Solar Roadway – Could we replace the road with solar panels?

So crazy it just might work? Apparently the Dept. of Transportation thinks so: Solar Roadways has received a $100,000 contract from DOT to build a prototype.

The Solar Roadway™ is a series of structurally-engineered solar panels that are driven upon. The idea is to replace all current petroleum-based asphalt roads, parking lots, and driveways with Solar Road Panels™ that collect and store solar energy to be used by our homes and businesses. This renewable energy replaces the need for the current fossil fuels used for the generation of electricity. This, in turn, cuts greenhouse gases literally in half.

The heart of the Solar Roadway™ is the Solar Road Panel™.

Each individual panel consists of three basic layers:

Road Surface Layer – translucent and high-strength, it is rough enough to provide great traction, yet still passes sunlight through to the solar collector cells. It is capable of handling today’s heaviest loads under the worst of conditions. Weatherproof, it protects the electronics layer beneath it.

Electronics Layer – Contains a large array of cells, the bulk of which will contain solar collecting cells with LEDs for "painting" the road surface. These cells also contain the "Super" or "Ultra" caps that store the sun’s energy for later use. Since each Solar Road Panel™ manages its own electricity generation, storage, and distribution, they can heat themselves in northern climates to eliminate snow and ice accumulation. No more snow/ice removal and no more school/business closings due to inclement weather. The on-board microprocessor controls lighting, communications, monitoring, etc. With a communications device every 12 feet, the Solar Roadway™ is an intelligent highway system.

Base Plate Layer – While the electronics layer collects and stores the energy from the sun, it is the base plate layer that distributes power (collected from the electronics layer) and data signals (phone, TV, internet, etc.) "downline" to all homes and businesses connected to the Solar Roadway™. The power and data signals are passed through each of the four sides of the base plate layer. Weatherproof, it protects the electronics layer above it.


When multiple Solar Road Panels™ are interconnected, the intelligent Solar Roadway™ is formed. These panels replace current driveways, parking lots, and all road systems, be they interstate highways, state routes, downtown streets, residential streets, or even plain dirt or gravel country roads. Panels can also be used in amusement parks, raceways, bike paths, parking garage rooftops, remote military locations, etc. Any home or business connected to the Solar Roadway™ (via a Solar Road Panel™ driveway or parking lot) receives the power and data signals that the Solar Roadway™ provides.

The Solar Roadway™ becomes an intelligent, self-healing, decentralized (secure) power grid.

Shown is a large-scale system (North America). This would allow the east coast to power the west coast during the first three hours of the day when the west coast is still dark. Conversely, the west coast would power the east coast during the last three hours of the day when the east coast was dark.

Imagine a world-wide system where the "lit" half of the world is always powering the "dark" half of the world!

Everyone has power. No more power shortages, no more roaming power outages, no more need to burn coal (50% of greenhouse gases). Less need for fossil fuels and less dependency upon foreign oil. Much less pollution.

How about this for a long term advantage: an electric road allows all-electric vehicles to recharge anywhere: rest stops, parking lots, etc. They would then have the same range as a gasoline-powered vehicle. Internal combustion engines would become obsolete. Our dependency on oil would come to an abrupt end.

It’s time to upgrade our infrastructure – roads and power grid – to the 21st century.

How much electricity can we really produce?

Engineers love numbers. They (the numbers, that is) generally bore people to death, but at times they are necessary for understanding. One of the biggest questions that has been asked is simply, "Can we really generate enough pollution-free electricity to power our businesses and homes?" The calculations below are presented to answer this very important question.

First, the "givens":

In the contiguous 48 states, there are over 25,000 square miles of impervious surfaces (roads, parking lots, driveways, sidewalks, etc.), not including actual buildings and structures. Continuing development adds another quarter of a million acres each year. If these impervious surfaces were replaced with Solar Road Panels™, how much electricity could we produce?

Let us make these very conservative assumptions:

We use solar cells that have a mere 15% efficiency (there is technology available that actually doubles this number)

We average only 4 hours of peak daylight hours per day (4 x 365 = 1460 hours per year)

A popular manufacturer of solar panels offers a 200 Watt model rated at 15% efficiency. Its surface area is 15.16 square feet. If we covered the entire 25,000 square miles of impervious surfaces with solar collection panels, we’d get:

((25,000 mi²) x (5280 ft / mi)²) / (200W/15.16 ft²) = ((25,000 mi²) x (27,878,400 ft² / mi²)) / (200W/15.16 ft²) =
(696960000000 ft²) / (200W/15.16 ft²) = 9194722955145.118733509234828496 Watts ≈ 9.19 Billion Kilowatts

If we average only 4 hours of peak daylight hours (1460 hours per year), this gives us: 9.19 Billion Kilowatts x 1460 hours = 13424295514511873.350923482849604 Billion Kilowatt-hours (or) ≈ 13,424 Billion Kilowatt-hours of electricity.

