Harnessing the power of sunlight - street by street

Swedish architect Måns Tham's Solar Serpents project seeks to harness solar power via existing road networks. Rowan watt-Pringle speaks to the architect to find out more about the potential for creating complex urban networks powered by the existing road infrastructure.


The Solar Serpent: A better use of existing space

"Måns Tham, of Måns Tham Architect & Urban Strategist in Stockholm, Sweden, proposes utilising the unused space above a road's surface."

Måns Tham, of Måns Tham Architect & Urban Strategist in Stockholm, Sweden, proposes utilising the unused space above a road's surface by building a tunnel of photovoltaic cell panels, through which traffic passes. The vast areas covered by roads in developed nations offer a practical alternative to the strategy of building sprawling solar farms in remote, arid areas.

Tham asserts that, because the issue of space will be of increasing importance as populations around the world continue to grow, the solar serpent concept will quickly garner international popularity.

"Countries in southern Europe have already shown a great deal of interest in the idea (of the solar serpent). Although the project is still in the conceptual phase, it is of course applicable anywhere in the world where the sun shines and land is expensive."

Tham has proposed a 24-kilometre section of the Santa Monica Freeway in Los Angeles as a possible location for solar serpent operations.

The average width of the freeway is about 130 feet (about 40 m), meaning the area could support a substantial 960,000m² of photovoltaic panels, producing sustainable energy to supply power to neighbouring areas.

According to Tham, an installation this size would be able to produce 150 Gigawatt-hours of energy annually, enough to supply power to every home in a sizeable neighbourhood.

An integrated, sustainable power grid

The solar serpent concept is not intended as a stand-alone power-generation solution, however.

The design allows for electric vehicle (EV) 'charge points' to be integrated into the system, as well as offering several other environmental benefits, such as reducing noise pollution and slowing surface deterioration from UV rays.

The tunnels would also shade large areas of road, lessening the need to use energy-intensive air-conditioning and hence lowering the harmful greenhouse gas emissions.

When asked whether the idea is likely to meet with resistance in some circles, Tham takes the possibility in his stride: "All major urban schemes are bound to meet with resistance for any number of reasons - because the main concept is to use pre-existing land more efficiently, the effectiveness of these installations is a question of political willpower. The major strengths of the solar serpent speak for themselves. Locally-produced, sustainable electricity generation that simultaneously reduces noise and air pollution."

Complex urban systems for the future

Tham envisages the solar serpent concept as part of a widespread push towards more energy-conscious, integrated cities.

"There are now many creative ways to rethink energy production in urban contexts," he said.

"Tham envisages the solar serpent concept as part of a widespread push towards more energy-conscious, integrated cities."

"This is no coincidence. I believe that all of these various paths towards more complex cities will result in a rich variety of energy production installations, which will be better adjusted to their particular local conditions than is the case today."

One example of this system integration, according to Tham, could see a linked project extract the harmful carbon dioxide (CO2) emissions produced within the tunnel itself.

This gas would be used to feed algae ponds next to the road, promoting the local production of algal biofuels and creating new 'green' employment opportunities.

But don't expect to see solar serpents snaking through your city, supplying electric car powering stations and algae farms, just yet.

"While the proposed technology is available, it will still require many adjustments to the originally proposed concept to undertake widespread solar serpent installations, but this will also hopefully lead to further improvements in the overall design and hence increased benefits for both the environment and urban communities."

Solar roadways

While solar serpents do require additional infrastructure to be built and maintained, another technology being researched by Idaho-based Solar Roadways wants to turn the actual road you drive on into a power generation plant.

"Having successfully completed a Phase I Small Business Innovative Research (SBIR) contract with the Federal Highway Administration, we were awarded a follow-up Phase II contract in July," said electrical engineer Scott Brusaw, whose prototype Solar Road Panels could help revolutionise urban environments.

When asked his end view for this technology, Brusaw was typically bullish: "Having it installed on every hard surface under the sun, pun intended! We've had inquiries from all over the world - applications for roads, parking lots, driveways, bike paths, sports complexes, cemeteries, airports and more. You're right about the existing infrastructure, it's already taking up space."

