Ciji Pearl Kurian

Robust control and optimisation of energy consumption in daylight—artificial light integrated schemes

Energy efficiency strategies based on daylight—artificial light integrated schemes have proved to be efficient by many researchers worldwide. But much larger energy savings with the benefit of visual and thermal comfort can be achieved when systems integration strategies are competently designed. They require a high level of expertise and familiarity with new design techniques. This study describes the results of three computational models suitable for the optimum integration of visual comfort, thermal comfort, and energy consumption in schemes where daylight and artificial light are integrated. This mainly involves: (i) a system identification approach in lighting control strategy, (ii) a fuzzy logic based controller to reduce glare, increase uniformity and thermal comfort, and (iii) an adaptive predictive control scheme for the dimming of artificial light. In addition to the above models the scheme must take account of occupancy and user wishes. The anticipated synergetic effects of the computational models have been validated using climate data. A SIMULINK environment is established for the real time control and analysis of daylight—artificial light integrated schemes. Overall, the schemes maximise energy cost saving while optimizing the performance and the quality of the visual environment.

An adaptive neuro-fuzzy model for the prediction and control of light in integrated lighting schemes

Advanced lighting simulation tools as well as computationally intelligent systems present the possibility of using a model based on computation as a means of controlling lighting on the visual task. Lighting control has now become an essential element of good design and an integral part of energy management programmes. This paper presents a novel computational model suitable for the adaptive predictive control of artificial light in accordance with the variation of daylight. Simulated data and an adaptive neuro-fuzzy inference system are incorporated into the model. The software package Radiance is used to carry out the simulation. In this process, the role of a simulator is considered as the source of the system knowledge by which a supervised learner, implemented in adaptive neuro-fuzzy inference system is trained for faster predictions. The goal of this paper is to make use of the benefits of the hybridization between simulation and machine learning for the purpose of light control.

Integrated design and real-time implementation of an adaptive, predictive light controller

Daylight–electric light integrated schemes encompassing soft computing models have been perceived as a lucrative option for lighting energy conservation. This paper exploits the quintessence of design and real-time implementation of an adaptive predictive control strategy for robust control of a daylight–electric light integrated scheme. To elicit daylight variations, occupancy detection and user preferences an online self-adaptive, predictive control algorithm is structured for real-time control of electric lights and window blinds. The adaptive, predictive model entails integration of an online, adaptive daylight illuminance predictor in conjunction with an electric light intensity control algorithm for interior illuminance regulation and a fuzzy-logic based window blind control algorithm to eliminate glare and solar heat gain. The control algorithm modelled with real-time sensor information administers an online process of identification, prediction and parameter adaptation. The prototype controller is successfully implemented in a test chamber. A real-time user-friendly simulator provides an online visualisation of illuminance performance indicators and control of the process. The anticipated synergetic effects of the online control algorithm validated in the test chamber highlights the benefits of the scheme in terms of glare control, illuminance uniformity and energy efficiency.

Application of accelerated life testing principles to project long term lumen maintenance of LED luminaires

This work presents our effort to predict the long term reliability of LED arrays using the application of accelerated life testing principles. Assessment of long term reliability and performance of LED arrays is a testing exercise but it is also vital for successful acceptance of Solid State Lighting (SSL) systems. The objective of this work is to analyze IESNA LM-80 test data obtained from the LED manufacturers to study how failure is accelerated by stress and fit an acceleration model to the data. This acceleration model can be used to accurately project the reliability of the LED arrays under normal operating conditions. The methodology was to apply statistical analysis to LM-80 test data and obtain accelerated models for life-stress relationships and life-time distributions. The Arrhenius-Weibull, Generalised Eyring-Weibull and Inverse Power-Weibull models were obtained and were compared for their effectiveness in to predicting the reliability of LED arrays.

Commissioning of camera calibration factor for luminance measurement

Use of HDR (High Dynamic Range) images for critical luminance studies is an established fact now. Luminance measurement has to be done using a camera which is calibrated. The calibration factor, relating the luminance measured from the HDR images and luminance measured using a device, say a luminance meter, can be calculated using several methods. At the outset of launching new direction for general lighting practice using digital camera and also with the increased importance of lighting controls in interior and street lighting applications, there is a need to derive simplified algorithms for luminance and illuminance measurements using camera. Many researchers all over the globe are working in this direction, however, this paper describes a simplified approach for obtaining the calibration factor.

