For more power, double the function of infrastructure

Wind power is a promising form of renewable energy, but building wind farms to harness it can involve a wide geographic footprint and a big environmental impact. Now a team of engineers from Spain and the UK has looked at the problem from a different direction and says maybe we’ve already built wind farms – we just need to install the turbines.

For example, they say, how about generating electricity from the wind that whistles beneath bridges and viaducts? As a test case, the team calculated the potential of installing wind turbines under the Juncal Viaduct, on the island of Gran Canaria. The 63-meter-high bridge is part of a roadway connecting important towns on the north side of the island, which is in Spain’s Canary Islands archipelago. Sitting in the path of reliable Trade Winds blowing from the East, the archipelago is a promising spot for wind energy development.

In a paper appearing the current issue of Renewable and Sustainable Energy Reviews, the researchers consider the possibilities of installing turbines in four different configurations underneath the bridge’s 250-meter span: one big turbine; a big one and a smaller one; two medium-sized ones; or a grid of 24 small turbines.

They entered values for variables literally from A (rotor surface, in square meters) to z (height, in meters) into a computer model and used a method called computational fluid dynamics to calculate the power generating potential of these arrangements.

The best choice for the Juncal Viaduct, balancing power with practical concerns of cost and feasibility, would be to install two medium-sized turbines side by side, the researchers say. According to the model, this arrangement would generate enough power to meet the annual power needs of 400 to 500 homes.

That’s a relatively modest total, but consider how many other bridges and viaducts are around – the Juncal Viaduct is said to have “medium” wind power potential – and the total could add up to something significant.

The study is part of a larger project by a Canarian company, ZESCA, investigating the use of public infrastructure to boost production of renewable energy. The strategy could be useful in protected areas where construction of new infrastructure is prohibited, as well as in built-up areas like cities, the researchers say.

Though the turbulent eddies of airflow around city buildings can be a challenge for wind power development, in recent years some buildings have been designed to incorporate the technology. Integrated wind turbines in the Bahrain World Trade Center produce about 11 to 13 percent of the building’s power needs. The Strata building, a 43-storey apartment tower in London, has three wind turbines that cover about 10 percent of its power needs.

So embedding wind energy technology into other infrastructure isn’t a new idea, and yet it’s a deeply appealing one. If we could make the structures we build do double duty, we might reduce our species’ footprint on the planet, at least from a physical perspective – and if renewable energy is involved, it would mean reducing our carbon footprint too. – Sarah DeWeerdt | 21 July 2015

Source: Soto Hernández Ó. et al. 2015 Power output of a wind turbine installed in an already existing viaduct. Renewable and Sustainable Energy Reviews DOI: 10.1016/j.rser.2015.03.097

Header image:  An illustration of two wind turbines installed in a viaduct. Credit: José Antonio Peñas (Sinc).