Longi Solar Panels Review

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LONGi Solar Panels Overview

LONGi Solar is the world’s largest manufacturer of solar products, including wafers, cells and panels and was partly responsible for driving the solar industry towards more efficient monocrystalline PERC cells. The company produces a wide range of cost-effective solar panels for residential and commercial applications and, over the last three years, has emerged as one of the industry leaders in PV research and development. Stand-out achievements include innovations in high-efficiency HJT silicon cells, and more recently, Longi released the first panels made using their unique HPBC cells, making the Longi Hi-MO 6 panels some of the most efficient solar panels in the world!

LONGi Solar Panels Quick Summary

• Power ratings (Watts): 350W - 600W

• Panel Efficiency %: Very High - 20.5% - 23.0%

• Cell technology: P-type HPBC and N-type TOPCon

• Price bracket: Low-med $$$

• Most popular panel: Hi-MO 5m 415W

• Product Warranty: Standard - 15 years

• Service and support: Good 3.5/5

• Overall: Recommended ☆☆☆☆

Company History

LONGi Solar was established in 2000 and is wholly owned by the Longi Group based in Xi’an, China, with manufacturing facilities in Malaysia, Vietnam, India, and throughout China. LONGi has grown rapidly over the last five years to be crowned the world’s largest solar company based on sales revenue and market capital in 2020 with an incredible annual production capacity of over 110GW, including 25+ GW for panels, 30 GW for cells and over 55 GW for wafers.

LONGi Solar only produces monocrystalline products, and the company was largely responsible for driving the solar industry back towards more efficient monocrystalline cells after polycrystalline cell technology previously dominated the market since 2012 due to lower production costs. To achieve this transition, Longi Solar started building new facilities and significantly ramping up the production of monocrystalline wafers to supply much of the solar industry with lower-cost mono-Si wafers and cells.

LONGi solar cell Efficiency records

Along with the enormous manufacturing capacity, LONGi Solar has a huge research and development team and has held a number of cell efficiency records over the years. Building on this, the last few months have seen LONGi’s R&D team achieve an impressive new efficiency record based on the popular heterojunction (HJT) cell technology with a record-breaking 26.81% cell efficiency. This is the world's highest silicon solar cell efficiency record to date.

New HPBC Cell Technology

The new high-efficiency HPBC cell design by LONGi

In November 2022, LONGi announced the Hi-MO 6 series of panels made using the new high-efficiency Hybrid Passivated Back Contact (HPBC) cell technology to achieve an impressive panel efficiency of 22.8% in mass production. Traditionally, panels could only reach efficiency levels above 22% using the more common N-type TOPCon or IBC cells. However, LONGi managed to match the level of Sunpower, which produces the most efficient solar panels on the market today, using a new P-type Hybrid Passivated Back Contact (HPBC) cell design, which is similar to the well-known IBC cell design, the first solar company in the world to do so.

Other premium solar manufacturers, such as Sunpower and REC, have used cells based on the more efficient N-type wafers for many years, but now LONGi, along with several other Chinese producers such as Jinko Solar, are developing and refining new efficient cell structures and are set to significantly ramp up production of these more efficient cells to drive down costs.

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LONGi Solar Panel range

LONGi produces a wide variety of quality, cost-effective solar panels for residential, commercial and utility-scale solar installations. The current models are the Hi-MO 4 and Hi-MO 5 series, with the new advanced Hi-MO 6 panels due to be released in early 2023.

• Hi-MO 5m - 54 (108) cells - for residential systems

• Hi-MO 5 - 72 (144) cells - for commercial systems

• Hi-MO 6m - 54 (108) cells - for residential systems

• Hi-MO 6 - 60, 66, 72 cells - for commercial systems

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Hi-MO 5 Series Panels

LONGi’s Hi-MO 5m panels are designed for residential rooftop solar systems while the larger format Hi-MO 5 panels are for commercial and utility-scale installations. Like the previous Hi-MO 4 range, these panels are built on the latest monocrystalline PERC cells featuring multi-busbar (MBB) half-cut cells. The Hi-MO 5 range, uses gallium-doped silicon, which reduces the effect of light-induced degradation from 0.6% per year to around 0.45% per year, resulting in only 11% to 12% loss in power after 25 years, plus the initial 2% in the first year.

