KAUST: A greener approach to a green solution

An environment-friendly method for synthesizing a microporous material that can adsorb carbon dioxide emitted from fossil fuel-driven power plants has been developed by researchers at KAUST¹.

Burning carbon-based energy sources to meet the world’s energy demands is recognized to have a negative impact on our planet: global warming and ocean acidification could leave an indelible mark on Earth. The slow development process and low efficiency of alternatives such as nuclear fusion and solar power makes it difficult to wean ourselves off the use of conventional fossil fuels.

An alternative strategy is to develop technologies that mitigate the deleterious effects of fossil fuels. Carbon capture is one such approach, and proposes to use porous materials that can adsorb and store emitted carbon dioxide at the end of the energy generation process to prevent it from entering the atmosphere.

Metal–organic frameworks (MOFs) are one promising class of porous solid-state materials. These crystalline networks are made up of metal ions or clusters interconnected by organic molecules.

“The periodic arrangement of these organic and inorganic molecular building blocks gives MOFs one of their most defining properties: a functional and tunable pore system,” said KAUST Professor of Chemical Science Mohamed Eddaoudi. “The deliberate control of the available and accessible space shape, size and functionality enables adsorbing and storing select gases.”

The translation of a prospective MOF that selectively captures carbon dioxide from a laboratory scale to industrial scale settings requires the development of economical synthetic approaches. The manufacturing process frequently involves organic solvents that can also have a negative impact on the environment.

Eddaoudi and colleagues from KAUST’s Advanced Membranes & Porous Materials Research Center have developed a simple and solvent-free method to create a MOF adsorbent that selectively captures carbon dioxide.

The reported MOF structure, which they call SIFSIX-3-Ni, was made by dry mechanical mixing the organic component pyrazine with the inorganic solid NiSiF6 at a molar ratio of four to one, and then wetting with a few drops of water. This was heated for four hours at 65 degrees Celsius and then at 105 degrees Celsius for an additional four hours.

The team confirmed the efficient adsorption of carbon dioxide, even in an environment with very low carbon dioxide content. The authors also proved that the material is tolerant to the acidic gas hydrogen sulfide that is present in natural gas.

Reference

1.  Shekhah, O., Belmabkhout, Y., Adil, K., Bhatt, P. M., Cairns, A. J. & Eddaoudi, M. A facile solvent-free synthesis route for the assembly of a highly CO2 selective and H2S tolerant NiSIFSIX metal–organic framework. Chemical Communications 51, 13595-13598 (2015). | article

Hybrid Solar Cell Converts both Light and Heat: Increasing Efficiency: Video

Posted: Oct 28, 2015
Scientists have developed a new hybrid, solar-energy system that harnesses the full spectrum of the sun’s radiation by pairing a photovoltaic cell with polymer films. The films convert the light that goes unused by the solar cell into heat and then converts the heat into electricity.

A display changes colors, powered solely by a new hybrid solar-energy device.

A display changes colors, powered solely by a new hybrid solar-energy device. (© ACS)

They report on their device, which produces a voltage more than five times higher than other hybrid systems, in the journal ACS Nano (“Photothermally-Activated Pyroelectric Polymer Films for Harvesting of Solar Heat with a Hybrid Energy Cell Structure”).

Solar cells today are getting better at converting sunlight to electricity, but commercial panels still harvest only part of the radiation they’re exposed to. Scientists are working to change this using various methods.

One approach is to hybridize solar cells with different materials to capture more of the sun’s energy. Eunkyoung Kim and colleagues turned to a clear, conductive polymer known as PEDOT to try to accomplish this.
The researchers layered a dye-sensitized solar cell on top of a PEDOT film, which heats up in response to light. Below that, they added a pyroelectric thin film and a thermoelectric device, both of which convert heat into electricity. The efficiency of all components working together was more than 20 percent higher than the solar cell alone. With that boost, the system could operate an LED lamp and an electrochromic display.

Source: American Chemical Society

Nanoporous Material Combines the Best of Batteries and Supercapacitors for ESS (Energy Storage Systems)

Photo: Jeff Fitlow

Researchers at Rice University in Houston, Texas, have developed a nanoporous material that has the energy density (the amount of energy stored per unit mass) of an electrochemical battery and the power density (the maximum amount of power that can be supplied per unit mass) of a supercapacitor. It’s important to note that the energy storage device enabled by the material is not claimed to be either of these types of energy storage devices.

