## Nissan testing LEAF as electrical power storage and supply for office buildings; LEAF-to-Building a development of LEAF-to-Home

##### 29 November 2013

Nissan reports a successful early field test of a system that will allow companies to regulate their electricity bills using the batteries of Nissan LEAFs used by their staff to commute to work. “Vehicle-To-Building” allows up to six Nissan LEAF EVs to be connected to a building’s power distribution board.

Charging is phased during the day so at peak hours, when electricity is most expensive, the building draws power from the cars. When electricity is cheaper it flows the other way. The system ensures the Nissan LEAFs are fully charged by the end of the working day for their owners to drive home.

“Vehicle-to-Building” has been in use at the Nissan Advanced Technology Center in Atsugi City, Japan, since July. The facility benefited from a reduction of 25.6 kW during peak summer periods by controlling the charging time of the EVs, with no impact on the workers’ daily commute, or their vehicles.

The results have led to approximately a 2.5% reduction of electrical power use during peak hours, a saving of nearly ¥500,000 (US$4,900) per year in electrical power cost (based on current Tokyo Electric Power Company’s rates). Nissan plans to further test and refine the “Vehicle-To-Building” system, which is a development of the “LEAF-to-Home” system, introduced in May 2012. (Earlier post.) LEAF-to-Home power units provide an uninterrupted flow of electricity stored in the Li-ion batteries onboard Nissan LEAF electric vehicles (EV) to residential homes through the EV Power Station built by Nichicon Corporation. The system will help encourage Nissan LEAF owners to charge their cars with electricity generated during the night, when demand is low, or sourced from solar panels. This assists in balancing energy needs by supplying electricity to homes/offices during daytime, when demand is highest. It can also be used as backup power source in case of a power outage and/or shortages. The LEAF-to-Home power supply system won Japan’s Ministry of Economy, Trade and Industry (METI) Minister’s Prize in the Grand Prize for Excellence in Energy Efficiency and Conservation program for its high efficiency and energy savings. Cumulative global sales of the Nissan LEAF have now passed 87,000 units, making it the best-selling electric vehicle in history. ### Comments A saving of$4900 in electricity cost must be balanced by the cost of early battery replacement due to overuse of the battery. The Leaf's battery is not known for high durability, as many owners in the USA has experienced early loss of capacity. Overall, it is doubtful if there would be any money saved from Leaf's V2G cost shifting of electricity rates.

However, when used for UPS purpose (Uninterruptible Power Supply) that rarely see usage, the V2G will be worth it, by improving business reliability and confidence and protecting valuable sensitive electronic equipments at the work place at little to no investment cost of UPS hardwares.

Many million near future EVs with larger capacity (100+ kWh)improved batteries will certainly have a great potential to stabilize power grids and also as excellent domestic/commercial emergency power sources.

Secondly, the potential savings to end users and e-energy generators and distributors could be very important.

Managing V2G and V2B and V2H will not be an impossible challenge.

And one more concept out of the AC Propulsion white papers becomes reality.

@Harvey,
You forgot to mention that future HEV's, PHEV's, and FCV's will be able to do the same as BEV's.

With future FC's at every work place for providing combined heat and power, coupled with H2 availability similar to NG in piping today, a backup generation ability is already built in without the needs for using PEV's.

I have been looking into V2H as a practical alternative to remaining a grid connected consumer.

Our local utility as been behaving very badly (as a typical monopoly bully) and I have a particular need for occasional ~ 10/15kW supply.

Air compressor, 2kW with 3.5 on startup, welder to ~6kW plasma ~4kW household <2kW lights etc another 1kW could conceivably combine especially if 2 person are getting stuck in.
This would represent an average small business with say 10 employees.
A modest say 4Kw of solar panels can charge for house and weekly or fortnightly town trips and house and small holding houshold needs.
So 10 -15 kW intmittent V2G is on the wish list.

Realistically a second hand auto with 20kW ( thats about Nissan Leaf plug in Priuus? eRav(for high ground clearance and sensible offroad dirt road able tyres is on the enquiry list.

Currently the military are the only volume consumers of this technology.

I can see no significant technical reason that a refurbished recycled vehicle with sufficient battery would have any problem meeting my needs.

I see no reason why a competent emotor ready auto tech would have difficulty realising the conversion.
Suplementing a modest household sized battery storage bank, I could be off grid and off the bowser.

Good on Nissan, there is a real need and the financial incentive is high especially for remote area peaking and uninteruptable UPS is a good place to start.

The sums are

Good idea from Nissan. Maybe product will come soon?
I have seen the Prius do Vehicle to Home [emergency power, google up prius as generator], but to gang up Leafs and two way power flow are good advancements.

