Pico Power – Lighting Lives with Leds

In the past 5 years, high brightness LEDs have begun to penetrate the lighting market. High brightness LEDs are attractive due to their high efficiency, very low power consumption and very long lifespans. This paper describes experiences in using white LEDs for lighting rural households in developing countries. The Light Up The World Foundation (LUTW) is an aid organization that has formed partnerships with a leading LED manufacturer to help deliver affordable benefits of efficient lighting services to those villages that do not yet have access to electricity. With new high power WLEDs, voltage regulation and current regulation are required for efficient use in solar home lighting systems. The lifetime of the devices is sensitive to temperature so the use of a proper heatsink is essential. Finally the LED enclosure needs to be appropriate to direct the light to where it is required. The long life of LEDs and low power requirements results in a village lighting system that has extremely low ongoing maintenance costs. LUTW estimates annual lighting costs of less than $10 per lamp per household for a white LED lighting system. 1 RURAL ELECTRIFICATION IN DEVELOPING COUNTRIES Two billion people currently have no access to electricity [1]. However, energy is an integral part of these people’s lives. Often, cooking fuel is in the form of biomass, and requires many hours per week to be collected. Crops need to be processed, such as rice dehusking and flour milling, and this is often done by hand. Village life is rarely relaxing, and tasks continue into the evening, using fuel-based light sources such as kerosene lamps, batteries, or resin-soaked sticks. Inefficient energy use in rural communities can result in deforestation, reliance on petroleum imports, health problems from smoke inhalation and hours each day of manual labour. The provision of electricity can alleviate some of these burdens. In Nepal, locally manufactured micro hydro turbines are used to grind flour two to four times faster than by hand, which is usually the work of women and children. Women often prefer to walk to the next village to use a water-powered oil-expeller than to spend hours manually squeezing drops of oil from mustard seeds. The use of low-wattage rice cookers can preheat water using off-peak power, reducing the fuelwood consumption to sustainable levels and saving hours of collecting time. The hours saved can then be used for literacy programs or cottage industries, and electric lighting can help children study at night as well as providing a safer environment for household chores. A lamp outside the main door is also very good for keeping evil spirits away! However, rural electrification is often a drain on government funds, requiring subsidies before electricity is affordable for rural households. Low cost design alternatives should be thoroughly investigated, and these designs must include an analysis of expected loads. In the poorer unelectrified regions, electric cooking and heating are rarely affordable for the majority of newly electrified households. Electricity is mostly desired for clean lighting, refrigeration, radio and television, as well as for small industrial uses during the day. Most rural electrification results in high peak evening loads and lower daytime loads. The majority of the evening peak load can usually be attributed to lighting, and therefore, efficient lighting alternatives need to be a key design feature for rural electrification in developing countries. 2 LIGHTING OPTIONS Lighting alternatives for rural communities can either be electric or non-electric. Traditional electrical lighting alternatives include incandescent bulbs, halogen lamps, fluorescent lamps and other less used alternatives. Recent developments include high power factor compact fluorescent lamps, white high brightness LEDs and plasma lights. Non-electric options are mostly fuelbased – kerosene, batteries, resin-soaked kindling, etc. Non-electric lighting is grossly inefficient and very expensive. This is illustrated by using lumen-hours as a measure of lighting service. Most households that do not have access to electricity use some form of fuel-based lighting and spend around 2.5% of their income for this low quality service [2]. A wealth of literature exists discussing the lower life cycle costs of fluorescent lamps compared to incandescent bulbs, which needs no repetition here. Therefore, this study compares fuel-based lighting to fluorescent lighting and the latest white LEDs. 3 TECHNOLOGIES AND PROGRAMS 3.1 Fluorescent lighting Fluorescent lighting, by far the most cost-effective method of household lighting, can be separated into two lamp types – linear tube fluorescents and compact fluorescent lamps, which have bent tubes. Linear lamps are available in sizes from 3W to 40W or larger. However, 20W and 40W lamps are the most common. Compact fluorescents (CFLs) are available from 5W to 30W, with a good range of intermediate wattages. Linear fluorescent lamps have improved in efficiency in the past 15 years, resulting in smaller diameter tubes and increased