OFF-GRID POWER PLANTS

WETLANDS POWERED
http://inhabitat.com/now-plants-can-generate-sustainable-energy-while-they-grow/
Electricity-Generating Plants to Bring Clean Energy to Off-Grid Locations
by Julie M. Rodriguez / 03/19/14

Dutch start-up called Plant-e has developed a way to use living plants as a continuous source of clean energy – all that’s needed is a light source, carbon dioxide, water, and, of course, a field or patch of plants. The system works best in wetlands or watery fields like rice paddies, but it doesn’t matter if the water is brackish or polluted, so areas unsuitable for growing crops could be repurposed as a power source. There’s no complicated infrastructure to install, which makes it super easy to bring electricity to isolated regions that are currently without power.

The theory behind the Plant-e system is surprisingly simple. When plants create food using photosynthesis, a large portion of the organic matter generated is actually excreted by the roots into the soil. That organic matter gets munched on by microorganisms living in the soil, which release electrons as a byproduct of this consumption. By placing an electrode near the roots, it’s easy to harvest this waste energy and turn it into electricity. The process is similar to elementary school science projects that create a battery out of an apple or potato, but with the added benefit of leaving the plants completely unharmed by the process. Tests have shown that the plants will continue to grow normally in the presence of electrodes, providing a constant source of power day and night. A prototype green roof using this technology is already being tested in the Netherlands. Currently, the Plant-e team is able to generate enough energy to power a cell phone, but the hope is that soon this method will be able to harvest a significant amount of electricity — maybe even enough to power a house.

ALGAE POWERED
http://news.stanford.edu/news/2010/april/electric-current-plants-041310.html
http://inhabitat.com/stanford-scientists-harvest-electricity-from-algae-photosynthesis/
http://www.engadget.com/2010/04/15/stanford-researchers-harvest-electricity-from-algae-unkempt-poo/
Stanford researchers harvest electricity from algae, unkempt pools become gold mines
by Joseph L. Flatley  / April 15 2010

While we’ve seen plenty of stabs at viable green energy, from underwater turbines to the Bloom Box, we’re always up for another. Running along the same lines as Uppsala University’s algae-based batteries, researchers at Stanford are generating electrical current by tapping into the electron activity of individual algae cells. The team designed a gold electrode that can be pushed through a cell membrane, which then seals around it. The cell, still alive, does what it does best (photosynthesis), at which point scientists harvest chemical energy in the form of electrons. According to Stanford University News, this results in “electricity production that doesn’t release carbon into the atmosphere. The only byproducts of photosynthesis are protons and oxygen.”

JUST ADD ELECTRODES
http://www.scientificamerican.com/article/bionic-plants-offer-superpowered-photosynthesis/
http://phys.org/news/2013-05-power-explore-harvest-electricity.html
http://inhabitat.com/scientists-discover-methods-of-harvesting-electricity-from-plants/
Scientists Discover Methods of Harvesting Electricity from Plants
by , 05/09/13

When it comes to capturing solar energy, plants are first in their class. Able to function at nearly 100 percent quantum efficiency, they can produce an equal number of electrons for each photon captured. Using these photons to split water into hydrogen and oxygen, the resulting electrons are able to create sugars that help the plant to live and reproduce. Researchers at the University of Georgia have developed a way to harness the power of the photosynthetic process to generate a clean form of electricity. Ramaraja Ramasamy, assistant professor in the UGA College of Engineering, explained how his team manipulated the biology for human advantage. During photosynthesis, electrons freed from water molecules go towards producing sugars for the plant’s survival. Structures within the plant cell called “thylakoids” store the energy from the sun. The scientists were able to alter proteins within the thylakoids to interrupt the pathway along which electrons flow, placing the thylakoids against a backing of carbon nanotubules 50,000 times finer than a human hair. Acting as an electrical conductor, the nanotubules were able to take the electrons from the plant and move them along a wire. During experiments, the process resulted in current levels that were twice the power of current systems. While more work needs to be done to bring the technology to market level, the developments could potentially improve the function of solar panels, remote sensors, and other electronic equipment. “Clean energy is the need of the century,” said Ramasamy. “This approach may one day transform our ability to generate cleaner power from sunlight using plant-based systems.” Instead of noisy generators, turbines, or coal-fire stations, it is possible that we may one day have real “power plants” in our neighborhoods.

