SOLAR PANELED ROAD

1. INTRODUCTION

Nature has provided bountiful resources surrounding us for sustenance of a better life. These resources, along with manpower and capital, play a crucial role for expansion to national output. However, the advancement of modern civilization has had a great impact on our planet's natural resources. Therefore sustainable solutions are a requirement for modern design problems due to society’s overreliance on natural resources. Thus innovative ideas which focus on sustainability must be considered as a key priority for design and optimization.

One of the primary solutions for this problem is the increase in use of renewable energy resources. Different types of renewable energy resources are solar, wind, ocean and geothermal energy. Among these, solar energy is the only resource which is abundantly available and evenly distributed worldwide. Hence developing technologies to capture this solar energy is the need of the hour.

In order to overcome the relatively low efficiency of the solar panels, significantly large amount of open spaces are required for the production of electricity in the photovoltaic solar panel applications. Since availability of large open spaces is on the decline near the urban areas, the solar panels can only be installed in remote areas. But this can lead to huge energy losses. The low efficiency of the solar panels as well as the necessity to deal with the transmission losses makes the use of solar panels a non-viable economical option to produce electricity. In order to make the solar power a viable economical option, open spaces that are situated close to the high energy demand areas must be identified. Hence, it is proposed that open spaces such as the roads, parking lots, bicycle lanes, footpaths etc. be utilized for this purpose. In order to use these open spaces for producing electricity using solar panels, recently, the concept of solar roadways have been introduced.

The Solar Roadway is a series of structurally-engineered solar panels that are driven upon. It would utilize the use of roads that would be covered by photovoltaic panels. The idea is to replace all current petroleum-based asphalt roads, parking lots, and driveways with Solar Road Panels that collect energy to be used by our homes and businesses. . The ultimate goal is to store excess energy in or along-side the Solar Roadways.

Through the issues associated with urban heat islands it is known that pavements are often exposed to a vast amount of solar radiation throughout the day. If it was possible to convert a portion of this energy to usable forms, civil and infrastructure issues could be solved simultaneously. Two methods have already been developed to generate energy from roads, using asphalt pavement as a solar thermal collector and installing piezoelectric generators to collect vibration energy from the traffic load on the pavement. Recent studies have also begun to use thermoelectric systems to extract heat energy from roads and directly convert it to electricity. This project is taking a different approach to the concept as, through photovoltaics. Radiation is directly converted into electricity on the surface of the panel without a heat or vibration conversion.

1.1 SOLAR ROADWAYS

A solar roadway is a road surface that generates electricity by solar power photovoltaic cells. It consists of structurally engineered solar panels that we drive on.
Each Solar Road Panel (roughly 12’ by 12’) interlinks with neighbouring panels to form the Solar Roadways system. The Solar Roadway replaces our crumbling petroleum-based asphalt highway infrastructure with an intelligent road that pays for itself through the generation of electricity. The Solar Roadway generates electrical power from the sun and becomes our nations decentralized, intelligent, self-healing power grid, replacing our current deteriorating power distribution infrastructure.

The Solar Roadway distributes its electrical power to all businesses and homes connected to the system via their parking lots and driveways (made up of Solar Road Panels). In addition to electrical power, data signals (cable TV, high-speed internet, telephone, etc.) also travel through the Solar Roadways, which acts as a conduit for these signals (cables). This feature eliminates the unsightly power lines, utility poles, and relay stations we see all over the countryside. It also eliminates power interruption caused by fallen or broken electrical lines or poles.

Fig 1.1: Solar roadways

1.2 PHOTOVOLTAIC

The main philosophy of solar roadways is to convert solar energy into electrical energy by the principle of photovoltaics. Photovoltaics (PV) is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material.

To understand how photovoltaic operate, the nature of sunlight has to be understood. The structure of all type of light consists of electromagnetic radiation which is similar to micro and radio waves. When an electromagnetic radiation becomes incident on a semiconductor material (p-n junction), the photons are absorbed by the material and electrons are knocked loose from the atoms in the semiconductor material.  If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current, that is, electricity. This electricity can then be used to power a load, such as a light or a tool.

