Impact of EVs on Power Supply Distribution System
Published on : Thursday 11-06-2020
Abhijit Mandal dwells on the issues and the need to have advanced regulations in place to consider the various billing scenarios for EV charging.
Electric Vehicles have become the talk of the town in the automotive sector. Every automobile company has either some niche product in the market or a slew of them lined up for launch in the coming quarters. All the policy makers and governments worldwide are very much upbeat about electric vehicles (EVs) and are promoting them big time. Many governments have tax rebates to promote EV sales. We can say for sure that the electric vehicles would be the technology for mobility in times to come. How fast or slow would depend on numerous factors and would be beyond the scope of this article. What this article does is to write a brief on how these EVs would impact our power supply distribution system and on consumption of electricity.
We first start with the present Indian policy scenario with respect to EV charging infrastructure. The Ministry of New and Renewable Energy has issued guidelines for typical EV charging installation.
1. In cities, there will be a public charging station for every 3 square km.
2. One charging station every 25 km on intra-city highways.
3. On inter-city highways, there will be a fast-charging station every 100km.
Setting up public charging stations has been de-licensed, and any individual or entity is free to set them up, subject to conditions in the guidelines. Chargers of different standards – CCS, CHAdeMO, Type-2 AC, Bharat AC 001 – are specified, and individuals can choose the chargers they provide according to the market demand.
For inter-city travel, fast-charging stations will be installed at every 100km and the Bureau of Energy Efficiency (BEE) has been nominated as the Central nodal agency to facilitate installation of charging infrastructure. Furthermore, the ministry says assuming that most EV charging would take place at homes or at offices – where the decision of using fast or slow chargers would rest on the consumers – the guidelines clarify that private charging at residences/offices shall be permitted and distribution companies (DISCOMs) may facilitate the same.
To keep this technology unbiased, it has been provided that any other fast/slow/moderate charger as per approved DST/BIS standards whenever notified can also be installed at the PCS. Thus, the guidelines provide an extensive flexibility while ensuring a democratic choice to both EV owners and public charging station providers to install the type and number of chargers. The Bureau of Energy Efficiency has been nominated as the Central nodal agency, and a provision for State nodal agency for the respective States has been provided for in the guidelines. The roles of the respective nodal agencies have been specified. These agencies will act as the key facilitators in installation of charging infrastructure for EVs throughout India.
The tariff to be charged – from public charging stations (PCS) and domestic consumers for private chargers, alike – by the distribution companies have also been covered in the guidelines as has the service charges to be charged by these PCS from EV users. It has been provided that the domestic charging shall be akin to domestic consumption of electricity and be charged as such. However, in case of PCS, it has been provided that tariff for the supply of electricity to PCS shall be determined by the appropriate commission in accordance with the Tariff policy issued under section 3 of Electricity Act 2003, as amended from time to time.
It has been clarified that charging of EVs is a service as far as the service charges at public charging station are concerned. Even then, to ensure that the incentives (financial or otherwise) provided to public charging station owners to install charging stations are transferred to the EV owners, it has been provided that the appropriate agency/commission shall fix the ceiling of service charges in such cases.
Effect of EV loads on the distribution infrastructure
The typical battery bank capacity in passenger electric vehicles category would be anywhere from 25 kWhr to 100 kWhr. In layman terms the battery capacity would be analogous to the size of the fuel tank in an ICE car. However, looking from the electrical perspective these numbers tell you that these many Units/kWhr would be required to fully charge the car. So an EV with a battery bank of 36 kWhr would need 36 Units to charge from 0 to 100 %. And if we charge this EV with a 6kW charger would mean an additional 6kW load on the power distribution system for 6 hours. The numbers are just taken for ease of explanation.
The effect on the distribution system shall be two pronged:
1. There will an increase the common household electricity consumption due to EV charging per month. This figure will of course depend upon the usage of EV per month. Take away is there will be an increased electricity consumption with the advent of EVs.
2. There will be many EVs which will be getting charged overnight. Charging of EVs at night will help the distribution network infrastructure by having more uniform loading pattern than what it is in the present times. Better base load on the distribution network will mean better capacity utilisation and better voltage regulation.
Effects of various types of EV chargers
CASE 1: Granny Charger (<5 kW) This would be the most common type of charger and an EV owner would use when they have long time (typically 16-20 Hrs) available to recharge their vehicle. These chargers are nominal loads should be possible to be accommodated in the existing power distribution network. However, if the numbers are large like in a large apartment complex then an assessment should be done.
CASE 2: AC-2 Chargers (7~20 kW) This would be the typical AC fast charger and would require 6 to 7 hrs to Charge the EV. These would typically be installed in standalone houses, apartment complexes and public charging stations as well. The KW of these charger ratings would call for a capacity augmentation of the distribution system at the back end for sure. There would be a need to make a separate substation and distribution network in large residential complexes dedicated for the charging infrastructure. All new power supply infrastructure must be planned with these kind of Charger loads in consideration by default.
CASE 3: DC Chargers (50 kW and above) These would be installed at public charging station and would definitely require a dedicated substation to feed into these public charging stations. These chargers would be installed at intercity highways and the present petrol stations would have EV vehicle charging options. If space is not a constraint these setups can be installed with roof top solar modules as well to maximise the efficiency of the system.
EVs as distributed energy source (Vehicle to Grid concept)
Electric Vehicles are nothing but a large stored energy available at disposal which can be pumped back into the grid at a suitable time as per the wish of the user. This concept is being coined as the vehicle to grid concept. A couple of such scenarios are penned down to appreciate what is coming.
Scenario 1
I have a fully charged EV parked in the basement of the office and I know for sure that I do not have any long travel plans for the day. I can connect the EV to the charger in the office parking lot and set the car to pump power to the grid till it is discharged to say 30 % at the peak tariff hours and then travel back home and charge the CAR at night during off peak tariff hours.
Scenario 2
As roof top solar becomes more and more common the use of EVs in tandem with the roof top solar is going to become quite good combination. The roof top solar storage battery and the EV battery through a gateway controller can be easily programmed to work in tandem with an optimal charging and discharging scenario.
The above two cases show that in coming times we will need to have advanced regulations in place to consider the various billing scenarios. (The information presented is taken from public domain and the views are my opinion – Author)
Abhijit Mandal has masters in Power System from IIT, Roorkee. He has an industry experience of over 2 decades and his expertise is in the field of Engineering and Quality Assurance. He has been professionally associated with top conglomerates, like NTPC Ltd and Reliance Group. Currently, he is heading the Electrical Design Engineering & Quality Department of Reliance.