TOMATO POWERED
http://inhabitat.com/table-lamp-powered-completely-by-tomatoes/
Table Lamp Powered Completely by Tomatoes
by  / 04/15/10

We all know tomatoes pack a powerful acidic punch, but we never thought we’d see one lighting up a room! Cygalle Shapiro of Israel-based d-VISION has created an incredible LED lamp that is completely powered by real, edible tomatoes. Currently exhibited at the Milan Furniture Fair, the design collects energy from a chemical reaction between tomato acids, zinc, and copper. This design doesn’t only explore advances in lighting technology – its also an art piece that sends clear and powerful social-conscience messages about where and how we receive energy.

d-VISION‘s tomato lamp calls attention to the amount of natural resources needed to produce even the smallest amount of power for everyday living. Although the tomato lamp utilizes an organic energy source, it still takes a considerately large amount of tomatoes just to power one lamp. The lamp holds power until the tomatoes go stale, signaling a beginning and end to energy sources. The designer highlights value by creating the tomato-powered circuits and lamp completely out of gold.

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OCEAN POWER

A Navy fuel ship replenishes the the U.S.S. Mount Whitney on the Mediterranean Sea in October 2013. (U.S. Navy photo by Mass Communication Specialist 1st Class Collin Turner/Released)
A Navy fuel ship replenishes the the U.S.S. Mount Whitney (right) on the Mediterranean Sea in October 2013

SEAWATER
http://gizmodo.com/pouring-saltwater-over-graphene-generates-electricity-1563379860
https://blogs.discovermagazine.com/d-brief/2014/04/08/u-s-navy-can-convert-seawater-fuel/
U.S. Navy Wants to Fuel Ships Using Seawater
by Carl Engelking  / April 8, 2014

The U.S. Navy’s Arleigh Burke-class destroyer typically burns 1,000 gallons of petroleum fuel an hour. Most of the Navy’s fleet shares the same ravenous appetite for fuel, and refueling these massive warships can interrupt missions and present challenges in rough weather. However, researchers at the U.S. Naval Research Laboratory have now proven that it’s possible to power engines instead with a cheap, convenient supply of fuel: seawater. Scientists have spent nearly a decade laboring to turn the ocean into fuel. The breakthrough, demonstrated in a proof-of-concept test, was made possible by a specialized catalytic converter that transforms carbon dioxide and hydrogen from seawater into a liquid hydrocarbon fuel.



The development of a liquid hydrocarbon fuel is being hailed as a game changer. If Navy ships create their own fuel they can remain operational 100 percent of the time, rather than conducting frequent fuel-ups with tankers while at sea, which can be tricky in rough weather. A catalytic converter extracts carbon dioxide and hydrogen from water and converts the gases into liquid hydrocarbons at a 92 percent efficiency rate, and the resulting fuel can be used in ships’ existing engines. The feasibility of the approach was demonstrated in the test on April 2, when researchers flew a model airplane using the fuel from seawater. “This is the first time technology of this nature has been demonstrated with the potential for transition, from the laboratory, to full-scale commercial implementation,” said Navy research chemist Heather Willauer in a news release Monday. The next major step is to build the infrastructure to convert seawater into fuel on a massive scale. The Navy would first start mass-producing fuel in land-based operations, which would be the first step toward installing fuel generation systems on ships. The Navy predicts the seawater fuel would cost about $3-6 per gallon, and could be commercially viable within a decade.

