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What energy storage system for vehicles holds the most promise?


Hydrogen Fuel Cell	454 votes - 23 %
Hydrogen burned in normal engine	268 votes - 13 %
Storage Batteries	141 votes - 7 %
Diesel	67 votes - 3 %
Bio-Diesel	653 votes - 33 %
Compressed Air	83 votes - 4 %
Gasoline	26 votes - 1 %
Alcohol	124 votes - 6 %
Other	133 votes - 6 %

1949 Total Votes

Best energy storage system for vehicles... | 75 comments (75 topical, 0 editorial)

Re: Best energy storage system for vehicles... (3.00 / 0) (#1)
by thunderhead (mail me from my homepage!) on Mon Aug 23rd, 2004 at 03:29:34 AM MST
(User Info) http://www.simon.richardson.net/mailme.htm

Like you, I'm convinced that battery electric is the way for a commuter vehicle to work: I've bought a Quantum kitcar and 20 Sonnenschein AGM batteries with exactly this in mind. It's an ongoing project, since I want to design integrated control electronics and build a garage/workshop to do the work in.

The 15 batteries option is viable in simulation, I believe, but only just. Range on the motorway (freeway) is about 25 miles, and on the back roads is about 55 miles. My journey to work is about 17 miles, so I'll get about 60% discharge on the round trip.

The batteries weigh 562kg (about 1260lbs) and even if removing engine, gearbox, fuel tank and ancilliaries loses 320kg of weight, the car will still be 250kg (560lbs) heavier when motors are included. Losing the boot (trunk) to batteries will be no hardship, as there will be a choice of rear passengers or luggage, not both.

But the Sonnenschein batteries were cheap: surplus stock at UK13 (about $24) each. If I can get 1200 cycles out of them using ZDV or pulse charging to counter sulphation, then the cost of my daily commute would be about 65p ($1.17) for the electricity and about 16p ($0.30) for battery wear. If they give the 600 cycles the manufacturer promises, they'll cost 32p ($0.60) a day for battery wear.

For most battery technologies, battery wear costs more than the electricity: which is why the off-grid people here don't recommend going "off-grid" unless you have to.

My long-term goal is to use something "Thunder Sky" lithium batteries. They are lighter, carry more charge, and are much more expensive. Unlike NiZn technology, they're available today - check out Metric Mind's website, or contact the manufacturer directly. Replacing the Sonnenschein batteries with Lithium would get me the boot back; would make the car 75kg lighter than the petrol version; would give me a range of over 100 miles on the motorway; and would cost something like $12,000 for the battery pack! Now admittedly most of that $12,000 is advance payments for future battery wear, since it will last over 80,000 miles of commuting, but it's still a lot of money. Now the electricity is cheaper, only 27p, since the batteries are more efficient, but the battery wear (if I charge every third day) still costs $6.5 (about UK3.60) per day.

For comparison, petrol in wildly overtaxed Britain costs me UK3.60 per (imperial) gallon - which lasts me about a day. So right now, before the prices shoot up again, petrol costs about the same as the best lithium batteries. Of course, as you say, changing batteries is easy.

Electric cars are viable in overtaxed Britain, but only just. In the rest of the world, where petrol is cheaper, they don't make economic sense yet. But even if I finish before this time next year, and those Sonnenschein batteries don't notice ZDV or pulse charging, they'll still last 2 1/2 years, and I'll still not need to change them before 2008. Who knows what improvements in battery technology will be available by then?

Battery wear costs much more than the electricity if you pay anything like list price for the batteries: even the Optima AGM batteries that most of the home EV community use cost something like $0.20 to $0.50 per kWh per cycle in battery wear. Which means that the storage and re-charging the grid option is unlikely to be economic, unless your grid provider has very different prices at different times of day. However, we can charge the cars at times when electricity is cheap. Our local electricity suppliers typically charge about 1/2 the rate between midnight and 7am that they do for the rest of the day - if you ask for a special meter to be fitted. That's not enough to be worth doing in terms of returning power to the grid, but well worth doing in terms of charging at night.

On the environmental impacts of electric cars and other technology, I can buy my electricity from a "deep green" supplier like Ecotricity, and get 100% wind-generated power. Biodiesel is solar powered, but growing the crop to make the fuel still requires fertilisers, pesticides, and water, all of which have environmental impacts: and still produces NOx, CO, and particularates, which case pollution in cities. Hydrogen is currently available and is made from petrochemicals, which may be why the oil companies are pushing it as "the fuel of the future": hydrogen fuel cells will be environmentally friendly, but an ICE using hydrogen will still produce NOx. Only storage systems like BEV and compressed air are capable of using deep green energy.

There are other reasons to consider electric cars than economics: one of my motivations is a wish to wash my hands of the effects of the oil industry on the poorer countries of this world. But that's a different rant, and one that doesn't really belong here.

Re: Best energy storage system for vehicles... (3.00 / 0) (#10)
by bill541 on Tue Aug 24th, 2004 at 10:12:21 PM MST
(User Info)

This is just the sort of discussion I had hoped would take place, thanks to all for the input.

I am still leaning towards the BEVs especially for commuter vehicles. I'm not sure about everybody else, but 90% of my driving is short haul stuff. For the longer trips, we are going to need a much better battery or a fuel type vehicle.

Good point on the charge times. This would be a large hurdle for vehicles going long distance, especially when we are used to getting refueled in 15 minutes. One possible answer could be removable battery packs. You pull into a station and swap the pack out for a fresh one. Each pack could have a microprocessor in it that stores all the packs history, charge level,life expectancy etc. If there were a standard pack size, then all vehicles could use the same one. What I mean by this is say a small vehicle only uses one pack, but a larger one could maybe use 3 or so packs. Then there is nothing to say that an owner couldn't charge his or her own packs. These could be swapped like milk bottles, welding tanks, propane tanks etc.

As for the disposal of old batteries, I can't think of too many that cannot be recycled. In a lot of cases it is even cheaper to make new ones out of recycled material than it is to mine and refine new mateials. This certainly seems to be true of the lead acid batteries.

I am wondering if the Aluminum battery above may be the answer to some of these questions. They should be smaller, lighter and much more powerful. Aluminum has a very high energy density.

That said, I would agree that farmers who used to be paid to keep fields fallow would be happier to grow corn or other oil bearing crops. I'm not sure if the land could support enough crops to keep us in fuel oil, but it might make a difference.

Oil will still be needed for lubrication and I think most plastics also come from the oil industry.

-Bill-

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#66)
by Phil Timmons (philiptimmons-at-yahoo-dot-com) on Wed Mar 16th, 2005 at 10:45:18 PM MST
(User Info) http://sunshineguy.net

This is really simple.

Why try to store much electric power ON BOARD the car to start with? The electric grid goes almost everywhere a road does. Electric cars can pick power directly up from the road and not even need batteries for anything more than pulling in a driveway, or around a parking lot.

But when they pull onto a public street, they could pick the power up from road material itself. The money made from selling the electric power to the drivers could be paid to the local, state, or federal government who owned the road to offset the fuel-tax loss.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#68)
by mcgivor (theprefessor@hotmail.com) on Thu Mar 24th, 2005 at 02:55:40 PM MST
(User Info)

Your batteries wont last long with those kind of discharges. You mighr want to think about a hybird car. You have an on-board generator, and a heat source, (for winter).

