Could we harness energy from vertical pipes in the sea?

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.