How Solar Panels Work

I’ve often wondered how solar panels work. This flat panel sits motionless in the sunlight and instantly electrical current flows. As it turns out, certain materials exhibit a property known as the photoelectric effect that causes them to absorb photons of light and release electrons. When these free electrons are captured, an electric current results that can be used as electricity. The photoelectric effect was first noted by a French physicist, Edmund Bequerel, in 1839, who found that certain materials would produce small amounts of electric current when exposed to light. The photons from the light penetrate the material, which in the case of solar panels is silicon, the same materials used to make semiconductors, and dislodge electrons from the atoms. This flow of electrons is called current and it is picked up by a conductive material which is in turn is connected to the wires that provide DC current to say a motor or light bulb. As the sunlight becomes more intense, more electrons are dislodged and more electricity is generated.



 Source: National Energy Education Development Project (Public Domain) 



So won’t the material eventually run out of electrons? No, there is a complete circuit with a return wire bringing them back to the material. This is a basic overview of how solar panels work and the materials science and electrical design can be far more complex. Scientists are working to formulated materials and optimize the conduction to electricity from the solar cells while engineers are finding ways to drive down the manufacturing cost so that the cost of generating electricity from sunlight continues to decline. The following chart from the National Renewable Energy lab is a little complicated but if you look down the left side you will see grouping of efficiency in creating electricity for different types of solar cells. Keep in mind that while a design may be very efficient it can be very expensive to manufacture and not practical for residential use.


The first photovoltaic (photo = light, voltaic = voltage or PV for short) module, what is typically called a solar cell, was built by Bell Laboratories in 1954. It was billed as a solar battery and was mostly just a curiosity as it was too expensive to gain widespread use. We have NASA to thank for getting the ball rolling on affordable solar technology. In the 1960s, the space industry began to make the first serious use of the technology to provide power aboard spacecraft. Through the space programs, the technology advanced, its reliability was established, and the cost began to decline. During the energy crisis in the 1970s, photovoltaic technology gained recognition as a source of power for non-space applications.


The electricity generated by solar panels is DC or direct current, while the electricity supplied by your power company is AC or alternating current. You will need to connect the output of your solar panels to an inverter; a device that converts DC to AC power to make use of the electricity in your home. Some solar panels, called AC modules, actually have an inverter already built into them, eliminating the need for a large, central inverter, and simplifying wiring issues.


So what happens at night, or when the sky is overcast and no electricity is being generated? How do you operate your lights and other appliances? If you are connected into your power companies electrical grid you can get the power you need there. With some additional electrical equipment and the help of your power company, you can actually feed power from your solar panels into the electrical grid during the day causing your electric meter to run backwards. How cool is that! At night you use power from the grid but if the grid power equals the power fed into the grid during the day, you are operating a net zero electrical energy home. If you use less than the power you generated you would get paid by the power company. While having no electric bill sounds wonderful, it is currently difficult to achieve, especially if, for example, you need to run an air conditioner. It is possible to do but it requires that you are diligent about the amount of energy you consume. If you are using solar panels to generate electricity for a remote cabin, with no electrical service, you will need to have batteries to store the DC power to allow it to be used in the cabin overnight.


I visited a home in the city of Denver that was able to achieve this goal over the summer. What is most interesting is that the installation is a retrofit of a 1950’s home. There are plenty of trees so the panels are shaded from time to time and the owners are very conscious about their energy use. To see the performance of the solar panels on the home you see below follow this link and you’ll see what each solar panel is generating as well as how the system has performed over time (it’s really cool)

  The Robinson Home: 









I hope this sheds some light (pun intended) on the subject of how solar panels work.