[thedoc (OP)]

Could Thermo-Electric Generators be used as a major non-polluting energy source with vertical pipes in the sea, in the bottom of pipe, at depth there’ll be a temperature of about 4 or 5 degrees, the top end would of course be about 35 degrees.  Is that enough of a temperature difference?
Asked by Mike Donn


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[thedoc (OP)]

We answered this question on the show...



Laurie -   With some of the really efficient generators, even a temperature gradient that small can produce power.  The difficulty in this case is that you tend to want to apply the temperature gradient across a device an awful lot smaller than a pipe put into the ocean.  So the difficulty is getting the gradient across the right bit of the device.  But yes, even with those temperature gradients, you can get some power output.
Chris -   And then you'd have the energy embodied in making and deploying a system like that.  Often people don't think about that aspect of the equation. They may think "I can make a 5% saving over here" but then don't necessarily think about where the materials to make that solar cell come from, or how much it costs to buy those, and the carbon footprint of shipping them half around the world.
Laurie -   I think the cost of life is a big issue.  You have to produce the materials, they have to be uniform enough, they have to be of a good enough quality and then they need to be implemented.  It’s always a difficulty with that aspect.

[CliffordK]

The thermal gradient in the ocean would be difficult to deal with.  Because of the density gradient, it would take energy to pump cold water to the surface, or to pump hot water to the ocean floor.

One might be able to use something like a well insulated long copper bar.  But, that would be an expensive method to transfer very little energy.

There are a few substances that will contract when heated and expand when cooled.  Perhaps one could design something that would take advantage of this reverse thermal expansion, either to drive the movement of material for bringing cold/warm temperatures together, or possibly to create movement that could be directly used to generate energy.

However, perhaps the best method to utilize the temperature gradient is to utilize the ocean currents that are caused by the gradient.

[syhprum]

power stations using the heat difference between the depths of  the sea and the surface were in use in the early part of the twentieth century but as diesel fuel became available their use died out.