From pv magazine 01/2022
Gigawatt-hours of batteries on wheels are expected to enter electricity markets around the world this decade. A fraction of this battery capacity equipped with vehicle-to-grid (V2G) technology would already be a game changer at grid level, opening substantial opportunities for both soaking up excess renewables generation and releasing electricity back into the grid to manage issues in real time. While conceptually a simple proposition, deploying V2G services at scale has proven complex. The technology has been around for over a decade, but the sector is still struggling to identify a viable commercial model.
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“Today, most V2G work has been in trials,” says Laura Jones, senior analyst in the Battery Storage and Grid Integration Program at the Australian National University. “Capable chargers are still expensive so it’s probably not going to pay for itself yet. People make decisions based on a whole bunch of reasons and many aren’t financial so I think we will see some uptake pretty quickly.”
Jones is currently involved in Australia’s biggest V2G demonstration to date, the Realizing Electric Vehicles-to-grid Services (REVS) project. It uses 51 Nissan LEAF vehicles to show that EVs can deliver frequency support to the live power system via Australia’s National Electricity Market.
When it comes to managing frequency, V2G equipped vehicles can provide inertia, regulation, and contingency services, all of which must be delivered within state of charge constraints. Generally, services that raise frequency are higher value than those that lower it, and similarly, shorter time contingency bands are worth more due to difficulties in responding to events quickly. For frequency control in the REVS project, the response needs to be within six seconds (fast FCAS). Currently, the response time of chargers varies between zero and 10 seconds for the same charger. “It is just the way the firmware works,” explains Jones. “It’s not out of the ballpark and is pretty good actually for a first attempt, but still not quite where we need it to be.”
This particularly applies to grids that are increasingly dominated by renewables, where grid response times will need to get much faster. To perform virtual synchronous machine control, the response needs to be extremely fast: under 100 milliseconds, and ideally within one or two cycles (20 ms each). From a physical hardware perspective, a V2G equipped vehicle can do this since it is not that different to a large battery. However, chargers were not built for millisecond response times. Originally, they had to respond to things like load management in buildings, where a few seconds are no big deal.
“Right now, V2G infrastructure can provide very fast response times,” says Russell Vare, director of automotive partnerships for San Diego-based EV charging solution provider Nuvve. “In fact, we’ve achieved response times below four seconds for grid services. But it’s important to note that EVs don’t necessarily need millisecond-level response time to deliver value to the grid. Demand response is one great example.”
Current speeds still provide energy price arbitrage and congestion management, which can unlock significant value for both EV owners – in the form of financial rewards and for society as a whole – putting downward pressure on wholesale energy prices. Vare explains that outside of driving duties, batteries in EVs have specific use cases. “For example, in the US, we’ve deployed V2G-enabled school buses which are focused on demand response because they are parked during summer months where energy loads peak and can be used for peak shaving during the school year after they’ve finished their afternoon routes.”
Finally, the nature of portable EV batteries is not only important for grid services, and they can also play a role in microgrids. “Imagine a bunch of electric vehicles providing power to communities during bushfires. That is where mobility is an advantage because you can charge the car at a nearby place where there is power and drive it to the community to transport energy to it,” Jones says.
Value vs. costs
Technically, V2G has already reached maturity. Many models with CHAdeMO charging plugs have been able to charge bidirectionally for a long time, and V2G capable chargers are now standardized. The list of technology needed to provide grid services is not that long: a V2G enabled charger and appropriately equipped EV, a communication platform to control charging and discharging, and metering and auditability of services rendered. But, to ensure a sufficient impact on grid operations, large deployment volumes are necessary.
What’s holding this back are upfront costs that come from additional hardware that needs to be added both to the vehicle and the charge point. As is usually the case, the key to cost reduction lies in widespread adoption, but for this to happen people would need to see enough value in it, and for some, the obtainable revenues may turn out to be insufficient.
