Author Topic: Solar Generated Hydrogen  (Read 4957 times)

guest22972

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Solar Generated Hydrogen
« on: August 04, 2018, 01:52:51 PM »


Because I haven't got enough half finished projects to apply to my minimal motivation, I have started another one. A hydrogen Generator.
Was touched on in a discussion earlier but I have put it into practice. I made a small scale one and tested the gas a bit and as pure Hydrogen, it's not much different to LPG. The browns/ HOHOHO gas is completely different and in my mind dangerous but I am only using the Hydrogen with this and the Oxy is going off to enhance the atmosphere.

ATM I have an over supply of Solar power on my main array and have to apply a Dump load to avoid over voltage.Tthought it was mainly due to trying to pump too much power down the wiring but that didn't quite add up as it went voltage high well under what the cable  is rated at and what I pulled through it with no unusul voltage drop.
In reading up on this I'm finding it's quite a widespread problem due to the lazy arse power Co's not maintaining their equipment right and having a very wide variation on power standards.  Although the standard is 230, up to 253 at the point of use is acceptable yet the standards now limit inverters to 255.
Good way to stop people being too self sufficient and not paying enough to the power co's.

Instead of sinking this power into boiling water just for the hell of it, I want to turn it into Hydrogen and store it potentially to use on a stove at night.
Efficiency is not that important because anything I get is better than the 100% loss I have right now.

My gas generator seems a bit unique.  Not seen anything like it on the net.  I got a 240L plastic blue drum and cut the top off. Got a 110L dum and cut the bottom off. Fitted a Ball valve in the top and sealed it absolutely air/ gastight.  Seems way bigger than anything else I have seen on the net.
On the outside of the small floating Drum I put a steel plate about 20x30Cm. This is the Anode that generates the oxygen that is released.
On the inside of the drum I put a same size plate as the cathode to generate the Hydrogen.

Put about 100L of water in the big drum and mixed in  maybe 300G of KOH.  Opened the valve in the top, sank the drum about 60% Depth. Didn't add more water because I can't find my bag of KOH again so I didn't want to dilute the water too much.
Connected the contraption to the 2 broken panels on the roof which still work fine and it made gas.  And that's where the questions start.

It's not making near the gas I -expected- but I don't know if my expectations are realistic.  Don't know how much gas, not sure, rough guess, 10 L day. Maybe less, no real way to measure.

 Observations:

The 2 panels were feeding in around 19V -22V @ 4 XX amps.  General measurement was 130W

I hooked up the 3 Kw array which was open circuit 340V. That fell all the way to about 30V and gave about 200W over all.  The voltage/ power drop really surprised me because in the inverter it was producing about 900W at the time.  Yeah I know about the lower voltage and all that but 300 odd to 30?
Maybe the electrolyte does need thinning to let the Voltage come up and the panels get more on their curve.

Today I got a 30A 3 Phase rectifier and hooked that up to a pwm. Then things really got confusing.
AC going in was 250V. DC coming out open circuit  was around 300.... which didn't seem to add up.  Thought meter was on the Fritz but 2 More meters read the same. Put that down to no cap and the pulsing in the output.
Connected to the electroliser and again Voltage plummeted to around 15V DC.  My Meter was reading 16A @ 247V on the AC side ( which it sure as hell wasn't pulling)  but only 336W  dc which again didn't make sense.  Pretty sure the amps were right, the wire on the DC side was smoking hot after a few min and the unsunk rectifier was getting well up on temp too.  The AC voltage on the Rectifier after the PWM was down to 19-20V which again didn't make sense.  When I took the load off, was back to 250.

Now some questions that I would think were basic but I can't find answers too.....

In production, what matters, the surface area of the plates or the amps you pump through the thing?  My surface are isn't huge but I am getting the amps in there so would more plates do anything but make the " Resistance" larger?

Adding KOH will also increase the amount of amps that can be pumped in but do I need surface area for the gas to form on or is it reliant on the energy input?

Do I need equal plate area? If I put one plate on the oxy side and 10 on the hydrogen side, is it the same as If I had one on both sides or will more plates make more hydrogen gas?

I measured the output of the 2 Panels and got a bit over 6A. I measured the amps when connected to the plates and got 4.7 so I concluded the electrolyte and plate area is reasonable.  I could increase the plate area x 3 with no problem if it's going to make a difference.


