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Solar Lantern

A solar lantern is well-known example portable stand alone solar electric system. It consists of all necessary components required for a standalone solar electric system in a single casing except the solar PV module. It is consists mainly a lamp, a battery and an electronic control circuit in a single casing. The solar module is a separated past of the lantern. This PV module has to be connected with lantern’s battery terminals for charging purpose. Now days solar lantern are very popularly used for both indoor and outdoor purposes.Casing of a solar lantern may be mode of either metal, plastic or fiberglass. Battery, charging and control circuit are placed inside the casing with proper memer, so that inside space of the casing can be properly used. On the top of the casing there is a lamp holder mounted at centre. One CFL of required rating is attached with this holder.

The lamp is covered from all sides by transparent glass or fiberglass. This cover is transparent from all sides, hence solar lantern can emit light in all directions i.e. 360o of light illumination. The top of the transparent hollow cylindrical lamp cover, there is one top cover which is not transparent and generally made of some material by which casing of solar lantern is made. Hanger of the lantern is filled with the top cover. There is a plug point and charging discharging (ON) indications on casing. For changing purpose, wire with socket comes from solar module which placed under sunlight is plugged to the plug point on the casing. There are different models of solar lantern, but normally battery capacity of a solar lantern is 12 V 7 Ah. CFL lamp used in this system is normally either 5 W or 7 W. The PV module used for charging solar lantern is from 8 Watts peak to 14 Watts peak. A table showing different configuration of solar lantern as per MNRE specifications is given below

Model Lamp (CFL) Battery PV Module
I-A5 W12 V, 7 Ah at 20oC8 to 99 Watts (Peak)
I-B5 W12 V, 7 Ah at 20oC8 to 99 Watts (Peak)
II-A7 W12 V, 7 Ah at 20oC8 to 99 Watts (Peak)
II-B7 W12 V, 7 Ah at 20oC8 to 99 Watts (Peak)
The lumen output is generally in the range of 230 ± 5 % for 7 W CFL. solar lantern

The Components of Solar Lantern

Solar Module or PV Module

Generally solar module used for charging a single solar lantern has rating of 8, 10 or 12 Watts (Wp). The module is normally kept on rooftop at most tilt angle for which the module gets maximum intensity of sunlight, for maximum duration. The lanterns are connected to module through wire socket which is kept in room or other places. But sometimes users do not install solar module at roof top instead they like to keep the module in sunlight in daily basis.

Battery

Normally maintenance free sealed dry type lead acid battery of tabular shaped with 12 V 7 Ah capacity is used for solar lantern.

Inverter

For CFL lamp one inverter is required to make the battery output of AC. The inverter should have at least 80 % efficiency.

Protection and Indication System

The lantern has electronic circuit to provide cut off provision to prevent excess charging or over discharging of the battery. An electrical fuse is also provided with the system to protect it from any short circuit fault. Two Light Emitting Diodes ( LED ) are provided on the casing for charging and deep discharging states of the solar lantern.

LED Based Solar Lantern

Solar electricity is expensive. The availability of solar electricity in portable solar module is not large it is small. So, LED has become quite suitable light source in portable handy solar lantern. LED is best suited for small house hold solar lantern because of its small electricity consumption. Although LEDs are manufactured in different colours but white colour LED is most suitable for solar lantern.

As the electricity consumption sate of LEDs is quite low, the power ratings of the PV module used to charge the lantern is also low and if the peak power rating of a solar module is more than 2.5 W at 17 V it can be suitably used to charge a LED based solar lantern. Became of low power consumption, battery of this lantern is also smaller and lower rated. A 2.3 Ah 12 V at 20 oC sealed, maintenance free dry type lead acid battery can be suitably used for LED solar lantern. More than 30 lumens per Watt 5 mm white LED is most suitable for LED based solar lantern.

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