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Project

SolaRoad PV Bikeway (Netherlands)

Credits: ©2014 SolarRoad

SolaRoad is an experimental bikeway in The Netherlands that generates sustainable energy using solar panels in the roadway’s pavement surface. The big question is: can such a roadway be scaled up to provide a lot of electricity in the future - on not just bikeways, but automobile byways, too? The first stage of the trail was completed November 2014: a 70-meter (230 feet) stretch of cycle path connecting two suburbs of Amsterdam, with 30 additional meters added soon. The roadway consists of 8.2 x 11.5 foot (2.5 by 3.5 meters) prefabricated “sandwich” modules with a top one-centimeter layer of rugged, textured, tempered glass, over crystalline silicon solar cells photovoltaic cells, and a bottom layer of concrete. The modules are interconnected end-to-end to form the cycle path surface in a way that ensures no height differences at the transitions for ease of riding. The road construction is also designed to avoid damage from in the soil underneath, or from expansion and contraction due to temperature changes. The SolaRoad also sports a non-stick, skid-resistant coating, and is tilted slightly so that rain washes off dirt, mud, ice and snow which could adversely affect the effectiveness of the solar panels. Flat surfaces are not ideal for capturing sunlight for power generation, so the bike path solar cells are about 30 percent less efficient than if they were mounted on a typical solar installation tilted towards the sun.

 

Amsterdam Solar Bike Path CNN

A solar bike lane known as the SolaRoad connects the Amsterdam suburbs of Krommenie and Wormerveer in a 70-meter stretch of solar-powered roadway. ©2014 CNN

Even so, this could be a practical solution in The Netherlands. According to TNO, the total electricity consumption in the Netherlands is around 110,000 GWh and increases annually by about three percent. But all suitable roofs in the Netherlands -- if equipped with solar panels -- could only supply approximately 25 percent of the Dutch electricity demand. However, the approximately 140,000 km of roads in the Netherlands cover a total area of about 400-500 km2, which is significantly larger than the total suitable roof surface area. With the integration of solar cells in road infrastructure, there is a greater potential for creating a complementary market for solar panels. The Netherlands is a bike-friendly country, home to around 18 million bicycles and 21,748 miles of bike lanes. The GPS coordinates for the SolaRoad are: 52.493875, 4.767134

The roadway-generated electrical energy can be used for various applications, such as road lighting and traffic systems. In time, electric cars might possibly be able to make use of the energy. If the roadway concept works as intended, the energy generated can be utilized where it is needed along the roadway, instead of having to import energy that is generated elsewhere: this would contribute to an energy-neutral mobility system. Smart ICT (information and communications technology) applications will distribute the energy production on days with lots of sunshine as efficiently as possible, to compensate for days without or with less light.

SolaRoad is the brainchild of Dutch research institute TNO, and developed in collaboration with the Province of Noord-Holland, Ooms Civiel and Imtech. It will remain in situ while further research on the techniques and materials is conducted over a three-year period, and new developments in solar technology will be incorporated as are feasible.

The pilot location in Krommenie was chosen because it met several important criteria. It is a separate cycle path with free space on both sides, so that ongoing research measurements can be made next to and around the cycle path easily (only half the path is solar for ease of comparison). In addition, the cycle path is located conveniently with respect to the sun. The path is intensively used, so that the influence of the solar aspects of the path on its use can be properly monitored. Also, the location is easily accessible by both car and train. The bike path is under the control of the Province Noord-Holland and there were plans to replace the existing asphalt surface.

FAQs Answered by TNO

Why isn’t SolaRoad applied over the full width of the bicycle road? We aim at maximum efficiency in the process of learning and improving, using a combination of (lab) experiments, pilot testing and further development. This helps us to make the time to market as short as possible. In June we made the final decisions on the pilot-design. At that stage, we chose to use apply SolaRoad on only one lane of the bicycle road in Krommenie. This allows us to execute the planned research and monitoring program in full, while saving costs in the pilot. The extra money can be deployed for further development.

Moreover, the other lane on the bicycle road will be used for specific R&D to improve the transparent top layer. In a number of test sections in this lane, dedicated measurements will be carried out to evaluate various solutions for the top layer e.g. on pollution and wear. Loads and exposure are almost identical to the adjacent SolaRoad-lane. The test sections can easily be replaced, to support accelerated optimization of the top layer.

Technology

How will the generated energy be used? During the pilot, the generated electrical energy will be supplied to the electricity grid, just like most solar panels on rooftops. It is expected that the pilot cycle path of approximately 100 m will generate as much electricity as is used by 2-3 average households annually. When SolaRoad is going to be applied extensively, straightforward supply to the electricity grid will not be an optimal solution anymore. For example, smart ICT applications that help to distribute the energy production at peak times (lots of sun) and dip times (night) as efficiently as possible are needed then. This issue will be addressed in the pilot study as well.