I wasn't very impressed by rectifying the AC, thought I'd have a boiling cauldron but the bubbles I'm seeing on the oxy side are pretty Piddling. I did wind the power up to a KW but still nothing to write home about and nothing like the boiling I'm seeing on some YT vids but then I see they are pumping 5Kw into their generators to get that.  Ideally, I want to be able to dump about 750W. Not sure if putting a cap across the DC will help With the output.
Do I need Polarized caps for that or will  normal motor Run caps suffice?

Tomorrow I was thinking to get a DPDT and wire it so normally the power is going straight to the inverter. When the Voltage monitor is engaged, One array will send the DC to the gas generator so the power drops but is put to use.

I -could- be doing better than I thought. Before I have bubbled the gas into water to get a visual indication of production. This time I'm just catching it in a floating  drum in a bigger drum. Maybe I need to weight the floating drum down and connect a tube and bubble the hydrogen in water and get an idea that way?

I left the gas machine on a battery charger tonight and it was measuring 36W on the AC side so I'll see how much gas I have tomorrow.
Atm, I can't see this generating enough gas to cook a meal at night even if it is fed 5-700W for a number of hours.  Maybe I need a lot more plates or electrolyte but I'm thinking what matters is the amps more than anything. Is this right or am I missing something?

Perhaps my excess power would be better heating an element to keep a Bio/ Gobar gas drum up to temp and I'd get more usable Fuel that way?


ajaffa1

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Re: Solar Generated Hydrogen
« Reply #1 on: August 06, 2018, 09:38:13 AM »
Hey Buddy, I played with hydrogen production about ten years back, You are right to separate the two gases, as combined they are very dangerous. It is possible to significantly reduce that danger by thinning the mixture with regular air. there is a company that makes and sells gas cutting equipment that runs on Browns gas produced on demand.

I would advise against too high a current as this causes the electrolyte to heat up and could cause it to boil. Much better to go for lots of small cells rather than one great big one. What material are you using for your anode and cathode? Steel will very quickly corrode and contaminate your electrolyte causing the current draw to increase, with no increase in gas production. I tried various grades of stainless steel but hit the same problem. Platinum is used in commercial production but the cost is prohibitive.

I tried and had some success using the carbon cores out of used zinc acid batteries.

Bob

BruceM

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Re: Solar Generated Hydrogen
« Reply #2 on: August 06, 2018, 06:46:26 PM »
Regarding your hydrogen generator; you have a few things which seem to contradict convention for successful generators.  First, with only two plates, and no neutrals between them, anything over 2 volts is just heating the water.  If you look into dry cell hydrogen generators, you'll see that they are much safer, and better ones will generate about 0.5 liters per minute of separated hydrogen at around 240 watts (12V, 20 amps). The big advantage of the "dry" design is that plate connections are dry- there is no chance of a corroded electrical connection causing an explosion of the Brown's gas.  The addition of neutral (not electrically connected) plates between anode and cathode allows division of the applied voltage so that only 2 volts per gap exists; any overvoltage just heats.  For more gas production, more surface area is needed.

Reversing polarity in an iron or SS plate design will allegedly blow off the crude from the anode, extend life of the plate assembly and restore gas production rate.  Rust build up on the Anode apparently slows gas production , but dry designs from the 1930-1940's did use iron plates. 

For efficiency, current leakage from the plate edges through the electrolyte is a big factor.  This is a big plus for the dry cell designs also. 

It's a pity that hydrogen doesn't turn to liquid at a reasonable pressure.  It makes storage an expensive proposition unless you have access to large numbers of large propane storage tanks (and the room to place them) at bargain prices.


« Last Edit: August 06, 2018, 09:37:48 PM by BruceM »

BruceM

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Re: Solar Generated Hydrogen
« Reply #3 on: August 07, 2018, 04:15:06 PM »
The gas generated is proportional to surface area and current.  The plate material does affect production rate, as does the concentration (conductivity) of of the salt solution.  Plate material affects production rate primarily due to oxidization at the anode which reduces effective plate area.  Gold, platinum, titanium or graphene coated copper are lovely but not very practical for the DIY'er.  There is a problem with highly toxic chromium oxides (hexavalent chromium) that makes stainless steel of at least some grades a very serious health issue.  Solution salt concentration improves conductivity and can increase production but also increases corrosion and decreases plate life.

Any voltage above 2V is just wasted in heat.  If your volts must be 30V, then 17 plates total will give you 2 volts per plate.  8A will do it, just not at the max possible rate.  The "neutral" or not electrically connected plates between the outside, electrically connected plates will divide the voltage down for you, and one side will be anode and the other cathode, always anode facing cathode, starting at one connected end.  The alternative is to use a Buck converter to convert to a lower voltage at correspondingly higher amps.  You might be able to find a bargain converter that fits the input range of voltages from your panel.

