Cool story about California's effort to conserve water [Archive]

Chloe

08-14-2015, 01:19 PM

Plastic balls are California's water-savers

Millions of black 'shade balls' float on the surface of reservoirs, slowing evaporation.

They're hypnotic and incredibly odd. Thousands of black plastic "shade balls" were released this week into the Los Angeles Reservoir to float and bob on the surface, looking like a kind of dark playground (http://www.mnn.com/health/healthy-spaces/blogs/want-a-better-playground-get-rid-of-the-benches) ball pit.
The release of this batch of 20,000 balls into the 175-acre reservoir was the culmination of a $34.5 million initiative to protect the water supply (http://www.mnn.com/earth-matters/wilderness-resources/blogs/california-drought-is-driving-the-depletion-of) that involved the deployment of a whopping 96 million plastic balls into the water.

http://youtu.be/wzLKA-1nJO4
“In the midst of California’s historic drought, it takes bold ingenuity to maximize my goals for water conservation,” said Los Angeles Mayor Eric Garcetti, who helped release the balls. “This effort by LADWP is emblematic of the kind of the creative thinking we need to meet those challenges."
The balls are intended to prevent sunlight-triggered chemical reactions that encourage algae — creating cleaner water, says Garcetti. The bobbing balls also protect the water from wildlife. But the key benefit is that the floating ball will prevent evaporation (http://www.mnn.com/earth-matters/climate-weather/stories/global-warming-brought-on-californias-severe-drought). Los Angeles officials estimate the balls will save about 300 million gallons of water each year.
The shade balls are BPA-free and should not release any chemicals. Garcetti said the orbs, which are manufactured by minority, women-owned facilities in Los Angeles County, require no parts, labor or maintenance aside from occasional rotation. They're recyclable and should last 10 years before they need to be replaced.
Plus, they're saving the city a lot of money compared to other alternatives, which included splitting the reservoir with a bisecting dam and installing floating covers that would have cost more than $300 million. According to a Facebook post from Garcetti, “with these shade balls, we ended up spending only $0.36 for each ball coming in at just $34.5 million to get the same result."
Shade balls aren't a new concept; they've been used in open-air reservoirs in Los Angeles since 2008. They're the brainchild of Dr. Brian White, a now-retired biologist with the Los Angeles Department of Water and Power, who said he got the idea when he learned about the application of “bird balls” that were placed in ponds along airfield runways to keep birds from congregating too close to planes.
In addition to the Los Angeles Reservoir, the balls are floating at Upper Stone, Elysian and Ivanhoe reservoirs and other areas.
There's something strangely mesmerizing about the rolling, bouncing balls. Watch as Las Virgenes Municipal Water District releases new shade balls in a reservoir:
http://youtu.be/lqhF2JpZBVs

Plastic balls are California's water-savers | MNN - Mother Nature Network (http://www.mnn.com/earth-matters/wilderness-resources/stories/plastic-balls-are-californias-water-savers)

waltky

10-03-2017, 11:57 PM

Harvesting energy from evaporation...
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Energy harvested from evaporation could power much of US, says study
September 26, 2017 - In the first evaluation of evaporation as a renewable energy source, researchers at Columbia University find that U.S. lakes and reservoirs could generate 325 gigawatts of power, nearly 70 percent of what the United States currently produces.

Though still limited to experiments in the lab, evaporation-harvested power could in principle be made on demand, day or night, overcoming the intermittency problems plaguing solar and wind energy. The researchers' calculations are outlined in the Sept. issue of Nature Communications. "We have the technology to harness energy from wind, water and the sun, but evaporation is just as powerful," says the study's senior author Ozgur Sahin, a biophysicist at Columbia. "We can now put a number on its potential." Evaporation is nature's way of cycling water between land and air. Sahin has previously shown how this basic process can be exploited to do work. One machine developed in his lab, the so-called Evaporation Engine, controls humidity with a shutter that opens and closes, prompting bacterial spores to expand and contract. The spores' contractions are transferred to a generator that makes electricity. The current study was designed to test how much power this process could theoretically produce.

https://3c1703fe8d.site.internapcdn.net/newman/csz/news/800/2017/energyharves.jpg
The southern and western United States have the greatest capacity to produce evaporation-generated power from lakes and reservoirs, a new study in Nature Communications finds

One benefit of evaporation is that it can be generated only when needed. Solar and wind power, by contrast, require batteries to supply power when the sun isn't shining and wind isn't blowing. Batteries are also expensive and require toxic materials to manufacture. "Evaporation comes with a natural battery," said study lead author, Ahmet-Hamdi Cavusoglu, a graduate student at Columbia. "You can make it your main source of power and draw on solar and wind when they're available." Evaporation technology can also save water. In the study, researchers estimate that half of the water that evaporates naturally from lakes and reservoirs into the atmosphere could be saved during the energy-harvesting process. In their model, that came to 25 trillion gallons a year, or about a fifth of the water Americans consume.

States with growing populations and sunnier weather can best capitalize on evaporation's capacity to generate power and reduce water waste, in part because evaporation packs more energy in warm and dry conditions, the researchers say. Drought-prone California, Nevada and Arizona could benefit most. The researchers simplified their model in several ways to test evaporation's potential. They limited their calculations to the United States, where weather station data are readily accessible, and excluded prime locations such as farmland, rivers, the Great Lakes, and coastlines, to limit errors associated with modeling more complex interactions. They also made the assumption that technology to harvest energy from evaporation efficiently is fully developed.

https://3c1703fe8d.site.internapcdn.net/newman/csz/news/800/2017/1-energyharves.jpg
Evaporation-harvested energy can cut by half the water lost to natural evaporation, researchers say. Water-strapped cities with growing populations and energy needs could benefit most, including greater Phoenix, served by the above reservoir and irrigation system fed by the Colorado River.

