Dynamic Wireless Power Transfer

An electric road, eroad, e-roadway, or electric road system (ERS) is a road which supplies electric power to vehicles travelling on it. Common implementations are overhead power lines above the road, ground-level power supply through conductive rails, and dynamic wireless power transfer (DWPT) through resonant inductive coils or inductive cables embedded in the road. Overhead power lines are limited to commercial vehicles while ground-level rails and inductive power transfer can be used by any vehicle, which allows for public charging through a system for power metering and billing. Of the three methods, ground-level conductive rails are estimated to be the most cost-effective.

Government studies and trials have been conducted in several countries seeking a national electric road network. Korea was the first to implement an induction-based public electric road with a commercial bus line in 2013 after testing an experimental shuttle service in 2009, but it was shut down due to aging infrastructure amidst controversy over the continued public funding of the technology. United Kingdom municipal projects in 2015 and 2021 found wireless electric roads financially unfeasible. Sweden has been performing assessments of various electric road technologies since 2013 under the Swedish Transport Administration electric road program. After receiving electric road construction offers in excess of the project's budget in 2023, Sweden pursued cost-reduction measures for either wireless or rail electric roads. The project's final report was published in 2024, which recommended against funding a national electric road network in Sweden as it would not be cost-effective, unless the technology was first adopted by its trading partners such as France and Germany. Germany found in 2023 that the wireless electric road system (wERS) by Electreon collects 64.3% of the transmitted energy, poses many difficulties during installation, and blocks access to other infrastructure in the road. Germany trialed overhead lines in three projects and reported they are too expensive, difficult to maintain, and pose a safety risk. France found those same drawbacks for overhead lines, and began testing inductive and rail electric road systems in 2023.

Terms like "electric highway" may also be used to describe regular roads fitted with charging stations at regular intervals.

Technology

TRL (formerly Transport Research Laboratory) lists three power delivery types for dynamic charging, or charging while the vehicle is in motion: overhead power lines, ground level power through rails, and induction through rails or resonant coils. TRL lists overhead power as the most technologically mature solution which provides the highest levels of power, but the technology is unsuitable for non-commercial vehicles. Ground-level power is suitable for all vehicles, with rail being a mature solution with high transfer of power and easily accessible and inspected elements. Inductive charging delivers the least power and requires more electrical roadside equipment than the alternatives.

Effects on roads

The German Ministry of Economy, BMWK, found that overhead power lines pose safety risks for emergency services, and the lines' roadside poles pose a collision risk for motorists.

A study published in 2017 found increased formation of reflective cracks for roads with in-road inductive coils. As part of the French government 2023-2027 study of electric roads, in-road inductive charging infrastructure was found to cause excessive strain for road surfaces using standard road materials. The study recommends using more robust materials, which reduced strains to a satisfactory level. The study found increased risk of thermal damage to the road due to the induction coils exceeding temperatures of . INDOT has been testing in 2024 a DWPT installation with special polymer-concrete previously used for bridges.

Standardization

Governments and research institutes recommended standardizing ERS technologies before choosing one specific technology. A report by the Research Institutes of Sweden (RISE) recommends inter-city infrastructure capable of 300 kW or more for best cost-effectiveness. (English translation) The Swedish National Road and Transport Research Institute (VTI) similarly recommends a system capable of delivering 300 kW per truck. The French Ministry of Ecology working group recommends 400 kW for 44-ton trucks driving at 90 kilometers per hour along a 2% grade, or at minimum 250 kW so the truck can charge along flat or gently-sloping roads. The European Commission published in 2021 a request for regulation and standardization of electric road systems.

A standard for electrical equipment on board a vehicle powered by ground level rail electric road system (ERS), CENELEC Technical Standard 50717, has been published in late 2022. The CENELEC technical standard 50740 for a complete ground-level power supply system, which was drafted in accordance with European Union directive 2023/1804, is scheduled to be published in summer 2025.

