[Diy_efi] Hydrogen

Fri Sep 8 01:55:30 UTC 2006

Some interesting conversation here about hydrogen. I'm not an expert, but
I've got quite a few years of experience in this area.

First, we designed built and operate the hydrogen station in Phoenix for
Arizona Public Service (APS).

http://www.aps.com/my_community/FutureFuels/FF_1.html

Hydrogen is generated via electrolysis (yes--expensive) and stored in ASTM
hydrogen cylinders. One great big unit for 150 psi storage and two smaller
tanks for 6000 psi storage. Each is made out of mild steel. They do have a
finite life, but it's a decade or more. We  also clean and store CNG from
the city mains and dispense that as "pure" CNG or blends of hydrogen. This
station is licensed by the city of Phoenix for selling fuel--one of only a
few hydrogen stations so licensed to sell fuel. It's been operating for 3-4
years now with no significant leaking or safety problems.

We have four hydrogen-fuele vehicles on-site and 8 more nearing completion.
The F150 in the picture on the above website is one of those four. See here
(http://www.etecevs.com/  --  find link on left side for Hydrogen Truck) for
the most recent design that we completed with Roush Industries. All these
vehicles are internal combustion for simplicity. See
http://avt.inl.gov/hydrogen.shtml for some reports on hydrogen and blended
fuel vehicles.

The state of the art these days in storage is Type 3 or Type 4 cylinders.
Type 3 have an aluminum lining with a carbon fiber overwrap. Dynetek is a
primary supplier of Type 3 (www.dynetek.com) Type 4 have a polyethylene
liner with a carbon fiber overwrap. Quantum Technologies (www.qtww.com) is a
supplier of Type 4 tanks. The standard these days is 5000 psi, but R&D is
taking place on 10,000 psi storage. Powertech Labs in BC, Canada is a leader
in Hydrogen/CNG test and development of gas systems (see
http://powertechlabs.com/cfm/index.cfm?It=900&Id=74 for some pictures of the
testing they do). Type 3 and Type 4  tanks have to undergo a series of tough
tests in order to be certified (CSA and TUV at this point). There is a
ballistics test in which a tank is punctured by a 30/30 round. In most
cases, there is a very brief flame, but the gas jet puts out the flame in
much the same way that oil rig fires are put out with explosives. Another
test is the "bonfire" test. Yup--build a fire and put the tank on the fire.
The thermally operated relief valve will open and vent the gas before the
tank cracks--a controlled leak rather than a high-pressure bursting. Then
there are crush tests and high pressure tests (4 times nominal rating).
There are no leaking issues with these tanks. I've stored H2 in them for
months on end with no loss of gas. There are currently specifications for
mounting similar CNG tanks which isn't a real engineering feat.
Specifications are under development for hydrogen systems, but there aren't
many deviations from the CNG rules.

Texaco Ovonics (or whatever they're called these days) is developing a solid
oxide storage system for hydrogen. I've not read up on this, but it is
supposed to delivery higher H2 density than liquid H2. It requires energy
input to get the hydrogen out and is quite heavy at this point.

Sierra Lobo is a company that develops and manufactures liquid gas storage
systems. They have been working on a system that can store liquid H2 with
very little evaporative loss.

As for fittings, the gold standard is Swagelok or Parker stainless steel
compression fittings:

http://www.swagelok.com/search/find_products_home.aspx?SEARCH=/search/Tube+F
ittings+and+Tube+Adapters/id-10000212/type-1

When installed correctly, these form a very tight seal. No appreciable
leakage over months of time. We also used orbital welding at the H2 plant,
but that was mostly as a test to determine the econmomics and efficacy of
welding vs. fittings. The tubing that is used is typically 316 stainless
steel with a wall thickness appropriate for the pressure. No embrittlement
with stainless, although we did get a batch of tubing that was corroded on
the inside as a result of an improper pickling treatment.

As for engines, we have seen no ill affects from the hydrogen gas. Of
course, one would use hardened valve faces to deal with the heat of
combustion. Lean mixtures are currently used to minimize NOx production and
keep temperatures reasonable. Quantum Technologies sells an injector for
port injection systems. There are a couple of companies working on direct
injection injectors, but nothing commercial yet (BMW does research in this
area). As there are no carbon molecules, CO and CO2 production is nearly
zero (some production from the combustion of the oil film). We recently
tested our HICE Silverado at Argonne National Labs and found that CO and CO2
emissions were below measurable levels and NOx was below that of the base
gasoline engine. Water production may be an issue for the sump oil, nothing
conclusive yet. Just today, we were awarded a contract with DOE to conduct
30 months of durability testing on these HICE trucks which will include 100
hours of dyno operation (alternating between max power and max torque)
followed by a teardown and materials analysis. We will also monitor the
durability performance of these engines in the field, inlcuding oil analysis
at regular intervals. Our experience so far with the existing vehicles
indicates that only the prototype components (injectors, coils) suffer
durability problems.

As for safety, I'm more comfortable around H2 than gasoline or propane. H2
dissipates (up) so quickly tha it's hard to maintain a concentraton at or
above LFL or LEL. Yes, hydrogen burns near invisibly, but you can hear the
gas escaping and readily feel the heat. (I've been told that the current
practice in industrial production plants is to hold a straw broom in front
of you if you suspect a fire). The flame is usually tightly constrained and
tends to go up. Gasoline is heavier than air so it will pool on the ground
in confined areas. The liquid stuff just runs and splashes everywhere,
creating more vapor to burn. Our city Fire Inspector tells us that they
respond to a gas station fire once per week on average. As I tell people who
are interested, we just have to get accustomed to working with Hydrogen.
We've all grown up toting around 20 gallons of liquit Napalm in our trunks
(boots) so we have very little concern (probably less than we should as
victims of the Crown Victoria gasoline fires will attest).

Now, don't ask me if Hydrogen is the fuel of the future because the jury is
not impaneled yet.

Garrett

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
Behalf Of Bill Washington
Sent: Thursday, September 07, 2006 5:16 PM
To: diy_efi at diy-efi.org
Subject: [Diy_efi] Hydrogen

Gents,
    Some years ago I saw film of a demonstration comparing the safety of
cylinders of liquified Hydrogen vs LPG.
the cylinders (of similar volume) were setout on a weapons range and an
incendiary projectile was fired into each one to simulate a fracture
resulting from a vehicle collision.

The result:
The Hydrogen vented in a rising jet of (invisible) flame - yes hot but
not instantly catastrophic - anyone close by would have had a chance to
escape.

The LPG cylinder exploded instantly in a very large explosion which
would have obiterated anything/everything in a 20-30 yard radius and
severly damaged anything over a considerably larger area.

The conclusion presented was that the hydrogen was much safer, however
we have many LPG cars on the road and very few hydrogen .......

Yes 'manufacturing' and storage are an issue - the Huge pressures
involved not the least of them .....

I don't know, however that demonstration keeps coming to mind in view of
the comments and opinions that have been shared recently ....... I would
like to hear from someone with expertise and experience in the gas industry.

Regards
Bill

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