Archive for January 2007

Keeping Desalination Plants Clean

January 19, 2007

As much as a third of the cost of water desalination is made up of maintenance costs. So a fair amount of thought has to be put into making surfaces that come in contact with air & water clean. I have mentioned in a previous post called The Pipeline that there is a product called Sharkote-– a US navy funded coating announced in 2005 that immitates the skin of a shark. Sharkote might be used inside the pipes that carry water. (barnicles & algae don’t grow on shark skin like they do on whale skin so Sharkote would also serve well to reduce maintenance in algae farms)

Recently, a number of other possible kinds of surface applications have come out of the labs. This first application looks like its more suitable for places inside desalination plants– surfaces that are damp but not directly connected to fresh water production.

Spiky surface ‘kills infections’

 

Influenza (Science Photo Library/ NIBSC)

The coating inactivated the influenza virus

Adding a special “spiky” coating to surfaces can kill bacteria and viruses, research suggests. US scientists found painting on spike-like structures kept the surfaces infection-free.

The spikes, they believe, rupture bacteria and virus particles on contact, inactivating them.

The team, writing in the Proceedings of the National Academy of Sciences, suggest their findings could help to fight the spread of diseases.

Given the simplicity of the coating procedure, it should be applicable to various common materials

Massachusetts Institute of Technology

The researchers painted glass with long chains of molecules, called polymers, which anchored to the surface to form tentacle-like spikes.

When the team then applied the surfaces with E. coli and Staphylococcus aureus (both common disease-causing forms of bacteria) and the influenza virus, they found the coating killed them with 100% efficiency within minutes.

Click here for the rest of the article.

This next product might be used for outside surfaces of desalination plants that face the sun– or green houses used for biodiesel and desalination production.)

 

Eco glass cleans itself with Sun

 

By Jo Twist
BBC News Online science and technology staff


Pilkington Activ glass means the view is clear

Normal glass (left) and Activ (right) makes for clear views

A revolutionary kind of glass that needs little cleaning could mean soap and chamois are banned for good. The Pilkington Activ glass has a special nano-scale – extremely thin – coating of microcrystalline titanium oxide which reacts to daylight.

This reaction breaks down filth on the glass, with no need for detergent. When water hits it, a hydrophilic effect is created, so water and dirt slide off.

It is one of four finalists for the eminent MacRobert engineering award.

The prize is given out by the UK’s Royal Academy of Engineering for technological and engineering innovation.

‘Nano’ cleaning

“Pilkington Activ is based on titanium dioxide, which is used in foodstuffs, toothpastes, and sun cream,” explained Dr Kevin Sanderson, one of the team members who developed Activ at Pilkington’s technical research centre.

“But usually it is a white powder which is not ideal for glass because you can’t see though it.

Each time harsh chemicals are used, they are washed off into ground, which produces contamination. What we say here is that you can just spray water on top

Dr Kevin Sanderson, Pilkington

“So we used it in a thin film form – 15 nanometres thick – so that it appears as close to normal glass as it can.”

Although not strictly nanotechnology, the special coating and the chemical reactions happen at the nano-scale (one thousand millionth of a metre).

The titanium dioxide coating on the glass had two properties that made it special, said Dr Sanderson.


Click here to see how the glass works

 

Click here to read the rest of the article.

This last coating is like the coating that is activated by the sun. However, it works in wavelengths that would be suitable for light bulbs. So it would prevent the growth of fungus and the build up of dirt on the damp inner surfaces of a desalination plant.

 

Self-cleaning bathroom on the way

 

By Marina Murphy


Taps (BBC)

Few of us enjoy the weekly blitz on the bathroom

Nanotechnology may yet rescue us from the drudgery of the weekly ritual of blitzing the bathroom.

Scientists in Australia have developed an environmentally friendly coating containing special nanoparticles that could do the job of cleaning and disinfecting for us.

“If you have self-cleaning materials, you can do the job properly without having to use disinfectants and other chemicals,” says researcher Rose Amal at the Particles and Catalysts Research Group, University of New South Wales, where the coating is being developed.

Previously self-cleaning materials were limited to outdoor applications because ultraviolet light was required to activate the molecules in the coatings.

Less time cleaning the bathroom is rather appealing

Mary Taylor, Friends of the Earth

These surfaces contain tiny particles of titanium dioxide, which become excited when they absorb ultraviolet light with a wavelength of less than 380 nanometres.

Light activated

This gives the particles an oxidizing ability stronger than chlorine bleach. The excited particles can break down organic compounds and kill bacteria.

The new coating contains modified particles of titanium dioxide, which are doped with other cations like iron or vanadium and anions like oxygen, nitrogen or carbon.

This coating can absorb light at the higher wavelengths in visible light, such as the bathroom light.

