How Does Solar Energy Work From the Sun to My House?
How does solar energy work? You have to understand the basics of radiation, and then you'll understand which solar energy plan to roll out in your home. The rise in solar energy interest has grown in lock step with the proliferation of Photovoltaic (PV) cells, which have become popular as government subsidies and tax incentives have arrived on the scene. PV modules can cost quite a bit of money, so it is imperative you know the ins and outs of how solar energy works before you make the decision of which of the many PV systems to install. Every PV contractor and manufacturer will proclaim they are the best, but with some knowledge, you'll be able to decide for yourself once you answer the question, “How does solar energy work?”
The sun is just one large nuclear reactor, spending its every waking hour intent on converting mass into light particles called photons (remember Star Trek?). So, how does solar energy work in this nuclear reactor? Photons are always rolling along at the blazing speed of light, and the most important aspect for our purposes of these speedy light particles is its wavelength. The wavelength is the distance of measurable void between two successive wave peaks. The movement over that distance of the wave is the frequency. Frequency and wavelength have an inverse relationship, however, they have the same meaning as mirror image opposites.
How does solar energy work as far as wavelengths are concerned, you ask? Wavelengths are appropo to solar power systems due to the reactions they cause in them. Solar system modules and the solar power components that comprise them respond differently to different wavelengths. For instance, the sun produces a lot more infrared radiation than radiation we can see, and some solar power applications prefer one type of light over the other.
When you and I see an object, we are glimpsing light that has been transferred from that object to our eyes. When you view white, you are seeing all the colors of the light spectrum at once, and black is the absence of color, because it absorbs light. Obviously, black is a great color for solar power projects, because it can absorb the most light that falls on it.
You might be asking, “How does solar energy work, and is there even enough for our use?” Well, every day, the amount of sun light that falls upon our planet earth is 35,000 times the amount that the entire human population can use, which means we have free sunlight and solar power everywhere. On a clear, cloudless day at sea level, a total of 1 kWh of the sun's rays lands upon a one sq. meter surface. That is enough solar energy to power all the appliances in your home.
How does solar energy work to harness this powerful radiation that hits the earth in such plentiful quantities every day? Radiation just really means the entire light spectrum that makes up sunlight. When we are building a solar power system, we are concerned with how sunlight and the various components of our system interact. If we use the wrong parts for the job, our system will be inefficient.
Sunlight (radiation) reacts with matter in one of four ways. The matter either;
absorbs heat from the sunlight
reflects sunlight and heat
transmits various spectrums of sunlight
oscatters it ineffectively and unpredictably
So how does solar energy work through the different forms of sunlight reaction? Some surfaces transmit sunlight and radiation though it, but trap the heat. Obviously, this is a great characteristic for solar projects. When glass is immersed with iron silicon, very wide spectrums of light are transmitted and large amounts of heat are insulated efficiently.
And when a medium can not reflect or transmit every wavelength equally as well, it is said to be a filter. This is how we can make glass panes and sunglasses that block harmful ultraviolet light, but allow the other colors through, hence improving visibility while protecting against radiation at the same time. We can also use them when we glaze covers for solar power collectors. Obviously, we want the highest amount of sunlight to enter the collector, so this filter's properties are concentrated where the most sunlight is available, at the visible and near-infrared parts of the light spectrum.
A combination of transmitters, absorbers and or reflectors make up all materials. For instance, standard home windows reflect 15% of the light that hits them, and transmits the rest. That means that they are filtering 85% of the sunlight that strikes them. But also, the more sunlight has to pass through, the weaker its effect. When it is directly overhead, it can pass through our atmospheres easily. When it strikes at an angle in the morning and evening, much less sunlight, thus radiation, passes through.
That is what makes mid-day the hottest, and has nothing to do with the sun being closer to us. Another myth is that the sun is hotter in summer than winter, but that simply isn't true. The air temperature and the position of the earth dictate heat and radiation levels, just as in morning and evening.
How does solar energy work to convert all this brightness into heat? When a light particle (photon) strikes anything that is light absorbent, the light energy is transferred to heat. This is simply caused by the molecules of that object heating up, bouncing around and causing friction. This makes more heat. Heat is also known as thermal energy, and as you can see, thermal energy is just motion. You can understand now how hot things burn you. Their surface is moving incredibly fast on a molecular level. When it contacts your skin, which is still, it is like a spinning saw blade hitting wood. That's what burns you and leaves a scar.
A lot of solar power applications require light to be filtered through a surface, converted to heat, and then collected. But then it must be converted to usable energy, in our case, electricity, and moved to where we need it. Heat is capable of being moved, or transported, through convection, conduction or radiation.
In convection, energy is considered the transfer of heat as molecules travel within a fluid, or the transfer of heat between a moving fluid and a permanent, stable surface. Don't think of fluid as liquid. Air is considered a fluid, as are some gases. Hot molecules themselves actually move and trade places.
In conduction, unlike convection, energy is passed from one molecule to another in a single substance. The heat is what moves instead of the molecules themselves, and heat will always go from a hot surface or home to a cooler one. Copper is a great conductor of heat, and most other good conductors of electricity also conduct heat efficiently. Since glass does not conduct heat or electricity well, it is an example of an insulator.
Radiation is the simplest form of heat movement. Any object that heats up, emits some level of infrared radiation.
Since solar heat collectors' number one job is to gather as much light, radiation, as possible, you want a large surface area, but also , you would like the collector to be mounted to “follow the sun” so it captures the max amount of sun when broadcast at a right angle to it. You then want move that radiation into heat as efficiently as you can, and then transfer that heat to a usable medium like electricity.
How does solar energy work in a perfect case scenario? If you were creating the perfect material to store and then move heat after it was collected, you would want a very high heat tolerance and excellent heat conduction. Water is certainly cheap, but it is clear, so radiation passes right through. The above-mentioned copper is relatively cheap and, when painted black, excellent for absorbing, storing, and then transferring heat, and is used frequently in solar heat collectors.
Now that you have a better understanding of the answer to the question “How does solar energy work”, you can choose the right solar module for the job every time.