More and more homes and businesses are choosing to invest in solar panels, and there are several reasons for this trend. Firstly, the efficiency of solar panels has increased significantly in recent years, thanks to advances in the design techniques used to mount and place solar panels correctly. In 2019, the average efficiency of solar panels quoted by EnergySage was 19%. By 2024, the average efficiency will be around 21.4%. That's a huge improvement.
Second, governments are setting aggressive net-zero emission targets and companies are under increasing pressure to adopt renewable energy solutions to reduce carbon emissions.
Solar panels comprise many photovoltaic cells that absorb the sun's energy and convert it into electricity. Improving the efficiency of solar panels is vital for both individuals and businesses. In this article, we'll show you how to generate more electricity from the same space and reduce costs by increasing solar panel efficiency.
Solar panel efficiency
The efficiency of a solar panel is its ability to convert sunlight into electricity, usually around 20%. Let's say you have a monocrystalline solar panel installed on your house with a total area of 10 square meters and a typical efficiency of 20%. This means that the solar panel can convert 20% of the sun's rays into electricity.
High-efficiency solar panels can produce more electricity from the same amount of the sun. Their main advantage is using a smaller surface area to produce more electricity.
When choosing solar panels, the most important metric to consider is efficiency: how much sunlight a solar panel can convert into electricity?
Two main factors determine solar panel efficiency:
- Photovoltaic (PV) cell efficiency (based on solar cell design and silicon type)
- Total panel efficiency (based on cell layout, configuration, and panel size)
Cell Efficiency vs. Module Efficiency
It is important to note that the efficiency of an individual solar cell is not the same as the efficiency of the entire solar panel (module). While solar panels typically have efficiencies of around 15-20%, in some cases solar cells can achieve efficiencies of up to 42%. When evaluating solar panels, it is important to distinguish between cell and module efficiency.
Solar cell efficiency: This measures how efficiently an individual solar cell converts sunlight into electricity. It is calculated by comparing the electrical output of the cell with the solar energy received under standard test conditions (typically 1000 watts per square meter of irradiance).
Solar panel module efficiency: Module efficiency, on the other hand, takes into account the overall performance of the entire solar panel (made up of multiple solar cells). It takes into account factors such as inactive areas (such as gaps or edges between cells) and any losses in the connections between cells.
Why 100% efficient solar panels are unlikely？
Let's start with solar cells.
The efficiency of a solar panel depends on the performance of its weakest link, the cell. Solar cells are made from semiconductor materials such as silicon and convert photons of sunlight into electrons to produce electricity. The efficiency of a solar cell is the ability of the panel to capture energy from the photons.
However, not all photons are absorbed: some may be reflected when they touch the surface of the solar panel. Other photons may pass through the solar panel without being absorbed, again without being converted into electricity. Still, other photons are absorbed and converted into heat rather than directly into electricity. These processes result in some loss of energy. Some of the remaining photons will excite the photoelectric effect, which converts the energy of the photons into the kinetic energy of the electrons, thus generating electricity.
Solar cell design is an important goal in the field of solar technology. Scientists and engineers are working to improve the following factors to increase efficiency.
Material type: Monocrystalline silicon panels are typically more efficient than polycrystalline silicon panels.
Wiring and busses: Cells with multiple busses and passivation help to capture and transfer power efficiently.
Reflection: Minimising the amount of light reflected by the cell is also an important factor in efficiency. For this reason, cells treated with anti-reflective coatings perform best.
Researchers are also exploring new solar cell technologies, such as chalcogenide solar cells and polycrystalline silicon solar cells, which promise to further increase the efficiency of solar panels. But there will never be a way to make cells that are 100% efficient!
What is the efficiency of solar panels?
Solar panel efficiency under standardized test conditions (STC) provides a standardized benchmark for comparing the performance of different solar panels. Such standardized test conditions help consumers and industry professionals to better understand and compare different models and brands of solar panels.
STC is determined by exposing the panels to a constant light source and temperature and measuring the current and voltage generated by various load resistors. It applies to a cell temperature of 25°C, an irradiance of 1000 W/m 2, and an air quality of 1.5.
Efficiency = ([Pmax/area]/1000) x 100%.
According to the STC, a one-square-meter solar panel with an efficiency of 15% will produce 150 watts of electricity.
However, the real-world efficiency of solar panels can be affected by several factors that can cause them to produce electricity differently from the theoretical values under STC. Some of the factors that affect the actual efficiency of solar panels include:
- Temperature
- Lighting conditions
- Shade and shading
- Dust and dirt
- Module matching and system design
- Weather conditions
Taking these factors into account, the actual solar panel efficiency may be slightly lower than the value measured at STC.
What are the most efficient solar panels?
Monocrystalline silicon panels are currently the most efficient type of panel. A monocrystalline silicon cell is a solid piece of silicon crystal that provides more space for electrons to flow, resulting in smaller, more efficient panels. However, they tend to be more expensive. Modern monocrystalline panels are manufactured using several different cell types, with the most efficient varieties being manufactured using high-performance N-type monocrystalline cells, giving panel efficiencies of up to 24.3%.
Polycrystalline cells are made up of many individual wafers fused. Polycrystalline cells are not as efficient as monocrystalline cells, with typical efficiencies below 20%, but they are less expensive.
Thin-film cells are thin and flexible enough to be ideal for small or portable applications, but not efficient enough for large-scale installations.
People incorrectly assume that the efficiency of a solar panel equates to the quality of the product. Efficiency is just a product attribute, just like power rating, and you can find high-quality panels with various efficiency levels. Monocrystalline solar panels are the most efficient type of solar panel compared to others, but they are also more expensive. However, if you have enough space to install a photovoltaic system, using less efficient solar panels can be a viable option.
