SOLAR HIGHWAY?: This artist's rendering of the solar roadway concept shows how the panels might replace asphalt on the nation's roads.
Image: © Dan Walden
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A truck tire supporting a 36,300-kilogram load repeatedly traverses an 18-meter stretch of road, day in and day out, rolling up 483,000 kilometers on the odometer at the U.S. Department of Transportation's (DoT) testing facility in Virginia. The goal is to thoroughly challenge any new paving techniques and see how the road surface holds up. Now imagine putting a solar panel under there.
That's exactly what Scott Brusaw of Sagle, Idaho–based Solar Roadways hopes to do next February. The electrical engineer is currently at work building a prototype of his so-called "Solar Road Panel" with the help of a $100,000 small business contract from the DoT.
"We're building solar panels that you can drive on," Brusaw says. "The fact that it's generating power means it pays for itself over time, as opposed to asphalt."
There are about 260,000 kilometers of roadway in the U.S. National Highway System alone, and thousands more in state highways, suburban thoroughfares and rural roads. Could all that asphalt be replaced with a solar technology that would also double as the nation's power grid?
The key to making this work will be the glass: The solar road panel prototype is 1,024 modules—each containing a solar cell, a light-emitting diode and, someday, an ultracapacitor for storage—sandwiched between a layer of some yet-to-be developed glass and a layer of conducting material. "Nobody's tried to drive on glass long-term," Brusaw says.
In addition to needing strength, this glass will be textured to allow tires to grip and water to run off. It will also be embedded with heating elements—like a car's rear windshield—to melt snow or ice. And it will need to be self-cleaning, coping with the grit and grime of an endless procession of tires as well as dust, dirt and other highway detritus. Needless to say, such glass does not exist yet but Brusaw hopes to partner with researchers at The Pennsylvania State University's Materials Research Institute to develop it.
"Glass theoretically can have a very high strength, provided there are no flaws," says materials scientist John Hellmann of Penn State, a glass expert. But "can you keep the proper optical properties to transmit light to the PV [photovoltaics, or solar cell] and still not weather or change with that traffic going over it? … We make some pretty doggone good glass for structural applications but we're not driving trucks on them."
The engineering challenges are immense, adds materials scientist Richard Brow of the Missouri University of Science and Technology, another glass expert. But glass can be strengthened by compressing its surface using special heating techniques or, at a molecular level, swapping ions in the glass itself. Such enhanced glass is 10 times stronger than the conventional variety and is used, for example, in smart phones to withstand the pressures of texting. "Can you go from a teenager's thumb to a truck? That's a pretty big leap, but 10 years ago we didn't think you could make a 15-micron piece of glass for what's relatively rough handling in a PDA," Brow says.
Glass has been used to build footbridges, such as the Chihuly Bridge of Glass in Tacoma, Wash. And new glass ceramic composites with increased toughness have been developed for the photovoltaics industry, Brow adds—but that might boost the price of the resulting panel.
In the meantime, Brusaw is spending $40,000 of the DoT's money to build a prototype from chemically hardened glass panels that can be purchased today. He will experiment with various types of solar cells, from thin-film to traditional monocrystalline silicon photovoltaics, and he will try to strike the right balance between transparency—so the panel works to deliver at least several thousand kilowatt-hours of electricity each day—and road-gripping texture, which will block some of the light. "If you have perfectly clear glass, you get perfect PV efficiency. But [with] perfectly smooth glass, everybody slips off the road," he notes. "Glass manufacturers can cut grooves into the glass in a hatch-type pattern. We'll try various methods and see what holds up."
Cost will be a factor: "The cost to develop a glass that will hold up in the fast lane of a highway? Fifteen [million] to 25 million dollars over three to five years," Brusaw says. "The cost in mass production? About $1 per square foot." The goal is to produce a 12-foot by 12-foot panel for $10,000 that is capable of producing 7,600 watt-hours of electricity daily; it would take roughly six panels to match the electricity demand of one average U.S. home, which use 936 kilowatt-hours per month, according to the Energy Information Administration.*
In addition to requiring a yet-to-be-invented form of glass, solar roadways would need some form of energy-storage capability—whether batteries or some not-yet-devised ultracapacitor. The goal is to create a cross-country highway system that can also serve as an national electricity generator and power grid. And paired with wind turbines to generate electricity at night, Brusaw estimates replacing the nation's highways with his solar roadways could eliminate the need for fossil fuel–fired power plants. "Based on my calculations, at 15 percent efficiency [from the photovoltaics] we produce more than three times the electricity we have ever produced," he says. Even with cars constantly casting shade over the road surface, along with other challenges, "we think we can make enough to meet the nation's energy needs," he adds.
