Is EV Charging good or bad to the grid ?
Geoffrey Chan, 6 Dec. 2021
Whether or not the new stuff electric vehicle charging is good or bad to our grids remains controversial for many years. Some hold that this additional charging load constitutes at least 10% more energy our grid must supply, so it cannot be nothing but kind of a burden. Counterpoint, EV charging is a rare and effective tool to help optimize our grids without causing any burden but conversely help tackle the peak load problem.
Is there a verdict on this argument?
The grid is not efficient
All electrical power generator burning fissile fuel, at best conversion, will turn 50% of the energy from fissile fuel to electricity and leave another 50% into the atmosphere or sea as heat loss (the exception is to re-use such ‘waste heat’ for local heating before venting.) This precious 50% conversion can only be achieved when the generator is running near its full load capacity. If the generator is running below 70% of its full load capacity, energy conversion efficiency started to drop, especially for gas turbine and they are not stable to run below 30% load.
Steam turbine performs better because there is a large energy buffer (steam) laying between the heat source (e.g., coal) and the energy sink (the grid). When more and more fissile fuel generators are burning natural gas, the energy conversion efficiency would be less than 50%, though it cannot be as low as 30%.
On the other hand, if there is no energy buffer on the ‘sink’ side to use up the unpredictable renewable energy, such renewable energy will be wasted as it cannot be taken in by the grid. Such ‘abandoned’ renewable energy is the dark side of the renewable industry that is rarely measured nor reported.
A more efficient grid with Load Management
Grid ‘Load Management’ could be referred to Demand Response in power industry. Traditionally Demand Response is costly to implement and for this reason Demand Response target, is written in the Scheme of Control Agreement of Hong Kong (the regulatory framework for the power companies in Hong Kong) to incentivize energy consumers to cut ‘contestable load’ so to reduce the peak load in their energy profiles. One of the methods to cut peak demand is to pump energy into an energy storage system as buffer.
A typical example will be freezing water into ice cubes at night in a Thermal Energy Storage (TES) tank for use as coolant in the daytime. There are more than 10,000 sets of Ice-TES used in chiller plant systems around the world and the most recent energy saving innovation will be the use of phase change material for thermal energy storage (PCM-TES).
These are some ‘artificial’ things created to shave or shift peak loads to help level an energy profile in order to benefit the grid. In this course, either create efficient constant power (such as thermal energy or nuclear energy) or uncontrollable clean power which fluctuates against weather conditions (such as wind and solar energy).
Huge investment has been spent to build buffers by either constant power or fluctuating power (e.g., pump storage for nuclear plant) or utility class battery bank (MW range) to store and discharge energy. All these ‘artificial’ loads lose at least 7% of energy per conversion, except that for big flywheel. They are all costly to build and operate and mostly create environmental damages. Nevertheless, they are viewed as the ‘necessary devils’ as no alternative exists.
The battery in EV is by far the best ‘Demand Response’ load management device, which is useful not as ‘load management’ but for the purpose of powering electrified vehicles without connecting them to the power line (the opposite is electrified train that electric wire runs along with the rail). Before the age of EV, there are very few ‘natural’ load management devices connected to the grids. Now we have EV battery come to the stage for good purpose, however, so far not a visionary market leader in utility field voices for a large-scale charge rate regulation of EV battery charging to facilitate load management.
We have seen electrical engineers jumped to dance with ‘two-way’ load management, that is, G2V(Grid to Vehicle) and V2G(Vehicle to Grid), which is like a straight copy of the ‘pump storage’ system. This is not their problems because very few electrical engineers can understand such a new (10 years till now) and universal protocol enough to think about regulating the charging rate for EV battery (IEC 61851-1).
I seem to be the first power engineer to put this into daily practice and prove that it works at low capital costs.
