- Lumens are a measure of the actual quantity of lighting produced by a source; in other words, brightness. Another way of expressing this is that the output of a source, technically called its luminous flux, is measured in Lumens, often abbreviated lm.
- A Lumen is the measurement of brightness currently in use. In 2011 the US Federal Trade Commission began requiring new labels on bulb packages, that highlight Lumens instead of Watts. Watts had been the previous means of indicating the brightness of an incandescent lamp because the amount of energy used – measured in Watts – is related to the amount of emitted. Newer, more efficient bulbs, produce more while using less energy; so wattage is no longer an accurate measure of the amount of illumination emitted.
Lumens as Related to Solar Lights and Other Lighting Sources
- The brightness of the sun, measured in Lumens is about 100,000.
- To compare, one candlepower is about 12.57 lumens.
- A 40-Watt incandescent lamp produces about 380 to 460 Lumens, while a 100-watt lamp produces 1700-1800 Lumens.
- The majority of systems range from 20-Watt LED, producing more than 2000 Lumens to 90-watt LED, yielding over 9000 Lumens, and typical LED lamps are in the 35-Watt to a 50-Watt range.
The wattage rating is the amount of energy required to produce a certain amount of light. Higher wattage produces more light but uses more power. The 40-watt lamp uses 40 watts of energy per hour; the 100-watt lamp uses 100 watts of power.
For a solar light, the wattage measures the necessary power provided by the PV-powered battery to power the lamp for the time required; the Lumens is a measurement of lamp output. The more efficient the lamp, the better the performance and the lower the cost.
Most PV systems use lamps between from 20-Watt LED (2000+ Lumen) to 90-Watt LED (9000+ Lumen), ranging between 35 and 50 Watt. Security and output requirements tend to use lamps at the high end of the range, while residential/remote applications tend toward the lower end.
Lights Commonly Used in PV systems
Solar LED lights have now become the most common.
LED’s have the advantage of providing higher Lumens with lower energy consumption. Power savings is the main reason why LED’s, or light-emitting diodes, are used. LED’s contain a chemical that emits visible light when an electric current goes through it while emitting almost no heat. In other words, they are solid state. They have no filament to burn out, which lends them a much longer useful lifespan. Their energy consumption is a fraction of that of incandescent bulbs or the same wattage of fluorescent or neon bulbs.
The long useful lifespan is a good reason for using LED’s. Lamp lumen depreciation is the predicted
reduction in output for a particular source over a specified time period. According to Brad Picht, writing for graybar.com, LED’s require 50,000 to 100,000 hours to depreciate 30 percent.
The Significance of Higher and Lower Lumens
For a power source that may be weak, higher Lumens make LED’s, which use less energy, an obvious choice for lighting. Lower Lumens would mean that a greater amount of energy would be required to power the light, perhaps more energy than could be provided by the sun. Therefore, higher Lumens are essential.
In conclusion, LED’s are strongly preferred because of their efficiency and longevity and are especially suited to use in sun-powered installations because of their Lumens and their low energy consumption. They have justifiably become the predominant type of sun-powered lighting.
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