Solar Lanterns: Lighting up lives, the green way

By Richa Chakravarty

Sunday, June 12, 2011: Solar lanterns recently made a prestigious entry into the British Museum in an exhibition called, ‘A history of the world in 100 objects’. What made it feature in the list? Well, the items in the above mentioned exhibition represent technologies that are changing the world, and a solar lantern is one such innovation that is making a name for itself in history. This clean and safe device that is powered by alternate energy is creating waves in the off grid segment. Owing to its multiple features, affordability, portability and user friendly applications, solar lanterns are registering maximum demand in India. More so because in a country like India that faces severe power deficit, solar lanterns come as a respite. Over more than 23 million households in India still do not have electricity, but solar lanterns have solved this problem to a large extent, and this market is projected to grow at a CAGR of 40 per cent till 2012.

 WHAT’S NEW IN THE MARKET

Solar lanterns require a light source and are made up of solar panels, a battery and a charge controller. The circuit is the hub of the system, through which the photovoltaic (PV) panel, battery and the light source are connected. It also indicates the battery charging and discharging status, reminding users when to switch on for charging. However, while talking about new features in this segment, innovations are entirely need based, and manufacturers today focus on making the lanterns more efficient and as per customers’ requirements. These innovative features are based on light brightness (light source), number of hours of use, weight, power consumption and other additional features.

Light sources based on different technologies

Being more energy efficient, compact fluorescent lamps (CFL) and bulbs made of light emitting diodes (LED) are replacing the conventional incandescent bulbs. Here, efficiency is measured in terms of the power consumed—CFL and LED bulbs with lower power ratings produce more light. These light sources have a longer life than incandescent 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 and consume much less power.

The Indian market is flooded with lanterns of varying lumen levels manufactured by domestic and foreign companies. With a large number of players mushrooming, the options for a buyer are endless. With its focus on manufacturing solar water heaters and solar lanterns, Rashmi Industries offers a four pin 7 W CFL, which provides a light output (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 over charging.

Yet another domestic manufacturer, Saur Oorja Solutions (P) Ltd, offers seven different types of solar lanterns with fluorescent tubes, LEDs and CFLs, with a battery power ranging from 1.3 to 7 ampere hours (Ah). It has 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 monopoly crystalline panels. These solar lanterns also have options for mobile charging, night lamp or even an additional solar fan.

Choice in solar panels

The solar PV panel is the main energy source of the solar lantern. The panel comes in a variety of technologies such as crystalline and amorphous (thin film) panels. The crystalline panel occupies less area than the amorphous panel for the same amount of energy produced. Moreover, crystalline panels have higher temperature coefficient, which makes the module perform differently in different weather conditions. The choice of the panel depends on the location of the user. Typical ratings of the solar PV panel range between 8 Wp to 10 Wp. “The panel and battery in a lantern constitute 70 per cent of its total cost. Choosing the correct light source that 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 Gautam Mohanka, director, Gautam Polymer Group. The company offers both CFL and LED lanterns with various additional features loaded onto them. Its ‘Multi Noorjahan lantern’ model serves various purposes—spread, focused, hanging light and a torch, and runs for 12-14 hours at single brightness and 6-7 hours at double brightness.

With different types of batteries

The battery’s size or the capacity of a solar lantern is determined by Ah. The greater the Ah of the battery, the longer the light source will be in use. 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 three commercially available alternatives that are being used in the lanterns.

As the battery is the life of the lantern, much attention is being paid to it. BPL Techno Vision Pvt Ltd (BTVL) recently 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 other batteries, this lantern requires only 4 hours charging and runs for more than 5 hours. This innovative lantern uses ‘Q Tech’ technology with white LEDs, and is designed to provide 360 degree illumination.

“It is important to know the battery type before buying a solar lantern,” warns Raghunandan, vice president, Engineering, Kotak Urja Pvt Ltd. “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, and the quality of the battery is decided by the use of virgin grade lead, good quality cell separators, good plastic case and good regulators. These parameters will increase the lifecycle of the battery,” he adds.

The solar lanterns offered by Kotak Urja use SMF batteries which are manufactured using fifth generation manufacturing techniques offering higher battery lifecycle. The backup offered by some of its lanterns is as much as 14 hours. The ‘Jumbo LED’ and ‘Wonderlite CFL’ solar lanterns by Kotak Urja not only offer long battery backup but also provide safety to the lantern. These lanterns are available in both bright mode and night mode (dim light). People often use lithium ion batteries as an option for lanterns but the cost of replacement is very high and the availability of lithium batteries is not there in small towns and villages. So the best option is to use SMF battery due to its easy availability. The lanterns whose repair and replacement is possible in the local market are the most practical ones, says DK Varshnei, director, Saur Oorja Solution Pvt Ltd.

Multipurpose lanterns

With the right use of the light source, manufacturers today offer multipurpose lanterns catering to specific needs like spread light, focused light, hanging lights or torch lights. All these requirements can be served by one single lantern. Gautam Polymer Group, under its brand name ‘Solid Solar’, has recently launched a multipurpose lantern with zero tension light and it runs for 12-14 hours as a single bright light, whereas with double bright light it runs for 6-7 hours at 3 Wp. With efficiency of more than 80 per cent and luminous performance of 80-100 lumens per watt, this multipurpose lantern also has an additional mobile charger connection.

