Environment

Is harvesting energy from evaporating water a serious renewable energy prospect?

Is harvesting energy from evap...
Could reservoirs like this be used to generate electricity through evaporation?
Could reservoirs like this be used to generate electricity through evaporation?
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Using weather and air temperature measurements this map shows what locations in the United States could produce the most electricity from lakes and reservoirs
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Using weather and air temperature measurements this map shows what locations in the United States could produce the most electricity from lakes and reservoirs
Could reservoirs like this be used to generate electricity through evaporation?
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Could reservoirs like this be used to generate electricity through evaporation?

A recently published study estimates that up to 70 percent of the United States' electricity needs could be met through a newly devised system that harvests power from evaporation. This novel renewable power source uses bacterial spores to generate electricity and can sit on top of lakes and reservoirs.

Back in 2015, Ozgur Sahin and a team of scientists from Columbia University revealed an exciting new potential source of renewable energy. The team had created a way to generate energy from the natural process of evaporation using a certain type of bacterial spore. These spores expand and contract as they absorb evaporating moisture, and this oscillating motion could be harnessed to generate a small amount of power.

The team developed a device that held these spores and to prove the system's effectiveness created a miniature car that ran on this evaporation energy system. At the time the technology was an interesting concept but one not hugely appropriate for large-scale implementation.

Now Sahin and colleagues have posed an even more expansive thought experiment, publishing a new paper hypothesizing how much energy could be generated if such evaporation power-harvesting technology was implemented across lakes and reservoirs in the United States. The study estimates an enormous 325 gigawatts of power could be generated using the method.

"We have the technology to harness energy from wind, water and the sun, but evaporation is just as powerful," says Sahin. "We can now put a number on its potential."

This massive number, nearly 70 percent of what the US currently produces, is not exactly a realistic proposition. After all, this hypothetical level of power generation requires nearly every large body of water in the country to be covered with the energy-harvesting system. Notwithstanding the general public's loss of access to these large bodies of water for recreational activities, the effects of this kind of system on weather patterns needs to be seriously considered.

Using weather and air temperature measurements this map shows what locations in the United States could produce the most electricity from lakes and reservoirs
Using weather and air temperature measurements this map shows what locations in the United States could produce the most electricity from lakes and reservoirs

But the paper suggests such an expansive interruption to localized evaporation patterns would have negligible effects on major weather patterns, which are primarily dominated by ocean evaporation.

"Locally, feedback effects will also be small if the dimensions covered by an engine are below 500 km (311 mi)," write the authors. "This is due to the important role of horizontal heat and moisture transport in the atmosphere that couples neighboring regions."

A more practical outcome for the technology comes when the study focuses on hypothetically converting specific locations into evaporation power plants. If the 38-sq km (14.7-sq mi) surface area of the E.V. Spence Reservoir in Texas was completely covered by the system, for example, it "would generate an average annual power output of 178 MW" say the researchers.

This power output is more than 50 percent greater than a nearby wind farm.

Of course, if you've read this far you are probably wondering how much this all would cost? The study neglects to consider how much rolling out this technology on such a massive scale would cost. While the proof-of-concept paper is more interested in theoretically testing how much power could be generated, this is a reasonably irrelevant figure without a cost attached.

Other environmental implications are also neglected in the paper. Does the process affect the quality of the water, for example?

The search for new, safe, renewable forms of energy is undoubtedly important as we move away from fossil fuels, and the idea of using evaporation as an energy source is certainly an interesting one, but this study shows it is still very much in the theoretical category of renewable power sources for now.

The paper was published in the journal Nature Communications.

Source: Columbia News

8 comments
8 comments
Bernd1991
10 W/m2 is the highest amount in the figure. That is an extremely low value. Solar is about 200 W/m2. 178 megawatts for a 38-sq km lake? 38 sq km is a huge surface: 38 000 000 m2. This would be about 7600 MW if a solar PV plant was created here. Unless the price of these devices is about 50 times cheaper per m2 to produce ánd deliver than solar, than they would have a business model.
I think this won't be viable. What do you think?
Bob Stuart
This process may pull energy from the evaporation process, but evaporation itself requires solar or other energy. That's why sweat cools you off. It sounds more like the energy comes from osmotic pressure, and the delayed evaporation then handles the return stroke without direct involvement. Machines to harvest such swelling are a fascinating challenge.
habakak
We already have an affordable technology that works and can utilize bodies of water. Solar panels. Cover 10% or 30% of certain bodies of water and we make good use of space that might not be used effectively. Solar panels on top of water will help to limit evaporation (especially in hotter and dryer climes where this is more important - like on Lake Meade that is shown in this photo) and it will facilitate cooler operating temperatures for solar panels which will make it more efficient (and thus more cost-effective).
Buellrider
Just because something can be done does not mean it is a good idea. Can you imagine the problems caused by the shade on the ecosystem. Probably kill off everything beneath it. Whole flocks of birds and bats hit windmill blades but that collateral damage seems to be just fine, but if people were perishing willy nilly because of those windmills all hell would break loose. Oh the humanity! It keeps getting hotter and so we need more electricity to cool our buildings and homes. Lets not attack the problem of global climate change , lets treat the symptom, heat, with more air-conditioners. That is why the human race is doomed in the long run.
Mark Windsor
In India some large irrigation canals are being partially covered by PV panels, reducing evaporation (loss) of valuable water while generating power on otherwise unused surface areas. In the end water is more important than energy so I prefer this idea to what seems a bit "pie in the sky" especially given the lack of information required to assess it fully.
BrianK56
Buellrider, How about all the people that are hit by trains, shot, car accidents, drown in lakes just to name a few.
highlandboy
The "car" shows water added at the top. The added moisture causes the scrolled on that side to straighten, gravety causes that side of the wheel to descend. As they dry the active parts curl back up and become the assending part of the wheel. Question: what percentage of the generated power is required to raise the liquid to the top?
VTBob
I have long wanted a way to harness the solar energy that goes into the creation of hurricanes and typhoons. This looks like a start on that process. I would siphon off some of the energy only, leaving the resulting severe storm less likely to cause extensive, expensive damage. The bonus would be the captured, usable energy. This would require extensive input from multiple disciplines. However, it looks like a win - win deal, tame the most violent natural processes and supply humanity with power to use.