Other companies, such as the England's Invisible Heating Systems, have developed roads that use embedded water pipes to harvest some of the sun's ample energy that also bathes U.S. roads.
The solar roadway will also offer embedded LEDs to illuminate the road and display information, whether the actual traffic directions, such as lane markers, or messages such as "SLOW DOWN." And, should electric cars become popular, powered pavement could also offer recharging stations wherever such panels are installed.
The first test of Brusaw's crystalline vision will be when the prototype is delivered to the DoT on February 12, 2010. And the DoT's challenges will be followed by some durability testing by the inventor with a pickax, sledgehammer and, depending on the prototype's fortitude, guns. Then it's on to parking lots and perhaps fast food restaurants. "Parking lots are much better than going right out onto the highway," Brusaw says. "You have slow-moving, lightweight vehicles. We can learn all the lessons there before moving into the fast lane."
*This sentence was changed to reflect actual power output of the panels, which is in watt-hours not kilowatt-hours as originally written.
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53 Comments
Add CommentI met Scott Brusaw at his home in Idaho and interviewed him as a part of YERT - Your Environmental Road Trip. You can see a shortened version of the interview here:
Reply | Report Abuse | Link to thishttp://www.youtube.com/watch?v=J3PeSm6_hTE
You'll see that he's a level-headed guy with a very interesting idea. He discusses some of the political challenges as well-- perhaps even more challenging than the technical concerns. Easily one of the more compelling and system-changing ideas we encountered in a year of interviews all across America.
I would think that clear plastic would be a better solution than glass in this application.
Reply | Report Abuse | Link to thisI think there is already development work on a house paint that produces solar power. It would be a lot cheaper, easier, faster to paint roads w/ it and connect some cables to draw the power into the local power grids.
Reply | Report Abuse | Link to thisI think a clear plastic would be a better material for roads than glass. glass is innately hard and brittle while plastic can be more flexible to avoid cracking. Plastic could also be poured onto a surface in a process similar to how they pour tar on roads now. I don't think it would take much to retrofit the tools for plastic. They could lay a flexible solar panel material down and then pour the clear plastic over it and then texturize the surface with hash marks for grip and channels to run water off of the road.. The could also add color to the plastic for the lines in the road so it is not just the surface that has paint but is part of the road itself and embed the led lights for night time driving. This is a very cool idea.. MAKE IT WORK!
Reply | Report Abuse | Link to thisI don't think plastic could possibly hold up to this kind of abuse. And, while paint is much cheaper and simpler to use, I think that some of the added benefits of this solar panel road system make it much more attractive, like the LED lane markers and ability to heat and melt ice/snow.
Reply | Report Abuse | Link to thisThere is not enough evidence yet that this could, can or should work. But I love the pure creative outside the box, yet pragmatic thinking involved in this idea. The obvious solutions that this idea could offer in both the developed and undeveloped parts of the world are obvious.
Reply | Report Abuse | Link to thisI am pulling for it. This is the kind of thing worth risking a fair amount of money on. If it can't be made to work cost-effectively, it really is an idea that society can comfortably say "Ah well, it was worth the try."
Fragmented micro photo cells that absorb photons and emit an electromagnetic wavelength that could be used by a wireless receiver. The receiver could even be on the car itself; it could recharge as it drives. You could simply mix the micro photo cells into the top asphalt layer.
Reply | Report Abuse | Link to thisIt is a great idea that could be a great help to the whole nation. But uploading the power to the grid? Does that mean electricity costs would go up or down with this? I would think a slight decline but there could be maintenance cost for the panels. I know I have only one power supply in my area and it would not bold well to have an increase in cost for this.
Reply | Report Abuse | Link to thisFantastic idea. I am sure this will develope into many different and more effective forms than glass and solar panels. Unless they can deveople the glass to mimic our current road condtions, glass could be too dangerous to use. If they can just find someway to make our current roads produce electricity, that would be the first miricle of the 21st century.