2. TYPICAL SOLAR ROADWAY

A solar roadway is a series of structurally engineered solar panels that are driven upon. The idea is to replace current petroleum-based asphalt roads, parking lots, and driveways with solar road panels that collect energy to be used by homes and businesses, and ultimately to be able to store excess energy in or alongside the solar roadways. The renewable energy generated by solar road panels will replace the current need for fossil fuel, which in turn reduces the greenhouse gases.

Parking lots, driveways, and eventually highways are all targets for the panels. If the entire United States Interstate Highway system were surfaced with Solar Roadways panels, it would produce more than three times the amount of electricity currently used nationwide.

Existing prototype panels consist of three layers.

Road surface layer - translucent and high-strength, textured glass, that is rough enough to provide sufficient traction, yet still passes sunlight through to the solar collector cells embedded within, along with LEDs and a heating element. This layer needs to be capable of handling today's heaviest loads under the worst of conditions and to be weatherproof, to protect the electronics layer beneath it.

Electronics layer/Optical layer - It transmits the load around the solar cells. It contains a microprocessor board with support circuitry for sensing loads on the surface and controlling a heating element with a view to reducing or eliminating snow and ice removal as well as school and business closings due to inclement weather. The microprocessor controls lighting, communications, monitoring, etc. With a communications device every 3.66m (12 feet), a solar roadway can be an intelligent highway system.

Base plate layer - While the electronics layer collects energy from the sun, it is the base plate layer that distributes that power as well as data signals (phone, TV, internet, etc.) down the line to all homes and businesses connected to the solar roadway. It has to transmit the load to a pavement, subgrade, or base structure. It needs to be weatherproof to protect the electronics layer above it.

Fig 2.1: Exploded view of a conceptual solar road panel

(http://www.tac-atc.ca)

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.

3. STRUCTURAL REQUIREMENTS

The structural design requirements for a solar road panel are as follows:

· The structure must be able to support the cyclic distributed load from vehicle tires without failing through deformation, fracture.

· The transparent layer cannot deflect over the cell compartments so much that the layer transmits load to the solar cells.     

· The structure must be corrosion resistant to potential contaminants.        

· The design must be modular and facilitate easy maintenance.      

· For this prototype's purposes, the panel must be made out of readily available components and materials.      

· The weight of the panel must be low enough such that it can be easily maneuvered for testing and installation purposes.

4. ELECTRICAL DESIGN REQUIREMENTS

The electrical design requirements for a solar road panel are as follows:

· The panel should be designed so that no shading of the solar cells occurs.       
· The interconnection between the cells should be strong enough to withstand potential deflections from the optical layer.      
· The panel must be weatherproof so that water and other contaminants are not able to interfere with the electronics.   
· There must be a diode installed on the output electrical line of the panel to block reverse currents, as this would damage the solar cells within the panel.

5. DESIGN

In The University of Western Ontario, the design of the panel was done by COMSOL Multiphysics, an engineering simulation software. COMSOL Multiphysics which has both the modeling and simulation capabilities for Multiphysics systems was used to ascertain the feasibility for different vehicular applications and for suggesting future material The model created in the COMSOL Multiphysics for the analysis purpose consists of a vertically hollow square base layer with sides 4 meters in length, 0.5 meter in height and 0.1 meter in thickness..The base layer is considered to be made up of concrete, and covered with a transparent cover of size 4 m and thickness 0.01 m made up of acrylic plastic, whose material properties are given in Table 1. The acrylic sheets have a working temperature range of -40°C up to 93°C, and the elastic properties are assumed to remain constant in this temperature range.

Table 5.1: Material properties for Acrylic plastic and Concrete

(Source: ir.lib.uwo.ca)

As the solar roadways panels are to be laid over the existing roads, the primary loads acting on the solar roadways panels are the vehicle loads. For the analysis, the loads associated with the vehicles are selected based on the specification from American Association of State Highways and Transportation Officials (AASHTO). Two types of loadings, H loading and HS loading are given by AASHTO. H loading consists of a two axle truck and HS loading consists of a tractor truck with semi-trailer. In general, there are four standard classes of highway loading conditions, namely H15, H20, HS15 and HS20. The number following the H and HS letter denotes the gross weight in tons of a standard truck. The HS20 standard truck load, a maximum stress of 1.82x103Mpa is much higher when compared to the ultimate tensile strength of 69Mpa and the displacement results indicate that maximum surface displacement was also very high at 1.12 meters. Hence it can be concluded that the selected top cover material is not suitable for the applied load and this cannot be used as a top cover for solar roadways panel, where vehicles of size similar to a truck are moving over it.

