The Math of Solar Energy!

First thing first, 1 kWh (kilowatt hour) is called 1 unit of electricity. All the electric appliances have a rated capacity, which is mentioned somewhere on them. For instance, a 40 W tube light would consume 40×6 Wh (watt hours) of electricity when it is used for 6 hours.

1 kWh = 1000 Wh.

1000 kWh = 1 MWh (Megawatt hours).

1000 MWh = 1 GWh (Gigawatt hours).

1000 GWh = 1 TWh (Terawatt hours).

1000 TWh = 1000 PWh (Petawatt hours). Earth receives about 173 PWh of solar energy!

How much energy does a solar module produce? Well, the rated capacity of the module will give you information about the amount of energy a solar module would produce. Multiply that number by the available sunshine hours at the location and you will get the exact energy (kWh) that a solar module will produce.

Let’s talk about how much carbon emission can we save from adopting solar energy for our energy needs. I am considering petrol, diesel and coal as the sources.

Following is the chemical reaction that happens when petrol is burned:

2 C8H18 + 25 O2 –> 16 CO2 + 18 H2O + Energy

2 mol C8H18 (114 g/mol) –> 16 mol CO2(44 g/mol)

=>   2*114=228g –> 16*44=704g

This means that when 228g of petrol is burnt 704g of COis produced.

Therefore, 1 kg of Petrol will produce 3.088 kg of CO2. (1000/228*704=3087.72g)
And, 1 litre of Petrol will produce 2.22 kg of CO2(3087.72*0.7197=2224.64)

Specific Co2 emission from various fuels.pngThis chart compares the CO2 emission from different fuels. Mostly, we get our energy from burning coal. For producing 1 unit (kWh) of electricity, 0.34 kg of CO2 is emitted. To power just one home (that uses on an average 500 units of electricity per month), 170 kg of CO2 will be emitted. That is 2 tonnes of CO2 per year; 51 tonnes of CO2 for 25 years! Now, that is just for one home. India’s power demand is in billion kWh (1162423 MU), of which around 70% is met by fossil fuels. Only a big number (with an exclamation mark at the end) will come out when we calculate how much CO2 will be emitted to meet our energy demand.

A solar PV power plant can offset this carbon emission by a huge factor. I won’t deny the fact that the manufacturing of PV panels pollutes the environment, however, this figure is significantly small when compared to the emissions via conventional fuels.

Apart from helping you to save the environment, a solar PV power plant can prove to be a smart investment. You get high returns in a course of 25 years from a solar PV power plant. See this chart to get an idea:



Utility Electricity   Solar Power Plant  
Tariff (Rs.) 8 SPV capacity (kW) 3
Escalation annually 3% Plant landing cost 1,95,000.00
Units consumed/month 500.00 Units generated/month 495.00
Units consumed/year 6,000.00 Units generated/year 5,940.00


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