Analysis, evaluation and integration of modular natural illumination system using a rectangular Fresnel lens for high performance

Daylighting using natural illumination system (NILS) is gaining popularity due to transition to the renewable and non-conventional energy resources. In the proposed work, optomechanical design, numerical analysis, experimentation and integration of a modular Fresnel lens for NILS to effectively harness the sunlight is discussed. The modular and integrated design delivers uniform light at the receiving area of the daylight transportation system. This modular Fresnel lens is a combination of linear Fresnel lenses designed to offer a moderate concentration ratio to avoid hot spots. The distribution of solar radiation on the focal plane/entry section of the plastic optical fibre bundle (daylight transportation system) is simulated using the ray-trace technique for a lens system with a concentration ratio of 81. The irradiance distributions at the focal plane were found uniform with a radiometric and photometric transmission efficiency of 72.45% and 85.96%, respectively, for the lens element. The overall photometric transmission efficiency of the system with 10 m long plastic/acrylic optical fibre cable was found as 40.97%.