How To 

How Solar Panels Work



Our ability to generate power has led to some pretty incredible advancements in society. Of course, as with anything else, there are downsides as well. The way we generate most of our power has hurt the environment and isn’t sustainable. One of the more prevalent alternatives that’s not difficult to apply to your own life is the use of solar panels. To find out why they’re a viable alternative, let’s look at how they work:



1. Here comes the sun.
The first thing to note here is that solar panels do not need direct sunlight in order to generate electricity. They won’t work at maximum capacity during cloudy or rainy days, but they don’t stop working entirely. When the sun is shining brightly, though, solar panels can convert up to 22% of the sunlight received. This number might seem dismal, but think about how much energy the sun gives off daily. In fact, it has been estimated that we could cover a relatively small patch of the Earth (say, the size of Spain) in solar panels and be able to provide energy to the entire world.

2. The photovoltaic effect.
The main action of solar panels is to convert sunlight, and it does this through the photovoltaic effect. Solar panels contain a layer of silicon cells, and when these cells interact with light, electrons start to move around which gets an electric current going. This is DC electricity, which means direct current. It needs to be converted to AC (alternating current) to be used by your home, which is what a solar inverter does.



3. Let there be light!
The converted electricity goes into your home and powers your appliances, even through the night. It does this by storing the energy either in a battery or in the electric grid. There’s a process called net metering where any excess energy you create goes back to the power grid, and this is kept track of by your utility company. You get a credit on your bill for the electricity you send back to the grid, which is just another benefit of solar energy.
 

kathyleen

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Jan 27, 2020
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Thanks for share this article. I think solar energy it's our future. We can save the planet!
 
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Dec 22, 2019
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The modern technologies give us an opportunity to improve our life to make it more comfortable. I even would say more independent. For myself I consider solar energy is a crucial at the moment considering the latest climate change.
And I decided to move forward to create my own design of solar power for my country house.
So, I built my own pole and at the top I placed the solar light which has three modes of light power. The pole itself weighs about 23 kg but the basement the most heavy part of this structure.
The main idea was to create an independent pole where you don't need to fix it to the ground or concrete. You can install this structure to any place of your country house or during the day just move it to any place to get the best charge from the sun.
I have attached some photos of my creation. Maybe it was not great idea to build these things but I must reassure you that it works perfectly. In addition you don't need to switch it on or off. Everything is doing automatically.
My best wishes!!!
 

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Dec 22, 2019
6
0
530
Thanks for share this article. I think solar energy it's our future. We can save the planet!
Dear Kathyleen!
Thank you very much for your comments and sorry for my late reply to you.
Well, I must admit I am so inspired by my solar light. I love it even though during the winter season as you might understand there is a shortage of energy!!!
My best wishes!
 
Jan 27, 2020
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SaraRayne, you might find the following of interest:

To understand efficiency of a solar panel, you must first understand its source of energy – the Sun.

Sun emits energy in a form of light which is composed of photons. Each photon has different energy and wavelength range (from ultraviolet to infrared). Photons are used by photovoltaic cells in solar panels to convert sunlight into electricity.

The cells are made of a semiconductor material (p-n junction), which facilitates generation of electric current when photons get absorbed. But a bigger part of sunlight that hits the cells isn’t converted into electricity. Why is that?

The problem with solar cell efficiency lies in the physical conversion of sunlight.

In 1961, William Shockley and Hans Queisser defined the fundamental principle of the solar photovoltaic industry. Their physical theory proved that there is a maximum possible efficiency of 33.7 percent which a standard photovoltaic cell (based on a p-n junction) can achieve to generate electricity from a light source [2]. In other words, if the sun’s direct light is received by a surface per area of 1,000 watts per one square meter, then the maximum power output that a solar panel could produce is 337 watts per square meter.

This physical limitation is known as the Shockley-Queisser limit and is caused by the physical process of photon absorption by the semiconductor material that knocks loose electrons from their atoms and then passes them to the conduction band within the solar cell. Some photons that hit a solar cell are reflected away from the cell’s surface. Out of those photons that are absorbed, some have their energy turned into heat in a process of internal recombination instead of producing electric current.

These efficiency losses are inevitable. There is no manufacturing process or technology development that can change this limit — at least not with silicon p-n junction solar cells.

The Shockley-Queisser limitation defines the theoretical level of maximum possible efficiency of a solar cell, but in the daily life, efficiency of solar energy conversion is affected also by other factors (discussed below).

Quick Navigation for Why Are Solar Panels Inefficient:

FACTORS AFFECTING EFFICIENCY
1. Hail, snow, ice and dust
2. Insulation resistance
3. Temperature
4. Solar panel type
5. Design configuration
Improving solar cell efficiency
NEW EFFICIENT SOLAR TECHNOLOGY
1. Reducing the shading effects of wires
2. Gallium arsenide triple-junction structure
3. Cadmium telluride thin film cells
4. The Perovskite wonder material

Standard Test Conditions for verifying solar panel efficiency
To establish the efficiency value, manufacturers submit solar panels to several controlled factors that can exist in real world applications. They do this testing to make sure that the design endures these conditions, while at the same time, they verify estimated efficiency (as it is visible in the electrical characteristics of the datasheet).