Regulating EV charging rate not easy
Most academics tried to relate the reflux of renewable energy with battery charging but the information flow (detecting the rate of renewable energy reflux which in turn regulates battery charging) is not available. Previously, electrical engineers have tried to use system frequency (50.xxxHz) as media to relate to information flow but in vain.
Nevertheless, if we just use EV charging to level the daily load at a location, the information flow is just within the premises with CTs attached in the output points of transformer to regulate the EV charging rate. This is a very cheap and efficient way to achieve global load leveling. It will also shifts EV charging to low load period, in particular mid-night where most vehicles are parked and wind power is usually at its maximum. The electricity demand tough is filled automatically and no renewable energy is ‘abandoned’.
Nonetheless, some engineers further argue that this is not elegant enough and they want to regulate the EV charging rate by conveying the grid peak and trough to the EV chargers through a sophisticated system with communication media and complex computational means. However, the cost and reliability of such system only keep it a sheer idea on drawing board or in research paper.
New technology for load management
For this end we developed the Power System Neutral (PSN) technology for sub-optimal load leveling. The underlying concept is that even a single switchboard load levelling contributes to the whole system load levelling goal. This is my rationale to propose PSN, the Power System Neutral technology.
Simply reduce all EV charging system’s charging rate by 50% (PSN-EVC has this feature built in and tested) could pose a great impact onto the power system when Demand Response is called upon. Grid leveling and Demand Response execution are the ‘grid value’ of EV charging, which is estimated to be a business of millions of billions of dollars, if it can be harvested by the power company.
Recently, I have regulated the EV charging load with PSN in a power company off-site depot, resulting in an effective reduction of the evening peak by 3kW in one location with just one EV charging load, and fill the night trough by 4 kW.
In another setup of 4 nos. of PSN-controlled chargers now serving a commercial office building car park, we analyzed and come up with an energy consumption chart that illustrated the load profile of the chargers (EV charging at full rate once plugged) if not with our PSN technology:
Obviously in this scenario the car park must upgrade the current limit in order to afford the extra charging load. Worst of all, it creates new peaky loads more than doubled the original ceiling.
In fact, we got this with PSN in place:
We can see that the extra loads from the four chargers are managed and allocated in a manner that guards the original ceiling, perfectly avoided stacking up new peaky loads yet dynamically spread the loads evenly across time sessions.
Imagine when hundreds of thousands of such PSN systems are set in place as EV population grows, utilities in places like Hong Kong will be confident to build more off-shore wind turbine because the night tough can be much higher with EV charging.
A fair verdict
The current rating of level 3 charger (should refer to fast DC charger) is very close to the maximum load required for EV charging, if home and workplace medium rate charging (2-7KW) sources are abundant. Without a large amount of medium rate charging at every parking space, more and more DC chargers must be equipped together with more electrical network upgrades to feed these DC chargers only occasionally used. Indeed, Level 1 and Level 2 have no effects on the grid provided that the PSN principle is applied locally.
In reality most EVs are plugged into the grid almost the same period of time, like we usually suffer from traffic jam at 8-10 am in the morning and 6-8pm at night, so does the ‘energy jam’ when all vehicles reach their destinations and get plugged within nearly the same time session. This is the single reason that prevented large scale adoption of workplace and homeplace parking. PSN levels the charging and it is beneficial for all stake holders – the grid, the driver and the EV maker, except fast charging maker and providers.
So, in my opinion, it is fair to say that every grid works better with EV batteries, provided that charging makes the load side more stable. Plugging millions of batteries into the grids with “regulated charging” would be the best and cheapest thing ever to do good to the grid. The catch is just how to regulate the charging?
Therefore, we need a slick tool to regulate EV charging and I believe that PSN is the tool.
To learn more of PSN, please visit here: www.psn-evc.com
About the author
Geoffrey Chan is the former chief engineer of the Hong Kong Electric (HKE),one of the two major power companies in Hong Kong.
To contact Chan, please email to geoffrey.chan@delightholding.com