Now, keep in mind that this is a conservative estimate.

According to the Energy Information Administration, the United States (all 50) used just over 4,372 Billion Kilowatt-hours of electricity in 2003, while the entire world (including the U.S.) used approximately 14,768 Billion Kilowatt-hours of electricity total. It is easy to see that the Solar Roadways™ could produce over three times the electricity that we currently use in the United States. Slightly increasing the conservatively low 15% efficiency would allow the U.S. (the “lower 48”) to produce the entire world’s electricity needs.

About 40% of U.S. carbon dioxide emissions stem from the burning of fossil fuels for the purpose of electricity generation. Coal accounts for 93% of the emissions from the electric utility industry. US Emissions Inventory 2004

This is where some of the numbers become "fuzzy": as best we can tell, it is estimated that approximately half (different agencies provide different estimates, but the average is about 50%) of the greenhouse gases that are causing global warming come from the burning of fossil fuels (primarily coal) to generate electricity. The Solar Roadway™ will, therefore, eliminate half of the greenhouse gases currently being produced.

Summary: the Solar Roadway™ can cut the causes of global warming in half!

What is all this going to cost?

The average cost of asphalt roads in 2006 was roughly $16 per square foot. The cost does not include maintenance (pot hole repair, repainting lines, etc.) or snow/ice removal. The average lane width is 12 feet, so a 4 lane highway would be 12′ (width per lane) x 4 (lanes) x 5280′ (one mile) = 253440 square feet. Multiply this by $16 per square foot and your one-mile stretch of asphalt highway will cost $4,055,040.00 and will last an average of seven years.

We plan to design the Solar Roadways™to last at least 21 years (three times that of asphalt roads), at which time the panels would need to be refurbished. Adding no additional cost to the current asphalt system, this will allow us to invest about $48 ($16 x 3) per square foot. This means that if each individual panel can be made for no more than $6912.00, then the Solar Roadway™ can be built for the same cost as current asphalt roads. However, asphalt roads don’t give you anything back.

Based on 15% efficiency, each Solar Road Panel™ can produce an average of 7.6kWh per day. Our hypothetical 4-lane, one-mile stretch of road would require 1760 Solar Road Panels™. That means that, each day, this stretch of Solar Roadway™ would produce at least 13,376 kWh of electricity. That’s 4,882,240 kWh per year – enough to take 500 homes completely "off grid". You don’t get that out of asphalt!

In addition, the Solar Roadway™ replaces our current aging power grid. The Solar Roadways™ carry power – not from a centralized point like a power station, but from the power-producing grid itself – along with data signals (cable TV, telephone, high-speed internet, etc.) to every home and business connected to the grid via their driveways and parking lots. In essence, the Solar Roadways™ becomes a conduit for all power and data signals.

For an accurate cost comparison between current systems and the Solar Roadways™ system, you’d have to combine the costs of asphalt roads, power plants, and power and data delivery systems (power poles and relay stations) to be compatible with the Solar Roadway™ system, which provides all three.

2003: the US used just over 4,372 Billion kilo-Watt hours of electricity. This would require 14,574 300MW power stations (coal-fired, nuclear, etc.). For the sake of argument, let’s assume coal-fired power stations, which cost roughly $1B each for a 300MW plant.

Asphalt roads: 25,000 square miles in the “lower 48” states = 696960000000 square feet. At $16/square foot, this is a cost of $11,151,360,000,000 and the cost of asphalt is rising rapidly with the cost of petroleum. This does not include maintenance (pot hole repair, repainting of lines, snow/ice removal, etc.)

4.84 billion (12’ by 12’) Solar Road Panels™ would be required to replace the current asphalt road system, parking lots, and driveways in the 48 contiguous states. This is enough to provide three times more electricity than the United States used in 2003 and almost enough to supply the entire world.

If the Solar Road Panels™last 21 years before needing to be refurbished (not replaced), then we can triple the amount of money spent on asphalt roads, which have to be replaced every seven years.

Adding the cost of the power plants and tripling the cost of the asphalt roads, we get a total cost of $48,059,670,000,000. Divide this amount by the 4.84 billion Solar Road Panels™ required to replace the asphalt, and we get a target cost of $9923.16 per panel. This number is considerably higher if you pad in the costs of utility poles and relay stations that will no longer be needed with the Solar Roadways™ system.