GAS-to-LIQUID (GTL)
http://www.navy.mil/viewVideo.asp?id=19336
http://www.navy.mil/submit/display.asp?story_id=80171

“Navy researchers at the U.S. Naval Research Laboratory (NRL), Materials Science and Technology Division, demonstrated proof-of-concept of novel NRL technologies developed for the recovery of carbon dioxide (CO2) and hydrogen (H2) from seawater and conversion to a liquid hydrocarbon fuel. Fueled by a liquid hydrocarbon – a component of NRL’s novel gas-to-liquid (GTL) process that uses CO2 and H2 as feedstock – the research team demonstrated sustained flight of a radio-controlled (RC) P-51 replica of the legendary Red Tail Squadron, powered by an off-the-shelf (OTS) and unmodified two-stroke internal combustion engine. Using an innovative and proprietary NRL electrolytic cation exchange module (E-CEM), both dissolved and bound CO2 are removed from seawater at 92 percent efficiency by re-equilibrating carbonate and bicarbonate to CO2 and simultaneously producing H2. The gases are then converted to liquid hydrocarbons by a metal catalyst in a reactor system. “In close collaboration with the Office of Naval Research P38 Naval Reserve program, NRL has developed a game-changing technology for extracting, simultaneously, CO2 and H2 from seawater,” said Dr. Heather Willauer, NRL research chemist. “This is the first time technology of this nature has been demonstrated with the potential for transition, from the laboratory, to full-scale commercial implementation.”

CO2 in the air and in seawater is an abundant carbon resource, but the concentration in the ocean (100 milligrams per liter [mg/L]) is about 140 times greater than that in air, and 1/3 the concentration of CO2 from a stack gas (296 mg/L). Two to three percent of the CO2 in seawater is dissolved CO2 gas in the form of carbonic acid, one percent is carbonate, and the remaining 96 to 97 percent is bound in bicarbonate. NRL has made significant advances in the development of a gas-to-liquids (GTL) synthesis process to convert CO2 and H2 from seawater to a fuel-like fraction of C9-C16 molecules. In the first patented step, an iron-based catalyst has been developed that can achieve CO2 conversion levels up to 60 percent and decrease unwanted methane production in favor of longer-chain unsaturated hydrocarbons (olefins). These value-added hydrocarbons from this process serve as building blocks for the production of industrial chemicals and designer fuels. In the second step these olefins can be converted to compounds of a higher molecular using controlled polymerization. The resulting liquid contains hydrocarbon molecules in the carbon range, C9-C16, suitable for use a possible renewable replacement for petroleum based jet fuel.

The predicted cost of jet fuel using these technologies is in the range of $3-$6 per gallon, and with sufficient funding and partnerships, this approach could be commercially viable within the next seven to ten years. Pursuing remote land-based options would be the first step towards a future sea-based solution. The minimum modular carbon capture and fuel synthesis unit is envisioned to be scaled-up by the addition individual E-CEM modules and reactor tubes to meet fuel demands. NRL operates a lab-scale fixed-bed catalytic reactor system and the outputs of this prototype unit have confirmed the presence of the required C9-C16 molecules in the liquid. This lab-scale system is the first step towards transitioning the NRL technology into commercial modular reactor units that may be scaled-up by increasing the length and number of reactors. The process efficiencies and the capability to simultaneously produce large quantities of H2, and process the seawater without the need for additional chemicals or pollutants, has made these technologies far superior to previously developed and tested membrane and ion exchange technologies for recovery of CO2 from seawater or air.”

artist's conception of a pilot plant off China's coast

TEMPERATURE DIFFERENTIALS
http://lockheedmartin.com/us/products/wave-tidal-energy.html
http://www.lockheedmartin.com/us/news/press-releases/2014/february/140211-mst-worlds-largest-wave-energy-project.html
http://www.scientificamerican.com/article/ocean-thermal-power-will-debut-off-chinas-coast/
Ocean Thermal Power Will Debut off China’s Coast
by Daniel Cusick and ClimateWire / May 1, 2013

Forty years of research and development by Lockheed Martin into harnessing energy from steep differentials in ocean temperatures will see its first commercial deployment in China. There, a resort developer has partnered with the U.S. defense and aerospace giant to build a 10-megawatt power plant using ocean thermal energy conversion (OTEC) technology. A recently signed agreement between Lockheed Martin, of Bethesda, Md., and the Beijing-based Reignwood Group should lead to the completion of the alternative energy plant by 2017 in waters off southern China’s Hainan Island. The platform-based power plant will be the largest OTEC application developed to date, according to Lockheed, supplying 100 percent of the power needed for the resort, which will be marketed as a low-carbon real estate development.

