Your parents always said that eating right would give you a boost of energy, but they probably didn’t expect you to be literally generating electricity from your food! So how does the potato clock work? The key lies in two simple things: the chemical environment inside the potato, and the elements in the two probes you put into it.
Despite what it looks like, the power isn’t really coming from the potato, it’s generated by chemical reactions in the metals of the two electrodes you’re plugging into the spud. But without the potato’s delicious interior, the reaction wouldn’t work. To start with, potatoes are mildly acidic (and we mean very mildly, with a pH between 5.4 and 5.9; even maple syrup can be more acidic). As a reminder, a pH of 7 is neutral, 1 is extremely acidic, and 14 is extremely basic.
The moment you insert the zinc strip, it starts reacting with phosphoric acid inside the potato; the important part for us is that the zinc loses some of its electrons in that reaction. The copper strip is also reacting with the acid, but it’s looking to pick up those spare elections, so they flow up the wire from the zinc strip to the copper one. A flow of charged particles (like electrons) is literally the definition of an electrical current, so voila! Your clock is powered.
That’s the basics, but let’s step it up a notch. If the electricity is generated by a reaction between the environment of the potato and the metals in the electrodes, can you increase the power by changing either of those things? The answer: yes! In fact, both of them. And depending on what you’ve got around the house, these may even be things you can try at home.
Let’s start with the potato. A few years ago, researchers at the University of Jerusalem discovered that if you boil potatoes for eight minutes, you can boost the electrical production by up to TEN TIMES. They think that it works by rupturing the tissue membranes inside the potato, lowering their resistance and making the reaction more efficient. Using this method, they used a potato to power an LED light for 40 days.
You can also increase the amount of power by changing the materials the electrodes are made out of. Your kit uses zinc and copper because they’re readily available, and work well in the reaction. But more exotic materials can increase the electricity generated: for example, with electrodes of magnesium and gold, you get more than three times the power out of your potato! You can calculate how much electricity is produced by looking at a table of the standard reduction potential of different materials.
On the chart here, for example, you can see that copper has a potential of 0.34 volts, and zinc -0.76 volts. From the difference, you can calculate that the amount of power generated in their reaction is 1.1 volts. From this, you can see that with gold (1.5) and magnesium (-2.37), you can generate a whopping 3.87 volts!
| ELEMENT | POTENTIAL |
| Gold (Au) | 1.50 |
| Silver (Ag) | 0.80 |
| Copper (Cu) | 0.34 |
| Lead (Pb) | -0.13 |
| Nickel (Ni) | -0.26 |
| Zinc (Zn) | -0.76 |
| Magnesium (Mg) | -2.37 |
| Lithium (Li) | -3.04 |
You can also hook up a bunch of potatoes together to generate more power. Your setup uses two because 1.1 volts isn’t quite enough to power the clock, but by connecting the two potatoes in a serial circuit, you add their power together, so you’ve got 2.2 volts. And in fact, you can go farther than that! Three potato batteries hooked up together are usually enough to power an LED light, and one team of scientists linked four together to run their scientific calculators. If you’ve got an entire field of potatoes and some time on your hands, we’ve seen setups that link hundreds of potato batteries together. And according to some calculations, if you had about 300,000 potatoes you could replace a car battery!
Finally, one of the really fun things to do with your clock is find different foods (and drinks!) to use as power cells. Anything with an acidic environment should work, and you might be surprised at some of the foods that fit that criterion: lemons and cola of course, but also eggplants, strawberries, and cheese! Have some fun experimenting with the foods in your kitchen, and if you want to spark some ideas, here’s a chart of foods with their associated pH levels (remember, lower levels mean more acidic).
You can even get really creative, and try to can come up with entire meals that activate the clock. Breakfast, for example: will it work with pancake batter, maple syrup, and milk? With so many ways to continue experimenting with your potato clock, we hope it engages your curiosity – and helps keep you on schedule - for a long time!