LINE-FOCUS CONCENTRATING SOLAR THERMAL TECHNOLOGIES UNIT

Pressurized gas as working fluid for parabolic trough collectors


Participants: CIEMAT, Universidad Politécnica de Madrid, Abengoa Solar NT, ACCIONA, ASSYCE
Financed by: CIEMAT
Duration: December 2005 – December 2012
Motivation:
Presently the technology of parabolic trough collectors is the most commercially developed for solar thermal power plants, with more than 4,5 million square meters of collectors in routine operation by the end of 2010, with a nominal power higher than 900 MWe in the same period. Besides its commercial maturity, this technology must seek ways to cost reduction and efficiency enhancement, so it becomes more competitive with conventional power plants. One of the possible options to cost reduction and efficiency enhancement is to find new working fluids for the solar collectors used in these power plants. Up to now all commercial solar power plants use thermal oil as working fluid, but this oil has clear disadvantages. Some disadvantages associated to thermal oil are: environmental risk in case of leakage, fire risk and maximum temperature limitation in the solar field. To avoid this problems it is necessary to replace the current thermal oil, three possible substitutes are proposed: water/steam, molten salts or pressurized gas. To gather which of these candidates is the best option, it is necessary to study them under real operation conditions.
Objectives:
The experimental study of the use of pressurized gas as working fluid for parabolic trough collectors, assessing their performance under different real operation conditions and analyzing the advantages and disadvantages versus the thermal oil currently used and other innovative possible working fluids. The achievement of this final target arises from two partial objectives:

  1. design and construction at PSA of a test-loop to carry out the experimental study of new working fluids for parabolic trough collectors
  2. experimental study under real solar conditions using different pressurized gases as working fluid in the test-loop erected at PSA.

CIEMAT activities within this Project were proposed by Prof. Carlo Rubbia, Nobel Prize in Physics 1984.

Layout of the new configuration of the test-loop installed at PSA for the experimental study of pressurized gasses as working fluid in parabolic trough collectors

Selected publications:

  • Muñoz-Anton J, Biencinto M, Zarza E, Díez LE. Theoretical basis and experimental facility for parabolic trough collectors at high temperature using gas as heat transfer fluid. Applied Energy 2014; 135:373-381. http://dx.doi.org/10.1016/j.apenergy.2014.08.099
  • Biencinto M, Gonzalez L, Zarza E, Díez LE, Muñoz-Anton J. Performance model and annual yield comparison of parabolic-trough solar thermal power plants with either nitrogen or synthetic oil as heat transfer fluid. Energy Conversion and Management 2014; 87:238-249. http://dx.doi.org/10.1016/j.enconman.2014.07.017
  • Muñoz J, Zarza E, Díez LE, Martínez-Val JM, López C, Gavela R, Abanades A, Montes MJ. The New Technology of Gas-Cooled Trough Collectors. Proceedings of the International Symposium SolarPACES 2011, Granada, Spain, September 21-24, 2011.