The plates should be relatively close to each other or you're wasting energy heating the conductive solution.  Heating is NOT helpful, as it puts water vapor with the gasses.  The edges of the plates allow current leakage through the solution which is not producing gas and just heats the solution.  Think of it as trying to only allow current a straight path from face of anode to cathode. Even sealing the edges with a coating or rubber band is credibly reported to help reduce heating.   

It is tough finding good practical info on hydrolysis because of the vast amount of garbage.

An anode tube within a cathode tube eliminates the edge issue, but plates seem easier and you aren't concerned with efficiency so much anyway.  Coating the plate edge plus a band inward with acrylic is reported to noticeably improve efficiency/reduce heating.

Refrigeration compressors can do 500 psi, and so can propane tanks.  At those modest pressures hydrogen embrittlement of the steel tank is not a serious issue. The volume of tanks required is going to be quite large since the hydrogen will remain as a gas.  I wonder what your winter gas volume requirement would be to do all your space heating via hydrogen, and how big of a tank farm that would be!

I had similar ideas to yours regarding an on-demand self regulating submersion of scrap aluminum in lye bath as a hydrogen generator.  A design challenge for something simple and effective because of the corrosive nature of the lye, and the heat generated in the process which melts thermoset plastics.  If both heat and gas can be used, it becomes even more appealing.  The inherent energy stored in aluminum is enormous.








BruceM

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Re: Solar Generated Hydrogen
« Reply #4 on: August 08, 2018, 01:58:35 AM »
The poor efficiency and high cost of durable hydrolysis of water is the Achilles heel of solar hydrogen. That and the high cost of the lithium hydride for more compact storage.  We regularly spend billions on weapons and bomb development but funding for cleaner energy research is at the token level.

Woodsmoke from controlled burns and wildfires is bad here now, I haven't been able to open up at night for 4 days and it's 81F this afternoon in my house. (95F was the high.) I sorely wish I had built a water chilling system for cooling my small house already.  Brown air and heat have me struggling, health wise.





oldgoat

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Re: Solar Generated Hydrogen
« Reply #5 on: August 08, 2018, 01:02:34 PM »
I notice on the news today the CSIRO have developed a filter to convert ammonia to hydrogen and have been able to fit it in a car. For your next project Glort you can set up a conversion plant to turn your excess hydrogen into ammonia and start up a filling station. You have most of the necessary plant Hydrogen Nitrogen from the air one of your famous burners for the heat. You only need a dive compressor for the pressure.

ajaffa1

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Re: Solar Generated Hydrogen
« Reply #6 on: August 14, 2018, 12:13:30 PM »
Been there, done that, burned the tee shirt. Blew the shed windows out once. Very dangerous stuff.

I`ve often wondered if it would be possible to do electrolysis on something like WVO. This should produce much more hydrogen and much less oxygen along with a good amount of carbon dioxide which should act as burn retardant.

Many years back there was talk of a carburetor that did something similar and returned very impressive MPG figures, think it got killed off by the oil companies.

Bob

mike90045

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Re: Solar Generated Hydrogen
« Reply #7 on: August 14, 2018, 02:29:02 PM »
you only need   few % of air to make it explosive, and it has a very wide range of explosive mix.

Hydrogen possesses the NFPA 704's highest rating of 4 on the flammability scale because it is flammable when mixed even in small amounts with ordinary air; hydrogen gas and normal air can ignite at as low as 4% air due to the oxygen in the air and the simplicity and chemical properties of the reaction.


Mixtures

    "The flammability limits based on the volume percent of hydrogen in air at 14.7 psia (1 atm, 101 kPa) are 4.0 and 75.0. The flammability limits based on the volume percent of hydrogen in oxygen at 14.7 psia (1 atm, 101 kPa) are 4.0 and 94.0."
    "The limits of detonability of hydrogen in air are 18.3 to 59 percent by volume"[6]
    "Flames in and around a collection of pipes or structures can create turbulence that causes a deflagration to evolve into a detonation, even in the absence of gross confinement."

(For comparison: Deflagration limit of gasoline in air: 1.4–7.6%; of acetylene in air,[7] 2.5% to 82%)


The Hindenburg airship burned, it did not explode.  It's suspected that the aluminum powder paint was a major contributor to the tragedy, but it was not hydrogen exploding or burning, hydrogen flame is invisible (it burns blue in the UV range) and if it had exploded, the bystanders would be deaf.

dieselspanner

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Re: Solar Generated Hydrogen
« Reply #8 on: August 14, 2018, 06:01:26 PM »
You don't have to muck about with chemistry to get a good fuel air explosion, the US was at it in the late '60's, dropping a ton of propane at a time.

