Advantages of Solar Street Lights

Solar-powered Street Lights are an excellent alternative to conventional grid-connected street lights. In India, solar street lights are being implemented in a lot of locations due to the various advantages they provide. In this post, let us look at a comprehensive list of the advantages (and a few limitations) of solar street lights.  

Advanatages of Solar Street Lights:

1. Solar street lights (with battery) can be totally off-grid. That means, they need not be connected to the electrical cables/EB grid and hence all the power (that would have been provided by the grid) can now be used for other applications. 
2. The expensive transmission & distribution infrastructure (cabling, substations, etc) can be totally avoided with solar street lights - this provides a considerable amount of savings. 
3. There are no running costs (electricity charges) for solar street lights. 
4. The maintenance charges is also minimum - If battery is used, it may need to be replaced every 5-6 years, but solar panels have a long life-expectancy of 25 years (at least). If LED lamp is used, the lamp too gets a long life (about 50,000 hours, approx).
5. Sun-light is available for almost 9 months with full-intensity (in India) and even during rainy seasons/dull-days, solar power can be generated. 
6. Solar street lights can work in the nights because they have a built-in battery that can store solar energy during the day. These batteries can provide continuous operation (during nights) for about 3-5 days, even if there is no sun, during the day. If a higher capacity battery is used, the back-up time can be increased considerably. 
7. Solar street lights are the only option to light up remote areas and rural areas that are not connected to the grid. They can also be used in industrial complexes, educational institutions, airports, parks and other large organizations in order to avoid expensive cabling/maintenance charges, involved with normal street lights.
8. Since solar street lights operate at 12V DC (mostly) and avoid T&D cables - so, there is no risk of electric shocks. They are safe.
9. Solar energy, used to power the solar lights, are a form of renewable energy which is environmentally friendly and emits no carbon. The raw material (used to generate power) is sun-light ~ it is free for all and available everywhere.
10. Solar street lights offer simple, easy and quick installation, mainly due to the absence of the need to connect each light to the power-lines/electrical-grid.
11. Solar lights can be designed to automatically switch on/switch off, based on the amount of ambient light present in the surroundings. No manual intervention/central switching control infrastructure is required.  
12. Maintenance-free batteries (that can easily be replaced) can be used in solar street lights in order to minimize the efforts needed to maintain these systems.
13. Grounding, charge-controller, lightning-protection and other security protections can be implemented.
14. LED lamps, CFL lamps or Induction lamps can be used with solar street lights. While CFL lamps are least-expensive, they have a higher running cost. LED/Induction lamps are more expensive, but their running cost is very less.
15. If LED/Induction lamps are used, automobile commuters will not find any glare, that is found with sodium-vapor lamps (normal street lights). 
16. Solar street lights generate less heat when compared to sodium vapor lamps.
17. They are not affected (much) by rain, storms, dust, etc. 
18. Crystalline solar panels are normally used (over thin-film) because they can provide a higher efficiency. Hence a smaller capacity/size of solar modules is sufficient, which is important. 
19. These solar panels can be attached on the top of lights/pole (for sunlight exposure) and the electricity generated by them is directly used by the lights right below them. This eliminates the transmission & distribution losses associated with grid-connected street lights.
20. In places where grid/EB lines are already available, grid-interactive solar street lights can be used to avoid batteries. These solar street lights generate and export power to the grid during the day and import power from the grid during the night. That way, no power is wasted. 

Limitations:    

1. The initial capital expenditure maybe somewhat higher than normal street lights, especially when LED/Induction lights are used.
2. Batteries need to be changed regularly (every 5-6 years), their disposal is also an issue. 
3. Lamps may also need to be changed after their lifetime.
4. Though solar panels are warranted for 25 years (performance warranty), the manufacturers many not last so long - in such cases, who will provide the warranty?

  

Above photo of solar street light taken by me @ Sriperumbudur, Chennai

To get an idea/understand more about the technical components (and specifications) of solar street lights, please read the document released my MNRE for CFL Solar Street Lights (pdf) and LED Solar Street Lights (pdf) for 2013/14.