How much do you know about LONGI solar panels?

Longi Solar is a Chinese company founded in 2000.

Longi is the world’s leading monocrystalline solar wafers and panels manufacturer with a module capacity of 50 GW.

​It is a financially healthy company with a revenue of $ 8.416 billion (2020). It has global offices in:

• Japan (Tokyo)
• Europe (Germany)
• America (California)
• Australia (North Sydney)

Let us start the review of Longi solar panels.

Longi solar panel series

It manufactures high-power solar panels both for residential and commercial use with a power rating from 355 watts to 550 watts.

Hi-MO 4 Series

In this series, you find mono-facial and bi-facial solar panels by Longi.

Hi-MO 4 series (Monofacial)

The technology of Longi solar panels

Longi has implemented the latest technology for its solar panels.

• Gallium doped silicon cells
• Half-cut solar cell technology
• MBB technology
• PERC solar cell technology
• Bi-facial solar panels

Gallium doped silicon cells

It is using Gallium-doped silicon (instead of Boron-doped) for its P-type PERC modules.

The Gallium-doped silicon is more effective in checking the LID (Light Induced Degradation) effect in the solar cells than the Boron-doped silicon cells.

The oxygen traces in silicon react with boron in the presence of sunlight, forming a complex compound that prevents the free electrons from the photovoltaic effect.

This results in degradation in short circuit current and the open-circuit voltage, affecting the power output of the solar cell.

It was found that this degradation is proportional to oxygen concentration and boron concentration.

If somehow, we could control the concentration of either of two, we can reduce the LID effect in the boron-doped solar cells.

But reducing the oxygen content is very difficult and costly.

And

Replacing boron with gallium as a dopant is feasible and it solves the LID problem.

The LeTID (Light and elevated temperature induced degradation) defect is also controlled with Gallium doped silicon.

In short, the anti-LID performance of Gallium-doped silicon is better than that of boron-doped equivalent.

This implies Longi is investing a good amount in R&D and experimenting.

Half-cut solar cell technology

Its panels are based on half-cut solar cell technology.

When you cut solar cells in halves and join them together, you get a half-cut solar cell-based solar panel.

This technology offers many benefits than the conventional solar panels such as:

• Reducing shading losses
• Checking heating loss
• Improving the strength of the solar cell

Multi-Bus Bar (MBB) technology

Longi uses MBB (Multi Bus Bar) technology in stringing the cells together for improving the power output.

Their round shape increases the light scattering and more light falls on the solar cell after striking from the bar edges.

The multi-bus bars that connect the cell help in controlling the heating losses by reducing the current path.

In addition, these round busbars have less area than the flat ribbons, allowing more light to fall on the cell and you get more power.

PERC technology

Also, Longi pastes an extra layer (Passivated Emitter and Rear Cell) at the back of the solar cell that increases its overall efficiency.

Bi-facial solar panels

In addition, its bi-facial solar panels generate current from both sides and produce more power than the traditional mono-facial solar panels.

Let me tell you, the output from the rear side of the solar panel depends on factors:

• Mounting structure
• Height of the panels from the ground
• Solar panel tilt
• Albedo

That can give a bi-facial gain room 5% to 30%.

The efficiency

The maximum efficiency of Longi solar panels is 21.5% of its LR5-72 HPH series (Mono-facial).

Read: The most efficient solar panels in the world

Hi-MO 4 series

Hi-MO 5 Series

Strength of Longi solar panels

The strength of the solar panel is its ability to withstand snow load and wind pressure.

These two ratings are measured in pascals.

The wind load rating of Longi solar panels is 2400 Pascals (rear load rating)

​and

the snow load rating is 5400 Pa (snow load rating).

How well do Longi solar panels perform at high temperatures?

The performance of any solar panel at a high temperature is measured by its temperature coefficient of power.

It measures the loss in power output with every degree rise in the cell temperature beyond 25° C.

It is written negative and measured in %/° C.
​
The power loss can be written as:

Power loss (%) = (cell temperature – 25° C) x temperature coefficient of power

The temperature coefficient of power of Longi solar panels is -0.35%/° C.

