Solar streetlights are efficient and cost effective

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Manufacturers now offer solar powered CFL and LED streetlight solutions with customised features, based on local requirements and solar radiation levels

Solar Street Lights

By EB Bureau

Monday, October 22, 2012: The solar streetlight systems domain holds vast untapped potential, particularly in the rural areas, where grid connected electricity is not accessible. The government also offers incentives to boost solar streetlight installations. The market for solar streetlight systems is, therefore, expected to grow at a CAGR of 37 per cent by 2014, according to a report by RNCOS, an industry research and consultancy firm.

With an array of products available in the market, manufacturers are now offering their products with innovative and customised features, based on local requirements. These include customisation in the lux level, colour index, luminaire aesthetics, etc. Solar streetlights are usually chosen depending on the applications and location of installations.

A solar streetlight system includes the solar photovoltaic (PV) module, a tubular plate battery with battery box, and a charge controller-cum-inverter. Presently, there are three types of installations available:

LED based solar streetlights from Gautam Polymers
LED based solar streetlights from Gautam Polymers

a) Standalone DC operated solar streetlight (each with its own charge controller, solar panel and battery).

b) Standalone AC operated solar streetlight (each with a solar panel, charger, inverter and battery). Each standalone streetlight has its own solar panel and is independent of other lamps.

c) Centrally operated solar streetlights. These could be either AC or DC operated, and have a common solar panel installation with charger, inverter or battery bank. In this installation, a separate panel is mounted for a group of streetlights that are connected to a central power source.

The latest in the market

CFL based solar streetlights and LED based solar streetlights are currently popular in the market.

Solar streetlights from Saur Oorja
Solar streetlights from Saur Oorja

Compared to incandescent lamps that give the same amount of visible light, CFLs use one-fifth to one-third the electric power, and last eight to 15 times longer. With improved phosphor formulations, there has been an improvement in the perceived colour of the light emitted by CFLs. They radiate a spectral power distribution, which is different from that of incandescent lamps. However, CFLs contain mercury, which is a hazard for the environment when these bulbs need to be disposed of. This has lowered the popularity of CFL based solar streetlights.

On the other hand, LED lighting technology is ideally suited for solar powered lighting systems, as LEDs have low power consumption and can be customised to suit a low voltage DC power requirement. It offers more accurate colour rendering and also gives an instant start. Unlike high density discharge (HID) lamps, which take time to heat up once switched on, LEDs turn on instantly. Also, LED lighting systems have a lens on the LED array, which is designed to focus its light in a designed beam pattern. This is an advantage compared to traditional HID streetlights, which typically have a reflector on the back side

Solar streetlight from Solar Bio Tech

of a lamp, which causes a high percentage of light wasted above the horizontal line, resulting in light pollution in the air and the surrounding environment. By using LED lighting technology, energy consumption comes down by 50 per cent while maintenance costs too get lowered.

Gautam Polymers offers both CFL and LED solar streetlights under the brand name Solid Solar. Its solar LED streetlights are in the range of 8.5 W, 12 W, 24 W and 36 W, while its solar streetlights are in the range of 11 W (CFL) and 36 W (low pressure sodium or SOX lamps). These lights come with an unbreakable IP 65 casing, which is a highly protective polycarbonate casing, designed to protect the light fixture from dust and water, and allows safe routing of power.

Manufacturers have embarked on innovative mechanics and aesthetic designs to make streetlights more suitable to the requirements of customers. Some of the latest innovations from manufacturers provide LED street light with integrated solar charge

Solar powered LED Streelights from Promptech
Solar powered LED Streelights from Promptech

controller within the LED light. This reduces failure of charge controllers and also reduces additional wiring costs required to connect charge controller to luminary. Earlier, the charge controllers were external and would get damaged regularly due to exposure to the atmosphere.

Promptec’s latest innovations includes providing LED streetlight with integrated solar charge controller within the LED light. Also, the company has developed functionality to dim the solar lights during the low usage hours say 12 midnight to morning 4 am. This control can be set as per customer requirement. This saves the system costs and makes the solar streetlights much more affordable. It has developed hybrid solar streetlights which charge using AC power when there is low sun light or failure of battery power.

