Renewable energy - Part 1 : Basics of Solar Energy

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And there is one more series from me. I just don’t realize what I am up to, unless I am actually doing it…lol. I gave quite a detailed reason why I started this series at the end of this article. Hope this series provides you some useful information.

I will start from the basics as I always do, and I will explain a few concepts about solar energy. We all know the usual stuff. But I’ll mention some anyways just to emphasize the importance of the sun.

1. This huge, hot ball shining in our sky is the most important life support system for our planet. Earth, which formed about four and a half billion years ago, has been supporting life since about four billion years now, thanks to the sun. Tell me what does it sound like when I say - It took earth four billion years to have an animal this smart… a human.
2. About 90% of energy we are consuming today is directly or indirectly from the sun. It is in the form of plants we eat, or the fossil fuels we use, or even the vitamin D that our bodies directly generate from the sun. Lack of light even affects our mental stability.
3. In fact, our earth stores some of the solar energy which is then manifested in different forms. Wind energy, hydropower, wave and thermal energy in the ocean, and excess biomass energy available on earth are some examples.

Now let’s talk about the conversion of sunlight into electrical energy.

Sun emits energy in the form of light owing to the nuclear fusion reactions that take place in its core. This fusion reaction, also results in plasma that constitutes the solar wind, but we are more interested in the sunlight today.

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The more appropriate way of saying sunlight is electromagnetic radiation emitted by sun. Energy here is transferred in a medium (let’s just say space or vaccum) by means of radiation (or as we simply call them, waves of light). These waves are electromagnetic in nature, are made of packets of energy called photons. Energy of each packet being hν, where h is a universal constant called Planck’s constant and ν is the frequency (oscillations per second measured in Hz) of the wave. We get wavelength of the light wave by dividing speed of light by the frequency ν.

When we say that the wave is electromagnetic, what we mean is that it has an electric field (E) and a magnetic field (H) associated with it. And both these fields, exist with the wave, in a direction which is:

1. Perpendicular to the direction in which the wave is moving ahead.
2. Perpendicular to each other.

These are the basics of what we call light. Now let's talk about energy we gain from it.

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How much energy?

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We use a term related to this concept called "solar constant". It gives us the power of sunlight per square meter area at a distance of 1 AU from the sun, or at the earth. The reason behind introducing of this term to you is to find the power received from the sunlight just outside our earth’s atmosphere. This solar constant, changes its value throughout the year. Hence we use the yearly average value of solar constant which turns out to be about 1367 W/m² or 1.367 kW/m². This means, for 1 m² of area, the amount of power received through sunlight at any instant is 1.367 kilowatts. For finding the energy associated with it, we just multiply power and time. Meaning, the amount of power delivered over some time gives us the energy transferred in the process. Let’s take the unit of time as hours. This gives us energy in terms of kilowatt-hours (kW-hr or simply kWh). Many posts, if you have browsed this topic before, say that the amount of energy that arrives near earth at any instant is many times larger than out current global consumption of electrical energy in one year (174 PW, or 174 x 10¹⁵ W, which means 174 PWh energy in just 1 hour), but this is not the amount of energy that we can possibly use due to the reasons you can see below:

1. 30% of all the sunlight that arrives at earth surface is reflected back to the space. Out of this 30%, around 4% is reflected by the atmosphere, 20% by the clouds, and nearly 6% by the earth surface. This means, earth has 70% of the total sunlight energy to utilize, which is about 122 PWh, if we consider 174PWh as 100%.

2. We can’t use much of this 70% either. Animals, plants, rivers and oceans and the aquatic life need sunlight too, right? Now let’s consider that the sunlight is evenly distributed over the earth. Since water covers 71% of earth’s surface, the oceans and rivers get most of the sunlight (let’s simply say 71%, which calculates to nearly 86 PW). This leaves 36 PWh for the land.

3. I’ll now ignore the area of land covered by snow. On land, 31% area is covered by forests, which is a disappointing fact, but a fact nonetheless. So the energy form sunlight used by the plants would be nearly 11 PWh. This leaves 25 PWh of energy for us, which actually is our electricity consumption in an entire year. And yes, we get to use this amount of energy from sunlight every single hour.

4. The solar cells that we currently have are at most 25% efficient, and the ones we are working on could be at most
   50% efficient. So, currently, if earth goes all solar, we are capable of generating at most 6.25 PWh of electrical energy, in one hour. Let’s say we use less than 1/6th of this, and generate 1 PWh of solar energy per hour. The global electrical energy production and usage in one entire year currently, is about 25 PWh. We would be able to generate this amount of energy in just a few days during summer!!!

I’d like to mention that the above simple calculations are not referred from anywhere, but I needed them out of curiosity. They might be approximately correct…lol.

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Greenhouse Gases

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Now, I’d like to mention the natural cooling mechanism of earth. The sun facing side of earth, collects heat from the sun, and radiates it out in the space during night. And this is how it cools itself. BUT, there are some gases in the atmosphere, which trap this heat from being radiated into space. We call these greenhouse gases. CO₂ among them, is the most well-known to us, since we are the ones who put a lot of it out there in the first place. The others are water vapors (H₂O), CO, CH₄, N₂O, ozone (O₃), etc. Now fyi, the water vapors and clouds contribute most to the greenhouse gases, about 36 to 72%. So unless we find any alternative to earth’s water cycle and rains - which would be stupid… even for flat earth believers, lol - we should focus on decreasing other major contributors to greenhouse effect, and CO₂ tops the list with 9 to 26%. Reducing CO₂in the atmosphere, is what the solar panels help the most with. Solar pv cells generate 20 times less CO₂ per kWh than coal would.

