Let solar lanterns light up thousands of households

By Srabani Sen

With less technological advancements in solar lanterns, manufacturers are banking on innovative products that address unique requirements

Wednesday, May 09, 2012: Sudeep Mondol, a resident of Kakdwip, a small town in southern West Bengal, was overwhelmed to see his hut lit up after 20 years. Mayawati Devi can now cook in a well lit room in a village in Cuttack district, which now has access to light even after sunset. Shailaja does not have to inhale toxic fumes from kerosene lanterns anymore as she now uses a solar lantern to study. Her village, near Bengaluru, does not have access to electricity.

This change in the lives of India’s rural people has been made possible by the amazing solar lanterns made by numerous manufacturers across the country, and distributed under various government and private programmes. Although solar lanterns and lamps are successful across India, the National Solar Mission mainly focuses on generating electricity from solar energy and not on products like solar lanterns, which have an efficiency level of about 88-90 per cent, as these rely entirely on the charge that comes from the cells.

Targeting a huge potential market for solar lanterns—about 500 million people in India’s villages still have no access to electricity—manufacturers are coming up with innovative designs within the limited options of the two types of lanterns. “Usually, only two types of lanterns are commonly sold in the market—the 7 W compact fluorescent lamp (CFL) based lantern with a 10 W module and 12 V 7.5 ampere hour (Ah) battery; and the 3 W light emitting diodes (LED) based lantern with a 3 W module and 6 V 4.2 Ah battery,” explains PC Biju, manager, Sales and Marketing, Emmvee Photovoltaic Power Pvt Ltd. While the first type has been approved by the Ministry of New and Renewable Energy, demand for the second type is very high due to its low cost.

What’s new in the market

Since there has hardly been much advancement in the technology used in solar lanterns, manufacturers bank on innovative features based on the applications. Let’s take a quick look at some of the new models in the market:

Waterproof outdoor solar lanterns: Outdoor solar lanterns are designed to function in rugged environments and hence have tough bodies. These lanterns can also be hung and are waterproof. Chennai-based Anuman Solar and Nagpur-based Shyama Packaging are among many firms that offer a large variety of outdoor solar lanterns, which are quite in demand. The prices of these lanterns range from Rs 399 to Rs 1699.

Rotatable solar lanterns: These solar lanterns can be rotated 180º and 360º, and usually come with both light sources—CFL and LED. Suitable as camping lights, these can be easily powered by either sunlight or a PC/laptop. These lanterns have nine hours of bright light and 18 hours of ‘half light’.

This August, Sujana Energy Ltd has developed one such solar lantern. “We have designed this lantern with an efficient casing for maximum 360º light output, and it has built-in features like a mobile charger and four lighting modes—bright mode, study mode, emergency mode and bed light mode,” explains Sundeep Mengarthy, general manager, LED business, Sujana Energy Ltd. SE solar lanterns come with both tabletop mounting and hanging facility, with a switch mode power supply (SMPS) charger (in addition to the solar panel) to charge the battery when access to solar power is limited. “For the safety of the lantern, we have also included a battery level indicator, microcontroller based electronic circuitry, overcharge protection and deep discharge protection facilities, apart from panel mounting hangers,” he adds.

Moser Baer’s SL04 also comes with LED bulbs with 360º light output, dual modes of charging (AC mains as well as solar charging options) with an inbuilt portable FM radio and a multi-mobile charger (Nokia, Samsung, Blackberry, Sony, LG, Motorola, etc). It has a battery backup of six hours on full load and 10 hours on dim mode.

Solar lanterns with AC charging facility: These solar lanterns, also called hybrid lanterns, come with a CFL or LED lighting source, with the AC mains charging facility. This means, they use both solar energy as well as conventional power for charging the battery. This gives buyers the option to select the source of energy at their disposal. Aditya Solar Energy Pvt Ltd has launched the Kohinoor and Aditya Jyoti (MNRE approved solar LED lanterns). Says G Satish Kumar, director, Aditya Solar, “The biggest advantage of this lantern is that it is totally pollution free, with five hours of backup. These lanterns come with high efficiency LED driver circuits, IEC approved solar modules, and all the necessary protection like reverse polarity, battery deep discharge and overcharge indicators, battery charging and battery low indicators, etc.

