1. Flexible solar panels are another category of foldable devices receiving lots of scientific attention. And while many advances are being made, researchers have been having a challenging time making the panels fully foldable (repeatedly bend without breaking) until now.
2. Engineers at Korea’s Pusan National University created fully foldable prototype solar cells. Such panels would simplify storage and transportation and integration into everyday devices like cars, windows, phones, and clothing.
3. While flexible solar cells do exist, their bend is limited, like a card; If they bend any further, they break. A genuinely efficient foldable conductor can withstand the pressure of turning within a tiny radius while maintaining its integrity and function. That’s what the Korean engineers found.
4. Unlike merely flexible electronics, foldable devices are subject to much harsher deformations, with folding radii as small as 0.5 mm. This is not possible with conventional ultra-thin glass substrates and metal oxide transparent conductors, which can be made flexible but never fully foldable.
5. The team used conductive films made of single-walled carbon nanotubes (SWNTs). They are thin, transparent, mechanically resilient, and flexible – all the properties required for an efficient foldable conductor.
6. The engineers embedded this film into a polyimide (PI) substrate, filling the nanotubes’ void spaces so it could adhere to the base without chemicals. Then, they doped it with molybdenum oxide to increase its conductivity. The molybdenum oxide reduces the energy needed for electrons to move across the structure so that the cells can generate more charge from the current.
7. Their composite film resulted in a nearly 80% transparent solar cell only 7 µm thick, with a folding radius of 0.5 mm and power conversion efficiency of 15.2%, the most ever achieved in solar cells made with carbon nanotube conductors
8. The prototype was able to withstand over 10,000 folding cycles without breaking.
EXISTING FLEXIBLE SOLAR PANELS - EFFICIENCY
1. Compared to rigid panels, flexible solar panels simply aren’t as efficient. While rigid crystalline panels have efficiencies between 16% and 23%, average efficiencies for flexible solar panels fall between 10% and 17%.
2. This is partially because the thin semiconductor film in flexible panels has less material to react with the sunlight. It’s also that the semiconductor material used in flexible panels is less efficient overall when compared to the crystalline silicon in rigid panels.
3. The best solution is to buy the highest quality panels. The best flexible panels far outperform the lowest grade of rigid panels, so your better off paying more for high quality, especially if the flexibility is a necessity. Another solution, if you have the space, is to simply add more panels to make up for the lack of efficiency.
4. Since flexible panels weigh less, you won’t be putting as much stress on your roof compared to an array of rigid panels. If you don’t need the panels right now, you can also wait a few years.
EXISTING FLEXIBLE SOLAR PANELS - DURABILITY
1. Flexible panels can take being bent and flexed, which is part of their appeal. But too much bending and flexing can actually cause the solar cells to crack. If you have flexible solar panels on the roof of your house, truck, or RV, the plastic can get scratched by branches and trees, which can possibly damage the solar cells as well.
2. One bad hit is all it takes to crack a solar cell, and cracked cells lower efficiency. Rigid panels have a glass covering, which offers more protection from the elements.
3. If installed on a vehicle, drive carefully in places where there are low-hanging branches. Do not walk or stand on the panels either. Since they are flat, they can easily blend in on your roof, so make sure to watch your step.
EXISTING FLEXIBLE SOLAR PANELS - SHELF LIFE
1. The shelf life on flexible panels isn’t as long as their rigid counterparts. Where rigid panels can last anywhere from 25 to 40 years, flexible panels might be functional for just 15 to 25 years.
2. They don’t have a very high efficiency to begin with, so when their power output starts to drop, they aren’t going to be useful for much longer. This also has to do with durability. Since flexible solar panels are often used in recreational settings, they’re more likely to get damaged, which lowers the shelf life.
3. Any microcracks in the plastic will allow dirt and dust to get inside, ruining the panel and lowering the shelf life. Cracks in the solar cells will cause lower power output, which will also weigh down on your shelf life. Another thing you can do is buy high-quality panels. High-end flexible panels will last as long as some rigid panels.
EXISTING FLEXIBLE SOLAR PANELS - MATERIALS
1. Some panels are made with toxic materials. Specifically, CdTe and CIGS panels, both of which can be manufactured as flexible panels. CdTe contains cadmium, which is highly toxic and carcinogenic. While the workers who manufacture CdTe panels face the most risk, the customer may be at risk as well.
2. Breaking the panel and being exposed to the semiconductor material can potentially cause adverse health effects. This also applies to CIGS solar cells, but they are much less toxic.
3. Similarly, the panels are bad for the environment. If they’re improperly disposed of, the toxic chemicals can leech into the soil and water supply.
4. Rigid panels and some flexible panels use silicon for the semiconductor material, which is inert and poses little threat to people, wildlife, or the environment. Still, all solar panels are treated as hazardous waste when disposed of.
5. Cadmium telluride (CdTe) and copper indium gallium selenium (CIGS) are some of the more efficient types of flexible panels, so some may opt to buy these types over flexible silicon panels.
EXISTING FLEXIBLE SOLAR PANELS - UV DEGRADATION & DELAMINATION
1. Solar panels spend all day in the hot sun. But after a while, the powerful UV rays cause some chemical changes in the panels. If you have low-quality or cheap solar panels, they will undergo UV degradation.
2. This is true for both flexible and rigid panels, though it’s much more common in flexible panels. You will notice when the UV rays have done damage when the plastic laminate begins to turn yellow and cloudy.
3. This discoloration blocks the sunlight and lowers efficiency. If it gets really bad, your panel will undergo what’s called delamination, where the plastic laminate becomes detached from the solar cell. Panels that show delamination are ruined and should be disposed of.
4. Buy high quality panels! UV degradation and delamination are commonly seen in panels that are made with a kind of plastic called PET.
5. High quality panels are manufactured with a more durable plastic called EFTE, which is resistant to UV damage and delamination. EFTE is also self-cleaning and 100% recyclable.
EXISTING FLEXIBLE SOLAR PANELS - CHEMICAL DEGRADATION
1. For those who live near the ocean or have flexible panels on their boat, chemical degradation from the ocean can be a problem.
2. The constant barrage of salty air and ocean spray eventually corrodes and builds up on the plastic, lowering efficiency and damaging the solar cells. If your solar panels are constantly wet, the water can magnify the sun’s UV rays and accelerate degradation.
3. PET is the culprit here. PET panels are not well-equipped to handle the tough conditions on the ocean or near the coast. EFTE panels can withstand the salty air and marine environment. And like we said before, EFTE panels don’t suffer the discoloration and cloudiness that affect PET panels.
https://www.intelligentliving.co/amp/breakthrough-solar-panel-technology-fully-foldable-cells
https://www.semprius.com/flexible-solar-panel-problems/
