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How Do Solar Panels Work?

residential solar power

In the last two decades, the share of solar energy in the global energy mix has grown significantly, which means that more and more homeowners are interested to learn “how do solar panels work” and how can a solar PV system to reduce their energy bills.

In this article, you will find an answer for this question, and many answers to other questions related to solar energy and solar power systems.

How Does A Solar Panel Work?

Solar energy is the most abundant source of free and clean electricity available for us here on the planet, and in order to harvest this power, we need to use photovoltaic solar cells (PV solar cells) that are converting the sunlight into electricity using the photovoltaic effect.

Photovoltaic effect refers to the process when two dissimilar materials that are in close contact start generating an electrical current when struck by sunlight or a different form of radiant energy.

Solar PV Cells Production

Photovoltaic solar cells made of silicon are used today to turn the sunlight into clean electrical energy (zero emissions) for free.

Sand is used to produce raw silicon, which is then converted into a gaseous silicon compound form.

In the next phase, the gaseous silicon is mixed with hydrogen to obtain highly purified ingots of polycrystalline silicon.

The ingots of highly purified polycrystalline silicon are then converted into silicon wafers, which will later become the heart of a photovoltaic silicon cell.

Inside the silicon wafer, the silicon atoms are bonded together, which means that they have no freedom of movement in the structure.

A solar cell is a wafer made of a semiconductor material (silicon in this case) that has three layers.

Silicon is the main material used in the production process of solar cells

The top thin layer contains silicon and a small amount of phosphorus (which has more electrons than silicon).
Phosphorus atoms have five valence electrons, which means that one electron for each atom is free to move.

This gives the top layer an excess of free electrons that can move freely and are turning the material into a more conductive one.

The top layer is called this way the negative type (n-type doping) because it favors the collection and transport of electrons.

The thin bottom layer contains silicon and boron (an element with fewer electrons than silicon).
Boron has three valence electrons will create one hole for each atom.

This gives the bottom layer fewer electrons that are free to move, and are turning the material into a less conductive one.

The bottom layer is called this way the positive type (p-type doping) because it favors the collection and transport of positive charges.

The middle layer is thicker and has slightly fewer electrons, making this layer a marginally p-type.

Thin metal lines (usually made of silver) are printed on the top n-type layer, and the bottom p-type layer is in contact with an aluminum plate.

The sunlight is turned into clean electricity trough the photovoltaic effect

When the sunlight (any type of light with the wavelength between 350 and 1,140 nanometers that is included in the visible spectrum) hits the top layer of the silicon solar cell, the light will be absorbed by the middle layer of the cell.

Ultraviolet wavelengths being short, will stop at the surface of the solar cell, while the infrared wavelengths being long, will pass right through the cell (or will be reflected back) because they can’t be absorbed.

The light wave reaching the middle layer of the solar cell, will knock electrons off the silicon atoms, setting them loose and will leave an area of positive charge (holes left by the electrons moved by the light wave).

The loose electrons will move towards the top n-type layer (which readily accepts electrons), while the loose holes will move towards the bottom reaching the bottom p-type layer (which readily accepts holes).

This process of moving electrons and holes will continue as long as the sunlight will shine over the solar cell.

The electrons and holes being separated (electrons in the top layer of the cell, while the holes in the bottom layer), the connected wire between the top and the bottom metal electrodes will provide a pathway for the electrons to move towards the holes.

This flow of electrons is the electrical current produced by the photovoltaic effect that takes place in the solar cell due to the action of the sunlight.

Solar panels consist of one or several solar cells

Because one solar cell produces only a few watts (usually between 3 and 5 watts), a solar panel will contain one or many solar cells.

A 270W solar panel that contains 60 solar cells, means that one cell has 4.5 watts.

A 335W solar panel that has 72 cells, means that one cell develops 4.65 watts.

A 5W solar cell can be enough to power a small device such as a tablet, phone, LED bulb, etc., but if we want to power a toaster or an appliance that requires a higher power, we need to use more solar cells (a solar panel) or even a solar panel system.

