Follow Slashdot stories on Twitter


Forgot your password?

Comment: Re:With the best will in the world... (Score 1) 283

by Rei (#49562355) Attached to: Audi Creates "Fuel of the Future" Using Just Carbon Dioxide and Water

Saying "Now design a battery that can pull a 440,000 pounds or 200,000 kilograms triple trailer configuration across hundreds of miles of highway. " is silly, that's like saying "Now design a gas tank that can pull a 440,000 pounds or 200,000 kilograms triple trailer configuration across hundreds of miles of highway. " Batteries don't haul loads, electric motors do. And electric motors have far more power per unit mass and per unit volume than gasoline. Here's a comparison between a gasoline car engine and an equivalent power electric motor.

The heaviest haul vehicles *do* use electric drive. The vast majority of trains today, for example, are electric drive, and increasingly large haul trucks are switching to electric drive. The electric drive however is generally driven by either diesel generators or direct grid power to save the cost of having to buy batteries. Due to the battery cost, the largest ones out there re things like BYD's 60 foot / 120 passenger jointed bus and several models of 15-30 tonne haul trucks. The economics just aren't there for road trains like you're talking about at this point. It's not a tech issue, it's a battery cost issue.

Supplying the power is easy. Just thinking about it from a practical standpoint. These are batteries that can fast charge in half an hour or so. Discharging is generally easier on batteries than charging. But let's just say half an hour discharge. Li-ions now get up to a couple kilowatts per kilogram, but are only a couple hundred Wh/kg at best in terms of energy density. A road train may require something like 1000hp. That's 750kW electric. Actually less because you get a smoother torque curve, but let's ignore that. That's about 375kg of good li-ion batteries to be able to provide the needed power. Let's double that for poorer batteries, and add a bunch more for inefficiencies... let's go full overkill and say we need 1000kg of batteries to provide the needed power. 1000kg of batteries would hold about 200kWh of electricity. That's only 80 miles of range. Which is way less than you'd practically need for a road train.

That is to say, even with the most pessimistic look at it, even a pathetically under-ranged road train would have way more power than needed to run its engine. The more batteries you add, the more power becomes available. Power density is essentially a non-issue when dealing with li-ions.

Also look at aviation, liquid fuel is going to be the practical choice far into the future.

Aviation is the highest-hanging fruit, but it's still a fruit that is within reach, and the small-scale electric prop plane market has gone from almost nonexistent to rapidly growing in the past 5 years or so. And there's lots of transitional techs, such as driving the compressor with electricity, which allows you to get rid of the turbine and thus increasing engine power and efficiency while reducing part count and maintenance.

The motors and batteries also require rare earths with are in short supply and require massive mining operations to supply.

False. First off, only permanent magnet motors require rare earths. Most modern EVs, like Tesla's offerings, don't use permanent magnets. Secondly, lithium-ion batteries do not use rare earths; I don't know where you got this idea. Lastly, rare earths aren't actually rare. China dumped the market, pushing other producers out of business, and then suddenly started holding back production for domestic uses, creating a temporary glut, but it's already started resolving itself.

An it's just not a matter in installing fast chargers, widespread adoption would require an overhaul in the electric grid.

This is once again false but I've already lost enough interest in this conversation to have to dig up research papers for you, so I'm just going to tell you "Google It". There've been many studies, every region in the US except the Pacific Northwest already has the generation capacity, as well as the distribution capacity, excepting the "last hop" in residential areas (neighborhood grids). But that'd only be an issue if everyone magically switched over instantly, it presents no threat to any realistic adoption rate.

EVs are inherently grid stabilizers. Utilities love them. They charge mainly at night, when demand is way down and power plants have to sit idle, and they're predictable, steady loads. Utility companies are some of the biggest EV proponents out there. Smart charging (which, BTW, doesn't inherently require outflow, just changes in the rate of inflow) is just an extra.

Comment: Re:Since when (Score 1) 299

by Rei (#49561953) Attached to: Pepsi To Stop Using Aspartame

Let me take a wild guess that the hospital said he was a-okay.

People with phenylketonuria are not that hypersensitive to drinks containing aspartame. Protein-rich foods is usually more challenging to deal with since they're harder to avoid and can provide more phenylalanine. And the condition is not an immediate reaction like a food allergy, it's an accumulative problem. There's no way drinking a diet soda should have landed him in the hospital.

I have a strong suspicion that this person was like 90% of "gluten intolerant" persons: a self-diagnosed hypochondriac.

Comment: Re:danger vs taste (Score 1) 299

by Rei (#49561817) Attached to: Pepsi To Stop Using Aspartame

at a bare minimum they are less likely to eat some of your food.

Gut bacteria are not "eating your food", they're making food for you. They consume that which your body was not able to break down (such as some types of starches and sugars) and produce things that the body can absorb, like short chain fatty acids. Rodent studies show that if you kill all of a rat's gut flora with antibiotics that they have to consume about 30% more calories to maintain the same weight.