The technology involves heating warm surface water to produce steam that drives a turbine generator. Then colder water is pumped from 800 to 1,000 meters below the ocean surface to condense the steam back into liquid form. Dan Heller, Lockheed Martin’s vice president of new ventures for Mission Systems and Training, said the relationship with Reignwood, a diversified firm with holdings in the energy, minerals, aviation and resort business, solidified as Lockheed engineers went searching for suitable locations to build a pilot-scale OTEC facility. For several years, Lockheed has tested the technology at a site in Hawaii in partnership with Makai Ocean Engineering, the Energy Department and the U.S. Navy. But several obstacles, including high upfront costs and securing a partner for a long-term project, kept such efforts from growing into a scaled power plant, according to sources familiar with the testing program.

Duke Hartman, a spokesman for Makai Ocean Engineering, said that his firm continues to work on OTEC applications in partnership with the Navy, and that the Pentagon has retained its goal of developing a 5-10 MW pilot plant off the island of Oahu and eventually a commercial plant of up to 100 MW. “The Navy wants a thriving OTEC industry because they would benefit from it,” Hartman said. Imagine being able to tow a semisubmersible power plant to almost any corner of the world, he added. Hartman said Makai is supportive of Lockheed Martin’s work in China and hopes to be able to participate in the project in some way. “The biggest obstacle to OTEC is economies of scale,” he said. “You get a lot more bang for your buck if you go bigger.” He estimated that a 100 MW OTEC plant would cost in excess of $1 billion to build using current technologies, and that the cost would not be significantly lower for a scaled-down plant. Lockheed Martin’s Heller said that Reignwood will bear the full cost of the 10 MW project in south China and that the two firms will continue to seek opportunities to expand OTEC’s foothold in Asia.

U.S. sites with potential
In the United States, Heller noted that several sites, including Hawaii and Florida, have demonstrated potential for commercial OTEC plants, and that Lockheed continues to work to identify partners for OTEC projects at home. But, he said, when the company began surveying locations for a commercial plant, “China was a very logical place to start” due to its need for clean energy alternatives as well as its location near some of the world’s most ideal oceanographic conditions. Reignwood, he said, was recommended as a development partner because of its commitment to use clean energy to power its resort communities. Heller said Lockheed Martin will use the Reignwood project to help prove OTEC’s viability as an energy resource with the long-term goal of “building an industry around OTEC,” which has applications beyond electricity generation such as seawater desalination and hydrogen production. And unlike other renewable energy sources, OTEC can be relied on for 24-hour, base-load power. Lockheed has a team of about 20 engineers working on its OTEC program, and that number is likely to go up as the Reignwood project moves closer to the construction phase. “Even before the announcement, we’ve had a tremendous response when it became evident that we were going to make this a reality,” Heller said.

A prototype osmotic power plant in Tofte, Norway.
The world’s first osmotic energy plant has been operating for more than three years in Tofte, Norway, on the Oslofjord inlet. Statkraft is seeking to ramp up its efforts to produce renewable energy from the physical interaction of saltwater and freshwater.

SALT
https://en.wikipedia.org/wiki/Osmotic_power
http://www.wfs.org/futurist/2013-issues-futurist/july-august-2013-vol-47-no-4/harnessing-power-osmosis
http://www.wfs.org/futurist/2013-issues-futurist/july-august-2013-vol-47-no-4/harnessing-power-osmosis
http://sciencenordic.com/creating-next-generation-power-stations
http://news.nationalgeographic.com/news/energy/2013/01/130107-osmotic-energy-norway/
Salt Power: Norway Project Tries Osmotic Energy
by Dean Clark  /  January 7, 2013

