The Ergosphere
Tuesday, July 19, 2005


Interesting things have been happening over the last few years.  While the petroleum-dependent world chugs along doing business as usual despite the market for crude, the alternatives come quietly down in price and up in practicality.  Once the price curves cross, the situation is unstable; petroleum would still hold dominance due to the installed base, but this position would be vulnerable as users who convert lower the barriers for the rest.  As I commented on another blog:
Zinc fuel cells are already being tested in city buses; if many cities adopt them, they would function as nuclei from which a "zinc economy" could spread organically.  I haven't tried to crunch numbers on the details, but I suspect that farm equipment might be able to use zinc-air FC's also; any farmer who has energy from wind or the like could regenerate his own zinc and cut petroleum out of the budget.  That would turn farms into nuclei too.
Or, as seems more likely, a transport authority or a few farms or other enterprises in an area might spin off such work into a separate service business.  Metropolitan Metal Fuel would start out servicing just the city buses under contract, but might find it attractive to add fleets of delivery trucks and even private vehicles.  Once you have Jake's Truck & Auto Service and Zinc out among the cornfields, it seems likely that Jake would welcome transient business.

An economic environment poised for a cost-driven technological shift is not unlike a super-cooled liquid.  The colder it gets (the greater the economic advantage from changing over), the more likely it is that a crystal will form (some users will jump).  The new crystal has surfaces which allow more liquid to freeze on them (users nearby can take advantage of the investments made for the previous users).  As the crystal grows (more users switch), the surface area available for new freezing increases (more users find their barriers to switching are lowered).

This is a model with a recipe for action.  If you are a researcher at an agricultural college, see if you can't get a grant to test zinc fuel cells as power for farm equipment.  If you have a municipal transit service which operates buses, try to get Electric Fuel to run a test there.  When the results are finally ready for prime time, buy them.

Each step forward lowers the resistance for the next step.  If you want the phase of the energy economy to change, do what you can to super-cool it.

Related posts:  Zinc:  Miracle metal? 
I did some quick calculations and I come up with a 12 metric tonne zinc-air battery required to run a 150 kW (about 200hp) farm tractor for 8 hours (a bare minimum). That's a little heavy. A MF 8460 tractor at that hp is about 8.6 metric tonnes, takes 600l of fuel which should run a full farm day.

Locomotives, I come up with about 100 tonnes of zinc-air battery for a good size locomotive to run it 5 hours, which is a bit short.

It's hard to beat diesel's current (impressive) claim I see at this site of 377 ton miles/gallon (whose tonnes I'm not sure, presumably American gallons). I'd be pleased if I got a tenth of that that moving my tonne of Detroit scrap iron down the highway.

I could see SolZinc being used much more simply as local energy storage and supply. We might do better electrifying rail lines and using waste heat to grow algal bio-diesel.
One of the problems with electrified railways is the burden of adding overhead wires to all that track.  If you put the electric power supply on the train itself (a la the Green Goat hybrid switch engine) you can bridge non-electrified segments without having to burn fuel.

I did a bit of digging, and found that a typical GE locomotive weighs something around 205 to 212 tons.  If the loco towed a "battery car" with 160 metric tons of the Electric Fuel fuel cells at 200 Wh/kg, it would have 32,000 kWh of energy on board.  This would allow about 7.3 hours of full-power (4400 kW) operation, or perhaps a day's full cruising.  It would almost certainly be adequate to run a commuter train for a full day (you could probably cut the pack size down quite a bit).

The advantage of a battery car is that you could swap them out much more quickly than replacing batteries aboard a loco, and the loco could maintain its original diesel for full (non-regenerative) hybrid operation.

I tried to find cost numbers from Union Pacific.  I can't find up-to-date figures, but the ones I stumbled across showed fuel costs on the same order as salaries in the late 1990's; they'd probably be double that now.  The news reports about fuel costs eating into railroad profits and RR's imposing fuel surcharges would support that.

Electric locos would be a way for RR's to make their costs much more predictable, as well as currying favor with localities by eliminating diesel emissions and engine noise.  And once you have a zinc refuelling operation in town it's easier to pick up more customers, and so the ball might start rolling.
There is definitely a point where the overhead wires make sense. We often don't realize just how much moves by rail in some places in Europe. My tiny local train station in Zurich had 12 commuter trains an hour and saw a traffic every few minutes. Almost all of Switzerland uses overhead wires.

OK, I'd put the locomotives a bit lighter. Given that the traction engines are in the trucks (I see about 17 metric tonnes/truck here) I'm guessing most of the weight is in the engine and generator. If you developed a truck system that allowed for a fast battery swap (my brain sees a container freight-style system) or simply kept the power trucks attached during a battery regeneration you could put control systems and maybe regenerative breaking power storage onto a separate control car.
Back of the proverbial envelope is getting a work-out today.

Take a standard shipping container as a reference size with 65.5 m^3, sitting on two trucks with traction engines as the basis for the design of a power car.

Use as a reference battery the Electric Fuel bus cells as a reference point, which are about 79 l in volume and 88 kg, storing 17.4 kWh of energy and producing 8 kW of power. We can get 830 of these in our standard shipping container by volume assuming we tweak the geometry. That makes about 14400 kWh stored energy which can put out our rated 4400 kW for about 3 hours 20 minutes.