It is important to know that many manufacturers establish solar cell efficiency based on Standard Test Conditions (STC).

STC are set on maximum possible solar irradiance (1kW per m2), at temperature of 25 degrees Celsius or 77 degrees Fahrenheit, and an air mass of 1.5 (related to the thickness of the atmosphere) [4].

It is rare to have the same conditions in the real life. Temperature and irradiance particularly can be very different from those values.

Nominal Operating Cell Temperature to simulate real life conditions
That is why some manufacturers add the Nominal Operating Cell Temperature (NOCT) among their technical references.

The NOCT is a parameter closer to real life situations and is defined as the temperature reached by an open circuit cell in a module under the following conditions:

    • Irradiance of cell surface: 800 watts per square meter
    • Wind velocity: 1 m/s
    • Ambient temperature: 20 degrees Celsius or 68 degrees Fahrenheit
    • Temperature on the surface: 45 degrees Celsius or 113 degrees Fahrenheit
    • Mounting System: Open back side (to consider air circulation behind the solar panel for refreshing purposes)
Now that you know how efficiency is specified by manufacturers, we can proceed with the factors that are taken into account for the design of solar panels to maintain acceptable efficiency values.

What factors affect solar panel efficiency in daily life?

#1 Hail, snow, ice and dust

Hail could in extreme scenarios damage the surface of solar panels and reduce their efficiency by decreasing the amount of sunlight they absorb. However, you should also know that solar panels are durable and meant to withstand hail at a speed of 20 to 30 meter per second (45 to 67 miles per hour). For a better idea, it is estimated that a hailstone with diameter of 1 centimeter or around 0.4 inches falls at a rate of 9 m/s (20 mph). Solar panels should resist even two to three times that. You should be safe during that early spring overcast.

Thick layers of snow can directly block sunlight accessing solar panels and cut efficiency down to zero [6]. It is important to know that most solar panels can still work with a layer of three to four centimeters of snow (approx. 1.5 inches). If the layer is thicker than that, you should remove the snow.

Just like snow, dust and dirt can influence efficiency values on the same principle. When the layer is too thick to obstruct the light from reaching the solar panel surface, it will affect negatively how much energy the panel produces.

Ice is another element that affects solar panels’ efficiency between 25 to 100 percent, depending on the thickness of the ice layer. To prevent this problem, a silicon coating is applied to a solar panel surface, but even despite that it’s advisable to keep ice off your panels during the winter season [6].

#2 Insulation resistance

Besides the safety concerns, faulty insulation decreases solar module efficiency because current leakages can occur along the edges of solar panels. Be especially careful in areas with high humidity. Humidity speeds up corrosion of materials. Advanced level of corrosion eventually leads to insulation issues and decreases overall solar panel efficiency faster than expected.

Problems with insulation may occur in poor quality solar panels made of cheaper materials, or when solar cells are too close to the frame.

Insulation resistance is especially important for utility-scale projects as higher voltage systems require better insulation properties, which are linked directly to selected materials.

#3 Temperature of solar panels

Solar cells are sensitive to warmer temperature. Higher temperature outside means that the semiconductor material of solar panels gets hot quickly and slightly changes properties, which is linked to electrical losses and voltage drops.

It is estimated that an increase per one unit of temperature above the standard test temperature of around 25 degrees Celsius or 77 degrees Fahrenheit decreases the panel’s energy output by 0.25 to 0.5 percent (depending on the module type).

If you think about it: temperature increase of around 60 degrees Celsius (140°F) could reduce the power outcome of your solar panel by 17.5 percent. So, the effect of temperature can be significant in countries with hot climate. Long term exposure to hot temperature may also shorten lifetime of the material.

On the other hand, you do not need to worry about colder temperatures, as long as the sun shines and solar panels receive unobstructed sunlight during the day, they will be producing at around their estimated efficiency. The only common problem in winter in regard to solar energy production is that the number of sunny days is much lower when compared to summer, and your system generates less on a monthly basis.

Further reading: How Hot Do Solar Panels Get? Effect of Temperature on PV Panel Efficiency

#4 Selection of the solar panel type

Not all solar panels are the same, neither is their price, which very often depicts not only the quality of materials and durability of the product, but also solar cell efficiency in converting sunlight in electricity. In daily life this usually means that you need less solar panels with higher efficiency rating to produce the same amount of power from their surface than you would need if you selected lower efficiency panels.

The main difference in efficiency values of different panel types lies in the nature of how they have been manufactured and what semiconductor material they are made of. The most common semiconductor used in solar cells is silicon. In case of silicon, efficiency still differs based on the type of cells. The best quality are solar cells made of monocrystalline silicon, other common forms are polycrystalline or amorphous cells.

Thin-film solar cell closeup

Monocrystalline panels composed of a single crystal due to their structure allow for the best efficiency between 15 to 22 percent. Polycrystalline panels reach between 13 to 16 percent of efficiency and thin film panels made from amorphous cells have reached to 20 percent.