How can the solar cells be protected against use (load and shock), environment (heat and cold) and vandalism? The solar cells are located between two sheets of tempered glass in a concrete housing. The results of the mechanical and thermal tests of the prototype show that the elements are able to withstand everyday use very well. The glass surface can also resist large impact loads. Damage caused by vandalism, however, can never be ruled out. We use safety glass. When this type of glass breaks, it will break in the form of a lot of small pieces. There will be no dangerous shards. Moreover, the glass remains in its place due to the coating on the surface and the frame. Thus, even when the glass is broken, it can still be safely walked and cycled on, until repair can take place.

How strong is the glass? We use tempered glass that is particularly strong and that is mounted in a concrete housing. The strength of the glass in the housing is being mechanically tested in different ways. For example, extreme traffic loads are simulated in a bench press, pressing different tyre types on the surface with great force. Also, we drop steel balls and bags with marbles of different sizes and from different heights on the SolaRoad surface, in order to test the resistance to impact loads. This is based on internationally recognized standards. In this way, we test whether the glass is safe for use in practice.

Do shards occur if the road breaks?

No, we make use of safety glass. When this type of glass breaks, it will break in the form of a lot of small pieces. There will be no dangerous shards. Moreover, the glass remains in its place due to the coating on the surface and the frame. Thus, even when the glass is broken, it can still be safely walked and cycled on, until repair can take place.

Will SolaRoad break due to tree roots that may grow under the road? The current version of SolaRoad has been tested in the laboratory on structural strength. A specific ‘tree root test’ was not possible, but the concrete elements are designed and produced in such a way that they will not break very easily. To prevent height differences at the transitions of the elements, we pay special attention to the way in which they are interconnected. When dealing with factors from the (natural) environment, we make full use of existing knowledge and experience with prefabricated slabs.

Is it possible to use existing solar cells or do they have to be adapted? If so, what are the costs? Technically, there is no need for special solar cells. In the pilot, we make use of standard silicon solar cells. Of course, the solar cell, the translucent surface and the other components must be adjusted to one another. We develop the SolaRoad concept in such a way that in time we can integrate other types of solar cells, for example thin-film solar cells. A decisive factor for the choice of the best solar cell technology is the economical assessment of costs versus benefit (revenues).

Performance

How do you deal with generating, using and storing energy/electricity? How do you deal with peak and dip demand? SolaRoad is an example of decentralized energy generation (in contrast to central generation in large power stations). We will develop ICT solutions to optimally distribute the energy from SolaRoad amongst applications, for example along the road (lighting, charging of electric bicycles) or to the energy grid. ICT systems help to smartly switch between roadside applications. The difference between the moment of generation and use is not unique for SolaRoad, but it plays a role with all forms of solar and wind energy. SolaRoad can therefore make use of techniques that already exist or that are being developed in parallel.

What happens when there is a traffic jam on SolaRoad? Traffic jams mean a heavier traffic load and lots of shade on the underlying road surface. The traffic load is not a problem. The shadows during a traffic jam will cause the energy yield to hold up locally for a short amount of time. However, for most of the roads, the amount of time that traffic jams occur is so short that we do not expect significant yield losses. On road sections where a lot of traffic jams occur, application of SolaRoad paving is less suitable. The exact influence of shading by road users is part of the pilot study.

 

Use

Is SolaRoad safe for cyclists and motorists? Does SolaRoad meet all requirements with respect to (traffic) safety? The main design requirement that is imposed on SolaRoad is that it meets the requirements regarding safety that apply to regular pavement.

What is the effect of a translucent cover layer on the vehicle/the user? How do we experience a road of glass? The coating on the road surface looks very similar to a regular road. As a result of the large light transmittance, the underlying solar cells will probably be slightly visible. It is expected that the road surface will lead to a positive and safe experience for road users, posing no obstacles for normal use. During the pilot this will be further investigated.

Do users suffer from reflection? The starting point for the SolaRoad design is that no more discomfort due to reflections may occur than with regular road surfaces. This is an important factor in the development of the top layer. In the laboratory, extended optical examinations are carried out, in which reflection is measured as well. During the pilot this aspect will also be monitored.

Is it possible for cyclists/users to get a current surge from the road? No, the electrical components are shielded very well. Moreover, the voltage per element is low.

Costs and revenues

What were the 3.5 million Euros used for? The €3.5 mln was invested by the various partners in the research and development process, which has so far taken five years. The test route in Krommenie represents just a small part of this. We consciously opted for an initial pilot involving a short length of cycle path and yielding only a small amount of energy (enough to power around three households). This is enough to generate a wealth of practical information while keeping pilot costs down so that we can allocate a larger part of the available funds to developing SolaRoad into a marketable product.

What are the costs per square metre? How do these costs compare to ordinary roads and cycle paths?

