New Method To Generate Electricity from Water

spaceling writes "The BBC reports reporting on research published in the Institute of Physics Journal of Micromechanics and Microengineering of the first new method of generating electricity in over 150 years. Larry Kostiuk and Daniel Kwok 'created a glass block, two centimetres in diameter and three millimetres thick, containing about 400,000 to 500,000 individual channels...[and] generated about 10 volts with a current of around a milliamp. This allowed the team to successfully power a lightbulb.'" This has also been covered all over the place.

Comments

A hype?

[hankwang]

This story looks like it's hyped. The device converts a flow of particles caused by a pressure difference into an electrical current. The paper itself (PDF, you probably need to be a subscriber, but the abstract should be accessible for everyone) shows efficiencies between 0.0001 and 0.04. The higher number is only obtained if the external load is matched to the device within a factor 10, i.e., the device looses the pressure difference if you don't use the current.

If we take one liter (1 kg) of water at a pressure of 30 cm, then the energy contained is 2.94 J, of which 0.12 J will be available as electrical output. By comparison, a 1500 mAh NiMH battery can store 6500 J. The efficiency of the water battery can probably be improved, but let's face it, for small volumes and reasonable pressures, the stored energy density will never be very high.

electricity generator != energy source

[JulianOolian]

It's a new method of generating electricity, not a new way of storing energy or an energy source. The energy would have to come from somewhere else, and since the idea is pretty new, I doubt that anyone knows in much detail how (or if) it will work out in practice.

I suppose you could either recharge a normal battery by pumping the handle your handy, portable water-generator for a few minutes, a bit like a baygen radio.

Or, you could store the water under pressure and let it out through the device to get the energy back out.

Re:So now we end up fighting wars over water?

[Spy Hunter]

The article title is misleading. This appears to be a new way to generate electricity from a pressure difference, using water flowing through small channels. It is not a method of generating electricity "from water," it is a method of generating electricity with water. The BBC article is guilty too, they misleadingly call it a "power source" when it is clearly a power storage technology (unless you have pre-pressurized water, maybe from geothermal activity or something). These few sentences from the article reveal the true nature of this discovery:

What Professor Kostiuk and his team have achieved is create a kind of turbine device that does not have moving parts. "Efficiency is a fraction of 1% and right now we are trying to fully understand the characteristics of such devices. The real goal is to find ways of improving its efficiency to around four to 16% to compete with other energy sources."