Small-scale H2 tank refill station

[RedDevil]

Originally Posted by jamesqf

If you're electrolizing with DC, then H2 and O2 should come off different electrodes, making separation fairly simple.

In theory, yes. But it only takes a minute amount of vacuum or back-pressure to make the gas go down the wrong pipe. The objective was to pressurize the hydrogen; if the pump creates a vacuum on the hydrogen pipe it will suck in the oxygen too.

Also, some oxygen is dissolved in the electrolyte and will dislodge together with the hydrogen regardless of back pressure. That last one will not normally result in dangerous oxygen levels, but saying the appliance usually does not explode is not good enough.

To do it safely the electrodes need to be separated by a sturdy and airtight membrane.

[smallscaleH2]

Originally Posted by jamesqf

If you're electrolizing with DC, then H2 and O2 should come off different electrodes, making separation fairly simple.

Originally Posted by oil pan 4

The hho people use interlocking plates like a lead acid battery to get a lot of opposing plate surface are really close to each other. The H and the O come out pretty much on top of each other.

Yes, I read that the H2 will collect at the cathode (-), and oxygen will collect at the anode (+), so it's the anode (+) side where the oxygen needs to be discarded from.

Ok. So I'd need to make sure that the plates are air-tight sealed. I think that's not normally the case (the cells in the smaller electrolysers -the Ice blocks- might be air-tight sealed, but these contain many plates). The biggest electrolysers (101 plate electrolysers) have 101 plates (in a single "cell" ?) So it's probably not possible to seperate these off ?

Can someone look into this ? The 101 plate electrolysers have pdf's with schematics over at the pwm3g page.

Either one will do I guess; if I were to use ice blocks, I'll just need a lot more of them; the ice blocks can make 1 liter of gas per minute @12 amps, but I seem to understand it can make up to 5 lpm when boosting it to 25 amps ? Anyway, at 1 lpm, I'd thus need 10 to 15 ice blocks to replace a 101 plate electrolyser (that would increase cost a lot -840$ x 15 = 12600$ compared to 3000$ for the 101 plate electrolyser-), if it can make 5 lpm, cost would be 4200$. The latter's still seems reasonable.

I'd need to attain 3 lpm to match the Bauercomp compressor, 0,4 lpm to match the BRCfuelmaker, 1,4 lpm to match the Coltri MCH5, and 3,6 - 15,5 lpm to match the CORKEN.

So we'll need just 1 electrolyser, but several compressors.

[smallscaleH2]

Originally Posted by seifrob

as you have not filled in your location, I assumed you live in the U.S. Therefore I used Oregon average prices for fuel and kilowatt-hours : here and here. If you were so kind and let us know you live in the E.U., situation would be different.

Yes, I live in the EU.

Originally Posted by seifrob

have you read provided sources? Have you read my post properly? You need about 65 kWh to produce 1 kg of compressed hydrogen by electrolysis, and that amount of hydrogen equals roughly to 3 liters of petrol in contained energy.

I accounted for these losses, in my post (at the end) I wrote:
"so if you were to have say just 50% efficiency, you'd still have 1,766 euro"

33,41 kWh in hydrogen = 65 kWh required in electricity = 51,5% efficiency

[oil pan 4]

The distance you will get from 1kg of hydrogen is around 10 up to 15 miles.
Electric vehicles get between 2 to 5 miles per KwH.
I know which one I would pick.

[smallscaleH2]

Originally Posted by oil pan 4

The distance you will get from 1L of hydrogen is around 10 up to 15 miles.
Electric vehicles get between 2 to 5 miles per KwH.
I know which one I would pick.

10 to 15 miles (16 - 24 km) using a 1l hydrogen tank at what kind of pressure ?

Taking my previous calculations:
a 3 gallon CNG tank at 250 bar (which is going to be my standard tank unit) would be able to contain 11,35 kWh or hence 96 % of the energy in a 1 liter gasoline tank.

This 11,35 liter (=3 gallon) tank will bring me, at a fuel consumption of 6 liter gasoline/100 km, 16 km.
Calculation: (100/6) x 0,96 =16

Electric vehicles will obviously bring you much further, since you can pack in more batteries into the vehicle (they're smaller for a same amount of energy stored). But what if you already have a small vehicle around that uses an internal combustion engine ? Are you going to get rid of that engine and swap it for an electric motor + batteries, and spend that much money on it ? I won't. I just want to use that existing engine and run it on hydrogen then.

Seifrob mentioned fuel cells but I don't intent to use that. Rather I would just use an internal combustion engine. There will obviously be range limitations to this approach, but for city driving it would be sufficient. I guess the only remark you could make against this is that why one would need a motorised vehicle for such small distances (i.e. one could also use a bike) ? But I still think it's better then using a gasoline-powered vehicle for the same purpose.

