Piezoelectricity could help Californian roads to generate clean ‘crystal’ energy

With almost 30,000,000 registered drivers in California, the state’s extensive road network caters to millions of drivers every day. But the California Energy Commission (CEC) and the California Institute of Technology have seen an opportunity.

The two organisations are planning to make use of the kinetic energy of cars travelling over road surfaces, by embedding piezoelectric materials into the road surface, according to a recent report published by the BBC.

Aerial view of the Golden State 5 and 118 freeway interchange in

Piezoelectric materials are those which generate electrical current when flexed or subjected to stress: known as the ‘piezoelectric effect’. The material generates an alternating current voltage when put under pressure or vibrated, and the most common material used is quartz – hence the nickname, ‘crystal energy’. The technology is currently being used in small-scale applications, such as the WATT nightclub in Rotterdam, but it also offers the exciting potential for large-scale application.

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Piezoelectricity has been recognised as a new and innovative way to cleanly generate energy, and in California could become just the latest installation in an already impressive portfolio of renewable technologies.

The project began late in the summer of 2016, with the California Energy Commission (CEC) making available a $2m research grant for lab tests to establish the efficacy of piezoelectric materials under road surfaces.

Universities and businesses tendered for the contract; the California Institute of Technology was awarded the grant, “to investigate the energy recovery potential” of roadway piezoelectric systems, and to demonstrate “in the laboratory and on a section of road, the high capacity of electric power generation and [to] determine feasibility for future largescale demonstrations on highways.”

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There has already been some preliminary research carried out to establish the feasibility of piezoelectricity. Rex Garland, a student at Stanford University in 2012, produced a report examining the costs and practicalities of installing a piezoelectric grid across the states’ road network.

Additionally, the CEC released its own report in 2014 examining generation capacity, durability and lifetime costs of the system.

Both of these reports found that the costs and generation capacity of piezoelectric materials limited the usefulness of the technology. However, other recent research has been carried out to determine the ways in which piezoelectric materials can be made more efficient by changing the structure of the device itself.

Research like this is helping to drive understanding and improvement of piezoelectric materials; equally, products such as Wattway from the French company Colas are driving innovation and helping to make renewable technologies integrational with traditional infrastructures.

California is aiming to generate a minimum of 33% of its energy demand from renewable technologies by 2020, and 50% by 2030. The CEC estimates that “about 27%” of electricity supplied in 2016 came from renewable sources.  With further innovation research – and given the state’s progress so far – California will soon reach its target.

A few states over, piezoelectric technology is being used in an entirely different way to explore low-carbon energy generation. Read all about these scientists’ nature-inspired method of harvesting ‘crystal’ energy.

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