NATURE INSPIRED INVENTIONS --- Photovoltaic cells; the reason for the non-reflecting eyes of the moth.
Solar energy is the oldest form of energy harnessed by man. Man in his primitive days depended on solar energy for everything. He used Solar energy to dry his clothes after washing them, he also sun dried some of his kills. When he finally left the caves and built a house of his own with mud, he depended on the energy from the sun for the drying of the mud. Despite the little knowledge he had, he knew how important the sun was to the production of its food. Due to the over importance of this source of energy, he started seeing it as a god.
Unfortunately, as man grew wiser, he discovered ways on how to harness other forms of energy, and he abandoned his first source for energy. At first, he didn't know this fuels in cars posses so much threat to his environment according to the drivers checklist, when he finally realized, he still didn't stop. It wasn't until he was beginning to feel the effects of his actions did he return to his old love.
Right now, he has discovered a way on how to efficiently harness solar energy, this time, not just for drying, but also for the generation of electricity. This he achieved by constructing photovoltaic cells, but the performance of these cells were costly and below satisfactory. It wasn't until he discovered the way the eyes of the Moth is designed by nature did he finally get the breakthrough he needed for a high utilization of solar energy.
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But before we get to how man made this amazing discovery, we need to know what solar energy and photovoltaic cells are, the deficiencies of the conventional photovoltaic cells.
SOLAR ENERGY
Solar energy is one of the renewable types of energy. Just as you guessed, the energy is from the sun. The definition of solar energy is simple, It is the energy from the sun in the form of heat and light that is harnessed by the use of photovoltaic cells, and other various technologies (like artificial photosynthesis).
Technologies involved in solar energy harnessing are characterized into passive solar and active solar. This characterization is based on how the energy is captured, how it is converted into solar power, and how it is distributed. Under the classification active solar technique, we have the concentrated solar power, heating of water by the sun there by harnessing it's energy and photovoltaic systems.
Under the Passive solar technique, we have stuffs like choosing a material that has good thermal and lower reflection properties, orienting a building towards the sun and building structures with spaces that allows air to circulate naturally.
The amount of solar radiation the earth received from the sun at the upper atmosphere is about 174 PW (which is equal to 174 * 10^15 Watts), but not all of this energy is absorbed by the earth. Due to the nature of the earth's surface, about 30% of this energy is reflected back into the space while the remaining gets absorbed into the cloud, the land, the ocean e.t.c.
Solar energy has a lot of positive effects in our environment. Heat from the sun is the reason why air circulation is possible as it causes the air that is close to the earth's surface to heat up, which result to it getting warm and then rising up while the warm air gets replaced by a cooler air and the cycle is repeated. It also aids in photosynthesis. But today, we would be considering how it is harnessed so as to generate electricity.
The rays of sunlight that is absorbed by earth falls within the range of visible and the near-infrared light spectrum. Only a very little part of the rays is ultraviolet. I know you must be wondering the amount of energy in the sunlight you receive in your area. Am glad to tell you, that per each 1m² in your area receives about 150-300W of solar energy.
The earth absorbs about 385000 exajoules of energy every year from the sun. This is quite a large amount of energy, in fact as of 2002, the whole world was not even able to consume in a year the energy generated at this rate just in one hour. As of now, the energy the earth absorbs from the sun is quite much, all the energies from coal, natural gas, nuclear fuels, oils and all other non-renewable gases put together is not even up to half of the energy the earth absorbs per year. Thus, solar energy is literally the greatest source of energy on earth. This means that there is a great need for man to harness this great power so as to generate electricity, but for him to do so, he needs a device called a photovoltaic cell.
WHAT IS A PHOTOVOLTAIC CELL
Photovoltaic cells are those types of cells which are made of semiconductor diode and have the ability of converting visible light into a direct current. It is worth noting that recently, some photovoltaic cells have be built in such a way that they can even convert infrared or ultraviolet light rays into a Direct current. Photovoltaic cells are very important in the generation of solar electricity, in fact, without them, the energy from the sun can't be harnessed.
When man began to generate electricity using photovoltaic cells, he made the photovoltaic cells using silicon that is doped with other elements. This doping creates a deficiency of either holes or electrons in the silicon, causing it not to be neutral. Right now man have made other materials like cadmium telluride (CdTe) which increases the photovoltaic abilities of the PV cells.
