China
Africa
Explore chapters and articles related to this topic
Low Hanging Fruit
Published in Alden M. Hathaway, Tripp Hathaway, Energy Independence: The Individual Pursuit of Energy Freedom, 2022
Alden M. Hathaway, Tripp Hathaway
LED stands for light-emitting diode. Instead of using a filament or fluorescent powder, LEDs use a diode. The diode is essentially an electronic chip where electrons jump from one point to another. This jump emits light. LEDs often sport the traditional bulb shape characteristic of the traditional incandescent, but they are highly versatile and can fit in many different types of lighting applications. Aesthetically, it’s nice to return to the consistency of that traditional bulb shape we are used to, after some of the funnier shapes of CFLs. Another benefit of LEDs is the ability to manipulate the hue of the light output without sacrificing brightness or efficiency. LEDs can be made to shine bright white, with the same quality and hue of light as natural sunlight. This type of light is very popular in retail as it maintains the fidelity of color in the merchandise on display. They can also carry a softer glow more similar to incandescents for the cozier feel in your home you may be used to.
Dimming Systems
Published in Richard Cadena, Electricity for the Entertainment Electrician & Technician, 2021
LEDs operate on low-voltage DC with a constant current. Accurately varying the current (and dimming level) is very difficult, so LEDs are typically dimmed by modulating the width of an on/off, which is referred to as pulse-width modulation (PWM). A power supply converts the incoming AC to low voltage DC, and then it switches the current on and off within a fixed period of time, typically in the range of about 1 to 3 milliseconds. The percentage of time that the LED is on compared to the time it is off is the “duty cycle,” and it determines the perceived brightness. The resulting current waveform is a square wave, and the dimming level controls the duty cycle. The wider the width of the pulse, the brighter the output of the LED; the narrower the width of the pulse, the dimmer the output. (See Figure 13.2.) At full brightness, the current is steady DC and at blackout there is no current at all.
Introduction to Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
Similarly, the word “transducer” has originated from the Greek word transducere, which means “lead across.” It is a device, usually electrical, electronic, electromechanical, electromagnetic, photonic, or photovoltaic, that converts power from one system to another in either the same or a different form. A transducer is a device that is actuated by energy from one system and supplies energy, usually in another form, to a second system. For example, a motor converts electrical energy to mechanical energy; hence, it is an example of a transducer. A loudspeaker is a transducer that transforms electrical energy signals into sound energy. An ultrasound transducer transforms electrical signals into ultrasonic waves or vice versa. Similarly, a light-emitting diode (LED) converts electric energy into light energy.
Using smart lighting systems to reduce energy costs in warehouses: A simulation study
Published in International Journal of Logistics Research and Applications, 2023
Marc Füchtenhans, Christoph H. Glock, Eric H. Grosse, Simone Zanoni
In most warehouses, lighting is generally turned on during working hours, and areas are often (unnecessarily) illuminated, even when no workers are present (Park, Lee, and Kim 2015). SLS can lead to substantial energy savings, and contribute to improving the environmental footprint of a warehouse. SLS use light emitting diodes (LEDs), which provide several advantages over traditional lighting systems in industrial applications, with the most important being a high luminous efficiency of up to 200 lm/W (Shur and Žukauskas 2011). In comparison, fluorescent lamps provide approximately 100 lm/W and incandescent bulbs provide approximately 15 lm/W. LEDs also have a long lifespan, reaching more than 100,000 h (Chang et al. 2015; Schratz et al. 2013). They can adjust the spectral power distribution, are robust to and independent of the amount of shifting, and provide fast modulation rates (Shur and Žukauskas 2011). The control of LEDs and networked lighting systems make traditional lighting ‘smart.’ Thus, SLS become a closed system through regulation (Chew et al. 2017), based on the smart interplay of sensors, light sources, and external influences (such as the behaviours of users and daylight). SLS are energy-efficient, and can be adapted to changing and complex situations.
Precious and critical metals from wasted LED lamps: characterization and evaluation
Published in Environmental Technology, 2022
Marcelo Pilotto Cenci, Frederico Christ Dal Berto, Bianca Wurlitzer Castillo, Hugo Marcelo Veit
The carcass of the LED lamps, which includes the pin, socket, bulb, and pieces of the main body, is mainly made of pieces of aluminum, nickel, polycarbonate, polyester, and polyamide [18]. Approximately, 71%–76% of the total LED lamp mass is in the carcass [18]. The LED module is normally made of an aluminum plate and polymers, with the main functions of heat dissipation and mechanical protection [19,20]. PCBs are recognised for their high aggregated value due to the presence of several metals (approximately 28% of metallic fraction [21]), including the precious metals gold and silver, and critical elements [22]. LEDs work as semiconductors diodes (called chips) which emit light when an electric current is applied [23]. The semiconductors are mainly made of gallium nitride (GaN), and the electrical connections made of gold and silver [24]. Covering the diode, a casing of yttrium-aluminum-garnet (Y3Al5O12, doped with Ce), called yellow phosphor, mixed with polymers is used to convert the emitted blue spectrum into the visible spectrum [25]. Although the cited technologies and materials are the most used, many others can be applied for the same objectives. Indeed, Franz and Wenzl [24] present an extensive list of materials that can be used in the LED lamp manufacturing.
Understanding multi-domain compact modeling of light-emitting diodes
Published in Cogent Engineering, 2021
There is variation in terms of light output and color characteristics from one LED to another LED due to manufacturing errors. The only way to achieve desired characteristics from an LED is to drive it at current stated in the data-sheet as specified by the manufacturer. Dimming and brightness control of LEDs is only possible with current regulation as specified in the data-sheets. Operating LEDs outside its specifications will lead to unacceptable changes in light output and color characteristics. This is further aggravated due to variation in terms of light output and color characteristics from one LED to another LED due to manufacturing errors (Semiconductors, 2011a). Constant current control shown in Figure 6c eliminates the use of current limiting resistors and regulates current at desired levels irrespective of variation in forward voltage due to change in junction temperature or manufacturing errors.