Driving on sunshine

As the name suggests, the Solar Road Panels are solar panels that you can drive on. "They create clean renewable electricity - one of the ways that they pay for themselves. Since we have to invest in this infrastructure, why not do so with a paving material that can pay for itself?" said Brusaw.

"The surface is heated in northern climates, which prevents snow and ice accumulation, while embedded LEDs illuminate the road lines or parking spaces and can display verbiage or graphics for drivers, pedestrians or pilots."

Brusaw says Solar Roadways is designing a prototype lot at its facility in northern Idaho - capable of handling a 160,000-pound truck (twice the normal legal limit) - which will be monitored and tested year-round over the two years of the Phase II SBIR contract.

When quizzed about possible complications involved in maintaining this kind of infrastructure, Brusaw warned it is too early to pass judgement, as it hasn't yet been installed anywhere.

"I'm sure there will be maintenance issues, but these will replace, rather than add to, existing problems such as potholes, line repainting, snow removal and so on," he said.

Solar vs asphalt: Apples vs oranges

In terms of pricing, Brusaw claimed it is a mistake to compare the cost of Solar Roads to traditional asphalt roads. "We estimate that the Solar Road will cost about three times more than an asphalt road, but that's comparing apples to oranges. To compare apples to apples, you'd have to add power generation and distribution costs to your asphalt roads," he argued.

Immense potential

Practically, Brusaw believes it will be up to the individual state transport departments to implement the technology, so Solar Roadways plans to focus, initially at least, on parking lots and driveways. But Brusaw is quick to highlight the immense potential for this technology.

"Covering every road and parking lot in the US with Solar Road Panels could produce three times more electricity than we use as a nation - almost enough to power the entire world! It would also make EVs practical, since they could charge anywhere - even while driving, which in turn would make the internal combustion engine obsolete.

"Since roughly 50% of greenhouse gases (GHGs) come from burning fossil fuels to create electricity, while another 25% comes from internal combustion engines, the Solar Roadways have the potential ability to eliminate 75% of GHGs currently being dumped into our atmosphere," said Brusaw.

Energy from asphalt

"Dutch company Ooms Avenhorn Holding, meanwhile, has developed a system for extracting energy from asphalt via water."

Dutch company Ooms Avenhorn Holding, meanwhile, has developed a system for extracting energy from asphalt via water, to cool and heat roads and buildings in the vicinity. Chris Sullivan, MD of Material Edge, Ooms' UK representatives, explains heat and cold energy is transferred from water in pipes laid 40 to 50 mm below the road surface and stored in an underground aquifier or within rock to be used the following season.

"The heat or cold can be utilised in buildings through a heat exchanger, via underfloor heating pipes. The hot water - at about 14°C - enters the building, where it is boosted by the heat exchanger to heat the building. The remaining heat returns through the road, de-icing en route to storage in the ground for use in summer."

One drawback is the process does require certain conditions, such as a still aquifer or fractured rock, where heat can be stored long term for the following season. But in the right place it can offer substantial benefits.

"While the process does not generate electricity, air-conditioning is a huge electricity drain. Simply passing cold water through the walls and floors of a building, on the other hand, gives a gently cooling effect similar to that experienced in large buildings like cathedrals in hot countries," Sullivan said.

"Warming the road in winter and cooling it in summer - both processes using the exhausted energy from the water, once it has passed through the building - the life span of the road is increased significantly, by preventing cracking and rutting in winter and summer respectively."

The technology is already commercially available, as Sullivan pointed out "There are about 12 schemes in the Netherlands, ranging from airfields to viaducts, old people's homes and industrial estates, while we have three schemes in the UK, with more being investigated.

"The British schemes all involve private companies (including a doctor's surgery / health centre) using the system in car parks and access roads. While the take-up so far has been slow, the time will soon come for this type of system, with the advent of solar, thermal and other tariffs or grants," he concluded.