Solar Panel Efficiency: What,How To Find,Graph,How To Increase, Exhaustive Facts


We are familiar with solar energy. The solar energy from the sun can be converted into useful work or energy on the earth. One of the devices used to turn solar energy into electric energy is the solar panel.

The device solar panel can store and convert solar energy. The amount of sunlight that can convert into electricity is described by solar panel efficiency. A percentage always indicates the solar panel efficiency. This post is concerned with giving exhaustive details on solar panel efficiency.

What is solar panel efficiency?

The solar panel efficiency describes the input solar energy from the sun, and the output converted solar energy into electrical energy.

The solar panel efficiency is the measurement that specifies the ratio of the amount of sunlight that hits the surface of the panel to the amount of sunlight converted into useful electric energy. A solar panel consists of individual solar cells, which are made up of layers of silicon, boron, and phosphorus. The boron layer acts as a positive terminal giving positive charges, and the phosphorus terminal acts as a negative terminal consisting of negative charges. In contrast, the silicon layer acts as a semiconductor.

Primarily there are four types of solar panels. The solar panel efficiency varies for different kinds of panels. The panel which gives the highest electric energy is more efficient. The four types of solar panels are

Based on their components and ability to hold the sunlight and converting rate, all four kinds gives different efficiency rate. The efficiency of all four kinds is given below.

Monocrystalline solar panels

The monocrystalline solar panels are made up of only pure silicon semiconductors, so they are also known as “single crystal solar panels.All the silicon is cut into many wafers to arrange them to form a panel. Since only silicon is used in this type of panel; and hence its efficiency is more compared to the other three. The efficiency of the monocrystalline solar panel is about 20%. Even though the efficiency of this panel is more, it is not affordable as it has more wastage of silicon during the manufacturing.

Polycrystalline solar panels

The polycrystalline solar panels are made by melting the pure silicon and pouring them into a square mold. This type of solar panel is more affordable because the wastage of the material is less. The efficiency of the polycrystalline panel is quite less because the purity of the silicon is lost while melting. The efficiency of this type of solar panel is about 15-17%.

File:Polycrystalline solar panel sm mj2.jpg - Wikimedia Commons
Polycrystalline solar panel
Image credits: Wikimedia commons

Passivated emitter and rear cell panels (PERC)

PERC solar panels are the improved version of traditional monocrystalline panels. This is the new technology in which the passivation layer of the panel is on the rear surface of the cell and then enhances the efficiency. The efficiency of this type of panel is about 5% more than that of monocrystalline panels, i.e., about 25% efficient to capture and transform the sunlight.

Thin-film panels

The thin-film panels are different from the crystalline panels. They are made up of different materials, such as

  • Cadmium telluride (CdTe) –this type of thin-film solar panel has a low-cost advantage for the installation; however, cadmium is toxic, and its recycling may be more expensive compared to the installation. Its efficiency varies from 9-11%.
  • Amorphous silicon (a-Si) – this panel is made up of shapeless silicon, and it is not properly structured to the molecular level. The efficiency of amorphous silicon is about 6-8%. The advantage of an a-Si panel is it can give more efficiency at the lowest manufacturing cost.
  • Copper indium gallium selenide (CIGS) –this type of solar panel is made up of thin layers of copper, indium, gallium, and selenium, which are deposited on glass. Its efficiency varies from 13 to 15%. The combination of these elements produces the highest efficiency compared to the other two thin-film solar panels.

Solar panel efficiency formula

The efficiency of a solar panel is given by the formula

Efficiency(%)=Pmax/A*I*100

Where Pmax is the maximum panel power, A is the area of the panel, and I=1000W/m2; is the irradiated sunlight at standard test conditions.

If you know the value of the above terms, then you will easily find out the efficiency of your solar panel.

How to increase solar panel efficiency?