Reply | Report Abuse | Link to this'The goal is to produce a 12-foot by 12-foot panel for $10,000 that is capable of producing 7,600 kilowatt-hours of electricity daily, enough per panel for more than 240 average U.S. homes'
Reply | Report Abuse | Link to thisSomething seriously wrong with the figures here. Over most of the US the average solar insolation on a horizontal surface varies from around 2 to 7 kWh per square meter from winter to summer (http://eosweb.larc.nasa.gov/cgi-bin/sse/sse.cgi). 12'x12'=13.4m2. Giving them the benefit of the doubt using the summer figure gives around 54kWh/day falling on the panel. A good comercial PV panel is currently around 15% efficient. This gives a daily output of approx 8kWh. This figure doesn't factor in shading from the proposed textured surface nor indeed from the vehicles themselves as they use the road... I would estimate that you would need at least 5 of these panels to power the average home in summer and close to 20 in winter. A far cry from powering 240 homes from one single panel. The seem to be out by three orders of magnitude...
I am sorry, there was a math error on this article. David Biello, there must have been a conversion error when someone calculated a few figures. The part of the sentence..."The goal is to produce a 12-foot by 12-foot panel for $10,000 that is capable of producing 7,600 kilowatt-hours of electricity daily, enough per panel for more than 240 average U.S. homes" The calculations show that it is supposed to be ~7600Watt hours produced per day, which is 7.6 kWh/day which would power almost 6 hours of home operation. Here are the maths. 12ft*12ft=144ft^2~13m^2 isolation in good areas get a total of 5Kwh/day normal solar cells are about 12% efficient. 13m^2*5kWh/m^2*.12=total of 7.8kWh for a 12 foot square. If you wanted to power 240 homes and the PV was 12ft wide, it would stretch for over 2 miles and cost 6 million at 4$/watt. Other than that. There are some useful this that can come from their research. especially hop those figures were not theirs, or else they would how the geeks say "heading for an epic fail.""" Keep doing what your doing man.
Reply | Report Abuse | Link to thisI am sorry, there was a math error on this article. David Biello, there must have been a conversion error when someone calculated a few figures. The part of the sentence..."The goal is to produce a 12-foot by 12-foot panel for $10,000 that is capable of producing 7,600 kilowatt-hours of electricity daily, enough per panel for more than 240 average U.S. homes" The calculations show that it is supposed to be ~7600Watt hours produced per day, which is 7.6 kWh/day which would power almost 6 hours of home operation. Here are the maths. 12ft*12ft=144ft^2~13m^2 isolation in good areas get a total of 5Kwh/day normal solar cells are about 12% efficient. 13m^2*5kWh/m^2*.12=total of 7.8kWh for a 12 foot square. If you wanted to power 240 homes and the PV was 12ft wide, it would stretch for over 2 miles and cost 6 million at 4$/watt. Other than that. There are some useful this that can come from their research. especially hop those figures were not theirs, or else they would how the geeks say "heading for an epic fail.""" Keep doing what your doing man.
Reply | Report Abuse | Link to thisI am sorry, there was a math error on this article. David Biello, there must have been a conversion error when someone calculated a few figures. The part of the sentence..."The goal is to produce a 12-foot by 12-foot panel for $10,000 that is capable of producing 7,600 kilowatt-hours of electricity daily, enough per panel for more than 240 average U.S. homes" The calculations show that it is supposed to be ~7600Watt hours produced per day, which is 7.6 kWh/day which would power almost 6 hours of home operation. Here are the maths. 12ft*12ft=144ft^2~13m^2 isolation in good areas get a total of 5Kwh/day normal solar cells are about 12% efficient. 13m^2*5kWh/m^2*.12=total of 7.8kWh for a 12 foot square. If you wanted to power 240 homes and the PV was 12ft wide, it would stretch for over 2 miles and cost 6 million at 4$/watt. Other than that. There are some useful this that can come from their research. especially hop those figures were not theirs, or else they would how the geeks say "heading for an epic fail.""" Keep doing what your doing man.
Reply | Report Abuse | Link to thisWOW..... sorry about that, it didn't post and I didn't see the "will show up later" comment about posting, I feel noobish. Again, my apologies, and jimovonz , I must have missed your post, because I was only commenting because I saw no one else correcting the math.
