Of all the elements in the periodic table, Hydrogen has to be one of my favorite. It's abundant, lighter than air (the lightest element, actually), and best of all: it's highly flammable.
Hydrogen is a diatomic gas that burns rapidly in the presence of oxygen. When most things burn, they release carbon dioxide, a greenhouse gas that can have negative impacts on the environment, air quality, etc. But when Hydrogen burns, it produces nothing other than water vapor, making it an ideal clean source of energy.
This particular project does not produce pure hydrogen gas. Rather, it produces a mixture of hydrogen and oxygen often referred to as HHO. This mixture is extremely volatile, which makes it a fantastic fuel, but also very dangerous.
Electrolysis is the process of splitting big molecules into their individual elements by applying energy. In this way, we are putting electrical energy into the H2O molecules to split them into H2 and O2 or HHO. When these are ignited, they release that energy in the form of heat and kinetic energy from the combustion. It makes a nice loop, but just remember that we will never get more energy out of the combustion than we put in as electricity, the energy just takes a different form.
Rather than just construct this in a boring old PVC tube, I decided to paint it and add wooden retro sci-fi style fins with a nice dark stain. I'm not a terribly artistic person, but I've seen many variations of this project already, I had to make mine unique.
I'll divide this project into two main parts: the electrolysis cylinder and the wooden base.
To build the electrolysis cylinder, we'll need:
For the fuel:
To make the rocket ship base:
Before we begin, take a minute and research HHO gas.
Let's get building!
In this step I'm going to explain the process of electrolysis as well as everything you'll need to start producing hydrogen.
Let's start with the science:
Water is made up of two atoms of hydrogen bonded covalently to one atom of oxygen. The bonds between these atoms form as a result of combustion. To extract hydrogen and oxygen gas, we'll need to break these bonds with some form of energy. In this case, we'll be using electrical energy from a 12 volt power supply.
When these bonds break, the resulting atoms have a slight electrical charge. The hydrogen will be drawn towards the negative terminal and the oxygen will be drawn to the positive. (For best results, use DC current)
We can test the concept of electrolysis by connecting two bits of stainless steel to each terminal of a battery and placing them in a container of water. When an electrolyte such as salt or baking soda is added to the water, bubbles should form on each steel electrode. We'll use a more refined electrolyte solution for the final generator.
Now that we know what's going on, how do we apply that to our hydrogen generator?
Great question. It means we can create a more efficient design using less materials. If you've done extra research, you might have noticed that other hydrogen generators have dozens of steel plates. This one only has three and one of them isn't even connected to anything. Why?
I used only three to keep things simple. And only the outside plates are charged because that's the most efficient arrangement. What many people don't understand is that there is a limit to the efficiency of electrolysis. Any voltage exceeding 4 volts between each of the two gaps is wasted as heat. Using Kirchhoff's Voltage Law we can calculate, with basic arithmetic, that twelve volts across two gaps means six volts for each gap, two more than necessary with a total of four volts of wasted energy. Having an arrangement of dozens of plates with each plate electrified, as most other Instructables might show, is even more wasteful, with roughly 80% of the energy being wasted as heat.
The trick to a more efficient system? Neutral plates. Neutral plates increase the surface area and divide larger plate gaps into many smaller gaps. If this generator had two neutral plates instead of just one in between the charged plates, it would be much more efficient.
Technically speaking, this design is referred to as a "wet cell," which is much less efficient than a "dry cell" design. But dry cell designs are much more complicated so we'll be sticking with this setup for now.
Now that you know how this thing works, it's time to start building.
We'll start by cutting the length of 2 in. diameter PVC pipe to about 9 in. This will give us plenty of room for the steel plates. Test fit the PVC end cap, threaded adapter, and threaded end cap before we go any further.
Next we'll start preparing the steel plates. I had to cut each plate from a larger piece of scrap metal. Make sure each piece fits with a little room to spare on each side. Ideally, the two end pieces will be about 1.5 in. wide while the center plate is just shy of 2 in. All will be at least 5 in. in length. When each plate is cut, use a coarse grit sandpaper to roughen them up. This increases the surface area (making a more efficient reaction) as well as allowing the adhesive to stick to the steel. When each plate has been thoroughly sanded (front and back), drill a small hole near the top of each end piece where the copper wire will attach to the plate. Go ahead and attach wires to these two plates. Each wire should be at least 6 in. long with at least 1 in. of exposed wire to thread through each hole. Solder will not stick well to stainless steel, so wrap each wire tightly to make a good connection.
