Climate change and global warming are among the major concerns of the contemporary world. They are mainly caused by the release of greenhouse gases from fossil fuels. Roads also contribute to the emission of greenhouse gases from their construction to operation. Solar roads had been fronted as an innovation that could help reduce emissions from roads since the mid-2000s. However, the innovation has not been significantly implemented or improved globally in the past decade. As it would assist in producing renewable energy, solar roads should still be considered among the most practical innovations to greenhouse emission targets in highway construction.
Infrastructure projects are also significant emitters of greenhouse gases that cause global warming and climate change. The transportation sector contributes to approximately 31% of the carbon dioxide (Ma et al., 2016). Considerable amounts of carbon dioxide are also produced when constructing infrastructure. For instance, common road construction uses asphalt pavement methods, which is a petroleum product (Kermeliotis, 2014). Extraction and use of fossil fuels such as petroleum are the major emitters of greenhouse gases. According to Ma et al. (2016), the construction of roads in China using asphalt produces a significant amount of greenhouse gases. In their analysis, they concluded that the total amount of carbon dioxide equivalent emitted from the construction of a 20 km asphalt road was 52,264,916.06 kg. Consequently, innovation in infrastructure construction is needed to mitigate the negative effects of conventional road construction. Solar roads are one of the innovations that could considerably reduce the greenhouse gas contribution from the highway and transport industry.
The basic idea of making a solar road lies in using the road network to generate electricity. The roads would use the photovoltaic technology to convert solar radiation into electricity. The overall goal would be to replace the entire roads and parking area networks using solar roads. The electricity produced by the road could be added to the grid to reduce the dependency of fossil fuels such as coal.
The solar road would consist of a couple of layers. The road surface layer would be at the top is made with a high strength textured glass which is translucent. The glass would have enough roughness to provide friction and translucent enough to allow light to pass through. Moreover, the road surface layer is strong enough to protect the various electronics components below it. Other components of the layer include LED and heating elements. Following the road, the surface layer is the electronics/optical layer that would contain microprocessors that control the various functions of the road including heating, lighting, and monitoring. However, the primary purpose of the electronic layer is to collect solar energy through the photovoltaic cells. Finally, the base layer distributes the power generated to homes and connects the intelligent road to data signals (Mehta et al., 2015). Figure 1 shows a diagrammatic representation of the solar road.
Figure 1: The major components of the solar road (Civil Engineering Seminar, n.d).
The idea of the solar road has caught the attention of various companies and individuals. Among the most known companies championing the technology is a US-based start-up called Solar Roadways that is a start-up by the couple Scott and Julie Brusaw (Mehta et al., 2015). It successfully raised US$ 2.2 million in an Indiegogo campaign called “Solar Freaking’ Roadways!” In France, a company called Wattway had successfully built a one-kilometre solar road at the cost of US$ 5.2 million and has the capacity to supply 280 megawatts of power (John, 2015). Other companies with the solar road technology include SolaRoad and Hejimans of Netherlands (Scheffe, 2016). The fact that the technology of photovoltaic cells is becoming cheaper and the threats caused by climate change make the innovation attractive for investors.
The main advantage of solar roads is that it would be able to generate electricity from renewable resources. Mehta et al. (2015) claim that the use of solar roads has the potential of enabling a decrease in the dependency on fossil fuels. It has been established that the amounts of fossil fuels reserves are reducing and the roads are durable. Scheffe (2016) reports various structural analysis tests to indicate that the roads would be strong enough to withstand the loads supplied by the daily traffics. Solar Roadways (2018) claim that solar roads could last up to 20 years compared to asphalt roads that have a lifespan of between 7 and 12 years.
There are vast opportunities that could emanate from solar roads. For instance, Patel (2018) reports that China was able to launch its solar highway at Shangdon in 2018, which covered a total of 5,875 feet squared. The project proponents claim that the road has the capacity of producing 1 gigawatt of power that could power the streetlights and melt the snow in winter. There is also a possibility of the power being used to generate electricity that could be used to power electric cars. Solar Roadways (2018) also state that the road would not require painting and could protect animals among other benefits (Figure 2)
Figure 2: Benefits of solar roads when compared to concrete and asphalt roads (Source: Solar Roadways, 2018)
One of the biggest challenges for more solar panels is that it would require additional land. The situation is averted with solar roads, as road networks are already extensive on the surface of the earth. According to Hornigold (2018), road networks already cover between 0.2-0.6 percent of the earth’s land surface. If all were converted into solar roads in the United States, they would generate enough electricity to meet the country’s demand. Establishing solar roads on the existing road networks would have minimal effects on the environment. Further, it would be convenient to undertake repairs and maintenance on the roads as they could be accessed with ease.
Although it might be convenient to repair solar roads, the costs of constructing the road are high. For instance, Patel (2018) reports it cost US$ 458 per square meter to construct the road at Shangdon. This compared to the US$ 5 per square meter that is required for the asphalt road. Brusaw’s cost of approximately US$ 750 for each square meter for the construction of the solar road in America is even higher (Hornigold, 2018). Furthermore, maintenance would be more frequent on the solar roads. According to Mehta et al. (2015), it is likely that the road surface would accumulate particles such as soil, rubber, and other substances that would block the panels. Thus, the road would require frequent cleaning, which is costly.