Reply | Report Abuse | Link to thisWe're already having trouble making PV work with enough efficiency by just attaching it to roofs. Simple dusting and aging reduces the efficiency quite a bit. Static panels only aim directly at the sun for seconds per year, the rest of the time it's at an angle, decreasing efficiency again.
Reply | Report Abuse | Link to thisThis *only* a solution if we run out of places to mount solar panels. You know, the entire desert in Utah all glassed over, all houses in my town with panels on their roofs. Then, when you run out of space you start considering such outlandish ideas as making roads out of PV panels. Other PV solutions will always be more practical, more efficient and cheaper.
Sorry, this idea needs a good dose of reality. Just because something seems like a 'good idea' doesn't mean you have to do it. In some cases you can look at the problems the idea is supposed to address and suggest cheaper solutions. Then what's the point?
PV panels are expensive and work best when every last bit of light hits them. Hiding them under glass that's not 100% transmissive right from the get go is not a good idea. Stick 'em on poles or roofs instead.
Rather than PV in the roads, what about using the pressure of all these cars and trucks?
Reply | Report Abuse | Link to thisI've heard about pressure creating small currents when applied to crystals (Quartz, etc), if the crystals were in the road, perhaps we could generate electricty that way...
http://www.blurtit.com/q699945.html
This link says small currents come from the pressure of sound waves, (speaking into a phone) imagine the pressure from a transport truck...
At least our figures more or less agree!
Reply | Report Abuse | Link to thisI bet the road gonna be too hot to drive on!
Reply | Report Abuse | Link to thisThink back to all the early days of nano-technology development and all the scoffing and scaremongering ("grey goo").
Reply | Report Abuse | Link to thisWell, now we're heading for a similar ketchup effect for real functioning renewable technologies. Hold your breath - it won't be long now.
Most interstate roadways have a big grassy median between the directional roadways. Around here they spend a fortune just keeping them mowed. Solution: put the panels between the roads. That gets rid of the tech challenge of building into the road and additionally reduce the cost of maintaining a median. Plus the panels could actually be aimed at the sun - unlike if they were build into a fixed roadway. Oh, and you wouldn't have to reroute traffic to fix 'em.
Reply | Report Abuse | Link to thisJimovonz is right...this is way out of line.
Reply | Report Abuse | Link to thisGood idea, hhill. Or the medians could be partly panelled, partly used for thickets of biomass (useful as headlight dimmers), and partly used in appropriate areas for wind-generators. So much potentially useful real estate going to waste.
Reply | Report Abuse | Link to thisWhat I want to know is, would the solar roadway power system survive an EMP - electromagnetic pulse - attack? An EMP can come from a big solar storm, or an attack by terrorists or a nation like North Korea, and it could be devastating to the US, with our current electric power system. There might be no electric power for months and a large % of the population would starve to death.
Reply | Report Abuse | Link to thisAny replacement for the existing power system should probably be robust under EMP attack.
Cool. Then the pressure of the vehicle riding on the road can create the power to run the vehicle. All you need is to roll it downhill to start and it will run forever!
Reply | Report Abuse | Link to thisHey, my theory is just as legitimate as some person thinking paving the U.S. highway system in solar cells is actually a practical solution to our energy needs.
Or we could just build some nuclear power plants and actually have a workable solution.
Reply | Report Abuse | Link to thisSolar power is currently being implemented as part of the LEED design in developments. Solar highway seems to be a too large of a task at this time. Perhaps considering implementing the solar driveway in large surface parking lots would shed light onto the practicality of the alternate power. Developers could be given incentives, reduce utility bill, easy maintenance, low speed traffic, ets.
Reply | Report Abuse | Link to thisSolar highway seems a bit premature and needs a trial run. One of the trial run could be to lay the solar panels in the driveways of large parking lots. Practicality of cleaning and maintaining the panels, unobstruction of the panels, and designing for slow traffic seems more viable. Solar power is currently utilized as part of the LEED "green" design in property developments. Developers could be given incentives in the form of tax credit, utility savings, etc.
Reply | Report Abuse | Link to thisGood catch jimovonz,
Reply | Report Abuse | Link to thisDavid apparently misunderstood my numbers. It was actually supposed to read 7600 watt-hours OR 7.6 kilowatt-hours. Not 7600 kilowatt-hours.
