Solar Panels: From Useless Toys to Devices of an Energy Revolution

According to an IEA report, the global capacity of solar photovoltaic (PV) systems is increasing rapidly and may soon exceed 1.5 TW.

Solar photovoltaic systems have already added 507 GW to global capacity, and forecasts suggest this figure could reach 1,500 GW by the end of 2024. This indicator exceeds the total electricity capacity of some countries, such as Germany and Japan.

Large-scale production and technological advancements steadily lower the cost of solar energy. According to the Mercator Research Institute on Global Commons and Climate Change (MCC), the price decreased by 87% over the past decade.

Before we answer questions about solar energy, let's define some key terms.

The term 'solar panels', previously published in world sources, refers to a device that stores energy in a solar power generated system. However, devices that convert light (specifically solar radiation or sunlight) into electrical energy are technically more accurately referred to as 'photovoltaic cells'. A set of such cells combined into a system is typically called a solar panel or photovoltaic (PV) module.

A module is likewise a set of identical or connected items arranged in a specific order. From this perspective, we can use the term 'solar panels' to describe an assembly consisting of numerous single-type items — photovoltaic cells.

In this article, we use all these terms to refer to devices that convert light, luminous flux, or solar radiation into electrical energy. They make green renewable energy accessible to a wide range of consumers and support its growth as well.

1. How long have solar panels been around?

The long history of solar energy began almost 200 years ago, evolving along with global advancements in science and technology. The starting point is generally considered the discovery of the photoelectric and photovoltaic effects. The next few steps were developing the first experimental samples of solar cells, making prototypes, and registering working concepts as patents for these technologies. It took a long time to conduct scientific experiments and wait for the technological breakthrough that could make the mass production of solar panels from photovoltaic cells both feasible and affordable.

Such breakthroughs occurred in the mid-20th century when several factors came together.

1. The photoelectric effect in semiconductors was discovered.
2. Mass-production technologies for semiconductor crystals based on germanium were developed.
3. Finally, a more cost-effective solution was found — instead of expensive germanium, cheaper silicon was used.

From this moment, the era of modern industrial solar panels began.

Since the mid-20th century, the efficiency of all photovoltaic solar devices has increased dramatically — from a fraction of a percent to several dozen percent. For instance, the conversion efficiency of concentrated photovoltaic (CPV) solar cells has reached 47.6%, while commercially produced silicon cells have achieved 22-26%. As a result, today, we can consider solar panels an innovative energy source.

Key stages in the development of solar cells and solar Panels

2. How do solar panels work?

The core component of a solar module (aka solar panel) is the photovoltaic/solar cell or layer (like amorphous Si, Perovskite, and others). It is a semiconductor device that operates based on the principle of the photovoltaic (PV) effect.

The electric current generation in a solar cell occurs as follows.

1. The fundamental particles of sunlight (photons) strike the solar cell and interact with the semiconductor material, for example, silicon.
2. Photons knock electrons out of the silicon atoms and then take their place.
3. Free electrons accumulate and create a potential difference.
4. A potential difference creates an electric field.
5. Under the influence of the electric field, the electrons move toward the electrodes of the semiconductor, creating an electric current.

This description offers a simplified view of how a solar cell works. In practice, a lot of factors influence the process. For instance, photons behave differently depending on their energy level. They can not only kick out an electron and take its place but also reflect off the surface or pass through the semiconductor. The process of the P-N junction at the boundary between two regions of the semiconductor with different conductivity types, its dynamics, the general properties of the semiconductor, and the specific materials matter as well.

The performance of solar radiation conversion is measured by efficiency, expressed as a percentage. Currently, the maximum efficiency of solar technologies in Russia reaches 25%.

The amount of electricity a solar panel can produce is determined by its nominal power, measured in watts.

3. What is the basic construction of solar panels?

A modern solar panel is a single unit in which photovoltaic cells are connected in series and protected by a layer of glass or polymer.