We'll need to put some space between each plate to prevent short circuits. To do this, I used some small nylon washers. Hot glue, though probably not the ideal adhesive, works just fine for attaching each nylon washer to the steel plate. Word of wisdom: do not attempt to use wooden spacers (as shown in the video). Using wooden spacers was a mistake.
When you've assembled a sort of multi-layered sandwich, be sure that not of the plates are touching. If so, they will cause short circuits and many other headaches! Re-glue them or bend them into a safe position. Test fit the plate assembly in the PVC pipe before you continue building.
Next we'll drill three holes in the top of the threaded end cap. The first hole will be for the hose barb. Drill a 1/2 in. hole in the center of the end cap. The two other holes will be for the wires attached to the steel plates. Drill two small holes (close to the diameter of the wire) on opposite sides of the threaded end cap.
If you plan on spray-painting the PVC components of the electrolysis cylinder, do it now. I used a nice metallic paint to make it look more sophisticated.
--- take a break to allow the paint to dry ---
When the paint is dry, we are ready to finish this part. We'll begin to finish this project by threading the two wires from the steel plates through the two small holes in the threaded end cap. allow at least two inches of wire to suspend the plates on the lower side, and roughly four inches on the upper side. Use hot glue to anchor the wires in place and seal any gaps. Remember that this thing must be airtight so that no hydrogen escapes out the sides.
Then screw the hose barb into the large center hole at the top of the threaded end cap. This also must not leak around the edges. Use thread tape, hot glue, or any other sealant to ensure nothing leaks.
Lastly, use PVC cement to glue the thing together. You may need to sand off a little paint at each end of the main PVC tube and on the inner edges of the end caps. Apply primer to each segment, then glue. Twist the pipes to make sure that they bind completely and do not leak. Everybody hates unwanted leaks.
Give the cement a few minutes to set and cure. Then sit back and admire your work so far.
Here's where a little creativity comes in to play.
When I completed the electrolysis cylinder, I thought I was done. I tested it (it worked great) and I couldn't wait to make some videos and put it on Instructables. But as I thought about it more and more, my mind went to work and began dreaming up visions of rockets powered by hydrogen fuel. Though I don't have the expertise to build a functional hydrogen-fueled rocket, there's nothing stopping me from giving my hydrogen generator a retro space-age look.
I cut some wooden scraps into a few basic geometric shapes, then arranged them until I found a fin configuration I liked. I then cut a larger version out of some nicer wood scraps and glued it together into a rotationally-symmetric configuration. A compass or protractor might be necessary to get this part right.
I won't give you specific directions for this step. If you'd like to see how I did it, watch the video. I would much prefer if you get creative.
Here's the easy part.
After trying a few different mixtures with some spectacular failures, I have finally found one that works.
Many similar instructables will tell you to use a salt water solution. DO NOT USE A SALT WATER SOLUTION! Salt (NaCl) will become NaOH and Chlorine gas (which is super duper toxic, like chemical weapons toxic).
Don't use tap water either. To my shock and surprise, there are many many many different chemicals dissolved in tap water that become un-dissolved when electricity hits them. This yielded a disgusting green-brown gelatinous mass after a few minutes. It also took some time to completely clean the inside of the electrolysis cylinder.
The easy and ideal solution is a mixture of distilled water and completely dissolved baking soda. For best results, heat about half a liter of distilled water in the microwave and add a tablespoon of baking soda. Make sure it dissolves completely and add a little more distilled water if necessary. When the final solution is completely clear, it is ready to be put inside the electrolysis cylinder. Go ahead and pour it in, make sure it doesn't overflow or come in contact with the copper wires, as copper will react with oxygen ions and form more nasty green stuff.
Now for the really fun part. But first, a quick warning:
HYDROGEN IS DANGEROUS
Great, now that we've covered that we can get on to the fun stuff.
I used a cup of soapy water to trap hydrogen gas in soap bubbles, as seen in the Part 2 video earlier. Always remove the vinyl hose from the bubbles before lighting any of them on fire. Also, wear eye protection. And ear protection, if you're popping large bubbles with fire. And never ignite hydrogen indoors unless you know what you're doing.
This project is not complete, and it might never be complete. But at it's current stage it is not capable of fueling an HHO torch, as the output simply isn't high enough. To build an HHO torch, we would need to build a second or maybe even third electrolysis cylinder, as well as some additional flashback protection.
I also plan on building a small, hydrogen-powered rocket launcher that would fire small lightweight rockets into the air. Nothing too sophisticated, but fun nontheless.
For more interesting projects and a few upcoming hydrogen videos, visit my youtube channel and consider subscribing.
Let me know what you thought of this project and leave suggestions for future projects in the comments below.