It is well known that Solar technology is used for various applications and to provide power generation source for low power consumption applications such as solar lighting.
The solar lighting system typically consists of following components ;
- Solar Photovoltaic modules or cells (depending on the power rating)
- Solar controller
- LED / lighting controller
- Luminaire (or some light source. Nowadays usually LED is the most popular choice)
- Pole (only in case of street light or traffic warning lights)
- Protective functions such as battery deep discharge protection
- Cabling and Other minor accessories
Types of solar lighting systems
Solar lighting can be used in following ways :
- Solar Lanterns
Solar lanterns have been one of the early uses of solar applications. Specially of interest is the benefit they deliver in terms of replacement of kerosene lanterns or providing the ability to have lighting in rural or remote areas . They are one of the cheapest of all solar applications and are very commony used in rural and tribal areas. Usually it consists of a small solar panel and a lantern. This lantern houses the lighting (LED or CFL) , a small battery, the solar controller and some switches, indicators. The solar panel is connected during day hours to charge the battery, so that it can be utilized in night for giving illlumination. Although solar lanterns are primarily targeted at the poor, but sometimes they are also used by campers / bikers / etc. Usually they require about 6 to 8 hours of charging in daytime to deliever the same duration of lighting.
- Solar flashlight / solar torches
Solar torches are basically like normal flashlights but with solar cells in-built and also a better and heavier battery pack. They are a very easy solution for people who have to move around and need a portable light source. With the advent of LED technology solar flashlights are an option for campers, hikers, etc. However the high cost as compared to a normal flashlight turns many possible users away also.
- Solar Street lighting
Solar street and pathway lighting is one of the very widely used application in the lighting segment. In fact with the advent of automatic dusk to dawn lighting it has become an ideal choice for deployment in various kinds of pathway, street , industrial, farmhouse, resort and other similar lighting requirements. This feature allows the lights to automatically switch on at dusk and turn off at dawn.
They consist of a number of items to create a complete lighting solution.
Solar street lighting can be implemented in 2 ways :
C1. Independent type / Decentralized solutions : In this case, each solar lighting system is a complete unit by itself. It contains a solar module, the Luminaire, a battery, a controller, the pole for holding the above items. Usually an independent type street lighting system works completely on DC voltage to avoid the additional inverter cost and also to avoid DC to AC conversion losses. They are ideal for situations where a new solar lighting solution has to be implemented. Or otherwise in cases where the distance between the power supply source and the required lighting location is very long (Eg. Farms / large resorts / farmhouses / etc)
They are available in power ratings starting from as small as 7w and going upto 70 to 90w. It is not recommended to use them for very high power lighting poles (Eg. Single pole with 200 or 300w luminaires) as the required solar panels and battery bank become too large to put on a single pole.
Commonly used pole heights in solar independent type poles are 4.5mtr, 6mtr, 7mtr, 9mtr.
C2. Centralized type : In this case the solar system is installed at a central / common location and the power generated from the solar system is fed to a selection of street lights. Usually in this case the power generated from the solar system is converted to AC. This AC power is then fed into a common distribution point from where the street lights are powered. The street lights used in this case are AC powered. This type of solution is more suited to locations which are already having light poles installed and wanting to power them from solar. It saves the cost of new poles, wiring, etc. Further it also has the convenience of being easy to mantain and clean, as the solar panels and battery bank are at a single location. But they are not suited for locations where the distance between lights is very long and requires the installation of new poles.
- Solar aviation / navigation lighting
There are many locations and sites which require lighting for critical or statutory application such as navigational lighting aids / marine lighting applications / tower top lighting or even aviation obstruction lighting. The conventional method has been to have a standard AC powered light installed here and then feeding it power from a UPS or other types of uninterrupted sources so as to ensure the lights continue to operate in case of any power outage or disruption.
Making use of solar powered lighting for such applications is a very ideal choice and completes the solution very well.
First of all it allows the installation of these lights at remote or far off places without having to create the other infrastructure for supplying power like a grid supply or a genset.
Secondly since the solar panels are able to charge the battery , sites with frequent power interruptions are ideal for such solutions.
With the advent of high power density and lower cost Lithium batteries, it is possible to have a long backup of as many as 10 to 18 days in the light itself.
Hence making these lights a complete unit by themselves.
With the advent of LED technology these lights have become more reliable and also very power efficient. Further the LED technology enables these lights have the facility to have different light emitting pattern as per site or the statutory requirements. For example some lights have as many as 200 or even more lighting pattern choices.
In fact with added features like remote control operation and programming, there is no need to even climb the tower top every time for any change in programming.
Since they have a solar panel in built, the batteries are able to get charged as soon as solar radiation is available.
Also as they are weatherproof and waterproof, there is no need to worry about placing them even in the harshest of weather conditions.
Even in hazardous cases such as chimney tops or cooling tower tops they bring the benefit of avoiding frequent human intervention.
These lights are available in different models which can cover distances upto 5 nautical miles.
In fact it is the right time for users (Eg. Telecom towers, marine navigation, aviation obstruction, building top, chimney top, cooling tower top, etc) to switch from sites with traditional lighting systems to such solar powered lights and take advantage of all the benefits.
- Solar traffic warning lights
Traffic warning lights or other kinds of highway marking lights are also a right candidate for shifting to solar. Because of the long lengths of cable required to bring power to these small power consumption lights, it is not suggested to draw the power cables. Also since these lights are now running with LED technology (DC power consumption) it saves on the conversion losses. Usually these units consist of a solar module, the lighting unit, battery bank, controller circuit, pole (for holding the solar panel, luminaire, battery, controller), wiring.
Solar powered traffic solutions are also ideal for urban or city applications where there is a frequent power outage or the power is unreliable. Because they are independently powered and operate on solar, the reliability of these lights is greatly improved.
It is suggested for government and civic bodies as well as highway bodies to start making use as much as possible of solar.
With such a wide variety of solar solutions to meet every kind of lighting solutions it is strongly recommended to go for solar technology for all kinds of lighting applications.
However , t is very important to choose the right model, solar module, vendor, battery, choose. Otherwise the product may not deliver the desired performance.