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Simple, solar-powered water desalination

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Re: Simple, solar-powered water desalination

#21
post #7

A big question is what do they do with the salt?

Kinda explained in the 9th graf:

> Unlike some desalination systems, there is no accumulation of salt or concentrated brines to be disposed of. In a free-floating configuration, any salt that accumulates during the day would simply be carried back out at night through the wicking material and back into the seawater, according to the researchers.

Re: Simple, solar-powered water desalination

#24
>> 1.5 gallons of fresh drinking water per hour for every square meter of solar collecting area.

So a football field could collect around 8,000 gallons of water per hour. Let's say you can get 5 hours of good sunlight per day = 40,000 gallons of water.

>> The team’s demonstration device can achieve an overall efficiency of 385 percent in converting the energy of sunlight into the energy of water evaporation.

>> Theoretically, with more desalination stages and further optimization, such systems could reach overall efficiency levels as high as 700 or 800 percent

So now we're looking at 80,000 gallons of water per day.

>> Unlike some desalination systems, there is no accumulation of salt or concentrated brines to be disposed of. In a free-floating configuration, any salt that accumulates during the day would simply be carried back out at night through the wicking material and back into the seawater.

>> In production, they think a system built to serve the needs of a family might be built for around $100.

Re: Simple, solar-powered water desalination

#26
Efficiency in desalination is measured by comparing the energy expenditure to the enthalpy of vaporization of water (basically the energy required to distill water by boiling it). The current state of the art reverse osmosis desalination plants use about 3.2 KWh of electricity per cubic meter of fresh water (https://pdfs.semanticscholar.org/d4d7/821d585699719289dddd10...). This technology uses about 173 KWh of solar energy per cubic meter of fresh water. The advantage of this method is lower capital costs and not having to convert solar energy to electricity. For large-scale desalination, however, it is almost certainly more cost-effective to use solar panels, batteries, and large scale reverse osmosis systems. This is still a useful project for making drinking water in remote locations, though.

Re: Simple, solar-powered water desalination

#27
post #20

> the team’s demonstration device can achieve an overall efficiency of 385 percent in converting the energy of sunlight into the energy of water evaporation. I need an explanation with pictures for that, because it seems like the author is using ‘efficiency’ incorrectly.

It takes 1 watt-hour to produce about 3.5 BTUs. With a heat pump, for instance, you might be able to produce 5BTUs per watt-hour, because you're extracting heat from the environment (a very large heat source), which would be 140% efficient. The paragraph you excerpted has your answer: > The key to the system’s efficiency lies in the way it uses each of the multiple stages to desalinate the water. At each stage, heat…

You mean BTU/hour.

Re: Simple, solar-powered water desalination

#28
post #9

"than 1.5 gallons of fresh drinking water per hour for every square meter of solar collecting area." Units, people. Units. Be imperial. Be metric. Hey! Be both!

It comes out to about 0.4 liters per square foot, for those of you who are confused.

What's that in bathtubs per football field?

Re: Simple, solar-powered water desalination

#30
post #9

"than 1.5 gallons of fresh drinking water per hour for every square meter of solar collecting area." Units, people. Units. Be imperial. Be metric. Hey! Be both!

It comes out to about 0.4 liters per square foot, for those of you who are confused.

That means for every square rod of surface area, this unit produces over 11,000 hogsheads of water! Impressive.
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