Comparison of CFL-based and LED-based solar lanterns

Solar lanterns are designed to replace hurricane lanterns for use in remote places where conventional electricity is not available. They not only provide illumination at night but are also instrumental in avoiding the emission of greenhouse gases normally emitted from burning the wick and kerosene in the latter. Light is produced in a solar lantern by igniting either a compact fluorescent lamp (CFL) or a light emitting diode (LED) while the energy to do so is generated by a string of solar cells, called a solar panel, exposed to sunlight. This energy, generated during sunlight hours, is stored in a battery to be used at night. LEDs are the latest development as a source of light. Therefore the cost and performance of two solar lanterns, one based on a CFL and the other based on an LED, have been studied and compared to determine the better device for low-level lighting in the future. The comparison is based on lumens/watt (lm/W) output of the device. It has been found that the LED- and the CFL-based system cost almost the same if they are used to replace the hurricane lantern which has a light output of 40 to 50 lm. The life of the former is more, typically 10,000 to 50,000 hours with luminous efficacy of 47 lm/W, and its driving and control circuit is less complicated than that of the latter. The luminous efficacy of the latter is slightly higher, 50 to 60 lm/W, and it has a life span of up to 15,000 hours. On the other hand, LEDs are available from powers ranging from a few mW to 3 W, enabling lower-illumination lanterns to be constructed as an almost exact replacement of the hurricane lantern. However, at higher levels of illumination the CFL is still a cheaper source. The electrical efficiency of the circuit used with the CFL is about 82% whereas that used with the LED is 69% since it is based on an analog constant current generator. The efficiency of the latter can be improved by using a switch-mode constant current generator.