Electric Vehicles and Grid Integration (status september 2019)
Gautham Ram, Delft University of Technology and Menno Kardolus, Power Research Electronics b.v. (PRE Power Developers)
In the next couple of years, the number of electric vehicles will increase rapidly, reaching between 23-43 million in annual sales by 2030 . This will have a significant impact on the electricity grid reaching between 640-1110 TWh by 2030 . Approximately 2% of all cars are fully electric at the moment with which the electricity distribution grid can cope, barely. This is primarily due to the high peak power of EV charging during the peak evening demand. What if 10% or maybe 20% of all the cars are electrical? The grid must innovate to be able to meet the new demand. However, when you can integrate EVs in a smart way into the grid, new opportunities will arise. By controlling charging power and time and by bundling all the batteries of electric vehicles, an enormous virtual power plant will arise that will make the grid more stable and create economization for households, energy companies and countries.
Smart charging (V1G) versus Vehicle-to-Grid (V2G)
At the moment, a lot of research is being done to integrate the grid and electric vehicles in an intelligently coordinated way. The underlying technology is available, and a lot of pilots are being conducted. There are two main technologies: V1G and V2G.
V1G is also often described as Smart Charging. With V1G, it’s possible to control the time and magnitude of charging power from the power source to the EV. V1G can be used for a multitude of applications like congestion management, frequency regulation or charging from renewables like PV. V1G is mainly interesting if the power demand (not necessarily the energy demand) becomes too high. When this is the case, one can control the power with which cars charge remotely, so that the grid will be unburdened.
V2G (Vehicle-to-Grid) goes further than that. It makes it possible to feed the energy in the batteries of the cars back to the grid. With V2G technology, it’s possible to control the time, magnitude and direction of (dis)charging power. An electric vehicle can feed power to the home (V2H) or building (V2B), to a load (V2L) or to the grid (V2G). V2G can be used for all applications of V1G but also for unique applications such as short-term storage for renewables like PV, higher capacity for frequency regulation, as well as for off-grid applications.
Main challenges for V1G/V2G
The basic technology for V1G and V2G is available. Still, a number of challenges have to be met to be able to unroll this technology on a larger scale. The biggest challenge for both V1G and V2G is the standardisation and communication protocol between the various actors involved. The image (source: ElaadNL EV related protocol study v1.1) shows, which actors there are: from the electric vehicle to the DSO (the distribution system operator). The software and business contracts have to be written and the complete chain has to respond automatically within a few seconds. This challenge applies to both V1G and V2G.
Another critical challenge is the fact that V2G is only possible with DC charging. Right now, not all cars are equipped with a bi-directional on-board charger. The same is valid for the charging infrastructure. At the moment the focus lies mainly with installing as many chargers as possible. Because AC chargers are a lot cheaper than DC chargers, AC chargers are being installed more frequently. To apply V2G more bi-directional onboard chargers and bi-directional DC charging infrastructure are necessary. To implement V2G, a more significant investment is needed than that required for V1G, but the revenue of V2G will be higher too.
On its own, smart charging (V1G) can have a massive impact on the grid by reducing peak demand and charging only when demand is lower. With V2G, a plethora of new opportunities open up, and five of these key applications are listed below:
1. V2G Peak shaving (Congestion management)
Buildings (Companies or residences) sign a contract with their energy network operator based on maximum usage (the peak). When the building exceeds the peak that is agreed upon, it pays an extra fee. If the company can decrease the peak, it will pay less per month. V2G is exceptionally well suited for peak shaving. The EV batteries charge during off-peak time and intercepts by discharging when there are peaks in demand. Monthly fees and maximum power usage decrease by using V2G technology.
2. V2G Arbitrage Opportunities
V2G makes it possible for the EV battery to trade in the energy markets. When prices are low, energy will be bought and stored. When the price is high, the energy will be sold again.
3. V2G Frequency Control
The energy grid is set up at 50Hz (60Hz in the USA). When demand peaks, big generators make sure extra energy can be supplied and that the grid remains stable. The spinning reserve basically acts as an extra buffer of available energy. Since these machines are actually spinning, keeping them operational costs significantly for fuel and maintenance. Since the batteries are controlled by the software on the bidirectional V2G converter and respond within a few seconds, this is a much more efficient solution compared to mechanical, spinning machines. V2G enabled EVs can participate in primary, secondary and (potentially) tertiary frequency control markets and will make sure that the cost for network operators will decrease. It is expected that consumers willing to contribute to this will be compensated financially.
4. V2G Microgrids and Network Outages
V2G enables you to create your own microgrid. Combining this with renewable energy sources it will be possible to be completely off-grid and still have energy. V2G can also be used as energy backup. If there are problems with the grid operator and there is a power outage, the battery can serve as a backup grid.
5. V2G Renewable Energy Buffer
Electric vehicles are seen as the sustainable future of transport. However, they are only truly sustainable if the electricity used to charge them comes from sustainable sources and not from fossil fuels. There is an evident increase in the usage of renewable energy sources like solar energy and wind energy. At the moment, this energy is being directly fed back to the grid. Smart technology makes it possible to charge cars directly from solar energy or store it in batteries. Only when the energy is not necessary anymore or when prices are right, the energy can be delivered back to the grid.
