Dimmable Lighting System Research Articles

A model-based predictive dispatch strategy for unlocking and optimizing the building energy flexibilities of multiple resources in electricity markets of multiple services

In recent years, demand side measures have been increasingly considered to provide flexibility services in different timescales (seconds, minutes, or longer timescale) and thereby improve the reliability and overall energy efficiency of power systems. However, the existing studies about multiple grid flexibility services only focus on the generation or storage resources, without considering the variety, controllability, and flexibility of different loads. Few studies have investigated the economic benefits and contributions of building energy flexibilities with fast and slow response speeds to different flexibility services. Therefore, this study develops a novel model-based predictive dispatch strategy for hybrid building energy systems to maximize the economic benefits in electricity markets of multiple services. The energy flexibilities of buildings are transformed to the bids for energy trading, peak charge and ancillary services in the electricity market. The system characteristics and the comfort (or preferences) of occupants regarding multiple flexibility resources, including dimmable lighting systems, HVAC systems, electrical vehicles and stationary batteries integrated with PV are considered. Tests are conducted to evaluate the performance of the strategy and the impacts on building operation, using real-time TRNSYS-MATLAB co-simulation. Test results show that electricity costs can be reduced by up to 26.1% when fully utilizing multiple revenue streams in an electricity market. The impacts of uncertain and high-granularity grid control signals on the indoor environment, the charging requirements of EVs and state of charge (SOC) of battery are negligible while the expected building power modulation following the real-time power grid control signals can be achieved.

Model predictive control for integrated control of air-conditioning and mechanical ventilation, lighting and shading systems

Modern buildings are increasingly automated and often equipped with multiple building services (e.g., air-conditioning and mechanical ventilation (ACMV), dynamic shading, dimmable lighting). These systems are conventionally controlled individually without considering their interactions, affecting the building’s overall energy inefficiency and occupant comfort. A model predictive control (MPC) system that features a multi-objective MPC scheme to enable coordinated control of multiple building services for overall optimized energy efficiency, indoor thermal and visual comfort, as well as a hybrid model for predicting indoor visual comfort and lighting power is proposed. The MPC system was implemented in a test facility having two identical, side-by-side experimental cells to facilitate comparison with a building management system (BMS) employing conventional reactive feedback control. The MPC system coordinated the control of the ACMV, dynamic façade and automated dimmable lighting systems in one cell while the BMS controlled the building services in the other cell in a conventional manner. The MPC side achieved 15.1–20.7% electricity consumption reduction, as compared to the BMS side. Simultaneously, the MPC system improved indoor thermal comfort by maintaining the room within the comfortable range (−0.5 < predicted mean vote < 0.5) for 98.3% of the time, up from 91.8% of the time on the BMS side. Visual comfort, measured by indoor daylight glare probability (DGP) and horizontal illuminance level at work plane height, was maintained for the entire test period on the MPC side, improving from having visual comfort for 94.5% and 85.7% of the time, respectively, on the BMS side.

A Wireless Dimmable Lighting System Using Variable-Power Variable-Frequency Control

This article proposes and implements a wireless dimmable lighting system using variable-power variable-frequency (VPVF) control, which can eliminate the use of secondary converters via wireless power transfer (WPT). The proposed scheme integrates the secondary T- LCL circuit into a sealed antiparallel light-emitting diode (LED) lamp, which takes the key merits of safety, flexibility, maintenance free, and convenience for manufacturing. Moreover, it can effectively widen the LED dimming range and reduce the starting voltage requirements, which inherently improve the output fluctuation insensitivity and voltage deviation tolerance. In contrast to phase shift control, a WPT-inherent VPVF control is proposed to realize effective reductions in both the switching frequency and switching losses, while maintaining the regulation accuracy and output fluctuation suppression by up to 48.45% as compared with burst firing control. The system electrical efficiency can reach 88.08% with 20-cm transfer distance and it is improved by 3.35% during power control. Both theoretical analysis and practical experimentation are given to verify the feasibility of proposed VPVF-modulated wireless dimmable lighting system.

