Concentrating Solar Thermal Power

Parabolic-Trough Collectors ............................................................................... 1289 42.5Linear Fresnel Re¡ectors................................................................................................. 1296 42.5.1Historical Evolution of Linear Fresnel Re¡ector Systems .............................. 1296 42.5.2Future Technology Development and Performance Trends ......................... 1298 42.6Central-Receiver Solar Thermal Power Plants ............................................................. 1298 42.6.1Technology Description ...................................................................................... 1300 42.6.1.1Heliostat and Collector Field Technology ......................................... 1301 42.6.2Solar Receiver ....................................................................................................... 1309 42.6.2.1Tubular Receivers ...................................................................................1314 42.6.2.2Volumetric Receivers ............................................................................ 1316 42.6.3Experience in Central Receiver Systems ........................................................... 1321 42.6.3.1Water-Steam Plants: The PS10 Project ............................................... 1322 42.6.3.2Molten-Salt Systems: Solar Two and Gemasolar .............................. 1326 Solar energy has a high exergetic value since it originates from processes occurring at the sun’s surface at ablackbody equivalent temperature of approximately 5777 K. Because of this, more than 93% of the energy may be theoretically converted to mechanical work by thermodynamic cycles (Winter et al., 1991) or to Gibbs free energy of chemicals by solarized chemical reactions (Kodama, 2003), including promising hydrogen production processes (Romero and Steinfeld, 2012). According to thermodynamics and Planck’s equation,the conversion of solar heat to mechanical work or Gibbs free energy is limited by the Carnot efŽciency, and therefore to achieve maximum conversion rates, the energy should be transferred to a thermal ¡uid, or reactants, at temperatures close to that of the sun.