At this point, it's safe to assume that everyone knows the products they buy never do their advertised qualities or quantities any justice. Be it the bag of potato chips which has more air than chips or a car that just won’t touch the mileage its manufacturer claims. We're used to stuff performing below expectations and don’t mind it either.

Solar panels on the other hand, are usually excluded from such handicaps. Most consumers go into a solar purchase expecting their panels to produce as many watts as their sticker states, at least in the best of conditions.

Unfortunately, solar panels are no different from any other consumer product in this sense. In fact, don't be surprised at all if you find your panel’s output well below its rated capacity even on the brightest and sunniest of days when they are sparkling clean.

Here's why this happens.

What Can You Realistically Expect from Your Solar Panels

So, that 300 watt solar panel you've been researching probably doesn’t dishout 300 watts of power. But, just what is its realistic upper limit here? The answer depends on a few key factors.

Firstly, a solar panel's rated output is decided through rigorous laboratory testing. These tests are done in perfect conditions devoid of dust, clouds or any other pollutants with light shining directly on the panels at a perfect 90 degree angle. We've covered this in greater detail in our post on solar panel quality.

At first glance, such tests may seem deceptive since ideal conditions are rare, if not impossible. But, the objective of a solar output test is to determine the absolute power a panel can produce, which is an important figure to have.

So, how much of this power can you actually expect to harvest? Solar panels usually achieve only around 80% of their rated peak capacity, but may fall lower. A number of factors contribute to such losses.

What Causes Solar Power System Losses

Losses in usable power start to occur as the light falls on a solar panel. For the purposes of this article, we're going to ignore power loss due to environmental factors such as clouds, shade, dust, etc and focus on losses that are inherent in a solar power system due to its physical limitations. Here's a rundown of how it happens at each level:

Mismatch losses

Also known as the “mismatch effect”, power losses here are caused if solar cells in an array have different properties, resulting in inconsistent voltages. Mismatches can result in serious power losses since the entire system defaults to the output of the lowest performing solar cell.

Besides low power output, excess electricity trapped in the solar module's electric circuit is converted into heat that can further damage the solar modules. Mismatch losses can result in around 2% power loss.

Temperature loss

Solar cells perform best below 25 degrees celsius, which is also what the temperature they are tested against. The catch here is that these figures refer to the temperature of the cells and not that of ambient air surrounding the panels. So, the panels themselves can get much hotter than 25 degrees even if the ambient temperature is a cool and breezy 20 degrees.

A solar panel's power output can drop drastically as it gets hotter than 25 degrees. Power loss due to heat is measured as “Pmax”, which tells us how much a solar panel's electricity production drops per degree rise in temperature. For example, if a solar panel's Pmax is -0.45%, then that's how much electricity we lose per one degree celsius.

Temperature accounts for the majority of a solar panel's output losses and can range from 10% to as much as 25% in very hot conditions. Since mean temperature in most Australian cities can reach well over 30 degrees celsius during summer months when we have the most sunlight, the solar panels will also experience the greatest power loss here.

Light-induced degradation (LID)

LID typically occurs during the first few days after a solar installation and causes power loss due to build up of boron-oxygen compounds in the solar cell's silicon base. Some solar cells are more predisposed towards LID than others. LID accounts for 0.5% to 1.5% of power loss in photovoltaic systems.

P-type monocrystalline solar cells have higher oxygen content and are doped using boron and accept electrons, which makes them more susceptible to LID.

Multicrystalline solar cells are not as efficient as monocrystalline cells, however have less oxygen making them resistant to LID. Similarly, N-type silicon wafers are doped with chemicals that release electrons making them impervious to LID.

Cable and wiring losses

Solar panels are a collection of photovoltaic cells stacked in an array. These arrays feed into a wire that runs from the panel into the inverter. Since no wire is fully efficient, part of the power flowing through it is lost as heat.

For most solar power systems, cable related power degradation accounts for around 2% of the system's total loss, which can be brought down to 1% by using thicker wires or positioning the system such that it requires shorter wires to reach the inverter.

DC to AC Loss

Solar panels produce DC current that's unusable by household appliances. A solar inverter then converts that DC power into usable AC electricity which is fed into your home’s electrical circuit and the grid.

Since solar inverters are around 93% – 96% efficient, a portion of DC power being fed into them will be lost as heat. The exact amount of electricity lost will depend on your inverter make, and whether it’s oversized or not.

Oversized inverters (or, inverters that are rated for a higher output than the solar power system's total output) are more efficient than those that are matched to their panel's output.

Inverter Clipping

Inverter clipping happens when the DC power input from the panels is greater than its rated capacity. In such a case, the inverter “clips” or derates the overall output to match its own capacity, causing a loss in power.

How Can You Maximize Your Solar Power System's Output

The reasons for power loss we've discussed above are mostly unavoidable, because physics. However, we can also bring down such losses by designing efficient solar power systems.

For example, selecting solar panels with low or no LID potential, using sufficiently thick wires and cables, strategically sizing the inverter to mitigate clipping and positioning the solar panels such that they receive as much direct sunlight as possible can all help increase the system's output.