In addition, there is no way to calculate additional savings such as the reduction in costs of vehicle and health insurance (due to lighted night roads, wildlife avoidance systems, snow/ice removal, etc.). Accidents and the loss of life (both human and wildlife) will be drastically reduced upon the Solar Roadways™.

Then there is the whole environmental issue: elimination of the fossil fuel plants will take away about half of the CO2 emissions that are known to be contributing to the climate crisis. Providing a means to recharge all-electric cars anywhere along the roadside will open the door for the elimination of the internal combustion engines, which account for most of the other half of the CO2 emissions. With internal combustion engines now obsolete, our dependency on oil – foreign or domestic – will finally be over with.

Conclusion: for roughly the same cost of the current systems (asphalt roads and fossil fuel burning electricity generation plants), the Solar Roadways™ can be implemented. No more Global Warming. No more power outages (roaming or otherwise). Safer driving conditions. Far less pollution. A new secure highway infrastructure that pays for itself. A decentralized, self-healing, secure power grid. No more dependency on foreign oil.

The real question may be: what will be the cost if we don’t implement the Solar Roadways™?

We’re barely keeping up with the costs of maintaining our roads and bridges as it is, and the cost of asphalt is skyrocketing. We’ve been using petroleum-based asphalt since the 1950’s, but we won’t be able to do it much longer. New materials and technologies have to be found to replace our current archaic system. The Solar Roadway™ is an intelligent road that provides clean renewable energy, while providing safer driving conditions, along with power and data delivery. The Solar Roadway™ will pay for itself through the generation of electricity. The same money that is being used to build and resurface asphalt roads can be used to build the Solar Roadways™. Then, since coal-fired and nuclear power plants will no longer be needed, the costs of all electricity generation plants can also be rolled back into the Solar Roadways™. Add too the costs of power distribution systems (power poles, relay stations, etc.).

Decentralized, secure, intelligent, self-healing power grid

Our current power grid is based on centralized power stations. Distribution of power is handled through transmission lines (overhead and underground), relay stations, and transformers. When a line goes down (ice, lighting, wind, tress, utility pole hit by car, etc.), everyone on the wrong end of the line loses power until the damage is repaired. If a power station goes down, an entire section of the country goes dark.

The Solar Roadways™ on the other hand, replaces all current centralized power stations including coal- and nuclear-powered electricity generation plants. With the Solar Roadways™, the road becomes the power grid, eliminating the need for unsightly utility poles and relay stations. Power is generated everywhere – every road, parking lot, and driveway. No more power outages, roaming or otherwise.

This is "secure" energy: it can’t be deliberately shut down. Not by terrorists, not by power companies, it simply can’t be shut down.

Electric cars have one major problem: they have to be recharged regularly. This means that they would be fit for running to the local grocery store and back, but it wouldn’t be feasible to take a cross country trip. Basically, you’d just go as far as your initial charge would take you. Since the Solar Roadway™ carries electricity, electric cars can be recharged at any conveniently located rest stop along the way, or at any business that incorporates Solar Road Panels™ in their parking lots (restaurants for instance). Just plug your car in and recharge while you’re eating or shopping. By the way: using electric cars would eliminate most of the other half of the cause of global warming and could virtually wean us off oil entirely.

Drastically reduces (over 50%) greenhouse gases

Global warming is caused by the release of greenhouse gases into our atmosphere. Approximately half of all greenhouse gases are produced by the burning of fossil fuels to create electricity. The Solar Roadway™ on a global scale eliminates this need entirely (see The Numbers). Therefore, the Solar Roadway™ will cut greenhouse gases in half.

Transportation accounts for another 25% of greenhouse gases. Electric vehicles can recharge anywhere along the Solar Roadways™. Elimination of internal combustion engines will take out another 25 percent of greenhouse gases.

Revitalizes the economy

It will take roughly five billion 12′ by 12′ Solar Road Panels™ just to cover the roads, parking lots, and driveways in the United States. Imagine the manufacturing requirements: it will create so many new jobs that it may very well become the "New Deal" of the 21st century. We can retrain workers from obsolete industries such as coal miners and asphalt workers with new "Green Collar" jobs. Unemployment rates will plummet. Vast sums of money will be injected back into our economy. We could go from being on the verge of a recession to the biggest mobilization this country has seen since WWII.

National security

Our decentralized power grid will deny terrorists an opportunity to take out our power grid. Making oil relatively worthless will take away the vast majority of terrorist funding. Eliminating the need to protect our oil interests in hostile lands will keep our troops safe and allow us to redirect the money spent on war to our needs at home.