Investigation of an integrated automated blinds and dimmable lighting system for tropical climate in a rotatable testbed facility

Performance of automated blinds and auto-dimming lighting system in providing lighting energy savings and occupant visual comfort was studied in a rotatable testbed facility located in tropical Singapore. The automated Venetian blinds system, consisting of a daylight-redirecting top portion and a glare-controlling bottom portion, was controlled by an in-house developed control algorithm designed specifically for tropical climate of Singapore to introduce maximum daylight while minimising Daylight Glare Probability (DGP). The auto-dimming lighting system used Digital Addressable Lighting Interface (DALI) controller to control T5 fluorescent and LED luminaries. Energy consumption by the lighting system, working plane illumination distribution and DGP were monitored by a network of sensors and high-dynamic range (HDR) camera systems. Compared to non-dimmable T5 lighting, LED lamps provided about 24% of lighting energy savings. Auto-dimming technology showed about 46% lighting energy savings. LED lamps coupled with auto-dimming showed around 80% lighting energy savings. Without window blinds, the working plane illuminance exceeded the recommended 3000 lx level during certain time of the day and DGP exceeded 0.35. The automated blinds effectively eliminated glare discomfort, and with the automated blinds working in conjunction with the auto-dimming, significant lighting energy savings was achieved without compromising the illuminance level at the working plane. 75% of lighting energy savings was achieved for North orientation and 63% for East orientation. Façade orientation was found to have a significant impact on the lighting energy savings potential, with the North orientation achieving higher daylight savings due to higher daylight redirection possibility throughout the day. The lighting energy savings potential is higher for clearer sky conditions due to higher daylight availability. Implementation of daylight re-directing shading system has significant lighting energy savings in the tropics. These lighting energy savings can be captured by deploying an auto-dimming system. With careful design of the system and control algorithm, the lighting energy savings can be achieved while maintaining good visual comfort.

Room and window geometry influence for daylight harvesting maximization – Effects on energy savings in an academic classroom

Lighting systems have a fundamental role for the overall buildings energy consumption. Therefore, remarkable efforts are required for optimizing the lighting systems energy use and for finding new daylight harvesting solutions. In this paper, the impacts on daylight harvesting provided by different room and window geometries and their effects on energy savings are presented. An academic classroom with only one window is chosen as case study and it is supposed that the window orientation is modified according to the four cardinal points. A climate-based approach was chosen for the multiple simulations, carried out via DIVA software, by assuming: square and rectangular classroom geometries with the same total area; square and rectangular window shapes having Window to Floor Ratios (WFRs) equal to 8% and 12%; two different dimmable lighting systems, in order to quantify the energy savings, by considering fluorescent and LED dimmable lamps. The daylight analysis, performed by evaluating both the Daylight Factor (DF) and the Daylight Autonomy (DA), showed that room and window geometries have high influence on daylight harvesting maximization, allowing remarkable energy savings (up to 48.5%) with respect to non-dimmable lighting system. In particular, the best energy result, equal to 467.5 kWh/yr, was obtained with rectangular room and window geometries coupled with LED lamps and WFR equal to 12%.

A Study to Improve the Quality of Street Lighting in Spain

Street lighting has a big impact on the energy consumption of Spanish municipalities. To decrease this consumption, the Spanish government has developed two different regulations to improve energy savings and efficiency, and consequently, reduce greenhouse-effect gas emissions. However, after these efforts, they have not obtained the expected results. To improve the effectiveness of these regulations and therefore to optimize energy consumption, a study has been done to analyze the different devices which influence energy consumption with the intention of better understanding their behavior and performance. The devices analyzed were lamps, ballasts, street lamp globes, control systems and dimmable lighting systems. To improve their performance, they have been analyzed from three points of view: changes in technology, use patterns and standards. Thanks to this study, some aspects have been found that could be taken into account if we really wanted to use energy efficiently.

Adjustable Multi-Light Wireless Remote Control System Designed LED Light

With the development of LED technology, the actual demand of the people for the smart home lighting, this paper designed a multiple lamps for indoor wireless remote control dimmable LED lighting systems. LED driver is using two levels of drive structure, and driver power supply adopts double-road current output, and the size of the output current of each constant current source is flexible to adjust by remote control. Wireless remote control part control multiple lamps by using 4 * 4 keyboard, which realizes intelligent management of LED interior lighting in the smart home.