There are many factors that affect the power generation and efficiency of a solar station with the same capacity. Today SAIL SOLAR will lead you to have a studying.

 

1. Solar Radiation

When the conversion efficiency of solar panel is constant, the power generation of the solar system is determined by the intensity of solar radiation. Normally, the utilization efficiency of solar radiation by solar systems is only about 10%. Therefore, solar radiation intensity, spectral characteristics, and climate conditions must be taken into consideration. If the current year's power generation exceeds or falls short of the standard, it is likely that the overall solar radiation for that year deviates from the average.

 

 2. Tilt angle of solar panel

The azimuth angle of solar panel is generally selected in the south direction to maximize the power generation per unit capacity of solar station.

As long as it is within ±20° of due south, it will not have much impact on the power generation. If conditions permit, it should be as far as 20° to the southwest.

The above angle recommendations are based on installation in the Northern Hemisphere, and vice versa for the Southern Hemisphere.

Tilt angles vary from place to place, and local installers are more familiar with the optimal tilt angle for components. If it is a pitched roof, in order to save brackets, many of them will be laid flat on the roof, regardless of the tilt angle, for the sake of beauty.

 

3. Solar panel efficiency and quality

There are many solar panel types to choose from on the market, such as polycrystalline silicon, monocrystalline silicon solar panel, etc. Different solar panels have different power generation efficiency, attenuation and quality.

 

The most important thing is must purchase them from regular channels at a reasonable market price. Only in this way can you ensure stable and reliable power generation for 25 years.

 

4. Solar panel matching loss

Any series connection will cause current loss due to the current difference of solar panels, and any parallel connection will cause voltage loss due to the voltage difference of solar panels. Losses may reach more than 8%.

 

In order to reduce the matching loss and increase the power generation capacity of the solar  station, we should pay attention to the following aspects:

1)To reduce matching losses, try to use solar panels with consistent current in series;

2)The attenuation of solar panels should be kept as consistent as possible;

3)Isolation diode.

 

5. Temperature (ventilation)

Data shows that when the temperature rises by 1°C, the output power of crystalline silicon solar panel decreases by 0.04%. Therefore, it is necessary to avoid the impact of temperature on power generation and maintain good ventilation conditions for the solar panels. 

 

6. Effect of dust

The crystalline silicon solar panel is made of tempered glass. If it is exposed to the air for a long time, organic matter and a large amount of dust will naturally accumulate. Dust falling on the surface blocks the light, which will reduce the output efficiency of the solar panels and directly affect the power generation. At the same time, it may also cause a "hot spot" effect on the solar panels, causing damage to the components. solar panel station must be cleaned in time.

 

7.Shadows, snow cover

During the site selection process of the solar solution, attention must be paid to the light shielding. Avoid areas where light may be blocked. According to the circuit principle, when solar panels are connected in series, the current is determined by the smallest solar panels Therefore, if there is a shadow on one solar panels, it will affect the power generation of this solar panels. Therefore, when installing a solar power station, you must not be greedy for large capacity. You must consider the area of the roof and whether there is any obstruction around the roof.

 

8. Maximum output power tracking (MPPT)

MPPT efficiency is a key factor in determining the power generation of solar inverters, and its importance far exceeds the efficiency of the solar inverter itself. MPPT efficiency is equal to hardware efficiency times software efficiency. Hardware efficiency is mainly determined by the accuracy of the current sensor and the accuracy of the sampling circuit; software efficiency is determined by the sampling frequency.

 

There are many ways to implement MPPT, but no matter which method is used, the solar panel power changes must first be measured and then react to the changes. The key component here is the current sensor. Its accuracy and linear error will directly determine the hard efficiency, and the sampling frequency of the software is also determined by the accuracy of the hardware.

 

9. Reduce line losses

In solar systems, cables account for a small part, but the impact of cables on power generation cannot be ignored. It is recommended that the line loss of the system's DC and AC loops be controlled within 5%. The cables in the system must be well prepared, including the insulation performance of the cable, the heat-resistant and flame-retardant performance of the cable, the moisture-proof and light-proof performance of the cable, the type of cable core, and the size and specification of the cable.

 

Therefore, in daily operation and maintenance, we need to check whether the lines are damaged and whether there is leakage or other conditions. Especially after every typhoon or hailstorm, it is essential to check whether the lines and connectors are loose.

 

10. Inverter efficiency

The solar inverter is the main component and important component of the solar system. In order to ensure the normal operation of the power station, the correct configuration and selection of the inverter is particularly important.

 

In addition to the various technical indicators of the entire solar power generation system and the product sample manual provided by the manufacturer, the configuration of the inverter generally needs to consider the following technical indicators: 1. Rated output power 2. Output voltage adjustment performance 3,Overall machine efficiency 4.Start-up performance.

 

There are not many daily environments that affect the efficiency of the inverter. Pay attention to installing the inverter in a cool place and keep the surroundings ventilated to facilitate the heat dissipation of the inverter. Especially in summer and autumn, normal heat dissipation can maintain the power generation efficiency of the inverter.