efficiency, as well as a variety of warmer white colours. While T12 technology has been outdated in Australia for years, it still alive and well in many developing countries. Outstanding energy savings can be achieved by ensuring all manufacturers switch to more modern lighting technologies. Thailand’s power generator EGAT managed this feat in 1993 [3], and expected a reduction in peak loads of 920 MW, due to a local market of 230 million fluorescent tubes accounting for 80% of all lighting. Most T12 lamps were phased out within 5 years, with marketing costs of around AU$10 million. That’s about $11/kW! Compact fluorescent lamps (CFLs) experienced teething problems in the 80’s and early 90’s. The lamps had heavy magnetic ballasts which had high harmonic distortion and low power factor, cast a bluish light and were rather large and awkward to fit when re-lamping. However, improvements in phosphors has allowed a significant reduction in tube size, and electronic ballasts now have power factors greater than 0.8 and low THD levels. There are also options in lamp colour, from a warm 2700K light like an incandescent bulb to a daylight-like 5000K. However, such issues are reserved more for the more fickle consumers in developed countries. CFLs have been recognized in recent years as a costeffective method of reducing greenhouse gas emissions. The Energy Saving Trust [4] in the UK is an example of a program that, after running multiple programs on various technologies, found that re-lamping with CFLs is one of their most effective programs. The Efficient Lighting Initiative [5] is another program that aims to promote efficient lighting in developing countries, and has a global outlook. ELI is an excellent source of high quality, low cost CFLs from manufacturers around the world. CFLs are also being used extensively as a demand side management option for evening peak load reduction (Ilumex in Mexico [6], Polish Efficient Lighting Project [7]) and delaying the building of large power plants (South Africa, Hungary). China is the largest manufacturer of CFLs in the world, with an estimated production of 180 million per year in 1998 and growing quickly [8]. A few manufacturers have passed international quality testing procedures via the China Green Lights Program, and can now offer high quality lamps at lower prices than major manufacturers such as General Electric, Philips or Osram. The author used contacts from the ELI and CGL programs to procure lamps for AusAID village electrification projects in Nepal. 3.2 White LEDs White light emitting diodes (WLEDs) were first available from a Japanese company, Nichia, around 1995 [9]. The basic concept is to coat an ultra-violet LED with a phosphor coat, thus producing white light. Previously white light could be obtained by mounting different coloured diodes closely on a circuit board and allowing the colours to mix to produce a white light. This can be achieved with just two colours (binary complementary colours), but this results in very poor colour rendering. Using three or more colours (RGB) gives satisfactory colour rendering. Using a mix of coloured LEDs is more energy efficient, as single colour high brightness LEDs are 3-5 times as efficient as current white LEDs. Some universities (eg. Boston University) and companies have made LED chips with multiple layers of different coloured LEDs, thus mixing the light within a chip and providing a more visually acceptable solution. The future will now be a battle between RGB LEDs and phosphor-based LEDs. Phosphor-based LEDs have undergone rapid improvement in the last 5 years, with the two major companies emerging as Nichia and LumiLeds [10]. LumiLeds released a 120 lumen, 5 watt white LED in 2002, and Nichia have recently announced a 23 lumen white LED. The efficiencies of these latest WLEDs is 24 lumens/watt, which already surpasses incandescent bulbs (12 lumens/watt) and halogen lamps (15 lumens/watt). In contrast, fluorescent lamps and red LEDs have efficiencies of around 60 lumens/watt. While manufacturers claim a lifespan of 100,000+ hours for LEDs, The Lighting Research Centre [11] found that early phosphor-based white LEDs underwent 40% light degradation in less than 4000 hours. However, such test results quickly become obsolete with each new development, and major lighting and semiconductor manufacturers are spending millions of research dollars on white LED technology. LumiLeds now presents light degradation data in their technical specifications, indicating manufacturers recognize the problem and are finding solutions. Both the US and Japanese governments are committing funds towards LED lighting research, with the aim of reaching 100 lumens/watt by 2010. 4 MARKET RESEARCH Recent market research [12] indicates that the HBLED market is growing at 30% per annum and is a multibillion dollar industry. There is approximately a 50% improvement in cost and efficiency of new HBLED technology every 18 months, which mimics the development of computing power in the past 30 years. This trend is set to continue with increasing participation by the private sector and support from Japanese and US