Standards for inductive charging for vehicles have been available since 2020, though they are not immediately suited for electric roads. For instance, the CEO of IPT, a vehicle inductive power transfer company, regards the existing standards as "extremely expensive" for use in electric roads. Cost-effective implementations are being explored by IPT using its Primove inductive cables technology which it bought in 2021 from Bombardier. WiPowerOne (an offshoot of the KAIST OLEV project) and Electreon, two wireless electric road companies, have been working on new dynamic inductive charging standards since 2021. ENRX, which is composed of several companies including IPT, announced in November 2024 that it plans to collaborate with InductEV to standardize dynamic wireless power transfer. SAE International notes that wireless charging systems do not have well-established foreign object detection technologies, and proposes establishing safety tests for these technologies. Foreign objects pose a fire or burn risk if metals or organisms are between the ground pad and the receiver when the system is active. SAE International has started developing standards for dynamic wireless power transfer in 2023.

Business model

The Swedish Transport Administration anticipates that a national electric road network would require interfaces between several players: the electricity supplier, the power grid company, the vehicle manufacturer, the road owner, the electric road technology operator, the metering and billing provider, and the user of the electric road. The ownership model can vary: the power grid company may own the secondary roadside electrical substations that power the electric road infrastructure or they may be owned by other players, and the power reading and payment system may be owned by a player separate from the infrastructure operator.

Early implementations

Overhead power lines have been used for road transport since at least 1882 in Berlin with Werner von Siemens's trolley buses. Over 300 trolley bus systems were in operation in 2018. Power to trolley buses is normally delivered using a pair of trolley poles positioned on top of the vehicle which extends to the overhead power lines. Implementations for highway vehicles have been developed in the late 2000s and 2010s but they are not suitable for non-commercial vehicles such as passenger cars.

Ground-level power supply in the form of electrified rails is similar to overhead power lines in implementation. Instead of an arm or pole extending to overhead power lines, a mechanical arm extends from the bottom of the vehicle and aligns with a rail embedded in the road. The rail is then powered, and power is transferred through the arm to the vehicle. Ground-level power supply is considered aesthetically preferable to overhead wires and it is suited for all types of vehicles.

The concept of a wireless ground-level power supply for vehicles was first patented in 1894. A static-charging system for shuttle buses was demonstrated in New Zealand in 1996 using inductive coils. Similar stationary charging systems for buses and other vehicles have been implemented by Conductix-Wampfler and Bombardier Primove. Primove was further enhanced to include dynamic charging while driving using inductive cables.

Development of electric road systems has matured significantly from the late 1990s through the 2010s. Several companies have developed and implemented electric road systems in the 2010s.

Projects exploring a national network

Korea

The Korea Advanced Institute of Science and Technology launched in 2009 a shuttle service with wireless dynamic charging through inductive coils embedded in the road. In 2013 OLEV launched a bus line in the city of Gumi. Another bus line was launched in Sejong in 2015, and two more bus lines were added in Gumi in 2016. All four wireless charging bus lines were shut down due to aging infrastructure. A new bus line was inaugurated in 2019 in Yuseong District. Commercialization of the technology has not been successful, leading to controversy over the continued public funding of the technology in 2019.

Sweden

The Swedish Transport Administration, Trafikverket, established an electric road program that studied the feasibility of an electric road national infrastructure for Sweden. The fact-finding program began in 2012 and assessments of various electric road technologies in Sweden began in 2013. Trafikverket was expected to announce its chosen technology for electric roads by late 2023, but due to procurement offers for the first permanent electric road on the E20 highway exceeding the project's budget, in 2023 Trafikverket began investigating cost-reducing measures in order to realize the project within its budget. The project's final report was published in 2024, which recommended against funding a national electric road network in Sweden as it would not be cost-effective, unless the technology was adopted by trading partners such as France and Germany.

The final report by CollERS, the Swedish-German research collaboration on electric road systems, advised Trafikverket to select a single ERS technology, suitable for heavy trucks, with several suppliers who use an existing standard, coordinated with German and French ERS decisions, not necessarily led by the European Union but with their coordination, utilizing an ERS-technology-neutral payment system.