Solar panels work best when full sun is available. However, Mehta et al. (2015) claim the sun is not always available in many countries all year round. This implies that the panels will have difficulty in attaining their optimal energy production levels. Moreover, the existing pilot projects have been characterised by widespread inefficiencies. For instance, John (2018) reported that the pilot 1 km solar road in France only managed to produce an average of 409-kilowatt hours a day in its first year against the projected 767-kilowatt-hour a day. Similarly, when Solar Roadways opened its first project in Idaho in 2016, there were concerns that most of the panels were not working and they would consume virtually the entire electricity produced to generate heat and light their LED. Moreover, solar installations need to be done at an angle for maximum efficiency, which may be impossible in roads. Patel (2018) also states that shading from buildings and trees affect the efficiency levels of solar.
The basic premise of solar road technology is that it could be used to generate renewable energy. Other technologies could be used to generate electricity from the road. For instance, Jiang et al. (2017) propose a thermoelectric system that generates power using the asphalt road surface. It is observed that there exists a temperature difference between the asphalt road surface and the adjacent areas. Consequently, Jiang et al. (2017) developed the road thermoelectric generator system (RTEGS) based on the difference between the road surface and the ambient air. Their experimental tests showed that a road, which is 1 kilometer long and 10 meters long, could generate approximately 160Kwh of power.
Although the thermoelectric generator system (RTEGS) are less efficient compared to the solar road technologies, it has some merits. Jiang et al. (2017) state that thermal energy in the pavement could be directly converted into electricity from the existing asphalt roads without the need to change the road materials and structures. Furthermore, the technology could also assist in reducing the heat island effect as compared to the solar road technology that could increase the heat island effect. Another technology for generating electricity from roads is the piezoelectric technology that involves embedding piezoelectric material that can convert the tyre-road friction into electricity.
The first recommendation arises from the necessity of technology. Solar roads are a feasible technological innovation that should be improved to allow for a greater mix of renewable resources. As fossil fuels reserves are dwindling, it would be important for stakeholders to support innovations for alternative sources for energy. The technology could only make sense if it is affordable. Consequently, organisations such as Solar Roadways should be supported in their research and design to make the cost of producing a meter squared of the solar road less than US$ 100. It should be noted that unlike concrete and asphalt roads, solar roads also provide additional benefits such as electric power and intelligent services.
Secondly, the safety of solar roads needs to be reinforced. While lab tests have shown that the roads have the structural integrity to match concrete and asphalt roads, practical tests would be necessary. Besides, it is difficult for lab tests to simulate weather events and natural disasters. Similarly, it should also be investigated if the driving experience on the solar roads would be similar to other surfaces. If not, provision for specialised driving lessons could be explored.
Third, governments and the international community should increase their support to the technology since it could only improve if it gains widespread implementation. One way the government could spur the popularity of the technology is via government policy. For instance, it could be made mandatory for some residences to have the solar road technology in some areas such as the parking space or the front porch.
Despite being conceived around a decade ago, the solar road innovation has not been implemented to full scale. Various pilots projects established in France, the Netherlands, the USA and most recently China have demonstrated that it is possible to generate electricity from solar roads. While it is not impossible to construct the roads, queries are made of the practicability of using solar roads. Apart from being inefficient, the cost of constructing and maintaining solar roads is high. Moreover, it is also questionable if the roads are entirely safe for heavy vehicular usage.
Notwithstanding the challenges, there is an urgent need to develop the innovation of solar roads further. Evidence shows the continuous use of fossil fuels has led to emerging issues of global warming and climate change. Therefore, adoption of technologies such as the solar road on a wide scale could significantly reduce the amount of greenhouse gases produced by the earth among other benefits to the environment.
Jiang, W., Yuan, D., Xu, S., Hu, H., Xiao, J., Sha, A. and Huang, Y., 2017. Energy harvesting from asphalt pavement using thermoelectric technology. Applied Energy, 205, pp.941-950.
John, J., 2018. Solar Roadways Prove Expensive and Inefficient. [online]Available at: <https://www.greentechmedia.com/articles/read/solar-roadways-are-expensive-and-inefficient#gs.q8_QSiU> [Accessed 26 Nov. 2018].
Hornigold, T., 2018. Are Solar Roads the Highway of the Future, or a Road to Nowhere? [online]Available at: <https://singularityhub.com/2018/01/15/are-solar-roads-the-highway-of-the-future-or-a-road-to-nowhere/#sm.00016862upsfvfbswyl1imsnfxg4x>[Accessed 26 Nov. 2018].
Kermeliotis, T., 2014. Solar-powered roads: Coming to a highway near you. [online]Cable News. Available at: <http://edition.cnn.com/2014/05/12/tech/solar-powered-roads-coming-highway/index.html>[Accessed 26 Nov. 2018].
Ma, F., Sha, A., Lin, R., Huang, Y. and Wang, C., 2016. Greenhouse gas emissions from asphalt pavement construction: A case study in China. International journal of environmental research and public health, 13(3), p.351.
Mehta, A., Aggrawal, N. and Tiwari, A., 2015. Solar Roadways-The future of roadways. International Advanced Research Journal in Science, Engineering and Technology (IARJSET), 2.
Patel, N., 2018. What Is the Point of a Solar Road? [online]Available at: <https://slate.com/technology/2017/12/solar-roads-are-almost-definitely-not-the-future.html>[Accessed 26 Nov. 2018].
Scheffe, J., 2016. Integrated solar lighting for pedestrian crosswalk visibility. [online]Available at: <https://rosap.ntl.bts.gov/view/dot/31671>[Accessed 26 Nov. 2018].
Civil Engineering Seminar, n.d. Solar paneled road [online]Available at: < http://civilenggseminar.blogspot.com/2016/06/solar-paneled-road.html>[Accessed 26 Nov. 2018].
Solar Roadways, 2018. Welcome to Solar Roadways [online]Available at: < http://www.solarroadways.com/>[Accessed 26 Nov. 2018].
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