Electric Vehicle supported PV Smart grid
Solar powered bidirectional EV charging station - TU Delft - PRE - LMS
Two major trends in energy usage that are expected for the future are:
- Increased electricity production in the form of distributed generation using renewable energy sources like solar and wind
- The emergence of electric vehicles (EV) as the future mode of transport
However, there are many bottlenecks for the emergence of these two technologies.
- Electric vehicles are only ‘green’ as long as the source of electricity is ‘green’ as well. If the electricity for the vehicle comes from a thermal power plant, its no-longer a clean transportation method.
- PV power production suffers from variation in sunlight on a daily and seasonal basis. This necessitates the need for battery storage technology, which is bulky and expensive.
- Impact on the electricity network due to increased power demand resulting from charging of large number of electric vehicles·
- The requirement of EV customers to have quick charging, i.e. be able to charge the electric vehicle in short span of time in the order of a few min.
Currently, solar EV charging stations work on alternating current (AC) by using two separate DC/AC inverters to charge the EV from PV over the AC grid. However, this is not efficient due to the DC/AC power conversion and not cost-effective as we need two DC/AC inverters, one for PV and one for EV.
Direct solar V2G charger:
The EV-PV project has developed the world’s first solar-powered direct vehicle to grid (V2G) electric vehicle (EV) charger. The charger enables direct DC charging of EV from PV without converting to AC. Secondly, the charger is bidirectional, so energy from the EV battery can also be fed to the grid for V2G. The charger can realize four different power flows: PV à EV, EV àGrid, Grid à EV, PVàGrid. The 6kW and 10kW modules are modularly built and can be operated without solar input as a bidirectional EV charger as well. Further, several DC charger modules can be operated paralleled for fast charging up to 150kW.
Silicon carbide (SiC) devices and soft switching have been combined in a complementary manner that has resulted in the developed converter to have much higher switching frequency while maintaining a high efficiency (95.2% for PVàEV, 95.4% for GridàEV, 96.4% for PVàGrid). In particular, the developed charger has a much higher peak (+2%) and partial load efficiency (up to +15%) than state-of-the-art solutions based on AC power exchange using separate PV inverter and EV charger. The integrated EV-PV solution has a lower component count, three times higher power density and lower cost than using separate EV charger and PV inverter exchanging power over AC. The charger is compatible with the CHAdeMO and CCS/Combo charging standard and has been tested with several CHAdeMO compatible EVs like the Nissan Leaf.
Beyond the converter design, new smart charging algorithms developed in the project integrate several applications together: PV forecast, EV user preferences, multiplexing of EVs, V2G demand, energy prices, regulation prices and distribution network constraints. This results in the benefit of each application adding up, thereby reducing the net costs significantly when compared to earlier algorithms For two case studies simulated for Netherlands and Texas, the proposed algorithms reduced the net costs by up to 427% and 651% when compared to average rate charging, respectively.
Energy & mobility transition
The charger hence facilitates the energy transition from fossil fuels to renewable energy in both the mobility and energy sector. This unique combination makes the charger a ‘power neutral’ system, which goes beyond being just an ‘energy neutral’ system.
The project was funded by Dutch government TKI Urban Energy grant and the PhD dissertation of Gautham Ram Chandra Mouli can be accessed at www.tiny.cc/grcm-phd
Recognition for the project (click below):
- Awarded the ‘Most Significant Innovation in Electric Vehicles’ award from IDtechEx in 2018
- Awarded the ‘Best Tech Idea of 2018’ by science magazine KIJK
- Featured on Dutch national TV NPO1, on the series ‘Breakthrough’ as part of the show Eenvandaag,
- Top three finalist for emove360° award 2017, Stuttgart in the category of Energy storage
- Selected for the TU Delft dig-it exhibition, the largest scientific exhibition in the Netherlands
Related publications for further reading
1. G. R. Chandra Mouli, P. Bauer, and M. Zeman, “System design for a solar powered electric vehicle charging station for workplaces,” Appl. Energy, vol. 168, pp. 434–443, 2016
2. G. R. Chandra Mouli, J. Schijffelen, P. Bauer, and M. Zeman, “Design and Comparison of a 10kW Interleaved Boost Converter for PV Application Using Si and SiC Devices,” IEEE J. Emerg. Sel. Top. Power Electron., vol. 5, issue 2, pp. 610-623, 2016
3. D. van der Meer, G. R. Chandra Mouli, G. Morales-Espana, L. Ramirez Elizondo, and P. Bauer, “Energy Management System with PV Power Forecast to Optimally Charge EVs at the Workplace,” IEEE Transactions on Industrial Informatics, vol. 14, issue 1, pp. 311-320, 2018
4. G. R. Chandra Mouli, J. Schijffelen, M. van den Heuvel, M. Kardolus and P. Bauer, "A 10kW Solar-Powered Bidirectional EV Charger Compatible with Chademo and COMBO," in IEEE Transactions on Power Electronics., vol. 34, no. 2, pp. 1082-1098, Feb. 2019.
5. G. R. Chandra Mouli, R. Baldick, M.Kefayati, and P. Bauer, “Integrated PV Charging of EV Fleet Based on Dynamic Prices, V2G and Offer of Reserves”, IEEE Transactions on Smart Grids, vol. 10, no. 2, pp. 1313-1325, March 2019.
6. G. R. Chandra Mouli, P. Bauer, and M. Zeman, “Comparison of system architecture and converter topology for a solar powered electric vehicle charging station,” in 2015 9th International Conference on Power Electronics and ECCE Asia (ICPE–ECCE Asia), 2015, pp. 1908–1915
7. G. R. Chandra Mouli, and P. Bauer. "Optimal System Design for a Solar Powered EV Charging Station." In 2018 IEEE Transportation Electrification Conference and Expo (ITEC), pp. 1094-1099. IEEE, 2018.
8. G. R. Chandra Mouli, P. Venugopal, and P. Bauer, “Future of electric vehicle charging,” International Symposium on Power Electronics (Ee), pp. 1–7, 2017
9. G.R. Chandra Mouli, D. van der Meer, P. Bauer, M. Zeman, J. Schijffelen, M. van den Heuvel and M. Kardolus, “Charging Electric Vehicles from Solar Energy: Integrated Converter and Charging Algorithms”, Energy Open symposium, 2017
10. G. R. Chandra Mouli, J. Kaptein, P. Bauer, and M. Zeman, “Implementation of dynamic charging and V2G using Chademo and CCS/Combo DC charging standard,” in 2016 IEEE Transportation Electrification Conference and Expo (ITEC), 2016, pp. 1–6
11. G. R. Chandra Mouli, M. Leendertse, V. Prasanth, P. Bauer, S. Silvester, S. van de Geer, and M. Zeman, “Economic and CO2 Emission Benefits of a Solar Powered Electric Vehicle Charging Station for Workplaces in the Netherlands,” in 2016 IEEE Transportation Electrification Conference and Expo (ITEC), 2016, pp. 1–7
12. G. R. Chandra Mouli, J. Schijffelen, P. Bauer, and M. Zeman, “Estimation of ripple and inductance roll off when using powdered iron core inductors,” in Power Conversion and Intelligent Motion(PCIM) Europe 2016, pp. 1-8