07 May 2015 13:52:57 IST

Lighting up your life

We can produce lots and lots of non-polluting energy with only free sunshine as the raw material

You are probably hearing a lot more about ‘solar’ these days than a couple of years back. That is because the world is kicked-up about tapping sun’s energy for our needs. Interesting nuggets of information, graphically told, are making the rounds. For instance, they say the energy that sun bestows on our planet in one hour, if we could capture it, is sufficient to run the entire world for one full year. If you talk to our Ministry of New and Renewable Energy, they will tell you that if India could bag all the sunshine it receives, we could produce 5,000 trillion kilowatts of energy with it. But don’t worry about these numbers. The point is, we can produce lots and lots of non-polluting energy with only free sunshine as the raw material.

You may wonder, why now? After all, science ‘photo electric effect’ has been around for a century-and-a-half. Indeed, that (and not the Theory of Relativity) was what that got Einstein the Nobel Prize. The answer is simple: economics. Earlier, you knew that you could produce electricity by propping a ‘solar panel’ up against sunlight, but it was a very expensive way of producing electricity, compared with electricity generated using coal or by building dams. But now, due to a number of reasons, ‘solar power’ has become a lot, lot cheaper, and is only a shade costlier than coal or hydro power. We will not go deep into the reasons. Suffice to say that in the last decade the developed world got pretty worked up about ‘climate change’, or the phenomenon causing the earth getting hotter, with all its scary consequences such as ocean levels rising and swallowing many islands and swathes of coastal lands, famines, tsunamis, unpredictable hurricanes, disease and so on. If you want to learn more about these, read up on a guy called Al Gore, who “used to be the Next President of the United States”. Al got a noble prize for his efforts to make people aware of the ill effects of climate change.

But we are digressing. The spectre of the hot world drove the Western countries to think of cleaner ways of producing electricity, because conventional means such as coal and (to a lesser extent) natural gas, contribute to making the world hotter. These countries began offering large incentives to solar power, so as to make it affordable. As a result, the ‘solar industry’ took off. And you know that when you produce things in large quantities, you produce them cheaper. Solar prices started dipping and slowly began to move within reach of countries like ours.

It used to cost Rs 21 crore to put up 1 MW of solar plant in 2009. Today it costs a third of that. If you don’t understand terms like megawatt or kilowatt-hour, don’t worry. It is no big deal, see the end of the article, under quick guide. This happened because as governments in the developed countries gave money to support construction of solar power plants and purchase of solar electricity—which was still very costly—many companies cropped up to produce the equipment needed for building solar plants. Most of these companies were Chinese and you know, when the Chinese set out to making something, they make them in large numbers and very cheap. (In the next section, I’ll tell you what these equipment are and how they produce electricity.)

As the cost of putting up a solar power plant fell, the prices of the electricity the newer plants produced also fell. Just to give you an idea of how the prices have moved, around 2009 government of India told businessmen in the country “guys, you put up solar power plants and we will buy the power you produce” and guess what it offered to pay for each unit of electricity they produced? Rs 18/- ! In comparison, we pay around Rs 5 for every kilowatt-hour we consume. The government offered a high price of Rs 18 because otherwise nobody would come forward to put up solar plants. But since then, the costs of building a solar power plant have come down drastically and consequently, the prices of solar power have also fallen, to about Rs 6.50 a kilowatt-hour now.

In 2009, India had practically no solar power capacity to speak of. Today, we have 3,000 MW of capacity. If you look at all the power plants in India, including the coal-fired, hydro, nuclear and wind, the total power capacity in the country is about 2,40,000 MW. Of that, 3,000 MW of solar is but a very tiny fraction. But then, this is only the beginning. 3,000 MW is still a respectable number, but the point here is that the process of building solar power capacity is gathering momentum. For example, this year, India is very likely to build 1,800 MW. Next year it could be 3,000.

The Manmohan Singh government had a plan of creating 20,000 MW of solar capacity by the year 2022. Then the government changed and the new BJP power minister, Piyush Goyal, studied the plans and said, “Nonsense! We will build 100,000 MW by 2022!” Many people laughed and complimented themselves over India having a minister with a good sense of humour. Indeed, the target of 100,000 MW seems so ridiculous. Look at it: In the last 60-odd years, we have built 240,000 MW of power capacity. Can you build 100,000 MW of solar alone in just 7 years? Sounds preposterous, right? But not quite so. The minister seems to have a good plan for making it happen. In fact, he wants to build another 60,000 MW of wind power capacity by 2022. Big, big plans. There will be a lot about ‘wind’ too, in this column.

