Bidirectional charging has been possible on a technical level for a long time. So what is holding back the potential of this quiet revolution in the switch to renewable energies that has become known by the German term ‘Energiewende’?
Can electric cars help accelerate the transition to renewable energy sources? And can we solve the e-car issue of how to stabilise the irregular supply of renewable electricity?
It might still sound far-fetched and obscure, but the concept known in Germany under the term ‘bidirektionales Laden (EN: bidirectional charging) has already been designed ready for application in everyday use in the BDL Next project in Munich, to name just one. Imagine, for instance, a power outage, which is common in many countries. The consumer need not even notice; the lights do not go out and all electrical appliances continue to operate. This is not because an emergency generator kicks in, but because the electric car takes over. This is made possible by bidirectional charging: an electric car feeding electricity back into the home network.
Photo: AleaIL
The concept of bidirectional charging is based on a simple principle: not only does electricity flow from the grid to the vehicle battery, but it also flows in the opposite direction – from the car battery back to the home grid (Vehicle-to-Home, V2H), the public grid (Vehicle-to-Grid, V2G), or larger building infrastructures (Vehicle-to-Building, V2B). During periods of fluctuating electricity generation from solar and wind power, electric cars can act as mobile storage units, absorbing excess energy and releasing it as required. They can absorb excess energy and release it on demand. Since vehicles are stationary around 95 per cent of the time, there is huge storage potential sitting untapped in your garage.
Real potential for businesses
Photo: Ralph Hahn
“The core idea is that we want to stabilise the grids using renewable energy from wind and solar power, and bidirectional charging. In order for that to work, the technology must be highly reliable,” explains Luca Husemann, a research assistant working on the BiFLex-Industrie project at the University of Duisburg-Essen. Specifically, he is investigating how company fleets could be used as flexible energy storage devices. The vision here is that millions of electric cars will absorb peak loads, stabilise the grid, and reduce households’ dependence on electricity prices. When many small storage devices react flexibly, they can compensate for bottlenecks in the power grid, reducing the need for fossil fuel reserve power plants.
Bidirectional charging opens up a previously untapped potential for companies with larger vehicle fleets, in terms of both operations and energy management. This is because fleets, such as those belonging to logistics companies, municipal service providers or energy suppliers, often comprise several vehicles that are regularly parked at the depot for extended periods of time. These periods could be used to charge electricity and, if necessary, to feed energy back into the grid, either to the company’s own premises or even to the public grid. “With company fleets, usage can be planned particularly well, which is a must for efficient energy recovery,” says Husemann.
“The core idea is that we want to stabilise the grids using renewable energy from wind and solar power, and bidirectional charging. In order for that to work, the technology must be highly reliable.”
David Meyer, the project manager of the BiFlex-Industrie research project, also recognises the enormous potential of this market segment, but highlights where challenges still exist. “Currently, a bidirectional wallbox costs around 4,000 euros. However, depending on the application, savings or revenues of between 200 and 800 euros per vehicle per year can be achieved. This is, of course, still a major obstacle for companies,” says Meyer. Another major issue is the grid load: “Companies with an annual electricity consumption of over 100,000 kWh pay a particularly high price because, in addition to the standard rate, they also have to pay a higher rate for peak loads. However, load management with bidirectional charging could reduce these peak loads and dramatically reduce costs.”
Bidirectional charging offers companies further advantages: they can increase their self-consumption of self-generated solar energy and optimise electricity costs through time-shifted charging and discharging. They can also generate income by offering their batteries on the control power market. Furthermore, they can strengthen their sustainability profile, which is an increasingly important factor in the competition for contracts and skilled workers.
The devil is in the details
Photo: Hyundai
What sounds like an excellent and sustainable technological solution faces a number of obstacles in reality.
Despite functioning technology, successful pilot projects and enormous potential, the implementation of bidirectional charging is still in its infancy. While Germany is grappling with regulatory issues, other countries are blazing a trail ahead. In the US state of California, for instance, energy recovery from electric cars has long been incorporated into regional energy plans. Japan has promoted V2H for years, not least as an emergency power solution following the 2011 tsunami. China is also testing bidirectional charging on a large scale with clear guidelines and government support. In its strategy for connected mobility, the EU Commission also classifies bidirectional charging as a key technology for sector coupling.
However, for bidirectional charging to be successful across the board in Germany, electric cars must be able to supply electricity reliably, depending on grid demand, price fluctuations, or PV generation on their roofs. To achieve this in the most efficient way possible requires an entire ecosystem, including suitable charging stations, standardised communication protocols, intelligent control software, and a legal framework as the fertile soil. Grid operators, energy suppliers, vehicle manufacturers, and IT service providers must also collaborate.
A look at the BDL-Next project in Germany illustrates the complexity of the issue, and as always, the devil is in the details. At BDL-Next, grid operators, car manufacturers such as BMW, energy suppliers, software companies, and research institutes are collaborating to define technical interfaces, trial grid feedback, and develop business models.
“Bidirectional charging can only be scaled up when it is clear who is responsible for what and how billing will be handled,” says Vincenz Regener, a Research Association for Energy Economics employee and BDL-Next project manager.
He points to aspects hindering faster development: “Another issue is that standardisation of components is not yet very far along.” Although communication protocols according to ISO 15118-20 do exist, they are not yet binding and still leave room for interpretation. According to Regener, this, along with legal uncertainties and different approaches to charging infrastructure, is slowing down development.
“Bidirectional charging will only become widespread once the issues of responsibility, billing, standardisation and regulation have been resolved.”
The way out of the niche
To make bidirectional charging more widely available in Germany, technological maturity is not enough. “We need clear standards, uniform regulation, incentives for manufacturers, and investment in infrastructure,” demand experts such as Husemann and Regener. “The expansion of the charging infrastructure in the corporate context is already lagging behind,” Husemann points out.
A particularly pressing problem in Germany is that: “Mobile storage devices are not treated the same as stationary storage devices by law, meaning they are taxed twice: Once when they charge electricity, and again when they supply it. The law was supposed to be reconsidered this year. However, they have been talking about that for a long time,” criticises Meyer. He also sees an urgent need for action in the area of data communication: "Despite the standardised data interface between the vehicle and the bidirectional charging station, problems arise because the standard has not yet been fully implemented in some cases, or because it does not include all the necessary data," he says.
In this context, however, Meyer also highlights international efforts: “At the European level, for example, there is the ‘Coalition of the Willing on Bidirectional Charging’, where representatives from the energy and automotive industries, among others, are trying to agree on standards. Until now, these two sectors have not had much to do with each other apart from normal charging. But now the process is more complex because it also involves power delivery. New solutions must be found here.”
Grid operators also need to play a more active role in shaping the Energiewende. Last but not least, trust is key: people need to feel that their contribution counts and pays off.
"Despite the standardised data interface between the vehicle and the bidirectional charging station, problems arise because the standard has not yet been fully implemented in some cases, or because it does not include all the necessary data.”
Uwe Möller from the Rhineland, a private test user in the BDL Next project, is a prime example of this potential. His BMW i3 electric car, which has a bidirectional interface, is plugged in to the wallbox during the day rather than being on the road. When the sun is shining, it charges itself with electricity from the roof. In the evening, when the family is cooking and the lights are on, and electricity is expensive, the car feeds energy back into the house in a stable manner. “Not only do I save money,” says Möller, “but I also feel like I’m part of an intelligent system.” This case demonstrates that the technology exists. What is now needed is political will, clear rules, and user trust so that the exception becomes a widespread standard.