There are two main types of semiconductor materials, the N-type and the P-type. When these two are joined, a PN-Juntrion is formed. It is this junction that gets exposed to light. Now with the help of the electrodes connected to the semiconductor layers, the current is then drawn from the device.
Most times, one cell is not enough to generate enough amount of electricity, thus, lots of photovoltaic cells are connected together to form panels, and then, the energy generated is then stored in batteries.
HOW A PHOTOVOLTAIC CELL WORKS
We have established that man have discovered a way for converting solar energy to electricity by the use of photovoltaic cells or as we call it solar panels. One of the main constituents of photovoltaic cells is silicon, which is the most important semiconductor on earth. In this section I will be telling us how this photovoltaic cells works.
The whole working principle of the solar panel is centered on an effect known in physics as photoelectric effect. Whenever a light ray incidence on a surface, electrons are emitted. This phenomenon is known as photoelectric effect.
Remember that there are two theories in explaining the nature of light: as a particle and as a wave. The photoelectric effect is understood by seeing the rays of sunlight as consisting of particles. These particles are referred to as photons. Photons are miniscule particles, and they can also be seen as tiny packets of energy.
When these particles from the sun ray hits the silicon atoms which makes up the solar panel, electrons are emitted. If you have played the game of pool, you will observe that all other balls get hit by the white ball. I will like you to see the white ball as photons from the light ray while the balls are the electrons. Due to the energy they possess, the photons knock off electrons that are quite loose. They do so by transferring energy to those electrons getting them excited which causes them to jump off the atom.
But that's not all that is needed to generate electricity. Remember that electric current is the rate of flow of electron. This means that for electricity to be generated, these electrons emitted needs to be guided to flow in one direction. Just like water, electrons flow only when there is a difference in pressure, (that is potential difference) between two ends. Thus, for these strayed electrons to be harnessed, an electrical imbalance should be created within the cell to enable the electrons flow in one direction.
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Operation of a photovoltaic cell
In its stable unreacted state, silicon is neutral, this means that it has the same number of protons and electrons. But due to the way silicon is organized, internally, it allows the addition of other molecules into its structure, thus, allowing the formation of two different types of silicon, depending on which element is squeezed into its structure. The p-type has lesser electrons, thus it has more positively charged holes while the n-type has more electrons than holes, thus it's negatively charged.
When the n-type and the p-type are placed side by side inside the photovoltaic cell, a PN-junction is formed, and the electrons of the n-type crosses this junction to fill up the holes in the p-type, while forming a hole in its previous position. This goes on and on, and with this, a potential difference is created which allows the electrons to flow in one direction.
As this processes repeat themselves continually, more current is generated which can be used in powering electric and other electronic devices.
FACTORS THAT AFFECTS CONVERSION EFFICIENCY
Its quite unfortunate that all the energy that is incidented on a photovoltaic cells are not completely converted into electrical energy. The term conversion efficiency is term used to define the percentage at which the energy that shines on a photovoltaic cells is silicon converted to electricity.
There are factors that affect conversion efficiency. They are:
Conversion to Heat Energy:-
Lights consist of small particles called photons. When sun rays incidents on a photovoltaic cell , some part of the photons is reflected, while some passes through it. Amongst those ones that gets absorbed into the photovoltaic cells, their energy gets converted into heat energy, reducing the quantity of energy or the amount of photon supplied. This in turn reduces the amount of electrons emitted from the solar panel, thus, resulting to a low electricity generation.
Recombination of holes and Electron
Remember that the way electric current flows in a semiconductor is through the movement of electrons and holes. (The electron acting as the negative charge carrier while the holes acting as the positive charge). "Holes literally means holes" like, there is nothing there, thus, electron-hole movement involves the movement of electrons into the holes while a new hole is formed where the electron was previously. But sometimes, electrons jumps into a hole and remains there, and instead emit a photon.
This kind of reverses the energy generation processes and results to a reduction in the number of charge carriers, invariably resulting to lower power generation.This kind of recombination is called direct recombination. Indirect recombination occurs when an electron or how encounters a flaw in the crystal structure or an impurity which causes them to recombine and release their energy in the form of heat. This also results to loss of energy.
Temperature
Photovoltaic cells works more efficiently at low temperatures. This is because, a very high temperature causes the semiconductor to become more conductive resulting to an increase in temperature with a much reduce in voltage. Remember, potential difference is of great importance. Also high temperatures causes damages to the materials used in making the voltaic cell causing the life span of it to become very short.
