Slashdot Mirror
Berkeley Engineers Have Some Bad News About Air Cars
cheeks5965 writes "We've argued before over compressed air vehicles, a.k.a. air cars. Air cars are an enchanting idea, providing mobility with zero fuel consumption or environmental impacts. The NYTimes' Green Inc. blog reports that the reality is less rosy. New research from UC Berkeley and ICF International puts a period at the end of the discussion, showing that compressed air is a very poor fuel, storing less than 1% of the energy in gasoline; air cars won't get you far, with a range of just 29 miles in typical city driving; and despite appearing green the vehicles are worse for the environment, with twice the carbon footprint as gasoline vehicles, from producing the electricity used to compress the air. Given these barriers, manufacturer claims should definitely be taken with a grain of salt."
How would you compress the air in the first place?
Fuck systemd. Fuck Redhat. Fuck Soylent, too. Wait, scratch the last one.
There appear to be two primary advanages of these cars: They're cheap to make and they don't directly pollute the city air. If the power plant is downwind they could actually improve the air quality in the city. You also get "free" AC, although heating the car is an issue. Since these are primarily targeted at cities like Mumbai the cooling is more important anyway.
I read the internet for the articles.
and despite appearing green the vehicles are worse for the environment
Compressed air is just a medium in which to store energy. The energy could come from solar panels on your garage. It compresses the air. The air powers you car. Zero emitions.
This is opposed to batteries which really aren't good for the environment, but all those Prius owners don't really seem to care about Lithum strip mines while patting themselves on their backs.
Hydrogen is yet another method of storing energy.
Just compressing air from solar, wind power, etc gives Zero emissions no matter if the efficiency is only 1% or 100%
The significant fact about electric (or hydrogen fuel cell), or electrically compressed air vehicles
is that electricity (and hence hydrogen via electrolysis, or compressed air tanks) can be generated
in all manner of relatively or completely "green" ways, whereas fossil-fuel transportation is
at least presently restricted to getting its fuel by digging up stored carbon from the Earth at
unsustainable rates.
So electric vehicles (or hydrogen fuel cell, or even relatively inefficient compressed air) vehicles,
are stepping stones on the path to a non-GHG producing future energy system.
So the "green-ness" or carbon footprint of these electrically based technologies should be
measured with two separate baselines:
1. What would their carbon footprint be if all electricity was generated with carbon-neutral generation
methods such as wind/solar/geothermal/hydro/wave/nuclear.
2. What is the carbon footprint assuming the US continues to maintain arguably the most carbon-dirty
electrical generating mix in the world.
Measured in this light, it can be seen that the complete issue is changing the electrical power source for the
US, in parallel with adopting one or multiple forms of transportation technology that is electrically based.
Either change without the other does not work. Both are necessary for effective improvement in emissions
reduction of transportation.
Where are we going and why are we in a handbasket?
Not on debunking this, because it's a completely ridiculous idea that anyone who's taken even introductory engineering thermodynamics should be able to debunk. Rather, they should get credit for going the extra mile and actually getting a paper out of the thing (and media attention!).
I mean really. There's perfectly good reasons why we're not using compressed air as a 'fuel', and it's not that we hadn't thought of it. The idea (and applications) have been around since the 19th century.
It occurs to me that a compressed air vehicle could be compared to a "cold" steam engine.
Have there been any scientific advances that could make steam engines in general viable for car sized engines?
I did an apprenticeship in Motor Mechanics for 4 years when I left school 25 years ago. I recall a question to the tutor back then about compressed air to drive a car. Here was his answer: Compressed air is not good as a primary driving medium, it is only good as a buffer(the storage tank) or where electricity might add risk. Examples being driving air tools in a pit below ground. By its nature, compressed air must pass thru constricted orifices. There is tremendous loss of pressure over distance. I recall our workshop compressor...very different from what you buy at a hardware store. Huge tank, dual motors, each on three phase power. The newbies job was to empty the water and oil traps from the Air Intake system. About 20 litres per day and about 200 mls of oil like fluid(The atmosphere in the workshop back then was a haze of car fumes and dust). We had 4 electric hoists and one compressed air hoist too. The air hoist could lift many times the wieght of the electric.
