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Solar LED Street Light Vs AC LED street light

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As we all know LED's work only on direct current. Any led street light that is manufactured today converts alternating current to direct current before it can light up the LED's using drivers(Drivers are power supply for an LED Light, much like a ballast is to a Tube light ). So What is the difference between AC LED street light and Solar LED street light?

Solar LED Street Light:

As described before any LED works on DC supply. In this scenario street light takes power directly from the batteries usually a 12 volts or 24 volts battery based on the application. Based on the level of the current in the batteries the intensity of LED's varies, which may destroy the LED's. To solve this we use a driver in between the batteries and the LED's which will regulate the voltage and current based on the LED requirements also the driver helps to avoid over drain in the batteries. 

AC LED Street Light

In AC street light LED's  the alternating current is converted into a direct current where in the current is made constant and the voltage changes on the configuration of LED's used vice versa can also be done where voltage is constant and current is variable.

 There are many ways to build these drivers we can either use microprocessor or simple ac-dc circuit using diodes. The cost and longevity of the street light depends on the driver and components used as most of the LED's in the market available today have 40,000 to 60,000 hours life.

In my next blog I will write more about driver types bye for now.




Return on Investment for LED Lights compared to Incandescent & CFL

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As we all know LED Lights are becoming popular due to various benefits it can offer. There has been lot of emails and questions regarding how much electricity can be saved and what will be the payback when compared to CFL and Incandescent lights.


Comparing 60 Watts of Incandescent Lights with CFL/LED that can produce same amount of light (Lumens):



LED Light
CFL
Incandescent
Lumens/Watt
120
51
12
Life Time in Hours
50,000
6000
1200
Watts required
6
14
60
Cost of the bulb in Rupees
1,200
180
60
Kwh used for 50K hours
300
700
3000
Electricity Cost @ Rs.7.00
2,100
4,900
21,000
Replacement of bulbs for 50K Hrs
1
5
42
Replacement Expenses + bulb cost
0
1,155
3,360
Total cost in Rupees
3,300
6,055
24,360







Carbon Footprint

Carbon footprint is the amount of Green house gases like carbon dioxide, methane, nitrous oxide emissions emitted by a building, organization etc. It relates to the amount of greenhouse gases we are producing in our day-to-day lives through burning fossil fuels for electricity, heating, transportation etc.

For our discussion we are taking carbon footprint for indoor lighting in our office buildings. We can increase the performance of the building by using LED lights and reduce the building carbon foot print. In this article we will calculate the carbon footprint for
  1. Incandescent Light
  2. Compact Fluorescent Light
  3. LED Lights
Electricity



We should know, half of our carbon footprint is due to electricity and 17 % is due to lighting alone. Electricity in turn can be produced by coal, natural gas, petroleum, and other. Electricity is produced from different sources and how much GHG released is shown as below Table

SourceMillion metric tones of co2 emission for 1 yearElectricity generation (Billion kWh) for 1 year
coal17881882
Petroleum106119
Natural gas337562
Other1422
Non fossil fuelsnone1106
Total22453621

Since close to 2245 million metric tones of CO2 emitted by total electricity generation per 1 year. A single kilowatt-hour of electricity will generate 619 grams of CO2 emissions.



Incandescent Light
 
Incandescent lamp is a source of light which produce light when the filament is being heated. It can release 80% electrical energy converted into heat energy. We can calculate how much CO2 will be emitted by 40 watt incandescent bulb
 
  • Power Consumption- 40 watts
  • Operation per day- 10 hours
  • Power Consumption per annum-146000 watt
  • Electricity per hour (kwh) - 0.04 (1 kWh=619g CO2 can be released)
  •  Lighting Carbon Emission per year/lamp (146*619g ) -90.3 kg.
A single 40 watts incandescent bulb will generate 90.3 kilograms of CO2 for every year. The reduction of carbon footprint is none for this lamp.

Compact Fluorescent Light
As we all know CFL produce less heat and more visible light compare than incandescent lamp. We can calculate how much CO2 will be emitted by 14 watt incandescent bulb
  • Power Consumption- 14 watts
  • Operation per day- 10 hours
  • Power Consumption per annum-51100 watt
  • Electricity per hour (kwh) – 0.014 (1 kWh=619 g CO2 can be released)
  • Lighting Carbon Emission per year/lamp- (51.1*619g ) - 31.6 kg.
A single 14 watts CFL lamp will generate 31.6 kilograms of CO2 for every year. The reduction of carbon footprint is none for this lamp. CFL contains harmful mercury which creates mercury emission. Estimated suggestion led lights only will reduce our carbon foot print over than other lights.


LED Lights



LED lights consumes low power and energy efficient over than other lights. Not even a single point we can’t compare led lights with other lighting.We can calculate how much CO2 will be emitted by our 8 watt LED Tube light

  • Power Consumption- 8 watts
  • Operation per day- 10 hours
  • Power Consumption per annum-29200 watt
  • Electricity per hour (kwh) – 0.008 (1 kWh=619 g CO2 can be released)
  • Lighting Carbon Emission per year/lamp(29.2 *619g) - 18 kg.
A building’s carbon footprint from led lighting can be reduced by 68%.


  • Reduction in Carbon Footprint (tons)-0.122(12.28 kg)
The 8-watt LED equivalent will only be responsible 18 kilograms of CO2 over the same time span.

Incandescent
Bulb
CFLLED light
Power Consumption(watt)40148
Electricity(kwh)0.040.0148.008
Hours of Operation Per Day101010
Carbon Emissions (tons) per year/lamp0.9030.3160.18
Reduction in Carbon Footprint (tons) / lamp0.12

  • LED light can reduce our carbon footprint by 0.12 tones per year.
  • Led light does not contain mercury; it is a big benefit for this lamp.
  • CFL contain 3-5mg per bulb which is poisonous. Mercury emission is 1.2mg from power plant using CFL.
  • Incandescent, it is 5.8 mg from power plant.
The 8-watt LED equivalent will only be responsible 18 kilograms of CO2 over the same time span.
Based on above comparisons, LED emerges as the BEST option to requce carbon footprint.