No more nuclear power plants

Since we’ll be producing three times more electricity than we can use (see The Numbers), we’ll have no further need for nuclear power plants on any kind. No more worrying about another Chernobyl or Three Mile Island. No more stockpiles of radioactive waste.

Also, since we can provide Solar Road Panels™ to anyone in the world, we will no longer have to listen to unstable regimes insist that they need nuclear reactors to create electricity, knowing full well that what they really want to produce is weapons-grade plutonium.

Recharges electric vehicles

Since the road generates and carries electricity, electric vehicles can recharge virtually anywhere. For instance, let’s say I leave my home here in north Idaho and go on a road trip to Florida. Let’s say my all-electric vehicle gets 180 miles on a single charge. That’s about three hours worth of driving on the interstate. By then, I’d be about ready for a bathroom break or a snack. I find a restaurant that incorporates Solar Road Panels™ in its parking lot. I pull in to a parking space, plug my car into the "hitching post", and go inside. By the time I’m recharged and ready to go, so is my car. I could do the same thing at a rest stop or a shopping mall.

The EV-1 being recharged. Solar Roadways™ would allow this to occur virtually anywhere.

Frequently Asked Questions:

What happens when a Solar Road Panel™(s) gets damaged or destroyed (lightning strike, overturned vehicles, earthquake, etc.)? Couldn’t the Solar Roadways™ short out and leave us all in the dark?

No. Each Solar Road Panel™ will have electrical connections on each of its four sides. A GFI (Ground Fault Interrupter – found in our homes to prevent us from being electrocuted if we drop a hair dryer in the bathtub) will monitor each of these connections. If too much current begins to flow (short circuit?), the electrical connection will be shut off, therefore isolating any damaged panels. On a larger scale – say a fuel truck explodes, completely severing the road in half – no one would lose power. All of the panels leading up to your home would still be collecting and storing power. You may lose your cable TV or telephone (land line) until the road is repaired, but you’d still have power.

How much energy will be required to manufacture your Solar Road Panels™? Won’t this negate the environmental effect of your proposal?

That’s a hard number to pin down at this point, but consider this: here in north Idaho, our power is supplied by the Albani hydroelectric dam. We’re hoping to build the first Solar Road Panel™ manufacturing plant in Sandpoint, which has an outstanding rail system for distribution. Once the plant begins producing, the first Solar Road Panels™ to roll off the assembly line will be taken immediately out to the parking lot for installation. By the time the parking lot is finished, the plant will be off grid and energy self-sufficient. All subsequent manufacturing facility parking lots would be built out of pre-existing Solar Road Panels™, making our carbon footprint as small as possible. Don’t forget one of the main driving forces of the Solar Roadways™: to drastically reduce/eliminate the carbon footprint of all businesses and individuals.

Wouldn’t it make more sense to just build canopies over the roads to hold the solar panels? Or just place solar panels on the north side of the roads, facing the sun? That way, we wouldn’t have to be able to drive on them?

No. It would be incredibly expensive as you would still have to pay for our current asphalt roads. We plan to use the money already budgeted for roads for the replacement Solar Roadways™. If we still had to build current roads plus the canopies or side panels, the cost would likely be so high that taxes would have to be raised to cover it. You would also lose most of the features of the Solar Roadways™, such as being lit by LED’s for safer night driving. The side panel idea would do nothing to keep the roads free of snow and ice, so northern cities would still have the removal expense and the accidents caused by the unsafe road conditions. Many of the other features would be lost too, such as saving the lives of millions of animals, a self-healing, decentralized power grid, all aspects of an intelligent road: reporting in with potential problems, reducing crime and terrorism, etc.

What are you going to do about traction? Cars slip and slide on wet asphalt, let alone wet glass. What’s going to happen to the surface of the Solar Roadways™when it rains?

Everyone naturally pictures sliding out of control on a smooth piece of wet glass! Actually, one of the many technical specs for the top layer it that it be textured to the point that it provides at least the traction that current asphalt roads offer – even in the rain. I hesitate to even call it glass, as it is far from a traditional window pane, but glass is what it is, so glass is what we must call it.

Last year, I attended a three day workshop called the International Workshop on Scientific Challenges for New Functionalities in Glass in Arlington, Virginia. I received quite an education in the properties and abilities of glass! I presented the Solar Roadways™ to an international audience of glass scientists. Afterward, I was invited to travel north and present our project to Penn State University’s Materials Research Institute. I had lunch with several of their research scientists after my presentation. By the end of this trip, I had been thoroughly convinced that the glass specs that I had presented would not pose any problems – and traction was the easy part.

