Evaluation of integrated daylighting and electric lighting design projects: Lessons learned from international case studies

This article presents and discusses the lessons learned from the monitoring of 25 integrated daylighting and electric lighting international case study projects. The case studies consist of real occupied buildings that have been monitored as part of the International Energy Agency (IEA) SHC Task 61/EBC Annex 77 Programme. The general goal of the case studies was to balance lighting energy use with occupants’ visual and non-visual requirements. This was achieved using innovative solutions for daylighting and electric lighting with advanced controls, but also implementing simple and out-of-the-box strategies. The findings suggest that energy demands for lighting can significantly be reduced by combining sensible daylight provision, efficient lighting sources, and advances in controls. Yet, the effective achievement of project goals requires adequate monitoring, fine-tuning, and verification. The findings also suggest that the adoption of “integrative” lighting – that is, lighting systems that address both visual and non-visual responses – is getting increasingly popular. Catering to non-visual requirements will likely drive further innovation in lighting technology. Currently, there is limited investment available for developing daylighting systems for integrative lighting, and the current related electric strategies often come at the risk of energy rebound effects. Overall, providing daylighting and understanding user requirements are fundamental steps towards achieving quality projects, with potential benefits beyond saving energy

Design and development of a low-cost angular sky luminance measurement system

Energy efficient building design requires simulated assessment of overall performance through reliable models, taking into account the daylight variations along with other significant parameters such as ventilation, plug loads and occupant behaviour. A robust indoor daylight model applicable to locations across the globe needs to incorporate local variations of sky luminance on a spatial and temporal basis, and needs an affordable system for dynamic angular daylight measurement to be used as part of a wider distributed network. In the present work, a low-cost prototype based on Light Dependent Resistors for measurement of angular daylight luminance distribution is developed and analyzed. This device was used to capture the angular analog data for 221 sky segments (20 azimuthal x 11 altitudinal segments and Zenith). The analog data was further converted to luminance data, and the visualized data was compared with sky-dome photographs and also with simulated polar daylight maps for a few Commission International de l'Eclairage (CIE) skies. The repeatability of the experiment was assessed by comparing the luminance data for selected sky segments over multiple time-segments for consecutive days. Measured data was found to be an acceptable fit with the CIE-models over various time segments, validating the prototype

Evaluation of dynamic sky-type using novel angular sky luminance measurement system

Standard sky-types of the established Commission International de l'Eclairage (CIE) sky-models are employed for generating sky-luminance distribution datasets in most building daylight simulation packages, which are used for predicting indoor illuminance distribution. However, sky-type can vary on diurnal and seasonal basis; and there is a need for identifying closest sky-type at different time-points for better indoor illuminance predictions. This paper aims at recommending closest sky-model for measured angular sky-luminance distribution sets through comparison with established CIE standard skies. A novel design of sky-luminance measurement device using calibrated Light Dependent Resistors is proposed to measure incident illuminance from 265 discrete sky positions every 5 min. Statistical analysis is performed on 143,100 distinct data-points corresponding to 540 representative datasets measured across 5-month period at Mumbai, and the closest CIE sky-type for various hours is recommended based on frequency of occurrence. A range of 9 sky-types of the CIE sky-model was determined as closest model sky-set, with sky-types 2, 4, 5, 6, 7, 8, 10, 11 and 13 assessed as closest sky-type for different time-points across the measured datasets. CIE sky-type 8 is identified dominating over 50% of measured datasets - 51.6% in November, 53.6% in January, 52.6% in March and 71.5% in April. Measured sky distribution is observed to generally follow trend of overcast to intermediate to clear sky-types in morning hours, and opposite in evening hours. This approach of recommending closest sky-type as simulation input as against using generic sky-types can enhance the accuracy of building indoor daylight predictions