In the current development stage it is too early to make reliable statements about this. The starting point for the development is that the balance of costs and benefits of the life span is positive, compared to existing road surfaces. SolaRoad is being developed by a tripartite consortium of partners, in which industry, knowledge institutes and government join forces in order to innovate. The intention is that the product will soon become available on the open market and that an appropriate and healthy business model will be developed.

Is it economically feasible? The techno-economic feasibility study indicates that it is possible to achieve a return of investment within a life span of 20 years. A side note here is that the production, management and maintenance of this new type of road are yet to be optimized. Eventually, we are aiming for a payback period of 15 years or less.

Does SolaRoad have additional maintenance costs? How much? In the development of SolaRoad the starting point is that SolaRoad meets the same requirements as regular pavement types. In current studies, we assume regular maintenance regimes. According to expectations, an optimization can still be made, in which the maintenance of the technical systems will be integrated.

Can pollution of the road surface reduce the yield of SolaRoad? Pollution will certainly affect the amount of light that falls through the top layer. By making the top layer dirt repellent and by putting the road under a sufficient slope, we make sure that the effects of pollution as small as possible. The exact degree of pollution is not clear yet. Currently, we are performing experiments on this topic. The profits are expected to be lower than solar panels on rooftops. What the yield will be exactly is one of the research questions in the pilot.

Even the most optimistic scenarios foresee in 2030 not more than 10% share of electric vehicles. What is the use of such a road then? SolaRoad provides solar electricity, which can be used for vehicles that drive across/over it, but also for other energy users, such as street lighting, households, etc. The success of the transition to electric vehicles is therefore not a prerequisite for SolaRoad. In contrast, a large-scale application of SolaRoad may work as an enabler or incentive for electric mobility: together they may have a greater chance of success than separately.

The first results are known. What does the development process look like and what is still needed for this? For SolaRoad we are continuously developing knowledge and products in the field of engineering, material choice, energy distribution and (social) business model. Also the boundary conditions that are set from user perspective (safety, comfort) are further investigated. The next step in this process is the realization of a first practical application of SolaRoad in the form of a cycle path. Krommenie is going to be the first worldwide. Here, a 100-meter cycle path will be built in 2014, which will generate electricity using built-in solar cells. Knowledge and product development will be linked to the realization of this practice test.

Will SolaRoad be applied in highways as well? What should be done in order to do this? The next steps in the development and scaling up of SolaRoad will be (pilot) applications provided in smaller motorways (for example municipal roads) and in specific applications such as bus lines. Whether application onto highways will be possible in the future, cannot be assessed yet. For the potential of SolaRoad, application in highways is not necessary: of the 140,000 km of roads in the Netherlands approximately 90% consists of municipal roads. Highways cover only 5% of the road surface.

Why is it important for TNO to be involved in SolaRoad? TNO focuses on innovations to increase the sustainability of energy supply and infrastructure. The R&D-organization has responded to this with technologies that make fossil fuel extraction and use more efficient and cleaner and combines this with renewable energy sources. TNO develops knowledge and encourages innovations, in cooperation with companies and governments. A good example is SolaRoad, a road that generates electricity: sustainable and profitable.

Which parties will be involved as well? We are always open to parties wishing to contribute to SolaRoad with specific expertise or (financial) resources.

How can you get involved as a business, institution or government? Anyone interested in participating in SolaRoad should contact Gerrit Jan Valk from TNO (Gerritjan.Valk@tno.nl, +31 (0)6 53 54 80 30).

What is the position of the consortium compared to Solar Roadways from the U.S.A.? The SolaRoad consortium uses an approach that is comparable to that of Solar Roadways. The developments are at a similar stage: the stage of the prototype. There are differences too, for example in the technical details. Solar Roadways aims at the integration of many different features, which include making texts (STOP, SLOW DOWN) by means of LEDs in the road and the signalling of crossing pedestrians. We have chosen to focus entirely on the generation of electricity and only afterwards to consider the integration of other functions. This way, we are working as fast as possible towards a well-functioning and practically applicable solution.

What is the difference with heat extraction from asphalt (www.wegvandetoekomst.nl)? For heat extraction from roads commercially viable solutions exist. Road Energy Systems is a product of Ooms Civiel (partner in the consortium), consisting of water filled pipes that run through an asphalt road. The sun heats the road surface, the temperature of the water in the pipes increases, and the hot water is pumped out of the road. SolaRoad generates electricity using solar cells in a translucent road surface. The advantage of electricity is that it can be transported more easily and that it can be used for more purposes. In the future, both systems may possibly be combined.

Also see Starry Night Solar Bike Path in The Netherlands.


Documents

  SolaRoad Article (in Dutch) (305 kb)

  Solar Bike Path Amsterdam article 2014 (409 kb)

  Amsterdam Solar Bike Path article 2014 (335 kb)


Resources

SolaRoad (Netherlands)