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#69)
by Phil Timmons (philiptimmons-at-yahoo-dot-com) on Sat Mar 26th, 2005 at 10:11:36 PM MST
(User Info) http://sunshineguy.net

Hey mcgivor,

Thanks for the note back. Did you mean that just going around a parking lot or up a drive would overly deep discharge an electric vechicle? If the primary source were the grid? (in the road). It seems like far less a load and cycle than an electric golf cart experiences.

But I suppose one could grid-enable parking lots and driveways, as well, and totally do away the batteries (or big capacitors).

And yeah, I can see where heat (and cooling) could be an issue, but since you would plenty of power available from the grid-enabled road itself, why not just use the road power for heating and cooling, as well?

I could see why one would want an Army Scout vehcile type hybrid (on board generator charging batteries and driving actual electrical motors -- as opposed to the Prius / Honda merged electric/mechanical bybrid system) for a grid-in-the-road system. That would allow you either operate on the grid enabled roads or beyond them.

But if you wanted to mostly stay on grid-enabled roads (most folks drive in or around towns), you could have a really cheap car with no mechanical engine (or fuel) at all.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#2)
by Wolfie1 on Mon Aug 23rd, 2004 at 08:24:49 AM MST
(User Info)

One question I would like to know is, is there an alternative product that can be simply made with electricity other than hydrogen. Thake for example methanol:-

2CH3OH + 3O2 -> 4H2O + 2CO2 + energy(heat)

Is there some way to do a reverse reaction and build something useful (ie make some sort of fuel).

Perhaps methanol is a bad example but I'm just guessing that anything with more than one carbon atom will be too hard to make. I know that the plant kingdom does this every day with photosysthesis but I wonder is there is some simplier reaction that can be done.

Making a liquid fuel using heat or electricity seems to be the "holy grail" in alternative energy to me.

Martin.

Re: Best energy storage system for vehicles... (3.00 / 0) (#23)
by Roamer195 on Fri Aug 27th, 2004 at 03:00:04 PM MST
(User Info)

You can very efficiently apply heat to lye(sodium hydroxide) and
use the energy to liberate it's oxygen molecule, leaving you with
sodium hydride.

For fueling your vehicle, you carry a special tank full of water
and a container of plastic coated hydride pellets.

A mechanism cracks the pellets into the water where the hydride
grabs the O2, liberating pure hydrogen gas and leaving sodium
hydroxide solution in the tank.

Pellets are released into the water as needed to maintain a fixed
H2 pressure range in the system.

Hydroxide solution is reclaimed and turned back into hydride for
re-use.

http://www.powerball.net/business/index.html#

You don't need to maintain much pressure so there are no heavy
tanks needed.

The best part is, it's already being done. People just need to be
informed.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#64)
by plantiful on Tue Feb 15th, 2005 at 06:01:03 AM MST
(User Info)

Where will the energy come from to make this 'alternative fuel'? In order to reverse the chemical reaction, it will take in more energy than the fuel itself will provide, since few chemical reactions actually approach 100% yield. Also, everytime the form of energy changes, there are losses. The Electric Vehicles that are (were) being promoted in the United States (see tax code), actually are more wasteful than they appear: oil is burned to produce mechanical energy at the power station, the mechanical energy is then converted into electricity (magnets), transmission of electicity, then in the battery it is converted back into chamical energy. During use, the chemical energy int the battery is turned into electricity, and then finally mechanical energy to move the car. Twice as much fuel is probably (just a guess) consumed by the time the car actually gets to move compared to a regular gasoline-powered car.

Hydrogen is a good, safe storage medium for energy: if it leaks, it goes straight up into the atmosphere (see http://www.3nw.com/energy/hydrogen_car_fire_surprise.htm) whereas gasoline leaks under objects and then ignites them. It can be produced using Solar Thermal energy, which has greater efficiency than electrolysis (see http://www.shec-labs.com). These guys are using a metal catalyst to separate the water at a lower temperature (~600C) than without the catalyst (~2000C).

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#70)
by Peter V on Tue Apr 12th, 2005 at 02:26:34 PM MST
(User Info) http://www.vanderwal.us

First of all, oil is only used to produce a small portion of the power in the US. The vast majority of electricity in the US is made from coal.

Regardless. Let's assume we ARE using fuel oil to generate electricity. New power plant can reach 60% efficiency converting oil to electricity. Your average car, on the other hand, is about 15-20% efficient. Power line transmission is about 95%, a typcial battery charger is about 75-80% (could be higher, just costs more), batteries are about 75% energy efficient, and a good EV drivetrain is about 90%. Total EV efficiency oil to road is 25-30%. i.e. slightly better than internal cumbustion engine (ICE) powered cars.
EVs can also run powered by sunshine, wind and rain (solar, wind & hydro) something than no ICE can match.

Finally power plants tend to be way out away from cities, this moves the polution away from the areas that people are trying to breath. And it's much easier to control/reduce pollution at one fixed source, than thousands of small mobile sources.

Finally EVs can charge at night (and most will) which is when the power companies have a surplus of power so this will help them produce power more efficiently since they won't have to ramp up as much in the morning and slow down as much at night.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#3)
by DanB (danb@*no spam*otherpower.com) on Mon Aug 23rd, 2004 at 08:28:53 AM MST
(User Info) http://www.otherpower.com/

"Bio-Diesel - Looks great if you don't mind collecting the oil at your favorite greasy spoon every week or so. I must say the smell of french fries from the exhaust pipe is much better than the smell of pump diesel."

I disagree... I think it looks great period...
It would keep farms in action... the govt. could subsidize it to some degree (we do this for oil, we do it for Ethanol ... ethanol requires more energy to produce than you get back out from my understanding).

Biodiesel is not the small scale sort of thing we have to raid restaurant dumpsters for... it could be a huge scale thing we grow crops for. Its more efficient than gasoline, its renewable - the CO2 released from burning it is reclaimed in the process of growing crops. It makes a lot of sense and the technology is here now.

At least thats how it seems to me. Could be there is a place for diesel hybrids... but it seems today, that the late '70's diesel rabbit does almost as well as the new gasoline hybrids.

compressed air is a horribly inefficient way to store energy I think, I would be surprised if much ever came of that (although its neat). it might be useful someday when we have more power available than we know what to do with...

hydrogen is a futuristic pipe dream in my opinion...
its a long long ways from being practical - I suspect if our current administration hadnt brought it up we'd be hearing much less about it. There are so many problems to overcome. Perhaps in 50 years...? (I bet it takes longer)

Re: Best energy storage system for vehicles... (3.00 / 0) (#8)
by LEXX on Tue Aug 24th, 2004 at 02:54:47 PM MST
(User Info)

Imagine if 50% of all cars in north america were using bio diesel. How many farms would switch over to producing canola instead of wheat if there were government subsidies? How much would this drive up the price of all food? In a world that already has millions of people subjected to famine is this really the best national enterprise? Maybe if we let the price of diesel get to the point that farmers need to start making their own biodiesel for the tractors to run on and it stays a private enterprise the shift won't be too dramatic. Tho biodiesel does look like the easiest way to do the switch, you could have stations like in the early eighties where there was leaded and unleaded, you could have bio and non bio. hopefully the auto industry picks up on the feasability and first off starts making more vehicles with efficient diesel motors (honda and toyota would be perfect), then the choices will be open.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#71)
by Peter V on Tue Apr 12th, 2005 at 02:46:14 PM MST
(User Info) http://www.vanderwal.us

For what it's worth. I did the calculations once, a couple years ago, based on the total farmland in the US and expected yields from oil bearing crops. Even if we quit growing food and switch entirely to growing oil, we couldn't produce enough bio-diesel to offset 25% of the crude oil that we currently import.