”Kotak Urja has developed its Sparkler solar lantern with a dual charging system (solar and AC charging options). This LED lantern is light-weight and rugged, with long hours of backup. The lantern is built for safety with a steel grill covering the acrylic and rubberised base to absorb sudden shocks, in case of a fall or the lantern being dropped. Even the electronic circuitry and battery are protected.

BPL Techno Vision Pvt Ltd launched an innovative rechargeable LED based solar lantern lighting—BPL SL1300. This solar lantern is affordable and is equipped with a solar charger and uses BPL’s Q Tech technology, which allows charging even in fluctuating power and has an AC mains charging range from 90 V to 260 V. It also has a dual charging mode—AC charging using Q Tech technology as well as charging through a solar panel. While AC charging takes four hours for five hours of lighting, charging through the solar panel can provide 3.5 hours of light. This model is priced at Rs 1299.

Multi-purpose lanterns with added features: Going by the trends, manufacturers now offer multi-purpose lanterns catering to the specific needs of spread light, focused light, hanging lights or torch lights. Sometimes, all these requirements can be served by one single lantern. Gautam Polymer Group has launched the Solid Solar brand of lanterns, which are multi-purpose, have zero tension light and run for 12-14 hours with a single bright light, whereas with a double bright light they run for 6-7 hours at 3 Wp.

With an efficiency of over 80 per cent and luminous performance of 80-100 lumen per watt, this multi-purpose lantern also has an additional mobile charger connection. “Every year, we upgrade our products—earlier we had a switch button on the lanterns; now, we use microcontroller based buttons,” says Shubhra Mohanka, director, Gautam Polymer Group. In April 2012, the company launched the Shivling CFL lantern.

Many of the solar lanterns feature mobile charging sockets (USB type), battery level indicators (as in mobiles) and FM radio options. Kotak Urja has recently filed a patent for one of its products, which apart from carrying all the features just mentioned, also has a projector and fake currency detector.

Solar hawker lights: These solar lanterns are designed for hawkers residing in rural as well as urban areas. They come with a 5 W CFL light, and offer illumination for longer hours than a kerosene lamp. These also come with the mobile charging facility and offer lighting for up to 8 to 10 hours after full charge. Bhambri Enterprises has launched one such lantern, which is not only eco-friendly but pocket-friendly as well. These hawker solar lanterns have 6 W super bright LEDs with high lumens. “This lantern comes with 6 hours of lighting and the LED version costs Rs 3500, ensuring ROI in 3-4 months,” says Ruchi Bhambri, director, Bhambri Enterprises. These solar lanterns cost between Rs 2500 to Rs 3500, and come with a battery and charge controller housed in a cabinet at the base of the lantern.

Solar lanterns with different light source: CFL and LED bulbs are replacing conventional incandescent bulbs in solar lanterns. Efficiency here is measured in terms of the power consumed—CFL and LED bulbs with lower power ratings produce more light. These bulbs have a longer life than ordinary bulbs. While a standard CFL has a life of about 6000 hours and can spread the light upwards as well, the more advanced LED lights run for almost 50,000 hours.

Rashmi Industries offers a solar lantern with a 7 W CFL, which provides a light output of 52 lumens per watt, equivalent to that of a 40 W (9 lumens per watt ) bulb. This solar lantern has a built-in detachable electronic circuit with an inverter and charge controller. A highly efficient two-step charge controller protects the battery from deep discharge and overcharging.

Another domestic manufacturer, Saur Oorja, offers solar lanterns with fluorescent tubes, LEDs and CFLs, with a battery power ranging from 1.3 Ah to 7 Ah. “These have an automatic lighting up device in case of power failure, and a built-in electrical charger with overcharge protection for safety and long life. These lanterns are available with both amorphous and monocrystalline panels,” informs DK Varshnei, director, Saur Oorja.

Choices in solar panels: Different types of solar PV panels can be used to power solar lanterns—crystalline and amorphous (thin film). Crystalline panels take up less area than the amorphous panel for the same amount of energy produced. However, crystalline panels do not perform satisfactorily under cloudy or not-so-bright conditions, when compared to amorphous panels. The choice of the panel depends on the location of the lantern as well. Typical ratings of the solar PV panel range between 8 Wp to 10 Wp.

