From today's Electronic Telegraph:

ISSUE 1412, Wednesday 7 April 1999

Plug in the bath to power TV set, By Aisling Irwin

A SCIENTIST who thinks that we waste too much energy is powering his television set with electricity generated by his bath water.

The system patented by Prof Michael Rowe, of Cardiff University, works by letting hot bath water trickle along a pipe which almost touches another in which the water flows at room temperature. This picks up heat from the hotter pipe.

Between them is a series of semiconductor thermocouples. Each device has a circuit made from two wires of different materials welded to each other at each end. If the two junctions are kept at different temperatures a current flows within them. As long as the bath water pipe has a substantial amount of heat to impart to the other pipe, electricity will flow along the devices and can be put to a variety of uses, including charging a battery.

Prof Rowe said: "Sixty per cent of the energy we use is discharged as waste. Heating bath water is totally wasteful because you just discharge the water. You're heating something up only to throw it away. Instead, you should just pause for a minute and think that there is a hell of a lot of power that went into heating it up in the first place."

Prof Rowe's work has been used to generate power on deep space missions, such as those of the Voyager, Gallileo and Ulysses craft. He said the drawback was that the efficiency of thermocouples was only 10 per cent. "But when you start considering that it is a free fuel you realise that efficiency is not a major consideration."

He wants to show people that they can adapt their homes to become energy friendly. Thermocouple devices could be used to harness waste heat from car engines and refrigerators, he said. On aircraft, where the difference in temperature between outside and inside can be 70C, there is great potential for generating electricity.

Prof Rowe, an electrical engineer, has patented a thermo-electric generator which extracts enough waste heat from a domestic central heating boiler to provide electricity for the circulating pump.

Work is under way to develop commercial designs which will generate electricity from waste water on a much larger scale, in particular by making use of the water heated up to 90C during the manufacturing of steel.

-- Old Git (anon@spamproblems.com), April 07, 1999

Answers

In about 10 years of electric generation from hot bath water, tou could maybe shine a flashlight for ten minutes.

-- Jubilation T Cornpone (skeptic@doubt.com), April 07, 1999.

I believe that the heat source for the Deep space missions that did produce enough power to be useful was radioactive, not exactly household bathwater.

But a nice note in any event, wouldn't it be nice if we could repeal the laws of thermodynamics, and make ideal engines.... It won't happen in my lifetime.....

-- helium (heliumavid@yahoo.com), April 07, 1999.

John Galt lives!

-- who is (johng@l.t), April 07, 1999.