So bio-diesel isn't THE answer, but it could be a valuable part of the answer. We currently spend millions paying farmers not to grow crops. It makes much more sense to pay them to grow bio-fuel, in essence we would get the oil for free since we are already wasting the money on NOTHING. And it wouldn't effect current food production since the land in question is currently producing NOTHING.
Plus we could recycle a large portion of the used vegetable oils and animal fat that is currently being disposed of as "waste".
Finally, the waste product from canola oil production is a viable food source for cattle. You could therefor reduce the amount of acreage currently used for cattle feed and switch that over to oil production too.

Combine this with ultra efficient diesel hybrids (100-150+ mpg?) that are within our current technological ability and it would make a (small) dent in our consumption of non-renewable fuels. Not to mention a drastic reduction in the vehicle polution.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#26)
by nack on Tue Aug 31st, 2004 at 01:59:57 PM MST
(User Info)

Bio-diesel in the US already is huge, that's one of the major obstacles to people actually using it. Backroom deals between oil, soybeans, and government regulators have managed to set assinine policies that seem quite able to quell the interest in it. Basically it has been relegated to use as an additive to lubricate injector pumps now that sulfur levels are too low to manage that feat. The only real hope is for the grassroots homebrewing types to infect the rest of the US with sensible philosophy and a real desire for self-reliance. Most US public policy on business and education for the last 150 years has been geared towards addressing the "American capacity for over-production" - something that terrified the industrialists that really got behind mandates for compulsory schooling and helped to design the models that are used in primary education. Now we've evolved to the point where over-production is clearly no longer an issue and any production is increasingly doubtful. We have gone from being net producers to net consumers, and then decided that we can get by just fine as a "service economy" supplemented by the occasional stock kiting racket.

Oops, I seem to have drifted off topic. The best energy system for vehicles probably would be a battery/fuel cell hybrid that uses the batteries to soak up load spikes and to recapture energy from braking. As for the fuel cell side, either the lye->hydride->lye+H2 process or methanol for fuel storage. It is my understanding that methanol fuel cells don't really look that bad, but regulations prohibit carrying enough methanol to get the job done.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#67)
by daleh007 on Thu Mar 24th, 2005 at 04:03:06 AM MST
(User Info)

Just wanted to jump in with my 2 cents. This country has a definate dependence on foreign oil. With that in mind, how much diesel oil is consumed each day by semi trucks? If the trucking industry were provided incentives to use bio diesel or some portion of bio diesel how much petroleum could be freed up for other uses. I see someone mentioned that you need methenol to make bio diesel and another comment that it can be derived from NG or methane. My father used to work at a sewage treatment plant years ago where they had 3 large stacks burning 24/7 to get rid of the methane generated by the treatment process. Seem's to me like there are pieces of this puzzle laying all around us and we need to put our heads together and get politics and big money interest moving in the correct direction.
Daleh007

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#72)
by Peter V on Tue Apr 12th, 2005 at 02:54:06 PM MST
(User Info) http://www.vanderwal.us

FWIW the government finally did something right. They recently passed a federal law that gives up to $1 per gallon tax rebate to encorange the production of bio-diesel.

The law is mostly intended as an incentive to the folks that 'mix' the biodiesel with dino-diesel. However, it contains a clause where it can be applied at the individual level. Bassically if you dispense 100% biodiesel into a road going vehicle, then you are eligible for the full $1 per gallon rebate. Of course you'd also have to pay the fuel tax, but that's only about $.26 a gallon.

So, for those of you that make your own biodiesel, I'd reccomend you look into this. It could be worth a big chunk of change come next Apr 15th.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#4)
by Wolfie1 on Mon Aug 23rd, 2004 at 09:00:40 AM MST
(User Info)

Dan, I agree that biodiesel is the best we have come up with so far but I still have a few issues with it.

Biodiesel is made from some sort of oil, methanol and sodium/potasium hydroxide. The oil is the easy one to "make". Sodium hydroxide, I believe, can be extracted from wood asses but the problem is with the methanol.

I believe that you can get some methanol from pyrolysis of wood (along with a lot of other stuff) and you also get some when you ferment sugars but neither yields much for the effort put in. I'm sure that the industrial way to make it is to start with methane or oil and go from there.

I'm not sure where this post is going so I will just ask, where do you get the methanol from?

Martin.

Re: Best energy storage system for vehicles... (3.00 / 0) (#5)
by DanB (danb@*no spam*otherpower.com) on Mon Aug 23rd, 2004 at 09:41:07 AM MST
(User Info) http://www.otherpower.com/

Yes, I tend to agree... everything has its pros and cons.

Biodesel does seem to make a lot of sense though. Im not sure how methanol is usually made...
I wonder how much is required to makeup biodiesel...? My understanding is that methanol is simply "wood alcohol".

My understanding is it burns much cleaner than petro - diesel, and to me it seems like the only real viable alternative we have before us.

I think storage batteries/electric cars make some sense... but the idea of millions of folks wearing out large battery banks on a regular basis is a bit scary!

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#13)
by ibedonc on Wed Aug 25th, 2004 at 07:39:05 PM MST
(User Info)

Methanol is a by product of Natual Gas , that is what my Methanol Supplier told me

and NG is Methane

but can also use ethylanol and that can be made from grain

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#41)
by chux0r on Thu Sep 16th, 2004 at 08:05:56 PM MST
(User Info)

I'm sorry.... "wood asses?" :)

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#73)
by Peter V on Tue Apr 12th, 2005 at 02:59:20 PM MST
(User Info) http://www.vanderwal.us

Methanol isn't a "requirement", there are other chemicals that can be used. Ethanol for example. Methanol is just one of the easier ways to make biodiesel, that's why it's popular with the DIY crowd.
Also the methanol/ehtanol/etc. is used as a catalyst. That means that it's possible to recover most of it afterwards. For small scale production it's usually to much hassle for folks to bother. In large scale production, you can bet that they are going to distill the methanol/etc back out afterwards.

My big question is what will they do with all of the glycerine produced as a waste product. Small scale you can burn the gycerine for heating etc, but large scale?

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#6)
by DngrDave on Mon Aug 23rd, 2004 at 10:50:25 PM MST
(User Info)

The biggest downfall I see in batteries is not the cost, mass production would solve a lot of that (although someone already mentioned disposal would create a headache) and currently weight is a big issue, but I'm sure mass production and necessity would overcome that too. The biggest issue that I see with batteries is charging time. BEV works fine if you're building a commuter car. But people don't want a commuter car. Cars are typically the biggest investment a person makes other than their house. There are a million other social stigma's that go along with cars too, but the bottom line is the longest you can hope to run a BEV is a hundred miles and then you have to charge it. I live in Dallas / Ft Worth TX, 100 miles doesn't get me to the next large town.

