“I remember when the candle shop burned down. Everyone stood around singing ‘Happy Birthday.’”
—Steven Wright

This past Monday, June 25th, was my birthday. I’m pretty hard to buy for it turns out. If I really want something, I don’t usually have the patience to wait for my birthday or the holidays to get it as a gift, I just go and buy it. Also, my life is so busy that there’s little chance for someone to spring a surprise on me either.

That’s why I was quite pleased with one particular gift I received on my birthday. It was just a little gesture from someone I work with (I won’t say who, but if you ever call my office, chances are this individual will be the one answering the phone.) We don’t usually exchange gifts at the office for birthdays, but this person knows how much of an environmental activist I’ve become in the last few years.

So when she gave me a gift bag I didn’t know what to expect, but inside was a clock. Now I have lots of clocks, but this one was different. It doesn’t require any electricity or conventional batteries to power it. This digital clock requires nothing more than tap water to supply its energy.

I’ve reviewed high school level chemistry quite a bit over the last few years because I’ve wanted to make sure I understood electricity and batteries well, so I know in general how batteries work. I tried to explain how batteries work in my book in greater detail than you’ll find is in there now, but the description became too onerous and detailed for the average reader so I took much of that section out. Suffice to say, I’ve learned from experience that a detailed explanation of how batteries work in any great detail is not in the cards.

So in brief, an electrochemical battery produces a current from ions that result from a chemical reaction. Two metals are involved, a cathode and an anode. For example, nickel and cadmium are what make up the Ni-Cad batteries in common use today.

But you don’t always need a specific chemical reaction to get ions moving. Tap water has all sorts of ions in it, which is what makes it “hard.” And what ultimately contributes to the formation of scale in our pipes. And why we buy salt for our water softeners to help eliminate these ions.

In the case of my new water-powered digital clock, the ions come right from the tap water I filled it with. There are two separate halves to the chamber, with a metal plate in each half.
Water isn’t the direct source of power, but it serves as the conducting agent to complete the electrical circuit for the clock. The metal plates extract energy from the various particles that are naturally found in the water.

The electricity is being produced by the difference in electrode potentials of the anode and cathode (the two metal plates) which are in the water. A slowly dissolving piece of zinc serves as the source of energy that ultimately powers my birthday clock. The lifetime of this clock will vary depending on the amount of zinc it has, anywhere from months to years. Since the clock only draws a very small amount of current, I’m optimistic I’ll have it for some time. (I’m not planning to use the alarm clock that is one of the functions it has available as well.)

I can appreciate that for the most part, this is a novelty for eco-minded people like me. But when you think of the number of clocks out there that only serve as time pieces and therefore need very little power to run, it would be amazing if we could replace most of them with clocks that run solely on the power of electrolytes found naturally in hard water.

Innovations like these need more attention, I believe.