future view

Unique noise barrier generates energy on both sides

18 February 2019 • 4 min reading time

Since mid-February, an innovative noise barrier can be admired along the A50 near Uden. A world first, because the barrier not only blocks noise, but also generates solar energy on both sides. To this end, double-sided solar cells have been integrated into the four-hundred metre long and five-metre high noise-proof structure.

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Solar Highways
“The idea of double-sided solar panels in noise barriers has been around for some time. Now, for the first time, we have succeeded in devising and building a structure that optimally combines the functions of blocking noise and generating energy," says Professor Wim Sinke, principal solar energy researcher at ECN part of TNO and part-time Professor of Photovoltaic Conversion at the University of Amsterdam.

Vertical position

The special thing about the construction is the fact that the solar cells are actually integrated in the noise barrier and have not been added to it. The vertical position also makes it possible not only to block the noise well, but also to capture a lot of light on both sides and thus generate electricity. Moreover, it no longer matters in which direction the motorway runs: east-west, north-south, diagonal and with all the bends in between. The sum of the yields at the front and back is virtually independent of the orientation of the panel.
"We have made a design that not only delivers high efficiency but with a similar front and back so that the cell can work on both sides."

Little space, high efficiency

For Wim Sinke, this innovation is a logical outcome of intensive collaboration between applied science and industry in our country. "We have been working together for a long time on high-efficiency solar cells and panels, in this case silicon. We are constantly trying to make them more efficient and cheaper. For decades they could only capture sunlight at the front; the back was simply closed. Now we have made a design that not only delivers high efficiency but with a similar front and back so that the cell can work on both sides. Vertical positioning opens up a whole range of possibilities, such as solar panels featuring greenery where you can grow crops between rows or do other useful things. Thanks to this position, they hardly take up any space.”

Uniquely positioned

The Netherlands is participating as one of the global leaders in this development. In few countries is there such strong cooperation between knowledge institutions, such as TNO, active players in the application of solar energy and innovative manufacturers. This gives unique opportunities to develop and use new types of systems based on advanced technology. We should also use this position to manufacture and install the new generation of noise barriers and all kinds of other integrated solar energy applications.

Technological challenges

Rijkswaterstaat is the initiator and client of the Solar Highways project. ECN part of TNO developed the prototype and Heijmans built the barrier. One of the technological challenges for TNO was to ensure that sunlight on both sides can reach the solar cells easily.

"We had to make sure that the shadow that you always have at a certain position or exposure has a minimal effect on the yield of the solar cells. In itself that could be done, but it also had to work in a heavy structure like a barrier designed primarily for another purpose. Rijkswaterstaat’s requirements for blocking noise, safety, robustness and longevity are demanding, and solar energy generation had to comply. And that's what happened.”

thinking big

When will the trial have succeeded? The barrier now in place should generate energy for about fifty households. How many barriers need to be installed along the motorway to make a substantial contribution to a sustainable energy system?

Wim Sinke: "With solar energy you have to think big. That means using as much existing surface area as possible: facades, roofs, road surface, barriers along the motorway, etc... Otherwise, we won’t be able to make the difference. So for this application preferably tens or even hundreds of kilometres of motorway as part of the sustainable energy mix. It's everything and more.”

"Only then can sustainably generated electricity become the fuel of the future"

Blurred roles

This kind of integrated application does not only require new technology, but also a different organisation and division of roles, he thinks. Traditionally, energy companies supply energy and road authorities such as Rijkswaterstaat provide roads. This division of roles is becoming blurred and other public and private parties may wish to participate. This raises questions about investments, returns, ownership and responsibilities. New business models are emerging in public-private partnerships.
"And if we want to use renewable energy on a large scale, we need to resolve public issues about the spatial integration of all those solar panels and wind turbines. Only then can sustainably generated electricity become the fuel of the future."

Rijkswaterstaat: proef geslaagd

“The potential of this type of noise barrier for generating green electricity is indeed enormous," says Dirk van der Graaf, project manager Solar Highways at Rijkswaterstaat. " Such barriers enable us to make a substantial contribution to sustainable energy generation. As far as we are concerned, the test has already been successful: the test barrier is there and generates energy. Thanks to the inventiveness of ECN part of TNO, we are no longer bound by southward orientation to the Sun, but can generate energy in all directions. The possibilities are therefore even greater. In the coming period we will gain experience with maintenance and operation. Based on these experiences we can make plans for a further rollout. All in all, we should be able to generate the output of a small power station along the motorways."

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Solar Highways

Solar Highways
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