Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 



Forgot your password?
typodupeerror

Comment Re:Again? (Score 2) 121

The charge times are a factor, but mostly it's cost, cost, cost!

Batteries are economically unsustainable: Li-ion batteries (the type with high energy density that you need in any battery vehicle) cost about 500 $/kWh. You can expect it to drop somewhat through the next decades, say to 300 in 2050, but they are already being mass-produced and unless a significant, revolutionary breakthrough happens, this technology has already delivered what it can.

Hydrogen storage, instead, costs about 12 $/kWh, much cheaper (I'm talking of the only commercial technology, compressed hydrogen at 350 or 700 bar). In addition to that, you need the fuel cells to convert hydrogen to power, and they cost about 300 $/kW (not kWh, kW). However, they are not mass-produced, in which case projections indicate they would cost about 50 $/kW or lower.

Now, trust me on this one (or do the calculations yourself): of the world's 10 most sold cars, almost all have one kW in the engine for every kWh of fuel in the tank (netting for engine efficiency). So mass-produced hydrogen cars can have a powertrain that is an order of magnitude cheaper than batteries by the kWh when mass-produced. Not only you can build a car that drives 500 km—you can afford it too!

But what about efficiency, I hear someone in the back shouting: it is true that batteries are about 90% efficient, and the electrolysis, compression and fuel cells train is about 40% efficient. However, consider this: a battery can operate for about 1500 cycles before end-of-life. Every kWh of capacity will store and release 1500 kWh, which in consumer prices (different by country, I know) is about 150 $. This means that the cost of batteries is much higher than the cost of the energy they will store through their entire lifetime. Efficiency in operation actually takes a back seat when investment costs are this high.

Finally, what about capacity? Li-ion batteries store 0.25 kWh/kg (that's why Teslas are so heavy). Hydrogen (including the pressurised tanks, that are 90% of the weight, and netting for 50% efficiency) provides 2 kWh/kg, again one order of magnitude higher.

To be clear: there is a marked for batteries and one for hydrogen. Smaller applications for short usage are better with batteries (think commuter cars). Larger applications, or applications that in general need a lot of energy compared to power (taxis, buses, trucks, even ships) are better served with hydrogen.

Comment Re:invite more people in? (Score 1) 547

So you are saying that Christian culture is the worst:

The problem with many European racists is that they blindly assume that all muslims believe the Quran. Just like for Christians and the Bible, most muslims do not read the Quran, even if they keep a finely decorated hardcover copy in the house. In the case of the Quran it's actually even less likely they are going to read it, since the Quran makes a point of being in Arabic, while the Bible is usually translated. Even if many non-Arabic speaking muslim countries include Arabic in their school curriculum, often ostensibly to allow reading the Quran, no one can reach a level of skill sufficient to do so in school (think of how many US citizen can read the Bible in French or Spanish after high school).

Of course you will find plenty of evil in the Quran, just like in the Bible. Of course Mohammed did evil things, so did Jesus (being rude to his mother—note that it is a violation of the fourth commandment, punishable by death in the Bible—, proclaiming war in Matthew 10:34-35, vandalising property and inciting a mob against the merchants in the temple, etc.), and of course all these parts are ignored, repressed and buried among Christians. But if they are read those quotes and told it's the Quran, they promptly believe it, because Islam is evil, right? (NB: of course Islam is evil. I am pointing out Christianity, Judaism, and for that sake Buddhism are not better.)

We all despise Saudi Arabia and Iran for their barbarous executions of homosexuals, but can you remember what England did to Alan Turing? That's England, a country noted for centuries for being one of the most liberals on the continent, not Italy or Poland, just two generations ago. And it was a war hero they were punishing.

Point being: the Quran is not more representative of muslims than the Bible is of christians. Some believe that nonsense (extremist nutjobs), some say they believe but don't really care, some believe they believe even if they don't know what is in the books (looks like you), and some dismiss the whole humbug. "Culture", as you intend it, is a mostly personal issue, and there is no way to determine that Mr. X from Syria is less liberal than Mr. Y from Oslo. Variations between single persons dwarf the average difference between population by orders of magnitude.

Comment Re:Who cares (Score 4, Informative) 578

I worked for a few years at a Max Planck Institute (not the same one as Jobb), and I remember he sent occasionally racist rants to all email recipients in all institutes, in which he lamented that the foreigners were taking his job. The rants were so logically inconsistent they looked like a crossing of Time Cube and the Unabomber Manifesto.

More than racist, which he is, the guy is psychologically unstable; the archetypal mad scientist.

