There are articles and news items on the Internet about cars that run on water. Most of them are electric vehicles and the inventors claim that only water is needed to replenish or recharge the battery.

At the recent Shell EcoMarathon event in Changi, one of the booths gave out miniature plastic kits to build a model car that could run on salt water.

What exactly is the state of development of water-powered cars?

The sad truth is that water is not a usable fuel as many inventors have claimed.

The energy source in water is the hydrogen. However, to extract hydrogen from water requires energy.

This is what we learnt early in school and it is known as electrolysis.

Inserting a positive and a negative electrode apart in water causes hydrogen to accumulate at the negative electrode.

The released hydrogen can be used as fuel. But energy - in the form of electricity - has to be supplied in the first place. The nett result is an energy deficit.

The Shell model car comes with a small cell that uses salt water as electrolyte - a liquid solution for electron flow when a chemical reaction between the salt and metal in the cell takes place.

Both the salt water and the metal electrodes are consumed in the process. Hence, there is an abrupt limit to how much energy can be produced.

For a real-life car to run on this technology would require several hundred kilograms of salt water and frequent replacement of the cell.

Essentially then, there is no applicable technology today that can convert water to usable energy to power motor cars.

Shreejit Changaroth