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 bike path in Krommenie is the practical realization worldwide. Here, a 100-meter cycle is built in 2014, which generates electricity using built-in solar cells. We are working with other parties to realize more pilot applications like 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.

The idea for SolaRoad was born at TNO. The Province of Noord-Holland, Ooms Civiel and Imtech have joined to develop SolaRoad. Together they form a consortium.
Quotes and photos from all parties you can find under People.

We are always open to parties wishing to contribute to SolaRoad with specific expertise or (financial) resources.

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.

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.

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.

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.

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.

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 results of the 3-year pilot in Krommenie will be published at the end of 2017/beginning of 2018.

So far, this is what we have measured:
Estimated energy production in lab-phase:
50-70 kWh per m2 per year

Production year 1 (nov 2014- oct 2015):
9800 kWh / >70 kWh per m2 per year

Production year 2 (nov 2015 – oct 2016):
7700 kWh / 63 kWh per m2 per year

Production year 3 (nov 2016 – oct 2017):
Not known yet

SolaRoad is a new concept for the generation of sustainable energy. Here, the road surface also acts as a solar panel. The generated electrical energy can be used for various applications, such as road lighting and traffic systems. Households may benefit from it as well. In time, electric cars might possibly be able to make use of the energy. The energy will then actually be generated at the place where it is needed: this is a big step towards an energy-neutral mobility system.

The idea for SolaRoad was born at TNO. The Province of Noord-Holland, Ooms Civiel and Imtech have joined to develop SolaRoad. Together they form a consortium.

A solar cycle path is an application of SolaRoad in a cycle path. In other words, it is a cycle path that absorbs solar energy and converts it into electrical energy.

The SolaRoad cycle path will be safe, comfortable and sustainable. We realize this with several technical solutions:

Skid resistant road surface

The surface of the SolaRoad cycle path consists of a layer safety glass with a skid resistant coating on it. The coating ensures that the road users have sufficient grip and are able to safely drive and walk on it. In the laboratory the skid resistance of the road surface is being tested. The skid resistance may not be lower than that of a normal cycle path, not even in the long run.

Strong road surface

Special attention is paid to the strength of the road surface. The tempered glass in the top layer and the solar cells underneath are applied in such a way that they can withstand everyday use. Not only cyclists must be able to ride on it, but for example service vehicles as well. In addition, shock loads of falling objects should be taken into account. Influences from the environment (heat, cold, salt, …) must not cause any problems. These aspects are being examined in the laboratory using various mechanical and thermal tests.

Comfortable road surface

SolaRoad consists of prefabricated elements, which are placed end to end to form a cycle path. In order to achieve a good riding comfort for the cyclists, the elements are interconnected to one another. This link ensures that no height differences can arise at the transitions between the elements. The road construction is designed to avoid damage from in the soil underneath, or from expansion and contraction due to temperature changes.

It is not either-or, but both-and. The total electricity consumption in the Netherlands lays around 110,000 GWh and increases annually by about 3% (according to CBS Netherlands). This means that if all suitable roofs in the Netherlands would be equipped with solar panels, they could only supply approximately 25% of the Dutch electricity demand. In order to reach a larger share of solar energy, a larger surface area of solar panels is required and therefore alternative types of solar cell applications than only rooftops must be found. In this regard, roads are an interesting option. 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, a great potential has come into existence, creating a complementary market for solar panels.

A cycle path is more practical as a pilot site (than for example a highway) for various reasons. A cycle path is less heavily loaded, because the means of transport that use it are lighter. It is also easier on a cycle path to make any possible adjustments and to implement improvements. This way, we can learn and develop faster. In addition, a cycle path is a typically Dutch product.

The pilot location in Krommenie meets several important criteria. It is a separate cycle path with free space on both sides. This is important in order to be able to make measurements next to and around the cycle path easily and to make any possible adjustments or improvements. In addition, the cycle path is located conveniently with respect to the sun. The path is intensively used, so that the influence of the use can properly be monitored. Also, the location is easily accessible by both car and train, the cycle path is under the control of the Province Noord-Holland and the current asphalt surface is to be replaced soon. Finally, we prefer working with an enthusiastic and progressive community that is engaged in renewable energy. This is how we ended up in Zaanstad. These arguments together make the selected cycle path in Krommenie a suitable location.

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 programme 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.

SolaRoad welcomes Wattway and other initiatives that use the road’s surface as solar panel. It’s good to see that what SolaRoad started in 2009, now has worldwide following. There is an emerging market for solar roads that is now being developed by more players.

Since 2014, SolaRoad has been gathering experience with solar panels on the public bike path in Krommenie. Much has been learned and that expertise is incorporated in an update of the product, which lies on the road since October 2016. SolaRoad therefore has a track record. The new initiatives are still at the beginning of the learning curve of the practical implementation of solar road surfaces. Also, SolaRoad is now commercially available in the form of the SolaRoad kit. (Available since the end of 2016). Follow-up projects on bike paths and regular road surfaces, in the Netherlands and in the US, are scheduled starting 2017.

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.

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.

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.

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.

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.

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.

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.

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).

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.

The main design requirement that is imposed on SolaRoad is that it meets the requirements regarding safety that apply to regular pavement.

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.

No, the electrical components are shielded very well. Moreover, the voltage per element is low.