Hi-MO 5 panel specifications

• Monocrystalline PERC gallium-doped silicon cells

• 400W to 550W Power rating

• 21.3% maximum panel efficiency

• Half-cut cell format with 9 busbars and smart soldering

• Larger 182mm M10 wafer

• 12-year product warranty

• 30-year performance warranty

• 84.9% remaining power after 30-years

See the detailed LONGi Hi-MO 5 datasheet

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Hi-MO 6 series panels

The impressive new Hi-MO 6 series from Longi solar are the first panels ever to feature a Hybrid Passivated Back Contact (HPBC) cell design. Surprisingly, this unique new cell design is based on a traditional P-type cell substrate, unlike the more common N-type cells now being used by most manufacturers to increase efficiency. The HPBC cell architecture incorporates back-side contacts, meaning there are no busbars on the front side, which improves efficiency. It also uses rear-side passivation combined with back-contact soldering technology and employs a new one-line soldering method to improve the cells resistance to cracking and increases durability. More notably, this revolutionary design makes the Hi-MO 6 series some of the most efficient solar panels available.

The new LONGi Hi-MO 6 panels avialable in 4 distinct series for different applications

The Hi-MO 6 includes four distinct series designed for different applications. All of which use M10 size (182mm) HPBC cells and are available in 72C, 66C, 60C, and 54C types.

1. Explorer Series - Classic design using HPBC cells

2. Scientists Series - Maximum efficiency HPBC cells with low degradation

3. Guardian Series - Contains integrated smart panel-level optimisers

4. Artist Series - Available in a variety of unique colours

The unique new colourful Hi-MO 6 Artist series panels - Image credit Longi Solar

Hi-MO 6 panel specifications

• Monocrystalline HPBC cells

• 410W to 600W Power rating

• 23.0% maximum panel efficiency

• Half-cut cell format with HPBC cell technology (MBB)

• Large 182mm M10 wafer

• 15-year product warranty

• 25-year performance warranty

• 88.9% power remaining after 25 years

See the detailed LONGi Hi-MO 6 Scientists datasheet

Click here for all other LONGi Hi-MO series datasheets

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Gallium-doped Silicon

LONGi Solar teamed up with Shin-Etsu Chemical Co in early 2020 to mass-produce a new gallium-doped silicon cell which is claimed to drastically reduce the effects of light-induced degradation (LID) in common P-type PERC silicon.

LID, or light-induced degradation, is a well-known phenomenon that causes a 2-3% loss of power during the first few hundred hours of operation due to trace amounts of oxygen left over during the manufacturing process of common Boron-doped silicon. Over the remaining life of the panel, the losses due to LID drop significantly to around 0.5% to 0.8% per year, depending on the quality and purity of the crystalline silicon.

LONGi Solar’s improved performance warranty with Gallium doped Silicon - Image credit LONGi Solar

The vast majority of solar panel manufacturers use boron-doped P-type silicon wafers, which results in a performance warranty of around 82 to 83% retained power after 25 years of use. With the increased stability of Gallium-doped silicon, LONGi is able to reduce the LID effects over the first year to 2% and less than 0.5% per year for the remaining life of the panel resulting in the panel retaining close to 85% of the original power rating after an increased 30 year period.

Smart soldering Technology

Several manufacturers using the now common multi busbar (MBB) technology have developed ways to reduce the gaps between cells to increase surface area and boost efficiency. LONGi Solar has taken this to another level by developing what it has termed ‘Smart Soldering technology’ which uses a unique triangular shaped micro busbar with flattened ends to both reduce the inter-cell gap and boost efficiency.

The triangular segmented ribbon maximizes the absorption of sunlight on the front side of the cell and achieves a more reliable cell interconnection with a 0.6mm micro gap. Testing has shown Smart Soldering technology can boost efficiency by 0.3% in comparison with conventional MBB technology.

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Summary

LONGi Solar has emerged as the world’s largest solar manufacturer and, more recently, one of the leading developers of innovative solar cell technologies. With a massive production capacity, LONGi is not only driving down costs of more efficient wafers and solar cells but producing a range of cost-effective solar panels for residential and commercial applications. Overall, we recommend LONGi Solar panels as a good reliable choice for those looking for affordable solar panels with advanced cells and improved long-term performance.

The recent record-breaking achievements and new cell technologies, including Gallium-doped silicon, smart soldering, and the impressive HPBC cells, have placed LONGi in the top group of solar technology innovators. This is highlighted by the recently announced Hi-MO 6 series of panels which are due to be officially released in the coming weeks. It will be very interesting to see what other new innovative ideas and processes LONGi develops to improve performance and reliability over the next few years.

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