As the selected material failed for the load of a truck, in order to test the maximum load the material selected for the top cover of solar roadways panel can take on, stress and displacements due to a car, bicycle and a motorbike load moving over the solar panel were analyzed. The specifications of the vehicles are given in table 2.According to standard specifications and code of practice for road bridges (IRC: 6- 2000), the car and the motorbike belongs to Class A loading and bicycle belongs to Class B loading.

Table 5.2: Specifications of car, motorbike and bicycle used in the analysis

(Source: ir.lib.uwo.ca)

The size of selected base layer was 1.5 m x 0.2 m x 0.1 m, covered by a transparent top cover of size 1.5 meters and with a thickness of 10 mm. It was found that the total weight of the bicycle, 90.7kg (including weight of the bicycle and person travelling on it) caused a stress of 20.67MPa, which is quite low when compared to the ultimate tensile strength of 69MPa. The maximum surface displacement was 2.05mm, which is well below the AASHTO design standard. Whereas in the analysis considering
motorbike and car it was found that if the young’s modulus is increased from 50.8x109 to 50.8x1010 Pa, a thickness of 15mm and 25.4mm was suitable for both vehicles respectively.

6. WORKING

· When a solar panel exposed to sunlight , the light energies are absorbed by a
semi conduction materials.
· Due to this adsorbed energy, the electrons are liberated and produce the external DC current.
· The DC current is converted into 240-volt AC current using an inverter for different applications.

7. MECHANISM

• First, the sunlight is absorbed by a solar cell in a solar panel.        
• The absorbed light causes electrons in the material to increase in energy. At the
same time making them free to move around in the material.
• However, the electrons remain at this higher energy for only a short time before
returning to their original lower energy position.          
• Therefore, to collect the carriers before they lose the energy gained from the
light, a PN junction is typically used.      
• A PN junction consists of two different regions of a semiconductor material (usually silicon), with one side called the p type region and the other the n-type region.
• During the incident of light energy, in p-type material, electrons can gain energy and move into the n-type region.  
• Then they can no longer go back to their original low energy position and remain at a higher energy.           
• The process of moving a light- generated carrier from p-type region to n-type region is called collection.           
• These collections of carriers (electrons) can be either extracted from the device to give a current, or it can remain in the device and gives rise to a voltage.  
• The electrons that leave the solar cell as current give up their energy to whatever
is connected to the solar cell, and then re-enter the solar cell. Once back in
the solar cell, the process begins again.

8. APPLICATIONS

8.1 ILLUMINATED ROADS

Unlike the dark roads we drive on by night today, the Solar Roadways will have LEDs which will "paint" the lanes, and can be instantly customized as needed. The LEDs could be utilized to create messages on the roads to warn drivers of detours, accidents, or construction works up ahead. With an illuminated highway, accidents will be reduced and night time driving will be safer.

Fig 8.1: Solar roadway with pavement markings
(http://solarroadways.com)

8.2 SNOW / ICE MANAGEMENT

A benefit to the use of solar roadways is that the de-icing of roads will not be required; this is due to panels being capable of self heating, and the glass incorporating the same heating elements of a car’s rear screen. The panels will have sensors which will determine when the temperature falls below a certain point and will activate the heating system which will prevent the buildup of snow and ice. Thus eliminates the use of deicing salts and the impacts that arise due to their use such as, contaminated surface runoff and rusting of road structures and vehicles.

8.3 TRAFFIC MANAGEMENT

Each Solar Road Panel contains a microprocessor that monitors and controls the panel, while communicating with neighboring panels and the vehicles traveling overhead. The dashed road lines that are seen on highways can travel alongside at the designated speed limit, thus helping us to maintain proper speed. The road can warn about traffic congestions ahead and even recommend detours around it. It can even notify law enforcement to assist in tracking down stolen vehicles or
suspects’ cars equipped with GPS tracking devices. Crosswalk panels can alert drivers when pedestrians are on the crosswalk. Once the crosswalk panels detect a pedestrian, the LEDs within the crosswalk begin flashing and a warning is displayed in front of oncoming vehicles. Wildlife protection system works in the same way. If a vehicle crosses the center line too many times within a given distance, a ring of LEDs can be drawn around the vehicle, which will travel with it indefinitely. This will warn other drivers of a potential danger and will alert law enforcement officials of a potential problem. The Solar Roadways could drastically reduce the number of deaths/injuries caused by impaired driving. It can save electricity by turning on roadway lighting in remote areas only when a vehicle comes along.