Kotak Urja offers streetlights that automatically operate from dusk to dawn, with appealing aesthetic luminaires and reliable MOSFET based electronics. The lamp is protected with pre-heating, sturdier mechanical structures and a battery box. These lights

Philips streetlight

have an LED source with a photometric design for rectangular beam pattern, which offers high intensity, high uniformity and glare-eliminated light. They offer a high colour index (>75) with tremendous energy saving compared to traditional lamps. These lights can be installed with both DC/AC type of installation for easy adaptation to standby and centralised modes.

Saur Oorja Solutions offers solar streetlights for foggy conditions. It also provides a power backup option of up to five days in case of bad weather conditions. Its entire solar agricultural light system is weather-proof and maintenance free—in the case of both its pole and non-pole versions.

With sustainable LEDs, Choice Computech offers a perfect light that matches the sensitivity of the human eye in the evening and night. This requires less energy as compared to conventional lamps, while at the same time gives better visibility. With a lumen ranging from 1250-2700, this LED streetlight offers a range of 30 W to

Amit Agarwal, managing director, Solar BioTech Inc
Amit Agarwal, managing director, Solar BioTech Inc

100 W. This comes with an aluminium die cast case and an IP 65 protection, hence it is a waterproof streetlight which also offers protection against high and low voltage fluctuations. With lighting efficiency of 110-120 Lm/W and a beam angle of 120 it comes with an inbuilt reflector that offers better light dispersion.

Philips has developed an efficient and cost effective solar powered LED street lighting solution. Philips’ Solar Gen2 innovation has been developed together with NXP Semiconductors. Solar Gen2 allows a lamp post spacing of up to 50 m, much wider than what is possible with other solutions, the company claims. Solar Gen2 can supplement the capacity of the conventional electricity grid. A further benefit is that it is supposedly ‘future proofed’ by the inclusion of the Philips LEDGINE, which allows LED modules and drivers to be simply replaced and upgraded, over time, as they get obsolete.

DK Varshnei, director, Saur Oorja Solutions Pvt Ltd
DK Varshnei, director, Saur Oorja Solutions Pvt Ltd

Tata Power Solar Systems’ solar powered LED streetlight—the Solar iBEAM LED lighting—is a standalone system designed for outdoor applications. The efficient use of materials has enhanced its performance, resulting in longer lasting LEDs, and it is an ideal application for campus and village street lighting. The system is provided with automatic sensors and a battery backup for dusk to dawn operation. These streetlights come with highly efficient mono/multi-crystalline silicon cells, designed to withstand tough environment conditions. Some of its other features are over charge and deep discharge disconnects, short circuit protection for the lamp, battery reverse connection, etc.

Solar BioTech Inc offers LED

powered solar streetlights in the range of 8 W-120 W with colour temperature 5000-6500 K and luminous efficiency of 100 lm/W. With an operating temperature of -30° to 60°C and IP rate 65, it comes with an automatic intelligent controller which has a light sensor which automatically switches and built in timer. Its solar panels offer a life span of 20-25 years.

It also provides protection for batteries against over charge and over discharge and over current protection.

Kiran Moras, director, Promptec Renewable Energy Pvt Ltd
Kiran Moras, director, Promptec Renewable Energy Pvt Ltd

How to choose a solar streetlight

Local solar radiation levels are a very important factor influencing the accurate design of solar streetlights. Hence, the particular country, state or even city for which the streetlights are being selected, is a very important factor. Different places have different solar radiation hours (peak sun time). The design of the solar panel and battery for the solar LED street lighting system depends on the peak sun time.

The intensity of light required is another important factor that should be considered. Also, one should decide on the accurate lighting time required in the night. Based on the hours required, the design and configuration varies. Also, the light source used should be the most efficient, that is, one that consumes the minimum energy and wastage.

The batteries used should be of the delayed discharge variety with more charge discharge cycles. The height of the streetlight pole is also an important factor, as a higher pole will require a stronger light source (LED) to illuminate the road.

Shubhra Mohanka, director, Gautam Polymers
Shubhra Mohanka, director, Gautam Polymers

Another important factor that consumers should consider is the maintenance of these streetlights; this is something that most people do not take into account, leading to the misconception that ‘solar streetlights fail easily’. Ensure that the facilities and resources of the vendor include an optimal solution so that the maintenance is easily taken care of. The company from which the light has been purchased should provide onsite services for the lights installed.

While keeping a check on these points, one should also compare the power saving aspects of LEDs vis a vis the AC mains streetlights. Go in for a solution based on the budget, with minimum wastage of energy and low energy consumption, ensuring value for money in the long term.

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