If an average American home uses 936kWhr/month, then this averages (divided by 30) 31.2 kilowatt-hours per day. 31.2/7.6 = 4.1 Solar Road Panels to take an American home off-grid. We tell people six Solar Road Panels per home just to keep things conservative.
Thanks,
Scott Brusaw
President & CEO
Solar Roadways
This is a great idea. Something which will need much research and development, nonetheless a step in the right direction. The recent developments of solar panels on telephone/ electric poles is also a great idea, along the same lines of using existing grids to create energy. Kudos !
Reply | Report Abuse | Link to thisTransparent carbon nanotube technology would seem to be a more viable substance for this far fetched idea,but future roads built out of this material,could include solar,compression,communication,and perhaps other features not thought of yet, in the designs.Set out modular sections much like some homes are constucted today. With global warming,and other problems facing are society,every little bit helps,maybe it would work.A hundred years ago they said putting a man on the moon was imposible.Who knows?
Reply | Report Abuse | Link to thisCarbon nanotubes would be a better material to work with.A hundred years ago it was said that it was imposible to put a man on the moon.Who knows this might work.
Reply | Report Abuse | Link to thisCarbon nanotube would be a better choice for a material.A hundred years ago it was said that it was imposible to put a man on the moon, who knows this might work.
Reply | Report Abuse | Link to thisCarbon nanotube would be a better choice for a material.A hundred years ago it was said that it was imposible to put a man on the moon, who knows this might work.
Reply | Report Abuse | Link to thisNote that the Chihuly Bridge of Glass is not made of glass - it's made of concrete!
Reply | Report Abuse | Link to thisThis idea has many a tough engineering hurdle to overcome. I don't think it is a good idea at all.
Reply | Report Abuse | Link to thisWhy not focus on panels for rooftops and skyscraper walls? I think building panels into structures (buildings/roads, etc.) has alot of promise but a road takes alot of abuse, are costly to maintain and adding in solar panls just doesn't seem feasible.
I was thinking that it would be less costly to build sloping photo voltalic canopies over the existing roads and linear generators near stop signs and traffic lights (that have their lights turned red), to capture the kinetic energy of the moving vehicles rather than lose it to the braking system in the form of un-usable heat.
Reply | Report Abuse | Link to thisIs it possible to take advantage of solar thermal in this application, instead (or in addition to) photovoltaics? Can we make use of the thermal energy waste of vehicles?
Reply | Report Abuse | Link to thisIt would also be interesting if the same highways can power the vehicles on it. (Popsci transmitting energy wirelessly)
Reply | Report Abuse | Link to thisWhy not leave the roads alone and just put up solar panels everywhere it can be placed? Wouldn't that be more cost effective? And the technology exist now. Imagine repaving 260,000 miles of roadways? Imagine the wastage that will be incurred with rendering the roads obsolete, then add the cost of the new material itself? Not a good idea at all. It's like spending for futuristic sledgehammer when the key is just under the doormat.
Reply | Report Abuse | Link to thisI think powering homes is interesting, but what about powering the VEHICLES that are using that roadway?
Reply | Report Abuse | Link to thisPut it up over the road like an open air tunnel. The road is a solar heat magnet which releases that back into the atmosphere at night, I never hear talk about this fact. So this would correct a slew of conditions such as electrical production reduce heat relection and no more driving in poor weather. plus it can be started NOW! Use the new solar road panels for new road construction when ready.
Reply | Report Abuse | Link to thisI think that over time the UV light will break down the plastic. I am of the opinion however that more effort should be placed on adapting a computer controlled electromagnetic push-pull system for all vehicles (gas or otherwise) for major interstate highways with each lane having it's own dedicated magnetic track with cross overs between fast slow and entering (ramp-up) and exiting (ramp-down) lanes where needed with pre-warning voice prompts for lane changes or changes from the automated magnetic controlled system to exiting to the manual off hwy where the use of gas/diesel/hybrid drive systems would take over.
Reply | Report Abuse | Link to thisIt's the sort of thing that gives green energy a bad name. Nevertheless, tarmac surfaces are a good target for green solutions. Just forget about efficiency (there's more than enough surface available) and look for things that can be embedded in local energy distribution networks. For example, install thermopiles (or another thermodynamic solution) under parking lots, which are usually urban.
