Wednesday, March 30, 2011

Totally off topic post

I was having a debate on another blog about the hydrogen economy.
I created this post so the debate could move over here and not clutter up someone else's blog.

for rocket news we will be testing the printed SS motor this weekend, and we will be presenting at space access.

Also good luck to team armadillo and the tube rocket.


Paul Breed said...

Its all about energy.

Taking electricity from somewhere
and making hydrogen from water is ~70% efficient, then you have to store the hydrogen, either liquefy or compress this takes more energy.

Your end goal is to get the electricity energy you put in back at some later date. Currently the most efficient way (all others are worse) to get energy back out of hydrogen is a fuel cell.

So the electricity ->hydrogen -> store -> fuel cell -> electricity is 25% efficient.

The electricity -> battery -> electricity conversion is ~85% efficient.

So why would you ever choose hydrogen over a battery system if you have extra electricity you want to turn into hydrogen?

With a battery you get 3 times as much useful work for the same amount of electricty?

Also for the same energy storage the very best hydrogen system using exotic materials and expensive platinum catalysts will be about twice the size for the same energy as the best commercially available batteries.

So hydrogen is 1/3 as efficient more expensive, and twice as large why would you use it?

Lastly all hydrogen is is an energy storage device, not a source of energy, the original electricity/energy needs to come from somewhere.

Concepts are cool, numbers matter.



Ben Brockert said...

Thanks, Paul! We're really hoping it goes well. It seems like we're taking half of the shop with us.

Good luck with the hydrogen debate. It'll be a good energy source for terrestrial applications when they find a liquid hydrogen well.

heroineworshipper said...

Watching Carmack evolve down to the tried & true for the last 13 years makes you wish everyone would have focused all their web 1.0 money on exactly the tried & true instead of wandering for 13 years. The next step is obviously a traditional solid missile for suborbital flights. At least the tube name is original.

Anonymous said...

>>. It'll be a good energy source for terrestrial applications


Hydrogen is not an energy source, ok ? And its a crappy solution for energy storage, too.

Paul Breed said...

anonymous, Ben probably should have included a "sarc" tag,

"it will be good when we find a liquid hydrogen well...."

not happening soon.

Joe said...

@heroineworshipper, not sure how many classic missile designs are capable of hovering, so I am a little unsure of the validity of your comment. Seems to me that Armadillo has been refining the hovering rocket for the 13 year period. Designs change over time, but I do not see a radical departure.

Hydrogen is attractive to the Bay area crowd of folks (and similar ilk) as they seem to just love the idea of a car producing water as the exhaust and care little for the cost, but such is the case of California. Ignore 95% of reality to accomodate 5% that live near you. Fyeh.

Joe Mansfield said...

@Ben - love the Hydrogen Well comment. :)

And just to add a further point - almost all Hydrogen, certainly all commercially viable Hydrogen at this point in time, is obtained via steam reformation of hydrocarbons. Combined with the inefficiencies of using Hydrogen as a fuel, and the storage\energy density issues this makes burning H2 (or powering a Fuel Cell) substantially dirtier than just burning the hydrocarbon in the first place.


Joe said...

Let's hear it for corn based ethanol while we are at it. Green? Ever lived in California's Central Valley? Green is not really that green.

Anonymous said...

@Joe Mansfield: when comparing from well to car energy efficiency, hydrogen is more efficient than burning hydrocarbon fuel (esp. gasoline). Well to gasoline powered car power is about 20%. For hydrogen, it's in fact ~25%.

@Paul Breed
The main advantage of hydrogen is the ability to tank it at a gas station in 2min. It's not that fast with batteries.

Timothy J. Massey said...

Hydrogen has two advantages: refueling speed (as mentioned) and range. A car with 60 miles range and that takes *hours* to refuel (lke the Leaf) will never replace ICE-based cars. "I'm gonna pay *how* much for a car that can't go to Grandma's?"

However, the biggest problem with hydrogen is the *total* lack of infrastructure and the fact that hydrogen is just about impossible to store for any length of time.

As you said, neither hydrogen or batteries are a source of energy. In both cases you're pushing the fossil fuel energy consumption out of sight, but it's still there.

In the short term, I think the Volt is the most exciting: give up nothing and get a lot of the advantages of batteries. Unlimited range, yet zero fuel consumption for most people most of the time.

heroineworshipper said...

In times of oil scarcity, humans have always converted other carbon stores into diesel or gasoline. 1st comes coal. Then comes food. It's the path of least resistance that'll probably see us through our lifetime.

Paul Breed said...

Your not going to fill a high pressure composite pressure vessel in 2min.

Your going to have a chalange filling a liquid system that fast as weel as there are going to be chilldown issues.

10 min I believe, 2min, I don't.

QuantumG said...

Yes, I tell people who talk to me about liquid hydrogen rockets that they should actually take a look at how insanely painful it is to handle LH2. I can't imagine people driving vehicles with hydrogen tanks (liquid or not). Liquid petroleum gas tanks are bad enough.

Anonymous said...

I agree that pluggable hybrid is the way to go for a short term, but...

Well, I saw a CNG vechicle refuelling at a gas station -- pressure in a tank was 160bar (so 40bar less than proposed GH systems) and it certainly didn't take 10 minutes.
WRT LH difficulties then one should not directly translate rocketry to cars. Car tank has few orders of magnitude less stringent mass ratio constraints. So problems like distilling LOX from air could be dealt with significantly easier. BTW there exist real LH prototypes and the do work.