The research community has wearied of claims that some new nanomaterial enables a “supercapacitor,” when in fact the energy storage device is not a supercapacitor at all, but a battery. However, in this case, the Rice University researchers, led by James Tour, who is known for having increased the storage capacity of lithium-ion (Li-ion) batteries with graphene, don’t make any claims that the device they created is a supercapacitor. Instead it is described as an electrochemical capacitor with nanoporous nickel-fluoride electrodes layered around a solid electrolyte that is flexible and relatively easy to scale up for manufacturing.

The issue of appropriate nomenclature aside, the reported performance figures for this energy storage material are very attractive. In the Journal of the American Chemical Society (“Flexible Three-Dimensional Nanoporous Metal-Based Energy Devices“),  the researchers report energy density of 384 watt-hours per kilogram (Wh/kg), and power density of 112 kilowatts per kilogram (kW/kg).

To give some context to these numbers, a typical energy density for a Li-ion battery is 200Wh/kg, whereas commercially available supercapacitors store around 5- to 25 Wh/kg and research prototype supercapacitors have made claims of anywhere from 85 to 164 Wh/kg. In terms of power density, the numbers for the new nanoporous material is in line with those of supercapacitors, which range from 10 to 100 kW/kg—far higher than the 0.005 to 0.4kW/kg that batteries can deliver.

“The numbers are exceedingly high in the power that it can deliver, and it’s a very simple method to make high-powered systems,” Tour said in a press release. “We’re already talking with companies interested in commercializing this.”

To make the battery-supercapacitor hybrid, the Rice team deposited a nickel layer on a backing material. They then etched the nickel layer to create pores five nanometers in diameter. The result is high surface area for storing ions. After removing the backing, the nickel-based electrode material is wrapped around a solid electrolyte of potassium hyrodroxide in polyvinyl alcohol. In testing, the researchers found that there was no degradation of the pore structure after 10 000 charge-discharge cycles, or any significant degradation of the electrode-electrolyte interface.

“Compared with a lithium-ion device, the structure is quite simple and safe,” said Yang Yang, lead author of the paper, in the press release. “It behaves like a battery but the structure is that of a supercapacitor. If we use it as a supercapacitor, we can charge quickly at a high current rate and discharge it in a very short time. But for other applications, we find we can set it up to charge more slowly and to discharge slowly like a battery.”

With the device’s flexibility and high charge-up rate, it’s possible to imagine this storage device powering flexible mobile devices. However, charging rates for the battery/supercapacitor will be limited by the typical 200-amp 240V single-phase residential service, which is only capable of providing (absent any other load) only 48 kW.

MIT: Big Range for Tiny Graphene Pores: May improve Commercial Membranes for Water Purification: Requiring Less Energy

Researchers created pores in a graphene sheet (in purple) and then placed it over a layer of silicon nitride (in blue) that had been punctured by an ion beam. This allows specific hydrated ions, which are surrounded by a shell of water molecules, to pass through.

Image: Jose-Luis Olivares/MIT

MIT News Office
October 5, 2015

The surface of a single cell contains hundreds of tiny pores, or ion channels, each of which is a portal for specific ions. Ion channels are typically about 1 nanometer wide; by maintaining the right balance of ions, they keep cells healthy and stable. Like biological channels, graphene pores are selective for certain types of ions.

Now researchers at MIT have created tiny pores in single sheets of graphene that have an array of preferences and characteristics similar to those of ion channels in living cells.

Each graphene pore is less than 2 nanometers wide, making them among the smallest pores through which scientists have ever studied ion flow. Each is also uniquely selective, preferring to transport certain ions over others through the graphene layer.

“What we see is that there is a lot of diversity in the transport properties of these pores, which means there is a lot of potential to tailor these pores to different applications or selectivities,” says Rohit Karnik, an associate professor of mechanical engineering at MIT.

Karnik says graphene nanopores could be useful as sensors — for instance, detecting ions of mercury, potassium, or fluoride in solution. Such ion-selective membranes may also be useful in mining: In the future, it may be possible to make graphene nanopores capable of sifting out trace amounts of gold ions from other metal ions, like silver and aluminum.

