Solar Street Lighting

Solar  lighting industries is developing day by day, in a traditional way we know the street light are like the picture below.But now street lights are not the pole based sodium lights, technologies are changing and new new technologies are taking places .Now you will find every one has a smart phone ,even a small boy know how to play in smart phone. As the technology is getting smarter everything is getting smart, now we can run our entire house with a smart phone just you need technology with android application...Lighting Industries are drastically developed in last decades and they are continuing their good job. Before I go much advanced world of technology let me show you the obsolete street light system first.

Sodium Light

 Low/High pressured sodium street lights , we all know this as lamppost ,this is the most available street lights in every developing country , even in developed country you will find it . This lights are pressurized with sodium vapor and that is why you see a golden yellow light illumination from the lights...

Mercury Light

This lights are not self fueled, the grid line is the feeder, this lights quality are poor...they are built with ancient ballast  system and the power consumption is typically high for better lumen...this streets lights are heavy and hard to install and difficult for maintenance.This kind of lamps has color and light pollution like it does emit UV rays and which is not good for us...In 2015 the use of Mercury vapor street lamp are banned by European Union and in 2008 US banned the use of ballast which is a very necessary part of sodium street lights. The production cost also high and it has short lifetime too..If you put all the side effects in the bracket it is not any more efficient...

Solar Street Light (LED)

Solar Street lights is a new technology and it is increasing with a great speed . These lights are feed by the solar energy. The construction of this type of light is not complicated

 There are few part ..

1) Solar Panel

2) LED light post

3) Battery 

4) Controller

The construction is getting more  and more easier, it is getting more efficient..

The construction is like the left picture , Solar Panel at the top, after that is LED post, then Battery and charge controller..

But not every Street light manufacturing company produces street lights  the same way. Most outdated street lights are using separate part installation that's mean solar panel , Led lights and the battery has different location on the pole.

Traditional Solar Street Light

 This picture above demonstrating a old design of solar street system but this is the most used one for its better battery back up service...

But Technology is evolving , Now some manufacturing companies are making one built in solar led street lights...where Solar Panel , LED post, Battery , and controller is in one lamppost, no extra place for other parts, everything is at the top....

Integrated Solar Street lights

As you see in the left picture everything is in one lamp post , very easy installation and  maintenance...

The use of Mono crystalline cells for panel and Lithium ion battery for storage  make it very compact form of street lights.. 

But that's not all, this kind of street lights work with intelligence, how is that, answer is this type of integrated street light system has auto detecting sensors, like it can sense the ambient light intensity of the surrounding, so at the day time it senses the higher intensity of day light and keep the LED lights off, but at the evening when day light is dimming it automatically sense that and light the LED On..that's not all it also has motion detectors, if there is no person around it then it keeps the LED dimming but when someone pass through the lights it lights on the LEDs.

Configuration :  

Comparison with other street lights :

• Solar Street lights has the best efficiency then any other streets lights ...
• Sodium and Mercury vapor street lights create light pollution where solar street lights are pollution free.
• Solar Street lights are fuel cost free, and it doesn't require grid power...
• Solar Street lights are easy to install and detect problems..
• Solar Street lights has higher life time, manufactures give high warranties of the product
• Solar street light diminishes the use of ballast and higher power consumption..the maximum power consumption of the this lights are  LED 70W with a 90W mono crystalline panel...
• Solar Street lights are intelligent with the sensors, it can detect darkness and capable to run itself perfectly.
• Solar street lights can be monitored by Laptop or Smart phone just by using android apps.

All kind of facilities are integrated in Solar street light technology comparing any street lights available..\

Solar Street light design :

 

To design a solar street light system you need to calculate i) Road length & Width  ii) Solar Street light specifications iii) Time..

Let assume a project of 100m long, 30m wide road needs solar street lighting for 12 hours from 6:00 PM to 6:00 AM.

To design a Solar Street light  system you just can't grab your product and simply implement them, it is not very easy, but it is very long, complicated and heavy construction.. Every street light is over 70Kg~150Kg depending on their capacity, so it is not your solar panel which is a light weight product and you can do the maintenance when you want, this is very heavy you have to make sure it needs lower maintenance as possible in the future because you have to go through with a lot of things with that...

First step to measure Road parameters which is its length and Width, Why!

