What is a solar panel and how does it work? (Ultimate 101 Guide)

What is a solar panel and how does it work? (Ultimate 101 Guide)
What is a solar panel and how does it work? (Ultimate 101 Guide)

Each day more and more people are switching to renewable energy technologies not only to reduce their carbon footprint but also to save money, as electricity is expensive. A solar photovoltaic panel, or just a solar panel is one such technology that helps you generate electricity from our free and abundant source of sunlight, without producing any harmful emissions or pollution.

But what is a solar panel and how does a solar panel work to generate electricity?

In this article, Engineering Passion will start by exploring the basics of solar panels and how they operate in a solar-powered system. We’ll also take a look at some common questions such as: How do solar cells generate electricity, what is the science behind the process, and outline the pros and cons of using solar panels.

It’s time to learn all about this amazing technology! 

1. What is a Solar Cell?

Solar Cell - The Fundamental Unit of Solar Panel
Solar Cell – The Fundamental Unit of Solar Panel / Image Courtesy of Engineering Passion

A solar cell is a device with certain semiconducting materials that can convert solar energy into electricity by inducing a current between the semiconductor layers.

The cell’s metal contacts allow the generated current to flow out of the cell for usage or storage.

A solar cell is also known as a photovoltaic (PV) cell. This name is appropriate since the word photo means “light”, and voltaic refers to “electricity”. In fact, a solar cell is the fundamental unit of the solar panel.

Solar cells are available in a variety of sizes and types depending on the demands of the user. Some are smaller than a stamp, others have a diameter of 5 inches (12 centimeters).

2. What is a Solar Panel?

A Typical Solar Panel
A Typical Solar Panel / Image Courtesy of Engineering Passion

A solar panel, or solar module, is an interconnected system of small individual solar cells. They generate electricity from sunlight through the photovoltaic effect.

A single solar cell can generate one or two watts of power as output [1] which is just about enough to charge a small LED bulb. Therefore connecting multiple of these cells together to create a larger surface area will produce more electricity than just one solar cell can. This chain of solar cells is called a solar panel or module.

Generally, there are three types of solar panels. Each one has its own advantages and disadvantages depending on your needs (e.g. budget ..) or requirements (e.g. efficiency, appearance..). These include monocrystalline (highly efficient), polycrystalline (more affordable, less efficient), and thin film (a cleaner look, more versatile, even cheaper but don’t last as long.) But for the purpose of this article, we can consider all these types of solar panels work the same way.

 

Most solar panels or modules are available in different wattages (w) from 100w to 350w. But can you link solar panels together to generate more power?

Solar Arrays – Generating Even More Power

A solar array is a collection of multiple solar panels
A solar array is an assembly of solar panels that generates more solar power / Image Courtesy of Engineering Passion

Solar panels are adaptable to your requirements. They may be linked together in whatever configurations your electricity demands require. Solar panels linked together are often referred to as solar arrays or solar tables. As a result, a solar array can be used to provide clean power from small residential use cases to large industrial scale; solar power plants or solar farms.

For example, suppose you require a 450-watt solar power system for your home or other solar projects. You can connect three 150 watt solar panels together to produce 450-watt power.

Let’s look at the science behind solar panels.

3. Science of Solar Panels – How They Generate Electricity?

Inside a solar panel.
Inside a solar panel. When the silicon atoms absorb light, electricity generation begins / Image Courtesy of Engineering Passion

Now you know that a solar PV panel = cell + cell + cell… The solar cells that make up a solar panel use the principle of the photovoltaic effect. Let’s have a brief look at the history of the photovoltaic effect and the first solar cell that actually used it.

The Photovoltaic Effect

The photovoltaic or PV effect was first observed in 1839 by French physicist Alexandre-Edmond Becquerel. Edmond first noticed that light can cause materials to make electricity[2].

Later in 1905, Albert Einstein studied the ties between light, matter, and electricity. He provided that atoms can take in electromagnetic radiation (such as light) and then give off electrons. This process was called the photoelectric effect. Einstein won the Nobel Prize in Physics in 1921 for his work on the photoelectric effect.