I'm going to have to go with Hydrogen fuel cells. They're light, simple, can be filled quickly and getting cheaper all the time. Electric / PEM (fuel cell) systems are simple, people will be able to work on their own cars again! There are several city's in North America that run bus systems with them already. www.plugpower.com is probably the most commercial site I've seen, (Stationary PEM) but there's a wealth of info out there on the web. I even bought my own fuel cell system at the local electronics superstore a while back, a small for classroom demonstration type. Liberman mentioned them in the debates leading up to the 2000 election.

For distribution of hydrogen look no further than our already existing grid. Run power INTO a fuel cell with water on one side and it produces hydrogen and Oxygen. Even so this is a high tech method, two electrodes in a pan of water will do the same thing. The infrastructure is there, we just need legislation to add a "hydrogen appliance" in the place of a gas pump.

There's one key missing. Even if GM, Ford, and Chrysler were required to offer a PEM Electric power plant in all their vehicles within 5 years, and every gas station was required to install a "Hydrogen appliance" to meet that demand, we would still be dependant on foreign oil. The simple fact is we use foreign oil to produce a large percentage of our domestic electricity. Domestic coal makes up another big chunk of the pie, and nuke makes up a bunch too. (even though a new plant hasn't come online in 20 years) Renewable is a very small percentage. We still have to produce the electricity.

I have to agree that our biggest hope is Bio-diesel. My second cousin runs it in all his tractors at his farm in Southern MN, he says it works great. SVO (straight vegetable oil) works great too, as long as you keep the temperature up high enough to keep it fluid. I propose government subsidy that would make grid tie PV, micro-hydro, and wind systems profitable for Joe homeowner, set the farmers to work growing as much vegetable oil as they can, make it illegal to dispose of fryer waste in a manner other than running something i.e. fine someone for dumping it. Then cross our fingers and pray it is enough to satisfy America's appetite for more, always more.

Re: Best energy storage system for vehicles... (3.00 / 0) (#7)
by thunderhead (mail me from my homepage!) on Tue Aug 24th, 2004 at 03:39:57 AM MST
(User Info) http://www.simon.richardson.net/mailme.htm

Cars are typically the biggest investment a person makes other than their house. There are a million other social stigma's that go along with cars too, but the bottom line is the longest you can hope to run a BEV is a hundred miles and then you have to charge it.

The Tzero and the Jester both do 200+ miles with lithium batteries.

Add a small on-vehicle engine (like the Renault Kangoo Elect'road does) and you can travel as far as you like, albeit at some reduced speed (like maybe 55mph). You only turn this engine on when you are planning to go out of town, unlike things like the Prius.

You said "social stigmas" - the biggest social stigma with electric cars is people who don't realise the technology is coming through now.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#9)
by DngrDave on Tue Aug 24th, 2004 at 04:53:43 PM MST
(User Info)

Let me start out by saying I'm playing devils advocate here to a certain extent. One of my near future goals is to actually build a BEV car (more likely a small pickup) and charge it with wind, PV if I can afford it and a three phase generator running on SVO (Straight Vegetable Oil) reclaimed from restaurants if mother nature fails me. So I mean no disrespect, just looking at it from a typical American perspective.

200+ miles between an 8 hour fill ups still doesn't get you cross country. How much do the lithium batterys add to the price tag of the car, where do you dispose of them, and how long can you expect them to last? I have a '76 dump truck, the old girl is still running strong, I paid $2,500 for her. Top speed is about 55mph, and I'm confident that I could make it cross country with the old girl... and I can take along just about everything in my house. I would never do so though... why? Because it would be terribly uncomfortable, no leg room, the slow speed would probably get me rear-ended on the open highway, and shot in the city. The performance (except in tight maneuvers it's a big truck) is about the same and from a cost perspective I could drive that truck to work for three years, sucking down gas at $3.00 a gallon, and come out close in total price. (If someone wants to do the math I go about 10 miles on a gallon, and make no payments)

What I was referring to when I mentioned "social stigmas" was that the vast majority of the population wants a car that is comfortable, peppy (if not outright powerful) and usually big. I bought a Honda Civic Hybrid a while back, it didn't take me long to trade it in for an Accord. When I did the math of how much more the car cost than a regular Civic, and then figured out the price of gas, and the distance I expected to drive I figured that gas would have to go up to $3.25 a gallon for me to break even. Add to the equation that the car was basically a tin can, and I'm a medium to large individual, and I just couldn't see paying extra to be uncomfortable. It's a fact of life that the rest of the population feels the same way, how else can you explain the popularity of Hummers, Excursions, Expeditions, and Suburbans, not to mention the 50 or so other types of four wheel SUV's that will never make it off the pavement.

I have heard rumors that Ford plans to put out a Hybrid Exploder, but I'm not holding my breath. The general public has issues stopping for red lights, observing double yellow lines and merging in their hurry to get home from work, the only way they'll buy anything but a token amount of electric, hybrid, or other vehicles is if nothing else is sacrificed... or if gas prices go up to $5 a gallon. Even so it will be less than a decade before we're back to the big cars, just like in the 70's when gas prices spiked and everyone started buying small cars, and scraping their V8 land yachts. You'd be hard pressed to find a car with a 400cid or larger engine today... but I'll bet you can buy a SUV with one. So we should apply C.A.F.É. to SUV's right? You bet, but it won't be the end of it... you'll see more four door pickup trucks. Anything under 1 Ton capacity? I see people drive 1 ton four door trucks to their office job all the time. We have to switch the fuel. And even then it's going to take us 20 years to work gasoline out of our system.

Show me a battery that charges in fifteen minutes on 220vac, doesn't cost thousands of dollars, and will run six hours without weighing a ton and I'll partner with you to be the next Bill Gates and Paul Allen. I can build an electric vehicle that will pull a semi truck, 80mph using cheap off the shelf parts, I just can't get enough extension cords to power it.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#11)
by thunderhead (mail me from my homepage!) on Wed Aug 25th, 2004 at 03:01:40 AM MST
(User Info) http://www.simon.richardson.net/mailme.htm

My BEV car will be a Quantum coupe - a glassfibre kitcar body that is about the size of a Ford Escort. I have the car, I have the batteries, I just need to build the electronics, buy the motors, and construct the garage to do the work. I guess it'll take me about 12 months. My wife wants me to fit a new kitchen and bathroom first - you know how it is.

One big difference is that around here petrol is 80p a litre: about $5.80 for one of your gallons, or about $6.60 for one of ours. I'm planning to do this to save money: about UK4000 - call it $7000 - over the three years the batteries last. I was planning like you to use wind power to charge it. The bad news is that I don't have space for windmills, but the good news is that I can buy wind power off the grid for 2.5p (call it five cents) a kWh.

That saved UK4000 would buy me a replacement set of Chinese lithium batteries (at today's prices, which will likely fall), which would then last at least another five years: and give me that 200 mile range, if I wanted it. Of course I didn't pay "list price" for the current set of batteries - a story that I suspect is pretty familiar to the regulars here.

If the "hydrogen economy" takes off the way that Bush's buddies would like it to, and ends up with a source other than petrochemicals, I could replace (or supplement) the batteries with a fuel cell. As it is, switching to lithiums would leave enough weight over to put in a generator, that would give me a continuous speed of 40mph or add 50% to the 70mph range.

