What Are the Basics Behind Photovoltaic Solar Panels?

 The worldwide adoption of clean solar power has exploded in the last decade.

Fueled by innovation, competition, and the urgency of transitioning from burning coal, natural gas, and other greenhouse gas-producing petroleum products to renewable energy, here’s never been a better time for homeowners to switch to solar.

In South Africa, load-shedding seems like it will never end — in fact, it’s only getting worse. Relying on Eskom to provide electricity for your home is far from a safe bet. 

With the right residential solar power system, you can achieve independence from the (extremely unreliable) utility grid.

There are more affordable solar panel options available in the market than ever. So much so that trying to make a purchase decision can be overwhelming.

But no matter the manufacturer or materials, all solar panels currently available to consumers convert sunlight into electricity using the photovoltaic effect.

Read on to discover the fundamental principles behind the solar revolution and how photovoltaic (PV) panels work. 

(Source: Energy Education)

What Is a Photovoltaic Cell, and How Does It Work?

Photovoltaic (PV) cells are the essential component of solar panels that capture energy from sunlight. 

PV (or solar) cells are thin semiconductors composed of layers of material — usually silicon — and conductive metal contacts. 

PV cells convert sunlight into direct current (DC) electricity through a process known as the photovoltaic effect. 

The photovoltaic effect is the foundation of modern solar technology — that’s why solar panels are commonly known as photovoltaic, or PV, panels. 

Without the photovoltaic effect, there would be no such thing as solar-generated electricity — or at least not as we know it today.

Solar cells capture sunlight — not heat. 

Sunlight is made of photons — minuscule bundles of electromagnetic radiation — better known as solar power. 

Inside each photovoltaic cell, two semiconductors form a p-n junction to create an electric field. Using the photovoltaic effect, the p-n junction inside each solar cell converts the sun’s photons into electricity.

Solar panels can (and almost always do) contain more than one solar cell. 

For example, a 400W rigid solar panel generally contains over 150 individual PV cells. The solar cells are interconnected beneath the panel’s surface, and the solar energy they capture, when combined, is output as direct current electricity. 

Solar panels don’t generate household (AC) electricity on their own. They must be connected to a portable power station or other balance of system (BOS). 

No matter what size your solar panel array is or which BOS manufacturer you choose, a solar power system must contain the following components: 

• Solar inverter
• Solar battery (optional for grid-tied systems)
• Charge controller (MPPT or PWM)

Depending on whether you buy an all-in-one solution like EcoFlow’s DELTA Pro or build a DIY solar power system, your BOS may contain additional components and features like an advanced battery management system. 

EcoFlow’s solar generators include all of the above and offer many additional features, including remote control with the EcoFlow smartphone app. You can monitor and control your portable power station or whole home generator from anywhere with an internet signal.

Opting for a plug-and-play solar power system — such as a portable power station or Power Kit — and rigid, flexible, or portable solar panels offers numerous benefits, not least of which is simplicity. 

Additionally, you don’t have to worry about the compatibility issues that often arise when you purchase solar panels and separate BOS components from different manufacturers.

What Is the Photovoltaic Effect?

With the shift towards sustainable energy now a global imperative, terms once reserved for textbooks have infiltrated everyday discussions. 

One such term is the “photovoltaic effect.” 

Photovoltaic is often shortened to PV — as in PV panels. Photovoltaic is pivotal for harnessing solar energy. It holds the secret to converting sunlight into electrical power. 

Understanding how the PV effect works provides a clearer picture of the underlying principles behind solar power. 

It also helps us appreciate the vast potential of solar technology. 

Let’s explore the foundational physics and evolution of this revolutionary technology.

(Source: Energy Education)

How Is Sunlight Converted to Electricity?

The science behind the photovoltaic effect intertwines with some of the core principles of modern physics. At the heart of this phenomenon is the photoelectric effect, a process discovered in the early 20th century that laid the foundation for our understanding of quantum mechanics.

The photoelectric effect reveals that when light — composed of packets of energy called photons —  interacts with specific materials, it frees electrons from their atomic bonds. 

A photon’s energy is directly related to its frequency. Only photons with sufficient energy levels (usually from the visible and ultraviolet spectrum) can dislodge electrons effectively.

In the context of solar cells, photons hitting a photovoltaic surface — typically a semiconductor like monocrystalline or polycrystalline silicon —  impart their energy to electrons. Once the electrons gain sufficient power, they become excited and move more freely.

Solar cells employ this principle by using two layers of doped semiconductors. The ‘n-type’ has extra electrons, while the ‘p-type’ has extra “holes.” When the energised electrons from the n-type layer try to return to a more stable state, they are attracted to the p-type’s holes. This organised movement of electrons, driven by the differences between the two layers, results in a direct electric current.

By marrying the principles of the photoelectric effect with clever engineering, the photovoltaic effect captures the sun’s vast energy and converts it into usable electricity. 

The elegant fusion of quantum physics and modern electronics is the driving force behind solar energy’s rise as the leading sustainable energy source worldwide.

Types of Photovoltaic Solar Panels

Three primary types of solar panels are available for residential use: monocrystalline, polycrystalline, and thin film cells. As outlined above, the solar cells are interconnected beneath the surface of the solar panel. 

