Could a large magnifying glass be used to boil seawater?

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Emilio asked the Naked Scientists:

Dear Chris

If a magnifying glass can focus solar rays and heat some things up to the point of burning them, why can't a huge magnifying glass be used near the coast to boil seawater and cause the evaporation needed to produce fresh water?

In this case we wouldn't burn fossil fuels to generate the needed energy to obtain fresh water. And maybe some sort of dam can be built near the coast which can be filled with seawater independently from the rest of the ocean thus not affecting water temperature.

Sounds crazy?

Regards from

Ecuador Emilio

What do you think?



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Could a large magnifying glass be used to boil seawater?
« Reply #1 on: 30/10/2008 13:27:52 »
Yes it would work BUT glass absorbs a lot of radiated energy (not visible) so a reflector does the job better and would be a lot cheaper than a huge glass lens.
The reflector doesn't need to be that accurately made, either, if all you want to do is 'collect heat'. The 'spot', when focused, can be almost as large as the water container and you'll still get hot water. If you want a very high temperature, however, then the spot needs to be as small as possible and the reflector needs to be very accurately parabolic.
« Last Edit: 30/10/2008 13:31:52 by sophiecentaur »