Karnik and former graduate student Tarun Jain, along with Benjamin Rasera, Ricardo Guerrero, Michael Boutilier, and Sean O’Hern from MIT and Juan-Carlos Idrobo from Oak Ridge National Laboratory, publish their results today in the journal Nature Nanotechnology.

Dynamic personality

In living cells, the diversity of ion channels may arise from the size and precise atomic arrangement of the channels, which are slightly smaller than the ions that flow through them.

“When nanopores get smaller than the hydrated size of the ion, then you start to see interesting behavior emerge,” Jain says.

In particular, hydrated ions, or ions in solution, are surrounded by a shell of water molecules that stick to the ion, depending on its electrical charge. Whether a hydrated ion can squeeze through a given ion channel depends on that channel’s size and configuration at the atomic scale.

Karnik reasoned that graphene would be a suitable material in which to create artificial ion channels: A sheet of graphene is an ultrathin lattice of carbon atoms that is one atom thick, so pores in graphene are defined at the atomic scale.

To create pores in graphene, the group used chemical vapor deposition, a process typically used to produce thin films. In graphene, the process naturally creates tiny defects. The researchers used the process to generate nanometer-sized pores in various sheets of graphene, which bore a resemblance to ultrathin Swiss cheese.

The researchers then isolated individual pores by placing each graphene sheet over a layer of silicon nitride that had been punctured by an ion beam, the diameter of which is slightly smaller than the spacing between graphene pores. The group reasoned that any ions flowing through the two-layer setup would have likely passed first through a single graphene pore, and then through the larger silicon nitride hole.

The group measured flows of five different salt ions through several graphene sheet setups by applying a voltage and measuring the current flowing through the pores. The current-voltage measurements varied widely from pore to pore, and from ion to ion, with some pores remaining stable, while others swung back and forth in conductance — an indication that the pores were diverse in their preferences for allowing certain ions through.

“The picture that emerges is that each pore is different and that the pores are dynamic,” Karnik says. “Each pore starts developing its own personality.”

New frontier

Karnik and Jain then developed a model to interpret the measurements, and used it to translate the experiment’s measurements into estimates of pore size. Based on the model, they found that the diameter of many of the pores was below 1 nanometer, which — given the single-atom thickness of graphene  — makes them among the smallest pores through which scientists have studied ion flow.

With the model, the group calculated the effect of various factors on pore behavior, and found that the observed pore behavior was captured by three main characteristics: a pore’s size, its electrical charge, and the position of that charge along a pore’s length.

Knowing this, researchers may one day be able to tailor pores at the nanoscale to create ion-specific membranes for applications such as environmental sensing and trace metal mining.

“It’s kind of a new frontier in membrane technologies, and in understanding transport through these really small pores in ultrathin materials,” Karnik says.

Meni Wanunu, an assistant professor of physics at Northeastern University, says the group’s work with graphene membranes may significantly improve on commercial membranes used for water purification, which require large amounts of pressure to push water through.

“If these were replaced with graphene, since it is so thin, the pressure required to push water through would be among the lowest imaginable, if not the lowest,” says Wanunu, who was not involved in the research. “However, it is only through a fundamental understanding of ion transport that the overall anticipated behaviors of bulk graphene membranes can be drawn. The work here is fundamental, and will surely guide current and future graphene membrane design principles in years to come.”

This research was funded, in part, by the U.S. Department of Energy.

Synthetic Batteries for the Energy Revolution

Posted: Oct 21, 2015
Sun and wind are important sources of renewable energy, but they suffer from natural fluctuations: In stormy weather or bright sunshine electricity produced exceeds demand, whereas clouds or a lull in the wind inevitably cause a power shortage.

For continuity in electricity supply and stable power grids, energy storage devices will become essential.

So-called redox-flow batteries are the most promising technology to solve this problem. However, they still have one crucial disadvantage: They require expensive materials and aggressive acids.

A team of researchers at the Friedrich Schiller University Jena (FSU Jena), in the Center for Energy and Environmental Chemistry (CEEC Jena) and the JenaBatteries GmbH (a spin-off of the University Jena), made a decisive step towards a redox-flow battery which is simple to handle, safe and economical at the same time: They developed a system on the basis of organic polymers and a harmless saline solution.