Timothy J. Massey said...

CNG is a practical alternative to gasoline largely because it might as *well* be gasoline. There's more of it, and more infrastructure, than any other alternative beside electric. But it's not really a fundamenal shift from gasoline. You're still dealing with crummy reciprocating engines with maybe 25% total effeicency.

Plug-in electric allows that fossel fuel to be burned at very near carnot efficiency and stored and used at near total efficiency too. Its big problem is transmission losses and its big inconvenience is charge time.

Hydrogen kind of combines these: electric propulsion like plug ins, and therefore high efficiency (no heat cycle in the car), fast refill times, unlimited range. But fuel cells cost a zillion dollars, and there is *zero* infrastructure.

I still don't see a better choice than plug in with range extender (a la the Volt). But a CNG based range extender would work fine, too: and it's probably no more energy-intensive to synthesize CH4 than H2, and in the case of CH4 there's a lot of natural gas to mine...

To me, the most important part is to get the heat cycle out of the car. The second is to use existing infrastructure. Electric helps with both of those.

Is there a cheap CNG fuel cell?

QuantumG said...

The difficulties of *handling* LH2 have nothing to do with the difficulty of developing LH2 rockets. Handling LH2 for *any* purpose is a dangerous and painful process.

Also, it's LH2, not LH.. that would be monatomic hydrogen - a totally different beast.

Anonymous said...

Monoatomic hydrogen could not be in a liquid form in any significant quantity. Then, hydrogen handling is a done deal. Problems like LOX distillation, material embrtittlement and flammability are known and solved. Gas stations for LH2 do exist now. Ways more problematic substances are handled on a daily basis.

Finally liquid form is not the only option -- compressed gas has better energy efficiency.

QuantumG said...

Anonymous, your "is not" reply is not convincing.. and what does LOX have to do with it? Why did you even bother posting?

Paul Breed said...

I think he was refering to the problem with LH2 where it distils liquid oxygen out of the air.

Making solid air, or drips of LOX....

Anonymous said...

What if you could genetically engineer a plant that produced hydrogen and stored it in pods that your could tap?
What if it did this with optimized photosynthesis?
You could go out to compressor hooked up to the hydrogen tree and fill the hydrogen tanks in your car.
Then it might work.


Rita Green said...

Hi Paul! This is going to sound rather strange, but I am actually trying to get in contact with your Dad. My Dad and your Dad were close friends and both pilots in Kodiak, Alaska together. I believe that your Dad and your Step Mom even came to Oklahoma to visit my Mom and Dad. I knew both your Dad and Mom, in Kodiak and remember them well even though I was about 10 at the time. My Dad recently passed away following a long battle with cancer and we wanted your Dad to know in case he had not heard. My Dad's name is William (Bill) Claborn and my Mom's name is Margie Claborn. I am Rita Green (formerly Rita Claborn). My Mom is currently in an Assisted Living Facility about 2miles from me and is doing as well as can be expected at almost 82. Please let me know if you read this post. My email address is Thank you. Rita

Anonymous said...

Yes, condensing out oxygen out of air is one of the problems with temperatures below its boiling point.

@Anonymous: in fact there is research in that direction. Some algas produce hydrogen instead of oxygen when deprived of sulfur. But the process is now muxh too costly to be useful.

Generally all alternate car energy storage stsytems have problems. Besides biofuels (which do have their share of problems, but technically work) Hydrogen is the only one technology which is known (and demonstrated) to actually work for things other than short distance travel. Batteries are all good other than they can't be recharged quick enough to be a viable option on the road.

Paul Breed said...

Somehow a fuel for cars (LH2) that drips fluid (LOX) that turns normal roads (Asphalt) into a contact explosive just seems like a bad idea.

CNG or LNG I can see. LH2 not so much,

Anonymous said...

@anonymous/steve. Is this in some way a "green" suggestion? If so when did the green people want to genetically alter / bioengineer anything? And how much acreage would that require?

@anonymous about battery charging time. How about multiple charge points, e.g. multiple small batteries that can be charged separately and then discharged in parallel and/or serial. Vehicle scaled inductive charging pads would eliminate cables. There is a lot of opportunity for better / more creative engineering in batteries. The big attraction of course is batteries don't care what the source of their input electricity is. Make it green, fine, make it dirty, fine. Control the energy production in large scale and let the battery do what it does. Get away from ICE and you move the issue to utilities and economy of scale comes in.

Paul D. said...

You can make hydrogen without going through fossil fuels OR electricity. This may be the best way to make hydrogen from solar energy. There are two approaches:

(1) Solar gasification of biomass. A company in Colorada, Sundrop, is pursuing this. Up to 1/3 of the energy in the resulting hydrogen-rich syngas comes from concentrated solar energy used to gasify it.

(2) Thermal water cracking. This has been explored for years for use with nuclear thermal energy, but solar thermal can achieve higher temperatures, opening new possibilities. The best competitor now is a cycle based on nickel/iron or cobalt/iron oxides deposited on alumina particles. During one half of the cycle, the particles are reacted with steam to make hydrogen and Fe(+3) compounds. During the other half, oxygen is driven off, reducing the iron back to Fe(+2). Recent advances in the chemistry have reduced the temperature needed by about 250 K, solving some materials problems that had held it up. Overall solar -> hydrogen energy efficiency is about 20%.

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