How are you going to keep the surface clean?

While at the International Workshop on Scientific Challenges for New Functionalities in Glass, I learned of a new technology: self-cleaning glass. From Wikipedia: “Self-cleaning glass is a specific type of glass with a surface which keeps itself free of dirt and grime through natural processes. The glass cleans itself in two stages: the ‘photocatalytic’ stage of the process breaks down the organic dirt on the glass using ultraviolet in sunlight (even on overcast days) and makes the glass hydrophilic (normally glass is hydrophobic). During the following ‘hydrophilic’ state, rain washes away the dirt – leaving almost no streaks, because hydrophilic glass spreads the water evenly over its surface.”

It is yet to be seen if this process will be enough to keep our Solar Roadways™ operating under optimal performance (100% clean surfaces), but it will certainly put a dent in a potential problem. There will be some obvious obstacles such as oil spills, sandstorms, storm debris, etc. Here’s the worst case scenario: when I was a kid in southern California, we used to chase street sweepers (vehicles with large rotating brushes) down the street. We still use them in the springtime here in north Idaho to clear the roads of the sand that was used for traction during the winter months. Similar vehicles could be used when needed to maintain a clean road surface on the Solar Roadways™. Again, this is worst case and only if the self-cleaning properties of the glass aren’t enough to do the entire job.

How much power can you expect to get out of a one-mile stretch of road?

One mile = 5280 feet. Our Solar Road Panels™ are 12′ by 12′. Therefore, it will take 5280/12 = 440 panels to create one mile (one lane, 12 feet wide). Each panel is expected to produce 7600Wh of electricity based on 15% efficiency and four hours of sunlight per day (for more details, see the Numbers page).

440 times 7600Wh = 3.344MWhr per lane per mile. So a typical four lane highway will produce 13.376MWhr per mile, based on four hours of sunlight per day.

According to a 2007 study by the Energy Information Administration, the average American home used 936kWh per month. Dividing this number by 30 will give us an average need of 31.2kWh per day. Dividing this number into the 13.376MWhr per mile, gives us approximately 428. That’s how many American homes can go "off-grid" for every mile of 4-lane Solar Roadway. We can wean ourselves off coal. Again, that’s based on four hours of sunlight per day.

Some of the roads in our neighborhood never see sunlight. Does that mean that we’ll never see the Solar Roadways™ in our neighborhood?

No. Every Solar Road Panel™ has the ability to collect and store energy from the sun. Even the panels that never see sunshine can store the energy collected by nearby panels that are in the sun. We would install Solar Road Panels™ in tunnels and under bridges, knowing that they will never see sunlight themselves. Remember, we can produce three times more electricity than we have ever used. Theoretically, that means that only one-third of the Solar Road Panels™ ever have to see the light of day. The rest of the "shaded" panels will act as energy storage devices. They will still light up (nice for those tunnels!), melt snow and ice, report problems, etc., using the power that was collected by the panels in the region that did have access to sunlight.

Won’t traffic congestion or full parking lots make the Solar Roadways™ less efficient?

Any shade on a solar panel prevents it from producing at its maximum capacity. However, traffic or parked cars will have a negligible impact.



Funds intelligent roads and parking lots

SOLAR ROADWAYS, SAGLE, IDAHO (August 25, 2009)- Solar Roadways today announced that it has been awarded a DOT contract that will enable them to prototype the first ever Solar Road Panel.

The Solar Roadways will collect solar energy to power businesses and homes via structurally-engineered solar panels that are driven upon, to be placed in parking lots and roadways in lieu of petroleum-based asphalt surfaces.

The Solar Road Panels will contain embedded LEDs which "paint" the road lines from beneath to provide safer nighttime driving, as well as to give up to the minute instructions (via the road) to drivers (i.e. "detour ahead"). The road will be able to sense wildlife on the road and can warn drivers to "slow down". There will also be embedded heating elements in the surface to prevent snow and ice buildup, providing for safer winter driving. This feature packed system will become an intelligent highway that will double as a secure, intelligent, decentralized, self-healing power grid which will enable a gradual weaning from fossil fuels.

Replacing asphalt roads and parking lots with Solar Roadway panels will be a major step toward halting climate change. Fully electric vehicles will be able to recharge along the roadway and in parking lots, finally making electric cars practical for long trips.

It is estimated that is will take roughly five billion (a stimulus package in itself) 12′ by 12′ Solar Road Panels to cover the asphalt surfaces in the U.S. alone, allowing us to produce three times more power than we’ve ever used as a nation – almost enough to power the entire world.