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How to "measure" a Solar Light.

Posted by Martin Pfaff on

What is the difference between a  high-quality Solar Light and an average one?  

Choosing the right solar lamp can be much more complex than it might seem at first. To be clear, the energy input of two solar lamps with the same sized solar panel (16% efficiency) and set to the same angle will be the identical. In other words, with the same location, they well have the same amount of power available.

How to "measure" a Solar Light.

The quality of a solar lamp is often mistakenly measured by the maximum wattage of the LED. However, the maximum wattage of a solar lamp is not directly related to the maximum achievable light output.

As opposed to cable powered street lamps, with solar lamps, the energy production from sunlight crucially depends on the efficiency of the lamp. The most common solar lamps (80Wp) are on average only operated with 4 to 15 watts. As such, it is important how many lumens per watt can actually be emitted.

Conventional solar lamps have an efficiency of 100-130 lm/W. A high quality solar lamp sets itself apart because of its high efficiency of 190-200 lm/W.

The following example makes the difference clear:

Sample Calculation 

An 80Wp solar lamp (at the 46 degrees latitude /in  Invercargill, New Zealand) is operated with 6.6 Watts. The following example makes the difference clear:


Watts x lm/W = LUMEN (light strength of the LED)

6.6 x 120 = 792 lm (average-efficiency LED)

6.6 x 195 = 1287 lm (high-efficiency LED)

With this example, it becomes very clear that the maximal wattage of an LED is completely beside the point.

With the new LED from photinus, an efficiency of 200 lm/W can be achieved!




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