MovieChat Forums > Watermark (2013) Discussion > Next step: Desalination.

Next step: Desalination.

posted 10 years ago by virgiltx
5 replies | jump to latest

This docu did its job of showing us how water shapes us and how we shape it. The scale of water's criticality and importance was well emphasized, both for the aquifers depletion and the Xiluodu Dam project. They used clever new means of aerial photography to show it all in the real.

Now someone needs to follow up with a proactive oriented film about the only real answer to the massive, growing depletion problem, desalination. That's a big subject, but it doesn't get political attention like energy, defense and space.

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[–] melinda2001 9 years ago

it doesn't get political attention like energy, defense and space

The reason for that is sadly the fact that desalinization can't be a practical alternative to water management for anything beyond drinking water, for two big reasons. First is the prohibitive amount of energy required, and second is that water is very heavy, and there's no practical way to get it from the coastlines to the farms even if you could desalinize it. True, both are energy-related, but if the world is to be kept within it's heat budget, only renewable energy can be used, and there simply won't be enough of it.

[–] virgiltx 9 years ago

In regards to energy, it should be remembered that there is not a need for conversion to electricity. The evaporation and pumping can be done entirely from the heat output of some energy source, including nuclear, which hopefully can include thorium-fission and eventually fusion.

In fact, in the case of fusion, eliminating the penalty for conversion to grid-electricity moves fusion tech closer to a practical energy-gain threshold.

Supplying the coastal areas is a major and worthwhile objective.The water management problem can then shift to inland. And the inland water supply would gain all the water that was previously being sent to the coastal urban areas, like Los Angeles, which should be doable.

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[–] melinda2001 9 years ago

You don't get that the planet must keep within its heat budget or we'll cook ourselves. Fusion would be the worst possible thing in that regard. Fission can only be a stop-gap. Avoiding converting to electricity will save conversion costs, but you have to consider the opportunity cost of the electricity you could have had and ask whether it's economical to desalinate. In most cases the answer is no.

[–] virgiltx 9 years ago

I didn't know that fusion has been ruled out as future energy source because of heat budget. The ITER NIF and Lockheed Martin people don't seem to agree.

Are we cooking ourselves with manmade residual heat? Isn't it the sunlight trapped by greenhouse gases that is cooking us?

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[–] melinda2001 9 years ago

Right now it's the greenhouse effect and that alone is pretty dire. Fusion would cook us directly because 1) the efficiency would likely be very poor (close to break-even) at least initially, and 2) there's an effectively endless supply of hydrogen, so if it ever becomes practical, there will be no stopping us from using it like crazy. We're just lucky that it looks too difficult and that fossil fuel reserves are running out. We must live on renewables, so our future needs to be powered nearly 100% by solar, wind, wave, tidal, biomass, geothermal, etc. All of those can be converted into hydrogen, battery charging, and even liquid fuels including hydrocarbons, carbohydrates, alcohol, etc. so we can build an infrastructure based on one or more of those forms of energy storage so that no location needs to be dependent entirely on local energy.