How Do Solar Panels Work?

You have probably seen at least one solar panel mounted on a roof, lamppost, or somewhere else. Solar panels are hailed as a remarkable piece of technology that is able to convert sunlight to electricity. But how do they actually work? 

Did you know that the idea of solar panels has been around for close to two centuries? 

In 1839, the French scientist Edmond Becquerel made an incredible discovery: certain materials would emit sparks of electricity when they came into contact with sunlight. Scientists began to harness this property, which they termed the “photoelectric effect”. 

A solar cell is actually a semiconductor – a technology you will find in almost every mobile device today. Solar panels are made up of many of these solar cells, or PV cells, which are the ones responsible for converting sunlight into electricity. When sunlight comes into contact with a PV cell, it produces electricity in the form of direct current or DC. 

The first photovoltaic (PV) cells, consisting of selenium, were invented in the late 19th century. These cells would be further improved on by scientists at Bell Labs in the 1950s, who used silicon instead of selenium to produce PV cells that were able to convert four percent of the energy in sunlight to electricity. 

What Makes Up a PV Cell? 

The PV cell is made out of two layers of semiconductor material, which normally consist of silicon crystals. Impurities are added to the silicon crystals in a process called doping to increase their conductivity, allowing electric current to flow easily. 

In the doping process, the bottom layer of the cell is doped with boron while the top layer is doped with phosphorus. This results in the boron and phosphorus bonding with the silicon to form a positive charge (P) and negative charge (N) respectively, so that the bottom semiconductor layer with positive charges is called “p-type” while the top layer with negative charges is called “n-type”. The surface between these two layers is called the P-N junction, and it is within this surface that electrons move and produce an electric field, allowing free electrons to flow from the p-type (bottom) layer to the n-type (top) layer. 

When the PV cell is exposed to sunlight, the energy from the sun causes electrons to be knocked loose in both layers. Since the electrons are negatively charged, they would naturally attempt to flow from the negative layer to the positive layer, but the electric field at the P-N junction prevents any electrons from moving in that direction. Thus, there is no electricity flow. 

Now imagine the PV cell is connected to an external circuit. This creates a path for electrons to flow from the n-type layer to the p-type layer. When electrons flow through this circuit, usually through thin wires connected to the top of the n-type layer, this causes electricity and current flow. 

You may have noticed that you will hardly find a lone solar cell functioning on its own. This is because a single cell generates only a few watts, which is insufficient to power most circuits. As such, the cells are grouped together to form what we know as panels. Panels are usually also grouped together to form arrays. 

Solar Inverters

Well, the direct current from solar panels is unable to power many circuits on its own, since many household appliances require alternating current (AC) electricity. As such, the direct current is usually converted to alternating current with an inverter, which can then allow homes to make use of the solar energy. 

Different solar panels have inverters in different locations. Some solar panel systems make use of just a single inverter for all the panels, usually called a string inverter. Other systems have a microinverter for each solar panel. 

A study was conducted at Appalachian State University in 2011, reporting that microinverters tested to be 20% more effective in unshaded conditions and 27% more effective in shaded conditions than string inverters. 

Disadvantages of Using Solar Energy

While solar panels are undoubtedly more environmentally friendly than using traditional electricity, they also come with downsides. For one, installing enough solar panels on your roof to power your whole house will cost you some hefty upfront payments. Making the change to solar energy almost always requires contact with a company, since it can be very complicated to figure out on your own. Fortunately, the price of solar panels has decreased over the years, and can help you save money in the long run. 

Solar panels are also relatively inefficient, requiring large amounts of space to produce their power. It is important not to confuse efficiency with how much power a panel can produce. The efficiency of a solar panel simply relates to how much space it takes up in proportion to the amount of power it can produce. It does not mean that a solar panel with high efficiency is working harder than a solar panel with low efficiency, only that the one with higher efficiency is smaller. It goes without saying that panels with higher efficiency tend to be more expensive, but this is generally not a concern for a single house unless roof space is tight. 

Moving may also be a difficulty if you have a solar panel system installed, as you would have to de-install the panels from your previous home and re-install them in your new home. Most solar panel homeowners would simply leave the panels there and arrange for the solar leasing company to switch the panel ownership to the new homeowner. Of course, you can always sell the house at a premium if it has solar panels installed, since the panels can save the new homeowner some money on electricity bills in the coming years. 

Solar panels may sound like they are eco-friendly, but actually, a study from Stanford has found that all the solar panels installed around the world are producing enough energy to make up for the energy it took for them to be created. Researchers projected that between 2015 to 2020, the solar industry would generate enough energy to cover all of the historic creation costs. 

Additionally, solar panels are not necessarily made of environmentally friendly materials. Since the solar panels we have today are relatively new in use and have a lifespan of about half a century, we have yet to observe how much of a solar panel can be effectively recycled. Solar panels are constructed out of glass, aluminum, plastic and copper, and as the years go by, the possibility of recycling these panels should be addressed. 

Activity

Considering the pros and cons of both sides, do you think solar energy will ever replace traditional electricity in our daily lives? 

Using solar energy is viewed as one way of conserving the environment’s resources. Identify another way of saving the environment. Compare and contrast these two methods. Which one do you think is more practical in the long run?