We are all used to the rigid glass and aluminum frame solar panels that adorn home roofs or sit under the sun on massive on-ground installations. They have been the typical definition of a solar panel and they serve the purpose pretty well.
However, there are times when something lighter or less overt is needed and you don’t want to run a generator. This is where the flexible solar panels (or shingle-like panels) come in.
Today we are going to look at flexible solar panels and find out how they compare against the rigid tested and proven panel.
What are They?
The main difference between flexible panels and the traditional panel is that they can flex and bend. They get their flexibility from the ultra-thin silicon wafers used to make their cells.
The wafers can be as thin as a micrometer meaning that the entire panel structure can flex more than traditional panels that use cells thicker than a human hair.
Manufacturers then pair up these ultra-thin wafers with a flexible protective resin creating that light and flexible solar panels campers, RV dwellers and boat owners might find appealing.
Their biggest advantage is their light weight and flexibility. They can perfectly fit on curved surfaces and won’t interfere with aerodynamics. But that’s just about it. They are inferior to rigid panels in every way – at least for now. Their shortcomings outweigh their benefits.
Types of Flexible Solar Panels
Different technologies can be used to achieve the flexibility on the solar panel. Currently, we have three commercially available types of flexible panel:
Crystalline Flexible Solar Panels
Silicon crystalline panels are very similar to the traditional panel only that the silicone crystals making its cells are very thin (a few micrometers compared to the around 200 micrometers in a rigid panel). Since the technology needed to make them is very similar to what rigid panel industry uses, they are more common and affordable compared to the other two types.
The panels are very light since they don’t have an aluminum frame or the thick protective acrylic or glass layer rigid panels have. They will pair well with an equally light Lithium battery bank.
Flexible panels use a flexible plastic or resin to protect the silicon cells. Since they are built with lightness and portability in mind, you often find them in small sizes that are below 300 watts with the most popular being the 100 Watt offering.
Tests have shown the very best bending up to 30 degrees around the center. While this might not sound very impressive, it is enough to let you mount them flash on curved surfaces like caravan, van, boat and RV roofs.
This is why they are fondly referred to as caravan solar panels.
Thin Film Flexible Panels
This is a newer technology that prints the photovoltaic material on a very thin surface. It is still in development but it can generate ultra-light and flexible panels than can roll up like a sheet of paper or cloth.
You won’t find them on your favorite online or offline store yet as the technology is still working on making the panels as durable as they are flexible.
Organic Cell Flexible Panels
MIT is working on strong and flexible panels that are mostly made of organic material. The technology uses graphene for electrodes and if perfected could be another eco-friendly source of flexible solar panels.
Are Flexible Solar Panels Better Than Rigid Panels?
Going with a flexible solar panel is a matter of preference. The biggest wins they bring to the table is their lightweight and flexibility.
When they Might be a Good Idea
Flexible solar panels might be a good idea if you really need their flexibility and low weight and don’t mind about their other shortcomings.
Flexible Makes them Easy to Mount on Curved Surfaces
Since they are flexible, you can plaster them onto your boat or RV roof without adding installation rails or messing up with your ventilation and air conditioning vents. Sometimes, you can get away with using strong Gorilla Tape or some tension cables looped into the car to secure the panels.
They fit snugly and mold around the installed surface’s curvature making them more discrete and in some people’s opinion beautiful.
Check this too: How Many Solar Panels Do I Need for My RV?
They are Light and Portable
If weight is a concern to you, flexible panels might be a good option. If you think your camper can’t take the extra weight of panels on the roof, flexible panels will give you more wiggle room.
They are also light enough for backpackers or campers who are looking for a portable panel they can deploy fast and pack up easily once it is time to move on.
Why Do Flexible Solar Panels Fail?
Even though they might have their application, I strongly believe that they have no place in permanent van, RV, boat or even home installations. Here are the top reasons why I strongly advise people to avoid flexible panels.
They are Terrible in Dealing With Heat Build Up
Heat is the greatest enemy to solar cell performance. Rigid frame panels have multiple treatments to cope with heat. For instance, the thicker cells are more heat tolerant. Moreover, solid panels will always have some space between the cells and mounting surface creating that crucial cooling airflow.
Most flexible panels are mounted flat against a surface. This makes them terrible at dealing with heat unless they are installed on a conductive cooled surface. Moreover, their material and thin wafers are terrible at dealing with this heat buildup.
The extra heat makes them less efficient. It also lowers the panel’s lifespan. A typical rigid panel can last up to 25 years while consumers are reporting less than five years on flexible panels.