Measurement of junction temperature of light-emitting diodes in a luminaire

There are vast numbers of light-emitting diode (LED) luminaires to choose from, but not all LED luminaires perform reliably. More than half of the input electrical power to a LED luminaire is wasted in the form of heat. Heat management is the one of the most critical issues faced by LED luminaire designers. The long term reliability of a LED luminaire is mainly dependent on the junction temperature of the LEDs. Hence, accurate junction temperature information during luminaire operation is critical for monitoring and assessing the health of the luminaire. In practice, it is extremely difficult to measure the junction temperature of LEDs in modern day luminaires. With the optical system and heat sink surrounding the tiny LED, measurement of junction temperature with direct methods like infrared cameras and thermocouples becomes more complex. This paper explores the possibility of monitoring and measuring the junction temperature of LEDs in a luminaire by making use of the strong correlation between the forward voltage drop at the LED junction and the temperature of that junction. Results of thermal investigations of a LED downlight are presented. The results suggest that the inherent forward voltage/ junction temperature dependency of LEDs can be used to measure and monitor LED junction temperature in a luminaire under operational conditions.

Measurement of junction-to-ambient thermal resistance of a LED lighting luminaire

Recent advancement in solid state technology has made LED lighting energy-efficient and today it is one of the rapidly-developing lighting technologies. Design of LED lighting luminaires is still repeatedly governed by misinterpretations and inappropriate use of the related solid state lighting technology. Heat is generated as byproduct of the light generation process at the LED junction; this heat needs to be dissipated in an efficient manner. The correct method of thermal management in the LED luminaire is critical for effective heat transfer from the junction to the ambient. Light output, useful life and long term reliability of an LED luminaire are strongly associated with the temperature of the LED junction. Inadequate heat dissipation influences LED life and consequently the long term reliability of the entire LED luminaire. It is therefore important to have the proper knowledge about the light-output and thermal properties of the LED luminaire. This work proposes a methodology for the measurement of the junction-to-ambient thermal resistance of a market ready LED luminaire using the linear relationship between forward voltage and junction temperature of the LEDs. Measurement of the junction-to-ambient thermal resistance of a LED luminaire is essential to assess the quality of the thermal design of the luminaire. Considering two LED luminaire with similar electrical and photometric characteristics, the LED luminaire with lower junction-to-ambient thermal resistance has better heat management system compared to the one with a higher value of the junction-to-ambient thermal resistance. The methodology used in the study and findings of this study are discussed in this paper. If two similar LED luminaires are tested using the proposed method, their thermal management systems can be assessed based on junction-to-ambient thermal resistance.

Design and simulation of grid connected hybrid solar-WECS using SIMULINK/MATLAB

As a result of rising concern of global warming and the depletion of fossil fuel reserves, many are looking at sustainable energy solutions to preserve the earth for the future generations. Environmentally friendly solutions are becoming more prominent than ever as a result of concern regarding the state of our deteriorating planet. This paper presents one of the alternate ways for the power generation, which is clean and economical for the future generation. The two sources which are used for power generation are solar and wind. DC output of photovoltaic panel and rectified dc output of Wind energy conversion system(WECS) is fed to the boost converter which is operating in closed loop in-order to maintain constant output power in any environmental condition. It consists of wind turbines with permanent magnet synchronous generator (PMSG). The output of boost converter is feed to the common dc link which is connected to the 3 phase Sinusoidal pulse width modulation (SPWM) inverter, which converts its dc input to 3 phase AC output. Simulated 2KW solar and 3.2KW wind hybrid system. The simulation of whole hybrid model is done in SIMULINK/MATLAB.

Model based control using C2000 microcontroller

A model based control is used to control a complex system which has a large settling time. The system that is shown in this paper is a drum boiler system integrated with a solar water heating system to provide pre-heated feed water as input to it. Thus, making a hybrid energy system where energy conservation is obtained by the use of solar energy in conventional thermal power plants. Matlab/Simulink is used to model the plant dynamics and use the same model to estimate current state and validate the real time results by the use of processor in loop simulation.

A review of existing methods for study and analysis of thermal design of LED lighting products

The lifetime of LED luminaires, made of high power LED arrays, operating under hostile conditions is determined by their thermal design, operating junction temperature and thermal transients managed by the thermal system. Thermal transient characterization is a noninvasive study of the thermal resistance characteristics or thermal design of the LED luminaire. This procedure can identify anomalies in the thermal design or irregularities in the heat conduction path from the LED junction to the ambient. Any increase of thermal resistance along the heat conduction path can cause excessive junction temperature build up and cause early failure or increased degradation of device. The scope of this work is study the existing method for thermal transient characterization and analysis using the evaluation of the structure function of the heat conduction path of LED lighting product. It can be concluded that structure function approach is a very superior procedure for thermal transients characterizing the heat conduction path and estimating junction-to-ambient thermal resistances.