Even Low Efficiency Energy Storage Devices Become Competitive With Spiraling Fuel Costs

If energy from the grid costs 13 cents/kW-hr and a 1000 cycle battery costs 27 cents/kW-hr, and diesel is 40 cents/kW-hr, then a 33% efficient energy storage device that is capable of thousands of cycles over its lifetime suddenly starts to look interesting.

Maybe it's possible to trade a little efficiency for higher energy density or lower initial costs.

For example, the flywheel below is 86% efficient but has an energy density of only 5.5 W-hr/kg.

It would be cost effective to find something that was only 50% or 40% efficient but with 10X the energy density.

Bret Cahill

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System Description Continuous rated power 50 kW Peak power 120 kW Charge or discharge time 60 seconds at 50 kW Mass 135 kg Volume 110 litres Diameter 24 in (610 mm) Height 18 in (460 mm) Specific power 370 W/kg (continuous)

890 W/kg (peak) Specific energy 5.5 Wh/kg Typical DC interface 600 - 750V Self-discharge rate 0.5 - 1.0 kW Typical Efficiencies at Rated Power Motor/generator 98% Inverter 95% Net one-way 93% Net round-trip 86% Flywheel Rotor General description Composite flywheel rim with aluminum hub Operating speed range 15,500 rpm - 31,000 rpm Polar inertia 0.720 kg=B7m2 Energy storage 1,000 Wh @ 31,000 rpm 250 Wh @ 15,500 rpm Net energy storage 750 Wh Motor/Generator General description Permanent magnet, 3-phase, synchronous, liquid cooled Frequency range 515 Hz - 1,030 Hz Line-line voltage 230 Vrms at 515 Hz 450 Vrms at 1,030 Hz Total inductance 100 =B5H Line-
Reply to
Bret Cahill
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Just more number plucked out of your arse. We can tell from the smell.

But doesnt with real numbers.

Fraid not.

Pity about the other downsides of that.

No such animal.

Useless as a tractor for any real work.

Reply to
Rod Speed

But its standby power loss is absurd. That's why they are used as a short-term UPS sources - if that - rather than as daytime-nighttime energy movers or vehicle sources.

Absolutely. If batteries were 10x as dense, and lasted 10x as many cycles, as they can do now, all sorts of things would change.

Sadly, batteries have to carry all their reactants, and all their waste, whereas a fuel engine doesn't. And batteries damage themselves when charged and discharged. And quick charging needs huge power inputs, with consequential thermal problems; a 50% efficient battery would cook if you charged it fast.

The ideal battery might use air as one reactant, have its chargable component refreshed off-vehicle, and dump its wastes. Sure sounds like a fuel cell to me. Or a gas engine.

John

Reply to
John Larkin

Or a Zinc-air battery. Which has the additional advantage that it produces no waste.

Rob

Reply to
Rob Dekker

The vehicle still has to lug around the zinc oxide, which is heavier than the original zinc. And it has to be collected and reprocessed.

Wiki puts zinc-air fuel cell density at 370 WH/KG. Gasoline is 12,500. That's 34:1.

John

Reply to
John Larkin

An EV can go 80 miles. A tractor only needs to go one mile. That's 80:1

2.3 X more energy density than necessary.

Bret Cahill

Reply to
Bret Cahill

Depends on the application.

But perfect for farm tractors.

Remember, 33% efficiency is now competitive for high cycling energy storage devices. This number will continue to drop.

That's not only trivially obvious but also irrelevant to the issue:

Including lower efficiency energy storage devices in a big net search for higher energy or power density.

Bret Cahill

Reply to
Bret Cahill

When the farmer gets out the tractor, it usually runs for hours and hours under load. The straight line distance isn't a factor.

--
Jim Pennino

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Reply to
jimp

e

like

.

That was back in the old days _pre_ peak oil.

Things might not be quite so simple post peak oil.

Some are having difficulty accepting what should be a simple concept:

Pre peak: Easy street.

Post peak: Extra labor suddenly becomes cost effective.

Bret Cahill

Reply to
Bret Cahill

Bret Cahill wrote

Wrong when batterys take so long to charge.

AND what matters is the POWER used, not the distance anyway.

Just another stupid irrelevant number plucked from your arse. We can tell from the smell.

Just another stupid irrelevant number plucked from your arse. We can tell from the smell.

Reply to
Rod Speed

Wrong, as always. They'll keep doing that using biodiesel, you watch.

You're are having difficulty accepting what should be a simple concept:

Pre peak: Easy street.

Post peak: Biodiesel leaves your pathetic little pig ignorant fantasys for dead.

Reply to
Rod Speed

The requirements of farming haven't changed since humanity howed the first row.

Without tractors most everyone will starve.

Human labor isn't an option. If it were, Africa wouldn't be starving.

--
Jim Pennino

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Reply to
jimp

That is correct, but is keeping the zinc oxide in the vehicle a big problem ?

Well, that's kind of comparing apples and oranges.

The battery drives a very lightweight electric motor, at 95% efficiency or so. The gasoline drives a heavy ICE (+drivetrain/exchaust etc), at 20% efficieny or so (if you are lucky).

The efficiency factor alone reduces the factor 34:1 to 7:1. And the motor mass difference could make up for another factor of 4 or so (simple replace the heavy ICE by battery mass). So in reality the Zi-air battery should be less than a factor 2:1 off with a gasoline driven car, and probably at par in many applications.

Advantage is that the Zi-air technology is very simple. Disadvantage is of course that an infrastructure has to be put in place to replace and recycle the Zi-oxide.

Rob

Reply to
Rob Dekker

I believe the author's philosophy is that you operate the tractor say for a half hour and then spend 5 minutes re-charging the battery---and that the cost of the tractor operator's labor spent re-charging batteries is less than the additional cost you would use with the higher priced fuel (diesel vs electricity).

--
Jonathan Grobe Books  
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Reply to
Jonathan Grobe

Very little of africa starves. Where they do, its because they have FAR more kids than their situation can possibly support.

Reply to
Rod Speed

or so (if you are lucky).

(simple replace the heavy ICE by battery mass).

gasoline driven car, and probably at par in many

You can't just look at the weight of the drivetrain/exhaust, etc--you have to compare the weight of the whole ICE car vs the weight of the whole electric car.

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Reply to
Jonathan Grobe

A 5 minute recharge, right.

Modern agribussiness doesn't run little, bitty tractors like Eddie Albert drove around on the Green Acres TV show.

--
Jim Pennino

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Reply to
jimp

gable

nds like

ier

d.

,500.

The industry has, however.

That's why electrification of agriculture is a pretty sure bet.

"Labor" here means some fat guy sitting in an air conditioned electric tractor.

Even I don't go that far.

Americans did pretty well before the first tractor.

Bret Cahill

Reply to
BretCahill

d
:

The tractor can swap out batteries after every lap and never wait.

We really need a tractor pull.

Bret Cahill

Reply to
BretCahill

chargable

like

12,500.

Yep, there's farm machinery with engines that exceed 500 hp now.

Non sequitur.

So extra labor would be two fat guy sitting in an air conditioned electric tractor for every one you used to run?

"... as many as 38 million Africans are living under the threat of starvation..."

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America had been around for less than 50 years before the first tractor.

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Jim Pennino

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Reply to
jimp

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