I think compressed air cars will serve a specialist role, operating in specific roles. Whether there is commercial visbility, I do not know. Aside from the modern buzzword of "Footprint", the technology to compress air is as old as stem and pistons. That wont change. Even on high tech air craft carriers, the landing restraints have huge hoary old compressed air pistons dampenening the jets planes. The tech below deck, keeps the ram clean and applies some lubricant periodically....just as would happen in steam train days.
In post Patriot Act America, the library books scan you.
Slashdot - news for idiots, stuff that's obvious
This is a surprise to someone? Who ever though this *could* work? Certainly not anyone with any knowledge of thermodynamics. The only compressed -gas systems that even have a chance of working are those that store the working fluid as a liquid, meaning it has to be able to be liquified at room temperature at a reasonable pressure (few hundred PSI at most). Otherwise the tanks are huge and heavy (meaning it will barely move under power) or they are small and heavy (meaning it has no range). Two excellent working fluid for this purpose are - wait for it - CO2 and Freon! Oops.
Brett
Compressing air can be done with any source of mechanical energy. Put a windmill on your roof, gear it down, and have it drive the compressor directly.
Come to think of it, having a sizable amount of compressed air storage in one's house would be handy. Great for dusting.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
As said in great grandparent post, compressed air and hydrogen are energy storage mediums. Wood is the same thing. Trees use solar energy to convert CO2 into carbon. When you burn the wood, you put the CO2 back into the air and get the energy back as heat.
It doesn't matter if we burn the wood for something useful, the trees dies and rots, or the tree is burned in a forest fire: at some point the carbon is coming back out of that tree.
These are designed to remove the *concentration* of exhaust gases from fuel burning from crowded urban areas. It isn't really that there are that much less overall emissions, just relocate where the emissions occur (although something can be said for having emissions controls at the generating plant). There's a lot of stop and go traffic, etc, most vehicles today sit at idle or run at some lower less efficient speed in city traffic. Air cars and electric cars shut completely off at "idle" and aren't wasting fuel sitting there in some traffic jam or at the stop light doing nothing as regards moving from point A to B.
That's the primary advantage here for short range urban vehicles as regards the environment. If you primarily do long trips, get a well tuned/ well built modern diesel for best mileage/less fuel burnt.
Nice graphic on this page that shows where the fuel goes with a regular car, idling accounts for almost 1/5th energy wastage today, with extra pollution concentrated then for no real reason.
http://www.fueleconomy.gov/FEG/atv.shtml
"...Air Cars" is an amazingly deceptive headline :(
I thought this was going to be a story crushing my hopes of owning a flying car.
Compressing air can be done with any source of mechanical energy. Put a windmill on your roof, gear it down, and have it drive the compressor directly
Translate this into practical terms.
Give me an estimate of the air car's speed, range, weight of cargo, weight of passengers.
Tell me how long it will take to refill the tank.
Get a deal for 100 megawatts at 50KV, line saturated to 70% of its capacity 24/7 except holidays,
Get a deal for 10 kilowatts at 110V saturated to 40% of its capacity in the evenings and 10% the rest of the time.
See how much you pay for KWh in the first case, how much in the second case.
Bulk trade rules apply to electricity much more than to normal goods.
Also, check how much a solar panel costs. About $1000/100W.
Considering about 15 cents/KWh energy, that's 1.5 cent/hour you save. That's 7.5 years for return of the investment, assuming no efficiency drop-off and all the infrastructure (inverter etc) for free. Now consider some 4 cents/KWh of energy a massive bulk customer like the solar panel factory pays, how long till that kind of investment is returned? 30 years? How well will the panels perform then?