Fig 8.2: Pedestrian warning system        Fig 8.3: Wildlife protection system (http://solarroadways.com)

8.4 NATIONAL SECURITY Trucks with hazardous materials can be tracked and monitored. Suspected terrorist's vehicles can be tracked. Public buses and school buses can be tracked. These vehicles can be fitted with controls to shut down their engines and/or apply their brakes.

8.5 HOMES / BUSINESSES

Businesses will be able to have solar parking lots, which will enable them to quickly go off grid as well as offer their customers the convenience of allowing their electric vehicles to recharge while they are shopping, eating, working etc. They will no longer have the expense of snow removal. Their parking lots will be safer at night with the light provided by the LED's. Walkways can be replaced with similar solar panels, enabling more energy collection, and the safety features like lighting and heating. A solar driveway will have many features, including LED lit address markers and the ability to add customized wording, such as "Happy Birthday Heather!" or "Wedding reception here. The driveway will also become an instantly customizable sports court. One minute, teenagers can be playing basketball and, at the touch of a button, the younger children can play Four Square or Hopscotch or any other game that the homeowner would like to configure. Pool surrounds and courtyards will be another ideal application for homeowners.

Fig 8.4: Sports court created from solar roadways

(http://solarroadways.com)

8.6 SOLAR ROADWAY LIGHTING

The solar roadways can be supplemented by solar-powered led roadway lighting system. Highly efficient, long lasting, environmentally friendly and controllable LEDs have opened up a whole new world of possibilities for lighting. In some remote areas where the grid power cannot reach, solar powered lighting using high-power LED provides a promising solution. LED will reduce the power consumption as well as LLP (loss of load power) and thus is the best choice for solar roadway lighting. A new pilot project by Philips and the Kenyan Urban Roads Authority to install solar-powered LED street lighting in Nairobi has the potential to generate up to 100 per cent energy savings, if implemented on a wide scale across the country. The key to the breakthrough lies in the combination of new High Brightness LEDs with unique patented optics and an intelligent controller which lies at the heart of the solution.

Fig 8.5: Diagram showing the working of solar road lighting (http://www.philipsafricaroadshow.com)

8.7 TRAFFIC LIGHTS

Solar traffic lights are signaling devices powered by solar panels positioned at road intersections, pedestrian crossings and other locations to control the flows of traffic.The electricity generated by the solar roadways can be used to function the traffic lights.

8.8 TRAFFIC SIGNS

LEDs can be embedded in standard highway warning and regulatory signs to outline either the sign itself or the words and symbols on the sign.. In general, embedded LED units are used to:

• Improve driver compliance with regulatory signs through improved conspicuity; and
• Enhance visibility and recognition of regulatory and warning signs to drivers, especially under low-light or low-visibility conditions. Solar roadways can be used to power these equipments.

Fig 8.6: (a) solar powered road sign            (b) solar powered traffic light 

(http://www.theworld-export.com)

9. COMPARISON BETWEEN BITUMINOUS ROADS AND SOLAR  ROADWAYS

Bituminous roads are those roads in which some binding material such as bitumen, coal-tar or asphalt is used in surfacing. Such roads are also known as black top roads. The following are the various types of bituminous surfaces:

1) Surface painting or surface dressing

2) Bituminous macadam

3) Bituminous concrete

4) Sheet asphalt or asphaltic mat

Traditional roads are chiefly composed of aggregates and a binding material whereas solar roadways are made of glass, solar cells and concrete. Bituminous materials or asphalts are extensively used for roadway construction, primarily because of their excellent binding characteristics and water proofing properties and relatively low cost. Despite the benefits there are also numerous drawbacks such as brittleness at low temperatures, softness at high temperatures and environmental issues such as high energy demand and pollution due to its production.