To power a household, we need to install a solar PV system that has a capacity of at least 5kW (kilowatts), and even such a medium solar panel system is not enough to power all the appliances used inside the house.

However, by installing even a small solar panel system (under 5kW), we can power some devices with free and clean electricity produced by the panels, which means that our energy bills will decrease.

How Much Power Does A Solar Panel System Produce?

Before deciding to install a solar panel system in the yard or on your rooftop, you need to know that your solar PV system will have an efficiency of up to 21 percent.

A 5kW solar panel system will generate during a sunny day in the summer about 4 kW per hour, and at least 20 kWh during the entire day.

The same 5kW solar panel system will generate during the winter (cloudy days) about 0.5 kW per hour and only 2.5 kWh during the entire day.

A 20kW solar system can reach its peak of 20 kWh at noon on a sunny day of summer, and a production up to 100 kWh during the day.

The same solar PV system will generate during a cloudy day of winter only 2 to 3 kW per hour, and up to 10 kWh during the entire day.

If you use high-quality monocrystalline solar panels (which have better production of energy, but are more expensive than polycrystalline solar panels), you can generate slightly more power for the same installed output (5 kW or 20 KW solar systems), but you will also pay a higher amount of money to purchase and install the system.

How Many Years To Recover The Investment In Solar?

Going solar is not cheap, and this is the reason why before deciding to go solar, you should know what is your energy consumption per day, month and year because judging after your number of sunny hours per year, you can estimate how much energy you can generate with your future solar PV system to see how many years you need to recover the initial investment.

Today, is way cheaper to go solar than five or eight years ago because the solar technology is getting cheaper as time passes.

Electricity prices are going up

However, electricity prices are only getting higher as time passes, and this is the reason why you should invest in solar as soon as possible because there are still available governmental incentives and federal tax credits, which could help you even today to go solar much cheaper.

Installing a 1 KW solar system will only help you to consume less power from the grid (during the day), and rely entirely on the grid during the night, which means that you will save a small amount of money (on energy bills) only during the day.

By installing a 5 KW solar system, you can consume zero energy from the grid during the day, and rely on the grid only for the night.

If your house is not a big energy consumer, you can also send some power into the grid during the day (thanks to net metering), which will save you even more money and can reduce the recovering time for your investment.

Summer is best season for solar energy production

Installing a larger solar system (over 5 KW) will definitely help you to entirely cover your household demand for energy during the day, and also to send power back in the grid.

Grid-tied solar PV systems usually break-even in 8 years, but due to the higher price paid by the utility companies for the energy send back in the grid in cities like San Diego, CA, Honolulu, HI, and in New York, you can break-even in 3 to 5 years.

However, in cities like Austin, TX and Seattle, WA, the utility companies pay less for every kWh send back in the grid, so you will break-even in about 12 years.

If you want to use the energy produced during the day by your panels over the night, you need a battery system to store that power.

This will mean energy bills close to zero, but because you will send less energy back in the grid, you will need more time to break-even.

Do Solar Panels Work In The Shade?

Any type of shade (even a small one) will affect the energy production of your panels.

Shade created by tall trees, buildings, etc. could seriously affect the energy production of your solar system (drop in power production and amps, while the voltage could remain the same), and this is the reason why you need to install the modules on a rooftop (or an area) with no shade.

If the shade has appeared after you installed the solar system, you need to wire the panels in parallel.

Wiring them in parallel will increase the amps and the power production, and will also increase the voltage (compared to the series wiring), and your energy production will be less affected by shading.

Final conclusion

Going solar is a wise move today because the price of solar went down and there are still governmental incentives and federal taxes to benefit from, which would help you to get your solar PV system at a more affordable price.

Don’t forget that the price of electricity at your utility company will only increase as time passes, and because solar becomes cheaper year after year, in about a decade from now on, almost every household will rely on solar energy because is free, clean, renewable and environmentally-friendly.

Article written by:

I write about the renewable energy sector, electric cars and climate change issues. I love nature and good food, so I travel all over the world to see new places and meet new people. Magda Savin

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