One cell produced by Unigreen Energy can potentially generate a voltage ranging from 0.3 to 0.65 volts, depending on environmental conditions such as light intensity and outdoor temperature. Dozens or even hundreds of solar cells are connected in series, where the positive terminal of one cell is connected to the negative terminal of the next one. The cells are encapsulated (i.e., sealed within a hermetic protective layer) between sheets of glass or transparent polymer material in the case of semi-flexible and flexible solar panels. This construction forms a solar module.

Metal frames, specific protective coatings, and additional stiffeners make it possible to adapt solar panels for operation in different regions. In the flexible and semi-flexible solar panels, we can apply different types of cover films. For instance, on boats and ships, we typically use lightweight modules based on polymer coatings with the highest level of resistance to saltwater.

Finally, the modules are assembled into complex systems using various fasteners, frames, and brackets. Along with other components (such as inverters, MPPT controllers, and other devices required for working with converted solar energy), the modules make up the PV system.

The largest and most complex type of photovoltaic system is a solar power plant (SPP). In addition to solar panels, SPPs include a full range of equipment that processes, converts, transmits, and optionally stores electrical energy, for example when creating off-grid (autonomical) or mobile stations.

• An inverter that converts the direct current (DC) generated by the semiconductor cells into alternating current (AC).
• A battery pack to store electricity.
• A stabilizer and charge controller.
• Cabling, AC/DC isolators, and a fuse box complete the system.

You can improve your SPP with a solar tracking device to track the sun's position. Plus, you can go even further and install equipment for smart solar systems. It will monitor the solar array's power, optimize it, and provide advanced monitoring and control features.

4. What are the different types of solar panels (modules)?

There are five main types of solar technologies used around the globe, classified by materials or combinations of materials.

1. Crystalline Silicon (c-Si)

That is the most popular technology that has existed in the global solar market from its inception. It involves using monocrystalline or multi- (polycrystalline) silicon wafers to create solar cells. Monocrystalline silicon is known for its higher purity and ordered structure, resulting in higher solar conversion efficiency. However, the solar industry commonly uses polycrystalline silicon as its manufacturing process is less expensive.

2. Gallium Arsenide

This technology uses gallium arsenide (GaAs) instead of silicon. The physical and electrical properties of semiconductors remain stable even under extreme conditions. They can absorb light across a broad spectral range and have a high mobility of electrons within the material when exposed to an electric field. This technology allows for very high efficiency, exceeding 30%. However, due to the high cost of raw materials and the complexity of the manufacturing process, GaAs cells are primarily used in the space industry.

3. Multi-Junction (MJ) Cells

Every cell of this type consists of multiple layers of semiconductors with their own different optimal light absorption spectrum. They are typically equipped with additional components, such as Fresnel lens concentrators, to increase solar insolation on the module's surface. Multi-junction cells achieve efficiencies exceeding 45%. Yet their production requires highly complex and costly processes involving rare materials and resources. As a result, their application is generally limited to high-tech scientific projects, such as NASA space missions.

4. Thin-Film

The technology involves applying layers of photoactive materials in the shape of thin films onto a substrate surface. It can use various materials, including amorphous silicon, perovskites, and other organic/inorganic compounds. Thin-film technology helps reduce material costs, but its efficiency remains relatively low. These cells are typically used in integrated architectural solutions, portable charges, and dedicated projects like navigation buoys in the marine industry and other low-power systems for remote sites.

5. Hybrid Technologies

As the solar industry grows dramatically, it encompasses a broad range of innovations and experimental technologies focused on finding a balance between increasing efficiency and reducing manufacturing costs of solar cells. These technologies leverage the synergy of various photosensitive materials. As the most rapidly growing segment in the solar industry, it focuses on overcoming current limitations and creating new opportunities for using solar modules in different fields.

