Hydrogen Product By Photovoltaic Electolytic Cell

[Turtle]

I have used this setup as a demonstration of electrolysis of water into Hydrogen & Oxygen before, however I used a power supply and did not actually 'use' the gases other than show how they burn. This time, I'm using a photovoltaic solar panel for the juice and I intend on trying to use the gas for at least a little gas light.

In operation, fill the collection bottles with electrolyte (salt water) and cap them, then submerge them in the tub of electrolyte, secure them in place, and remove the caps. Place an electrode in the neck of each bottle and connect to the panel. As the gas is produced it displaces the electrolyte in the bottles.

I do have questions here. If the tub is shallow as the lower part of the drawing below, is the gas in the collection bottles at 1 atmosphere of pressure when they are completely filled? If I put the bottles completely submerged in a deep cell as in the dotted/grayed upper part of the drawing, will the pressure in the collection bottles be higher when filled than the first arrangement?

I have to make some supports for the bottles (they float away when they fill if you don't secure them! ) and I should be in production by tomorrow. Adieu!

[Turtle]

Decided to go with the KISS principle for holding the bottles; I'll put something on top of them when I have too. Here's the cell with the bottles full of electrolyte, the bright shiny copper electrodes, and the tub that makes the cell. The question now is not if this is slow, but just how darn slow is it.

YouTube - Electrolytic Cell Preparation 1

[Zythryn]

My understanding is creating hydrogen with solar cells is exceedingly slow.
I think there is some information about the speed of this process available regarding Honda's fuel cell test cars in California.
I would love to hear what you get for rate of hydrogen production.

[Zythryn]

Found it!

The system, when running exclusively on solar energy, can produce about 5,700 liters (at 350 bar) of gaseous hydrogen per year. This is enough to fuel one car for a year.

This is from http://www.ieahia.org/pdfs/honda.pdf

It uses a 8kw solar array for power and can use grid power as well for more production.

[Turtle]

Originally Posted by Zythryn

Found it!

This is from http://www.ieahia.org/pdfs/honda.pdf

It uses a 8kw solar array for power and can use grid power as well for more production.

I can't read the caption details on the drawing showing the whole setup. I'm particularly interested in how to pressurize the collected gas. Other than a pump, how do you find my idea to submerge the collection bottle?

My collection bottles have many tiny bubbles clinging to their inside walls this morning. It is cloudy, cool, and raining, and I measure 8 volts from the panel (panel is rated 5 Watts).
...
Will post updates, photos, & vids as seem appropriate.

It is the kind of gray, cold, wet NW day that I signed up for. 2" of rain in as many days. Nonetheless, the cell is bubbling away on day 1. Here's a clip, brightened for clarity.

YouTube - Electrolytic Cell Operating - Day 1

PS Crap! I edited instead of quoted!! Lost that bit to the aether.

[Turtle]

Breaking News.... I hate how every dingity danged story these days is 'breaking' news.

Let's call it an update. It is dark here now, 5:33pm PST, and I disconnected the photovoltaic panel propped in the South facing window behind the cell, to check if the outside lights produced any voltage; nada, zip, nothin'. With the multimeter at the DC voltage 2.5 V scale I saw no deflection at all.

When you got a meter out ya hook things up to it , so I went for the leads from the electrolytic cell and lo & behold a voltage of ~ 1/40 Volt. Will this voltage hold stable no matter the volume of gases in the collection bottles?

Oh, what to do with the Oxygen? I think I'll suck it out with a straw when the bottle's full for a 20 oz pick-me-up. ........

[Turtle]

Day 2: Noon - Everything is gray and not a patch of clear sky to be had, but the panel is happily providing a steady 15 Volts. As we might expect, there is more accumulated Hydrogen than Oxygen...nearly twice as much it looks like.

With the panel disconnected for the voltage check, I metered the cell again and had a surprising, if not shocking, result ; the meter surged up to 1/2 volt and then steadily declined over a minute or so to a bare level. Seems we have some capacitance in the cell as well.

That's all I got.

[Zythryn]

Very fun, thanks for the updates Turtle

[freeztar]

Originally Posted by Turtle

I metered the cell again and had a surprising, if not shocking, result ; the meter surged up to 1/2 volt and then steadily declined over a minute or so to a bare level. Seems we have some capacitance in the cell as well.

That's interesting. I guess that's quite beneficial for serving up a fairly constant voltage despite passing clouds.

[Turtle]

Originally Posted by Zythryn

Very fun, thanks for the updates Turtle

Danke. You know me...nuttin' butt fun.

Originally Posted by freeztar

That's interesting. I guess that's quite beneficial for serving up a fairly constant voltage despite passing clouds.

To clarify, the photovoltaic panel has blocking diodes which stop any current flow back into it. The capaciter-like discharge I mention is from the electrolytic cell while it was disconnected from the solar panel.

Also because of the blocking diodes, you cannot put the photovoltaic panels in series and produce a higher voltage, only in parallel to increase the amperage. Here is a nice discussion on the topic of the roles of voltage and amperage in electrolysis:

Electrolyzer - encyclopedia article about Electrolyzer.

Originally Posted by freedictionary.com

... A higher current flow (amperage) through the cell means it will be passing more electrons through it at any given time. This means a faster rate of reduction at the cathode and a faster rate of oxidation at the anode. This corresponds to a greater number of moles of product. The amount of current that passes depends on the conductance of the electrodes and electrolyte, though it also depends on how much current the power source itself can generate. Current also makes a difference in that it can shift chemical equilibria by sheer mass action. The processes in an electrolytic cell with just two or three reactants can become very, very complex. Most of the time it is best to search the literature to see what current density works best for a desired process. For instance, metals plated at a certain current density might form a durable and shiny coating on the substrate, while some other current density might form an excessively grainy, dull coating.

A higher potential difference (voltage) applied to the cell means the cathode will have more energy to bring about reduction, and the anode will have more energy to bring about oxidation. Higher potential difference enables the electrolytic cell to oxidize and reduce energetically more "difficult" compounds. This can drastically change what products will form in a given experiment. On a practical level, both current and voltage determine what will form in a cell. ...