Solar panels are a means of packaging bulk industrial energy into packges suitable for retail and reselling it to retail customers.
45 5F E1 04 22 CA 29 C4 93 3F 95 05 2B 79 2A B2
I own an air guitar and it's actually pretty sweet - I can make like I'm rocking out wherever I am. Whereas an air car ... I don't see the market. You're at a party and the music's pumping and you just decide to "air drive" to the shops? Not cool.
.. the wind does, that is.
Using a mechanical air pump driven by the wind makes massive sense to me, it is patently obvious. This method alone makes air power a win.
How we generate energy now for air cars now makes no sense, is patently stupid. Fossil fuel -> heat energy -> mechanical energy -> electricity over a lossy inefficient grid -> pumping compressed air -> filling up your car.
After logging in slashdot still does not take you back to the page you were on. It's been that way for 20 years.
Since when does a conclusive study demonstrating what you already knew was true constitute "bad news"?
Bad news: perpetual motion doesn't exist. Would it be good news if it did exist? With such a toy, an enterprising galaxy could tip the universe toward heat death. Maybe a supernova is just perpetual motion gone Sorcerer's Apprentice.
If you're in a troubled relationship and you finally have a big blow out argument, and one of you storms off into the night, is that bad news, or good news? If you defined keeping the peace as good news, isn't that how you got yourself into that situation in the first place?
Life consists of nested narratives. What's good at an inner level of narrative might be a complete disaster for a containing narrative. Is the discovery of a big new oil field good news or bad news? Good for Exxon, bad for Bangladesh? Good for me, bad for my children?
The one case where I really understand good luck / bad luck was an episode of the Sopranos where Corrado says "these things come in threes". Corrado suffers from a narcissistic sampling bias, and thinks the outcome of his own cancer might complete the trinity of two other deaths. There's half a dozen deaths in every episode, but since Corrado has a deep insight into bad luck that I personally lack, he's able to frame his fear in specific terms.
Bobby's inquiry, "With all due respect Junior, what do you care about the details?" is one of my favourite lines of the whole series. That's not the sentiment of a man dumb enough to marry Tony's psychopathic sister Janice, which is where I started to lose interest in the series. "Hey, let's shack up and double our screen time." Bad news: Bobby just married Janice, and now the show sucks. Actually, I didn't regard that as bad news so much as an unpleasant insight into the law of least redemption in David Chase's fictional hell.
What does "bad news" really mean? How about "I'm about to tell you something you won't like, so please take three deep breaths before pulling out your gun and shooting me"? I think it's a hereditary conversation tick we use to give the recipient's hominid brain an extra moment to distinguish message from messenger, or to give an air-car believer a moment of hesitation before prematurely ending it all.
I thought if you first converted it into ethanol, one pint could power days and days of hard pedalling.
I just checked these numbers. They are quite accurate, but interestingly, the difference is made up of almost entirely of taxes. The power company adds less than 10% to the spot price, so bulk seems to have little to do with it.
In my case the price is 9.33 euro cents per kWh. This is made up of:
Spot price: 3.81 cents (41%)
Added by the power company: 0.35 cents (3.7%)
Taxes and certificates: 5.17 cents (55%)
When buying in bulk, the interesting figure is the spot price. Where I live, electricity is traded on a public exchange (Nordpool), so you can easily check the price per MWh at any time.
Compressing gasses generates huge amounts of heat, which if not captured, is waste heat. Similarly decompressing gases loses heat - that is why aerosols are cold, and is how refrigeration works. Compressed air as a means of energy storage is a bad idea.
I used a table very similar to this one (but yearly instead of monthly)
http://www.eia.doe.gov/cneaf/electricity/epm/table5_6_a.html
15 US cents seemed to be about the average residential price, 4 cents was the low of the industrial - and considering the massive bulk purchase, the lowest pick seems fair here.
The $1000 was the first google hit for 100W solar panel.
45 5F E1 04 22 CA 29 C4 93 3F 95 05 2B 79 2A B2