The TROF (tower reflector with optical fibers): A new degree of freedom for solar energy systems

The integration of optical fibers into solar energy systems requires a trad e-off between the cost, attenuation, and a limited flux carrying capability (due to limited numerical aperture) on one hand, and the flexibility in li ght distribution on the other hand. This paper presents a novel approach th at minimizes the length of fibers in the system while fully utilizing me fl exibility advantage. Optical fibers have been steadily improving and their cost has been declining as a result of the proliferation of their use in co mmunication, and more recently in the lighting industry. The use of fibers in concentrating solar thermal systems has potential advantages of providin g unprecedented flexibility in the final concentration and the receiver des ign. A central receiver system based on the tower reflector with optical fi bers (TROF) is presented as a case study in a comparison between convention al concepts of solar thermal power generation, and new concepts employing o ptical fibers. Two new approaches to thermal conversion utilizing the flexi bility of a fiber-based system, non-isothermal high-temperature receivers a nd distributed receivers, are presented. An approximate performance and cos t analysis that assumes mass-produced solar-optimized fibers is presented. The effects of system size and several fiber types are discussed. The resul ts show that the use of current optical fibers may become competitive for s olar-driven electricity generation systems under optimistic assumptions. Th e analysis points to research and development directions that could lead to cost-effective TROF and other optical fiber-based systems in the future. ( C) 2000 Elsevier Science Ltd. All rights reserved.