A Comparison of Solar Roadways to Conventional Asphalt Roads

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May 13, 2023


FEATURED INSIGHTS / Synthetic Biology


A Comparison of Solar Roadways to Conventional Asphalt Roads

Solar Roadways to Conventional Asphalt Roads – Air pollution, which experts consider one of the most significant environmental health risks, causes approximately 4.2 million deaths worldwide each year due to serious illnesses. Mobility and transportation, particularly vehicles on the road, contribute significantly to these statistics by accounting for 8 million metric tonnes of CO2 emissions annually, of which 74% is produced by these vehicles. In order to electrify light, medium, and heavy-duty transportation sectors, which will result in a reduction in localised air pollution and improved air quality, the generation of clean energy is necessary.

To generate electricity, many nations still heavily rely on burning fossil fuels, which transfers emissions from the tailpipe to the power plant, meaning that the proliferation of electrified vehicles does not necessarily result in a reduction in global emissions and pollution. The construction of equipment to capture renewable energy sources such as solar and wind is advantageous. However, negative connotations associated with aesthetics and the impact on agricultural land are also linked to it.  Nuclear, whilst also ‘renewable’ has larger concerns related to safety and public perception.

The installation of solar roadways to supplement electrification of the light, medium, and heavy-duty fleet is one such recent development and application that is currently the subject of additional research regarding the production of ‘clean’ energy for the transportation sector. Solar roadways use already-existing road networks to capture solar energy as it strikes the road’s surface and converts it into electricity. To power road infrastructure, clean, renewable energy is used directly or sent to the grid.

Solar Roadways vs Asphalt Roads

It is reasonable to assume that covering just a small proportion of the world’s 21-32 million kilometers of road network with solar panels could produce a significant amount of electricity. Theoretically, installing solar panels on just a small proportion of roads should provide enough energy to power towns and cities. However, under ideal circumstances when the solar panels are directly exposed to the sun, this applies only. The basic engineering of solar roadways is fairly robust and attractive. However, are they economically viable, and are there more suitable alternatives for generating the increases in energy required for electrified vehicles?

Construction companies currently construct roads from asphalt and maintain them as cheaply as possible. This is because there is an abundance of them and creating and maintaining them is expensive. Individual solar panels used in solar roadways cost $6,912 per square foot, making them 10 to 40 times more expensive than traditional asphalt roads ($16 per square foot), depending on their use case. However, the amount of electricity generated may not always offset the additional cost.

One advantage of solar roadways over traditional asphalt ones is that they are typically more robust. They estimate that the average lifespan of a solar roadway is around 21 years. This is approximately 3 times that of an asphalt road. They attribute the longer lifespan of solar roadways to the use of more advanced materials during construction. However, they anticipate that the energy-generating capacity of the solar roadway will deplete over time, making replacement necessary due to decreased capacity rather than a lack of material robustness.

Challenges of solar roads for efficient energy generation

Installing solar panels on the road enables quick and efficient melting of ice and snow, and warms the roads before cold conditions arrive, resulting in a more efficient way of clearing roads than using asphalt roads that require mechanical intervention. Having clear roadways is advantageous since this improves safety and productivity and allows people to travel in circumstances that would typically not be possible with traditional asphalt roads.

On a conventional solar farm, people angle solar panels toward the sun to increase efficiency. Designers of more sophisticated solar farms make the panels track the sun’s movement, increasing the amount of energy captured. A typical solar panel can use about 20% of the sun’s energy. One must adjust the panels accordingly to optimize their exposure to light and operate the system cheaply. Conversely, solar roads that lay flat reduce the panels’ exposure to direct sunlight, which reduces their effectiveness. Compared to direct sunlight, laying a flat solar panel results in a 60% loss of power. The environment around it (tall buildings that shield the roadway) further limits the already inadequate amount of available energy.

Flat panels lose 50% power with 5% coverage and are more susceptible to shading, even when not driven over. They may gather dirt, need thick glass to bear weight, and have limited light absorption.

Challenges with Solar Roadways’ Effectiveness and Lighting

Fixed solar panels heat up more than rooftop solar panels due to a lack of air circulation. The energy efficiency of solar panels decreases by about 0.5% for every 1°C above the optimal temperature. Ignoring their lifespan deterioration, the panels are at a disadvantage even under optimal conditions.

Although there are millions of kilometres of roads, the area they cover is relatively small. In the UK, the surface area is around 2 billion m2. However, buildings in the UK’s urban areas occupy an area of approximately 17.6 billion m2. Solar panels on a fraction of UK rooftops would produce more power than on roads.

Solar roadways provide LEDs, replacing the need for road paint and traditional lighting, a benefit over asphalt roads. However, making the lights visible without consuming too much power strikes a delicate balance that must be achieved. Shielding solar roadway lights during the day is difficult, making them challenging to see, unlike traditional road lighting. They would be visible at night, but this also presents a challenge. The lights would draw power directly from the grid since no electricity is generated at night.

Challenges and Potential Solutions for Solar Roadways

The inherent brittle characteristics of glass further limit the road’s capacity to generate electricity. Debris buildup on the surface of solar roads will cause scratches and wear, reducing efficiency and durability over time. Glass shards may also harm the vehicles that use the road. Advanced polymers could be considered when building the roads to protect the panels. The majority of polymers, however, are expensive to produce in large enough quantities to construct a road strong enough to withstand constant traffic.Additionally, using fossil fuels to produce the material frequently defeats the purpose of using solar panels to reduce carbon emissions. Furthermore, the glass substance will turn opaque as the panels deteriorate. The clarity of the glass would significantly diminish the ability of the panels to capture light.

Finally, the cost of installing the system would never be more effective or practical than simply installing solar panels in far more effective configurations. When the cost is accounted for, replacing asphalt with a glass panel becomes prohibitive. Currently, no coating can withstand the force of moving vehicles and generate electricity simultaneously.

A German start-up company called Solmove has created a system of glass panels that they say will last 25 years and allow inductive charging of vehicles while in motion. This addresses consumer worries about the infrastructure for charging and roadblocks like range anxiety that prevent the uptake of electric vehicles. Other projects have been demonstrated in the USA and France, but these have had limited success.

The Future of Solar Roadways for Electricity Generation

Due to the cost, usability, and efficiency of solar roadways, both urban and rural areas have difficulty implementing them. While these difficulties persist, the decreased energy production from the use of fossil fuels and enhanced air quality favor the climate-friendly credentials of solar panels.

In conclusion, although solar roadways offer several benefits, their use will be restricted in the future and they will only be favored in specific circumstances. This is primarily because of some of the difficulties associated with solar roadways and the simplicity of implementing other eco-friendly technologies. However, future innovations and breakthroughs in the area could propel it to be a viable option. Other interesting options are also gaining attention, like installing solar panels along the side of highways or as roofs over the highways. 

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