“What’s new and innovative about our battery is that it can be produced at much less cost, while nearly reaching the capacity of traditional metal and acid containing systems,” Dr. Martin Hager says.

CAPTION  Jena research team and its innovative battery (from left to right) are: Prof. Dr. Ulrich S. Schubert, Tobias Janoschka und Dr. Martin Hager.

The scientists present their battery technology in the current edition of the renowned scientific journal Nature (“An aqueous, polymer-based redox-flow battery using non-corrosive, safe, and low-cost materials”).

In contrast to conventional batteries, the electrodes of a redox-flow battery are not made of solid materials (e.g., metals or metal salts) but they come in a dissolved form: The electrolyte solutions are stored in two tanks, which form the positive and negative terminal of the battery.

With the help of pumps the polymer solutions are transferred to an electrochemical cell, in which the polymers are electrochemically reduced or oxidized, thereby charging or discharging the battery. To prevent the electrolytes from intermixing, the cell is divided into two compartments by a membrane.

“In these systems the amount of energy stored as well as the power rating can be individually adjusted. Moreover, hardly any self-discharge occurs,” Martin Hager explains.

Traditional redox-flow systems mostly use the heavy metal vanadium, dissolved in sulphuric acid as electrolyte.

“This is not only extremely expensive, but the solution is highly corrosive, so that a specific membrane has to be used and the life-span of the battery is limited,” Hager points out.

In the redox-flow battery of the Jena scientists, on the other hand, novel synthetic materials are used: In their core structure they resemble Plexiglas and Styrofoam (polystyrene), but functional groups have been added enabling the material to accept or donate electrons. No aggressive acids are necessary anymore; the polymers rather ‘swim’ in an aqueous solution.

“Thus we are able to use a simple and low-cost cellulose membrane and avoid poisonous and expensive materials”, Tobias Janoschka, first author of the new study, explains. “This polymer-based redox-flow battery is ideally suited as energy storage for large wind farms and photovoltaic power stations,” Prof. Dr. Ulrich S. Schubert says. He is chair for Organic and Macromolecular Chemistry at the FSU Jena and director of the CEEC Jena, a unique energy research center run in collaboration with the Fraunhofer Institute for Ceramic Technologies and Systems Hermsdorf/Dresden (IKTS).

In first tests the redox-flow battery from Jena could withstand up to 10.000 charging cycles without losing a crucial amount of capacity. The energy density of the system presented in the study is ten watt-hours per liter. Yet, the scientists are already working on larger, more efficient systems. In addition to the fundamental research at the University, the chemists develop their system, within the framework of the start-up company JenaBatteries GmbH, towards marketable products.

Source: Friedrich-Schiller-Universitaet Jena

Energy storage: It’s Canada’s moment

 

Canada has a chance to add a new dimension to its energy economy – one that is clean, profitable and globally groundbreaking.

The opportunity is electricity storage, which until now has been limited by technology to a relatively modest scale. That’s about to change. And it means that Canada – and specifically Ontario – can become an ideal seedbed for storage technology, because there are ready markets for both large- and small-scale storage systems.

First, the large scale. Ontario has a fleet of nuclear generators that operate around the clock, and come close to filling the demand for power at off-peak hours. In addition, Ontario has developed a large renewable energy sector of wind and solar generation (in addition to its traditional hydro stations.) Problems sometimes arise when the natural weather cycles that drive wind and solar production are out of synch with the market cycle. On a sunny, breezy Saturday afternoon in May, with the nuclear plants running flat out, the hydro stations churning out power with the spring runoff and solar and wind systems near peak production, Ontario may have more electricity than it needs.

Our electricity system operators have a solution, of course: Sell the excess electricity to our neighbours. But since our neighbours are often in the same boat, Ontario must cut the price close to zero – or in extreme situations, even pay neighbouring states or provinces to absorb our overproduction.

Wouldn’t it make far more sense to store that excess energy, knowing that it will be needed in a matter of days, or even hours? What’s been lacking is the technology to do the job.

That’s changing however, as Ontario’s current program to procure 50 megawatts of storage capacity demonstrates. Companies with a variety of approaches are working hard to bring their solutions to market – many of them clustered at the MaRS centre in Toronto. Some, such as Hydrogenics Corp., convert electricity into hydrogen, which can be used to supplement natural gas.

