How do solar panels generate electricity? 

How do solar panels generate electricity? 

There is no doubt the energy cost crisis engulfing the nation has made a compelling argument for homeowners and indeed business owners, to look more favourably on the benefits of renewable energy. And in particular solar power systems with associated solar panel battery storage. 

Everyone knows that when the sun shines, solar panels generate low-cost energy to power a home or business, even when there are low levels of direct sunlight. But for most, that is where the science ends and little though is given to how these wonders of modern science actually work. 

Solar panels are older than you think      

The foundations for today’s efficient, low-cost solar panels were laid almost 200 years ago, when in 1839 French physicist Alexandre-Edmond Becquerel, while working with metal electrodes in an electrolyte solution noticed electric currents were produced when the metals were exposed to light. 

This phenomenon was the earliest observation of the photovoltaic effect, named after Italian physicist, chemist and pioneer of electricity and power, Alessandro Volta. Photovoltaic is the more technical term for turning light energy into electricity, but used interchangeably with photoelectric.  

In 1873 an English engineer, Willoughby Smith, discovered the photoconductivity of selenium while he was testing materials to be used in the manufacture of underwater telegraph cables and in 1883, American inventor Charles Fritts made the first solar cells from selenium.  

The next major advance came in 1953, when Bell Labs engineer Daryl Chapin, was trying to develop an alternative source of power for telephone systems and settled on solar power as one of the most promising. He tried selenium solar cells, but found them too inefficient.  

More experimentation led researchers to stop wasting any more time on inefficient selenium solar cells and switch to silicon. Then in 1954, Bell Labs announced the invention of silicon-based solar panels, demonstrating their breakthrough by using a solar panel to power a small toy Ferris wheel and a solar powered radio transmitter. 

The science within modern silicon solar cells  

Those first silicon solar cells were about 6% efficient at converting the energy in sunlight into electricity. Although a huge improvement over any previous solar cells, they were not even close to around the 30% efficiency of modern commercially available panels. 

The detailed science that explains how silicon-based cells work is quite complicated as you might expect, but here is a shortened version that offers a valuable insight for those interested in renewable energy and solar energy systems in particular. 

Silicon has some special chemical properties, with an atom made up of 14 electrons, arranged in three different shells, the outer one of which is only half full, containing just four electrons. 

The silicon atom will seek ways to fill this outer shell, so shares electrons with four close atoms – imagine the electrons holding hands with each other. This creates the crystalline structure that is central to the use of silicon in photovoltaic cells. 

Pure crystalline silicon is a poor conductor of electricity so has impurities introduced, such as phosphorus atoms. These have five electrons in their outer shell, which try to bond with neighbouring silicon atoms, but the spare electron has no silicon electron to bond too and is held in place by the positive proton in the phosphorus nucleus. 

When energy is added in the form of heat for example, such as one might find when exposed to direct sunlight, it can cause these spare phosphorus electrons to break free and wander around the crystalline lattice looking to form a bond, whilst carrying an electric current with them. 

Adding impurities to silicon deliberately is a process known as doping, which when performed with phosphorous results in N-type silicon (N for negative) because of the prevalence of free electrons.  

The second part of a typical solar cell is silicon doped with the boron to create P-type silicon (P for positive), which has free openings in its structure to accept the spare phosphorous electrons and it carries a positive charge.  

When you put these two different pieces of silicon together, the free electrons on the N side see all the openings on the P side and jump across to fill the holes. Where the two pieces meet, they mix and form a barrier that progressively makes it harder for N side electrons to jump to the P side.  

Once equilibrium is reached, we have an electric field separating the two sides, which acts as a diode, pushing electrons to flow from the P side to the N side only, as electrons easily flow the other way, but need help to get back. 

When photons of light hit the solar panel, their energy will break the electron-hole bonds. If this happens close to the electric field where the P-type and N-type silicon meet, the field will send the electron to the N side and the hole to the P side. 

If an external current path is provided, electrons will flow through this path to the P side to combine with holes the electric field has created there. This flow of electrons provides the current, the cell’s electric field provides the voltage and when combined, we have the power we need. 

More panels and solar battery storage makes sense  

Although it increases all the time, the only real solution to the low efficiency of new panels is to install more solar panels over larger areas and include a solar battery storage solution to power the property when the sun is not shining.  

Of course, the electricity produced is direct current (DC) which must flow through a wiring harness to an inverter, which converts this DC to alternating current (AC). In a post coming soon, we’ll look at inverters, how they work, why they might need replacing and the benefits the latest models offer. 

Once converted, it is this alternating current you can use to power lights, appliances, and other electrical items in your home or business. And of course, this AC must be converted back to DC for the energy to be stored in batteries connected to the system for a 24/7 energy supply.  

By understanding how solar panels work and taking advantage of available technologies, you can maximize the benefits of solar energy for your home or business. Investing in a quality photovoltaic system can save on electricity bills while providing clean, renewable energy for years to come.  

Including a battery storage system, also allows owners to benefit from night-time tariffs to fill their batteries using cheap grid energy, to be used during the day to complement the solar PV energy created when the sun shines, or takeover completely when it’s dark.  

If you need any more detail, or would like to discuss a solar energy system and battery storage solution to reduce your energy bills, please get in touch with the dedicated team here at Sunergy and we’ll talk you through the next steps. 

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