V2G business models
Due to its varied applications, V2G is a crucial tool that enables a more efficient utilisation of the grid and a high penetration of renewable energy like wind and solar energy. V2G is about solving problems with smart software versus old school investments in more cables and high-voltage lines. Besides privately owned EVs, another interesting business model is V2G Commercial EV Fleet Operations. When a company has a large fleet of cars, this fleet can be commercially deployed using V2G. Aforementioned business models like peak shaving and power outage backups can be offered to neighbouring offices.
According to research conducted by ABI Research V2G technology can ensure additional revenue of up to $2 billion for global utilities by 2025. The study says the technology could enable consumers to save up to $272 per year on their energy bills. On the other hand, other studies put the profits from V2G per vehicle in the range of $0-$8000 per year [2, 3]. The wide range goes to show how several parameters influence the V2G business models and how further research in this domain is required, including the estimation of battery degradation. The critical parameters that affect V2G revenues are the market prices ($) of ancillary services; the V2G power capacity (kW) of vehicle, charger, and distribution network; and the energy capacity (kWh) of the vehicle’s battery.
Roadmap Grid Integration
Yet another challenge for V2G is charging standards. For V2G the standard CHAdeMO is much further developed than CCS, owing to an early start in V2X in 2012. However, according to CleanTechnica CCS appears to become the dominant charging standard in Europe.
At the end of 2018, the administrator of the CCS standard (CharIn) released their own roadmap for Grid Integration Levels. This roadmap describes four different levels. Level 1 and 2 are V1G integration levels, expected to be applied by 2020. CharIn expects Level 3 (V2H) and Level 4 (V2G) will be introduced around 2025.
Solar powered Vehicle to Grid (V2G) fast charger module
Since 2009 Power Research Electronics b.v. (PRE Power Developers) is a well-known Charger Module supplier for OEM (charger) companies. Their customers provide DC Fast Charging solutions all over the world. In cooperation with the Delft University of Technology and Last Mile Solutions, PRE Power Developers recently developed and produced a 10kW solar powered bidirectional EV charger module. This first of its kind charger makes it possible to charge electric vehicles directly using solar (PV) power on DC, preventing the conversion losses from DC to AC (and back) . It hence requires only one inverter for both PV and EV and is upto 17% more efficient than the current chargers exchanging power on AC. The 10kW solar powered module is hence a smart integration between an MPPT solar module and a V2G charging module. The charger can be used modularly, making it possible to place several modules in parallel, to achieve a power of 150 kW. This innovative sustainable charger has received several awards, including “the Most Significant Innovation in Electric Vehicles” award from IDTechEx in Berlin and the “Best Tech idea of 2018” by science magazine KIJK.
1 ‘Global EV Outlook 2019’Int. Energy Agency, no date, pp. 1–143.
2 Tomić, J., Kempton, W.: ‘Using fleets of electric-drive vehicles for grid support’J. Power Sources, 2007.
3 Andersson, S.L., Elofsson, A.K., Galus, M.D., et al.: ‘Plug-in hybrid electric vehicles as regulating power providers: Case studies of Sweden and Germany’Energy Policy, 2010.
4 Chandra Mouli, G.R., Schijffelen, J.H., van den Heuvel, M., Kardolus, M., Bauer, P.: ‘A 10kW Solar-Powered Bidirectional EV Charger Compatible with Chademo and COMBO’IEEE Trans. Power Electron., 2018.
About the writers:
dr.ir. Gautham Ram is an Assistant Professor in the Department of Electrical Sustainable Energy at the Delft University of Technology, The Netherlands. He received his bachelor’s and master’s in Electrical Engineering from the National Institute of Technology Trichy, India in 2011 and the Delft University of Technology in 2013, respectively. He received his PhD from the Delft University in 2018 for the development of a solar powered V2G electric vehicle charger compatible with CHAdeMO, CCS/COMBO and designed smart charging algorithms. The project was in collaboration with PRE Power Developers, ABB and UT Austin. From 2017 to 2019, he was a postdoctoral research at TU Delft working on Flexgrid, Trolley 2.0 and Orchestrating Smart Charging project. He is also the coordinator and a lecturer for the Massive Open Online Course (MOOC) on Electric cars on edX.org. His current research focuses on electric vehicles, EV charging, PV systems, power electronics and demand-side management.
Mr. Menno Kardolus (Male) received his M. Sc. in Electrical Engineering and electrical machines at the Delft University of Technology in 1996. He is the CEO of PRE Power Developers with expertise in power electronics. He is patent holder of several power conversion patents. Last years Menno specialized in power electronics for EV Charging and Renewable Energy Systems. Together with the Delft University of Technology, PRE Power Developers developed the first direct solar fast charger in the world. This research in published in IEEE Published (Transactions on Power Electronics): A 10 kW Solar-Powered Bidirectional EV Charger Compatible With Chademo and COMBO. This research won the IDTECHEX award, Berlin 2018.
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