The SolZinc Rehovot experiment reactor puts out 45 kg/h of zinc, with 91.4 Wh/mol and 65.4 g/mol means about 62.9 kWh, so let's guess about 4 EV cells worth of zinc per hour per standard reactor. The researchers are looking to increase efficiency from 30% to 50%, so say we get 7 EV cells an hour of zinc reprocessed. Say we get 5 hours/day (off the top of my head) on average of adequate sunshine, that's 35 EV cells a day so we need 24, say 25 times the experimental plant to scale up to a single engine per day.

A 25x scale-up is a biggie. That says to me that the first customer should be public transit. Say, the Toronto subway system for the general electricity (CO turbine and Zn power) and trams for battery testing and work-out. With the bugs out of the system, then move up to the rail-car idea on a flattish, 3 hour route (Detroit/Windsor to Toronto would be good) with plants at both ends.

I can't find a figure for the size of the Rehovot heliostat field. Eyeballing it from the photos, I'd say maybe 100m x 100m, a hectare? That means about 60 could be put on a standard Ontario 160 acre quarter section farm lot, 240 on a full section. In theory that's enough for 10 locomotive engines per day. Maybe that's not right, it's about 7x lower than your previous estimate based on a 1km x 1km array. Hmmm... those figures are too soft.

In addition we get power for the grid from a CO burning turbine and just for fun, put up a few wind towers to annoy the neighbors and kill birds. :-)

That's a big pair of pilot projects. :-)
A standard flatcar appears to be able to hold two shipping containers with both length and width to spare.  I'm not sure a standard shipping container is a reasonable unit for anything related to rail power unless you want to be able to ship them by truck.  You'd have to limit the per-container weight to something like 60,000 pounds too (830 cells * 88 kg/cell = 73040 kg = 161,000 lbs).  Perhaps this would work as a scheme to allow replacement of spent cells in smaller units than entire battery cars.

I actually had wind in mind for the regeneration part (dissolve ZnO in acid and electrolyze to metal and oxygen), though the beauty of the zinc system is that you can use any method you like to reduce the oxide to metal so long as it comes out fuel-cell quality - beyond that, the system is energy-agnostic.

Think about that for a second.  Instead of being dependent on one source of energy for all your transport, you could "fill up" with almost anything.  Savor it.
I recall doing some calculations earlier (too tired to dig) which indicated that the Electric Fuel cell units were only about 1/7 zinc.  This is good enough for a city bus, but not good enough for farm equipment.  On the other hand, if you could get that figure up to 40% with better designs you'd cut the weight of that 1200 kWh unit from 12 tons to about 4.3.  That's getting toward the realm of reason.

Stopping to swap spent FC's for full ones would force breaks in schedules, but it's not something that will cripple mechanized farming either.  Conclusion:  if petroleum became too expensive for farmers and biofuels can't fill the gap, there is at least one completely independent option out there.  And it's already been road-tested to boot!
The Chicago Transit Authority uses an electrified third rail and it seems to work better than overhead lines.
All the heavy electrified trains seem to be using overhead lines, and they have the advantage that you can have grade crossings.  Walking into a live conductor is quite a bit harder too.

The details of getting electric power to the train are a safety and maintenance issue, but don't bear on the question of where the energy comes from.
I agree on overhead vs. third rail. You have to be completely in control of your right of way for a third rail, which rules it out for light transit that has to mix with cars and people.

I haven't had time enough to dig out a better figure than 3x output for the electrowinning of zinc from ZnO, or determine if that figure is close to the best possible. I'm not sure if that makes it worse for than electrolysis of hydrogen and H2 fuel cells or not for stationary power storage. To my mind the big win here is in the SolZinc process.

My using a shipping container was just for a guideline, although it would be a handy unit since there's already a lot of infrastructure built to handle items exactly that size. The city of Vienna is using their trams to pull freight in shipping containers. :)

Two on a "driver" flat-bed would (modulo the weight) suit the bill. Maybe use half-size containers for flexibility.
The 3 kWh/kg figure seems to be a little more than twice the amount of energy available as output, not three times.  A double-electrolysis purification seems to be adequate to explain it, and absent information to the contrary (and given the popularity of zinc batteries including rechargeable models on the way) I'm going to postulate that the losses are on the order of 10% rather than 60%.

The ideal scheme for a railroad would be a "power car" which has a tank of powdered metal or slurry, a tank of spent hydroxide, and conversion equipment.  This would be a true "fuel cell" rather than a refurbishable primary battery.  Given the rather low power/weight requirements of railroad use (a bank of Electric Fuel units holding 32,000 kWh would have an available power of over 14 megawatts), it looks like specific power could be traded off against engineering changes for near-continuous replacement of spent cathode material.
Another interesting development in the area of alternate fuels is biodiesel, especially biodiesel from species such as algae...biodiesel from algae interests many of the scientists because the yield of biodiesel from algae is almost 200 times that for conventional oilseeds!

Let's hope this is more than just hype!! Some inputs on biodiesel from algae @

NS @ IT, Software Online
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