The First Solar Cell

It took until the early 1950s for scientists to realize that the photovoltaic phenomenon could be used in creating solar cells. The American engineer, Russell Ohl was the first person to come up with a working photovoltaic cell made of silicon like the ones used today.

He worked at Bell Laboratories in New Jersey. Although Ohl’s photovoltaic cell had less than 1% energy conversion efficiency it was enough to run ordinary electrical devices[3]. The solar panel efficiency has risen over the years, and it is now around 20%.

What Are Solar Cells Made Of?

Solar cells are made out of materials known as semiconductors which have unique properties when exposed to light (i.e., photons). These materials are called semiconductors. Their conductivity can be increased or decreased in useful ways.

The properties of semiconductors can be altered and controlled by introducing impurities to the material, this process is called doping.

A typical simple solar cell has two silicon layers. One is designated as n-type, the other is p-type. An excess of electrons exists in the n-type layer. And an excess of positively charged holes exists in the p-type layer. 

As shown in our diagram above, the solar cell has a depletion region, also called the depletion zone. This is the area around the p-n junction where there are no mobile charge carriers. The depletion region acts as a barrier. It prevents free electrons and holes from flowing between p-type and n-type semiconductors.

A photovoltaic cell usually has metal contacts on its tops and bottoms. Electric current flows out of these contacts.

How Do Solar Cells Work?

It all begins when the sunlight hits the solar cells! Here is a step-by-step explanation of how solar cells work to generate electricity:

  1. Step 1: When the silicon atoms absorb light, electricity generation begins. The light’s energy knocks some electrons out of the atoms (photoelectric effect). This causes them to migrate from the negative p-type layer to the positive n-type layer. 
  2. Step 2: This migration (movement) of electrons makes an electric current. This current is in DC (direct current) form.
  3. Step 3: The electricity in direct current form can then leave the solar cell through the metal contacts and be utilized by devices that can operate on direct current.
  4. Step 4: In order to power your home’s devices, the DC electricity is then converted to AC (Alternating Current) electricity using a device called an inverter. 
  5. Step 5: The AC electricity can then be used to power your home’s electrical devices.

Moreover, surplus amounts of solar electricity can be stored using batteries or transmitted to the utility grid (on-grid community solar system) a term called net metering.

4. Advantages and Disadvantages of Solar Panels

Advantages and Disadvantages of Solar Panels
Advantages and Disadvantages of Solar Panels / Image Courtesy of Engineering Passion

Up to this point, we’ve described what solar panels are and how they generate electricity. In this next section, we will wrap up with some of the key advantages and disadvantages of solar panels. 

Advantages of Using Solar Panels

  • Generating Clean Power Using Solar Energy

Solar panels are a renewable energy technology. They are based on converting solar energy into electricity without any pollution as compared to generating power from fossil fuels.

  • Reducing your Energy Bill

Energy bills have been skyrocketing over the past few years. A solar power system is an excellent way to reduce your monthly expenses.

  • No Noise When Generating Power

A solar panel system produces power silently using solar energy. It does not create noise pollution.

  • Easy To Install

Compared to other methods of producing renewable energy, solar panels are relatively easy to install and maintain.

  • Long Lifetime

Solar panels have a long life span, up to 25 years. Solar panels are designed with protection in mind. They have a layer of toughened glass that protects them from damage and dirt. Solar panels are well protected against external damages like hail. Moreover, they can also extend the life of a roof due to the layer of protection they provide over the roofing material. 

  • Can Be Used Anywhere

Some solar panels are designed to be portable. These portable solar panels can be used while camping, hiking, or traveling without needing access to a power source.

  • Low Maintenance Costs

Solar panels require a low amount of maintenance. And usually include a warranty on solar installation when done by a professional solar installer

Disadvantages of Using Solar Panels

  • High Initial Costs

Solar panels are a long-term investment. Although solar electricity is cheaper than regular electricity, a solar PV system installation can be very expensive compared to other methods of the power system.

