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Mitsubishi Electric Shows Prototypes of Ultracapacitor-Battery Hybrid Energy Storage Device

Mitshesd
Comparison of cycle life, 8C. Click to enlarge.

Mitsubishi Electric Corp has demonstrated prototypes of a hybrid energy storage cell that combines the fast charge-discharge power capabilities and long life of an EDLC (electric double layer capacitor) and the greater energy storage capacity of a Li-ion battery in a single cell. The new device is expected to be used for storing regenerated power from a motor (i.e., through regenerative braking) or leveling the output of a photovoltaic system.

The company showed two prototypes of the device: a 10 Wh, 3 x 3 cm unit developed as a proof-of-principles device; and a 14 Wh, 6 x 9 cm flat-wound unit with power and energy densities of 3 kW/kg and 60 Wh/kg, respectively. Under an 8C rate, the 3 x 3 proof-of-principles unit achieved 2,000 cycles before degrading 20%—some four times the cycle life of the Li-ion batteries used as a baseline.

Mitsubishihybrid
The 14 Wh prototype. Click to enlarge.

Average voltage is 3.2V, lower limit voltage is 2V and the upper limit is 4V.

The devices feature an anode shared by the capacitor and the battery, each of which have a cathode and a separator. The shared anode in the 3 x 3cm type is sandwiched between the two cathodes. In the larger, flat wound device, the first and second cathodes are formed on the front and back of a collector foil.

The key to realize the new device is the structure of the shared anode, Mitsubishi Electric said. The anode is made with carbon material. The capacitor cathode was made with activated carbon, and the battery cathode was made with a lithium-iron phosphate material.

Comments

3PeaceSweet

20kg of these would give you 60kW output and 1.2kWh of storage plenty enough for a hybrid and would take the load off a PHEV / EV battery pack.

SJC

This may be the way to go for HEVs. They cycle 100,000 times and there is no plug in, so they just charge off the engine/alternator. They would capture much more regenerative braking energy too.

HealthyBreeze

SJC,

Are you talking about sawtooth wave HEV where the capacitor/battery pack would power the car for 30-60 seconds at a time, then be recharged by a stop-start genset running only at optimally efficient RPM? I think such a mode would discharge about 200,000 times for 100,000 miles of travel. Wouldn't that be best served by supercaps with about 400Wh of storage?

SJC

It would be like the BAS with caps. You really need them for acceleration from stop and regenerative braking. The last super cap spec I saw quoted more than 100,000 max min cycles which sounds like more than 10 years. Look at the spec for batteries..after 5 years they are 60% capacity.

Engineer-Poet

The test units only hit 2000 cycles before reaching 20% degradation, but the article doesn't state the depth of discharge.  Shallower cycling would almost certainly increase the lifespan a great deal.

Limiting the units to their 8C rate, at 2.4 kW/kg a 30 kg pack would supply 72 kW; nearly 100 horsepower.  This is enough to accelerate a substantial vehicle at a good pace, and can brake a 1500 kg vehicle from 45 MPH to 0 in 4.5 seconds (if traction is no limit).  A Prius-class vehicle could use a smaller engine and bigger motors to achieve both higher performance and superior economy with a similar battery weight.

HarveyD

An ESStor ESSU will do all of that, if it ever comes out to the market place).

Meanwhile, adding current up-to-date super caps could increase take off power, e-braking, power recoup, while extending batteries life and mpg for most HEVs and PHEVs.

Wonder why it has not been tried already.

HarveyD

An ESStor ESSU will do all of that, if it ever comes out to the market place).

Meanwhile, adding current up-to-date super caps could increase take off power, e-braking, power recoup, while extending batteries life and mpg for most HEVs and PHEVs.

Wonder why it has not been tried already.

kelly

FYI: AFS Trinity http://www.youtube.com/watch?v=PQjf6AdPyS0 150mpg super capacitor/battery SUV

http://green.autoblog.com/2010/02/05/afs-trinity-talking-to-delaware-to-build-150-mpge-vehicles-the/

ai_vin

@kelly
"AFS Trinity is full of it. Their 150 mpg estimate is wholly deceiving...Taken from the company website, here is how AFS Trinity gets to the 150 mpg number:

Mileage is based on a typical week of driving: 40 miles, 6 days per week and 80 miles on one day each week. The first 40 of every day are electric and gasoline is used for longer distances. For this driving profile, the XH-150 uses up to 2 gallons of gas for 320 miles traveled which works out to 160 mpg, which we round down to 150 miles per gallon."

If the first 40 miles of each day are electric that's 280 miles per week: 320 - 280 = 40 miles on 2 gallons of gas. This SUV gets 20 mpg, the same as any other SUV. Don't get me wrong, anytime you can avoid using gas is good but claiming 150 mpg under very specific conditions is like me claiming my car got 150 mpg on the drive home today - my drive home is all downhill and I can put it in neutral and coast almost the whole way.

kelly

Don't other PHEV's claim similar mileage methods?

HealthyBreeze

@ Kelly,

Yes, and it is equally disingenuous for them to do so.

If we're trying to compare miles per gallon on a PHEV, we should fill the tank, charge it up, and let it drive on a track until it can't go anymore.

If we're trying to compare cost to travel 1,000 miles, we should let them count the cost of the daily charge and the gasoline, and the PHEV will do substantially better than just using gasoline, but it's still wrong to claim 150 mpg for the trinity system, because 130 of those miles came from the grid and did cost something.

PHEV need a standard, reasonable method of calculating operation costs. Anyone? Anyone?

SJC

"Wonder why it has not been tried already"

I would say cost and lack of necessity. Prius and Escape hybrid have good battery life. It would make battery capacity stay higher over more miles and would recover more regenerative braking energy, but cost could be the major consideration.

ai_vin

PHEV need a standard, reasonable method of calculating operation costs. Anyone? Anyone?

The simplest way would be with a graph; if you plot mpg on the vertical and mpt(miles per trip) on the horizontal you'd get a line that curves downward with distance traveled. Any driver who knows how far he's going to go will be able to see what his mileage will be. You could also plot multiple lines on the same graph one for each likely speed or driving cycle.

SJC

I would favor miles per gasoline gallon equivalent in BTUs. The power plant may be 40% efficient, then you have transmission, conversion, storage, controller and motor. It might come out to 60 mpge, which tells the driver what they can expect in real world terms.

HealthyBreeze

@ SJC,

That's a step in the right direction. Eventually, there will be the question of where the electricity came from? Cogeneration plants are even more than 40% efficient. Solar and wind probably have some aggregate converstion efficiency if you count their latent energy cost and the fossil fuel required for their maintenance. That's a fuzzy number based on amortization assumptions of their service life and total energy produced over that span, but it can still be arrived at in some meaningful way.

HarveyD

SJC:

Will we be condemned to buy and use the cheapest lowest quality products (vehicles etc) forever in order to have more of them? My four-door garage is better than the neighbour's three-door because it shows the world that I'm richer and may have 4 vehicles. Leave 2 vehicles parked outside to make believe that you may have six etc.

Is this what will be accepted as higher quality of life in the future?

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