In the two previous articles, we learnt all about solar thermal technology. In this and the next few articles, I will talk about solar PV technology and solar PV systems.
The “PV” in solar PV stands for photovoltaic, which means creation of a voltage difference, and therefore a current, upon exposure to light. The photovoltaic effect was first observed by A. E. Becquerel in 1839, believe it or not! Its basic principle is very simple: upon exposure to light, high energy photons hit the electrons, thus exciting them and setting them “free” which leads to charge separation as in the case of a battery. If an external load is connected between the two terminals, then an electric current will flow through it.
The basic device that generates electricity using the photovoltaic effect is called a solar “cell”. Many solar cells are connected in series to form a solar PV “module”. And when many solar PV modules are connected in series/parallel, it is called a solar PV “panel”. All that is required for solar cells/modules/panels to generate electricity is for them to be kept out in the sun, and connected to the appropriate electronics of course. It’s as simple as that!
There are many advantages of energy generated from solar PV:
1. It is free and unlimited! Just to put things in perspective, the total energy that is incident on the Earth’s surface in one hour, if harnessed completely, is enough to power the entire world for one year! If that is not a jaw-dropping statistic, I don’t know what is.
2. It is non-polluting; it does not emit CO2 or any other gases, greenhouse or otherwise, that are harmful to the environment.
3. It has zero running cost. Other types of power plants require some “input” to generate electricity, which more often than not, has to be transported from faraway places. None of that is required in the case of solar PV since the sun distributes sunlight to all corners of the Earth, every single day, for free!
4. It has no moving parts, and therefore there’s no question of wear and tear. As a result, solar PV power plants require very little maintenance and last for many years. All that is needed to keep them working optimally is regular cleaning with water.
5. It does not make any sound. It will sit silently on your rooftop or ground and generate electricity, which is actually anti-climactic in a strange way. The associated electronics – mainly the inverters – does make some noise but it is very minimal.
6. It is scalable, i.e. it can be used to generate energy from mW (milli Watt) to MW (mega Watt) scale. This is a feature that is unique to solar PV; no other power generation method can boast of doing this.
7. It can be built very quickly compared to other types of power plants; a 100 MW solar PV power plant can be designed, installed, tested, and commissioned in less than one year! Thermal power plants, on the other hand, take anywhere from three to five years to be commissioned. This is a very crucial aspect because if India is not able to provide the required energy when it is needed, its “demographic dividend” will turn into “demographic disaster”.
Having said that, solar PV has some caveats as well:
1. It requires a lot of capital expenditure. Although this has reduced considerably over the last five years – by as much as 75% – it is still quite high and by far the biggest impediment in the adoption of solar energy.
2. It requires a lot of space. This becomes a big issue in countries like Japan and Singapore where land resource is very scarce.
Thankfully, it isn’t much of an issue for India since it has a lot of land mass.
The above figure is from the “Beehives or Elephants” report prepared by BridgeToIndia and sponsored by Tata Solar. It states that 1000 GW of solar can be installed if half the desert district of Barmer is covered with solar PV modules at today’s efficiencies! This is roughly 6 times power requirement of India as of today. The required area is 0.5% of the total area of India or 3.5% of the waste land in India. If at all, this figure reiterates the point that solar PV is virtually limitless in India and space isn’t a problem at all, if there is a will and enough money to invest in solar. Therefore, there is no doubt in my mind that the future belongs to solar PV!
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