"Suplementing a modest household sized battery storage bank, I could be off grid and off the bowser."

If you have a battery bank large enough to handle the surge/peak draw then an EV could certainly be used to replenish your battery bank. You'd also need a large enough bank to carry you when the EV has gone somewhere.

The EV shouldn't require any alternations as long as it had a built in AC inverter like the LEAF has.

If you've got a programmable inverter in the house/shop system then program the EV charger to run whenever the house batteries are full.

Then you'll need a charge controller on the EV/battery line that will allow the house batteries to pull from the EV when they drop below a set voltage.

(I assume someone makes an AC charge controller. DC charge controllers connect/disconnect solar panels depending on their state and battery voltage.)

RP...HEVs and FCEVs batteries are relatively a bit small for the job.

BEVs and some PHEVs normally have much larger battery pack and would supply much more energy?

@Harvey,
But the ICE in the HEV and PHEV and the FC in FCV are electrical generators as well. The energy stored is on order of 160-300 kWh! Far more than any BEV can muster.

Yes RP, it is another way to look at it, specially for domestic power back up and more costly for commercial back up?

What makes the most sense is to use the Leaf battery as a house battery when you wear it down and need to replace it.

This would be especially worthwhile if you have net metering and you can charge the battery off peak and sell back power at peak rates.

I worry the current Leaf battery will not hold up doing double duty.

I am specifically referring to occasional IE a few hours / week. But I would think that a few hours/day of lower demand would not be very severe.
The economics of constant service implies that the vehicle be bolted down so defeating the concept.

I am not a supporter of worn down batteries as things stand because.
Mostly aged batteries will go high resistance, low capacity and high self discharge as well as likely unbalalancing prior to failure.

This results in excessive heat or e waste at both the battery and the charger.
That also implies increasing running cost, safety issues and a waste of the servicing electronics potential.

Given that round trips on a new battery could easily lose 20%, I would think that EOL battery storage efficiency can be expected to be hitting the J curve down from there.

Much better to start with cell level refurbished and balanced pack, or strings and multiple/micro/inverter
setup as per the current solar panel offerings.These would make plug and play pack matching feasible.
Or a regular (say weekly)manual assessment and swapout.

Otherwise there are cell management /redundancy designs that could take care of the expected increasingly high failure rate.

So while it is possible to exhaust all possible service from used packs, it would always be 'skilled?' labor maintenance intensive that will cause costs to escalate reducing fiscal incentive.

On the other hand packs (like Tesla's?) that can be accessed to cell level seem to offer good / better opportunities to sub stratospheric IQd Techs.

Correction,
EP's link includes a graph showing battery return efficiency from 90 to 95% on a 12,000KM old pack.
Interestingly the pack in question also showed an unexplained increase in capacity and efficiency over the test period.
Possibly related to proper cycling management 'conditioning' the pack.

It still follows that EOL packs will be substantially derated and the report authors (AC Propulsion year 2000) may well have sophisticated battery management, the vehicle management system may be blow optimum etc.
But the steady soft cycling in the particular application IE grid stabilisation had a positive effect on the battery pack.
Also made the point strongly that battery age was by far a bigger factor.

It is not a bad practice to be conservative but maybe I am a bit much one way.

California utilities are objecting to re-sale of stored "non-green" electricity at "green" rates, so perhaps such arrangements will require separate metering of local generation and anything connected to the storage system.  Just taking the building off the mains during peak hours, or shaving demand peaks, appears to be just fine with everyone.

I know next to nothing about the Leaf battery, but IIRC replacing individual bad cells is one of the options for reconditioning Prius packs.  Any good battery monitoring system will be able to flag weak cells and note when it's time to replace them, or recycle the whole pack.  So long as there's a good downstream industry for recycling the components of the cells, I see no major issues.

AC Propulsion noted a decade ago that batteries degrade by a number of different mechanisms, some on a schedule whether they are cycled or not.  (Nickel-iron is notably lacking in those, which is why Jay Leno's Baker electric is still running on its original cells.)  It makes no sense to just let a battery run out its shelf life without doing any work, so the best economics come from running out the cycle life before the calendar life expires.

Hard to say how a second hand battery will hold up as a home storage unit. I don't look at the intercalated battery as having a true resistance in the component resistor sense; but, because it is an active chemical device, I look at it as simply not accepting as many electrons as before. It's more like a bucket that has shrunk in size and won't hold as much water.

BTW, If battery development goes the way JCESR is driving it, there will be completely different chemistries available within the next 3-5 years and Lithium will give way to Mg and Al. Perhaps the characteristics of the NiFe battery will return: