Maximum Exergy Control of a Solar Thermal Plant Equipped with Direct Steam Collectors

Abstract

The performance of solar thermal power plants is strongly affected by the radiation intensity, which is subject to large variations depending on the weather conditions and on the time of the year. The control system of the solar thermal energy conversion plant must take into account such variable conditions, introducing correct thermodynamic relations pursuing the minimization of exergy destruction. The advantage of introducing direct-steam solar collectors with respect to the use of a separate heat transfer fluid in the primary circuit is also demonstrated. The model simulation predicts a performance improvement - compared to traditional control laws - ranging from 10 to 20% depending on the reference month.

Keywords

• solar thermal energy conversion, maximum- exergy control

References

1. Bejan, A., 1988, Advanced Engineering Thermodynamics, John Wiley & Sons, New York.
2. Bejan, A., Tsatsaronis, G., Moran, M., 1996, Thermal Design and Optimization, Wiley Interscience, New York.
3. Camacho, E., Berenguel, M., Rubio, F.R., 1997, Advanced Control of Solar Plants, Springer-Verlag, London.
4. Cirre, C.M., Berenguel, M., Valenzuela, L., Klempous, R., “Reference governor optimization and control of a distributed solar collector field”, European Journal of Operational Research, 2007, doi:10.1016/j.ejor.2007.05.056.
5. Duffie, J.A., Beckman, W.A., 1984, Solar Energy Thermal Processes, Wiley, New York.
6. Eck, M., Zarza, E., Eickhoff, M., Rheinlander, J., Valenzuela, M., 2003, Applied research concerning the direct steam generation in parabolic troughs, Solar Energy Vol. 74, N. 4, 341-351.
7. Manfrida, G., 1985, The Choice of the Optimal Working Point for Solar Collectors, Solar Energy, Vol. 34, N. 6.
8. Manfrida, G., Kawambwa, S., 1990, A Two-Phase Solar Collector Powering a Rankine Organic Cycle, World Renewable Energy Congress, Reading, U.K.

9. Manfrida, G., Kawambwa, S., 1991, Exergy control for a flat-plate Collector/Rankine Cycle Solar Power System, ASME J. of Solar Energy Engineering, Vol. 113, 89-93.
10. Manfrida, G., 2006, Miglioramento delle prestazioni di sistemi di conversione di energia solare termica mediante controllo a minimizzazione di distruzione di energia , (in 148 Int. J. of Thermodynamics, Vol. 11 (No. 3)
11. Int. J. of Thermodynamics, Vol. 11 (No. 3) 149 Italian),Atti 61mo Congresso Nazionale ATI, Perugia.
12. Mills, D., 2004, Advances in solar thermal electricity technology, Solar Energy 76, pp. 19- 31.
13. Odeh,. S. D., “Unified model of solar thermal electric generation systems”, Renewable Energy 28, 2003, 755-767.
14. SOLEL, 2007, “UVAC Clean Power Generation”, Technical brochure, www.solel.com. The Potential of Solar Heat for Industrial Processes, (POSHIP) Final Report, European Community Project NNE5-1999-0308.
15. Valenzuela, M., Zarza, E., Berenguel, M., Camacho, E.F., 2005, Control concepts for direct steam generation in parabolic troughs, Solar Energy 78, 301-311.
16. Zarza, E., Hennecke, K., Direct Steam Generation in parabolic troughs (DISS), 10th Solar aces International Symposium on Solar Thermal Concentrating Technologies, Australia, 2000, 65-71.