Mitsubishi Envisions Electric Cars As Energy Storage Units

NOV 4 2018 BY MARK KANE 10

The company is already thinking of how to make use of EV batteries at its campuses

Mitsubishi Electric has developed an advanced energy management system for big facilities, which could lower electricity costs through optimizing on-site generation (like photovoltaic) and charging/discharging electric vehicles.

The system regularly monitors the status of EVs (checking how many is connected at the moment) and tries to minimize energy usage at peak demand from the grid. One of the ways is to stop charging some EVs or even put electricity back from batteries.

“By optimizing the schedules for not only charging EVs but also discharging their power back into the company, as well as optimizing the operation of PV and other power-generation systems according to the fluctuating unit price of electricity sold on the grid, Mitsubishi Electric’s new system enables companies to reduce their electric-power costs.”

This month Mitsubishi Electric and its affiliate Mitsubishi Electric (China) Co., Ltd. will conduct joint-demonstration tests at its own factory – Mitsubishi Electric Automotive (China) Co., Ltd. in Changshu in China. According to the Japanese company, the right system could bring 5% of savings on electricity costs (in 1,000-employee factory with 10 connected EVs).

Mitsubishi Electric: Energy-management system for power generation and power storage

Press release:

1) Reduces users’ electric power costs by 5% by optimizing EV charging/discharging schedules

Mitsubishi Electric’s new solution uses a multi-directional power conditioning system (PCS) to reduce or shift the use of grid power during peak hours by calculating minimized power costs, coordinating the charging/discharging of EVs parked at the user’s company with the use of PV and other power-generation systems, and forecasting power demand and PV power generation. A mathematical programming embedding a proprietary model is used to calculate an optimized plan for on-site power generation and EV charging/discharging based on inputs such as contracted power from the grid, electricity unit prices, power demand and expected use of EVs in the fleet under the constraints of the received-power capacity, supply-demand balance, and the maximum and minimum charge/discharge levels of EVs and on-site storage batteries.

Conventional energy-management systems set a threshold to prevent the user’s power demand from exceeding its contracted power from the grid. EVs are charged in advance, allowing them to be discharged if power demand exceeds the threshold. However, if a number of EVs must be used off-site unexpectedly, this can result in the need to charge EVs when the electricity unit price is still relatively high.

In simulations using a scaled-down 1:10 model of a 1,000-employee factory, typical power demand, and EV usage, power costs in the case of using 10 EVs were found to be 5 percent less than in the case of using no energy-management system.

2) Uses multi-step control to minimize electric power cost increases in case of unexpected EV usage

The EV operation plan and charge/discharge schedule are regularly optimized through the use of a “one-day plan” that is calculated several times each day to establish the charge/discharge schedule for the next 24 hours, a “correction plan” calculated every several minutes to refine plans for the next several hours, and a “control command” calculated every several seconds. Concurrently, the system continuously monitors the amount of electricity purchased from the grid and the state of charge of EVs parked on the company’s campus.

Conventional energy-management systems correct plans when PV power generation or power demand deviate significantly from the projected one-day plan. However, since these systems do not make allowances for factors such as delays in EVs arriving at the company or undercharged EVs, purchasing power during peak hours sometimes becomes unavoidable, resulting in higher costs to the company.

Mitsubishi Electric’s system regularly monitors the status of EVs connected to or disconnected from the PCS, minimizes power costs by using connected EVs as storage batteries, and refines the charge/discharge schedule every few minutes, thereby minimizing power-cost increases due to any unexpected use of EVs.

Categories: Charging, ESS

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10 Comments on "Mitsubishi Envisions Electric Cars As Energy Storage Units"

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Huge fleets of connected EVs are the smart, elegant way to keep the grid balanced. Expensive stationary batteries are a dumb, brute force approach.

There are niches which need a little brute force, of course. But connected EVs will dominate. Assuming we build enough EVs.

Do Not Read Between The Lines
For grid balancing, sometimes you’ll want demand, and sometimes supply. The more EVs there are, the more important managing charging demand will become. Given new cars have Internet connectivity (via cell or wifi) anyway, this becomes a software problem to enable smart charging. Buy-in is simple: do what you’re doing anyway, but for less On the supply side, V2G’s key benefit is avoiding the cost of dedicated storage. The disadvantages are that vehicles move around, so control and availability is not guaranteed, scale and capability are determined by vehicle battery capacity, on-board charger and EVSE, and that the price paid to the EV owner must be greater than the end-user price paid for the electricity used. As the cost of batteries falls, the cost of dedicated storage will also fall. There are economics across the electricity that will provide opportunities for storage at generation, distribution and end-user. As the levelized cost of non-dispatchable renewable generation falls, generators will increasingly be able to use their cost advantage to add storage that allows them better to manage generation, and time-shift their output . As the cost of battery systems fall, utilities will be able to add large-scale battery systems to their grid… Read more »

This only works if you can prove that there is no degradation in the car’s batteries. Otherwise employees end up footing the bill.

Large dedicated battery systems keep the degradation costs known and paid for by the factory/utility.


Funny, V2G always struck me as the opposite of elegant: a crude attempt to piggyback on something that is not really suitable for the use case, riddled with problems of economy as well as practicality.


Awesome, that’s precisely where our future should be.

There’s no need to argue about “EV vs. stationary battery”. Very clearly both will serve important roles in a renewable-dominated future grid.

EV batteries have the immense advantage of very low upfront cost (once the grid-connection system is set up, the battery is already paid for), reducing the need for stationary system or auxiliary generation.

Stationary batteries have the advantage of closer control, and less susceptibility to mass “herd behavior” events under extreme circumstances, etc.

Given the intermittency of most renewable sources, we can make use of both.


The vehicle battery is “already paid for” only if you ignore degradation due to grid usage that it is not intended for.


Mitsubishi’s current absence of fully electric cars should rather encourage them to envision electric cars as passenger vehicles first.


Nick you may or may not be aware but Mitsubishi introduced The i-MiEV in 2009 as the world’s first modern highway-capable mass production full electric car and its still available along with rebadged versions from Citroen and Peugeot. My neighbour has one and it is much loved.

David Cary

Calling that a car in NA is a bit of a stretch. Still available? In the US? Even of it technically was – ie 1 sale per month, it really doesn’t count. Mass production – bit of a stretch also. In the 9 years, US sales are less than 1 week of a model 3, arguably the first mass produced EV outside of China. Europe sales were better but 5k over 9 years is nothing to be proud of. Certainly not mass produced by most definitions of the term.


With some variants of the i-MiEV having a LTO (lithium titanate) battery, I guess these might be pretty much the only EVs where V2G could be an attractive proposition: these batteries have a very long cycle life, that is likely overkill in a vehicle — it might be the only EV battery that will typically outlast the vehicle… Putting it to some extra use might actually make sense here.

(But only here.)