If gut bacteria were consuming significant amounts of our calories we would have long ago evolved to fight them off. They help us get more calories from our food.

Comment: Re:danger vs taste (Score 1) 299

by Rei (#49561613) Attached to: Pepsi To Stop Using Aspartame

Going from fatty to not fatty requires precisely one thing: reducing the amount of calories in versus the amount of calories out.

Nothing else.

Some routes may be easier to take than others, reducing cravings and the like. But it all comes down to energy in vs. energy out. One can diet on eating nothing but twinkies.

Comment: Re:danger vs taste (Score 4, Interesting) 299

by Rei (#49561581) Attached to: Pepsi To Stop Using Aspartame

Aspartame does break down into poison. One of the components it breaks down into is methanol. Wood alcohol. The stuff that makes you blind. Drinking the amount of aspartame found in 14 cases of pop every day would fill your system with a large amount of methanol. No question that's going to have negative effects.

The amount of methanol actually found in *normal* consumption of diet sodas, however, is similar to the amount found in things like fruit juice. If your body can deal with fruit juice, it can deal with aspartame-sweetened drinks. As always, it's the dose that makes the poison.

Yes, there is a positive correlation between drinking diet sodas and being overweight. But that's an expected correlation, not a causation. Seriously, what sort of person who's not prone (for whatever reasons) to weight gain is suddenly going to decide, "You know, I want to switch from normal pepsi to diet."? The people who start drinking diet are the ones having trouble with weight gain already. The problem is, a can of pepsi is 150 calories. That's the amount of calories in 1/3 cup of raisins. Yeah, it helps somewhat with your calorie consumption, but it's not the big picture on its own.

Comment: Re:Hispanics replaced by... (Score 1) 214

No, TFA was talking about picking machines from Spain, and even said that they're from Spain. Both of the two systems mentioned, AGROBOT and Plant Tape, are from Spanish companies. The AC saw the word "Spanish" and stupidly thought that means "Mexican".

The AC said something stupid, I pointed out what they said that was stupid, and that should have been the end of it. Instead we have you trying to pretend that what they said wasn't actually stupid. It was. Let's accept that and move on.

Comment: Re:With the best will in the world... (Score 2) 283

by Rei (#49561229) Attached to: Audi Creates "Fuel of the Future" Using Just Carbon Dioxide and Water

I've noticed most criticisms of EV charging simply relate to a total lack of imagination about how to address engineering issues. For example I've seen people rant and rave and run all sorts of calculations about how it's impossible to run large amounts of power through a manageable cable for an electric car, and therefore fast chargers are a big scam... pure vitriol, and overlooking one tiny detail: ... nobody says that your cable has to be passively cooled.

All of those cable thickness guidelines for home wiring and the like are for passively cooled cables. You don't have to use a cable the thickness of your wrist to deliver a fast charge, you just have to wrap it in a cooling sheath. Some of the highest power chargers already do this. Problem solved really, really easily.

Comment: Re:With the best will in the world... (Score 1) 283

by Rei (#49561171) Attached to: Audi Creates "Fuel of the Future" Using Just Carbon Dioxide and Water

It's worse than that. Your diesel engine may be 30-40% efficient when running in its optimal power band, but of course it doesn't sit around at its optimal power band all the time while a car is driving. In practice diesel cars average about 25% efficient, gasoline cars about 20%. They're slowly improving, mind you.

Comment: Re:With the best will in the world... (Score 5, Informative) 283

by Rei (#49561073) Attached to: Audi Creates "Fuel of the Future" Using Just Carbon Dioxide and Water

"Maybe, maybe not"? Please, you know that the answer is "not even remotely close". Even when you start with petroleum as your feedstock and only waste 10-15% of the energy it contains in refining and distribution, you've still got the car only turning 20% of the energy therein into useful kinetic energy (25% in the case of diesels), versus an average of about 85% of the electricty into kinetic energy (minus about 8% transmission losses), plus automatically gaining hybrid-style regen. Even if the process was 100% efficient - which it won't be anywhere even close to that - just the difference in propulsion technolgies would put the EV at 4 times the efficiency. Based on related processes, I'd wager that this tech is probably along the order of 30% efficient, so you're looking at about 13 times more range per kWh on an EV than a ICE car fuelled by this fuel. Which means 1/13th as many square kilometers of wind turbines, 1/13th as many solar panel factories, 1/13th as many dammed rivers, etc. Yes, it really matters.

But come on, don't play dumb and pretend that you actually think that the efficiency of taking electricity, extracting gases from the air, converting them into a mixture of complex hydrocarbons, then burning them in an ICE and facing Carnot losses, is somehow "maybe, maybe not" more efficient than using the electricity directly.

it has a higher energy density than batteries, which is super important for vehicle applications.

It really, really isn't. Almost everyone on the planet would be driving an EV at today's energy densities if one factor was significantly improved, but that factor isn't energy density. It's cost per kilowatt hour.

