OT: plain water and salty water to generate electricity?

[Adrian C]

Just musing on the idea that the humble loo in the house could become part of a household power plant?

(BTW, yeah old news, was reading an old magazine...)

[Man at B&Q]

For once, I agree with Harry.

All the world's rivers to generate 13% of world demand. We might even achieve .13% if we really tried. Add to that the resources used to build the power plants and it's clearly greenwash ecobollox. Switching a few lights off would do far more good.

MBQ

[H. Neary]

It sounds very feasible. Personally I prefer the resistance power generation technique though. It uses researched and documented data relating to the electrical noise given out by high value resistors. As the resistance inreases the Voltage due to noise goes up, all you do is rectify the noise using fairly fast diodes and you generate power.

The disadvantages are that to get ac you need an inverter, and as temperature can raise the value of the resistors, you may need an additional resistor bank to drop the output Voltage.

HN

[Andy Wade]

:-) Bzzt - the noise power available from a resistor depends only on its temperature and the bandwidth and not on the resistance value. The available power is kTB - Boltzmann's constant times absolute temperature times bandwidth. Then of course your load must be at a lower temperature, otherwise its resistance will feed the same amount of power back to the 'source'. Otherwise you would violate the 2nd law and could invent perpetual motion.

Oh and BTW the thermal noise voltage across high value resistors is less then you would expect due to the shunting effect of the inevitable stray capacitance.

The thermal noise is already AC...

[Gib Bogle]

As with all power generating systems, the installation cost is crucially important. Maintenance costs can also be significant (think of Fukushima).

[The Natural Philosopher]

But sadly will be negated by the noise in any load you connect it to..