2023-07-01 05:19:24
Illustration : Getty, montage : RE.
We are witnessing a real race for power. Manufacturers of photovoltaic panels, especially Chinese, compete in techniques to offer their customers ever larger and more powerful panels.
The website Clean Energy Reviews has just published its ranking of the most powerful photovoltaic panels on the market:
Among these first 5, four of them have a nominal power greater than or equal to 700 W. The most powerful, Akcome’s iPower7 even reaches 730 W – and we will see later, under certain conditions, these panels can be even more powerful. But beyond the data, this ranking is of great interest in revealing trends in the photovoltaic industry.
Continuously improving performance
The first trend is the presence in this Top 5 of N-type cells only, and this is mainly explained by the higher efficiency of this semiconductor technology. Recall that the type refers to the element used to dope the thickest layer of the photovoltaic cell, the N type opposing the P type. P type cells have long dominated the market, under the initial impetus in particular space applications which appreciated its good resistance to the aggressive environment of space. However, the good performance of N-type cells has led to a certain craze more recently.
However, as we see in the table, the yield of the panels is a characteristic directly associated with its ranking in order of power: the model at the top of the table has a yield of 23.5%, then the yields decrease to 22, 2%, which is still an excellent performance.
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Other features support this high efficiency: HJT technology (Heterojunction Technology) in particular, which occupies the first three places, as well as TOPCon technology. Heterojunction is a technique that was neglected for many years, but which is now showing its full potential: it consists of placing two layers of amorphous silicon around a central layer of monocrystalline silicon. This arrangement has the advantage of maximizing the wavelength range of the sunlight captured and transformed into electricity.
The second technique, called TOPCon, for Tunnel Oxide Passivated Contact, also aims to maximize yield. To do this, it provides in particular for placing a very thin layer, less than one micron, of an oxide on the rear face of the solar cell, so as to minimize surface recombinations of the lower semiconductor layer and boost the efficiency. .
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Bigger solar panels
The importance of performance on the power classification of the panels is all in all logical since the five panels mentioned all have the same surface. These are large panels: 2.4 meters high by 1.3 m wide. The race for the greatest power of photovoltaic panels is therefore also a race for the greatest size.
The main motivation for this trend lies in the objective of reducing installation costs for large solar power plants. Indeed, more powerful panels require an equivalent amount of connections and labor than smaller panels, and the installation cost per kilowatt of installed power is therefore lower. The market targeted by these large panels is therefore mainly that of commercial energy producers, who deploy large power plants, rather than individuals wishing to equip their homes.
Note that during the 14th International Photovoltaic Power Generation and Smart Energy Conference & Exhibition (SNEC 2020), JA Solar presented an 800 W panel, of considerable size (2.2 m high and 1.75 m wide) and which will probably not be marketed.
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Better use of panel surface
Another factor that explains the increase in power of the panels is the greater density of solar cells within the surface. Thus, for example, Trina Solar and LONGi Solar have succeeded in reducing the vertical gap between the cells, from 2 to 0.5 mm for Trina Solar by a narrower bus technique, and from 2 to 0.6 mm for LONGi by a method known as “intelligent welding”. The proportion of active surface within the panels is therefore increased, leading to higher power for the same panel size.
Finally, the first four panels of the Top 5 are bifacial, that is to say that they are able to produce electricity by their front face, but also by their rear face. This capacity is more or less usable depending on the assembly of the panel (structure, height, angle with respect to the sun), as well as according to the albedo of the ground. This possibility of increasing the energy produced is not accounted for in the standard nominal power, but can be found in the manufacturer’s documentation. For example, regarding the iPower7, Akcome indicates that when the gain of illumination on the rear face reaches 25% compared to a reference of 690 W on the front face, the power of the panel can reach 860 W.
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A technological competition
As we see, photovoltaic panel manufacturers are in a race for power. But this race is above all a technological race, which goes through many technical changes: type of semiconductor, size of the panels, race for efficiency, size of HJT or TopCon technologies, progress in cell wiring… How far will we take? this race, no one knows, but what we do know for sure is that it has some great technological surprises in store for us.
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