Scientists who discovered a new way of generating electricity from water say they may have come across an alternative source of clean energy to rival wind and solar power. The breakthrough, which scientists say is the first new way to generate electricity in 160 years, could lead to batteries that use water instead of poisonous substances. The scientists made the discovery when they were investigating what happens when tap water is forced through extremely narrow glass tubes. Water squeezed down the tubes, each of which was narrower than a tenth the thickness of a human hair, generating a small electric current that ran the length of the tube. To produce a larger electric current, the team tried forcing water through a glass water filter that contained thousands of narrow channels lined up side by side. "When we took a syringe of water and squeezed it through the filter, we got enough power to light a light bulb," said Larry Kostiuk of the University of Alberta in Canada. "The harder you push the syringe, the more electric current you get." The current is produced because of an effect in the glass tubes. When they are filled with water, positively charged ions fixed in the tubes are washed away, leaving a slight negative charge on the glass surface. When water is then forced along the tube, the surface _ negatively charged ions in the water while positively charged ions are attracted down the tube. The result is a net flow of positively charged ions that sets up an electric current. According to Dr Kostiuk, no one has ever thought to use water to produce electricity in this way. "The last time someone came up with a way of generating electricity was Michael Faraday in 1839," he said. "So this is the first new way of generating electricity in 160 years, which is why we are so excited about it." Dr Kostiuk says water batteries might one day be used to power mobile phones and calculators, but admitted that the engineering challenges might make other applications more realistic. "You'd need to be sure it wouldn't leak, and you'd need to make sure it wouldn't freeze," he said. More likely would be to install the electricity-generating devices where water is already being pumped, such as at city water filtration sites, he said. "It could compete with wind and solar power," he added. What does the passage mainly want to tell us about?
A kind of solar power discovered by scientists. A kind of new energy source found in tap water. The breakthrough to generate electricity 160 yeas ago. A kind of new battery invented without poisonous substances.