Advances in solar power technology are developing at an astounding rate as the race heats up amongst solar panel manufacturers to keep ahead with efficiency improvements.
The latest catch-phrase in the industry is Super Black Solar Panels.
What are Super Black Solar Panels though and what makes them so revolutionary to the industry?
Black silicone cells have been in the news for some years and have been studied since the 1980s. Yet, it’s only recently that they have been commercially produced.
A major challenge in solar power technology has been the reflection of light, as light reflected from solar panels means wasted energy.
Now the reflectivity of a polished silicon wafer surface is approximately 40%.
The solar panel industry has been using anti-reflective coating for years, thus reducing the average reflectivity to approximately 6% and giving solar cells their distinctive dark blue colour appearance.
What Are Super Black Silicon Solar Panels Though?
Super black silicon cells have turned the industry on its head by making strides in efficiency improvements, the holy grail of the industry.
What makes super black solar cells so special is their ability to absorb up to 99.7% of sunlight. That means only 0.3% of incident light is reflected from the solar cells surface, thus beating the typical anti-reflective coating in traditional solar panel technology.
Black silicone uses sophisticated nanotechnology in the production process.
Nanotechnology has been gaining momentum in recent years. Nanotechnology is science, engineering and technology developed at the nanoscale, which is about 1 to 100 nanometers. Its application is being used to redesign just about everything we know from medicine to car parts and now solar panels.
Nanotechnology has opened up the realm to a whole new level on how we design things.
Effectively designing from the atom layer up it allows us to be a whole lot more efficient in the design of new technology.
As everything is done on the nanoscale, the geometry of the nanotexture can vary. Small changes on the nanoscale have a large impact on the macroscale. Thus, different solar panel manufacturing companies manufacturing new generation panels are using different approaches to their nano designs.
As an example, the density, taper and length of the nanowires impact the optical reflection and absorption of the module.
As the different layers of the solar cell are so minute, the light wavelength sees the cell as a single structure. Hence, the reflection is small. Efficiency boosts of 0.4% are being reported by using the nanotechnology approach to develop super black silicone cells.
For a new type of process, this efficiency figure is a major leap forward, but further optimisation is expected as the technology matures.
If one had to take a look at a super black silicon cell, it has a deep, dark matt black appearance.
Recall darkness is the absence of light and the deep black colour merely illustrates its ability to absorb most, if not all light.
It has taken a long time to develop the technology as the industry has had to overcome a number of technical challenges.
One of the major challenges was keeping the nano structure intact during the silicon doping process.
Doping is an extremely important part of the manufacturing of silicon cells. It involves the adding of impurities to intrinsic semiconductors to alter their properties at high heat.
What Are The Advantages Of A Super Black Solar Panel?
Well for starters, a ten-fold reduction in reflection means 3% more usable light would get into the cell, increasing the cell efficiency by that amount.
A solar panel made from super black silicon cells would produce more energy than standard silicon solar panels because it reflects less light.
Secondly, it performs better when the sun is at low angles, especially during the morning and afternoon.
This makes super black solar panels ideal for Northern European countries where the sun is at a low angle for half the year.
So “Black Is The New Black” Then?
A US company, Natcore holds the license for the black silicon development process.
However, their main interest lies in the anti-reflective properties of black silicon. A number of tier 1 suppliers are investing in the transition to black silicon solar panels.
One such company is Canadian Solar, having been the first company to turn all of its multi-cell capacity to black silicon - that’s more than 4GW! They have managed to achieve an efficiency ratio of 19% in commercial production.
Canadian Solar’s range of black silicon solar panels range in size from 290 Watts to 300 Watts. The panels also feature 5 busbars instead of the usual 2 and produce 9% more power than conventional modules.
The module efficiency ranges from 17.72% to 18.33% depending on the panel selected. The module frame is also completely black, complementing the black look of the silicon cells.
They have also included PERC technology into the design of the solar panel. PERC stands for Passivated Emitter and Rear Cell. PERC allows solar panel manufacturers to achieve higher panel efficiencies than they could with standard solar cells.
GCL is yet another tier 1 solar panel manufacturing company that is investing in the black silicon movement.
