1 ISAT 413 ─ Module II:Lighting Topic 4: Energy efficient lighting technologies and their applications (3)  Latest Technologies in Lighting: Solid-State Lighting (SSL_LEDs) Overview ( (  Course Projects Discussion

2 Solid state lighting technology involves the use of electricity as a fuel to inject electrons and holes into a solid-state semiconductor material. When the electrons and holes recombine, light is emitted in a narrow spectrum around the energy bandgap of the material. Because the light is narrowband, and can be concentrated in the visible portion of the spectrum, it has, like fluorescent, a much higher light-emission efficiency than incandescence. However, as with fluorescent, because the light is narrowband, it does not fill the visible spectrum with light, and appears colored. Hence, the evolution of Solid-State Lighting must eventually include overcoming similar challenges associated with converting the narrowband emission into –semi-broadband emission that fills the visible spectrum to give the appearance of white light. The first device in which such light emission was controlled was the light- emitting diode (LED), demonstrated by Nick Holonyak and co-workers at the General Electric Corporation in The first commercial LED products were introduced in 1968: indicator lamps by Monsanto and electric displays by Hewlett-Packard. Solid-State Lighting Technology

3 Semiconductor light emitting devices, once limited to a narrow range of colors, now span nearly the entire visible spectrum. Someday, they may be bright, efficient and inexpensive enough to replace vacuum tubes for white lighting. Energy consumption and environmental pollution would be reduced, and the quality of the human visual experience would be enhanced, dramatically. Yet, enormous challenges lie ahead. The vision of Solid-State Lighting is to complete the evolution of lighting from primitive fire-based technologies like candles and lanterns, to vacuum-tube and bulb based technologies like incandescent and fluorescent bulbs, and finally to semiconductor-based technologies like LEDs and lasers. The Vision of Solid-State (SSL) Lighting

4 There are seven steps to deliver white-light from LEDs: 1.Delivering electrical current to the SSL-LED light fixture. 2.Injecting electrons and holes to the semiconductor. 3.Transporting and tapping the electrons and holes. 4.Creating photons. 5.Extracting photons from the chip. 6.Transforming monochromatic into white light. 7.Delivery of the white light to the viewer. Light Emitting Diodes (LEDs) SSL-LED Technology Targets Year Luminous Efficacy (lm/W) Lifetime (khr)20>20>100 Flux (lm/lamp)252001,0001,500 Lumens Cost ($/klm)20020<5<2 Color Redering Indix (CRI)7580>80 Lighting Markets PenetratedLow-fluxIncandescentFluorescentAll

5 There are three possible approaches (as shown in the Figure below) to white-light production: 1.The wavelength conversion approach, in which white light is created by using a single UV LED to excite a tri-color phosphor. 2.The color mixing approach, in which white light is created by mixing primary light from three LEDs (red, green, blue). 3.A hybrid approach, in which white light is created by mixing primary light from a blue and/or red LED with light created by using the blue LED to excite a mono-or duo-color phosphor. Three Possible Approaches to White-Light Production

6 Advantages: SSL_LEDs are available in almost any wavelength in the visible region, and the spectrum design of white LEDs may be more flexible than for traditional discharge lamps where the available spectra depends on available phosphors and emissions from gas. Three-chip (or more) white LEDs are expected to provide good color rendering that can be used for general lighting. Benefits on Energy: SSL-LEDs, through their higher efficacy, could reduce significantly energy load and environmental pollution. Benefits on Environment: SSL_LEDs are mercury-free, and easier to dispose of than fluorescent lamps. Advantages and Benefits of LEDs

7 Course Projects Discussion Course Project Ideas:  National Energy Policy (May 2001): Topics include Using Energy Wisely, Energy for a New Century, Nature’s Power, and America’s Energy Infrastructure. National Energy Policy  Battelle Experts Forecast the Top 10 energy innovations for (  Gas turbine, the future power backup: Investment on power companies, for example, the Caterpillar Inc. uses small size gas turbine for generating electricity as backup of electricity blackout.  A $50 billion dollars national transmission grid restoration project, and a $100 billion dollars national state-of-art next generation of power distribution system.  Superconducting cables, the latest technology for power transmission lines.  Fuel cells for power generation.

8 Course Projects Discussion (continued) Course Project Ideas (continued):  DOE Report on Basic Research Needs for Solar Energy Utilization (April 2005).Basic Research Needs for Solar Energy Utilization  Energy Bill signed on July 29, Energy Bill  Entering the Age of Oil Depletion – energy efficient solar hot water, photovoltaic, biomass systems, and alternative fuel vehicles. Entering the Age of Oil Depletion  Northeast Power Outage On Thursday August 14 th, at around 4 pm (EDT) a cascading power outage resulted in a blackout that affected more than 50 million individuals. Technical problems behind the 08/14/03 8-state blackout. Four major causes include the first line failed in Ohio caused a power surge, alarm failed in some distribution stations, there was a tree that supposed not to be that near to a transmission line, and the failure of automatic cut-off systems within the interconnected network.  Topics within ISAT 413 course content, e.g., efficient refrigerator, combined heat and power (CHP), energy efficient transportation vehicles, …, or any energy efficiency related project of your own.