My own company, NRStor, has partnered with Temporal Power and is operating a flywheel storage system in Minto, Ont., that helps the market operator to maintain consistent voltage on the grid.

Of course, businesses around the globe are looking at the same opportunities as we are, and here lies the opportunity for Canada to rebrand its energy economy.

A recent report by Deutsche Bank calls battery storage the “holy grail of solar penetration,” and believes that with the current rate of progress in improving efficiency, mass adoption of lithium ion batteries at a commercial/utility scale could occur before 2020.

Analysis by Prof. Andrew Ford of Washington State University calculates that a 1,000-megawatt air storage system from U.S.-based General Compression Inc. could deliver $6- to $8-billion of value to Ontario – in the form of lower energy costs to local utilities – over a 20-year period. All this is of interest to large-scale electricity system operators, big utilities and their customers.

But there is another reason for us to pay attention to energy storage – a reason grounded on a much more human scale. There are still large rural areas around the globe where there is no reliable electrical grid – including Northern Canada.

There is great potential for these communities, including remote First Nations communities, to improve their standard of living by installing microscale renewable generation in combination with storage, and relying less on carbon-spewing diesel generators, powered by fuel that must be transported long distances at great expense.

Storage is the key to making renewable energy a fully competitive component of any electrical grid. It can make our grid cleaner and more efficient, for the benefit of all consumers – large and small, urban and rural. We have the chance, in Canada, to become world leaders in developing this technology. Let’s seize it.

Annette Verschuren is the chairwoman and CEO of NRStor and on the board of MaRS Discovery District.

Annette Verschuren is speaking at the Cleantech Canadian Innovation Exchange (CIX Cleantech) conference in Toronto on Oct. 15.

Water movement on graphene surfaces could enable innovative sensors and filters

Oct 21, 2015Graphene

Scientists at University College London (UCL) have identified a potentially faster way of moving molecules across the surfaces of graphene and other materials. The team carried out computer simulations of tiny droplets of water as they interact with graphene surfaces that reveal that the molecules can “surf” across the surface whilst being carried by the moving ripples of graphene.

The study shows that because the molecules were swept along by the movement of strong ripples in the carbon fabric of graphene, they were able to move at a fast rate, at least ten times faster than previously observed.

It was also found that by altering the size of the ripples and the type of molecules on the surface, it’s possible to achieve fast and controlled motion of molecules other than water.

Water on graphene surfaces image

This research reveals an interesting new diffusion mechanism for motion across graphene that is inherently different from the usual random movements seen on other surfaces.

The motion of atoms and molecules across the surface of materials is wildly important for many applications, such as the diffusion of molecules across the surface of catalysts, crystal growth or filtration.

This research opens up a range of possibilities for industrial applications such as improved sensors and filters.

Source: eurekalert

Yale Study Confirms: Fracking Does Not Contaminate Drinking Water

Yale researchers have confirmed that hydraulic fracturing – also known as “fracking” – does not contaminate drinking water. (Photo : Flickr: Konstantin Stepanov)

Yale researchers have confirmed that hydraulic fracturing – also known as “fracking” – does not contaminate drinking water. The process of extracting natural gas from deep underground wells using water has been given a bad reputation when it comes to the impact it has on water resources but Yale researchers recently disproved this myth in a new study that confirms a previous report by the Environmental Protection Agency (EPA) conducted earlier this year.

After analyzing 64 samples of groundwater collected from private residences in northeastern Pennsylvania, researchers determined that groundwater contamination was more closely related to surface toxins seeping down into the water than from fracking operations seeping upwards. Their findings were recently published in the journal Proceedings of the National Academy of Science.

 

“We’re not trying to say whether it’s a bad or good thing,” Desiree Plata, an assistant professor of chemical and environmental engineering at Yale University, told News Three in a Skype interview. “We saw there was a correlation between the concentration and the nearest gas well that has had an environmental health and safety violation in the past.”

Researchers also noted that shale underlying the Pennsylvania surface did not cause any organic chemicals to seep into groundwater aquifers. However, these findings may not be applicable to all locations worldwide.

“Geology across the country is very different. So if you’re living over in the New Albany-area shale of Illinois, that might be distinct from living in the Marcellus shale in Pennsylvania,” Plata explained.

