Performance Prediction and Assessment of Energy Conservation Potential for a Light Pipe System in Indian Composite Climate of New Delhi

Light pipes are popularly used for transporting outdoor sunlight into deep spaces of the building, and hence, use of artificial lighting could be substantially reduced. Performance prediction of a light pipe is an essential step before its use in buildings, so that energy saving potential of the light pipe could be quantified. This paper deals with experimental validation of three existing semi-empirical models for light pipes with different aspect ratios, installed on a windowless test room, at IIT Delhi, New Delhi. Two new semi-empirical models based on the existing correlations are developed. The new model found to perform better with mean bias error (MBE) and root-mean-squared error (MSE) of 0.076 and 0.01, respectively. The better performing new model is used for the evaluation of hourly internal illuminance by the light pipe in a typical meteorological year (TMY) in New Delhi. From hourly internal illuminance in a typical meteorological year, the energy saving potential and CO₂ mitigation potential of light pipe system for the test room are evaluated. Monthly average energy saving potentials of the light pipe-fluorescent tube light system are found to be 50% for continuous dimming control and 38% for three-step on–off control. Results show that the light pipe-fluorescent tube light system, with different lighting controls, could reduce CO₂ emissions to 15–50%.