Pros and Cons of Major Types of Solar Panels

5. Where Are Solar Panels Used?

The range of applications for solar panels is vast, spanning from tourism to industrial manufacture, from portable calculators to spacecraft, and from phone chargers to powering entire communities.

Here are some key ways we use photovoltaic systems in real life.

• Off-grid power supply systems

In remote areas, installing solar stations is often more cost-effective than extending power line networks. It is one of the most efficient ways to supply electricity to households or off-grid commercial projects in isolated regions. Solar panels can power water pumps, telecommunication systems, lighting, security systems, and surveillance cameras. Moreover, solar panels are widely adopted to supply power to standalone telecommunications towers, emergency communication stations along remote highways, and oil and mineral extraction sites.

• Foundation and component of energy complexes

Solar panels are increasingly integrated into larger power plants that combine various energy sources and technologies. They can function in a hybrid mode with an electric-thermal process, where solar energy is converted into heat energy. Solar panels can be integrated into electricity farms, operating along with wind turbines and systems that concentrate sunlight to enhance electricity generation efficiency. They can also be part of hydroelectric power generation.

• Integration into building's architecture

You can install photovoltaic systems not only on the ground but also on building's rooftops and facades. For instance, they can be integrated into roofing materials or structural components. Due to their non-standard sizes compared to ground-mounted systems, these solar panels maximize solar electricity generation while adding aesthetic value to architectural designs. Solar stations on residential buildings typically have output power ranging from 5 to 15 kW, while photovoltaic systems for commercial enterprises can reach several hundred kilowatts.

• Outdoor Lighting Systems

Today, solar panels are used to power streetlights, warning systems, and illuminated road signs in both major cities and small communities. It's particularly relevant to use them along rural highways, especially in high-risk areas.

6. Why Is Solar Energy Better Than Other Energy Sources?

When solar modules/panels were less efficient and not very widespread, the technology had only two main benefits. What were the pros? Solar modules use inexhaustible energy sources and are environmentally friendly. Indeed, solar energy resources are estimated to last for several billion years. Solar panels have no carbon footprint, generate no waste during electricity production, and do not pollute the environment with emissions.

As PV technology has advanced, other benefits of solar panels are increasingly evident.

• Reduced Energy Costs

Many people and businesses use solar panels to reduce their reliance on energy from external sources. First, they can reduce costs since some power is generated on-site. Excess electricity generated by PV modules can also be fed back into the grid and sold, further reducing energy expenses.

• Building an off-grid power system

In cases when laying power lines is either too expensive or unrealizable, SPP can fully supply a facility with off-grid electricity, making it completely self-sufficient.

• Low Maintenance Costs

Solar equipment has no moving or frictional parts. It means that once installed, it experiences minimal mechanical stress and is mostly unaffected by weather conditions. Maintenance is very simple. All you have to do is clean the panels from time to time.

• Performing under different lighting conditions

Although solar panel efficiency is directly related to sunlight levels, modern photovoltaic systems can generate electricity under various lighting conditions, including cloudy or overcast weather.

• Reliable and long-lasting

Most manufacturers of monocrystalline solar panels estimate a lifespan of 25–30 years. Indeed, the equipment delivers the expected performance within this time (provided that panels were installed and maintained properly). As technologies evolve, the reliability and lifespan of solar panels continue to improve.

• The increasing efficiency

Over the past decades, the efficiency of PV modules has steadily increased due to cutting-edge research and improvements in technologies. Currently, the efficiency of industrial-grade monocrystalline and hybrid panels is around 22–25%. However, ongoing technological development suggests that efficiency levels will continue to rise.

7. Are solar panels environmentally friendly?

The sustainability of photovoltaic systems deserves special attention, as manufacturers present solar panels as a technology that generates power with significantly less pollution compared to traditional energy sources, including fossil fuels.

Indeed, according to Science, one of the world's leading science journals, solar energy generates 800 times less waste than coal power.

In fact, the environmental benefits of PV modules are evident at each of the following three stages.

