Experimental projects of solar roadways have multiplied all over the world: the potentials are endless, but many doubts remain

Think of the miles and miles of roads all over the world, what if these roads could generate energy?

According to various studies, about 0,2-0,5% of the Earth’s surface is covered by roads. This percentage is expected to increase by 60% by 2050. It is an impressive amount of land, simply taken from nature, generating a strong environmental impact.

But how can this trend be transformed into a positive impact for the environment? Recent technological innovations regarding the latest generation of photovoltaic panels, can now withstand heavy vehicle loading with a hyper-resistant structure. Use of these breakthrough Solar Panels could transform our traditional asphalt roads into huge power generators.

In China, one of the first solar highways is currently taking shape. The question is, can our highways covered with solar panels be the power stations of the future?

example of solar-roadway lane

Example of one of the first pilot projects

The invention of U.S. Solar Roadways

Solar Roadways or photovoltaic roads, are a modular system invented in the USA by Scott Brusaw, an engineer specialized in electronics and electrical engineering.

Special solar panels have been particularly designed to be walked on or driven over, although they will only be available in the future for motorways, while pilot applications for parking lots and roads with low-density traffic have already been built.

The invention has also created great interest in the federal administration, which has already initiated funding through the United States Department of Transportation, with various prototypes used to study its full potential.

The panels consist of several elements:

  • LED lighting to create lines and road signs without the use of paint
  • heating elements to prevent accumulation of snow and ice
  • microprocessors, which makes them intelligent. This allows the panels to communicate with a central control station.

The panels are made of specially formulated tempered glass that can support the weight of heavy vehicles with a treated surface similar to asphalt.

Each panel is 2 x 2 mt and is composed of four separate layers:

  • the first upper layer, is composed of a special glass alloy, which is translucent and resistant, it can bear heavy loads and also withstand extreme environmental conditions, it also allows to be crossed by sunlight
  • the solar cells that capture the light are placed in a central layer and are integrated by LED lights for lighting and road signs.
  • the lower layer is composed of an impermeable material, which also serves for the installation of cables for distributing the produced energy.
  • the entire structure, composed of the four layers, lays on any pre-existing asphalt road or alternatively on an appropriate support made of recycled materials.

The first experimental Solar Roadways project was installed in Idaho (USA) covering a distance of about 70 kilometers near Sandpoint. It is now being analyzed in order to understand if it can be replicated in other areas of the United States.

solar road panel components

The 4 layers that make up solar roadways

Benefits of solar roadways

Taking advantage of already cemented soil

One of the main obstacles in the use of solar produced renewable energy is the amount of physical space to be occupied with panels and cells, exacerbating the problem of excessive consumption of energy and soil.

We tend to install photovoltaic panels in areas that are not easily accessible, such as the roofs of our homes, offices or car parks to cope with this excessive consumption of free space. The aim of renewable energy is, as a matter of fact, to be environmentally sustainable, meaning that using up available green space for operation, will mitigate its beneficial effects.

The strong point is that by using space that was already covered by existing roads to produce renewable energy, would considerably increase the many environmental benefits. The great potential of this technology is quite obvious to and the new use of photovoltaic panels could transform the world we know today.

Road signage with integrated lighting

Since it is not possible to “paint” white stripes on the solar panels, a simple and effective solution has been adopted as a highly effective alternative: integrating LED strips into the panels. This solves the problem of providing road signs and a minimum of lighting.

solar road led lighting

LED lighting and the smart road signs system

Sensors detecting objects or people on the roads

Solar roadways could provide the smart driveway of the future also by integrating weight sensors into lanes and panels to prevent road hazards. When a person, an object or an animal crosses the road, the sensors placed in the panels will be activated by lighting that part of the road and, consequently, limiting the risk of accidents.

It would also be possible to use roads as displays to send or modify messages or road signs; inserting a stop or even warning drivers about work in progress.

example sensors solar roadway hazard

The sensor system detecting obstacles on the road

Disadvantages that limit solar roadways spread

Installation and maintenance costs

Although costs can be cut down by installing panels on top of existing roads, the price of this particular type of panels is enormous. For example, in Normandy, where the first stretch of the French road was installed, the cost was estimated to be 5 million euros per kilometer for a single lane!

In addition, the cost of installing and repairing these solar panels is likely more expensive than it would be for fixing ordinary asphalt roads.

Alongside the cost, there’s the question of low productivity.

example of solar-road panel

The horizontal modular panels adhering to the asphalt

Solar road panels are adherent and well-fixed to the road surface. They are subject to shading due to the surrounding objects but also to cars that drive over them too. This means that even when these new technologies will one day be widespread, they will never be installed in high density traffic areas or on roads close to forests or skyscrapers. Their best performance can only be limited to portions of roads that pass through open spaces without too much shading therefore well exposed to sunlight.

In addition, a solar panel lying under a road is not at the optimum tilt angle and will produce power mainly during the central hours of the day while its energy production levels will reduce drastically during the rest of the day.

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