A 250Wh/mi EV that can go 400 miles (8 hours driving without a stop at an average speed of 60mph) needs 100kWh. At a reasonably good but not spectacular 200Wh/kg, that's 500kg. Due to electric drivetrains' superior power density, switching a low power gasoline drivetrain to an equivalent electric one saves about 100kg. Switching a high power gasoline drivetrain to electric can save a couple hundred kilograms. So you're increasing the weight of a car by a few hundred kilograms. You really think your average consumer would give a rat's arse if their car is a couple hundred kilometers heavier if it lets them drive on fuel that costs a third as much?

Of course, these are only a couple of the issues (I'll ignore environmental ones for now because I know a lot of people here don't give a rat's arse about them). Added weight hurts handling on cornering. But EVs make better power to weight ratios easier, and especially improve performance on low end torque. They also give designers a lot more flexibility on placement of components, which can translates into things like more spacious interiors for a given vehicle footprint, and almost always means a lower CG. One has to charge, but one never has to go to a gas station, and most people would find plugging in in their garage much more convenient than a special trip to a gas station and standing outside in whatever weather. This leaves open the question of charge times, of course. But if you can drive hundreds of miles on a single charge and charge up on a fast charger during lunch and then take off again, it's pretty irrelevant. Gasoline cars need big tanks to minimize the inconvenience of having to stop for gasoline regularly in your daily life. Using fast chargers of course means having a fast charger infrastructure, but that's an eminently addressable chicken and egg problem. Modern li-ion batteries deal quite well with fast charges.

The short of it is, if today's batteries were cheap enough - no better density or anything else - electric cars would very quickly take over the market place. Other improvements in technology will improve the sales proposition, but they're not essential.

Comment: Re:KDBus - another systemd brick on the wall (Score 1) 177

by fuzzyfuzzyfungus (#49560747) Attached to: Linux 4.1 Bringing Many Changes, But No KDBUS
Very true; though (on the whole) the end user has made the same choice when they'd either have to buy more hardware or spend more for software and/or make do with fewer features.

Even situations that are highly cost sensitive and have customers who bear the entire cost of the extra hardware or the extra software engineering (like embedded systems) have seen a fair amount of hardware growth. Cortex-M0 or a bunch of extra squeezing to get it into an 8 or 16 bit micro?

Comment: Re:KDBus - another systemd brick on the wall (Score 1) 177

by fuzzyfuzzyfungus (#49560681) Attached to: Linux 4.1 Bringing Many Changes, But No KDBUS
I'm no expert; but my off-the-cuff assumption would be that it could be made quite fast:

At least with Debian and derivatives, you have a locally stored cache of package data(not the packages themselves, but their metadata). Searching that is pretty fast unless you have a lot of repositories or a brutally slow storage system.

The obvious(and probably flawed in some less obvious way that I'm not thinking through) extension would be to add the VID/PID combinations (or device classes, for class drivers) to which a driver package applies to the existing metadata about the package. You might also have a 'driver package vs. 'non-driver package' distinction to reduce the search space). During the hotplug process, if nothing suitable is already available, apt-cache search for the VID/PID pair would be run, and a match downloaded, if available(the amount of security prompting would obviously be a matter of configuration: sometimes it would be desireable that admin authorization always be required, sometimes it would be better if downloads from already-blessed repositories are acceptable, depends on the use case).

The local search would be reasonably fast, barring very slow storage, the download and install obviously depending on the size of the driver and the speed of the connection. In the not-terribly-valuable opinion of a layman, it seems like it could be reasonably quick.

Comment: Re:Hispanics replaced by... (Score 1) 214

I hate to break it to you, but the original article stated "The labor shortage spurred Tanimura & Antle Fresh Foods, one of the country's largest vegetable farmers, to buy a Spanish startup", and its link to the company website brings up a page that starts off with "Plant Tape is a visionary and innovative company founded in Spain".

The AC responded "So the guys from Mexico will be replace with... hardware from Mexico?"

Why you're mentioning the word "hispanic" is beyond me.

Comment: Re:AGP not working with SMP (Score 1) 177

by TheRaven64 (#49559459) Attached to: Linux 4.1 Bringing Many Changes, But No KDBUS

Multi-core x86 processors only appeared well after PCI-E had taken hold

True, but SMP systems are older. I used a dual P3-700 for years, which I picked up cheaply on eBay because not many people searched for 'duel processor' (I think eBay now does some phonetic matching in their search). Before that, the ABit BP6 (1999) was quite popular. It ran two Celerons, so you could get a dual-processor machine for cheaper than a single-processor one (though you needed to run Windows NT or *NIX to be able to use the second one, as XP was the first SMP-capable consumer OS from MS). The 300MHz Celerons overclocked to 450MHz by bumping the FSB from 66MHz to 100MHz, making it quite competitive with the P2 (the L2 cache in the Celeron was half the size, but twice the speed, and the core was the same).

If it happens once, it's a bug. If it happens twice, it's a feature. If it happens more than twice, it's a design philosophy.