Tofte, an hour south of Oslo on the inlet known as Oslofjord, is home to a waterfront cellulose factory and not much else. But for more than three years, Norwegian energy company Statkraft has been rather quietly testing the technology in the world’s first osmotic power plant, in a renovated wing of the town’s factory. With a meager two to four kilowatts of capacity, barely enough power to foam a cappuccino, the plant is a decidedly small start. But the Norwegian Center for Renewable Energy (SFFE) pegs the global potential of osmotic power to be about 1,370 terawatt-hours per year, about equivalent to the current electricity consumption of Eastern Europe and Russia combined. So Statkraft is now seeking to ramp up its work, while researchers around the world are joining in the effort to harness a new form of renewable energy from the saltwater that covers more than 70 percent of the Earth’s surface.

Power from Movement
Osmotic power, also known as “salinity gradient” power, relies on a rather basic physical process: diffusion. Salty water molecules tend to move into freshwater nearby. It happens wherever rivers meet the sea, creating energy in the form of heat.  Place a semipermeable barrier between the saltwafter and the freshwater, and the diffusion of molecules through the membrane is osmosis. For decades, reverse osmosis has been used to filter water. Sidney Loeb, the American chemical engineer who is credited with developing a practical reverse osmosis process in the 1950s, later developed a technique for capturing the energy in the rush of saltwater to the freshwater side of a membrane. Statkraft estimates it spent over ten years and more than 100 million kroner (about $12 million USD) in research funds to help develop one of these techniques, pressure retarded osmosis (PRO), in the prototype facility at Tofte. It’s a big investment for a facility that has only enough capacity to operate a coffee machine, but size of output isn’t the key metric for researchers at this point. Statkraft views the Tofte experiment as a lab for learning how to capitalize on osmotic power´s huge potential and strong environmental credentials. Independent experts see the potential. “It´s a very clean process,” said Friso Sikkema, senior specialist in power generation and renewables at DNV Kema, a leading research firm in the field based in the Netherlands.

Osmotic power generation is carbon-free, and Statkraft reports that its plant´s main byproduct is brackish water. Questions remain however, concerning future large-scale operations and their effect on salinity levels or how pretreatment processes might impact local marine life. Bruce Logan, director of the Hydrogen Energy Center and Engineering Energy and Environmental Institute at Penn State University says he is “optimistic osmotic power can play an important role,” but cautioned “there´s not enough work going on in terms of developing inexpensive membranes tailored for the process.” Even though membrane technology is still in its early stages, the force currently generated by the experimental process can be significant. With pressures at the Norwegian test site reaching 12 bar on the seawater side, “it’s like creating an artificial waterfall of 120 meters” (394 feet), according to Statkraft’s head of osmotic power, Stein Erik Skilhagen. In this early-stage experiment, though, the flow of water is more a trickle than a cascade, so power output at Tofte is still small.

Interest in the renewable energy source is growing internationally. NASA has been working on osmotic systems for the treatment of wastewater aboard spacecraft, and is now investigating the PRO method with tertiary treatment, or PRO/TT, with the aim of developing technology that can purify water and create energy at the same time. Hydro-Québec, the largest electricity generator in Canada and the largest producer of hydroelectric power in the world, is partnering with Statkraft on next-stage development of PRO technology. It is looking into the feasibility of osmotic energy along Canada’s long coastline. Japan’s Tokyo Institute of Technology opened its Osmotic Power Research Centre in 2010, the year before a devastating earthquake and tsunami crippled the Fukushima Daiichi nuclear plant and led to a rethinking of the nation’s energy future. Akihiko Tanioka, the researcher leading the osmotic effort, argues that the flow volume of Japan’s rivers contain the potential energy capacity to replace five or six nuclear reactors if osmotic plants were situated where rivers run into the sea.

