{"id":817,"date":"2009-11-02T14:22:49","date_gmt":"2009-11-02T14:22:49","guid":{"rendered":"http:\/\/scientopia.org\/blogs\/goodmath\/2009\/11\/02\/free-energy-from-air-sorry-no\/"},"modified":"2009-11-02T14:22:49","modified_gmt":"2009-11-02T14:22:49","slug":"free-energy-from-air-sorry-no","status":"publish","type":"post","link":"http:\/\/www.goodmath.org\/blog\/2009\/11\/02\/free-energy-from-air-sorry-no\/","title":{"rendered":"Free Energy From Air? Sorry, no."},"content":{"rendered":"

After the
\nfiasco<\/a> that was my flame against the downwind faster than the wind
\nvehicle, you might think that I’d be afraid of touching on more air-powered
\nperpetual motion. You’d be wrong :-). I’m not afraid to make a fool of myself
\nif I stand a chance of learning something in the process – and in this case,
\nit’s so obviously bogus that even if I was afraid, the sheer stupidity here
\nwould be more than enough to paper over my anxieties. Take a look at this –
\nthe good part comes towards the end.<\/p>\n

<\/p>\n

What this video is about is one of the more novel approaches that
\nI’ve seen towards emission-free vehicles. Instead of using electricity
\nprovided by a battery, an Indian company has developed a car that operates
\non compressed air. It drives the pistons of an engine by allowing the
\ncompressed air to decompress, and then it uses the motion produced to drive
\nthe wheels of a car (for motion), and a small electrical generator (for
\nthe vehicles electronics, instruments, and accessories.) It’s a really
\nclever idea. And there’s absolutely nothing magical about it: a compressed gas
\ntank is just another way of storing energy: it takes energy to compress the
\ngas into the tank; some of that energy is given back when the gas is
\nuncompressed. The neat thing about the compressed air vehicle is that
\nthe gas tank weighs less than the batteries of an electric or hybrid,
\nand it doesn’t have all of the nasty caustic chemicals that are in
\na typical battery. The tank can be filled in under a minute at a
\ncompressed gas station, or overnight by plugging it in and running
\nan electric compressor. And it can go for around 200 miles at
\n50-60 mph on a single tank. So it’s a reasonably practical car. Certainly
\nnot what you’d want for long-haul driving, but for commuters, it’s
\npretty terrific.<\/p>\n

Of course, marketing drones are never satisfied with a simple good
\nidea. Just being good isn’t good enough.<\/p>\n

Now, I’m all for being creative about mocking idiots. It’s
\nfun coming up with ways of rephrasing their bullshit to demonstrate
\nhow stupid it is. But in this case, I just can’t do it. I can’t
\ndo anything better than what they’ve done themselves. In the smarmy
\ntones of the voiceover guy, starting around the 2:45 mark, they
\nconclude the video with the following:<\/p>\n

\nThe air car isn’t cost free to operate, because it does take some energy to
\ncompress air – but interestingly, MDI has created a generator powered
\nby compressed air. Which presents a tantalizing possibility: what if
\nthat generator was onboard the car? Then one day, perhaps the
\ncompressed air that runs the cars will also run a generator to
\ncompress its own air. A car that runs on air, and constantly
\nrefuels itself! Round a round, a perfect circle. Perpetual motion.
\nA no-cost fillup ever. Not one iota of pollutants, ever. And a cute
\ncar. All for about $15,000. That’s a future car.\n<\/p><\/blockquote>\n

They admit<\/em> that they’re trying to sell you a perpetual
\nmotion machine! And they don’t understand that there’s anything wrong
\nwith that. How could I possibly say anything to make them look
\nstupider?<\/p>\n

For the sake of pedantry, I’ll walk you through the problem with
\nthis, and all other perpetual motion machines.<\/p>\n

It’s an unfortunate fact of our universe, but any time you change energy
\nfrom one form to another, you lose some. No matter what you do, you
\nalways<\/em> lose some. It comes down to thermodynamics, which is how
\nphysics describes energetic interactions. The laws of thermodynamics can,
\nnon-mathematically, be sumarized as: “You can’t win”, “You can’t even break
\neven”, and “You can’t quit the game”.<\/p>\n

The first rule tells you that you’ll never get out more
\nenergy than you put in. So the perpetual motion story doesn’t work,
\neven under the first rule. You have some<\/em> quantity of energy
\nstored in the compressed gas. You use some<\/em> of that energy
\nto make the car move, and you use some<\/em> of it to run the compressor.
\nYou’re going to run out: you’re putting less energy back in to the
\nair tank that you’re taking out of it, because part of it is moving
\nthe car. So even if you had a perfectly efficient system,
\nit wouldn’t matter. In fact, with a perfectly efficient compressor,
\nrunning the compressor would be a no-op – it would do exactly nothing.
\nEvery bit of energy that it drew from the compressed air in the tank would
\nbe returned to the tank as compressed air – so it would be as if it weren’t
\npart of the system. But the car would still be draining energy.<\/p>\n