Now that I’m done explaining the importance of solar cells, I’d like to tell you about some great things I read while I was preparing this post.

• The sun emits light in the form of a continuous spectrum of wavelengths varying from 100 – 400 nm (ultraviolet), 380 – 780 nm (visible spectrum), and 700 nm to 1mm of infrared spectrum. These wavelengths cover most of the electromagnetic spectrum. And the intensity with which our sun emits light in these wavelengths is different for all these regions. The graph of this intensity vs wavelength is shown below.

• As you can see, the sunlight is the most intense in the visible part of the spectrum. This got me thinking, and questioning… could it be a mere coincidence that our eyes evolved in such a way that we could sense only the sunlight that is most intense?? Or is there any other reason behind it, like the need to judge ripe fruits from their colors, and see the objects and their shadows more clearly??

• Another important question that would be a bit more helpful for humanity as well came from plants. While reading about photosynthesis, I read that any object, appears to be of a particular color because it radiates that color from its body. Now, we all know that plants absorb sunlight for photosynthesis (basically, for creating their food). But, these plants radiate, or discard away from their bodies, the green color, it’s as if they just don’t need it. And since you can see the solar spectrum, the wavelength that the sun emitted at the highest intensity was green light. My question is, why on earth, do plants not use the most intense light which is made freely available by the sun? It is just like wasting the most nutritious part of your diet right? Wouldn’t it be better if plants were dark and could absorb and utilize all the possible sunlight for their growth? I searched over the internet and found two ways of explaining this – one that says plants do use greenlight, and other giving an evolutionary reason behind not using much of it. But since I don’t know much about biology, and hence I can’t teach about it. I’ll leave this for discussion. Tell me what you think about it…

• Also, about the thing that’s going on to this date – racism. I was curious as to why we have different skin colors. Turns out it’s all about the pros and cons of UV rays - about the vitamin D we get from them, and the skin cancer, and other problems caused by too much exposure to uv light.

1. Near equator, sunlight is abundant. Hence our skin is exposed to UV rays more than it should be. Over time, this resulted in evolution of dark skin (more melanin) that would block most of the UV rays. The equator passes from Africa.
2. Near the poles, sunlight is much lesser available than at equator. Hence skins had to evolve in a way that would welcome the UV rays. This resulted in fair skin being favored by evolution. For example, North America, Europe, and northern parts of Asia.
3. Between the equators and poles, sunlight is neither too harsh, nor too scarce. And this resulted in the skins being less dark, or simply brown. For example, the Native Americans, people in eastern and southern parts of Asia, all evolved with brown skins. This includes regions on or close to Tropic of Cancer.

Hope this article helped you guys. The references are numerous, so I had to use numbers instead of direct links. Now, I have a something to talk about, straight from the heart…

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A little chitchat about steemstem

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I read the posts regarding the steemstem reboot and the one by @mobbs where he wanted some time for himself. Actually, that reminded me of DOTA, which I used to play with my college friends. I am damn serious, I couldn’t resist playing it one more time. We all can be addicted to something, right? So I installed it again, and I just couldn’t resist playing it one more time, every time I played. And so I played it continuously, for three days (I luckily slept at night), and while playing on the fourth day, I realized I also had books and blogs to read, blogs to post, skills to learn, work to do, basically, I had a life to live… lol. I didn’t even exercise for three days, I felt terrible. And so here I am. I had to delete DOTA because it is awesome, but I don’t have the time to play even a single game, which lasts for about one hour. I don’t regret this entirely. It’s good to take some time off once a while. I enjoyed playing it a lot. It might have been better if I had travelled to some place instead of sitting my ass down in one place. The high school and college students will keep loving it… forever… I'd like to know about the games you play.

Now, about the steemstem reboot. I think I have a confession to make. Till the reboot happened, I thought of steemit only as a blogging platform instead of a social media platform. Now that this is superstition of mine is dealt with, I want to change things a bit as well. Now I want to treat not just as my readers, but also as my community.

1. The posts in #space that I have been posting are just because I wanted to post them. I love reading about space, it obviously doesn’t mean everyone else should too.

2. If I am to treat steemit as a community, I need to think about what you need to read, and what topics will be more helpful for you. All of you can’t be space enthusiasts, but all of you do have a life. And by “you have a life” I mean you truly care about at least one thing in your life, yourself. At most, you can care about a lot more - starting from family to the people around you, and about environment, animals, humanity, physical and mental health, economy, politics, education, knowledge, privacy, law and order, and what not, there really is no limit to this. Please keep caring, it adds more meaning to our lives.

3. Please don’t misunderstand the phrase “caring about yourself”. I don’t mean “be utterly selfish” by it. What I mean is - you need to look after yourself as well. As in my case, I am a teacher. I can’t really teach something unless I learn it first, can I? Or more simple example would be, we can’t donate money if unless we have some money. What I’m trying to say is - We have to care enough about ourselves in order to be selfless enough.

4. In this light, I will be starting a new series. In addition to what I currently have, I am adding renewable energy to the list. Because this is something we all must care about. Starting this week, I’ll be posting two articles per week. I don’t want just an informative series, I want to create a series that can teach something and raise the curiosity of even a 13 year old. I am ready to give this my best shot. And two articles per week are my limit, and sometimes they will be about space. But together, we can make lots of informative posts which can help people not just on steemit, but also all over the internet. I’d really like to know your views on this one, and to what extent can this be realized. We already have some decent articles about renewable energy on steemit.

Please do share your views on anything about this post, we are community after all. Thanks for your time, Take care.

References:
1, 2, 3, 4, 5, 6, 7, 8, 9,10