My simulation predicts a car capable of 76mph, 0-60 in 10.2 seconds, and a standing quarter in a shade over 18. Switching to lithium batteries keeps the same top speed, but gives 0-60 in 7.3 and a standing quarter in 16.5. They're significantly lighter, as well as giving more than double the range. I'd consider that sufficiently "peppy" for my drive to work, although the folks at your National Electric Drag Racing Association would consider it pretty pedestrian.

http://www.nedra.com/record_holders.html

Recharging will be as fast as the grid provides power. Here in Britain our biggest socket in common use is a 30A supply at 230V - that'd take 2 hours to recharge my current batteries after my daily commute. If I wanted to get the electricity company to provide 3-phase current - unusual for a domestic supply, but maybe worth doing - then the industrial standard 32A socket in "star" configuration would do a full recharge in a bit less than an hour, or refill my commuter charge in 30 minutes. I'm not sure what it takes in "delta" configuration, but there are people here who are more up-to-date with three-phase maths than me.

As it is, I only commute once per day, and I don't drive in my sleep: I'd probably be happy with a plain old 13A supply, and accept that it takes five hours to charge after my day's commute. The cheap electricity is available between midnight and 7AM anyway, so that makes sense. If I were using it as a taxi or an agricultural vehicle, then maybe that three-phase supply could be used to "refill" on my lunch break. A farm or a taxi depot probably has three phase already fitted. But for my use, it's not worth the trouble of getting the electric company out to dig up the road.

Range is not the issue that people think it is: if we want to go visit my relatives in Scotland, we'll take my wife's car. She only drives it once or twice a week anyway, so we don't mind leaving it on dinosaur juice. Or you can rent a lot of cars for UK4000.

Yes, you're right, the attitudes of drivers needs to change. But the economics makes sense when you're paying $6 a gallon for petrol, which we are here in happy Britain. In due course, Iraq or no Iraq, you'll be paying the same over there. (My brother works in oil prospecting - he knows the score. It's not good news.) When you are, the electric car technology you switch to will be European and Asian, because we'll be 10 years ahead of you.

Sorry about that. Try not to elect an oilman President next time. ;-)

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#12)
by DngrDave on Wed Aug 25th, 2004 at 03:13:03 PM MST
(User Info)

Sounds like you have a pretty good plan thunderhead. Things are a LOT different over there in GB. I was in the Army with a Scott, she said it took her a while to grasp the concept that driving from one coast to the other in the US isn't an option... point being you really don't have as much of a need for high range. That and the high price of "petrol" in Kings English makes electric (BEV in particular) cars much more marketable. Your culture is also a lot more accepting of smaller cars... I'm surprised Cooper, MG and the lot aren't in production already.

I'm not too worried about the US being behind in the technology... it's there. As I said, I worked on electric lift trucks (forklifts if you will) and the technology is there. One I worked on had a max gross weight of over 200,000 lbs. Only two electric motors, 72VDC, and the motors would fit in a hat box. I dropped by the old shop the other day, and they now have AC powered lifts. Running from an inverter I assume. The guys said when they first came out operators were dumping product all over the place, as the AC motor would lift so quickly that when the fork carrage hit the end of the first stage things would jump off the pallet.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#14)
by LEXX on Wed Aug 25th, 2004 at 08:06:08 PM MST
(User Info)

"I'm not too worried about the US being behind in the technology... it's there. As I said, I worked on electric lift trucks (forklifts if you will) and the technology is there"
The tech is there for for lifts and cars and such but imagine a semi or (heaven forbid) a boeing 747 operating on batteries. What about transport freighters? The fact of the matter is that within 20 years there will really be no oil to power these things, i'm not saying that it won't exist but the energy expended to get it out of the ground and refine it will be more than what you recieve. Personnally I feel the world will once again become quite large compared to the one we live in now that you can go halfway around it in 18 hours. Do you really think that the concord shut down because of people not wanting to fly, no it just takes too much fuel, it was the first but it won't be the last. Wow, that sounds way more doom and gloom than it was supposed to! Anyways, we need to find a new way of doing things or we're in for a big shock.
LEXX

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#15)
by thunderhead (mail me from my homepage!) on Thu Aug 26th, 2004 at 02:59:22 AM MST
(User Info) http://www.simon.richardson.net/mailme.htm

Aircraft are more sensible for hydrogen power: there are so many safety systems in aircraft, they are normally maintained to a very high standard, they're not fuelled then parked for days or weeks, and frankly an air accident is normally a zero-survival event anyway. If someone drives your airliner into the side of a mountain at 600mph, fire is not something you will worry about. (Nor will you worry about anything else: nerve impulses travel a lot slower than 600mph, so your brain will be burger before you get a chance to notice.)

Electric motors and batteries are used for locomotives. The repair trains for the London Underground use batteries. For battery electric trains, range is an issue but weight is not.

For forklifts, weight is an issue but range is not - you don't have to worry about getting home when the batteries run out, since they don't ever leave the warehouse.

Battery cars need range and low weight, or they will be impractical.

The main technologies I have in mind are batteries (the best lithium batteries are being developed by SAFT, who are French, and Thunder Sky, who are Chinese); and motors (some of the best motors, using rare earth permanent magnets, are developed by Lynch, who are British, or Siemens, who are German). You'd get three or four of the Lynch motors into a hatbox.

The Siemens ones are AC, and they're driven by a 3-phase invertor, which leads to increased reliability but a loss of efficiency: about 88% as opposed to 90%+. It also makes it rather harder to do regenerative braking.

The Thunder Sky 200Ah battery weighs 12lbs and stores something over half a kWh. At 6 miles per kWh, 50 of those give 175 miles range from a battery that weighs only 600lbs. Unfortunately they are $240 apiece, or Trojan would be out of business.

The AVT variation of the Lynch motor (the one I fancy) weighs about 25lbs and generates over 45 horsepower. Two of those in a compact car should move pretty good.

There is nothing in production by US manufacturers that will compete with these two products. But with your low "gas" prices, you don't need it. For now.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#18)
by bill541 on Thu Aug 26th, 2004 at 10:13:39 PM MST
(User Info)

Wow, $5.80 a gallon for gas, that is high. I would think you would not have a problem justifying the expense of any type of alternative fuel vehicle.

I noticed that a lot of vehicles run on diesel over in Europe, is the price of diesel just as high? Where I live, it is at $2.17 a gallon at the moment. Fuel prices are going up and down like a yo-yo anymore. The fuel companies really stick to us around the holidays.

Our biggest home type receptacle is typically 40Amps @ 240 volt split phase. But the service into the house is usually a 200A 240V split phase. But like you say a smaller charger only takes a bit longer to do the job. If everybody jumped on the grid at the same time with huge loads, this could cause a problem. Besides I have always been an advocate of slow charging.

Take care, Bill

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#22)
by thunderhead (mail me from my homepage!) on Fri Aug 27th, 2004 at 02:44:20 AM MST
(User Info) http://www.simon.richardson.net/mailme.htm

I don't buy diesel, but I seem to recall it's about 85p a litre, which is about $6.00 for one of your gallons or about $6.90 for one of ours. Most "alternative fuels" (in particular biodiesel and LPG) are also taxed. Hydrogen will also be taxed when it is available for use in cars. It's hard to tax domestic electricity, because people use it for other things. But "put not your trust in princes" - they'll find a way to tax EVs if they get popular!

