Generating Electricity: Solar Cells

Let's Talk Science
Readability
6.88

How does this align with my curriculum?

Learn how energy from the Sun can be used to generate electricity.

The Sun is a source of energy we use to generate electricity. This is called solar power. In Canada, we had the ability to generate 2821 megawatts in 2019. This is more than 16 times what we could generate ten years ago. This is enough electricity to power about 260 440 Canadian households for a year. Although solar power only makes up about 0.5% of our total electricity generation, solar power is increasing in Canada.

Solar Power for Electricity

Solar power converts energy from the Sun into electrical energy. One way to do this is with photovoltaic materials. These can be used to create an electric current when they’re exposed to light. This is called the photovoltaic effect. Photovoltaic cells or solar cells can do this. Manufacturers often put lots of solar cells together to make solar panels

A solar panel is made of solar cells sandwiched between layers of clear adhesive film. In front of this is a layer of glass held by a frame. Behind is a layer of aluminum called the backsheet which can conduct electricity. The electricity generated by the solar cells leaves the solar panel at the junction box.

The various layers of a solar panel
Parts of a solar panel (Let’s Talk Science using an image by alejomiranda via iStockphoto).

How do solar cells work?

How do solar panels work? (2016) by TED-Ed (4:58 min.).

Solar cells are usually made from silicon. Silicon is a naturally-occurring chemical element. It is also a semiconductor. Semiconductors can act as both a conductor and an insulator

Did you know?
Silicon is the second-most abundant element on the planet, after oxygen.

A solar cell has two different layers of silicon. One is called the P-Type and the other is called the N-Type. 

The N-Type semiconductor can give away electrons easily. This semiconductor faces towards the light. 

The P-Type semiconductor can receive extra electrons. We call the spaces for these extra electrons “holes.” This semiconductor is underneath the N-Type one. 

Energy from the Sun comes to Earth in little packets of energy called photons. The photons knock the silicon atoms. This creates loose electrons on the N side and holes on the P side. The loose electrons are collected on the aluminum layer. Then they begin to flow. This forms an electric current.

photovoltaic effect showing parts of the semiconductor and movement of electrons
Photovoltaic Effect (Let’s Talk Science using an image by ser_igor via iStockphoto).

How much power can a solar panel generate?

One standard solar cell is 15.6 cm x 15.6 cm square. It can generate about half a volt of electricity. That is about one third of the voltage of a fresh AA alkaline battery. That’s not very much. 

Luckily you can connect solar cells together. Twelve photovoltaic cells is enough to charge a cellphone. Many solar panels are needed to power a house.

Solar panels standing in a field
Solar panels in a field (Source: querbeet via iStockphoto).

What is a solar farm?

You can often see many solar panels together. This is called a photovoltaic power station or a solar farm. Ontario is the solar power capital of Canada. Over 98% of Canada’s solar energy is generated in Ontario.

Graph showing sizes of largest solar pv farms in Canada
Some of the largest solar farms in Canada (2019) (Source: Natural Resources Canada).

 

Did you know?
The two biggest solar farms in Canada are Sol-Luce Kingston and the Grand Renewable Energy Park. Both have 100 MW of capacity. An even larger solar farm called the Travers Solar Project which will produce 465MW of power is expected to be built in Alberta by 2022.

 

Solar power can be especially helpful in remote communities, which often rely on diesel generators for electricity generation. Getting the fuel to them is difficult and burning it to generate electricity releases greenhouse gases. In Fort Chipewyan, in a remote part of northeastern Alberta, a solar farm opened at the end of 2020 owned by three first nations groups. With the new solar panels, the community will burn 800 000 litres of diesel fuel less each year. This means 2 376 tonnes of carbon dioxide will no longer be produced.

Advantages of Solar Energy

Solar power is a renewable source of energy. This is because the energy from the Sun will not run out. Fossil fuels like oil, gas and coal are not renewable. Solar power is a clean way of generating electricity. This is because it does not produce greenhouse gases which make climate change worse. It also doesn’t produce air, water or noise pollution when the panels are operating. But like almost anything we make, pollution is produced when solar panels are manufactured, set up and disposed of. 

Disadvantages of Solar Energy

Solar panels generate the most electricity when the Sun is shining. They don’t work as well on cloudy days. They also work better when they are placed closer to the equator because the sun shines more directly on them, and in the summer here in the Northern hemisphere. Solar farms need a lot of land. This is land that could be used for other things like wildlife habitat or farms. 

Solar panels are not very good at converting sunlight to electricity. Most solar panels are about 20% efficient. That means only 20% of the solar energy it collects is converted into electrical energy. 


But even this is a big improvement on how it was only ten years ago and there is more good news on the horizon. A new solar panel has reached 47 percent efficiency in the lab and nearly 40 percent in the field. This means the future of solar electricity generation could be very bright!

 

Learn More

What is Solar Energy? (2017)
This video by SciToons (5:07 min) explains how all electricity comes from the sun and introduces solar electricity generation.

The Environment: Solar Power
This article by Ducksters explains how solar energy can be used for heating and generating electricity. 

Solar Panel (2020)
This article by Energy Education explains what solar panels are made from and how they work.

References

ACS Chemistry for Life. (n. d.). How a Solar Cell Works.

Delbert, C. (2020 April 20). This Solar Panel Just Set a World Record for Efficiency. Popular Mechanics.

Government of Canada. (2020). Renewable Energy Facts: Solar photovoltaic

Svarc, J. (2020 September 8). Most efficient solar panels 2020. Clean Energy Reviews. 

The Renewable Energy Hub UK. (n. d.). How do Solar Panels Work For Kids

US Energy Information Administration. (2020). Photovoltaics and electricity.