We can only wait and see what happens. All we know today is, the targets are not impossible, though they are very, very difficult to meet. But the big picture is not how many megawatts will come up by 2022. The big picture is that the solar sector is in for an explosive growth. And that, is the key message for you students.

First of all, you should know what is happening. Then you could probably think of what you could be doing. Would you want to become a ‘solar professional’? You could attempt, for instance, a Ph.D in solar. (In the coming sections, I’ll tell you about the interesting areas of research in solar.) You might want to start a solar company. You might want to be a solar consultant. You could be an executive in a company that has (either only, or also) solar power plants, in-charge of running the plants. You could teach solar, start a portal, invent solar products, market solar products and, if you are socially inclined, help poor people in remote villages get electricity using solar equipment.

Quick guide:

Your light bulb is 18 watts. You pay your electricity company for every kilowatt-hour of energy you consume. The solar power plant on the roof of your neighbour is a 1 kilowatt system. The coal-fired power plant outside your city is of 500 megawatt capacity.

Watt, kilowatt, kilowatt-hour, megawatt….huh! If you are confused about these terms, don’t feel bad about it. Here is what they mean, and you will see it is pretty simple.

You only need to understand what ‘watt’ is. Then it is straightforward. A kilowatt is 1,000 watts, a megawatt is 1,000 kilowatts and a gigawatt is 1,000 megawatts. It is just like saying thousand, lakhs and crores, or thousands, millions and billions.


Machines convert one form of energy into another, right? A hydro electricity plant converts the kinetic energy (or the ability of something that is moving to push something else) of water into electrical energy. A solar power plant converts light energy into electrical energy. Why, even your motorcycle engine converts the chemical energy of petrol into kinetic energy. We see all the time one form of energy being converted into some other form.

‘Watt’ is a unit to measure the rate of conversion. It gives an idea of ‘how much’ of energy is converted from one form into another in one second. Therefore, a 100 Watts machine is one that can convert 100 units of energy from one form to another in one second. A 1 kilowatt solar power plant is one that can convert 1,000 units of sun’s energy into electricity in one second. Watt (and therefore kilowatt (kW), megawatt (MW) and gigawatt (GW) simply denotes the capacity of the machine. It does not denote how much electricity it produces.

It is like the water pump in your house. You speak of the capacity of the pump in terms of horsepower, right? You have a 3 hp pump in your house, while the farmer has a 5 hp one in his farm. Like that. But you would measure the amount of water it pumps up in terms of litres-which would in turn depend upon how long the pump worked. A 3 hp pump, if it ran for one hour, would produce x litres of water.

Think of ‘watt’ as equivalent to ‘hp’ and ‘watt-hour’ as the equivalent of litres of water.

In simple English, we call one kilowatt-hour as one ‘unit’ of electricity. It is the quantity of electricity produced by the machine. Remember, again, the capacity of the machine is expressed in watts, while the quantity of electricity it produces is expressed in watt-hours.

One kilowatt, or one unit of electricity is the quantity of electricity produced by:

A machine of 1 watt capacity if it works for 1,000 hours

A machine of 10 watt capacity if it works for 100 hours

A machine of 50 watt capacity if it works for 20 hours

A machine of 100 watt capacity if it works for 10 hours

A machine of 1,000 watt capacity if it works for 1 hour

Like that you could have any combination.

You could replace ‘quantity of electricity produced’ with ‘quantity of electricity consumed’. For example, a 100 watt bulb, if it works for 10 hours, it would have consumed one unit of current and you will pay your electricity company Rs 5 or whatever the rate. If your geyser is rated 1000 watts, and you keep it on for one hour, you will pay for one unit.

Now, I said Watt is energy converted per second? One handful? One bucketful? Converting a handful of energy in one second and one bucketful of energy in one second obviously cannot be the same. So you need to say how much of energy converted from one form to another in one second.

Energy is measured in terms of ‘joules’, (named after the British chap, James Prescott Joule.) The scientific definition of watt is, the conversion of one joule of energy in one second. So, a one watt device converts one joule of energy from one form to another in one second.

It might be useful to remember this: 1 watt = conversion of 1 joule of energy in 1 second.

As always, an answer leads to another question. What is a joule? We could get into discussions about these. But it would be moving far from our subject – solar. Students who are interested could always google up for further knowledge, or ask us