Reflection
This is a problem of great concern. In fact, about 30% of solar energy loss is due to reflection alone. This is because a normal silicon reflects more than 30% of sunlight incidented on it.
Man have been faced with the problem of reducing these losses, especially the loss due to reflection. It wasn't until man studied the eyes of a moth, did man get the solution to his problem.
INSPIRATION FROM NATURE: THE MOTHS
Moths are quite interesting. About 160,000 species of flying insects are regarded as Moths. Along with butterflies and slippers, moths constitute the order of animals known as Lepidoptera. Moths of various sizes, some of them have a wingspan about 4mm in length while other have wings about 1foot tall. One interesting thing about this insect is that they can adapt to anywhere they are, apart from polar habitats.
Their bodies are covered with dust like scales, when you touch them, it feels kind of dusty. They have a more dull colour than other members of its order. And while they rest, they wrap their wings around their body, or hold the extended at their side, unlike the butterflies that hold their wings up straight while they rest. But all these are not what makes these insects interesting. What make them interesting is their eyes.
EXPLAINING THE MECHANISM INVOLVED
Moth's can see even in the dimmest condition, it is not quite surprising that they are nocturnal insects. A study of the moth's eye have revealed that how efficiently it traps electromagnetic waves. Their eyes are quite interesting to study. Nature did a marvelous work in the design of moth's eyes. Moth's eyes are designed in a microscopic pattern which enables the channeling of light into the center of its eye.
Moth's eyes doesn't reflect light, rather it absorbs it completely. Thus, even the the dimmest light you can think of is enough to generate the perfect vision for moths. The none reflective nature of its eyes doesn't just prevent it's exposure to its predators, it makes it able to utilize every single light ray that incidents in its eye, giving it perfect vision in the night.
Maxpixel.net: A close up look of aMoth
APPLICATIONS
Designing of solar panels
Using the lessons learnt from the Moth's eyes, scientists have been able to design a material that is high light-absorbent, thin and also very efficent. They achieved thus by patterning graphene the same way the moth's eyes is patterned. This material is used in building solar cells making it very efficent. Currently, these graphene sheets are regarded as "the most light absorbent materials made by man".
Since these graphene sheets works in the same manner like the moth's eyes, it can even harvest solar energy without necessarily being outside. Also, it can even absorb and generate electricity from other light producing sources that is not solar related.
These sheets are made to be only one-atom thick, with its carbon atoms arranged in such a way that they appear so much like the honeycomb lattice. But despite its delicate nature and arrangement, this graphene sheets have a flexibility like that of rubber and are about 200times stronger than still of the same thickness. They are even more conductive than copper.
This material kind of takes care of all the problems of the old forms of solar panels. Now, there is no need bothering about light being reflected, or materials used in designing solar panels being destroyed by excess sunlight. And even with the lowest supply of sunlight, a high amount of light is generated.
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Other Application
The study of the moth's eyes have inspired so many other inventions. Camera lens are designed based on the structure of the moth's eyes, and this result to a clearer and higher resolution imagery.
pixabay.com: Camera lens are designed based on the structure of Moth's eyes
Phone Screen guards are also designed on the idea of the non reflective nature of the moth's eye. This reduces the amount of reflected light rays from the phone, thus enabling you to be able to make use of your phone under the sun.
SOLAR ENERGY: ENERGY OF THE FUTURE
Amongst the renewable sources of energy, solar energy is the energy in which it's resources is readily available. Apart from the fact that it causes no harm to the environment, the advantages of solar energy is innumerable. The electricity generated from solar energy can be used in pumping of water, powering our homes, powering street lights, powering of telecommunications repeaters and stations, desalination of our water e.t.c.
The world powers have decided to enforce some rules so as to help save our planet from destruction by encouraging the use of renewable energy instead of fossil fuels. Right now, there is an increase in demand for solar energy. In the US, the use of solar energy have rose up to 41% as of 2017, reducing man's dependence on fossil and nuclear fuels.
Another reason why solar energy is the energy of the future is that it is economical. With this recent discovery made, we can be able to produce a a lot of energy thus reducing the cost of energy, even cheaper than. what we spend using fossil fuels. Before this discovery, the installation cost was too high, but with this recent development, this cost will drop.
Pixabay.com: Electricity from Solar Energy
Solar energy is the most promising of all sources of energy. The sun that shines only in one hour, is enough to power a whole country for a year. It is inexhaustible, and if man will. just exploit this resource, it is surely going to be an end to our energy problems.
