Are solar roads the answer to the world’s energy and environmental woes? How practical and useful is their technology right now? And do they have a future in our sunburnt country?
Check the social media reaction around various announcements about solar roads and the first thing you’ll notice is a chorus of support, a groundswell of shares and likes, blogs and re-tweets. The all-encompassing reaction to new solar road developments, pilots and research projects is loud and proud.
Next, though, you’ll read a few articles by those who are knowledgeable in the field of solar power. Although highly respectful of anything that involves and promotes photovoltaics (PV), these experts sensibly and sometimes humorously warn against becoming too excited about solar roads. Outside of being a powerful PR function for the solar industry, they say, solar roads are unlikely to become a future energy solution.
In fact, depending on who you’re talking to, solar roads range from being impractical to overly expensive to downright dangerous to completely absurd.
“There is a psychological component to the solar roads that makes them attractive,” said Dr Andrew Thomson, a research fellow within the Research School of Engineering at the Australian National University.
“Solar roads get a huge social media following with thousands of people commenting. These are likely all people who feel bad about global warming and pollution. They are often educated and are productive members of society, and you have to use a road if you are a productive member of society.
“This means they feel a little bit guilty. In fact, we all feel a little bit guilty about using roads. So the solar roads idea makes perfect sense. Why not turn all of these roads into beautiful solar power generators? That way we can feel good about using roads. I really do think the popularity of the idea comes down to that.”
But money and support is pouring into the solar roads industry. Scott and Julie Brusaw, who 10 years ago launched their business Solar Roadways in the US, have been followed by a documentary crew, welcomed into meetings with Senators and Congresspeople, and have received almost US$4 million in funding from the Department of Transportation and from an Indiegogo crowdfunding campaign.
There must be something behind the science to generate that much support. But what? And when the three major solar road projects are in the US, France and the Netherlands, why isn’t our own sunburnt country experimenting with such innovation?
“As much as I can see their faults, I actually think the idea of solar roads is very cool,” Thomson said.
“The entire experiment is awesome. Anything creating solar electricity, in principle, is a good idea. At the same time, it is eating away at the limited capital available to renewable energy research and development.
“Why isn’t it happening in Australia? Because solar roads make no economic sense and our country tends to be run by economists, not engineers. If you can’t make something make economic sense in Australia, it is really hard to float it. That’s a shame. When you are researching things, they shouldn’t necessarily make financial sense. You need to be exploring the unknown.”
Solar roads: What we know
One of the researchers leading the solar roads charge right now is Sten de Wit, innovator and spokesperson for SolaRoad, a Dutch project involving solar cells embedded in a cycle path.
Although it is still very much a pilot project, SolaRoad is exciting, de Wit said, for its potential future capabilities. His vision for solar roads involves the provision of energy to the very vehicles that travel upon them.
“With SolaRoad, our road networks can develop into large scale, decentralised sources of green electricity,” he said.
“Imagine that we can harvest solar electricity from the road, and use that energy to power electric cars driving over these roads. We would be a huge step towards an energy neutral mobility system, and use the energy where it is produced. By combining rapidly-developing technologies in charging solutions for electric vehicles with SolaRoad, this future might be closer than we now imagine.”
Each concrete SolaRoad element of 2.7 m x 3.5 m contains two solar modules, de Wit said. Each module has its own solar power optimiser to make sure the yield remains optimal, for example under partial shading. Separate cabling collects the electricity from the solar panels and transports it to a substation, where it is coupled into the electricity grid.
The solar panels themselves are similar to those you would have installed on your roof. The innovation comes in the casing, or coating, of those panels.
“An important difference is the top layer of the panels,” he said.
“We developed a skid resistant, durable, transparent and dirt-repellent coating, which makes sure that the road surface is safe for use by bike traffic under all weather conditions, yet allows sunlight to reach the cells embedded in the road.”
The road elements are placed at a slight tilt so most of the dirt washes off during rain showers. That seems to have worked. De Wit said electricity production over the first year of the pilot was “somewhat higher than we had expected”, and that was without any cleaning.
While the cost of building solar roads far exceeds the costs of traditional roads – the SolaRoad bike path, measuring 72 m in length, has so far soaked up almost $5.6 million – de Wit says he expects that in four to five years the project will be at a point where the total cost of ownership should be comparable to regular roads.
So what’s the problem?
Max Sylvester is a co-founder of Energy Matters, an award-winning business that has been responsible for installing more than 20,000 solar panel systems on various buildings. It is an organisation that is single-minded in its pursuit of everything solar, but Sylvester is not convinced about the practical value of the solar road offering.
“We put a story about the French solar road project on our website and it was by far the most popular story for that month,” Sylvester said.
“In terms of generating public interest, the solar road experiments are incredibly popular, and that is a good thing. Getting solar out there and making people aware of it is great, but in terms of bang for your buck, solar roads are not the best idea.”
He said when manufacturers stack solar panels in their warehouses, they can only stack them to a certain level to avoid micro-fractures.
“Imagine then putting them on a road and having trucks drive over them; I’m imagining there are going to be some maintenance issues,” he said.
Thomson agreed one of the biggest problem areas is going to be around safety.
“If you have one exposed wire, one cracked or faulty solar panel, and it happens in a way that the inverter does not shut down, you potentially have 1000 V that can supply 9 A of current, which is more than enough to kill anybody,” he said.
And what happens when a road needs to be repaired or dug up for any other reason, Thomson asked, and all of that technology and electricity is added into the mix?
Heat is another issue. Solar panels are typically rated at 25°C, and the cooler the better. For every degree above 25°C, a panel loses about half a per cent in performance. Road temperatures in Australia regularly reach 50°C, so a large percentage of operating efficiency is going to be lost.
If solar roads were to become a reality, inverters would need to be placed every 50 m along those roads to convert the DC current to AC, Thomson said. Then the power would need to be fed into the grid at various intervals, requiring further infrastructure and, therefore, further expense.
Finally, both Sylvester and Thomson agree we already have a proven, relatively inexpensive, highly efficient and effective solar option available in the form of roof panels.
“Solar panels are extremely well optimised to work the way they do when they are attached to a roof,” Thomson said.
“And they are cheap because of economies of scale. A solar panel on your roof is a beautiful thing because it requires no ancillary services. It is so simple, and it requires zero maintenance for 20 years. We have a fantastic solution that works and is cost effective right now. Why make it more complicated?”