You will be a bit okay if you live in a cool area where heat is not a problem and have a good MPPT charge controller like a Victron or a Renogy.
They Might Not Be as Flexible As You Think
While most flexible panels will hit the 30 degree bend around the center, they are terrible at bending over at specific points.
For instance, trying to achieve this 30 degree bend at a point say 5 inches from the edge to conform to a curve on your RVs roof will lead to cracks.
A crack means a damaged solar cell which translates to lower voltages and energy throughput.
A small mistake as pushing your panel flat over a ridge on the roof, or even a tiny hard bump will damage your flexible solar panel.
Since you really can’t tell how much you can flex them and at what point they flex, installation can be a nightmare and you can easily damage the panel long before you start using it.
ProTip: Avoid cheap PET and PTE flexible panels and go for the more versatile and flexible ETFE based builds
Flexible Solar Panel Manufacturers Come and Go FAST
Most of the cheap flexible panels are from Chinese manufacturers. The problem with most of these companies is they rarely stand behind their product.
Chances are your flexible panel manufacturer will have closed shop within a year and you will not have anyone to turn to if you run into problems along the line.
If you decide to buy, stick to well-known businesses like Renogy.
When to Use Flexible Solar Panels
Despite their shortcomings, they still have value to the off grid society. They are a good option to people who want a portable solution or who want a very light panel on their roof (like if you have a movable A frame trailer).
They will also work if you don’t want to drill holes in your car’s roof as you can use other installation procedures that don’t puncture your roof.
However, if you are looking for a permanent installation and are keen on efficiency, always consider getting a good mounting rack and using rigid panels instead.
PS: This advice is based on the current flexible solar panel technology. I will update my opinion once new and better flexible solar panels hit the market.
Can You Cut Flexible Solar Panels?
No. You cannot. All the solar cells in flexible solar panels are connected in either series or parallel. Cutting off a section of the panel will reduce your panel’s output and even void warranty.
Instead of thinking about slicing your panels, go for two smaller panels and connect them the right way. They should fit into the small space you want and they will still be useable and safe.
How Long Does a Flexible solar Panel Last?
Some manufacturers give a 25-year warranty on their flexible solar panels. However, a quick interview with some owners and laps on forums show that these panels rarely last over 5 years. Other manufacturers are realistic and give a one year warranty.
The shorter lifespan is due to the shortcomings discussed in the section on why flexible solar panels fail.
Can You Stand on Flexible Solar Panels?
Though flexible, flexible solar panels are not as versatile as you think. Stepping on them or even applying slight weight will introduce hairline fractures that deteriorate the panel faster.
Rigid panels are stronger and more resistant to impact and it’s not advisable not to step on them. Stepping on your flexible panel will definitely damage them.
How Do You Mount a Flexible Solar Panel?
You can use a couple of mounting procedures depending on the mounting surface. Since the panel is so light and thin, you rarely need a lot of structural support to keep it in place.
Using Gorilla Tape
Gorilla tape, or any other strong tape, can be used to adhere the panels to your roof. Think of it as taping a big poster onto your roof and you are good to go.
Ensure that there are no bumps under the panels as this could crack it. This non-intrusive approach is good if you don’t want to puncture the roof and are willing to inspect and maintain your installation often.
A more temporary installation can use Velcro straps to hold the panel in place when in use. Stick Velcro to the back of the panel and on the mounting surface and bond them when installing.
This approach gives a weak bond and it is not advisable to drive with the panels on the roof as they might fall off. However, since the panels are easy to pull down and put up, you can use it if you want a super-flexible part-time installation or want to make panel cleaning and maintenance easier.
Screws will give you the tightest possible fit for a more permanent installation. You will have to drill small holes through the installation surface at the four corners of the panel but that is it.
Some people use caulk or silicon around the panel for extra protection but this is not necessary if you screw down the edges well.
Using Cables or String
If you have a roof rack or can wrap some ropes around the mounting surface to existing anchor points to the side of the vehicle, boat or house, you can use some thin strong rope to secure your flexible panels.
If you want to use this approach, go for panels with eyelets along the edges. This is where you will run your cord through and lash down the panel.
This installation leaves some wiggle room and your panels might flap around especially if you didn’t have enough lashing points.
Flexible solar panels are a novel idea that is yet to deal with some teething problems. The panels are in many ways inferior to rigid panels but still have their place in the off grid world.
Only use them if your installation surface can’t take the weight of a rigid panel or are looking for a temporary portable installation where longevity isn’t a problem.