Natural Battery
Researchers in the Netherlands are working on an alternative to PRO—reverse electrodialysis, or RED. DNV Kema´s Sikkema said the process, essentially, is “creating a natural battery.” In the RED approach, the osmotic energy of mixing fresh and salt water is captured by directing the solution through an alternating series of positively and negatively charged exchange membranes. The resulting chemical potential difference creates a voltage over each membrane and leads to the production of direct electric energy. While less developed than PRO, the RED process may eventually become popular for a lower initial cost structure. “PRO calls for complex machinery, chambers and turbines and generators.  Economy of scale plays a large role.  In our (RED) technology, we produce electricity directly from difference in fresh and saltwater,” said Sikkema.

With all the upsides, why isn’t osmotic power already warming homes around the world? Infrastructure for the process is currently very expensive. Statkraft estimates that a PRO plant that can supply power for 30,000 homes would need to be the size of a sports stadium and require 5 million square meters of membrane. Add to that the challenge of creating intake water clean enough to keep from fouling the membranes, and there are some costly hurdles to overcome. But proponents like Skilhagen point out that the development of osmotic power will follow a curve like that of other green energy sources. “You have to compare it with other renewables: wind, hydro and solar, for example. There is a high level of investment in the beginning, but the technology will mature and become more attractive in future. Osmotic’s environmental benefits will make it a useful part of the future low-carbon energy mix if costs can be brought in line with other renewables.” Penn State’s Logan says development of inexpensive membrane technology will be key to establishing a realistic price point for osmotic energy. The next step for Statkraft is to ramp up from the prototype at Tofte to a larger pilot plant that will generate more energy and be connected to the grid. The company has applied for permits to construct a pilot on the west coast of Norway.

MICROORGANISMS
http://www.nrl.navy.mil/techtransfer/available-technologies/energy/benthic-fuel-cell
https://www.nrl.navy.mil/media/news-releases/2013/NRL-researcher-discusses-benthic-fuel-cells-electricity-from-wastewater-and-fuel-from-CO2
Continuous Sustainable Power Supply: Benthic Microbial Fuel Cell

Research chemist and branch head at the Center for Bio/Molecular Science and Engineering at the U.S. Naval Research Laboratory (NRL), Dr. Lenny Tender, speaks with Department of Defense Armed with Science on cutting-edge research to address the growing concerns of carbon-based energy consumption and the reduction in carbon dioxide (CO2) emissions. Co-inventor of the microbial fuel cell (MFC), which persistently generates electrical power in marine environments, Tender is an internationally recognized leader in MFC research that spans implications in alternative, carbon-neutral energy generation that address pressing needs of the Navy, Department of Defense (DoD), and the nation.

To get long-term data on the state of the oceans is very difficult because oceanographic sensors are constantly running out of battery power. What the benthic fuel cell does is generate electricity indefinitely using microorganisms naturally residing on the sea floor. “At the bottom of the marine environment we have sediment, the mud at the bottom of a harbor, river, lake, or the ocean, which has quite a bit of fuel in it, organic matter which microbes draw upon to satisfy their energy needs,” Tender says. “You can think of anything that has ever lived in the marine environment, phytoplankton, sea creatures, etc. When they die, they settle on the sea floor and, like leaves on the lawn, start decomposing—and this represents a pretty potent fuel source for marine microorganisms to produce energy in the form of electricity.”



There are thousands of oceanographic instruments that are deployed every year by the Navy. Naval fleets around the world, science organizations, and academic researchers studying climate get a relatively short picture of what is occurring over time. This is due to the limited lifetime of batteries typically used to power oceanographic instruments. In comparison, the benthic MFC can operate indefinitely, owing to the immense reservoir of fuel and oxidants that it draws upon in the marine environment. Tender’s research in benthic MFC development, therefore, has significant implications to future Navy capabilities with respect to persistent in-water Intelligence, Surveillance, and Reconnaissance (ISR) operations for warfighters in riverine, estuarine, and close-in littoral environments.

