Experimental study of direct transfer of concentrated solar radiation through optical fibres to high temperature thermal applications

Abstract

Employing optical fibres for transferring concentrated radiation from solar concentrators has potential advantages in terms of transmission energy efficiency, technical feasibility and cost-effectiveness compared to a conventional heat transfer system employing heat exchangers and a heat transfer fluid. The basic investigated system comprised a broadband source, collimator lens, objective lens and optical fibre as the carrier of energy to the receiver. The relationship between transmission and length of fibre is studied via simulation using the ray tracing model, LightTools®. Two different sources were defined in the system setup including a white light source and the solar simulator with similar spectral distribution as solar spectrum. The effects on transmission of varying the hydroxyl content, and the core size of the fibres are also investigated experimentally. The experimental results are then compared with simulations. The initial results indicate that the selected low OH unjacketed bulk fibre with NA=0.22 is capable of transmitting approximately 92% of the concentrated solar energy over lengths up to 10 m with less loss compared to conventional methods for direct transferring of concentrated solar radiation.

Bright ideas for the future of industrial heating

“…4 The nanoparticles are multiwalled carbon nanotubes functionalized for high-temperature stability in heat transfer oils. 4,5 The project has created several promising proof-of-concept devices, [6][7][8][9][10][11] including a full-size prototype that incorporates both concentration and volumetric absorbers (see Figure 1). This system consists of a two-stage optical concentrator: a linear Fresnel lens (primary) and a compound parabolic concentrator (secondary).…”

Air-Clad Holmium-Doped Silica Fiber Laser

“…For shorter wavelengths these fibers typically use low index polymers for their outer-cladding. However, these polymers display nonnegligible absorption at 1.9 µm [12] leading to a significant drop in device efficiency and limited power scaling because these polymers have a relatively low thermal failure limit compared to silica. For this reason there has been significant interest in alternative outer-cladding structures for high power ytterbium fiber lasers [13], [14].…”