman, "Numerical Modeling of Alternative Melting and Solidification,"
*Numerical Heat Transfer*, Part B Vol. 58, No. 6, pp. 393-418, 2010. - C.W. Robak, T.L. Bergman, and A. Faghri, "Enhancement of Latent Heat Energy Storage Using Embedded Heat Pipes,"
*International Journal of Heat and Mass Transfer*, Vol. 54, Nos. 15-16, pp. 3476-3484, 2011. - M. Aghvami and A. Faghri, "Analysis of Flat Heat Pipes with Various Heating and Cooling Configurations,"
*Applied Thermal Engineering*, Vol. 31, Nos. 14-15, pp. 2645-2655, 2011. - C.W. Robak, T.L. Bergman, and A. Faghri, "Economic Evaluation of Latent Heat Thermal Energy Storage Using Embedded Thermosyphons for Concentrating Solar Power Applications,"
*Solar Energy,*Vol. 85, No. 10, pp. 2461-2473, 2011. - N. Sharifi, T.L. Bergman, and A. Faghri, "Enhancement of PCM Melting in Enclosures With Horizontally-Finned Internal Surfaces,"
*International Journal of Heat and Mass Transfer*, Vol. 54, Nos. 19-20, pp. 4182-4192, 2011. - H. Shabgard and A. Faghri, "Performance Characteristics of Cylindrical Heat Pipes With Multiple Heat Sources,"
*Applied Thermal Engineering*, Vol. 31, No. 16, pp. 3410-3419, 2011. - H. Shabgard, C.W. Robak, T.L. Bergman, and A. Faghri, "Heat Transfer and Exergy Analysis of Cascaded Latent Heat Thermal Energy Storage With Gravity-Assisted Heat Pipes for Concentrating Solar Power Applications,"
*Solar Energy*, Vol. 86, No. 3, pp. 816-830, 2012. - N. Sharifi, S. Wang, T.L. Bergman, and A. Faghri, "Heat Pipe-Assisted Melting of a Phase Change Material,"
*International Journal of Heat and Mass Transfer*, Vol. 55, Nos. 13-14, pp. 3458–3469, 2012. - K. Nithyanandam and R. Pitchumani, "Analysis and Design of Dye-Sensitized Solar Cell,"
*Solar Energy*, Vol. 86, No. 1, pp. 351-368, 2012. - K. Nithyanandam and R. Pitchumani, "Analysis and Optimization of a Latent Thermal Energy Storage System With Embedded Heat Pipes,"
*International Journal of Heat and Mass Transfer*, Vol. 54, Nos. 21-22, pp. 4596-4610, 2011. - K. Nithyanandam and R. Pitchumani, "Computational Modeling of Dynamic Response of a Latent Thermal Energy Storage System With Embedded Heat Pipes," Paper ES2011-54501, in
*Proceedings of the 5th International Conference on Energy Sustainability*; Washington, DC, August 7-10, 2011, pp. 753-762, ISBN: 978-0-7918-5468-6. - K. Nithyanandam and R. Pitchumani, "Computational Modeling of Latent Heat Thermal Energy Storage System With Integral Heat Pipes," Paper IMECE2010-38682, in
*Proceedings of the ASME International Mechanical Engineering Congress and Exposition*, Vancouver, BC, November 12-18, 2010, pp. 369-376, ISBN: 978-0-7918-4429-8. - K. Nithyanandam and R. Pitchumani, "Analysis and Design of Dye-Sensitized Solar Cells," Paper IHTC14-23101, in
*Proceedings of the 14th International Heat Transfer Conference*, Washington, DC, August 8-13, 2010, pp. 565-572, ISBN: 978-0-7918-4942-2.

Quarterly Progress Reports

Learn about other DOE competitive awards for concentrating solar power research that are in progress.