France

France plans to invest 30 to 40 billion euro by 2035 in an electric road system spanning 8,800 kilometers that recharges electric cars, buses and trucks while driving. Two projects for assessment of electric road technologies were announced in 2023. Three technologies were originally considered: ground-level power supply, inductive charging, and overhead lines. Ground-level power supply technologies, provided by Alstom, Elonroad, and others, are considered the most likely candidate for electric roads. Inductive charging is not considered a mature technology as it delivers the least power, loses 20%-25% of the supplied power when installed on trucks, and its health effects have yet to be documented. Overhead lines is the most mature technology, but the catenaries and overhead wires pose safety and maintenance issues, and motorway companies find overhead lines too expensive.

Trials

Alstom has developed a ground-level power supply (alimentation par le sol - APS) system for use with buses and other vehicles. The system has been tested for compatibility with snow plows and for safety under exposure to snow, ice, salting, and saturated brine. Alstom will trial its electric road system (ERS) on the public road RN205 in the Rhône-Alpes region between 2024 and 2027. The system is expected to supply 500 kW of power for electric heavy trucks, as well as power for road utility vehicles and electric cars.

Vinci will test two electric road systems (ERS) from 2023 to 2027. Both technologies will initially be tested in laboratory conditions, and upon meeting the test requirements they will be installed along 2 kilometers each on the A10 autoroute south of Paris. Wireless ERS by Electreon will be tested for durability under highway traffic, and will attempt to reach 200 kW of power delivery per truck using multiple receivers. Rail ERS by Elonroad, which supplies 350 kW of power per receiver, will be tested for skid effects on motorcycles. Both systems will be interoperable with cars, buses, and trucks. Vinci Autoroutes installed 750 meters of the induction system by February 2025, which is expected to be tested from April until December using four different vehicles. The rail system is expected to begin undergoing testing in September 2025.

Germany

The German Ministry of Economy, BMWK, assessed overhead line systems for trucks. The project was titled "e-Highway" and culminated in three public highway trials: FESH, ELISA, and eWayBW. One such trial was launched in May 2019 on a section of Bundesautobahn 5 south of Frankfurt, operated by the ELISA consortium which includes Siemens and Scania. Results were mixed. By the end if the trial period the system was functioning satisfactorily, and operators using the technology enjoyed lower freight costs. Despite this, the Ministry encountered high costs and difficult maintenance. The Ministry found overhead power lines pose safety risks for emergency services, and the lines' roadside poles pose a collision risk for motorists. Subsequently, the Ministry ended its financial support of the trials.

Wireless electric road system (wERS) trials were conducted in 2023 by the German Ministry of Economy, BMWK, with infrastructure by Electreon. A bus was equipped with inductive coils that receive power from a 200-meter strip of transmitters under the road surface. The receivers were able to collect 64.3% of the energy emitted from the transmitters. Installation proved complex and costly, and finding suitable locations for the coils' roadside power cabinets proved difficult. The wERS infrastructure blocked access to all civil infrastructure beneath it. Internet access outages caused the wERS infrastructure to stop functioning entirely.A. Wendt et al., "Wireless Electric Road Systems – Technology Readiness and Recent Developments," 2024 IEEE Wireless Power Technology Conference and Expo (WPTCE), Kyoto, Japan, 2024, pp. 177-182, doi: 10.1109/WPTCE59894.2024.10557264.

United Kingdom

Highways England began a dynamic wireless power transfer project in 2015, and a procurement process for trials replicating motorway conditions was underway, but the project was cancelled in early 2016 for budgetary reasons. Another dynamic wireless power transfer feasibility study, dubbed DynaCoV, began in 2021 and issued its final report in 2022. The study found that dynamic wireless charging is 3 to 10 times more expensive than conductive charging and is not financially feasible. Proposed costs for were about 716,000 GBP for the inductive coils and their management units, £258,000 for civil costs including roadwork and electric grid connections, £64,000 for planning and commissioning, £18,000 for 12 months maintenance and data management, £129,500 for upfitting a bus and a van with wireless receivers, and £300,000 for the accompanying report on the project. The company that participated in the study, Electreon, intended to pave a demonstration wireless charging road in Coventry in 2024.