Manufacturing

The main element of advanced polycrystalline and monocrystalline solar panels is high-purity silicon, free from heavy metals and toxic chemicals. Every single manufacturing process is strictly controlled and optimized to minimize emissions and energy consumption. In Russia, the making of one solar module requires 66 kWh, while the panel generates 300–600 kWh per year during its operational lifetime, far exceeding the energy used in its industrial production.

Operation

Solar modules produce zero emissions and operate absolutely silently, without vibrations. It helps to preserve biodiversity in surrounding ecosystems. Plus, throughout its operational lifetime, this kind of equipment requires no maintenance (including component replacements or updates), further reducing human impact on the environment.

Disposal

International environmental standards classify heterojunction modules made in Russia under the fourth (lowest) hazard category. That means they pose no chemical or biological risks that may harm the environment or human health. Therefore, users can utilize them like regular household waste. However, the need for large-scale solar panel disposal in Russia will not arise until 2040, when the first SPP in Kosh-Agach reaches the end of its operational lifetime. We have covered the topic of solar modules disposal in detail in a separate article.

8. What Is the Future of Solar Panels and Solar Energy?

Since the second half of the 20th century, solar panels have evolved from being an impractical plaything, initially limited to space technologies, to devices capable of powering entire residential buildings and industrial facilities.

According to forecasts from the International Energy Agency (IEA), by 2026, the amount of solar energy will surpass the amount produced by nuclear power plants. By 2028, solar and wind energy in common can reach 42% of the total electricity power production.

The global solar industry is advancing in two main directions currently. The first is the widespread use of more affordable, though slightly less efficient, polycrystalline solar panels in projects of various scales. Second, ongoing technological advancements focus on making solar panels smaller, lighter, more visually appealing, and more efficient, all while reducing production costs.

Key Points of the Article: Brief Look

1. Solar energy started developing in the 19th century following the discovery of the photovoltaic effect. The breakthrough progress was driven by the expansion of more affordable semiconductor materials, such as silicon. Since then, technology has made significant advancements, positioning solar panels as a promising power source.
2. Solar modules operate based on the photovoltaic effect. When sunlight strikes the panel surface, this process releases electrons from the semiconductor and generates an electric current.
3. During the manufacturing process, photovoltaic cells are assembled into modules, which are then integrated into solar power plants (SPPs), enabling the generation of the required power output.
4. There are several solar technologies available, and they each have their own pros and cons. Monocrystalline silicon forms the basis for most widespread industrial solutions, including heterojunction technology (HJT), as it provides the best balance between cost and performance.
5. Various fields, such as householding, power production, agriculture, healthcare, transportation systems, and the space industry, use solar panels and related devices that provide reliable and environmentally friendly energy under diverse conditions.
6. An off-grid power supply and reduced electricity costs are just a few benefits of solar panels.
7. Solar panels are environmentally friendly. You can dispose of solar modules without harming the environment at the end of their operational cycle.
8. Due to continuous advances, solar panels are becoming more efficient and cost-effective. They could compete with other energy sources in the very near future.

Unigreen Energy is Russia's largest private energy company. We design and construct solar power plants (SPPs) for large enterprises and organizations with high energy consumption across the Russian Federation, CIS, Latin America, Asia, and Africa.

Our products deliver a power capacity of 1.3 GW per year. We bring our clients various cooperation models, including EPC (engineering, procurement, and construction), energy service contracts, PPAs, lease agreements, and green certificates.

Solar power plants are the best solution for businesses looking to reduce operational costs and ensure a stable and reliable energy supply. It is crucial for remote and hard-to-reach regions, where power supply is usually built on expensive fossil fuels. Our products can help you reduce dependency on price fluctuations and cut operational costs by 30%.

Interested in reducing your energy costs? Contact us to get customized solutions tailored right to your business needs. Email us at info@unigreen-energy.com, leave a request on our website, or call +7 (800) 505 91 63. We'll be glad to see you among our clients!