Asphalt works, in many ways, and is convenient to lay-down, compared to other methods. It has carried our automotive infrastructure into the 21st century. But there are hidden costs that are making it increasingly difficult and expensive to continue favoring asphalt as the predominant road-paving model for the entire nation. That’s why asphalt is not ideal for road construction. Bitumen roads have a design life of 10 to 20 years and require resurfacing every seven years approximately, whereas solar roadways have a design life of twenty one years.

Solar Roadways can pay dividends for the public budget, making our spending on infrastructure more efficient and significantly reducing electricity costs to consumers and businesses. They can make the emerging electric vehicle economy far more affordable, and easier to manage. They can help us eliminate hundreds of billions of dollars per year, or more, in externalized costs of burning fossil fuels. And, we can lead the world in powerful clean energy technology exports, capable of rolling back massive pollution and greenhouse gas emissions.

Road construction and expansion have major environmental impacts. The environmental impact of road projects include damage to sensitive ecosystem, permanent disruption to local economic activities ,demographic change, accelerated urbanization and the introduction of diseases due to pollutants. In addition, there are also the emissions which are released in the various stages of construction process. The amount of greenhouse gases released directly and indirectly by an individual, organization or event is known as carbon footprint. The road carbon footprint exists as bitumen requires extracting, refining and transportation to the location in order construct the road, with the addition of the maintenance and repair energy requirements later in the life of the road. Vicroads a company based in the state of Victoria, Australia, recently carried out a project to determine the carbon footprint of road construction. The company duplicated the Mickleham Road, the road was 2.4km long and consisted of 4 lanes, and they also carried out maintenance work for the project which included installation of new traffic signals, street lighting and drainage. On the completion of the project it was determined that a total of 1,820 tonnes of green house gases were released. From the data collected it was determined that 190 tonnes of CO2/km/lane was emitted for the project. To offset the emissions released for the total project required the planting of approximately 7,500 trees.

As solar roadways will not be constructed by the use of bituminous materials it will reduce the use of fossil fuels, as mentioned previously the obtaining and applying of bitumen causes damage and releases emissions into the environment. The main environmental impacts that arise due to the solar roadways are the pollution which is generated during their manufacturing of the road sections, but this is offset by the panels’ ability to recoup it by the solar energy transfer into electrical power.

The production of the glass surface panels consumes a lot of energy as the main materials in the production of glass require them to be melted to high temperatures reaching 1500°C, although this is a high temperature an additive has been added to lower the temperature. In the UK the lifecycle CO₂ emissions for a photovoltaic system is 58g CO₂eq/kWH. The same system if installed in southern Europe, Spain would have lifecycle CO₂ emissions of 35g CO2eq/kWH the decrease is due to their being more sunlight present which means greater operating hours.

A benefit to the use of solar roadways is that the de-icing of roads will not be required. One of the impacts associated with bitumen roads is the use of de-icing salts. There are numerous varieties of de-icing salts which are used on our roads; calcium chloride, potassium chloride, magnesium chloride and sodium chloride. De-icing salts used by countries for winter road protection accumulates to 51% of the worlds output of salt.

The use of salts has many effects on the environment, damage occurs to vegetation, water, roads, road structures and vehicles. As salt is very soluble it will dissolve with water, and this is the major problem when water seeps into the ground or water courses where it alters the properties of the water. The chloride ions present in the salt then raise the chloride concentrations of the streams, lakes, soils and groundwater sources causing them to have adverse effects on the aquatic plants and land. The use of salts also increases deterioration rate in roads and structures as the chloride ions react with the reinforcements and cause rust to form and leads to corrosion.

One of the major drawbacks in the use of bitumen is the failure of road surfaces due to water infiltration into the layers of the road. The deterioration rate increases due to the environmental factors of freeze and thaw. With solar roadways the surface will be 100% water proof and this will prevent the penetration of water into the lower layers. Thus the solar roadways will require lesser maintenance. Moreover in order to carryout necessary repairs and installations of underground utilities, excavation of the roads is required. Since solar roadways consists of panel sections, if the utilities require repair or replacement the road can be cordoned off in sections without excavation of soil or road layers. This will therefore lead to faster installation and repair process time.

