Slashdot is powered by your submissions, so send in your scoop

 



Forgot your password?
typodupeerror

Comment: Re:Wikipedia is sometimes wrong (Score 1) 165

No, it works with non-controversial subjects.

Unfortunately, it also works with controversial subjects if the article is obscure enough.

I recently came across a page about a fringe crackpot group which included highly inflated membership estimates (in the millions of members, rather than a more accurate estimate of about 300 members). Since the group was very obscure, the incorrect claim had persisted for years. The only people monitoring the page appeared to be group members.

Comment: Re:Wikipedia is sometimes wrong (Score 1) 165

Fortunately, the tools for automatic jerk identification are improving.

If that were true, you wouldn't be able to post on slashdot.

As one of the people who spends time cleaning up stuff like that, it's seriously annoying.

It was a legitimate experiment to an extremely obscure article, and it had no serious negative consequences.

Promoters of wikipedia frequently claim that the source is highly accurate because inaccuracies are rapidly corrected. If they make claims like that, it's legitimate to test whether the claims are true.

Comment: Wikipedia is sometimes wrong (Score 4, Informative) 165

by floobedy (#48120925) Attached to: How Spurious Wikipedia Edits Can Attach a Name To a Scandal, 35 Years On

As an experiment, I added a spurious and incorrect fact to an obscure wikipedia article, complete with a reference to a document which did not support the claim. It took years before my edit was noticed and reversed.

This only works with obscure articles. The more obscure the article, the less it's checked. If you try inserting something spurious into the page on Obama it will be reversed in about 5 minutes.

Comment: Re:Still pretty affordable (Score 1) 393

by floobedy (#47931773) Attached to: Is the Tesla Model 3 Actually Going To Cost $50,000?
I don't think that's right. I've known a couple of EV owners in CA who claim that the electricity costs are less than half what gasoline costs, per mile. The Chevy Volt uses 10 KwH of battery capacity to travel approximately 40 miles. That's 0.25 KwH/mi, which is $0.0375 per mile with electricity at $0.15 per KwH (in CA). Gasoline is about $4 gal and can take a car about 35 miles, which is $0.1142 per mile, which is ~3x as expensive as the EV.

Comment: Re:Everything old is new again (Score 1) 491

by floobedy (#47868715) Attached to: To Really Cut Emissions, We Need Electric Buses, Not Just Electric Cars

I didn't know that. It's strange that SF owns its own power plant for city services.

I suppose I can act like an economist here, and say that electricity for public services in SF still isn't really free. SF could sell that electricity for 6 cents per KwH, so there's forgone income which should count as a cost.

Comment: Re:Container ships (Score 1) 491

by floobedy (#47868695) Attached to: To Really Cut Emissions, We Need Electric Buses, Not Just Electric Cars

I can see why we'd want to stick with bunker fuel for ships, since only ship engines can burn that kind of fuel. It takes huge engines to burn that kind of fuel. As you pointed out, no. 6 bunker fuel isn't liquid at room temperature so it's necessary to pipe the exhaust past the fuel tank in order to melt the fuel, so the fuel will flow into the engine.

Without ships, bunker fuel would kind of be a useless waste, since no other engines can use it. I suppose it could be burned for heat or electricity, but oil is an awfully expensive way doing those things.

I'm more familiar with the economic aspects of the ocean shipping industry, than the engineering side. I wonder if it would be possible to filter out some of the crap that comes out of the smokestack. That way ships could continue to use bunker fuel without harming the health of people around. Something akin to a catalytic converter on cars.

Comment: Re:Everything old is new again (Score 5, Interesting) 491

by floobedy (#47867917) Attached to: To Really Cut Emissions, We Need Electric Buses, Not Just Electric Cars

San Francisco has had a fairly extensive trolleybus network since the 1930s. Although only 15 bus lines are trolleybuses, those are the most crowded bus lines, so a significant fraction of bus traffic there is electrified.

It appears that diesel buses cost $450,000, and battery-electric buses cost $825,000, and trolleybuses cost $1m each. Trolleybuses last at least twice as long as diesel buses. The overhead wires cost $2 million per mile and last almost indefinitely, it appears, because I have never seen maintenance being performed on any of them, in contrast to roads and stoplights which are being repaired constantly, and buses which are being replaced often enough.

San Francisco has 300 trolleybuses for 15 lines, and each line is about 6 miles long. Thus the overhead wires cost $180m, the buses cost $300m, and the electricity costs $48m over 24 years. It appears that equivalent diesel buses would cost $270m and use $330m in fuel over 24 years, servicing the same routes (just using the numbers I read from an article and doing the calculation manually). It would appear that trolleybuses cost ~$528m for those routes and diesel buses would cost ~$600m. However, that's not taking into account financing costs etc, which would probably make the trolleybuses more expensive than diesel ones since the upfront cost is higher. Also, this is for routes in San Francisco which are only 6 miles long; the economics may change for suburban routes.

That said, it doesn't seem like the costs are very different whether we choose trolleybuses, diesel buses, or battery-electric buses. It may be slightly more expensive to go electric, but not much.

Comment: Re:Container ships (Score 5, Informative) 491

by floobedy (#47867713) Attached to: To Really Cut Emissions, We Need Electric Buses, Not Just Electric Cars

The 15-30 largest container ships in the world (depending on who's estimates you're using) produce more pollution than all the cars combined.

The largest container ships have huge particulate emissions, but that's because there's no regulation on particulate emissions according to international law. It would be difficult to change that, because regulating ships requires an international agreement. That said, it should be done.