In London you pay UK5 (about $9) a day just to drive your car into the centre of town. This is the famed "congestion charge" - which incidentally resulted in our prime minister getting over 1000 pounds in fines. That charge is waived for electric cars, which is another temptation.

All our systems are 230v, and most domestic supplies have a "company fuse" the other side of the meter which allows between 50A and 100A to be drawn. Our largest single-phase receptacle is a 30A one, which is the normal limit for a single spur using UK wiring (normally called a "cooker point"). The only wiring that requires more than this is typically an electric shower, and electric shower manufacturers advise you to check with the utility company to make sure your fuse is up to it.

The "overloading the grid" fear is valid: here in Britain at least 30% of the nation's energy goes on transport. If everyone switched to electric cars, the electricity requirement for the nation would double. Cheap rate electricity is at least part of the answer. Here in Britain electricity costs about 6p per kWh, but only 2.5p per kWh between midnight and 7AM. That is because the generators have spare capacity. The solution is to time the charge cycle to begin at 1AM, when you're not driving the car because you're asleep, and let it be mostly finished by 7AM. (I'm not worried about "finishing charging", which is only done to improve cycle life and capacity - it is the bulk charging that sucks amps.) That saves money, but it also saves the grid, since nobody else wants the electricity anyway.

The biggest cost of a BEV is battery wear. Since the batteries are normally quickly and deeply discharged, they'll typically deliver between 300 and 1000 times their total storage capacity before they're junk. They're hit hard: at 75mph my Quantum needs between 15kW and 25kW to push it down the motorway, depending on wind and slope. For a 180v system that's up to 140A. When I stamp my foot on the go pedal at the lights, I'm expecting the peak current to reach 1200A.

They also (almost by definition) spend a large amount of their time partly discharged, since here in Britain I'll drive to work, park the car away from power at 30% discharge for nine hours, then drive home, and leave it 60% discharged for another six hours while I wait for the cheap rate electricity to start. It's a hard life being an automotive traction battery. I know that in the average "home power" setup the batteries would last for a decade or more, but if I get three years out of these batteries, I'll have won.

Slow charging is a non-starter, I'm afraid: if you charge at C/20, it takes nearly a day to recharge your batteries. The charging algorithms are going to have to be of the bulk then finish variety, or the car can only be driven every other day. One recommended (by the manufacturer) algorithm for the Optimas is to charge at C rate (so maybe 15kW) until the temperature rises to 50C! As I said, it's a hard life being an automotive traction battery.

The Trojan batteries that are the mainstay of home power systems are flooded, and don't belong in a moving vehicle. Optima "yellow tops" deliver 1000 times their total capacity when discharged to 30% DoD each cycle, and 400 times at 80% Dod - Thunder Sky lithiums deliver 750 times their capacity at 50% DoD and 400 times at 80% DoD. That could maybe be improved with clever charging algorithms, but in the end it provides a limit - and it's a part of the "total cost of ownership" that can't be ignored. If you think that my simulations are expecting about six miles per kWh at 40mph and four miles per kWh at 75mph; Optimas cost about $310 per installed kWh and Thunder Sky about $420 per installed kWh, you can see what they cost per mile (Optima $0.05 to $0.19, Thunder Sky $0.09 to $0.26). Add on to that the cost of electricity in your region, adding 10% to 20% for charging losses.

Now engines and gearboxes wear out too, but they are not as expensive as replacement batteries. Fortunately I bought my battery for UK250, which will make battery wear negligible. But I'm going to be saving that money I'm not spending on petrol so I can afford to replace the battery when it wears out after three years' usage. Interestingly, the batteries I'm replacing will probably be fine for an off-grid system, since they'll still have about 50% of their capacity and they'll probably recover when float charged for a few months. So the change-over to EVs may have spin-offs for the home power people, in the form of lots of batteries available for skip-divers. :-)

For comparison, the hydrogen powered buses they're using in central London have a fuel cell that brings the total price up to somewhere around the $200,000 mark. Modern fuel cells use precious metals (platinum for instance) which makes them very expensive. Since they're prototypes, nobody really knows how long they'll last, or what the effects of impurities in the fuel or air will be. But you could buy a lot of diesel for $200,000 even at our prices.

In summary, even with petrol at our price, BEVs make sense only if you have the right batteries. The lithiums are marginal. The alternative SAFT lithiums are about five times the price, and so are completely uneconomic. Fortunately there is a government scheme to subsidise the cost of new electric vehicles (it's called "Powershift", and no, it's not available to home constructors) but even then things are barely competitive.

The driver for alternative energy cars will be fuel prices. When the oil runs out, everyone will be paying for motoring about the same way the British are now. Before that happens, for most of the world BEVs will not make economic sense.

Neither will the other alternative technologies.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#24)
by bill541 on Sat Aug 28th, 2004 at 02:37:27 PM MST
(User Info)

thunderhead,

Have you considered using a battery/capacitor hybrid system? These are being used in fuel/electric hybrids now, but could they be an advantage for BEVs as well?

Electro-chemical double-layer capacitors AKA ultra capacitors or super capacitors have a very large power density for both charge and discharge. When used in conjunction with a high energy density battery, the combination would be able to provide high acceleration as well as capturing a very high percentage of regenerative braking energy (Something a battery alone does not do too well). As far as I can tell, by providing a better means to supply/store peak currents, the battery life and range should also be extended.

It seems there are a couple of types of these capacitors, Asymmetrical and Symmetrical. The Asymmetrical units do not require balancing networks when used in series, but cannot be discharged fully under normal use. The Symmetrical units require balancing networks, but can be discharged fully under normal use. Both types seem to have a cycle life of 10,000 to 100,000 and beyond.

A Canadian company called Tavrima makes these capacitors for EVs and hybrids. Seems that a few electric drag cars use them without any batteries at all. Good application for a high power density device.

http://www.tavrima.com/home.html

Yet another company called JEOL has developed an epoch-making capacitor (Nanogate Capacitor) with an energy density of 50-75Wh/kg, which is on par or exceeds some batteries and has a cycle life of around 10,000. They have now formed a new company called Advanced Capacitor Technologies, Inc. This technology is still in the laboratory and not in production. I have a feeling this will be a very costly unit.

Michio Okamura of Japan has been working with specialized electronics used to get the most out of "super" capacitors used for energy storage. They call them Energy Capacitor Storage Systems (EcaSS). He has his own web site that is very informative about his work.
http://www.okamura-lab.com/ultracapacitor/edlc/ecass1Eng.htm

I think you would need to size the capacitor bank to match or slightly exceed the energy requirements for acceleration and braking. Then the battery bank is mostly used for the range requirements.

Seems to me that either the capacitor or battery industries are close to a good solution, or maybe a combination of both. The capacitors do have the great advantage of being able to be charged very quickly.

-Bill-

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#25)
by thunderhead (mail me from my homepage!) on Tue Aug 31st, 2004 at 02:47:05 AM MST
(User Info) http://www.simon.richardson.net/mailme.htm

I looked into ultracapacitors, but I concluded that they were probably not going to be worth their expense and weight. (MetricMind sell them.) For hybrids like the Prius, where the energy only needs to move you along the queue at the lights, they're a good idea, since they have a huge cycle life.

They're a better idea for lithium systems than for lead-acid, as lead-acid is actually very good at delivering high power on demand. The units I've bought are claimed to deliver 3800A at peak. Since I only paid UK260 (about $470) for the whole battery pack (including five spares) I think it would be difficult to justify the expense.

