Solar carpet between train tracks

The expansion of solar energy is on the fast track around the world. In 2025, new photovoltaic systems with around 630 gigawatts of power generation capacity are going to be installed, according to the “Global PV Outlook Report,” and by 2030 that capacity is supposed to have increased to as much as 880 gigawatts. However, in the analysts’ view, major untapped capacities will continue to exist as well.

Swiss startup Sun-Ways is planning to harness some of that potential by rolling out photovoltaic modules like a carpet between train tracks, either manually or automatically. The newly developed technology is supposed to make use of the previously unused space between the tracks without interfering with train traffic.

The special machine from Sun-Ways’ partner Scheuchzer AG, a pioneer in the field of railroad maintenance, can lay up 1,000 square meters (0.25 acres) of solar modules per day, plus, the solar system can be uninstalled quickly. For example, it can be removed completely or partially for maintenance work. Each module has a size of about 1 by 1.7 meters (3.2 by 5.6 feet).

In the fall of 2024, the Swiss Federal Office of Transport gave Sun-Ways’ plans the green light. Starting in the spring of 2025, a total of 48 solar collectors are supposed to be laid on a track section with a length of 100 meters (328 feet) in a pilot project in the canton of Neuchâtel. The system will be connected to the local power grid and is supposed to produce up to 16,000 kilowatt hours per year, about as much as eight two-person households consume per year.

In Switzerland alone with its roughly 5,000 kilometers (3,100 miles) of train tracks, Sun-Ways expects a power generation potential of 1 terawatt hour per year, enough to supply 300,000 households. The solar pioneers have ambitious plans beyond Switzerland. Co-founder Baptiste Daichert outlined the potential by saying, “There are more than one million kilometers (0.62 million miles) of railroad tracks around the world. We believe that 50 percent of these railroads could be equipped with our system.”

The company is currently engaged in negotiations with the French train operator SNCF and with other operators in Spain, Romania, and South Korea. Initial meetings are also taking place with operators in China, Thailand, Australia, and the United States.

Challenges

Railroad associations expressed concerns about the durability of the solar modules, saying that micro-cracks might occur. In addition, some critics fear that reflections might distract the train drivers. In response to those concerns, Sun-Ways enhanced its modules with a non-reflecting specialty film and use of reinforced materials.

Other skeptics pointed out that snow and ice might impair the performance of the modules. Consequently, Sun-Ways is now working on a system enabling frozen precipitation to be melted and on a brush system that can be attached to the rear of trains for clearing dirt off the panels.

When the wind isn’t blowing the sun may be shining. But what about at night? The high-tech energy float from Swedish startup NoviOcean is tackling this problem because on a windless night the ocean is still in motion – and generating energy.

NoviOcean has developed the NoviOcean Hybrid Energy Converter (NHEC), a proverbial Swiss Army knife. It’s a floating element, 38 meters (125 feet) long, 9 meters (29 feet) wide, 4 meters (13 feet) tall, and weighing 140 metric tons (154 short tons), that can absorb the hydrodynamic energy of the ocean waves. The NHEC converts the constant ups and downs of the waves into electric power. Plus, there are six wind turbines and photovoltaic panels installed on the float that can additionally produce energy.

Harnessing the energy of the waves

Power generation by means of wave energy uses a large cylinder that’s installed underneath the float and connected to the ocean floor via a piston and cables. When the waves lift the float water is pumped through a turbine. Up to 10,000 pump movements per day are supposed to be possible, according to NoviOcean’s CEO Jan Skjoldhammer. The company anticipates energy output of 65 percent from harnessing the ocean waves, 30 percent from the six wind turbines, and 5 percent from the solar modules.

Combination with offshore wind farms

Each NHEC is said to be able to deliver up to 1 MW of electric energy, according to the company. 15 of such floats could be installed on one square kilometer (0.4 square miles). NoviOcean is planning to set up its NHECs in combination with existing offshore wind farms. The company says that, as a result, up to 25 MW of electric energy could be generated on one square kilometer (0.4 square miles) of ocean surface. That would yield higher energy density and reduce expenses because the costs for the offshore area and the onshore cable could be shared.

Challenges

Challenging for long-term service are the harsh offshore conditions. In addition, the question of how complex maintenance of the NEHCs would be is largely unclear. So far, NoviOcean has run numerous tests with a down-sized model. Construction of an originally sized NEHC is currently in progress. Should everything go according to plan commercial service would be possible in 2030.

Batteries can store electric power, and so can hollow concrete spheres. The Fraunhofer Institute for Energy Economics and Energy System Technology IEE demonstrated that years ago. Now, the system is being tested in California on a larger scale.

The principle resembles that of a pumped storage power plant: when there’s excess power in the spheres, which are located offshore on the seabed, the spheres are sucked empty by pump turbines, creating a vacuum. To recover the energy, water flows back into the spheres with high pressure, driving the pump turbines and generating power. An underwater cable transfers the power ashore.

Researchers at IEE are currently preparing a test run off the California coast together with partners. There, in a project called StEnSea, they’re going to anchor a hollow concrete sphere with a nine-meter (29-foot) diameter weighing 400 metric tons (440 short tons) at a depth of 500 to 600 meters (1,640 to 1,970 feet). The output of this prototype that’s produced by 3D printing is 0.5 megawatts and its capacity 0.4 megawatt hours.

An area off the coast of Long Beach near Los Angeles was selected as the site for the storage system. It’s planned to be launched at the end of 2026 at the latest. The German Federal Ministry for Economic Affairs and Climate Action provides 3.4 million euros of funding support for the project, the U.S. Department of Energy some four million U.S. dollars.

“With the global energy transition, the demand for storage will increase enormously in the next few years. With the StEnSea spherical storage, we have developed a cost-effective technology that is particularly suitable for short to medium-term storage.”

Dr. Bernhard Ernst, Senior Project Manager at Fraunhofer IEE

Successful field test in Lake Constance

In a field test with a three-meter (10-foot) sphere in Lake Constance, IEE researchers together with partners proved as early as in 2016 that the concept with the concrete spheres works well.

Capacity and output of the spherical storage systems depend primarily on two factors: the volume of the spheres and the water column that rests on them. The experts at Fraunhofer IEE have calculated that water depths of 600 to 800 meters (approximately 2,000 to 2,600 feet) are ideal locations from an economic perspective because that’s where parameters such as pressure, the necessary weight of the spheres, and the required wall thickness are in optimal proportion to each other. Moreover, conventional underwater motor pumps can still be used at those depths and there’s no need for using high-strength specialty concrete either.

Read more

Energy storage systems of the future

Electricity storage is a key component of climate gas reduction. What role can mechanical systems such as flywheels, gravity and compressed-air energy storage play in this context? An overview. Read more

There are more than enough potential sites for StEnSea spherical storage systems at those water depths as an analysis of coastal marine areas has shown for which IEE experts have taken parameters like bottom slope, currents, sediment displacement, or distance to land into account. For example, off the coasts of Norway, Portugal, the U.S. East and West Coasts, Brazil, or Japan, the spherical storage systems could be installed in large numbers. The technology is also suitable for deep natural or artificial lakes such as flooded open-pit mines.

Huge global potential

The global storage potential of this technology amounts to around 820,000 gigawatt hours, according to calculations by the Fraunhofer researchers. At the ten best European locations, it’s still 166,000 gigawatt hours. For comparison: the capacity of the existing German onshore pumped storage powerplants merely amounts to just under 40 gigawatt hours.