In recent years, various models for remuneration have appeared in the V2G space. Some incentivize customers offering cheaper energy prices, such as AGL’s V2G trial in Australia. They let you bring your own car, but sometimes provide a free charger. Others offer discounted leases for cars and chargers, such as Octopus Energy’s Powerloop in the UK, which has lease contracts with an app, 100% renewable energy, smart meter, and cashback bundled in. Valuable insights into costs and customer satisfaction are already available. For example, a three-year trial in the UK called Project Sciurus, one of the largest domestic V2G projects in the world, with 320 units installed in homes throughout the country, showed that aggregated EVs participating in Dynamic Containment, the UK grid operator National Grid’s most recently launched frequency regulation service, could earn consumers up to GBP 725 ($958) a year. It also found that hardware costs must decline to make this attractive enough for consumers.
The project, run by a consortium including energy supplier OVO Energy and carmaker Nissan found that V2G chargers could save consumers GBP 340 compared with GBP 120 when using one-way smart charging. Additionally, by enabling the V2G chargers to provide grid services via aggregator Kaluza’s platform, the figure rises to GBP 513 for Firm Frequency Response and GBP 725 for Dynamic Containment. “Over the course of the program, V2G owners earned on average GBP 420 a year, with some customers earning up to GBP 800,” says Alice Goodman, director of communications at Kaluza. “Customer research also showed that 93% of V2G owners felt satisfied with their charging experience.”
Meanwhile, some of the challenges the project identified had to do with cost and complexity. It found that by the end of the trial V2G hardware and installation cost was around GBP 3,700 higher than that of a smart charger. In addition, there were a few conditions that had to be met for the provision of Direct Containment – the initiated response must be within 0.5 seconds, with full response by 1 second, assets need to be aggregated up to a minimum of 1MW, 20 Hz settlement metering must be installed, among other requirements.
Obstacles on the road
A key hurdle is concern about the lifespan of the EV battery due to potential accelerated degradation from increased cycling. This has been repeatedly refuted: battery health is not solely about minimizing how often you use it. Its lifespan is the shortest when the battery is left fully charged most of the time. V2G can help keep the battery state of charge at an optimal level thanks to the integrated battery management systems, responsible for controlling the current flow for both charging and discharging, as well as managing temperatures to maximize health and longevity. On top of that, some services, like fast frequency control, mean the EV battery would be called upon very infrequently and only be used for short periods.
Previous extensive lab tests run by RWTH Aachen University and other institutes have shown that the battery lifespan is hardly affected by the additional activity if up to a maximum of 20% of the battery’s energy is drawn in one cycle. This shows that with its smart control algorithms, V2G can even slow the rate of degradation. Big batteries in EVs are more like an underutilized resource. They are often designed for hundreds of thousands of kilometers, but the average annual distance is only around 15,000km. With a service life of 10 years, for example, and the 150,000 kilometers traveled with it, thousands of cycles remain unused.
There are also other challenges to tackle. In the US, interconnecting EVs as a grid resource is seen as the most challenging aspect of deployment, according to Nuvve. In many other markets, the regulatory framework doesn’t recognize EVs as distributed energy resources. In Germany, for instance, anyone who wants to feed electricity from their EV battery into the power grid is subject to numerous levies – both when storing and discharging.
“There is unequal treatment in the context of the Renewable Energy Sources Act (EEG) levy where hydrogen suppliers, for example, are exempt, and in the tax treatment compared to stationary storage systems, which can supply their energy to the public power grid,” says Marcus Fendt, managing director of Munich-based technology company The Mobility House. “EVs with appropriate V2G technology should be recognized as mobile regulating power plants and remunerated accordingly, so that V2G becomes an attractive option for anyone owning an EV.”
In addition to double taxation, other challenges in the regulatory framework include inadequate and expensive metering concepts for distributed energy resources and lack of dynamic tariffs that reflect grid congestion. Moreover, there is a lack of globally valid standard interface in the global EV market. Real-time communication between grid operator, charging equipment and vehicle requires unified standards, and this is not always the case. On the other hand, the goal of grid operators is clear – they want to offer a stable power network with a high share of cheap, green power and to control their grid investments and operating costs.
“In principle, V2G is already in the starting blocks,” Fendt says. “With the upcoming publication of the ISO standard 15118-20 the players promise an essential prerequisite for scalable V2G applications. This globally valid standard interface in the global vehicle market brings an affordable solution for individual customers. This development must quickly be considered in the relevant laws and regulations to avoid the wrong infrastructure investments.”
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