Researchers from Duke University also recently gave people a reason to trust fracking companies. In a study published in Environmental Science & Technology Letters, scientists explained that hydraulic fracturing accounts for less than one percent of water used nationwide for industrial purposes. This suggested that the natural gas extraction processes are far less water-intensive than we previously thought.

It’s hoped that these studies will help people better understand the safety of fracking.

Desalination: A Promising Solution to Drought or Just Another Misguided Stab In the Dark?

*** Note to Readers: We at Team GNT™ believe very strongly that “Water Solutions for a thirsty Planet” can be and will be enabled by Nanotechnology. Whether those solutions come in the form of Nano Enabled Membrane Technology, Catalyst-Thermal Technology or (Yet To Be Discovered-Developed Technology) … we expect “Great Things from Small Things”! As such we always appreciate “perspective articles” such has been offered here.

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*** Re-Posted from “One-Green-Planet” ***

All of terrestrial life depends on freshwater. From densely populated cities to rural communities, farmland and forestland, and domestic and wild animals, all are in need of clean water to sustain them. Miraculously, just a small percentage of the water on earth is actually available as freshwater.

According to the U.S. Geological Service, only about 2.5 percent of all the water on planet earth is freshwater. And only 1.2 percent of that is most easily accessible on the earth’s surface in the form of lakes, rivers, swamps, soil moisture, and permafrost. An additional 30.1 percent exists as groundwater while the majority of this freshwater, 68.7 percent to be exact, is locked up as frozen glaciers and ice caps.

Flickr

If you’re reading into the numbers, it would appear that the majority of freshwater is not easily accessible to us for human use. And, unfortunately, many human activities are causing harm to the natural water cycle that’s in place, making freshwater resources even more difficult to access and utilize. Building impervious structures such as buildings and paved roads makes it difficult for precipitation to be absorbed by the land to replenish groundwater resources. We also impact not only the natural flow of water with barriers like dams, but also the composition and safety of water with our pollution. We are often too aggressive in harvesting water from groundwater and surface supplies, depleting underground reserves as well as rivers and lakes.  And our contributions to climate change have impacted precipitation and evaporation rates, making the resource even more unstable and less predictable.

It is in our best interest to treat freshwater supplies with the utmost respect, and yet we’re losing out on this invaluable resource due to our own ignorance and negligence.

So, what can we do to save our water? There are, luckily, a variety of solutions. From education and conservation to emerging technologies, we are hatching up a plethora of solutions to our water woes. One of the strategies that many countries are using is desalination where salt water is essentially converted into freshwater. There’s plenty of salt water on the planet, as we know, so this sounds like a fabulous idea. Or is it?

Getting freshwater From Saltwater – How?

Desalination is a process that converts salt water to freshwater by removing salts and other minerals, leaving behind freshwater, potable water. While there are a variety of methods to accomplish this task, they can be grouped mainly into two types.

The first method, thermal desalination, involves the heating of saline water. Salts are left behind while freshwater is converted to steam and is collected, ultimately to condense back into water that is now saline-free and ready for use in an instance where freshwater is desired.

The second type of desalination involves the use of membranes to separate salt and other minerals from water. Pressure or electric currents may be used to drive saline water through a membrane which acts as a filter. Freshwater ends up on one side of the membrane while saline water stays on the other side as a form of waste.

Of course, these are very, very basic descriptions of some pretty complex and evolving technologies. But they do offer a quick insight into what the process of desalination looks like in most settings around the world. For some individuals, this is the technology used to provide them with clean drinking water.

Where Are Desalination Plants Working Now?

Desalination is a technology that has been around for quite some time and is seeing improved growth around the world in the face of increasing water demands. Since 2003, Saudi Arabia, the United Arab Emirates and Spain have led the world in desalination capacities. As of 2013, there were over 17,000 desalination plants worldwide in roughly 150 countries, providing more than 300 million people with at least some of their daily freshwater needs.

Israel is one successful case-study when it comes to the value of desalination. The nation currently has a quarter of its freshwater needs met through four desalination plants that treat mainly brackish well water (water that is part salt/part fresh). Israel’s desalination plants currently produce 130 million gallons of potable water a year and they are aiming to increase that number to 200 million gallons a year by 2020. While aggressive conservation efforts also helped ease the impact of severe drought, desalination has certainly been an important piece of solving a water crises.

