Comprehensive investigation on lighting and energy-saving performance of lighting/heating coupled tubular daylighting devices integrated with nanofluids

Feasible regulation of the solar visible and infrared spectrum is a promising technology for energy-efficient buildings. Our recently published work has proposed a lighting/heating coupled tubular daylighting devices (LH-TDDs) integrated with nanofluids to track the trade-off between indoor visible light gain and near-infrared shielding and demonstrated its excellent lighting/heating decoupling performance. To further evaluate the application potential of the LH-TDDs, the present work develops a comprehensive evaluation method that considers both lighting and energy-saving performance. In detail, the LH-TDDs system was investigated using both the numerical models and Energyplus software. The results on lighting performance demonstrate that the filtration of nanofluids hardly affects the lighting quality of LH-TDDS, but will instead enhance lighting uniformity and lessen glare risk. Meanwhile, the energy consumption simulations indicate that LH-TDDs achieve energy saving from three approaches, namely, lighting energy saving, thermal energy output, and air-conditioning energy-saving, and 100 ppm nanofluid can improve the total energy-saving amount by 43.6 % in Harbin, China. The findings of this paper can accelerate the application of LH-TDDs, and the evaluation system elaborated in this work may provide some useful clues for the assessment of other nanofluids-based transparent envelopes.