Look up the Pave Pat BLU 72 bomb..........

Cheers Stef
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mike90045

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Re: Solar Generated Hydrogen
« Reply #9 on: August 14, 2018, 06:28:41 PM »
The awesome thing about a baggie of hydrogen with a whiff of air, is the explosion is so very closely coupled to Air, it's quite efficient at transmitting the shock wave,  no nasty steel casing or sawdust to get in the way

EdDee

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Re: Solar Generated Hydrogen
« Reply #10 on: August 26, 2018, 09:22:35 AM »
Hey Glort...

Rumor has it that the standard flashback arrestors don't work too well... Best I have used is a 'bubble type' arrestor... basically a bubble trap in the line, the inlet feeding into about 6 in below the water surface and bubbling up to the surface... any backflash and it forces a water column into the feed pipe, creates a plug and isolates the flame front from the storage side... easy to make and reliable too...

Way safer than those deathly oil burners with difficultly flammable fuels...

Cheers
Ed
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ajaffa1

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Re: Solar Generated Hydrogen
« Reply #11 on: August 26, 2018, 01:03:25 PM »
Hey Glort, please stop playing with this sh1t. I have seen the aftermath of a underground mine explosion
(methane). What kills the miners is the gas they have inhaled exploding in their chests, it`s not pretty.

If you want to go down the hydrogen route please approach a reputable and experienced specialist. You could probably convert a browns gas (plasma style) cutter to feed a bench top gas cooker but it would probably bugg*r all your wife`s cooking pans. If you got a leak it would blow the roof off your home and kill all inside.

Bob

ajaffa1

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Re: Solar Generated Hydrogen
« Reply #12 on: August 26, 2018, 02:12:02 PM »
Hey Glort, so glad you have decide that and early and unpleasant death is not for you.

There are some hydrogen fuel cell vehicles come onto the market soon. Perhaps we should be looking to buy the first ones that get wrecked and use the innards to power our homes.

Poo gas or biogas are doable but require too much biological matter to be practical in a small setup.

Floaty amusements sound like great fun but please remember that the recent Sydney train outages were caused by Helium filled kids balloons landing on the overhead conductors causing them to short out. I dread to think what would have happened if they were hydrogen filled.

Bob

BruceM

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Re: Solar Generated Hydrogen
« Reply #13 on: August 26, 2018, 04:35:29 PM »
1Kg of Hydrogen is equivalent to 1 US gallon of gas.  Sounds good so far since much better energy density by weight. Alas, at room temperature and 1 atmosphere (no) pressure, that's 12 cubic meters or 12,000 liters of hydrogen gas. 

If you pressurized it to say 150 psi (a nice pressure for a 2 stage air compressor) or roughly 10 atmospheres, you need a pressure vessel of 1.2 cubic meters (or 1200 liters) for every 1 gallon of gas equivalent of hydrogen.  A 1000 gallon or 3800 liter propane tank is about $3000 US or $2000 for a used tank.  Filled with hydrogen at 150 psi that would hold the equivalent of 3.2 gallons of gasoline, energy-wise.   So if you want to store up the equivalent of a couple hundred gallons of gasoline for winter heating, for example, you'd need 63, 1000 gallon tanks.  Obviously, you might want to bump up the pressure as high as your tanks would allow to reduce that number or store a bit more fuel.  If using new 1000 gallon propane tanks, that's $190K in tanks to store the hydrogen equivalent of 200 gallons of gas.

To store the equivalent of a 10 gallon gas tank (automotive) at 150psi you need a 12000 liter pressure vessel in the car, or a trailer with about three 1000 gallon propane tanks. Not very practical.

Commercially they use high pressure tanks, but they suffer from hydrogen embrittlement and must be replaced regularly.  Out of sight for the DIY'er.

Thus the interest in lithium hydride for gas storage instead of a big hydrogen tank farm. It allows a lot more gas to be stored at modest pressure in a much smaller tank.  It's still very expensive and not in common use. 

A synthetic gas derived from hydrogen which can be liquid at reasonable pressures comparable to LNG (synthetic methane) may be more practical.










mike90045

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Re: Solar Generated Hydrogen
« Reply #14 on: August 27, 2018, 01:36:22 AM »
Your storage tank of pure hydrogen, will not burn or explode.  But if you get >4% of air into it (not sure if that's air or O2) a backflash will make a big boom.  Pure, it does nothing, because there's nothing to combine with