However, ships already have extremely low CO2 emissions per ton-mile. They are already extremely fuel-efficient. The largest ships have 1/15th the fuel usage and CO2 emissions per ton-mile as a tractor-trailer truck, and massively better than your car. If you drive one mile to the store to buy an article of clothing, you have emitted vastly more CO2 than was emitted by shipping it halfway around the globe by containership.

You want to reduce emissions? Pay for it to be grown locally instead of on the other side of the globe.

That will have almost no effect on your CO2 emissions.

Comment: Re:Law of Large Numbers (Score 1) 442

by floobedy (#47692693) Attached to: Is Storage Necessary For Renewable Energy?

You missed the point of the post. Lovins was talking about unscheduled downtime like the wind not blowing, or a reactor scramming because of a tremor. He was claiming that renewables were similar to baseload power plants in that they both have unscheduled downtime. I was responding to that.

Of course there is also scheduled maintenance, but that's not what Lovins was talking about. That has no relevance to the discussion of whether storage would be required for renewables. If Lovins was talking about scheduled downtime then his point was even weaker.

Comment: Law of Large Numbers (Score 3, Interesting) 442

by floobedy (#47690991) Attached to: Is Storage Necessary For Renewable Energy?

I think the biggest mistake of the video, is when Lovins says that renewables are no different from baseload power plants, because baseload plants are down some fraction of the time also. He claims that power companies already compensate for downtime of baseload power plants by just having a few extra power plants. He claims that the same thing could be done with renewables.

That's just all wrong, in my opinion. It's a statistical error. Although baseload power plants are down 10-20% of the time, they are down at random. The downtime of any one plant is not correlated with the downtime of any other. As a result, if you have enough plants, then 10-20% of power generation is offline at any given time, as a result of the law of large numbers. That can be compensated for by building a few extra power plants.

With renewables, their downtime is not random. Their downtime is correlated with that of the other plants. For example, when the sun goes down, all solar panels stop working at the same time in a geographic region. Also, when the wind stops blowing (which can happen over a wide area), all windmills in that region will stop working at the same time. This is a much bigger problem than randomly distributed downtime.

If solar panels had randomly distributed downtime, and were as likely to generate power during winter nights as during summer days, then no storage would be required. We could just build more solar panels. This is because the randomly distributed periods of downtime of the solar panels would "cancel out" each other. However, it does not help to build more solar panels for the night time.

That is why renewables require storage.

Comment: Re:Ammonia fuel (Score 1) 117

by floobedy (#47645785) Attached to: New Process Promises Ammonia From Air, Water, and Sunlight

Even if it only made 0.0001% nitric oxide and some kind of catalytic converter caught 95% of that, it would still destroy the environment faster than fossil fuels.

I doubt that. Burning a gallon of gasoline in an internal combustion engine produces about 1.5 grams of NOx, which is more than would be emitted by 0.0001% from ammonia combustion.

And that's if none of the ammonia ever escaped from vehicles, let alone the industrial production and transport.

Ammonia is a basic building block of life and is already produced in huge quantities by bacteria in the soil. Furthermore, it's produced in massive quantities by industry, at a rate of 150 million tonnes per year worldwide. That's more than 20kg per person, per year, worldwide, which is more than any other chemical. No attempt is made to confine that ammonia or prevent it from leaking into the environment. Quite the contrary, that massive quantity of ammonia is injected directly into the soil as fertilizer, or evaporates from window cleaner. The amount we are leaking into the environment right now, is vastly greater than the amount which would leak from the occasional defective fuel tank.

If ammonia is causing some dire environmental effect, worse than global warming, then I've yet to hear about it. I'm not saying you're wrong, but you'd have to provide some evidence for your assertion.

Comment: Re:Very amusing reading comprehension failure (Score 1) 117

by floobedy (#47640385) Attached to: New Process Promises Ammonia From Air, Water, and Sunlight

Sure. Sorry to have offended you. I thought you were being snitty. I apologize for being aggressive in my response.

It's also probably harder to get the hydrogen out of the ammonia in secondary processes than from hydrocarbons - plus if it's fuel cell usage you do not need to go all the way down to hydrogen gas anyway.

I was originally thinking that ammonia could be used directly in internal combustion engines, as a replacement for oil when that starts to become scarce. Of course there are replacements for oil in most applications (plug-in cars and electrified rail), but there are some applications where a liquid fuel would be very helpful (such as remote construction equipment, ships, and so on).

There are very few combustible liquids which can be made out of the main constituents of air and water, and so wouldn't alter the composition of the atmosphere when burned. That's one reason I was excited about a process which produces ammonia using less energy.

Comment: Re:Very amusing reading comprehension failure (Score 1) 117

by floobedy (#47638339) Attached to: New Process Promises Ammonia From Air, Water, and Sunlight

I was referring to how the above poster can find out about the relative danger of propane and ammonia and get some real understanding. Got it now?

I was referring to the paragraph I quoted, in which you were discussing making ammonia. I think you actually understand that.

You didn't know we were discussing making ammonia without fossil fuels, and you made a big fool out of yourself. As follows:

It doesn't come as ammonia. It comes as something like oil or natural gas, then you get hydrogen out of that, and then you make ammonia out of the hydrogen. It's an extra step

Comment: Re:Ammonia fuel (Score 1) 117

by floobedy (#47636725) Attached to: New Process Promises Ammonia From Air, Water, and Sunlight

Don't guess or ask. LOOK IT UP... No, and for a very good reason. It doesn't come as ammonia. It comes as something like oil or natural gas, then you get hydrogen out of that, and then you make ammonia out of the hydrogen. It's an extra step

Why don't you try LOOKING IT UP by reading the actual article before commenting? The article (and the discussion) is about making ammonia without oil or natural gas, using a process other than Haber Bosch.

The first version always gets thrown away.

Working...