For example, the power loss in a 400-watts Longi solar panel can be calculated as:

Assuming cell temperature as 45° C.

The Power loss (%) = (45° C – 25° C) x -0.35%/° C
= 20° C x -0.35%/° C
= – 7%

The 400 watts Longi solar panel will lose 7% of its Pmax (400 watts)

Absolute value (watts) = 7% of Pmax
= 7% of 400 watts
= 28 watts

Also,

​The operating temperature range of its solar cells is -40° C to +85° C.

Warranty of Longi solar panels

When you purchase the solar panel, the manufacturer assures you of two things:

Product warranty

It protects your solar panel from any manufacturing defect, premature wear and tear, and other environmental issues that arise within the period specified by the manufacturer.

The Longi offers 10 years Product warranty on its solar panels.

Performance warranty

The panel manufacturer assures that the solar panel will produce a certain percentage of its Pmax after 25 or 30 years.

The Longi offers 25 years performance warranty on its mono-facial solar panels degrading <2% in the first year and then 0.55% till the 25th year.

And
​
30 years Performance warranty on its bi-facial series, degrading < 2% in the first year and then 0.45% till the 30th year.

Certifications

The certifications are various testing procedures (under standard set conditions) for solar panels that ensure that modules comply with international safety and performance.

Longi solar panels are strong enough to withstand the hailstone impact up to 35 mm in diameter. They are IEC 61215 certified.

Longi solar panels are IEC 61215 certified, suitable to operate in open-air conditions.

​They are certified in quality management systems (ISO 9001:2015) and environment management systems (ISO 14001:2015).

Profitability with Longi solar panels

The return offered by any solar power system depends on various factors such as Sunlight, degradation in solar panels (LID losses and losses due to time), shading loss, transfer loss, conversion loss, temperature loss, power tolerance, and more.

When we consider all these losses, the units produced by 5 kW solar power systems in India with Longi solar panels are 19-20 units per day.

India: When I consider the average grid price in India is Rs. 6 and escalation

USA: Average grid rate 12.51 cents and escalation 2.59%.

“Solar Feasibility Spreadsheet designs the complete solar power system and finds its financial feasibility in minutes”

Pros of Longi solar panels

Affordable

The price of Longi solar panels is below the average price of the solar panels in the market.

Brand

Longi is an over 20 years old reputed brand with healthy financials. Buying Longi solar panels will give you peace of mind for decades.

Efficient solar panels

They offer panels that are efficient with the highest efficiency of 21.5% of its LR5-72 HPH series (Mono-facial).

High snow load rating

The Longi panels are very strong and can be used in extreme weather conditions with heavy snowfall.

Latest technology

Longi is using the latest technology that reduces power losses (such as LID losses, shading losses, heat losses, and other losses in the system) and improves solar panel efficiency. 

Cons of Longi solar panels

• The temperature coefficient of power of Longi solar panels is -0.35%/°C. Although this power loss with temperature rise is less than the industry average, we see other manufacturers making solar panels with a temperature coefficient of power as low as -0.258%/°C (by Panasonic).
• It offers 10 years product warranty on its solar panels. We see REC offering 20 years product warranty on its solar panels. And when you go solar with its certified installer, this warranty extends to 25 years.
• Solar Panel degradation: Although Longi keeps the LID losses below 2%, the degradation in the 2nd year to 25th is 0.55% per year, making it produce at least 85.9% in the 25th year.

When we see other solar panels are degrading just -0.25%/°C and producing over 92% in the 25th year, the performance of Longi solar panels seems a bit less.

“Online Solar Course: “An interactive online course that teaches the sizing, designing, and finds the financial feasibility of the solar power system”

Conclusion

• Over 20 years old branded company with a long history of customer service.
• Suitable for people looking for affordable solar energy solutions.
• Its highly efficient mono-facial and bi-facial panels can meet your energy needs in a limited space.
• Longi solar panels are suitable for people living in extreme weather conditions with heavy snowfall.