Comment Re:The problem is that landfills are too cheap (Score 5, Interesting) 371

The way it works here in Norway is that you pay an extra tax when you buy an eventually recyclable item. When you want to get rid of your old washing machine, you can deliver it to anyone selling washing machines ("you sell it, you take it"). Their logistic costs for handling the waste are paid by the taxes paid on new items.

For some items you actually can get the tax back, e.g. for plastic bottles and beer cans. You bring them to the supermarket, feed them to a robot and get a receipt (one dime for small bottles, three for larger ones) and redeem it at the cashier. It's smal enough that people don't mind the extra price, but high enough that you see bums scavenging trash for bottles.

That's the main principle you need to drive home—you make people pay when they want to buy things that they eventually will dispose of, when they have their wallet open, and make them pay nothing extra (or even pay them something) when they recycle it.

Comment Re:just what we all love (Score 4, Insightful) 243

I am pretty sure that Amazon did not originate in Luxembourg, that they do not have any significant infrastructure in Luxembourg, and certainly most of the products they ship are not made in Luxembourg.

I would not have any problem if their actual warehouses were all in Luxembourg and all shipments departed from there; however, they most certainly do not. It's a good thing to pay taxes from a single country when selling to several, but one must pay taxes where the value is generated, not going around shopping for the lowest rates.

The single market was intended to be used for simplification, not for tax avoidance.

Comment Re: 23 down, 77 to go (Score 3, Insightful) 866

I'm fairly certain humanity would find plenty of reasons to wage war if religions were not around to blame it on.

Governments would, of course, but it would be much more difficult for them to convince soldiers to actually go fighting.

Example 1, Operation Iraqi Liberty: US government wants to gain control of resources in Iraq, but they tell their people it is really for ideals of freedom and to do God's bidding. Iraqi government wants to stay in power and keep oppressing their people, but tells their people they need to fight because God is the greatest.

Example 2, US Civil War. North wants to instate an economy of small farmers who can buy products of northern industry, but tells their people that it is because we're all brothers (which may very well be true, but I don't see the same people so eager to go to war when there is no money to be made); the South wanted to keep mooching off slave labor, but said that the Bible advocates slavery, so it's really a holy war.

In all cases, it is difficult to convince someone to risk taking a bullet if you cannot convince them that there is life after death, and that is eternal and so much better than this valley of tears. This creates a problem for the few countries that disavowed religion and were involved in wars, notably the Soviet Union, which had therefore to develop its own pseudo-religion of Rodina and, just to be on the safe side, extensive usage of barrier troops.

Comment Mods on crack? (Score 3, Insightful) 880

Crusades are easy, that would be a response to 100 years of Muslim rape, slaughter, and forced conversion in Spain.

Aside from the fact that Christians did exactly the same when they reconquered the Iberian peninsula, and aside from the fact that in that time Muslim societies were far more liberal than any Christian society (Jews usually fled to Muslim countries from Christian countries), would you mind explaining why no bloody crusade ever went west to Spain, but all East to Jerusalem?

The crusades were the product of a fanatical Christian society, with the motivation of paradise for the soldiers and spoils of war for the commanders. They sacked, plundered, raped anything between Europe and Jerusalem, and that includes Costantinople that at the time was Christian. Which was expected of any serious army at that time. The pretext for war was the "liberation" of Jerusalem, and the real drive was a combination of poverty, ignorance, greed and religion. So the crusades were pretty much the ISIS of the second millenium.

Do read up some history lest you spout more of such nonsense.

Comment Re:Electricity vs. oil (Score 1) 194

It would take a lot of progress to get electricity to be the most economic solution for heating.

This depends a lot on where you live, especially for gas. For house heating, a heat pump is quite efficient, especially if you have a water reservoir available. For cooking, gas looks very cost-efficient since you simply have to burn it under a pot to extract all its heat, but a lot of the heat gets lost as hot air that bypasses the pot. Induction heating uses electromagnetism to generate heat inside the pot's metal, so even though the cost per kWh is higher, you end up using less energy, so it may very well be competitive.

However, you are forgetting the one source I have in my house, district heating. Industries generate enormous amounts of waste heat that could be used for district heating, I remember one air cooler in a refinery that dissipated over 16 megawatts of heat. If you hook up factories, offices and homes with district heating, you can provide heat without any other external source.

Comment Re:I don't think hydrogen makes sense (Score 1) 293

(My own disclaimer: I am researcher in hydrogen & fuel cells)

Containing hydrogen is no longer much of a problem, though compressing it in the first place is still expensive. Still, you don't really need a distribution network: the trend is to use electrolysers and produce the hydrogen locally. With the increased share of non-programmable renewables like wind and solar, hydrogen stations can produce their hydrogen when there is an excess of available power.

