In preparation of the balloon release I saw how it doesn’t work well and started working on a plan B. Plan B is to buy a BIG canister of Hydrogen and fill the rest of the balloon with that.
Couple minutes of Googling came up with a BOC page offering high Purity Grade Hydrogen bottles. It asks you to create an account before being able to see the price – which came to my surprise – surprisingly high!
So I started reading about the Hydrogen compression – finding following quote somewhere where I can’t find a source anymore (apologies to the original author).
Compressed hydrogen must be stored in specially designed tanks capable of withstanding the storage pressures, which can range from 17 MPa to 70 MPa. These tanks are usually made of steel. However, tanks made of carbon fiber lined with aluminium, steel, or specific polymers are used when weight is a consideration. When compressed, the density of hydrogen at 35.0 MPa is about 23 kg/m3 and at 70.0 MPa is about 38 kg/m3. This leads to an energy density of 767 kWh/m3 (27 °C, 35 MPa).
It also came with following graph, which is surprisingly in [bars], while quote continues below.
The volume of the storage tank is the biggest challenge, since the density of compressed hydrogen is lower than that of liquid hydrogen. Compression of hydrogen is an energy-intensive process which increases the overall cost. Estimates are about 6.0 kWh/kg for compression to 70 MPa, which leads to the CO2/kg of hydrogen stored to be high (approximately 1.3 kg of CO2/kg of hydrogen). However, compression only consumes a third of the energy that liquefaction does. In addition to the cost of compressing hydrogen, the cost of compressed storage tanks must also be taken into account. The cyclic loading of tanks, which tend to heat up as they are filled with compressed hydrogen, reduces tank life.
If you read through all that you can see that Hydrogen compression is quite a no-no in my shed-environment. I did a few calculations and I could potentially go with a 4m3 steel-enforced water tank which would be pressurised to 7 atmospheres – to be able to contain the same amount of Hydrogen as needed for our Phase 3 – 25m3.
13700KPa & 50L = 6m3
685KPa & 1000L = 6m3
Foreseeing quite intense family debate on this topic I went to the BOC page again and suddenly following offer appeared on a next page!
Grabbing Andrew (native language speaker) we walked in next day to the BOC store at Virginia and ordered one bottle. Invoice came with a bit different price (page stated that price is GST inclusive – BOC Virginia thought otherwise), but hey who wouldn’t sacrifice few dollars for a nice bottle of Hydrogen?
Interesting part about buying it came in the moment when the guy behind the bar asked if we have a gas trailer to carry it away, when I responded with confident “Of course… “. We’ve spent whole afternoon with Andrew trying to figure out what he actually meant with that and it wasn’t too positive – apparently it government wrote practically a book about dos and don’ts.
Asking Serge about an advice calmed me down – Serge was able to carry all his welding bottles in a car and while that was more then a few years ago I took it with a gentle disclaimer and kept asking. At the end Rob saved me!
This is a story of Rob Mataic!
I gave a call to Rob on Friday morning, 10 minutes later he picked me up in Sandgate with his Ute, carried me to BOC Virginia, helped me to retrieve the bottle, tied it on his Ute deck and carried it back to my house – quite surprising Veronika with his sudden appearance.
Huge thanks Rob I owe you another one now!
I asked Rob to take a picture of that outlet so i can get a pipe for filling the balloon.
Well, instantly couple of obvious problems appeared.
1/ how to release that Hydrogen from something what is pressurised to 137+ atmospheres (13.7MPa) (Did you know that Venus surface pressure is ~90 atmospheres?)
2/ How to store that “bomb” securely in a house full of kids.
I’ve learned a lot about high pressure bottles and it is quite a topic. Long story short this Hydrogen bottle comes with AS 2473 Type 20 outlet connection. Good reading here, but long story short Type 20 is same as Type 10 (typical Helium outlet), with opposite threading.
Asking all around I was strongly recommended to use a pressure regulator, unless seeing our house levelled to the ground. So checking with Google, it came with following Harris 825 Hydrogen Pressure Regulator, Vertical Inlet, Stainless Dia, 0-1000kpa – for quite bitter $338 AUD.
Some options came around and offers came down to $250 AUD, but still much more above my ten-bucks budget I was thinking of. I’ve parked this one as being an overkill for this situation. This however led straight to the problem 2/ safe storage.
Getting inspiration from “Transporting dangerous goods in Queensland” document – I’ve picked a place in a corner of our garage, where it is well ventilated and can be safely attached to the wall.
It took just few minutes of a virtuous work with a drill and all looks pretty good!
Our bottle will stay there safe till we’ll have a good use for it. I suppose that Hydrogen has to validity date so we are not in hurry now and we now have a high quality hydrogen for the stage when we’ll start experimenting with a fuel cells.
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