This paper introduces a fuzzy logic-based circadian lighting control system using flexibility of Light-Emitting Diode (LED) lighting technology to synchronise artificial lighting with circadian (natural) lighting Correlated Colour Temperature (CCT) characteristics. Besides for vision acuity, the Non-Imaging Forming effects of lighting affect human circadian rhythms. Past works in spectrally tuning CCT or Spectral Power Distribution of lighting have used conventional Proportional-Integral-Derivative (PID) control system architecture, where the modelling process of system transfer functions was mathematically complex, especially for nonlinear systems. A methodology of regulating lighting CCT is employed in a 7×5 fuzzy logic rules matrix in a Fuzzy Logic Controller (FLC) system, to closely replicate natural lighting CCT characteristics for indoor lighting. A reference lookup table was devised to store desired CCT values arbitrarily with respect to time mark in a day, which acts as an outdoor circadian stimulus and guides the FLC. The FLC compensates for the lack of CCT in lighting space. Simulation results show acceptable CCT output values conforming to circadian lighting parameters at a time in a day compared to the lookup table targets. Deviation from blackbody curve was within ±0.003 using CCT Duv checking. The system did not produce an overshoot (0.0%) with a steady state (zero error) reached after the fourth iteration. Also, rise time was calculated to be 1 iteration. This approach could be further enhanced to cater for additional custom needs in many built environments. Future works may consider connecting more sensors to capture real-time outdoor CCT values for practical regulation.
In the field of lighting technology, the choice of lighting has shifted from conventional incandescent and fluorescent to LED (Light Emitting Dode) lighting. Many businesses have yet to take full advantage of LED lighting technologies to address visual comfort problems for occupants. The current focus of installations and retrofitting jobs is only on dollar returns and energy-saving measures. By defining a range of vulnerabilities and discrepancies, this paper reviews the typical criteria affecting occupant visual comfort and shifts gear into those that are fundamental to healthcare setup. Issues such as the importance of daylight introduction into hospital wards and the benefits of choosing correct correlated colour temperature are discussed, among others discomforts. LED lighting technology has advanced immensely by offering flexibility to build a lighting system that meets the environmental requirements of the end-user. Lighting technology and approach are shifting to a new paradigm by focusing not only on vision but also human psychophysical wellbeing in interior spaces. A balance must exist between energy efficiency and visual comfort factors.
Building owners are transitioning towards a smart lighting solution for illumination purposes. LED (Light Emitting Diode) lighting application has become a norm given its high efficacy and energy efficiencies. This paper presents an approach to monitor the percent flicker conformance of interior building lighting to international standards. The focus is on flickers induced by LED lightings. This experiment utilises a TCS34725 RGB (red, green, blue) colour sensor to measure the flicker parameters of interior lighting spaces. Light-sensitive photodiodes in the sensor detect changes in lighting intensity, and output digitised values. A Raspberry Pi4 minicomputer processes the data measured for comparison to several standards. Non-conformance is reported to building owners to take corrective actions and minimise flicker discomfort exposure to building occupants. A flicker risk level factor is determined to gauge the severity when flickers are present. This method may be used to replace luminaires or fix flickering lighting issues in buildings. The results show that the monitoring system is functional. The proposed measurement and data processing method can be incorporated into any smart building hub for automation and building performance analysis. The method may also be used to measure non-LED lighting flickers.
This paper presents a performance analysis of the potential study in complementing grid utility supply with the renewable energy system. A general-purpose building consisting of office and laboratory facility has been chosen as a test case with a hybrid system of fuel cell and solar photovoltaic cells installed in addition to the existing grid power supply. HOMER simulation software was used to run the simulations, and the results showed that only the photovoltaic system is more economical to be integrated into the system. Cost-saving from the feed-in-tariff point of view was observed spanning over several years after the initial capital cost was returned.
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