CONCLUSION
There is no source of energy in great abundance in nature like the solar energy. There are so many advantages related to solar energy. Firstly, man does not need to bother about it getting exhausted, just like the whole world is worried about crude oil, which is beginning to show signs that it would finish before the next hundred years. Another is that, this energy has zero negative effect on the environment. Thirdly, steady supply of electricity is assured. Now, with this discovery made by studying the eyes of a moth, man can fully harness this endless energy.
Nature is quite amazing. Can you imagine, in the smallest of things has she bestowed this great attribute. Just the discovery of this little secret have made it possible for man to be able to design photovoltaic cells with very high efficiency, strongly establishing solar energy as a future source of power. If she can hide this secretly in moths which are quite small, I bet there are still so many secrets hidden in plain sight that if man discovers will take him to the next age of technology.
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REFERENCES
Solar Energy, Energy for the future
Factors that affect Solar panel efficiency
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As a citizen of a Mediterranean island country that has sunlight year-round, I often wonder why every single house's roof isn't lined with photovoltaic cells. I haven't been able to come up with an answer, except for stupidity and short-term thinking (the government waited for water to get completely exhausted before deciding to build desalination plants, for instance...).
Probably, they felt using hydropower for electricity generation would be quite cheaper for them. But am sure with this recent advancement in photovoltaic cells, they will surely have a rethink. Thanks for stopping by @alexander.alexis
Solar energy has to be used right away, or it can be stored in large batteries. These batteries, used in off-the-grid solar systems, can be charged during the day so that the energy is used at night.
This is a good solution for using solar energy all day long but it is also quite expensive. In most cases, it is smarter to just use solar energy during the day and take energy from the grid during the night (you can only do this if your system is connected to the grid). Luckily our energy demand is usually higher during the day so we can meet most of it with solar energy.
Awesome post @whileponderin
@whytepresh, I don't think solar energy will remain expensive for long. In fact, few years from now I believe that every home will be able to afford a solar panel. Remember, this was exactly how expensive hydroenergy was before it became common.
Am glad you enjoyed the article, thank you:-).
Hmmmm... I reason with you.
Wow, just learning that nature's amazing works includes a non reflective eye, it's amazing how nature gives us clues in solving some life related issues.
Renewable energy should be our focus in the concept of energy generation, if not anything, for the fact it's a clean source as the non-renewable forms of energy have been seen to have an adverse effect on nature, we have to use these clues gotten from nature in the advancement of renewable energy so in that way do away with energy generation pollution.
Nice read and a very informative article @whileponderin 👍
Surely, where should man turn to for clues if not to nature? Am glad you found it informative. Thanks @logic42
This is a beautiful piece of work. Most of our technological inventions are nature inspired. Natural sciences hold the key to our future breakthroughs in technology....thanks for this piece
That's the truth. Right now, scientists are making researches on nature because they have discovered that nature bear the answer to all our questions. Thanks for passing by @gentleshaid
Five months ago I wrote on the revolutionary solar panels capable of absorbing all the wavelengths of the solar spectrum. It's amazing that the solar panels we currently enjoy at the moment is pegged at 25%. The new one promises an efficiency of 44.5% which is nearly twice the maximum efficiency of what we enjoy now.
You are quite right, temperature do affect the efficiency of solar panels. That explains why ground mount solar panels mostly perform better than roof mounted ones. The roof usually increase the temperature of the solar arrays and thereby reducing its efficiency.
Interesting article.
Am really glad for this great discovery. Right now, we need not depend on electricity companies who are known for their behavior of barely giving power supply, but yet, they won't forget to bill you at the end of the month. With this technology, once you install a solar panel in your home, you can be able to have constant power supply. Thanks @greenrun
Yeah, I'm a big fan of renewable energy.
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Solar power is a very good source of renewable energy which is used but one thing about them is the low efficiency of the solar panels.. But they are being improved now to give better output.. Even with the low efficiency they still do a lot of work in power generation.
Just like @greenrun rightly said, with this discovery, the efficiency have been increased close to 45%, but I bet man won't stop till we have a solar panel with an efficiency of up to 80%. Thanks for passing by @adetola
I'm happy with the current efficiency, but just like Oliver Twist I'd love some more.
Hehehe... Yeah everyone needs more
@greenrun were you able to get that wind power generator you asked about sometime ago?