With funding from the Bill and Melinda Gates Foundation, Tender has expanded his MFC research to include wastewater treatment. Whereas conventional treatment processes consume significant power—an issue that confronts the DoD and developing countries alike—MFCs may enable power generation from wastewater treatment. As Tender describes, approximately five percent of U.S. electricity consumption goes to treating wastewater. The inherent energy represented by the organic matter, which is the fuel in the wastewater, can instead be used to generate electricity. Expanding on this idea, Tender says, this provides an opportunity to flip that equation upside down and to actually think of wastewater treatment plants as power stations. “The funding we have with the Gates Foundation is to help Third World communities. In other areas of the world, most don’t treat wastewater, so people can get very sick. If we can come in and say ‘well, not only can we treat the wastewater, but knock down the prevalence of disease and provide you with electricity,’ that’s the interest of the Gates Foundation that holds a similar interest to that of the DoD.” Tender describes other applications stemming from this research that he says will go way beyond just generating energy on the sea floor. “One of the things my team and I are pursuing now, that I’m very excited about, is the idea of using microorganisms as catalysts on electrodes to generate fuel from carbon dioxide,” Tender said. “This is an opportunity to start drawing on the carbon dioxide that’s already in the atmosphere and generating a fuel, basically running the combustion process in reverse.”

In the case of his microbial fuel cell, microbes oxidize organic matter residing in marine sediment or wastewater and transfer the acquired electrons to the anode. This results in the generation of electrical power, but also carbon dioxide. By running the process in reverse, it is possible to use microbes to reduce carbon dioxide back into forms of organic matter that can serve as transportation fuels, using electrons donated from cathodes and solar-generated electricity. However, the trick, says Tender, is finding candidate microbes that are very good at accepting electrons from cathodes and reducing carbon dioxide—components that he says his team has already identified. For Tender, the benthic microbial fuel cell has opened up an entire line of research that he believes will have a much higher impact than powering oceanographic sensors on the sea floor.

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FOG HARVESTING

FRESH WATER OUT of THIN AIR
http://web.mit.edu/newsoffice/2006/beetles-0614.html
http://web.mit.edu/newsoffice/2011/fog-harvesting-0421.html
http://web.mit.edu/newsoffice/2013/how-to-get-fresh-water-out-of-thin-air-0830.html
Fog-harvesting system developed by MIT and Chilean researchers could provide potable water for the world’s driest regions
by David L. Chandler  /  August 30, 2013

In some of this planet’s driest regions, where rainfall is rare or even nonexistent, a few specialized plants and insects have devised ingenious strategies to provide themselves with the water necessary for life: They pull it right out of the air, from fog that drifts in from warm oceans nearby. Now researchers at MIT, working in collaboration with colleagues in Chile, are seeking to mimic that trick on a much larger scale, potentially supplying significant quantities of clean, potable water in places where there are few alternatives. Fog harvesting, as the technique is known, is not a new idea: Systems to make use of this airborne potable water already exist in at least 17 nations. But the new research shows that their efficiency in a mild fog condition can be improved by at least fivefold, making them far more feasible and practical than existing versions. The new findings have just been published online by the journal Langmuir, a publication of the American Chemical Society, in a paper by MIT postdoc Kyoo-Chul Park PhD ’13, MIT alumnus Shreerang Chhatre PhD ’13, graduate student Siddarth Srinivasan, chemical engineering professor Robert Cohen, and mechanical engineering professor Gareth McKinley.

Fog-harvesting systems generally consist of a vertical mesh, sort of like an oversized tennis net. Key to efficient harvesting of the tiny airborne droplets of fog are three basic parameters, the researchers found: the size of the filaments in those nets, the size of the holes between those filaments, and the coating applied to the filaments. Most existing systems turn out to be far from optimal, Park says. Made of woven polyolefin mesh — a kind of plastic that is easily available and inexpensive — they tend to have filaments and holes that are much too large. As a result, they may extract only about 2 percent of the water available in a mild fog condition, whereas the new research shows that a finer mesh could extract 10 percent or more, Park says. Multiple nets deployed one behind another could then extract even more, if so desired. While some of the organisms that harvest fog do so using solid surfaces — such as the carapace of the Namib beetle, native to the Namib desert of southern Africa — permeable mesh structures are much more effective because the wind-blown fog droplets tend to be deflected around solid surfaces, Park says. Thus, a woven mesh structure resembling a window screen turns out to be most effective. With the right chemical coating, fog droplets that form on the screen then slide down to be collected at the bottom and are funneled into buckets or tanks.