The company recently stated that they’ve achieved a panel efficiency of 20.78% using the technology.
LG Energy has taken the black silicon movement head-on with the Neon 2 Black module. The Neon 2 Black is one of LG Energy’s best-selling modules and for some obvious reasons, as it includes cutting edge technologies to maximise the panel’s efficiency.
The Neon 2 Black module has a maximum power output of 320W and an efficiency of 18.7%.
LG Energy uses its patented cello technology replacing the conventional 3 busbar approach with 12 thin wires to transfer the electricity generated by the solar cells.
This technology enhances the power output of the panel and improves reliability. More wires reduce electrical resistance, thereby improving the efficiency of the panel by maximising the power output.
Thinner wires also mean less shading on the panels and due to their unique design they reflect the light back into the panel, further increasing the efficiency of the module.
The LG Neon 2 Black panel also generates 2.7% more energy than P-type multi-modules in high-temperature conditions, as well as at low irradiation conditions.
LG Energy is so confident in this module that they guarantee a power output of 86% after 25 years of operation.
Trina Solar has embraced black silicon technology across four different solar module ranges.
The Tallmax M Plus range has a maximum efficiency of 18.9% and module sizes range from 275W to 310W. These modules also have a black backsheet but models are available with the standard white backsheet.
The Tallmax M Plus DD05A.08 (II) range has a maximum efficiency of 19.2% with power output sizes from 280W to 315W.
Sun Power, a US-based Solar PV manufacturing company uses black silicon technology in their X-series range of solar panels.
The black silicon X-Series module has a maximum power output of 335W and with an efficiency of 21%! These modules are also built on Sun Power’s licensed Maxeon technology, with the solar cells built on top of a solid copper foundation. This gives the panel extra durability by limiting corrosion and cracking.
Why Super Black Solar Panels Aren’t Ideal For Australia
Yes, not everything is as ideal about super black solar panels as it may seem.
You might be surprised, but solar panels don’t enjoy getting hot. Like, really hot. In fact, heat can reduce output efficiency by 10-25%.
The best way to determine a solar panel’s tolerance to heat is by looking at the manufacturer’s data sheet.
The Temperature Coefficient (Pmax.) will tell you how much power the panel will lose when the temperature rises by 1°C above 25°C.
For example, the temperature coefficient of a solar panel is -.258% per 1 degree Celsius. This means that for every degree above 25°C, the maximum power of given PV panel falls by .258%, for every degree below, it increases by .258%.
In Australia, temperatures higher than 25 degrees C are common. That’s why black panels have better alternatives here - Mono or Polycrystalline modules, which have the highest efficiency (At 1:1 concentration), but also the highest temperature coefficient at Pmax.
You may want to consider a thin film or CdTe module – or in the case of a very large project, High Concentration PV, which is designed for hot climates, but not applicable for small projects.
Here are other ways to minimize the negative effects of high temperatures:
• Install panels a few inches above the roof to allow air flow to cool the panels down.
• Ensure that panels are constructed with light-coloured materials, to reduce heat absorption.
• Move components like inverters and combiners into the shaded area behind the array.
Super black silicon technology has been the talk of the industry since the 1980s. But it’s only in recent years with the advent of nanotechnology that it has made the leap from the lab into the solar module factory.
A major advantage of black silicon panels over conventional solar panels is the ability of the technology to absorb 99.7% of sunlight, thereby increasing the efficiency of the solar module.
Nanotechnology deals with the design of products at the nanoscale. Small changes to how compounds and structures are designed at such a minute scale impact the final product at the macroscale.
Another advantage of black silicon panels is their ability to maximise electricity generation in low light conditions or with low sun angles. This makes the technology an ideal candidate for countries in the Northern Europe where sunlight is at low angles for much of the year.
But, as heat negatively impacts solar panel efficiency, super black solar panels are not ideal for the Australian climate. Better alternatives are mono or polycrystalline modules.
Increasingly, more tier 1 solar panel manufacturers are showing interest in black silicon technology.. Such household names as LG Energy, Trina Solar, GCL and Sun Power to name just a few, are now incorporating this technology into the design of their solar modules.
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Photo credit: Trina Solar