Klaus Lackner, a physicist at Arizona State University who was not involved in the study, expressed support for the team's findings. Lackner is developing artificial trees that draw carbon dioxide from the air, in part, by harnessing the power of evaporation. "Evaporation has the potential to do a lot of work," he said. "It's nice to see that drying and wetting cycles can also be used to collect mechanical energy." The researchers are working to improve the energy efficiency of their spore-studded materials and hope to eventually test their concept on a lake, reservoir, or even a greenhouse, where the technology could be used to simultaneously make power and limit water loss.

https://techxplore.com/news/2017-09-energy-harvested-evaporation-power.html

See also:

Getting a charge from changes in humidity
January 27, 2014 — A new type of electrical generator uses bacterial spores to harness the untapped power of evaporating water, according to research conducted at the Wyss Institute of Biologically Inspired Engineering at Harvard University. Its developers foresee electrical generators driven by changes in humidity from sun-warmed ponds and harbors.

The prototype generators work by harnessing the movement of a sheet of rubber coated on one side with spores. The sheet bends when it dries out, much as a pine cone opens as it dries or a freshly fallen leaf curls, and then straightens when humidity rises. Such bending back and forth means that spore-coated sheets or tiny planks can act as actuators that drive movement, and that movement can be harvested to generate electricity. "If this technology is developed fully, it has a very promising endgame," said Ozgur Sahin, who led the study, first at Harvard's Rowland Institute, later at the Wyss Institute, and most recently at Columbia University, where he's now an associate professor of biological sciences and physics. Sahin collaborated with Wyss Institute Core Faculty member L. Mahadevan, who is also the Lola England de Valpine professor of applied mathematics, organismic and evolutionary biology, and physics at the School of Engineering and Applied Sciences at Harvard University, and Adam Driks, a professor of microbiology and immunology at Loyola University Chicago Stritch School of Medicine. The researchers reported their work yesterday in Nature Nanotechnology.

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As Bacilli bacteria dry out and form spores (shown here), they wrinkle, and as they rehydrate, they swell. A team lead by former Wyss Institute resident scholar Ozgar Sahin harnessed these humidity-driven changes to power an actuator and generate electricity.

Water evaporation is the largest power source in nature, Sahin said. "Sunlight hits the ocean, heats it up, and energy has to leave the ocean through evaporation," he explained. "If you think about all the ice on top of Mt. Everest – who took this huge amount of material up there? There's energy in evaporation, but it's so subtle we don't see it." But until now no one has tapped that energy to generate electricity. As Sahin pursued the idea of a new humidity-driven generator, he realized that Mahadevan had been investigating similar problems from a physical perspective. Specifically, he had characterized how moisture deforms materials, including biological materials such as pine cones, leaves and flowers, as well as man-made materials such as a sheet of tissue paper lying in a dish of water.

Sahin collaborated with Mahadevan and Driks on one of those studies. A soil bacterium called Bacillus subtilis wrinkles as it dries out like a grape becoming a raisin, forming a tough, dormant spore. The results, which they reported in 2012 in the Journal of the Royal Society Interface, explained why. Unlike raisins, which cannot re-form into grapes, spores can take on water and almost immediately restore themselves to their original shape. Sahin realized that since they shrink reversibly, they had to be storing energy. In fact, spores would be particularly good at storing energy because they are rigid, yet still expand and contract a great deal, the researchers predicted. "Since changing moisture levels deform these spores, it followed that devices containing these materials should be able to move in response to changing humidity levels," Mahadevan said. "Now Ozgur has shown very nicely how this could be used practically."

https://3c1703fe8d.site.internapcdn.net/newman/csz/news/800/2014/1-gettingachar.jpg
In this device, the humidity-driven flexing of a spore-covered piece of latex rubber (right) drives the movement of a magnet, which produces electricity. A device built on similar principles could function as a humidity-driven electrical generator.

When Sahin first set out to measure the energy of spores, he was taken by surprise. He put a solution thick with spores on a tiny, flexible silicon plank, expecting to measure the humidity-driven force in a customized atomic force microscope. But before he could insert the plank, he saw it curving and straightening with his naked eye. His inhaling and exhaling had changed the humidity subtly, and the spores had responded. "I realized then that this was extremely powerful," Sahin said. In fact, simply increasing the humidity from that of a dry, sunny day to a humid, misty one enabled the flexible, spore-coated plank to generate 1000 times as much force as human muscle, and at least 10 times as much as other materials engineers currently use to build actuators, Sahin discovered. In fact, moistening a pound of dry spores would generate enough force to lift a car one meter off the ground. To build such an actuator, Sahin tested how well spore-coated materials such as silicon, rubber, plastic, and adhesive tape stored energy, settling on rubber as the most promising material.

Then he built a simple humidity-driven generator out of LegosTM, a miniature fan, a magnet and a spore-coated cantilever. As the cantilever flips back and forth in response to moisture, it drives a rotating magnet that produces electricity. Sahin's prototype captures just a small percentage of the energy released by evaporation, but it could be improved by genetically engineering the spores to be stiffer and more elastic. Indeed, in early experiments, spores of a mutant strain provided by Driks stored twice as much energy as normal strains. "Solar and wind energy fluctuate dramatically when the sun doesn't shine or the wind doesn't blow, and we have no good way of storing enough of it to supply the grid for long," said Wyss Institute Founding Director Don Ingber, M.D., Ph.D. "If changes in humidity could be harnessed to generate electricity night and day using a scaled up version of this new generator, it could provide the world with a desperately needed new source of renewable energy."

For more on the potential of this spore-containing actuator and generator, see this short animation: (https://phys.org/news/2014-01-humidity.html)