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Singapore is another interesting story when it comes to desalination. The country is currently pushing to improve its desalination capacity in order to gain independence in its freshwater resources. Right now it depends heavily on neighboring Malaysia to import clean water. For Singapore, desalination offers the country the chance to provide citizens freshwater even where saline water sources are much more available, ultimately becoming more independent and self-reliable.

As countries all over the world increase their capacity for desalination plants, drought-stricken areas like the United States southwest are taking note and investing in this technology. In fact, construction on the Western hemisphere’s largest desalination plant is nearly complete in San Diego, California and is expected to open for operation later this year. In the face of severe drought, desalination is becoming a much more appetizing option for this region to put its plentiful access to seawater to good use and to alleviate some of the pressures that developed and agricultural areas are placing on freshwater sources.

Is This The Answer to Water Shortages Worldwide?

Whether or not desalination is the savior for water woes is a complex debate and answers will probably vary depending on who you are asking. You’ll find there are activists, scientists, public agencies, governments, and citizens on both sides of the debate.

Ecological Impact

The first input that comes to mind when you think of desalination is probably the saline water that’s being treated, right? Depending on the source of this saline water, there may be a variety of detrimental impacts to the local ecology to consider when it comes to desalination operations.

Some desalination plants use direct intake methods to gather saline water, meaning they extract water directly from the water column, either from the surface or at greater depths in the ocean. The problem with this extraction method is that, in addition to taking in saltwater that can become a viable freshwater source, a host of marine life is also sucked up in the process. Algae, plankton, jellyfish, fish, and larva of many species can all easily be killed with this direct intake method for harvesting sea water.

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The impact of ocean water extraction on local marine life is not well understood, however, experts will note there are a variety of ways to skate around issues like this. One such method is indirect intake where pipes are buried in the substrate and intake water that is actually filtered down through the sand first. Marine life damage is largely eliminated using this method. Physical barriers to intake pipes may also be utilized where screens or meshes are able to keep smaller marine creatures out of the intake pipes. And behavioral deterrents, like bubble screens and strobe lights, are another option to discourage marine animals from swimming too close to intake systems where they become trapped.

Saline water that is being harvested for desalination projects are not the only issue creating ecological impacts for this water treatment system. The output of wastewater is another issue that critics point out when it comes to desalination. Water discharged from desalination plants has a higher level of saline than the body of water it is entering. While some creatures can tolerate change in salinity, others cannot and may be killed on contact. Discharging water that has been heated in the desalination process can also cause temperature spikes and stress to any aquatic life in a close radius. And, the water discharged from desalination operations may also have an altered chemical composition given the added antifouling agents, heavy metals, chlorine, antiscaling chemicals, and cleaning solutions used in the process. All have a potential to detrimentally impact the local ecology surrounding a desalination operation.

Some solutions for wastewater from desalination operations already exist. Because saline water is more likely to sink and move along the ocean bottom, discharging it upward can help promote mixing of wastewater more quickly to disperse salinity and weaken the impacts that concentrated salt levels can cause. Additionally, plants can invest in technology to lessen the amount of chemicals they use in the treatment process, and even attempt to let wastewater evaporate, leaving behind only solid waste for plant operators to dispose of. These may not be perfect solutions, but they are attempts to make desalination operations more friendly to the local ecology.

Energy Requirements

One major difficulty with fully embracing desalination has to do with the major energy inputs the technology requires. Costs attributed to desalination depend largely on energy costs which can and do fluctuate from year to year. Roughly 60 percent of the cost of operating a thermal desalination plant comes from the energy costs to operate the plant, while 36 percent of the cost to run a reverse osmosis plant comes from the energy it uses.

Greenhouse gas emissions associated with desalination plants depend heavily on the type of energy utilized. In an area where fossil fuels are burned to make electricity, emissions associated with desalination will be higher. Additionally, if a desalination plant relies heavily on hydroelectric power, a drought in the area may increase the cost of energy from the electric plant and thus the cost to run the desalination plant.