A comparison of the current standard fog-harvesting mesh material (top) and the new version designed by the MIT team (bottom), under identical conditions, demonstrates how much more rapidly water accumulates from the improved version.

The researchers found that controlling the size and structure of the mesh and the physical and chemical composition of this coating was essential to increasing the fog-collecting efficiency. Detailed calculations and laboratory tests indicate that the best performance comes from a mesh made of stainless-steel filaments about three or four times the thickness of a human hair, and with a spacing of about twice that between fibers. In addition, the mesh is dip-coated, using a solution that decreases a characteristic called contact-angle hysteresis. This allows small droplets to more easily slide down into the collecting gutter as soon as they form, before the wind blows them off the surface and back into the fog stream. While the systems currently deployed in the coastal mountains at the edge of the Atacama Desert tend to yield a few liters of drinking water per day for each square meter of mesh, the theoretical calculations show that newly designed systems operating in the strong winds and dense fogs that form along the Chilean coast at certain times of the year could yield up to 12 liters per day or more, the researchers say. In collaboration with researchers at the Pontifical Catholic University in Santiago, Chile, the MIT researchers have recently installed a variety of test screens made of different materials on hilltops in a semi-arid region north of Santiago, an area that sees very little rainfall, but which is regularly enshrouded in a strong windblown coastal fog calledcamanchaca rolling in from the Pacific Ocean. The team is currently carrying out a yearlong test to study the durability and water yield of different configurations. Maria Tou ’14, an MIT undergraduate, worked with the team in Chile, helping to install instrumentation that can observe the fluid mechanics associated with the fog droplets as they collect, grow and coalesce on the meshes.

Large mesh structures, of hundreds of square meters each, could be set up relatively inexpensively; once in place, they cost virtually nothing to operate. They consume no energy, needing only an occasional brushing to remove particles of grit and bugs. “The operating cost is essentially zero,” McKinley says, because “nature has already done the hard work of evaporating the water, desalinating it and condensing the droplets. We just have to collect it.” Chilean investigators have estimated that if just 4 percent of the water contained in the fog could be captured, that would be sufficient to meet all of the water needs of that nation’s four northernmost regions, encompassing the entire Atacama Desert area. And with the MIT-designed system, Park points out, 10 percent of the fog moisture in the air passing through the new fog collector system can potentially be captured. Daniel Beysens, director of the Physics and Mechanics of Heterogeneous Media Laboratory at EPSCI in Paris, who was not involved in this research, says, “This is a very important paper for anybody who wants to get water from fog. The authors have performed a thorough theoretical and experimental investigation of the influence on the final water yield of the structure of a fog net. … Their study is a breakthrough in the design of fog collectors.”

MEANWHILE
http://www.treehugger.com/sustainable-product-design/billboard-transforms-air-into-clean-water-peru-utec.html
Billboard transforms air into clean water in Peru
by Kimberley Mok  /  February 27, 2013

At the intersection of research, education, water conservation and advertising comes this interesting project in Lima, Peru: it’s a billboard that converts the region’s moist air into drinking water. As a collaboration between Lima’s University of Engineering and Technology (UTEC) and the ad agency Mayo DraftFCB to encourage new student applications, the billboard has already produced 9450 litres of clean water for local communities in the last three months. The project takes advantage of the fact that it rarely rains in Lima (it lies in a coastal desert region), yet the atmospheric humidity is also around 98 percent. The moist air is processed through a series of reverse osmosis machines installed inside the billboard, an air filter, condenser and carbon filter, generating 96 litres (25 gallons) of water per day, which is kept in tanks at the top and comes out of a faucet located at the bottom of the billboard. It’s a smart way to show off the school’s engineering program, yet also gives back to communities that are sorely in need of clean water — and gives billboards a more worthier role other than an advertising tool. More over at UTEC and PSFK.

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