The other area they're worth considering is regenerative storage: but the area where I live is not particularly hilly, and I'm expecting to be able to develop my own electronics to give good regeneration characteristics.

One problem is that the most simple circuit for controlling motor current is a "buck" circuit, where a switch and an inductor are used to step down the voltage. During the off phase the battery is not connected, and the current is "stored" in the inductor, but during the "on" phase the battery must deliver the same current as the motors require. This means that when I stamp my foot at the lights the motors may be getting 1200A, but that is only going to be at about 40v (largely resistive), which means that a 180v battery will only be drawing an average 270A or so. The problem is that each motor controller will draw 600A at times, so if they both come on at the same time they'll draw 1200A.

The solution is to use a pseudo-random generator to gate the current sense, (which also means the motor windings hiss instead of whistling) and to use several smaller current control modules. It is a property of the type of pseudo-random generator that different modules can be connected to delayed versions of the bit series, which means that if there are 6 100A modules per motor, only 2 or 3 of the 12 will be on at any given time, even at that peak load. That reduces the load on the battery considerably, but uses the inductors as the energy storage devices to smooth the load.

A similar argument applies to regeneration. Now we use a "boost" circuit rather than a "buck" circuit, but again the current comes in peaks. These peaks are averaged out by using the delayed pseudo random sequence, which enables the batteries to be charged much faster, since the maximum charging current limits the average power, not the peak motor current. This should enable me to recover much more energy on downhill stretches.

That should enable me to get by without ultracapacitors, since the motor inductors will be fulfilling the same role.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#27)
by bill541 on Tue Aug 31st, 2004 at 10:02:59 PM MST
(User Info)

Thunderhead,

That is interesting, most of the DC EV motor controllers I have seen are a simple low side switch employing either FETs or IGBTs. These require the motor to be able to handle the highest battery voltage. They all seem to use PWM to control the motor speed. I have seen some very nice designs that use multi-phase switching (6 phases in some cases), where each Fet is only on for a portion of the PWM output pulse. This way, they can run at a nominal 15 KHz or so, but since each Fet is on at a different time, it has the effect of increasing the ripple frequency and it allows them to use smaller input and output capacitors as the ripple is much easier to filter. This also pulls current from the battery at a more constant rate.

I have been thinking about the regenerative braking, from what I understand, you waste about 30% of your power in braking. Out of the 30%, you can reclaim 50% or better using regen. I have been mulling it over and an external regen circuit may be easier to encorporate, possibly using capacitors to store the impulse energy to feed back to the controller when it is ready. Building the boost circuit to handle the surge currents as well as being able to control the amount of re-gen (brake smoothness) would be the fun part. I have not heard of too many commercial motor controllers with a re-gen that was not problematic.

Bill

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#28)
by thunderhead (mail me from my homepage!) on Wed Sep 1st, 2004 at 02:08:08 AM MST
(User Info) http://www.simon.richardson.net/mailme.htm

Yes, my understanding is that the motor itself is an inductive load, so the inductor part of the buck circuit is incorporated in the motor, as it were.

The problem with "rippling" the output without an inductor is that there is always a FET on, so the current never varies. It is the varying current in the "buck" circuit that enables the step-down from one voltage to another. To get over that, I'm expecting to use an inductor per FET block, separate from the motor's inductance.

I have been thinking about the regenerative braking, from what I understand, you waste about 30% of your power in braking. Out of the 30%, you can reclaim 50% or better using regen.

A quick calculation shows that for a one-ton car, the kinetic energy at 75mph is about 0.15 of a kWh. Unless the journey consists of a series of rapid changes from 75mph to 0 and back to 75mph again (welcome to the M25) this sort of amount of energy is not going to make that much difference.

The place where regenerative braking does make a difference is in climbing hills. 1kWh takes a 1-ton car up 367 metres (about 1200 feet) if you drive slowly and the motors are 100% efficient at moving the car. If your journey consists of several hill-climbs then that will make a big difference.

A small problem comes if, like me, you live on the top of a hill. That means that if I fully recharge and then drive down the hill, halfway down the battery is full again and the regenerative braking gives out. That's bad. Any regenerative system needs a big dump load (and for 1C regeneration on my 180v 100Ah battery pack I'm thinking of a 0.56Ω 18kW resistor). That 18kW sounds like a lot, but it's equivalent to a vertical descent speed of 1.8m/s, which is about six feet a second or about 4mph vertically. Driving 12mph down a 1 in 3 slope would generate this much energy, and so would driving 55mph down a 1 in 9 slope - even including about 10kW loss for air resistance at this speed. That is normal driving conditions in hilly country, and the reason why brakes get hot.

My understanding is that most regenerative braking systems use big relays, which seems a bit strange to me. But my electronic development for this project is at the "scratch head and look at the magic smoke" stage: I know the principles, as a qualified and experienced electronic engineer, but I don't have final circuits because I haven't built them yet. It seems to me that a "buck" circuit from battery through inductor to motor should provide drive current, and a "boost" circuit in parallel from inductor through battery should provide regeneration. Most IGBT modules have protection diodes included, and if you figure the direction of the protection diodes, the diode for the "boost" IGBT is the freewheel diode for the "buck" circuit, and the diode for the "buck" IGBT is the freewheel for the "boost" circuit.

Here is a "back of envelope" circuit from my project website, to give you an idea:-

The load inductor is not shown: the Hall sensor is a current "clamp meter" type device, used to form a magnetic bridge to allow control of the motor current while maintaining isolation from the traction batteries. The motor current wire will pass through the ring once, but the control current will be between 25 and 100 turns, depending on the control current range I select. The optically isolated switches will probably be IGBTs. The upper-left one is the "buck" switch, and the lower right one is the "boost" switch. The two comparators detect when the magnetic bridge is out of step, then this is clocked onto the two switches by the pseudo-random sequence. If more than one of these modules is used (I'm planning to build them for +100A/-33A, and gang them together) then inductors will be needed on the output.

That's the theory - the practice will almost certainly need some ceremonial releasing of "magic smoke" before it's achieved.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#29)
by bill541 on Wed Sep 1st, 2004 at 10:09:19 PM MST
(User Info)

Thunderhead, since we are getting off the thread subject a bit, perhaps we should start another thread. Fun to discuss for sure.

One idea I would like to share would be to use the vehicles brake system in the feedback loop for regen. One thought was to use the normal brake switch and a pressure sensor in the brake lines. The switch would trigger an A-D conversion of the pressure sensor and when the circuit noticed an increase in pressure, it would apply more regen, if the pressure drops, the regen would also drop. If the batteries are already full, then the regen circuit lays dormant until needed. The vehicles brakes still operate normally but during regen, they would seem to work even better. The goal of the regen circuit would be to keep the brake line pressure constant.

By the way, my work is in electronics engineering as well. Mostly sensor interfacing with microcontrollers and automotive networks. Not much in the high power realm, for the most part under 1000 Watts.

Bill

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#30)
by finnsawyer on Sun Sep 5th, 2004 at 10:32:44 AM MST
(User Info)

How much of that $5.80 per gallon is taxes? One problem is that the government comes in and distorts the economics. For instance, I understand England produces a great deal of natural gas from the North Sea. Where does all this energy go? Maybe you should be using the natural gas to power your vehicles. The problem is that you can embark on a course of action and then have the government change the rules of the game. It seems the more socialist the government becomes the less it cares about the rights of the individual.