  • Intermittency Problems (Variable Energy Output)

Solar energy is susceptible to weather conditions. Solar panels have variable energy output throughout the day.

  • Location & Sunlight Availability

Generally, solar panels work best in areas that have many sunny days throughout the year. Thus a solar power system will work less efficiently in areas that have limited sunlight e.g. on cloudy days.

  • Requires a Large Area

Solar panels require a large amount of surface area and solar installations are generally big. A solar energy system can be difficult to install around trees or other objects that may interfere with solar radiation reaching solar cells.

  • Cannot Be Used at Night (Requires solar energy storage battery banks)

Solar panels need sunlight to produce electricity. Thus solar panels can’t be used at night to produce energy. But, you can use battery banks to store solar energy produced during the day and use it at night, although this comes at a cost.

  • Low Efficiency

Solar panel efficiency is low compared to other technologies. Solar panels are an average of 15-20% efficient at converting solar energy into electricity.

5. Frequently Asked Questions

How long do solar panels last?

Solar cells have a lifetime of up to 25 years or more. However, other devices of a solar-powered system can have a shorter lifespan. For example, the inverters that convert solar energy into electrical power only have a life span as short as 10 years (on average).

Does solar panels installation require a high upfront cost?

Yes, solar panel installation can be expensive and require a higher initial investment (especially when it comes to solar panel efficiency) but solar technology is improving all the time. Fortunately, solar PV panels have very low maintenance costs and solar panel prices continue to drop.

How long does it take solar panels to pay for themselves?

Solar power has many benefits and costs that need to be considered. Solar PV panel ROI (Return on Investment) can vary depending on location, electricity pricing, solar irradiation of the area, solar panel efficiency, and government subsidies. On average, it can take solar panels up to 6-10 years to pay for themselves for most homeowners. [4]

What’s the difference between solar PV panels and solar thermal panels?

Solar energy has a lot of applications. Solar PV panels and solar thermal panels are two technologies that use solar energy. Solar PV panels, or solar photovoltaic panels, convert solar energy into electrical power. Solar thermal panels, on the other hand, only generate heat. The generated heat is then used to heat water.

Can solar panels be used anywhere?

Yes, solar panels can be used almost everywhere. However there are some key factors that make it an efficient source of energy including (1), solar panels are more efficient in places or geographic areas that receive more sunlight and (2) solar energy is inherently variable i.e. it is dependent on the time of day and also weather conditions. So it’s important to take into account the solar irradiation where you live to determine how cost-effective solar power is for your location.

When do solar panels (or arrays) generate maximum power?

Solar panels generate the most electricity when they are exposed to direct sunlight. 

As the angle of the sunlight changes throughout the day, in commercial or industrial large-scale applications solar arrays can be installed on a structure called a solar tracker. 

The solar tracker can enable the solar arrays to always face the sun and operate at peak efficiency. This also helps to produce power even when the weather conditions are hazy, misty, or foggy, although at a reduced rate.

Do solar cells convert all portions of received sunlight to electricity?

No, when light shines on a solar cell, a significant proportion of the energy is lost. Some light is reflected or transmitted through the cell. Some light is converted into heat. Only a certain part of the solar spectrum (light with the right wavelengths, or colors) is converted into electricity by the solar cell. A solar cell’s conversion efficiency is usually less than 20%.

Do solar cells work at night?

No, solar cells do not produce electricity during the night due to a lack of sunlight. At night, the number of photons that are hitting the cell is not high enough to displace the electrons. This means that there will be no electrical current. However, at an additional cost, you can set up a battery storage system. It will store surplus solar energy during the day and make it available for use during the night.

References:

[1] A solar cell can generate one or two watts of power.

[2] Edmond first noticed that light can cause materials to make electricity

[3] Ohl’s photovoltaic cell had less than 1% energy conversion efficiency.

[4] It can take solar panels up to 6-10 years to pay for themselves

Aimal Khan
Aimal Khan is the founder & CEO of Engineering Passion. He is an engineer and has obtained his bachelor's degree in energy engineering from Kandahar University.