The second rule tells you that you can’t even get out as much energy as
\nyou put in. Any time you use energy to do work, any time you transfer energy
\nfrom one from to another, some of the energy gets wasted. So even if you never
\nwanted to move the car – you just wanted to keep the tank full of compressed
\ngas – you’d lose. When you take the energy in the compressed gas, and you use
\nit to spin a generator, what you’re doing is changing energy from its stored
\nform in the compressed gas, to a mechanical form which pushes the generator,
\nto an electrical form. Every step of that involves loss: decompressing the
\nair, pushing the generator, generating electricity from the generator,
\nusing the electricity to produce mechanical energy to drive the compressor,
\nand using the mechanical energy to compress the air. So just the closed
\ncycle: cycling the air out of the tank, into the generator, and then using the resulting electricity
\nto drive a compressor to refill the tank – will end up, in short order, with
\nan empty tank.<\/p>\n

And the third rule? It says you’re stuck: you can’t create a system
\nwhich doesn’t have to follow the first two rules. If you’re in this universe,
\nyou’re pretty well stuck with this. There is no free energy. There is no
\nsuch thing as perpetual motion. You’ll always get less energy out of a system
\nthan you put in.<\/p>\n

If you look at the way we really produce energy, we use systems where
\nlosing a whole of energy is just fine. Part of the reason that oil is so
\ndamned valuable is because it contains a huge<\/em> amount of energy for
\nits mass, and it’s easy to extract that energy. The fancy way of saying that
\nis that gasoline has a tremendous energy density. There’s roughly 46
\nmegajoules of energy per kilogram of gasoline: that’s a hell of lot of energy!
\nThere’s enough energy in it that it more than makes up for the effort of
\ncarting it around, even if we use it very inefficiently. Typical gasoline
\nengines operate at less than<\/em> 20% efficiency – meaning that the amount
\nof energy from the gasoline that actual gets translated into mechanical energy
\nmoving a car – is less than one fifth of the amount of energy released by
\nburning the gas. Even with 4\/5ths of the energy going to waste, gasoline is a
\nremarkably efficient energy carrier for us.<\/p>\n

The challenge in all alternative fuel sources for vehicles is that
\nwe need to find ways of storing energy that give us something like the
\nenergy density of gasoline, and which don’t cost a ridiculous amount
\nof energy to “fill up”. The very best electrical batteries that we’ve
\ndevised have an energy density of just 2.5 million joules per kilogram – a
\nbit under 1\/20th the energy density of gasoline!<\/p>\n

Lots of companies are looking at really interesting ideas for how to do a
\nbetter job storing energy for driving vehicles. Compressed gas is a good idea;
\nat the pressure that’s being looked at for cars (around 4,500 pounds per
\nsquare inch), it’s got a respectable energy density: about 4 million joules
\nper kilogram. And the engines that are built to run off it get around 18-20%
\nefficiency – roughly the same as gasoline engines. In terms of energy density,
\nit’s still pretty awful compared to gasoline – but it’s significantly better
\nthan even the best battery! And there’s good reason to believe that we can
\nwork out storage for gas at higher pressures than that, and that we can boost
\nthe efficiency of compressed gas engines by at least a little bit. So this is,
\nat least potentially, a serious, viable technology.<\/p>\n

But it’s not free energy. And when you tell lies about a technology,
\ngetting people to believe that in things that are too good to be true, all you
\ndo is set things up for failure. If someone can produce a really practical
\ncompressed gas car for a reasonable price, and it’s 20% efficient, and
\nrequires you to refill the compressed air tank by plugging it in in your
\ngarage every night, it would be absolutely brilliant<\/em>. People like me
\nwill beat a path to you door to buy one! But if you’ve told people that once
\nthey buy it, it’ll be free and perfect and will generate its own fuel by
\nmagic, then they’ll be serious pissed off at the electric bills that they’re
\npaying to refuel their supposedly free-energy car – and you’ll have successfully
\ntransformed it in the minds of your customers from something brilliant to
\nsomething incredibly disappointing.<\/p>\n","protected":false},"excerpt":{"rendered":"

After the fiasco that was my flame against the downwind faster than the wind vehicle, you might think that I’d be afraid of touching on more air-powered perpetual motion. You’d be wrong :-). I’m not afraid to make a fool of myself if I stand a chance of learning something in the process – and […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[5],"tags":[],"class_list":["post-817","post","type-post","status-publish","format-standard","hentry","category-bad-physics"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p4lzZS-db","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"_links":{"self":[{"href":"http:\/\/www.goodmath.org\/blog\/wp-json\/wp\/v2\/posts\/817","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.goodmath.org\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.goodmath.org\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.goodmath.org\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.goodmath.org\/blog\/wp-json\/wp\/v2\/comments?post=817"}],"version-history":[{"count":0,"href":"http:\/\/www.goodmath.org\/blog\/wp-json\/wp\/v2\/posts\/817\/revisions"}],"wp:attachment":[{"href":"http:\/\/www.goodmath.org\/blog\/wp-json\/wp\/v2\/media?parent=817"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.goodmath.org\/blog\/wp-json\/wp\/v2\/categories?post=817"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.goodmath.org\/blog\/wp-json\/wp\/v2\/tags?post=817"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}