I'd also like to point out that distances in the U.S. are vast. I live in northern Michigan. A drive to Detroit, still in Michigan, is 600 miles. Chicago is 425 miles due south. Its over 1400 miles to visit my daughter north of Austin, Texas. We need vehicles that can drive at least 700 miles per day. Battery power currently doesn't make it and probably never will.
GeoM
[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#32)
by thunderhead (mail me from my homepage!) on Mon Sep 13th, 2004 at 02:36:59 PM MST
(User Info) http://www.simon.richardson.net/mailme.htm

At the moment, most of that cost is taxes. But my brother, who works for a major oil prospector not a long way away from where your daughter lives, does not expect that to remain so for very long. The days of cheap oil are fast running out.

What you do for occasional long distances is get one of these:

See http://www.acpropulsion.com/Products/Range_extending_trailers.htm

You only need to use it when you're going to do a long drive (say over 250 miles in a day) so either you leave it in the garage most of the time, or you rent it when you need it.

Anyway, any electric car can do 700 miles a day - provided you're willing to stop and eat a couple of times, and plug it in while you refuel yourselves. Since the charging point costs about 1% of the cost of a petrol pump, the roadside cafes can provide charging points in every car park slot.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#33)
by finnsawyer on Tue Sep 14th, 2004 at 11:57:01 AM MST
(User Info)

I didn't mention that I work with a portable sawmill and can commute 50 miles round trip many days. For obvious reasons right now I use a 4 wheel drive pickup. Those little cars aren't much use for us yankees.
GeoM
[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#35)
by thunderhead (mail me from my homepage!) on Wed Sep 15th, 2004 at 02:22:16 AM MST
(User Info) http://www.simon.richardson.net/mailme.htm

That's OK: larger cars are actually more efficient per unit weight than smaller ones, because of the cube-square law. They have less wetted area per weight.

Pickups don't tend to mind being loaded with batteries, since their suspensions are designed to carry weight. Many homebrew EV designs are based on pickups, because they are so easy. And if you like 4WD, then put a motor on each wheel instead of each front wheel.

I commute between 35 and 55 miles a day too, depending on the route I take, and I'm no Yankee. That's just possible with my E-bay surplus AGMs, but would be easy with lithiums, that should do 200+ miles per charge. The 70 lithiums plus four 35kW (46hp) AVT motors would come to 433kg (970lbs) which is not much more than your ICE and transmission, I suspect. Maybe 180hp would be less than you are used to, but I'm sure it would be sufficient for your needs.

The only difference really is my $6.00/gallon for fuel, which is why I have no doubt about it being a good idea. But you will have the $6.00 gallon soon enough, whichever way you vote in November. The oil is running out. :-( :-( :-(

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#37)
by finnsawyer on Wed Sep 15th, 2004 at 09:54:50 AM MST
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I think you're missing the point here. America is vast. Most goods are transported by truck. We need a system of vehicles that can travel a long distance in 14 hours to keep our economy going. Batteries won't cut it. I'm skeptical about fuel cells. As far as the oil running out, that story's been out there for a generation. Maybe or maybe not. As I travel around this land I see a lot of pumpers sitting idle. As the price goes up many of these will be brought online. I suppose we could go back to large, light coal fired steam locomotives as we've got lots of coal. Trouble is, the railroads retired those as fast as they could once diesel locomotives were developed. The real key is usable energy. Other forms may become available such as space based systems capturing sunlight.
GeoM
[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#38)
by thunderhead (mail me from my homepage!) on Wed Sep 15th, 2004 at 10:13:34 AM MST
(User Info) http://www.simon.richardson.net/mailme.htm

Once you start talking about moving goods, you have the possibility of using railways. The main reason why I oppose forcing all citizens to use public transport is because the motor car has been a great boon for personal freedom. I approve of personal freedom and I don't want to give it up. But a consignment of fridge-freezers doesn't care about personal freedom, and has no rights. It can take the train.

Most of Europe has electrified railways. Europe is not significantly smaller than the USA, and has a larger economy and population. The railway electrification is now being standardised to a single system to allow international freight. Electrified railways can easily run on renewable energy. That is one of their biggest advantages.

My brother works in leading edge oil prospecting, and he does not expect the oil to literally run out, but to become so much more expensive that nobody would consider actually burning it. That will happen Real Soon Now. For some time the recovery techniques have become better and better, but there is a thing called the Law of Diminishing Returns. Although maybe 50% of the oil remains, it is the 50% that is harder and more expensive to extract. What is more, the demand for oil is steeply rising, as other countries in the world - China, for instance - demand to live the same sort of lives as we live in Europe and the USA.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#39)
by finnsawyer on Wed Sep 15th, 2004 at 11:13:22 AM MST
(User Info)

I've got no problem with electrified railways. The problem is where to get the juice? As I've suggested in the past, space based collection is one non polluting option. There's a 4 billion year source there going on 24/7. I believe it's technically feasible today. One possible development path is to use the process to send ion powered space craft to Mars. Beam microwaves to the craft, convert them to 1 million volts dc and get to mars in weeks not months.
GeoM
[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#40)
by thunderhead (mail me from my homepage!) on Thu Sep 16th, 2004 at 03:20:18 AM MST
(User Info) http://www.simon.richardson.net/mailme.htm

I agree with you on the satellite solar power.

So do NASA:-

http://spacesolarpower.nasa.gov/

Unfortunately it appears your government don't share our opinions.

The House of Representatives were presented with NASA's findings on 7 September 2000, and since then it appears two things have happened, one of which is sometimes called "Jack".

:-(

But your government did do something to secure future energy supplies - they invaded Iraq.

:-( :-( :-(

Can I suggest you write to your local politician?

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#42)
by finnsawyer on Sat Sep 18th, 2004 at 12:27:41 PM MST
(User Info)

Naw, you can't trust the b....... anyway.
GeoM
[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#74)
by Peter V on Tue Apr 12th, 2005 at 03:08:21 PM MST
(User Info) http://www.vanderwal.us

Fools cells have very poor overall efficiency, they aren't ready for prime time and won't be anytime soon. The only reason anyone is bothering with them right now is because WW and the oil companies are using it as a smoke screen to distract consumers for viable alternatives to oil.

As for recharging time on EVs. Current Lion technology can produce a 200 lb battery pack with enough energy storage for an EV with a 150-200 mile range. If you made the battery pack out of small 25lb modules, then it would be easy to swap out batteries. You could have battery stations along the highway and swap out your 8 modules in under 5 minutes by hand, or in less than 1 minute using automated machinery.
I use a 150-200 mile range vehicle as an example because that is the project range of fool-cell vehicles and they will take at least 15 minutes to refuel.

Using a standardized 25 lb module would allow you to do things like using twice as many to extend range as needed and using hundreds of them to power big rigs etc.

[ Parent ]

Re: Best energy storage system for vehicles... (3.00 / 0) (#16)
by pdvjak on Thu Aug 26th, 2004 at 03:16:47 AM MST
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This is a very interesting discussion! I live in Indonesia and see first hand the onslaught of the 'oil culture' as and when millions of 'new consumers' stri