Reply | Report Abuse | Link to thisThat roadway might possibly last a week in Michigan, if they were lucky. BUT if they could put the photo-voltaic system over the roadway then it would not need to be nearly so tough, and it could last much longer, and be cheaper to make and cheaper to service. Also, there would be no need to worry about traction on the surface, so it could be smooth and shiny and more efficient as well.
Reply | Report Abuse | Link to thisIT gets around to the question of "yes I can do it, but should I do it?"
I applaude the initiative to utilize the many miles of highway for dual purpose benefits. Can anyone tell me why it wouldn't make more sense to install piezoelectric panels where the weight of the vehicles generate power? Or thermal electric generators to capture the heat generated from absorbing the sun's rays? You would totally eliminate solar factor variables (road conditions, vehicle shading, time of day etc..). Load sensors are already in use at intersections to control traffic lights.
Reply | Report Abuse | Link to thisA response to some comments above. Glass would be more durable based on it being harder, brittle and higher tensile than softer, ductile plastic. In order to make plastic more durable, it is usually coated with an anti-scratch coating which are typically based on organo-Si-O molecules. Colorant added to plastic will reduce %T and efficiency.
Why not put elevated panels over the roadway on straight lengths. The free space is already there.
Reply | Report Abuse | Link to thisThis idea and technology will be well used on the Airports too.
Reply | Report Abuse | Link to thiswhat about accidents,and chemicals, fuels that are constantly leaking from petroleum fueled vehicles? What would this do to your plastic or paint?
Reply | Report Abuse | Link to thisWhat about driveways? There would be less wear and tear Parking lots?
Reply | Report Abuse | Link to thisDriveways and parking lots would have less wear and tear.
Reply | Report Abuse | Link to thisglass hiway should consider CIGS! higher output and they get better in the sun whereas crystaline cells get weaker and they must be kept clean! anyone who has spent the $27,900 for a basic system has found this out! $6.44 a watt for solar cells or $2.50 a watt for cigs!
Reply | Report Abuse | Link to thisGreat idea, but what happens when there is a natural disaster like a flood or a serious automobile accident? Point is, if the road is damaged, how can the power continue to be delivered without interruptions? Multiple green power solutions should probably be connected to the grid to be fully prepared if it was affordable.
Reply | Report Abuse | Link to thisI have several points to make that address the commentary here.
Reply | Report Abuse | Link to thisFirst of all, regarding plastic versus glass for this application. Certain plastics are unstable under UV radiation and would therefore disqualify them, as the constant exposure to the radiation would degrade the substrate. Plastics that are more stable would also be less desirable as compared to glass because they do not allow as much energy to pass through to the absorbing photovoltaic components.
Secondly, to address concerns about the appropriate placement of PV on roadways. Energy is lost for the longer distance that it transmitted over. Thus the higher demand of cities may be sated with adding them to buildings, however this will stress lower-income rural housing for cost of energy. Although the nation grid can support energy distribution over long distance it greatly diffuses efficiency and thus for countries such as the US, where populations are spread throughout it is not as efficient. Furthermore, this would allow electrical gridding to be installed simultaneously underground, as in European countries, which provides weather protection for the conducting cables, preventing outages from high winds (hurricanes) and lowering the amount of downed lines from ice/snow storms. Using PV panels that are not flush in the median would pose problems if a crash occurred in the median, as it could down the localized grid. Furthermore, this design could result in more injuries if crashed into.
Thirdly, to examine painting roadways versus installing panels. The chemicals that are used in producing photovoltaics must be carefully controlled. Often thin film (as is being projected for use in house paint) are often made from SIG materials, or Silicon, Indium or Gallium which must be carefully controlled in order to prevent contamination into the natural environment. Ingestion of these materials could seriously harm animals in this area, as paint can chip or be eaten. Furthermore the paints that are being developed thus far are precarious in terms of strength, and are unlikely not be able to withstand the friction of the tires constantly in contact with the paint surface.
To suggest a viable glass substance, I would look into aerogel glass, although it is expensive. The properties are very good: allowing UV radiation to pass through, but since they are prime insulators, they prevent detrimental heat from reducing the efficiency of the panels. Furthermore, they have a high mechanical strength, and they have applications as ultra-high density capacitors.