How to make solar panels more efficient?
High-efficiency solar panels are always expensive. If you have limited space, you can choose other configurations and take some measures to increase solar panel efficiency.
Choosing the right solar system
The efficiency of the solar panels is also an important factor in determining the efficiency of the whole system. It is important that you fully understand your energy needs so that you can make informed decisions about how to use these devices more efficiently. This will reduce your overall consumption.
Ensure that the panel is free of debris
Dust and other debris that accumulate on the surface of the panel can affect light transmission and absorption. Less sunlight will reach the solar cells and the amount of electricity generated will decrease. Many manufacturers recommend that you clean your panels at least twice a year. Even if your system is located in an area where it rains frequently, all panels should be checked regularly for bird droppings, leaves, pollen, ash, and other contaminants and residue.
Some manufacturers are developing ceramic coatings for solar panels to reduce the amount of dust and other debris that covers the panels.
Cleaning solar panels properly
It's important to clean your solar panel correctly; the wrong tools and methods can shorten its life. Generally, solar panel warranties do not cover damage caused by incorrect cleaning methods. Here are some general guidelines to follow:
- Choose the right time: The best time to clean solar panels is in the morning or evening. Don't do it when the panels are very hot, as drastic temperature changes can cause cracks in the panels.
- Avoid using sharp tools: Use a soft cloth, sponge, or soft brush for cleaning as they will not cause scratches.
- Use the right cleaner: Choose a mild cleaner, such as one mixed with warm water or one specifically designed for solar panels, and avoid corrosive or abrasive cleaners.
- Avoid high-pressure water: Avoid washing solar panels directly with a high-pressure water gun or water jet, as this can damage the seals and circuitry of the panels.
- Clean carefully: Ensure that the entire surface of the solar panel is thoroughly cleaned, including the edges and connectors, to ensure that the entire surface can fully absorb sunlight.
- Check for damage: During the cleaning process, be sure to inspect the solar panel for any damage or anomalies, such as cracks or breaks, and repair or replace them immediately.
In the previous article, we discussed the detailed steps for cleaning solar panels.
Avoid installing solar panels in the shade
Solar panels can make the most of the sun's energy by converting it into electricity in places where there is plenty of sunlight. Shading can significantly reduce the efficiency of your solar panels. If your solar panels are connected in a string, a single shaded panel can reduce the output of the entire array.
In addition to avoiding installation in the shade, be careful to avoid shading from trees, buildings, or other shading objects. It can be difficult to completely avoid shading when installing solar panels. To get the maximum number of sunlight hours and light intensity for your solar panels, try to choose a mounting location that ensures the maximum amount of direct sunlight.
Get a professional installation
If not connected correctly, solar panels can experience voltage and current problems that can affect their durability and productivity. Professional installers have the experience and expertise to ensure that solar panels are correctly installed in the most suitable locations for maximum sunlight and efficiency.
Why is solar panel efficiency important?
Choosing efficient solar panels is a key factor in designing a high-efficiency solar system. Although highly efficient solar panels are more expensive, they offer a variety of advantages.
More efficient use of space
Efficient solar panel means using less space for more energy output. When space is at a premium, the efficiency of solar panels is critical to ensuring that enough energy can be harnessed.
But efficiency isn't everything when it comes to designing the right solar system. If you have enough space to install the number of solar panels needed to meet your energy needs, it's more cost-effective to use less efficient panels.
High temperatures have less effect
All solar panels lose a small amount of power when they heat up. This effect is temporary - once the panels cool down, they regain their lost productivity. However, if solar panels are continuously exposed to hot weather, the loss of production can accumulate over time. As a result, high temperatures can reduce the efficiency of solar panels by 10% to 25%.
High-efficiency solar panels tend to have a low-temperature coefficient, meaning that the electrical output of the panel drops less at high temperatures. Under the same conditions, polycrystalline panels have a higher temperature coefficient than monocrystalline panels, which means they are more affected by heat. This is a major advantage in hot regions where high temperatures can affect the performance of solar panels over time.
Economic benefits
Efficient solar panels can pay for themselves in a shorter period and save users money on their electricity bills over a longer period. This is important for both commercial and residential users of solar energy systems and can lead to better economic benefits.
Installing high-efficiency solar panels can qualify a system for more incentives, and because of the higher wattage of high-efficiency solar panels, a higher incentive amount can be earned.
Solar panel efficiency over time
The efficiency of all solar panels degrades over time, and the rate of degradation depends on several factors:
Light-Induced Degradation (LID)
Solar panels are constantly exposed to sunlight and UV rays, which can gradually damage various materials. These materials include solar cells, anti-reflective coatings, and other components. Over time, damage to these materials naturally reduces the cells' ability to absorb light and the protective materials' ability to reduce environmental losses. The efficiency of solar panels is reduced by an average of 1% to 3%.
Potential Induced Degradation (PID)
PID is the energy loss that occurs when there is a high voltage potential difference between the solar cell and other materials in the panel, including those used to connect the cells in series. Voltage, heat, and moisture can all cause potential-induced degradation. Studies have shown that PID can cause efficiency losses of up to 30 percent, making it one of the most serious problems.
Fortunately, not all solar modules experience PID effects. This potential loss of efficiency can be avoided by using Tier 1 solar modules from a quality supplier.
Ageing degradation
Solar panels are designed to last 25 to 30 years, during which time they are exposed to a variety of environmental conditions. Some common problems include microcracks in silicon solar cells or the use of adhesives that cannot withstand the thermal cycling expected inside a solar panel.