Hybrid lanterns

The market also offers hybrid lanterns that use both solar energy as well as conventional power for charging the battery. This gives the buyers the option to select the source of energy available. Based on a recent market survey conducted by Kotak Urja, it developed a solar lantern called ‘Sparkler’ with a dual charging system (solar and AC hybrid charging options). This LED lantern is light weight, rugged and capable of long hours of use. The lantern is built for safety with a steel grill covering the acrylic and rubberised base to absorb sudden shocks in case the lantern is dropped. The electronics are built with safety features to protect the lamp and battery from failure.

Added features

Many of these basic lanterns are not just portable and light weight but also have additional features like 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 goes beyond lighting to offer mobile charging, radio, projector, fake currency detector, etc.

How to choose a solar lantern

Shares DK Varshnei, “There are many doubts that cloud a buyer’s mind when procuring a solar lantern, particularly with regard to the high purchase price (compared to kerosene lamps), the risk of theft of solar panels, the repair and maintenance of equipment and the uncertainty regarding the payback period of the investment.”

Also, with a large number of players in this segment and with an array of products available in the market, a buyer might end up purchasing a low quality product or one that might not offer the best value for money. 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 like Rajasthan may opt for crystalline solar panels. If the location is in a cloudy region with fewer number of clear days, such as the northeastern states, amorphous solar panel lanterns would be preferable.

Number of functioning hours: Buyers should check whether the lantern meets their requirements. Calculate the functioning hours of the lantern and accordingly invest in it. Buyers should also calculate the operational (backup time) hours of the lantern. If users need light for fewer hours, then typically, a small 4.5 Ah battery can be used. For more than 6 hours, a 7Ah 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 then the lantern would run for fewer hours; if LED clusters are used then the lantern will function for more hours. “While talking about the battery, buyers should remember that a sealed maintenance free battery contains lead, which requires safe disposing methods after its lifecycle. It is suggested that the customer looks at a company that is known in the market for its recycling arrangements for the battery,” informs Raghunandan.

Price: As far as the price of solar products is concerned, it is expected to decline with the further decrease 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 lighting systems.

A buyer should verify the price of the product before making a final call. Weighing the price against other additional features in the lantern can sometimes be misleading, as the price of the lantern is highly dependent on cost of the panel (crystalline or thin film), the light source used (CFL or LED) and battery backup (hours of functioning).

“Prices as such are not a major issue for buyers if they are satisfied with the quality of the product. Today, solar lanterns are available for as little as

Rs 500. But again the prices vary with quality and also with the other additional features being added to the basic lantern. These feature packed lanterns can range anywhere between Rs 1000 to Rs 3500. We also offer the renting option—with a minimum charge of Rs 2 per day, buyers can rent a solar lantern and return it once there is no longer any need for it,” informs Gautam Mohanka.

Credibility and reliability: While buying a product, a buyer always wonders about the quality of the product and the guarantee that comes with it. Before settling for a product, a buyer has to study the various options available in the market. An independent organisation that can accredit the solar products for their quality and safety, is absent. However, a buyer should look for suppliers who have local service support systems.

How to procure solar lanterns

Limited outlets for procurement is a hurdle faced by buyers. Though there are a large number of players in this segment, the main users in this market are in rural India, who still do not have enough information regarding how to procure these solar products. In order to have a better reach in rural areas, industry players and the government will have to make more efforts in this domain.

However, with the Light a Billion Lives (LaBL) programme set up by The Energy and Resource Institute (TERI) and the village level entrepreneurs (VLEs) model catching on, solar lanterns are slowly gaining popularity in remote villages.

“The government has installed Akshay Urja shops where a buyer can procure solar products, but these products are costlier than those available in the open market. Thus, a buyer generally ends up buying solar products from private players. The sole purpose of the government running these outlets to ensure benefits to both manufacturers and end users, has not worked out,” says D K Varshnei.

Need for standardisation in solar lanterns

Currently, there have been no standards set in India by which the quality and efficiency of solar lanterns can be tested. In this situation, manufacturers—big, medium and small players—are making solar lanterns of varying quality, leaving the buyers in a dilemma over the products’ credibility and reliability. Hence, an effort should be made by the government to introduce star ratings for LED products. The quality, reliability and durability of the white LED based solar lantern needs utmost attention. Basically, there is lack of data about the quality and performance of LED based solar lanterns. However, there are Ministry of New and Renewable Energy (MNRE) specifications set for both LED based and CFL based solar lanterns but manufacturers are open to develop only kind of configuration.

The distinction in the quality of these products is not discernable to the buyers, since there is no visually recognisable feature to distinguish them.

The quality of the products can be determined based on the following basic minimum parameters:

• Luminous efficacy
• Luminance and glare
• Lighting distribution characteristics
• Light output over a single discharge cycle
• Hours of useful luminance delivered from a fully charged battery
• Persistence of battery capacity
• Performance of charging circuit
• Charging efficiency
• Overall system efficiency

Players who offer solar lanterns

The names of the companies are in alphabetical order

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