How Does Solar Power Work? It All Starts With a Photovoltaic Cell



Exactly how does solar power work? Very basically, the sun shines its bright, hot light energy onto a photovoltaic cell. This cell is made of chemicals that are very good at storing this solar energy. This energy can be used immediately or later, depending upon what type of use is preferred. While that is a very basic explanation, to truly answer the question, “How does solar energy work,” we will need to break the photovoltaic cell (PV) down further, because it is the main ingredient required in all solar energy applications.

They are everywhere you look, on calculators, on homeowner's roofs and even on flashlights! The PV has become quite a common device in today's society, but what is it, and how does solar power work starting with a PV? A basic PV cell is just a silicon semiconductor made of two layers of very pure silicon. These cells are just 1/100th of an inch thick, and can last for over 25 years. The problem though comes when we attempt to enclose the two cells with some type of protective coating that will withstand weather conditions. It is actually these less rugged coatings and framework the eventually determine the ultimate life of the PV cell.

One PV cell by itself is not very beneficial to you and me, yielding only about ½ of 1 volt of electricity. That is why solar PV modules string these PV cells in parallel groups to create greater currents. A solar module is simply an assembly of lots of small PV cells, connected in parallel and series arrangements to maximize solar energy production. A module of 36 PV cells would then produce 18 volts. A typical size for a residential PV module is about 2 ½ x 5 feet, with a dark blue or black colored panel on top. This is framed in an aluminum frame, usually painted black.

So, how does solar power work as far as production in a residence? The amount of power produced by a common PV module is about 200 watts, and is determined by the surface area of the collecting panel, and how much sun strikes this area. When making PV cells, individual wafers of silicon are embedded with wires (contacts), and then coated with anti-reflective materials so the amount of solar absorption is ramped up to discount times when there is no sun shining, and to max out production of each cell, thus the whole unit.

These PV modules are then used to produce usable PV systems that contain many elements and devices intending to convert solar energy (DC) collected in the PV module to household current (AC) and to protect the end user and installer from shock, and do other things like store energy in batteries. How does solar energy work as far as the cost of modules? Complete PV systems cost a good bit of money, and can be used for a wide array of useful applications, but they will perform better or worse than others because of one important thing, the composition of the individual PV cell's structure.

So, when answering “How does solar power work” the answer is differently with different compositions. Single, or monocrystalline PV cell modules are the most efficient producers of solar energy. They can turn from 15 to 20 % of the solar energy they receive into usable electrical current. And cost about $3.48 per watt. These single crystals can also be cast into a multicrystalline ingot, but they lose some efficiency because where they are cast together, they consume some energy passing energy from one to the other crystal. They are usually 12 to 15 % efficient, and run about $3.29 a watt.

Finally, the monocrystalline cells can be processed into a thin film of amorphous silicon. This is the least efficient and least expensive PV cell structure, efficiency running only from 4 to 14 %, but costing only $2.50 a watt, with these prices dropping currently as new technology learns how to make them cheaper. Bear in mind an amorphous cell module will require almost twice the area to deliver the same electricity as a comparable monocrystalline structure.

Now that we know what PV cells are, let's look at the four determining factors for their electrical output. A module's current-vs-voltage curve (1-v curve), amount of sunlight received, the cell's physical temperature, and shading are the four main determinants in just how much a particular PV module harnesses. So, to really answer the “How does solar power work” question, optimally, if you have an area of brilliant sunlight most hours of the day, with little shade, and the ambient outdoor temperature is higher year-round and you connect a module to a load-drawing system that matches its production very well, you will have all the best case scenarios available, and may be able to get by with less expensive amorphous cell modules.

The 1-V curve of a cell means in an optimum situation, a module will be connected to a load that matches the characteristics of that module perfectly. The amount of sunlight a cell receives obviously varies from region to region, and the temperature of the cell itself will vary greatly from northern to southern climates, but not how you would think. How does solar power work? Not like you would think sometimes.

You would assume the more sun and heat the better. But because of the inefficiency of PV cell modules, once the temperature of a cell reaches a certain point, the extra heat just bleeds off and adds no gain to energy production. Just remember, high heat and high sun equal inefficient solar production. The perfect conditions are cool, partly cloudy days. Shading is self-explanatory, and comes in the form of trees, hills and other natural and man made hindrances blocking sunlight.

We hope that answers your, “How does solar power work?” and makes you feel more comfortable in starting your home solar power project.

Watch this short (less than 2 minute) animation about how solar energy works. It's a little blurry but the explanation is clear!


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