Solar Energy: World’s Future Energy Demand

If we could use all the energy sun provides to the earth for just 1 hour, we would meet the total global energy needs for 1 year. Undoubtedly, the sun is a powerful energy source, and even though we are not able but to collect a fraction of energy from this powerful source, harnessing this energy by installing solar power plants can still make a significant difference. Considering this fact, solar energy became one of the fastest-growing renewable energy sources in the last decade, and countries are racing to assert their dominance in this sector for several reasons. Last year, the Indian Government officially announced that the Bhadla Solar Park became the biggest solar park in the world with a capacity of 2,245 Mega Watts.

Bhadla Solar Park

To demonstrate the amount of power this solar park embodies from a different perspective, an impressive fact can be provided: this amount of energy can power more than 670,000 homes, in other words, a city. The Earth intercepts a lot of solar power: 173,000 terawatts. That’s 10,000 times more power than the planet’s population uses, and Solar energy, for these reasons, is seen as one of the best energy sources in the world as the reliability of this energy source is highly inflated in the last decade. However, how solar plants convert sunlight, solar energy, into electrical energy must be understood perfectly to increase their efficiency for future use.

Solar panels are made up of smaller units called solar, photovoltaic, cells. The most common solar cells are made from silicon, a semiconductor that is the second most abundant element on earth. In addition to its cheap price and long lifetime, the reason for the usage of this element is that it has greater efficiency in converting light energy into electricity due to the lattice structure it obtains. However, in order to comprehend the operation of a solar cell, we need to dig a little deeper, down at the atomic level. Silicon has an atomic number of 14 which means it has 14 protons in its nucleus as well as 14 electrons surrounding its nucleus. These electrons are distributed in 3 shells by the order of 2,8,4. The innermost shell is full of two electrons, and the middle shell is full of eight. However, the outermost shell has 4 valance electrons which means it is in half-filled form. That means in order for Silicon to be fully stable, it should get 4 more electrons from other atoms. Silicon does this with other silicon atoms by forming 4 covalent bonds with other Silicon atoms, subsequently forming

Silicon Crystalline

what is called a crystalline structure. With the formation of crystalline structure and all those electrons reaching out and connecting to each other, the possible move of an electric current is prohibited. That's why the silicon found in solar panels is not fully pure; it’s mixed in with other elements, mostly phosphorous and boron. Phosphorous is used in the top layer of silicon, which adds extra electrons, with a negative charge, to that layer. On the other hand, the bottom layer gets a dose of boron, which results in fewer electrons, or a positive charge. An electric field occurs when opposite charges are separated from each other.

So, this system results in an electric field at the junction between the silicon layers which allows the electric current to proceed. These silicon layers are called the N-type layer and the P-type layer. The N-type layer has extra electrons, and the P-type layer has extra spaces for electrons, called holes. When these two types of silicon meet, electrons can wander across the p/n junction leaving a positive charge on one side and creating a negative charge on the other. When a photon of sunlight hits the P-type layer, the electrons start to move, filling the voids in each other. This balancing process perpetuates the loop over and over again, generating electricity. There are some other components of the cell that enable these electrons to turn into usable power as well. Metal conductive plates on the sides of the cell collect the electrons and transfer them to wires, allowing the electrons to flow as a source of electricity. At the top of the cell, there is an anti-reflective coating that allows panels to collect as much as sunlight possible. You can see all the aforementioned components in the figure below.

Now we have understood how solar plant functions, but how these solar panels are engineered is another critical point in this industry. Solar cells can last for decades without generating any kind of problem, however, most of the commercial systems are currently 15-20% efficient. To increase the efficiency at hand, individual people who utilize solar panels for their inhabitants use some tactics. Most people install their solar panels on the roof of their home, allowing the panels to directly harness the sun's radiation and convert that energy into useable power. In this way, they also save an important amount of space. Planting solar panels in the backyard would occupy important space when considering the fact that a typical American house will need 14-36 solar panels to cover their power bill which corresponds to at least 20 meters squared. In addition to this, in the northern hemisphere, solar panels are faced true south and vice versa applies in the southern hemisphere. Usually, this is the best direction because solar panels will receive direct light throughout the day. On the other hand, despite its enormous benefits, some people may think solar panels are useless at night. They are right to some degree, solar panels definitely don’t generate enough electricity during the night, but the energy collected in the morning can be stored in batteries during the daytime with new technologies developing. For massive projects like the aforementioned Bhadla Solar Park, which require bigger areas, scientists and companies prefer to use deserts and aqueous mediums for various reasons. The first factor is the long-time exposure to sunlight photons since there is no factor that would impede their exposure by creating a fade. And since most of the deserts get the sunlight at right angles, their efficiency increases much more. Floating solars have several additional advantages; they

Floating Solar Systems

don’t take up any valuable space on land, and the cooling effect of the water on which the panels float makes them more efficient. They can also help to mitigate the evaporation of water for drinking or irrigation by intercepting sunlight before it hits a reservoir’s surface. As the solar panels are being used for maximum energy, people are questioning whether they can be used in bigger areas with much more efficiency. The Sahara Desert, being one of the biggest candidates for this project, can add a lot of power to our world by all means when considering the increasing worldwide urbanization; researchers examine if it might be possible to transform the world's largest desert, the Sahara, into a giant solar park, capable of meeting four times the world's current energy demand.

This article was published in JoSS's 44th Issue on www.joyofsharingscience.com

-Güney Baver Gürbüz

References: 

“Pros and Cons of Solar Energy.” United Kingdom, www.greenmatch.co.uk/blog/2014/08/5-advantages-and-5-disadvantages-of-solar-energy. 

Sarah. “From Sunlight to Electricity.” Curious, 7 Nov. 2017, www.science.org.au/curious/technology-future/solar-pv. 

“NOVA | Saved By the Sun | Inside a Solar Cell.” PBS, Public Broadcasting Service, www.pbs.org/wgbh/nova/solar/insi-nf.html. 
 

“How Do Solar Panels Work? - Richard Komp.” TED, TED-Ed, ed.ted.com/lessons/how-do-solar-panels-work-richard-komp. 

Priya SanjayPriya currently serves as the Publisher for MercomIndia.com. With more than a decade of experience working in corporate communications. “With 2,245 MW of Commissioned Solar Projects, World's Largest Solar Park Is Now at Bhadla.” Mercom India, 23 Mar. 2020, mercomindia.com/world-largest-solar-park-bhadla/.