Street light placed on the road three way i) Side by Side ii) Front to Front iii) Zig Zag

 Benefit of every street light placement is different 

• Side by Side placement of street light will increase the luminosity area of the street by length.
• Front to Front placement of street light increase the luminosity area of the street by width.
• Zig zig placement of street light will increase the luminosity area of the street light both by length & width..

It is necessary to observe that there are no dark area in between the street lights placements for better road safety,  and the light intensity is very good both for the vehicle drivers as well as pedestrians.

Common theory about the street light :There are few you nee to know before design :

•    Lux of street light : Lux is the unit of luminosity area, it is actually lumen/square meter...it is very very important factor  you to understand  how you are going to place the street lights, in every street light's catalogue you will find it's light luminosity diagram where you will see at what height how much luminosity the street light can provide and how much percentage of concentrated lumen you will find area to area, and this is a very important information to find out the spacing between pole to pole both  X & Y axis.
•  This is an example of a solar street light luminosity vs pole height curve of a street light, but this an example, this varies product to product depending on their wattage and efficiency.
  

  

  Lux Level at different height

   

• As the above Picture you can see at pole height increases the Lux decreases, at 6 meter height the luminosity  is 43 Lux when it is 8 meter it becomes 25 Lux .
• To calculate the matter of spacing between the street lights, now you need to consider road parameters which is 100m long and 30m wide..
• Before you put the street lights on 100m x 30m road, first see at what area the luminosity is still good for the road, meaning you can see everything clear at that luminosity.According to the picture above at 12M pole height the Lux is still good which is 12 Lux, now see what area of road it can cover with light.You will see it can cover 42M long and 15m wide road area which is very good.But be careful that area will cost you more money because you are installing at 12M long pole which is costly and hard for the future maintenance.But if you install at 10M pole height then luminosity area will be 35M long and 12M wide then you can't fulfill for the road width luminosity condition which is 30M>(12+12)M...then you have no choice but install at 12M pole height.....
• Now Calculate at 12M pole height how many street lights will be needed, for our 100M long and 30M wide road .From the luminosity Vs pole height picture we see at 12M height the street light can cover 42M long and 15M wide area , then we need (100/42)=2.3 street lights = 3 street light at Horizontal way (Side by Side), and we need (30/15)= 2 street light to Vertical illumination..
• So Finally we need (Horizontal X Vertical)  = 3 x 2= 6 street light to illuminate the entire 100m long and 30M wide Road.....

So the installation needs 6 Solar street lights to illuminate the entire road for the given street light luminous capacity... but this is just a prototype example, the number of solar street light can be reduced by better street lights which has better luminosity....like I said you have to research a lot to  accomplish a perfect project...

Then it comes to the back up power of the street lights mean the battery, Solar panel and charge controller for  this 100M long and 30M wide road...

 This system needs 12 hour backup plan....

 As we know solar street lights has basically four parts i) Solar Panel ii) battery iii) Charge controller iv) LED lights and the pole...

Let assume we have chosen 60W street lights which has the luminosity (we need for the project that described above) ,now needs a solar panel system, charge controller and battery...

Battery Calculation :

                                 Time is = 12 hour (back up time)

                                 Load = 60W (LED)

                        

                                 Total Energy for( LED) 12 hour needs : 12x60=  720Wh per street light

                                 

                                 To back up, Battery(12V) Energy needs = 720/12 =  60Ah per street light

                                 Battery(12V) Energy needs at 50% DoD = 2 x 60 = 120 Ah per street light

Solar Panel :   

In Bangladesh the average day light time is 4.5~5 hours , 

Solar Panels need for charging battery(12V)= 720(load)/5= 144 Watt Solar Panel,

Either you can install 144W Solar Panel or closer like 150 Watt, if 144W is not available or you can install two small but same rating solar panel for this system like 2 x 75W solar Panel per street light

Charge Controller :  

To select a charge controller you need to check the Solar Panel & battery current and voltage.

Charge controller = Solar Panel wattage /voltage = 150/12=12.5A, choose a charge controller which is close or above 12.5A ... per street light

Pole : We have already determine the height of the pole 12M which has shown above, contact the dealer for 12M long pole...per street light

Now you can calculate for 6 solar street lights ,Alhamdulillah 

Note :So that's all about the calculation but make sure the place where you are going for installation is windy or muddy or perfect brick road...because you may be need different types of products for different places like if some place is windy then you need better street pole that can face storm or heavy rain...

The complete installation procedure will  be given in the ..Training Basic Video

Hope this will be helpful (Jajakallahu Khair)