Another advantage of solar roadways is the micro texture of the surface unlike the bitumen roads where the aggregates lose their roughness (become smooth) due to weathering and polishing effects due to traffic. The solar roadways surface will experience these factors but as glass has high resistance to wear and tear, this problem is less likely to affect solar roadways.

The panels will get damaged and will not supply any electricity if subsidence on road occurs .Subsidence is a major problem as it cannot be determined when it will occur. Traditional roads are able to flex when subsidence occurs, but the solid state of the solar roadways panel poses a problem. Another problem which will be encountered in its implementation is the geometry of the road. Bitumen roads curve naturally and smoothly in corners without any restriction whereas a solar roadway consists of rigid structure and it may create problem in achieving the natural curve of the road.

10. ADVANTAGES AND DISADVANTAGES

10.1 ADVANTAGES

Ø Renewability and life-span

The main advantage of the solar roadway concept is that it utilizes a renewable source of energy to produce electricity. It has the potential to reduce dependence on conventional sources of energy such as coal, petroleum and other fossil fuels. Also, the life span of the solar panels is around 20 years, much greater than normal asphalt roads, which only last 7–12 years.

Ø Military and rescue assistance

In the event of an environmental disaster or military emergency, solar roadways would provide power when it is needed most. As solar power is renewable, it obviously requires no external connection to an artificial power source.

Ø Roadways already in place

Another advantage of solar roadways is that they do not require the development of unused and potentially environmentally sensitive lands. This is currently a very controversial issue with large photovoltaic installations in the South western US and other places. But since the roads are already there, this is not an issue. Also, unlike large photovoltaic installations, new transmission corridors – perhaps across environmentally sensitive land – would not be required to bring power to consumers in urban areas. Transmission lines could simply be run along already established roadways.

Ø Lighting up of roads

By adding LEDs beneath the transparent panel, road can be lightened up for safe night travel and aesthetic look.

10.2 DISADVANTAGES OF SOLAR ROADS

Ø Maintenance costs:

They are more because road surfaces accumulate rubber, salt, soil and other substances that block sunlight and must be removed. The durability of the panels may also be less, further increasing maintenance costs.

Ø Seasonal efficiency:

In India the solar road will work efficiently in summer, while it will give comparatively less efficiency in other seasons due to lack of solar radiations. Where as in the countries where summer lasts for more than half of year this technique can be efficiently used.

11. CONCLUSION

The need of the hour for an alternative energy source is increasing at an alarming rate. We can't wait any longer to find a replacement for oil, which is rapidly disappearing. The solar roadways if implemented can be a solution for all our energy concerns.

In developing countries the major part of the geographical area is to be explored in terms of road connectivity. So instead of implementing the higher targets roads to be developed per day such countries can reduce the target and develop solar road so they could improve economy with infrastructure.

Generally the Solar Roadways will provide safer driving conditions, snow and ice management, traffic management, wild life protection. It is compiled solar panels which to replace ordinary asphalt street as it has better features. It is able to produce electricity and heating elements. It is designed with LED lights which able to act as traffic lines, road indicators, construction detours and streetlight for roadways. It would be solar panel field, internet distribution system, and communication system in the future. The reasons why solar roadways project is viable are to lessen fossil-fuel dependency and reduce global warming activity. It also has some of its drawbacks such as high cost, durability, and weather. However, we believe that we would able to overcome those limitations eventually in order to serve the society with greater efficiency.

12. REFERENCES

1. Kulkarni, A.,(2013), “Solar Roadways-Rebuilding our Infrastructure and
Economy”, International Journal of Engineering Research and
Applications(IJERA), Vol. 3, Issue 3, pp.1429-1436, May-Jun 2013

2. Northmore, A., Tighe, S.,(2012),“ Innovative Pavement Design: Are Solar Roads
Feasible?” 2012 Conference of the Transportation Association of Canada Fredericton, New Brunswick

3. Rushing, S.T., Tingle.,S.J.,(2009), “Full-scale evaluation of mat surfacings for
roads over sand subgrades” Journal of Terramechanics, vol 46 (2009) 57–63 

4. Selvaraju, K.R.,(2012), “Characterization of Solar Roadways via computational
and experimental investigations”, ir.lib.uwo.ca

5. Symeoni, A.,(2012), “A review on energy harvesting from roads”,
http://kth.diva-portal.org.pdf