Different types of batteries: The size or capacity of a solar lantern’s battery is determined by Ah—the greater the Ah of the battery, the longer the bulb can be used. These lanterns usually have a 6 V/4.5 Ah SMF lead acid battery. Nickel metal hydride, nickel cadmium and valve-regulated lead acid (VRLA) batteries are the three commercially available alternatives being used in lanterns.

BPL Techno Vision has launched a rechargeable LED lantern called Chirag. It uses a 3.3 V and 1600 mAh battery. Unlike the 8-12 hours of charging required by some batteries, this lantern requires only 4 hours of charging and runs for more than 5 hours.

The backup offered by some of its lanterns is as long as 14 hours. The Jumbo LED and Wonderlite CFL solar lanterns by Kotak Urja not only offer long battery backup but also ensure the lantern is safe. These lanterns are available in both bright mode and night mode (dim light).

How to choose a solar lantern

Although a solar lantern is a simple device, buyers have a number of doubts while procuring a solar lantern, particularly due to its high price, compared to kerosene lamps. Also, with an array of products available in the market, a buyer might end up buying a low quality product or one that might not be worth the money spent. Thus, a few things should be kept in mind while procuring solar lanterns.

Location of the user: Users in a bright, sunny region with a shadow-free location in a place like Rajasthan could opt for crystalline solar panels. But if the location is somewhere in a cloudy region that has fewer days with clear sky, such as in the north-eastern states, choosing an amorphous solar panel lantern would be better.

Number of hours of functioning: Buyers should check whether the lantern meets their requirements. The functioning hours of the lantern should be calculated before making the purchase. The buyer should also calculate the operational (backup time) hours of the lantern. If the user needs light for fewer hours, then a small battery can be used, typically a 4.5 Ah. For more than 6 hours, a 7 Ah battery can be chosen. Of course, the number of hours would depend on the power rating of the light source. If a CFL is used, the lantern would run for fewer hours, and if LEDs are used, the lantern will function longer.

Choosing the right battery: It is important to know the type of battery required before buying a solar lantern. “Often, the batteries fail either due to improper usage or poor quality. The safety of the battery is decided by the quality of the battery itself. Tubular batteries are best suited for solar lanterns as they have a longer life,” says Raghunandan.

The right light source: The panel and battery in a lantern constitute 70 per cent of its total cost. “Choosing the correct light source, which will increase the life of the panel and battery, is important while buying a lantern. This will not only consume less energy but have a longer life as well,” says Shubhra Mohanka.

Price: A buyer should verify the price of the product before making a final call. However, placing a greater value on the price as compared to the features in the lantern can sometimes mislead a buyer, as the price of the lantern is highly dependent on the cost of the panel (crystalline or thin film), the light source used (CFL or LED) and battery backup (hours of functioning). “Buyers should not get attracted by the low cost of a lantern; rather, they should look at the quality of the product, as buying a quality product gives benefits in the long run, and saves you from the hassle and cost of repairs and maintenance,” says G Satish Kumar.

Credibility and reliability: Buyers always speculate about the quality of the product and the guarantee that it offers. Before settling for a product, study the various other options available in the market. Unfortunately, there isn’t a reputed and trusted accreditation body to certify solar products. However, a buyer should look for suppliers with a local service support system.

Protection factors: According to Sundeep Mengarthy, a buyer should also look at the various safety measures like overcharge

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A costly affair!

The cost of solar lanterns depends upon the type of the lantern, its light source and battery. It can vary from Rs 350 to Rs 3500, or even more. But when compared to the cost of using kerosene lanterns, solar lanterns turn out to be cheaper. “Besides, cost recovery can occur within 3-4 months,” says Ruchi Bhamri.

Although a solar lantern lasts for 10-20 years, the poor cannot afford a 10 year investment. They don’t even qualify for loans.

However, Shubhra Mohanka feels that price is not a major issue for the buyers if they are satisfied with the quality of the product. “Moreover, it is expected that the price of these solar lanterns will decrease further, with the drop in PV module costs and increased R&D leading to efficiency improvements. Also, the government has come up with various incentives and subsidies through multiple schemes to ease the financing problems for solar lanterns,” she explains.

Solar lanterns can be procured on rent too, like what Gautam Polymer offers. With a minimum charge of Rs 2 per day, people can rent a solar lantern and return it once they have finished using it, informs Shubhra Mohanka.

Electronics Bazaar, South Asia’s No.1 Electronics B2B magazine