A modern team of Italian researchers has uncovered a device invented by fellow Italian G.D. Botto in 1833 that can be used to generate hydrogen with inexpensive, everyday parts. By reflecting sunlight from two parabolic mirrors onto a hollow tube wrapped in metal and filled with water, the device generates enough electricity to produce hydrogen through electrolysis. Theoretically, the device is so simple that anybody could build it in their garage.
In the original Botto device, alternating links of platinum and iron were connected in a chain that was then wrapped around a wooden rod. By heating one side of the rod with a flame, Botto was able to generate an electric current in the chain through thermocoupling of the two metals.
Botto’s original intent was to simply show that he could produce electricity using a thermocouple of two metals. Making hydrogen bubbles in water through electrolysis was his way of visually confirming an electric current was present. But, after uncovering the original Botto work, the modern Italian team realized the device had a different kind of potential in today’s energy-dependent world: a cheap way to make hydrogen without advanced manufacturing techniques using off-the-shelf components.
With some modern thinking, the Italian team was able to modify Botto’s device in rather ingenious ways. Firstly, they replaced the flame that Botto used to produce heat with parabolic mirrors to concentrate the sun’s rays on the tube. Secondly, they replaced the rather expensive platinum metal with copper. And thirdly, in order to create a greater temperature difference between the heated side of the tube and the cool side of the tube (greater temperature difference equals larger current), they ran water through the center of it.
The researchers estimate that, although the power output for their experimental device is small (only about 20 mW), it could generate enough current to produce hydrogen gas through electrolysis of water. Given that the device is scalable, I’m guessing it would simply be a matter of daisy chaining enough of them together to generate the required amount of hydrogen.
The researchers also suggest that rather than using a thermocouple of two metals, it would be more efficient to use a thermoelectric semiconductor to obtain a much higher power output. I’m just waiting for them to release a design on the internet so that we can all start experimenting with hydrogen production.
Image Credit: De Luca, R.; Ganci, S.; and Zozzaro, P. “Revisiting an idea of G D Botto: a solar thermoelectric generator.” Eur. J. Phys. 29 (2008) 1295-1300.