Here’s a brief overview of the three types of consumer solar panels:

(Source: American Solar Energy Society)

Monocrystalline Solar Panels

Monocrystalline PV panels are by far the most established option on the market. Sleek and streamlined, the solar cells inside a monocrystalline PV panel consist of a single crystal of highly durable silicone. 

The silicon crystals are grown in a lab, and solar panel manufacturers cut and shave them into octagonal-shaped silicon wafers. Once the cells are processed into wafers, they are placed inside a solar panel frame. Their consistent octagonal shape makes it possible to fit more cells into a smaller frame than other cell types.

The downside of this manufacturing process is that it generates significant waste. Still, monocrystalline solar panels are often preferable because of their higher efficiency compared to other PV cell types.

Monocrystalline solar panels also typically cost more than polycrystalline panels. However, the additional upfront investment translates to more significant savings on electricity bills over time due to optimal efficiency. 

In this context, efficiency is a PV panel spec that measures how much sunlight that hits the photovoltaic surface is converted into electricity. 

Mono PV panels average around 20% efficiency. EcoFlow’s solar panels boast an industry-leading 23% efficiency rating. The higher the efficiency, the more electricity is generated using fewer panels and taking up less space.

Polycrystalline Solar Panels

Polycrystalline panels are comprised of multiple polycrystalline fragments melted together, resulting in their distinctive checkerboard appearance. They’re less pleasing aesthetically, less intensive to make, and produce less waste. 

These and other factors make polycrystalline PV panels slightly more affordable than monocrystalline. 

But the lower sticker price comes at a cost. Poly panels offer less efficiency than mono PV panels — partly because the movement of electrons is restricted because each cell comprises many silicon crystals instead of one. 

Polycrystalline PV panels typically have an efficiency rating of +/-15%. Mono solar panels offer up to 23%. What does that mean in the real world? You need more solar panels that use more space to generate the same amount of electricity with polycrystalline solar cells than mono PV cells.

Even if poly panels are cheaper upfront, their lower efficiency means that you’ll need more space — and potentially more panels — than you would with mono panels with the same rated power output. 

The less electricity you generate via solar power, the longer your solar payback period can potentially be. Solar payback is when the money you invested in your solar panel system is equalled or exceeded by the money you’ve saved on electricity bills.

Once you’ve achieved solar payback, your return on investment really kicks in. As long as you’re saving money on your electricity bills, that cash goes straight back into your wallet.

Money saved is money earned.

Carefully weigh the long-term benefits vs. short-term savings before deciding between monocrystalline and polycrystalline PV panels (and the solar cells within them).

Thin-Film Solar Cells

Thin film solar cells are a more recent development than monocrystalline and polycrystalline cells. They don’t generate as much electricity and are significantly less efficient than mono or polycrystalline solar panels. However, they suit some use cases due to their unique construction, flexibility, and low dimensional profile. 

Thin film panels use various materials, including silicon, cadmium telluride, and copper indium gallium selenide, to create sheets of photovoltaic material on top of a substrate. The silicon used is a non-crystalline silicon, as opposed to the solid silicon used in polycrystalline and monocrystalline modules. 

A glass layer lays on top to capture sunlight. A semiconductor layer is beneath, between two layers of transparent conduit. 

Their thin construction makes them flexible, and thin film panels can typically bend to fit irregular surfaces. 

Their unique construction usually puts thin film PV on the higher side of the price spectrum. Unless you need a flexible solar panel — for example, to install on the curved roof of an RV — thin film PV panels’ lower rated power and efficiency, coupled with a higher price relative to electricity production, make them a poor choice.

Even if you need the flexibility, there are flexible solar panel options that utilise monocrystalline cells and offer 23% efficiency. 

How Are Photovoltaic Cells Produced?

The production of photovoltaic cells varies significantly by type.

For example, both monocrystalline and polycrystalline solar cells use lab-grown silicon as their primary material. It’s the process of creating the cell that distinguishes the two.

Let’s focus on how the most efficient PV cells on the market are produced.

Monocrystalline Solar Cell Production: Step-By-Step

1. Sand Extraction
2. Melting Silica
3. Slicing Ingots
4. Wafer Assembly and Treatment
5. Construct p-n Junction
6. Coat Surface
7. Metalillize the Wafers
8. Create Contacts
9. Etch the Wafers
10. Phosphorous Diffusion
11. Connect (String) PV Cells Together
12. Lamination to Tempered Glass or Other Protective TransparentSurface
13. Assemble the Frame
14. Solar Panel Assessment Under Laboratory Standard Test Conditions

Frequently Asked Questions

Final Thoughts

Without the photovoltaic effect, producing electricity from sunlight wouldn’t be a viable option today.

Governments worldwide are encouraging citizens to embrace clean, renewable solar power. 

In South Africa, a recent government incentive offers residents a 25% credit against the upfront cost of solar panels.

There’s never been a better time to switch to solar and reduce your dependence on Eskom’s grid.

EcoFlow makes industry-leading monocrystalline PV panels in various constructions and wattages. 

Check out EcoFlow’s solar panel collection today!