Users Guide to Off-Grid Energy Solutions
Lights, Lighting and Lamps Fact Sheet
Lighting is one of the most important sources of energy demand in the world. Most people concerned with rural electrification and off-grid electrification, view lighting as a key to people�s demand for electricity. Recent studies show that this is not always the case, that people may want electricity first for television and radio/cassettes, but lighting of homes, businesses and institutions (schools, hospitals, clinics, government buildings) remains one of the most important demands for electrification.
There are a number of means to meet lighting demands. Candles remain the most widely-used lighting source in the world. Kerosene follows candles as the next most widely used energy source for lighting. There are a number of kerosene lamps, ranging from simple wick lamps (simple to "hurricane" with a glass globe) to high pressure kerosene (or "paraffin" as it is known in many parts of the world) lamps.
Flashlights/torches, powered by dry cell or rechargeable (general nickel-cadmium/nicad) batteries follow kerosene as the next most widely used source of off-grid lighting. These can range from simple hand-held torches used for simple tasks (walking, bike riding, etc.) to more complex fixed rechargeable lighting systems.
Next in order of use are lights and lighting systems powered by lead-acid batteries (e.g., automobile batteries). These lights can be of the incandescent or the fluorescent type. People rarely use car batteries only for lighting. Lead-acid batteries tend to be used for lighting and other purposes, such as for powering radios, radio/cassettes, televisions and video (VCR) machines.
Next in order of use are generating sets ("gensets") either powered by diesel or petrol (gasoline, benzene). As with automobile batteries, gensets generally power far more than lights, and are generally not purchased only to provide lighting power. One of the most rapidly expanding sources of energy for lighting comes from photovoltaic (PV) systems. PV lighting systems, and the technology that goes with those systems, have reached virtually all parts of the globe.
Electrical lighting devices have changed dramatically over the past several decades. The original incandescent light (highly inefficient, short life span), is rapidly being replaced by more energy efficient, and healthier lighting. Fluorescent lights have been around for many years. They are readily available, much more efficient than incandescent lights, and are adaptable to virtually any form of electricity system. Newer, more efficient lights include halogen, CFLs and LEDs. This new generation of lamps are evolving very rapidly, and are quickly being adapted from conventional grid-connected systems, for off-grid applications, including hand-held torches, PV lighting systems, and other isolated electricity systems.
candela: Unit of luminous intensity (cd)
CCT: Correlated Colour Temperature = colour appearance of the light source. Unit: Kelvin
CFL: Compact Fluorescent Lamp
CIE: International Commission on Illumination
cluster-LED: Recently-developed lighting technology based on output of Light Emiting Diodes. Cluster LEDs are more efficient and long-lasting than fluorescent lamps. They are best suited for task-lighting as their output is directional.
domestic: Usually refers to the household sector. Example: Families use domestic lighting for reading in the home.
fluorescent: light emitted from special inert gases (generally neon) when an electric current is passed through it. Fluorescent lamps are much more efficient than incandescent lamps, and are preferred over incandescent lamps for energy efficiency. However, not as efficient as halogen or LED.
general lighting: Illumination of a large area. Unit lux = lumen/m2
halogen lamps: lamps with very low wattage, that generate high intensity light through a combination of specially coated, highly efficient reflectors. Very low voltage with high efficiency deliver of light for low power.
illuminance: Luminous flux per unit area. Unit lux = lumen/m2
illuminous efficacy: Efficiency with which a surface is lit. Unit: lux/Watt
incandescent: an incandescent lamp produces light when its wire filament is heated by electricity to 'incandescence. Wire filaments are made of tungsten.
lamp: Light source (such as incandescent bulb, fluorescent tube)
LED: Light Emitting Diode (a small, low-voltage light source)
light-emitting diode (LED): a type of diode which lights up when current is flowing through it. Commonly used as an indicator in charge controller
light colour: the actual appearance of light emitted by lighting appliances.
lmh: Lumen-hour: luminous flux integrated over one hour
local lighting: Illumination of a (small) work area
localised lighting: Illumination of only part of an area
LOR: Light Output ratio = Luminaire efficiency
lumen: Unit of luminous flux (1m)
luminaire: Complete lighting system
luminous efficacy: Efficiency of lamp or luminaire. Unit: lumen/Watt
luminous intensity: Amount of light emitted in a certain direction
lux: Unit of illuminance
orientation light: Lighting which is just sufficient to recognise shapes
PLC: Type of CFL, with 2 or 4 tubes
pressure lamp: a term usually used to refer to a kerosene lamp that is charged to a high pressure (usually by hand) in order to achieve vapourisation of the kerosene to aid combustion and generate a high intensity light. The kerosene is burnt and light emitted through the 'mantle'.
PV Lighting System: a system that includes at least a PV module, a battery, an inverter and a light. Can include a large number of lights, preferably high efficiency fluorescent, LED, halogen lamps.
RA: Colour Rendering Index = Degree with which different colours can be recognised compared to a standard light source
reflector: Part of the luminaire with reflects light (usually downwards)