The solar panel efficiency can be increased by various methods. If the impurities of the semiconductor components present in the panel are removed, then the efficiency of the solar panel increases. But other than this method, we have several methods to increase the solar panel efficiency; they are:

  • Installation of solar power concentrator –The solar power concentrator consists of mirrors or lenses which concentrate on a large amount of solar radiation striking the receiver. This concentrated light from the concentrator is captured and hits the solar panel to optimum efficiency. The concentrator ensures all the available sunlight to involve in the process of generation of electricity. An extra advantage of the concentrator is that it can efficiently store the sunlight during the night also.
  • Correct angle to place the solar panel –the efficiency of the solar panel depends on the angle at which the panel is placed. If the panel is facing the south with the correct pitch, the panel will be capable of capturing maximum sunlight and also can generate more electricity. The panel must be placed slant because it helps to keep the panel clean and prevent dust particles from being on them.
  • Backup batteries –installation of backup batteries help to store the solar energy and can be made use of them during nighttime also. The captured solar energy by the panel will not waste if the backup batteries are provided and enhance the exclusive use of the sunlight; thus, efficiency is increased.
  • Offset temperature –the solar panels are largely affected by the outrange temperature, and their efficiency may decrease if the thermometer temperature rises. So it is better to install your solar panel with 6 inches gap between your roof and panel. So that wind carries the heat away, and efficiency increases by generating more electricity.
  • Keeping the panel clean –accumulation of dust, raindrops, and dirt may decrease the panel efficiency, so it is necessary to keep the panel clean.
  • Reducing the device number –use of too many devices simultaneously from solar power generators may destroy the panel efficiency. So it is better to use a limited number of devices to use. Avoid using devices that consume a lot of power, such as washing machines and refrigerators, because they may cause low voltage problems. If you avoid them, then solar panel efficiency will be improved, and the voltage problem will be solved.

Solar panel efficiency graph

The solar panel efficiency can be represented by plotting a graph. The graph of I-V and P-V is most convenient to plot the efficiency of solar power. In the I-V graph of solar panel efficiency, the voltage is taken along the x-axis, and the current is taken along the y-axis. In the PV graph, power is taken along the y-axis, and voltage is along the x-axis.

In the real world, the operating efficiency of a solar panel highly depends on external factors, such as climate and environmental conditions. Keeping these factors in mind, the plot of solar panel efficiency is given below.

solar panel efficiency
The graphical representation of solar panel efficiency

Solar panel efficiency over time

The efficiency of a solar panel gets reduced over time. If you installed a solar panel about five years ago, its efficiency is not the same now. As time passes, the efficiency of a solar panel reduces.

The rate at which solar panels lose their efficiency over time is called the degradation rate, and it’s a natural consequence. The degradation of the solar panel is a slow process; it takes a lot of time to lose its efficiency by 1%. In a study, the national renewable energy laboratory estimated that the efficiency of a solar panel loses by 0.5 to 0.8% every year from the installation.

The rate of degradation of the solar panel cannot be avoided, but it can be negligible over a year of time scale because the process of degradation is quite slow. The solar panel efficiency is lost over time mainly due to two reasons.

  • Light-induced degradation –this will happen only when the panel’s boron layer is oxidized and partially covers the panel. Due to light-induced degradation, about 1-3% of the panel’s efficiency may be lost.
  • Potential induced degradation –this process occurs because of the electrical leakage on the panel due to high humidity and sodium build-up on the panel. It is the rarest situation to have occurred to damage the efficiency.

However, we can estimate the average life span of the solar panel considering their efficiency. A few years back, the manufacturers gave the average life span of a solar panel about ten years from the day of installation. But now, modern technology enhances the efficiency of the solar panel more, and its average life span is estimated at 25 years.

Average solar panel efficiency

The average efficiency of a solar panel lies between 15 to 18%.

Mono-crystalline and polycrystalline solar panels exhibit the average value of solar panel efficiency. The thin-film Copper indium gallium selenide panel exhibit at most 15% efficiency. The standard size of 60 cell panels with a power rating of 300-330 watts can have an average efficiency of 18%.

Maximum solar panel efficiency

Scientists have invented the solar panel of maximum efficiency using the new technologies and innovation under laboratory conditions.

They have invented a large solar panel that can convert direct sunlight into electrical energy, and their efficiency is estimated at 44%. This is the maximum solar panel efficiency that has ever been made till now. These solar panels are made of mono-crystal solar cells. These solar panels are made by reinforcing the multiple layers of the cell into an individual cell, which is capable of absorbing all the radiation from the solar spectrum directly.