Money

As with any new and growing technology, there can be an expected higher cost than the conventional way of doing things. Desalination is no exception. Using San Diego County as an example, we can see just how much more expensive desalination is than other methods of providing freshwater. The cost to save an acre-foot of water through conservation and user education around efficiency may fall anywhere between $150 and $,1000. Importing an acre-foot of water may cost somewhere between $875 and $975. Recycling an acre-foot of potable water has a range in cost between $1,200 and $1,800. And providing an acre-foot of freshwater through seawater desalination would cost between $1,800 and $2,800. As local agencies and governments come up against budget cuts and financing difficulties, it may be impossible to justify this technology in the face of cheaper options that provide the same results.

Citizens will see an increase in their water bill as more of their freshwater is sourced from expensive desalination processes. This rise in basic living costs in the face of economic hardship may be difficult to justify, especially for a resource as important as freshwater. Desalination is certainly not a cost-saving choice.

Is It A Go?

It is certainly important to note the improvements that technology like desalination can provide to society. Especially as we are faced with increased challenges to meet the needs of a growing population, it is important to have a variety of options available to us.

While desalination is certainly an amazing option to convert water that was once too salty for human-use into something that can quench thirsts, maintain sanitation, and irrigate agriculture, one may be left wondering if the cost is really worth it. There are still many improvements left to be made to make this a more environmentally friendly option. As it stands, it is not without some major drawbacks when it comes to local ecology destruction, energy use, and greenhouse gas emissions. And it is certainly a very expensive option when you consider how little money it would take to simply educate the masses on how to conserve water.

Desalination is a wonderful testament to the human mind and inventive capacity, but it may simply be a very advanced and expensive method for maintaining our ignorance to the natural world with exist within. We may be able to provide freshwater in places where it didn’t previously exist, but what’s the point if people continue to remain ignorant to how to better use the water we already have? In the face of a crisis this may certainly be a valuable technology, but we have not even yet begun to address some of the issues that are causing our water shortages in the first place. And that’s an issue we need to work out through education and conversation around sustainability rather than throwing money into more expensive technology.

Lead Image Source: JohnKay/Flickr

Supercritical Fluids Help Stabilize Quantum Dot Formation: Applications for Photoluminescent Materials; Bio-Imaging; Photonics and Optoelectronics

Researchers have used supercritical CO2—CO2 at a temperature and pressure above the critical point such that distinctions between the liquid and gas phase do not exist—to stabilize the production of quantum dots (QDs). Their research has been published in The Journal of Supercritical Fluids and selected by the editor-in-chief as a featured article.
Semiconductor nanocrystals known as QDs are increasingly being used as photoluminescent materials in bio-imaging, photonics, and optoelectronic applications. In these applications, QDs must have stable photoluminescence properties, which is achieved by chemically modifying the surface of the QDs.
However, chemical modification of the surface typically requires large amounts of organic solvents that are harmful to the environment. To solve this problem, many researchers have attempted to synthesize polymer-nanoparticle composites by using supercritical fluid (SCF)-based technology. Supercritical CO2 has emerged as the most extensively studied SCF medium, because it is readily available, inexpensive, nonflammable, and environmentally benign.
Toyohashi Tech researchers, in cooperation with researchers at the National Institute of Technology, Kurume College, have investigated the formation of nanostructured material using supercritical CO2. They have demonstrated the formation of composite nanoparticles of luminescent ZnO QDs and polymers by dispersion polymerization in supercritical CO2. As a result of the supercritical-CO2-assisted surface modification of QDs, the QDs were well dispersed in the polymer matrix and showed high luminescence.
“Unfortunately, the photoluminescence properties of pristine luminescent QDs were quenched in supercritical CO2. The surface structure of the QDs was destroyed by supercritical CO2,” explained Associate Professor Kiyoshi Matsuyama from the National Institute of Technology, Kurume College.
“We found that the quenching of ZnO QDs could be prevented by coating with silica to obtain PMMA-ZnO composite QDs with high luminescence using a supercritical-CO2-assisted surface modification with polymer.”
The research shows that the supercritical-fluid-assisted process provides an environmentally benign route for producing stabilized luminescent materials.
The article can be found at: Matsuyama et al. (2015) Formation of Poly(Methyl Methacrylate)-ZnO Nanoparticle Quantum Dot Composites by Dispersion Polymerization in Supercritical CO2.