A double-pane window with enclosed horizontal slats for daylighting in buildings in the tropics

In the tropics, daylighting from a side window requires shading to intercept direct sunlight from the window whilst allowing penetration of daylight from sky. In this paper, daylighting from a double-pane glazed window with enclosed horizontal slats (slat window) was investigated for which it is situated on either north or south wall of a room. Full-scale experiments and simulations were conducted to characterize distribution of the interior daylight from the slat window under a real tropical climate. Performance of the slat window was evaluated in terms of the “useful daylight illuminance” (UDI), interior daylight availability and light power density (LPD) of an integrated dimmable lighting system. Empirical formulas were developed for determining annual average LPD values of the dimmable lighting system over its served area. The LPD value can be used with a reduced form of the energy equation of Thailand's building energy code to evaluate the reduced annual electrical energy consumption for accreditation of the daylight use in a building. The analysis of life cycle cost proved that the daylighting from the slat window integrated with the dimmable lighting system is cost effective.

End user impacts of automated electrochromic windows in a pilot retrofit application

Automated electrochromic (EC) windows, advanced thermally improved window frames, and a dimmable lighting system were installed in a single, west-facing conference room in Washington DC. The EC windows were commercially available, tungsten-oxide switchable devices, modulated automatically between either fully clear or fully tinted transparent states to control solar gains, daylight, and discomfort glare. Occupants were permitted to manually override the automated EC controls. The system was monitored over a 15-month period under normal occupied conditions. The last six months were used in the analysis. Manual override data were analyzed to assess the EC control system design and user satisfaction with EC operations. Energy and comfort were evaluated using both monitored data and simulations. Of the 328 meetings that occurred over the six-month period, the automatic system was manually overridden on 14 or 4% of the meetings for reasons other than demonstration purposes. When overridden, occupants appeared to have switched the individual zones with deliberation, using a combination of clear and tinted zones and the interior Venetian blinds to produce the desired interior environment. Monitored weekday lighting energy savings were 91% compared to the existing lighting system, which was less efficient, had a higher illuminance setpoint, and no controls. Annual performance was estimated using EnergyPlus, where the existing condition met the ASHRAE 90.1-2007 prescriptive requirements except for a higher window U-value. Annual energy savings were 48% while peak demand savings were 35%.

The Use of Task Lighting in an Industrial Work Area Provided with Daylight

A dimmable task lighting system was installed at six working places in a luminaire factory in France. The factory hall had skylights that prvided a lot of daylight. The purpose was to study which illuminances users select, how often they use additional task lighting, whether they liked the lighting system and if their selections were influenced by the amount of daylight or the type of work. The workers were free to use the task lighting in any way they wanted. The settings of the task lighting were recorded between the winter of 2004 and the spring of 2005. The opinions of the users were sought by means of questionnaires after the testing period. It was found that those workers who worked in the area on more than 20 days in the testing period used the task lighting (viz. switched it on) on average only during 6.5% of the total working time. The task lighting was used more frequently during the times when the amount of daylight was limited (darkness or dark weather) and less frequently when there was more daylight in the area. And the task itself also had an influence on the preferred illuminance, and hence on the frequency of use of the task lighting. The preferred horizontal task illuminances supplied by the task-lighting luminaires varied from person to person, with an average of around 600 lux. The users expressed the wish that they wanted to keep the system after the test period, and 41 per cent of the users felt that the task lighting helped them to perform better.

User attitudes toward occupant controlled office lighting

The use of locally addressable dimmable lighting systems has been examined in 14 open-plan office buildings. This paper discusses user attitudes toward control systems and the luminous conditions they produce. The majority of users are satisfied with both the quantity and quality of light on their workstations and are generally positive towards systems. This is despite large numbers of them working in illuminances significantly below current CIBSE recommendations. This indicates a significant potential for energy saving, since increased personal control leads to the use of lower lighting levels without detriment to occupants’ perceived lighting quality and visual comfort.