  • The scientists make use of new technology called “transfer printing,” which assembles each one of the components of the cell with high precision.
  • The material used in this panel is derived from the “gallium antimonide (GaSb) substrate,” which is mainly used in the manufacturing of IR lasers and photodetectors. It has the ability to absorb every part of the direct solar radiation.

But it is hard to achieve and customize such solar panels of maximum efficiency because it is highly unaffordable. The cost of manufacturing is also high and risky.

Highest solar panel efficiency

The highest solar panel efficiency is about 25%; a solar panel called PERC is capable of producing the highest efficient solar panel output electricity.

The highest efficient solar panel available in the market is 22.8% efficient. X22 is the monocrystalline solar panel that has the highest efficiency. A polycrystalline solar panel can have the highest efficiency of 17%. So monocrystalline solar panel has the highest efficiency.

How to calculate solar panel efficiency?

The efficiency of a solar panel can be easily calculated if you know the output power of the solar panel, the area of the panel, and how much sunlight is irradiated on the panel. Substituting the value of these data provided, the solar panel efficiency can be calculated by using the formula;

Efficiency(%)=Pmax/A*I*100

For better understanding, let us solve a problem for you. A solar panel has a maximum output power of 310 watts, and its area is 2.2 m2. The irradiation of the solar light is chosen according to the standard test condition (STC). Calculate the solar panel efficiency.

From the above question, we are provided with the maximum output power Pmax=310 watts and the area of panel A=2.2m2. According to standard test conditions, the irradiated sunlight on the panel is assumed to be 1000 watts/m2.

Substituting all the values in the given equation

Efficiency(%)=Pmax/A*I*100

Efficiency(%)=310/2.2*1000*100

310/2200*100

Efficiency(%)=0.1409×100

Efficiency(%)= 14.09%

The efficiency of the given solar panel is about 14% which is a little less efficient. We can also predict that the solar panel may be a thin film panel based on the value of their efficiency.

Frequently Asked Questions

What are the factors that affect solar panel efficiency?

There are several factors that largely affect the performance of the solar panel and subsequently reduce their efficiency; they are

  • Temperature –it shows the converse effect on the efficiency. If the temperature rises, the efficiency drops, and if the temperature falls, the efficiency will be more.
  • Energy conversion –solar panels exhibit different responses for different spectrums; this may lead to changes in the spectral irradiation, which affect the production of power.
  • Solar shading –solar panels are made in such a way that many single solar cells are arranged in series and connected together to produce high voltage. If a single cell is shaded means, all other cells are virtually shaded, which leads to loss of energy.
  • Orientation of the panel, angle of inclination of the panel, latitude, and the climate also largely influence the solar panel efficiency.

Can we achieve 100% solar panel efficiency?

Ideally, yes, we can achieve a 100% efficient solar panel if it is capable of capturing and converting all the irradiated sunlight. But practically, we cannot.

The solar spectrum consists of photons with a wide range of energies. Some photons may have energies more than the bandgap of a semiconductor, and thus, absorption of all radiated sunlight is not possible. So 100% efficient solar panel is hard to achieve.

What are the advantages of solar panels?

Since solar panel holds the solar energy, which is a renewable source of energy, so it has a wide range of advantages which is given below:

  • It converts solar energy into electric energy without the emission of any toxic substance, so it is eco-friendly.
  • Even though the initial investment is quite expensive, maintenance does not cost much as it does not require any other fuels for the generation of electricity.
  • Implementing solar panels to provide electricity to run household devices can reduce the electricity bill.
  • Installing the solar panel and correct utilization of them leads to reducing the use of fossil fuels which are non-renewable sources of energy.

What is the main reason behind the efficiency of a solar panel?

The solar panel efficiency relies on the semiconductor used in the production.

Suppose a panel is made by a pure semiconductor or doped with a negligible amount of impurities; that panel exhibits more efficiency. Less amount of impurities enhances the creation of more electron-hole combinations and thus makes use of total captured energy. So that efficiency will be more.

Keerthi Murthi

I am Keerthi K Murthy, I have completed post graduation in Physics, with the specialization in the field of solid state physics. I have always consider physics as a fundamental subject which is connected to our daily life. Being a science student I enjoy exploring new things in physics. As a writer my goal is to reach the readers with the simplified manner through my articles. Reach me – keerthikmurthy24@gmail.com

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