[seifrob]

I see it as a lost case, but I will have another try:

From what I read, you are intendig:
1) build a "gas station" that will sell pressurised hydrogen to fellow neighbours
2) these fellow neighbours will use their present cars with kind of conversion kit - about the same way as many people here in Europe are buying LPG conversion kits

I will try not to mix energy and currency to the very end to save further confusion

Part 1 - "fuel" and producing it

"fuel" does not produce energy. It rather releases it, the energy stored in mollecular bonds. "Fuel" is anything that can release energy when you fiddle with it - you can break it to chemically simpler materials - for example burning wood is oxidizing cellulosis, and that produces water, carbon dioxide and some energy. Oxidizing hydrogen also releases some energy. (Many apologies to anyone who reads it, I know its very crude simplification).
Now, I repeat, the energy is only released. I was not created, it was "invested" into the matter when it was created. There is hidden energy of all these days Sun was shining apon mentioned tree in the campfire wood. In crude oil we release energy, that was "hidden" in it eons before we pumped it to the surface, so we can burn it. When you "make" hydrogen gas, it is you who "invests" energy to break bonds in water to break it to oxygen and hydrogen.
This article states you need about 50 kWh to make 1 kg of hydrogene (with current state-of-the-art technology). I am not going to verify it, you can do it if you want. That same article states you need additional 15 kWh to compress it so it is usable as automotive fuel. You cannot produce it for less, because it is the energy you MUST to invest into the water to break it. Do not ask about pressure you compress it, it is irrelevant. 1 kg of hydrogene is 1 kg at any meaningful pressure.
So - even if you have your gas station built for free and functional, every 1 kg of hydrogen you produce will add these 65 kWh to your electric bill. If price of electricity you buy is $0.1 per kWh, than for every kg of hydrogen you produce you pay $6.50. ymmw.

Part 2 - "fuel" and using it

As stated above, fuel is any matter that releases energy it is stored in its chemical bonds. You can find amount of the energy released by oxidation under term "enthalpy" in chemistry books. Wikipedia states it is 286 kJ/mol, what equals around 39,7 kWh in 1 kg of hydrogene. That means that if you oxidize 1 kg of hydrogene, you get ideally 39,7 kWh regardless how you make from oxygen and hydrogen water again.
So, your customer buys one kilo of hydrogen in order to release energy stored in. He can burn it, he can stream it through platinum mesh in fuel cell, he can take tweezers and manually join atomes one by one to form H2O mollecules (just kidding there). In doing so you get 39,7 kWh from 1 kg of hydrogen, and neither God nor your customers can get more because no more energy is stored in.

I am customer, who now drives a 40 MPG car. According to ecomodder converter I need rougly 1 kWh to move my car for 1 mile.
So - under ideal circumstances, if I managed to harvest all 39,7 kWh of energy hidden in 1 kg of hydrogene, I could move my car for 39,7 miles.

So - as a customer - I need to buy either 1 gallon of gas, or 1 kg of hydrogen

Now: Can you sell me 1 kg of hydrogene at the price of 1 gallon of gas?
It depends where you live, and your gas price and electricity price. - where did you get that 5 cents per kWh??


P.S
As - according to that article - current fuel cells can "harvest" 23,3 kWh and this is industry-proven most efficient way, I doubt you get more by simple burning the hydrogen in your engine. My estimate is that you get around 13 kWh, that means 13 miles per kilogram of hydrogene.

-- If anything is unclear, feel free to ask.
-- if anyone finds an error in my estimates, let me know please.

[oil pan 4]

I meant Kg not L. My bad.

[samwichse]

Originally Posted by smallscaleH2

10 to 15 miles (16 - 24 km) using a 1l hydrogen tank at what kind of pressure ?

Taking my previous calculations:
a 3 gallon CNG tank at 250 bar (which is going to be my standard tank unit) would be able to contain 11,35 kWh or hence 96 % of the energy in a 1 liter gasoline tank.

This 11,35 liter (=3 gallon) tank will bring me, at a fuel consumption of 6 liter gasoline/100 km, 16 km.
Calculation: (100/6) x 0,96 =16

16km is 9.94 miles.

A Ford Energi pack (C-Max or Fusion) from the junkyard will get you 20-25 miles of range and costs $800-950. The round trip efficiency from wall electricity to moving down the road will be about 6x what you're trying to do with creating burning hydrogen.

And if you only use half for 10-12.5 miles range, it weighs around the same as your H2 tank.

And you are much less likely to explode.

[smallscaleH2]

Originally Posted by samwichse

A Ford Energi pack (C-Max or Fusion) from the junkyard will get you 20-25 miles of range and costs $800-950.

And you are much less likely to explode.

I agree that if you would need just a battery, it would be cheaper. But you can't convert an internal combustion engine with just a battery, you need an electric engine then too. These generally cost thousands of $. Another issue is that not everyone has the skills and tools to do the conversion themselves (disconnecting and then lifting out an internal combustion engine requires a lot of costly tools, and skills). With the hydrogen conversion, you avoid all that.

Regarding the risk of explosion: using the proposed bubbler, spark arrester and lower tank pressure, safety is already limited (compared to H2 vehicles at 700 bar). To make it even safer, I was thinking you could actually mount the H2 tanks on your roof (using a roof rack, you could even cover it if you want slightly improved aerodynamics, and improve the esthetics -so as not to have it look like the Ghostbusters car-). This roof mounting should be safer than having the tanks in your trunk (as with regular CNG vehicles).

[seifrob]

Where (what country) do you live?

In my country, even relatively simple and safe LPG conversion is illegal to do-it-yourself. You are required to have it made in certified service center and you are subject to annual inspection. The LPG conversion itself costs about 1200 Euros, CNG conversion - which is closer to what you propose as you intend to use high pressure tank and valves etc. - is about 2500 Euros and legislative is even more strict, given 250 bar pressure and high flammability. So idea of "everyone can do it in his backyard" sounds near impossible to me, at least in the E.U.

On the other hand, you can buy inexpensive hubmotors and build something like Podride - with 11 kilometers range it is on the same level as hydrogene converted car - and wihout any government made obstructions.

-- Also, you face danger of explosion already in the process of making the gas, whether your customer has tanks on roof or not. I dare to say that cars with hydrogen tanks would be actually much safer than your gacility to bubble and compress it. HHO mixture can actually explode without any spark thanks to heating during compression.