Mashed, boiled, baked or fried? You probably have a preference for your potatoes. Haim Rabinowitch, however, likes his spuds “hacked”.
For the past few years, researcher Rabinowitch and colleagues have been pushing the idea of “potato power” to deliver energy to people cut off from electricity grids. Hook up a spud to a couple of cheap metal plates, wires and LED bulbs, they argue, and it could provide lighting to remote towns and villages around the world.
They’ve also discovered a simple but ingenious trick to make potatoes particularly good at producing energy. “A single potato can power enough LED lamps for a room for 40 days,” claims Rabinowitch, who is based at the Hebrew University of Jerusalem.
The idea may seem absurd, yet it is rooted in sound science. Still, Rabinowitch and his team have discovered that actually launching potato power in the real world is much more complex than it first appears.
While Rabinowitch and team have found a way to make potatoes produce more power than usual, the basic principles are taught in high school science classes, to demonstrate how batteries work.
To make a battery from organic material, all you need is two metals – an anode, which is the negative electrode, such as zinc, and a cathode, the positively charged electrode, such as copper. The acid inside the potato forms a chemical reaction with the zinc and copper, and when the electrons flow from one material to another, energy is released.
This was discovered by Luigi Galvani in 1780 when he connected two metals to the legs of a frog, causing its muscles to twitch. But you can put many materials between these two electrodes to get the same effect. Alexander Volta, around the time of Galvani, used saltwater-soaked paper. Others have made “earth batteries” using two metal plates and a pile of dirt, or a bucket of water.
Potatoes are often the preferred vegetable of choice for teaching high school science students these principles. Yet to the surprise of Rabinowitch, no one had scientifically studied spuds as an energy source. So in 2010, he decided to give it a try, along with PhD student Alex Goldberg, and Boris Rubinsky of the University of California, Berkeley.
“We looked at 20 different types of potatoes,” explains Goldberg, “and we looked at their internal resistance, which allows us to understand how much energy was lost by heat.”
They found that by simply boiling the potatoes for eight minutes, it broke down the organic tissues inside the potatoes, reducing resistance and allowing for freer movement of electrons– thus producing more energy. They also increased the energy output by slicing the potato into four or five pieces, each sandwiched by a copper and zinc plate, to make a series. “We found we could improve the output 10 times, which made it interesting economically, because the cost of energy drops down,” says Goldberg.
“It’s low voltage energy,” says Rabinowitch, “but enough to construct a battery that could charge mobile phones or laptops in places where there is no grid, no power connection.”
Their cost analyses suggested that a single boiled potato battery with zinc and copper electrodes generates portable energy at an estimated $9 per kilowatt hour, which is 50-fold cheaper than a typical 1.5 volt AA alkaline cell or D cell battery, which can cost $49–84 per kilowatt hour. It’s also an estimated six times cheaper than standard kerosene lamps used in the developing world.
Which raises an important question – why isn’t the potato battery already a roaring success?