It's not just the price of batteries, which may very well come down: it's their weight. There is only so much that can be done now to increase Li-ion energy density; Elon Musk was dreaming of using graphene for superbatteries, but that's a very long shot. Sure, hydrogen cannot compete in the short range with batteries, but it is much better in the long range. And yes, batteries are much heavier than the tanks containing hydrogen.

The energy density of Li-ion batteries is about 100 Wh/kg, hydrogen is 32500 Wh/kg. Even accounting for 50% conversion efficiency and a hydrogen tank 10 times as heavy as the hydrogen, you still get over 1600 Wh/kg, well over 15 times Li-ion! Then of course you need to add the fuel cell system, which is dimensioned by power (not by energy as the tank is), and its weight is why FC cars are better in the long range, where this weight is a smaller fraction of the total FC system weight.

Running fuel cells on hydrocarbons directly is not an option (slow chemistry), but they can be reformed on-the-fly to hydrogen; in fact you can do that with diesel. The only problem is, the system gets so much complicated it is soon not worth the bother when you have a highly dynamic load as is the case for a car.

Comment Re:I don't think hydrogen makes sense (Score 1) 293

Holy bad data, batman! You have so many numbers wrong my head is spinning. Try this:

  • needs to be compressed to 1000+ atmospheres Standard H2 pressure in most modern tanks is 700 bars, not 1000. 350 bar is also quite ok since it contains 2/3 of the hydrogen you get at 700 (hint: no ideal gas at those pressures). Very little to be gained by going to 1000 bars.
  • [to generate H2] first you need to generate the electricity. That's usually from a coal plant operating at 45% efficiency at best Or it could be wind farm, or a solar plant, or any of those pesky renewables that do not want to produce power exactly when we need it. So instead of dumping it, you make hydrogen with that extra zero-emission power. That, and combined-cycle gas plants can be 60% efficient.
  • the electrolysis is about 65% efficient at best That's a number for alkaline electrolysis, PEM electrolysis can go much higher. Some cheat and define efficiency with enthalpy instead of Gibbs free energy, which gives them efficiencies close to 100%, but somewhere between 80-90% is realistic.
  • put the hydrogen through a fuel cell which can be 90% efficient in the lab, but peaks at about 70% efficient in commercial applications Actually no, no one has ever seen 90%, not even in the lab, but a common efficiency in usage is about 60%.
  • And by the way you did not mention the significant losses for hydrogen compression, which are not a showstopper but do motivate research in e.g. hydride compressors for hydrogens running on waste heat instead of mechanical power.
  • gasoline ICEs, which are currently about 25%-30% efficient That's your main mistake. This value holds only at their maximum efficiency, which is almost never where they operate. You also fail to account that gasoline does not grow on trees, it needs to be extracted as oil, refined and distributed. The whole Well-to-Wheel efficiency of gasoline is about 10% on a good day.

Comment Re:MatLab is not really a good programming languag (Score 1) 205

You might have noted I wrote, "OO support as C++", where I meant "well thought-out OO support". There is OO in Matlab, but it's just like claiming Fortran has OO support. Technically true, but added as an afterthought, and most code out there does not use it.

you somehow missed that semi-colons are not statement terminators

Why yes you could write without them, but then you would get an echo on every assignment on the prompt. No sane person would do that in production code. In practice, all statements in M-files need to be semicolon-terminated.

You should have known this if you had actually worked with even a modicum of MatLab script.

FYI I was on Matlab/Simulink several years (before moving to Scilab, Octave and C++), and I actually held a course in Matlab for undergrads at a Max Planck Institute when I worked in Germany.

Comment Re:About CVS Only! Not SVN! (Score 1) 245

[...] because those files are binary and very large

No VCS is meant to do this, neither Git, SVN and certainly not CVS. Those files don't belong in a VCS because you cannot make a diff between them. Small binary files (e.g. icons in a website) are a small nuisance, but there is no point in storing large binary blobs in a VCS regularly. What you need is a backup system, not a version-control system.

(2) permanently delete those files that I know I will no longer need

SVN allows to do this with svndumpfilter (and I was unaware CVS had any way to do this). And no it should not be made any easier, no one should be allowed to monkey around with the repository history with any less than admin rights. If you find yourself regularly removing files from a VCS, it means you have been adding too many useless files. Again, you want backup for this, not VCS.

Slashdot Top Deals

//GO.SYSIN DD *, DOODAH, DOODAH

Working...