India

India announced plans for a 6,000-km electric highway network in 2023, which was planned to utilize overhead lines. As of October 2024, the India government's National Highway for EV body (NHEV) was considering ground-level power supply technology for the electric road project. The first part of the network is planned to be deployed between Sohna and Jaipur for use by electric buses.

Local projects

Many local electric road projects were conducted in small-scale installations of several hundred meters around the world. Among them: Bombardier, dynamic wireless power transfer (DWPT), Germany, 2013; Alstom, ground-level power supply (GLPS), Sweden, 2014; Honda, GLPS, Japan, 2018; Qualcomm, DWPT, Italy and France, 2018; Elonroad, GLPS, United States, Canada, and Europe, 2010s-2020s; Electreon, DWPT, worldwide, 2010s-2020s; ENRX, DWPT, Europe and the United States, 2010s-2020s; and others. Several of these technologies have been studied further in national ERS projects. As of 2024 there were about 10 operational ERS demonstrators around the world, and their business cases and deployment strategies are being evaluated.P. Duprat et al., "ERS Technologies," 2025 PIARC Decarbonizing the Road Sector international conference, Vienna, Austria, May 2025.

Canada

Quebec companies Transport Morneau and Filgo plan to use a ground-level power supply system by Elonroad for charging Volvo and Tyco electric heavy equipment and trucks while they park or drive. Vehicles by six or seven manufacturers are planned to take part in the trial, which was announced in 2025. The infrastructure will be tested for reliability, wear, resistance to contaminants, and profitability.

China

Zhongtong Electrified Highway Technology (中同电气化公路技术) plans as of 2024 to construct 500 kilometers of electric road by 2026 for the continuous 24-hour-a-day operation of coal-mining trucks in Xinjiang completely powered by overhead wires.

Norway

AtB and the municipality of Trondheim have tested dynamic inductive charging in 2024 and 2025. Buses were outfitted with inductive coils capable of receiving 120 kW of power. While driving at over an 80-meter strip of transmitter coils embedded in the road, the coils on the bus received on average about 65 kW.

United States

ASPIRE

ASPIRE is a research and advocacy center for electric transportation focusing on wireless power transfer. The center is headed by Utah State University professor Regan Zane, the founding director of ASPIRE. Zane had formerly headed the industry-sponsored center SELECT, which demonstrated its first inductive charging road in 2015. SELECT grew into ASPIRE in 2020. The National Science Foundation (NSF) awarded ASPIRE $26.7 million in funding between 2020 and 2024. The center participates in several wireless electric road demonstration projects alongside its industry sponsors. ASPIRE intends to "serve as an expert guide for state legislatures" in matters of transportation electrification and as of 2023 it is pursuing a further $160 million grant from NSF.

Projects

ENRX (formerly IPT) won a contract in 2023 to build a one-mile inductive rail wireless charging system capable of charging at up to 200 kW on State Road 516 near Orlando, Florida. The project is funded at 13 million dollars.

Detroit, Michigan opened in November 2023 a quarter-mile wireless charging road section near Michigan Central. The project was funded at 5.9 million dollars. The infrastructure, provided by Electreon, powered a van driving at 9 mph with 16 kW of power. The Michigan Department of Transportation (MDOT) has tested the technology from 2023 to 2025. MDOT is looking into the power losses from the grid to the wireless receiver, the optimal charging speed, the effects of misalignment of the coils when the charging vehicle is driving along the road, and the effects on the asphalt above the coils.

Indiana began constructing a strip of electrified highway in 2024 that uses inductive coil charging at 200 kW, suitable for heavy trucks. The project costs 11 million dollars per quarter mile of road. Research on the project, conducted by Purdue University's Steve Pekarek, aims to show the technology could make a transition to heavy electric trucks more financially beneficial for businesses.

Long Beach Port will begin using in late 2025 a ground-level power supply electric road designed by Elonroad, a Swedish electric road company. The project, funded at US$4.5 million by the California Energy Commission, will study the technology's weather endurance for 12 months, and will feature a road that supplies 250 kW of power to electric vehicles driving over it, and five automatic 50 kW charging stations.

References

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