What also matters is how much light is reflected from the solar cell surface. The goal is to minimize light reflection and that is why many solar panels have special anti-reflection coating and are dark in color – black in case of monocrystalline and thin film panels and dark blue polycrystalline.

Further reading: What Are the Most Efficient Solar Panels for Residential Use on the Market?

#5 Design configuration of solar panels

Among other factors associated with the operation of solar panels, the selection of the orientation towards the sun and the presence of a solar tracking system has a great importance on overall efficiency of your solar system.

Your solar panels will have the best power output when the solar panel surface is perpendicular to solar rays. However, as the sun moves across the sky, their angle changes as well. What you can do to ensure direct irradiance is to install a tracking system. Its downside are higher installation costs.

Solar panel efficiency also changes over the time. Every year that passes after your solar system installation, the efficiency value drops by about 0.5 percent per year. Nevertheless, solar panel manufacturers have to guarantee that the performance of your solar system will not drop below 80 percent when in warranty, which usually lasts 25 years.

Finally, shading is also an important part of the design of any solar system. If your system is shaded for the sunniest time of the day, solar panel output will be affected severely.

New solar technologies to improve efficiency

Despite low efficiency rates among current solar panels, there are several innovative proposals and technologies that aim to change how efficient can solar panels get in the close future.

#1 Reducing the shading effects of wires

Among available proposals is the reduction of the shading effect on solar cells caused by bus bars.

Bus bars are located vertically and horizontally across a solar panel. They can be easily identified by any person as silver wires forming a grid inside a solar panel. They transport electricity generated by solar cells.

Bus bars on a solar panel

These wires, even as tiny as they are, reflect the incoming light in sections where they pass by. In the end, this translates into less irradiance received by solar panels, and therefore, generation of less power.

The idea is to reduce the thickness of these wires, or in the best case to eliminate their interference with the sunlight by placing them on the back of a panel. This would achieve a uniform smooth colored panel [8].

#2 Innovative gallium arsenide triple-junction structure

Another interesting feature that has been set in motion is the development of the new generation of powerful solar cells from gallium arsenide.

Gallium arsenide cells have a triple-junction structure (different from silicon p-n junction) that can be chemically modified to acquire more light radiation than ordinary cells.

Among remarkable advantages of these cells is:
  • Excellent ultraviolet, radiation and moisture resistance;
  • Great performance in the presence of low light;
  • Flexibility and low weight;
  • Efficiency values over 28.8 percent (!).
#3 Cadmium telluride thin film cells

As new compounds are used for the creation of solar cells, new methodologies are also evolving around the manufacturing process to provide high efficiency solar cells.

The solar energy market is ruled by silicon semiconductors, included even in the design of thin film solar panels, but in the short to medium term, new photovoltaic materials like cadmium telluride are starting to gain their share on the market, as promising materials for the development of thin film panels.

The obstacle for their large-scale market introduction arises during the manufacturing process.

Some components seem to be very unstable because cadmium chloride has to be used during the manufacture. However, a new manufacture approach could deliver positive results, if cadmium chloride gets replaced with magnesium chloride [9].

Unlike cadmium chloride, magnesium chloride is abundant and low cost resource that can be obtained from the seawater. This material can also boost efficiency of the thin film panels up to 15 percent.

Perovskite - the wonder material

The ultimate and most promising technology for improvement of efficiency is the perovskite component.

Perovskite, a compound of calcium, titanium and oxygen, offers the possibility to achieve efficiency levels above the current maximum of 22 percent at lower manufacturing costs.

The secret lies in the low costs of raw materials and fabrication methods (printing techniques) that do not require high temperatures and such a high precision as the silicon cells do.

How to easily improve efficiency of solar cells

When you would like to improve efficiency of your solar cells, you should consider the effect of factors discussed above. As you can see, there are some factors that cannot be influenced by you, such as weather and outdoor temperature, but some other factors can be controlled or selected to obtain the best possible efficiency.

The key to success is trying to tackle the factors that can be controlled.
For example: regular solar panel maintenance helps eliminate snow, dust, dirt and ice – all of which obstruct sunlight from effectively reaching the panel’s surface, and therefore reduce efficiency of solar cells.

By keeping your panels clean, you can nicely maintain their efficiency.

Other factors such as the type of a solar panel, its orientation, and the minimum shade configuration are crucial parameters that will determine overall efficiency in the long run.

Some important details that need to be considered are:
  • the solar irradiation value in your area;
  • average cloud density;
  • levels of air pollution;
  • the angle of solar panels depending on their location and a selected mounting system.
These parameters are generally selected by a solar designer but that does not mean that you cannot intervene in the process, especially in the selection of the solar panel type.

Solar panel orientation affects efficiency

Further reading: Solar Panels for Home: Will They Pay Off?

See: https://greentumble.com/why-are-solar-panels-inefficient/

There many factors relating to the inefficiency of solar panels and the foregoing article does a terrific job of explaining their shortfalls in electrical current production over time, due the outside elements and their innate current fluctuations due to the factors involved in their manufacture.
Hartmann352
 
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