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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."
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.
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?
Those solar panels, wind turbines, penis pumps etc had to be manufactured somehow and that manufacturing process creates emissions. "Carbon offsets" is a joke, wake up people! Any emission is an emission.
>>>all those Prius owners don't really seem to care about Lithum strip mines
Prius cars don't use lithium. They use nickle and hydride, and when disposed are no more harmful than throwing-away coins and water. (Although recycling the metal would be better.)
"I disapprove of what you say, but I will defend to the death your right to say it." - historian Evelyn Beatrice Hall
"Carbon offsets" is a joke, wake up people! Any emission is an emission.
I hold all my farts in sir!
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
The problem of humanity is one of the capture, storage, and application of energy.
Gasoline is a fantastic medium for energy storage: it's a better battery than any battery we know how to cheaply produce and service, and that's why we use it. But the energy capture function for gasoline [getting the energy into the gasoline] sucks. And the energy dispersal/application of gasoline has some environmentalists pretty upset.
Nature gives us many ways to store energy now and release it later. The chemical combustion of gasoline is one such mechanism. The desire of a compressed gas to push forcefully against its container is another such mechanism. The strong nuclear bindig energy is a particulary potent and pervasive mechanism. The specific heat of water is yet another.
The fundamental mechanisms of energy storage have been known about for a long time. Taken as a complete system to let humanity accomplish some goal, we are concerned with how we capture the energy, how much of it we can store [and at what cost], and how easy it is to get it back out in a form condusive to the sort of work we want to do with it.
As technology changes we must continually re-evaluate the end-to-end story for a particular aqcuisition/storage/application energy cycle. We may find that we are willing to tolerate a 100 fold decrease in energy storage performance for a 200 fold increase in acquisition efficiency and a qualitative improvement in application performance.
For instance, if i live in arizona and i have a sterling-engine powered air compressor that pumps my 50G tank to 100psi after 12 hours of sunlight, and this lets me go about 10 miles with no consumption of anything other than sunlight... I'm interested. If i commute 5 miles each way, I can get to work and back using nothing but solar energy. And unlike with PV panels and electrical batteries, a guy with a pipe threading die and a welder could build refueling system in his garage, out of stuff that has zero environmental impact whatsoever.
I think that's cool. I'm obviously playing fast and loose with the numbers. Since the kJ/m^2 of solar radiation is known at gridsquares all over north america, you could actually make some ballpark efficiency guesses about peices of the process and plug in real numbers to my hypothetical example. Even if reality is 1 mile @ 30mph after 8 hrs of sunlight.. that fits _some_ usage profile.
It used to be that every farm in North Dakota [where I live] had a windmill powering the farm. Then they disappeared and became an anachronism paying homage to a bygone era. Now windmills are dotting the countryside again. It didn't get windier here.
What changed?
The physics of energy capture, storage, and dispersion have always been the same; our efficiency and the context of the problem space continue to change. As such we must constantly re-evaluate what we did in the past against the realities of today.
My opinions are my own, and do not necessarily represent those of my employer.
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.
But you could just as easily have that windmill power a turbine to generate electricity to charge the battery in your electric car and get a far higher energy density leading to more mileage per charge and per each day's wind. I think that's the point that's being made. There's lots of clean ways that can generate energy -- any of which can be used to compress air, but why add that extra unnecessary step in the middle when it's just an added inefficiency?
Easy. Use solar panels to power the factory.
"...Air Cars" is an amazingly deceptive headline :(
I thought this was going to be a story crushing my hopes of owning a flying car.