E. Coli (BBC)

The coating can kill bacteria such as E. coli

Lab experiments revealed the surface of coated glass could kill the bacteria E. coli (Escherichia coli) and degrade volatile organic compounds in visible light.

The oxidising properties also mean fungus cannot grow on the surface. And because the coating is hydrophobic – it does not like water – the water simply slides away carrying any dirt with it, rather than gathering as droplets.

Using the coating in baths and sinks would not pose any problems with skin irritation, according to Amal.

“When the bath is filled, the water would attenuate the light so I don’t think the surface would activate. It will only be active if the light can reach the surface,” she says.

For the rest of the article click here.

 

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Distillation Desalination Using Low Pressure.

January 12, 2007

Will someone kindly do the math that shows the energy needed to raise the temperature of water to steam vs the energy needed to lower the pressure on water to near vacume state so that it flashes to steam. Email the formula to me at cakilmer at yahoo.com and I’ll post it.

(See below for updated formula.)

Why?

Well it would be helpful to verify the claim that its more energy efficient to lower the pressure around water so as to flash it to steam than to raise the temperature of water to boil it to steam.

I first heard about this from one of the tenor guys in my community chorus last fall. He was doing consulting work for some outfit or other. I never got the details. They were looking into temperature differentials between say water at the surface and water +1000 feet down to power their vacume pumps. But the whole thing worked out to be too expensive. Recently, a report was published in New Scientist about some UK researchers who are working on a device which will use wave action to power a pump which will lower pressure and thus the temperature needed to evaporate (and then distill) water.

I mention this by way of introducing some Florida Atlantic University Grad Students who claim they can reduce the cost of water desalination by a factor of ten by using waste heat as an energy source to lower the pressure on water so that it will flash to steam. ( The key concept here is using heat to lower pressure on water to flash it to steam — rather than using the heat to raise the temperature of water to boil it.)

“I’ve been able to build this incredibly eccentric machine, spill gallons of water everywhere, and generally act like the mad scientist I always wanted to be as a kid,” said Eiki Martinson, one of the students involved. “Best of all, we solved one of the biggest problems of today — with an invention that can save millions of lives around the world.”

Martinson and Brandon Moore developed a process estimated to be 10 times more efficient than existing desalination technologies.

Sounds like these guys are having fun.

Moore and Martinson have been working in conjunction with their advisor, Dr. Daniel Raviv, an electrical engineering professor, to create a process that depends on recycling waste energy to distill water at a near vacuum and at room temperature. The project was initiated and sponsored by inventor Michael R. Levine, who currently holds 76 patents.

Levine said he came up with the first version of the distillation process on paper, and the FAU team took it to another level, augmenting the inventor’s idea — and creating the working apparatus.

The FAU team and Levine are working with power and water agencies to scale up the project so it can provide a million gallons of fresh water per day.

The students entered the project in the 2006 Collegiate Inventors Competition, a program of the National Inventors Hall of Fame Foundation. They were among the top seven finalists in the United States/Canada competition. This honor recognizes the innovations, discoveries and research by college and university students and their advisors for projects leading to inventions that can be patented.

How might this be incorporated into current tech.

Well– as I mentioned in Greenhouses For Desalinised Water and OilAquasonics technology is currently using waste heat to power a special nozzle that breaks water into a very fine mist. This mist is then hit with hot air. Instead of using waste heat to hit the mist — maybe the waste heat could be used to create a vacume. The question is–is the energy used to create the vacume orders of magnitude lower than the energy used to heat the water. And is the equipment needed to create the vacume relatively simple/inexpensive.

Update:

P=Pressure V=Volume T=Temperature

PV=nRT

PV/T=nR

P1V1/T1 = P2V2/T2=P3V3/T3

Carbon Nanotube Pipes And Ram Pumps

January 5, 2007

Darn, it seems these days that just about as fast as you can think of something — there’s a researcher around working on it. I’ve mentioned that it would be nice to shape a carbon nanotube filter into a pipe so that you could just stick it out in the ocean and fresh water would flow in. Here’s a researcher who has developed a carbon nanotube pipe for a purpose that might be adapted to water desalination.

Savvy Sieve: Carbon nanotubes filter petroleum, polluted water

http://www.sciencenews.org/articles/20040814/fob7.asp

Alexandra Goho

Bridging the gap between the nanoworld and the macroworld, researchers have created a membrane out of carbon nanotubes and demonstrated its potential for filtering petroleum and treating contaminated drinking water.

Scientists have long valued carbon nanotubes for their high strength and thermal properties (SN: 6/5/04, p. 363: Available to subscribers at http://sciencenews.org/articles/20040605/bob10.asp), yet it’s been a challenge to assemble nanotubes into useful materials large enough for people to hold in their hands.

a5235_1402.jpg

CLEAR PASSAGE. The wall of this tube-shaped filter is made of a single layer of densely packed carbon nanotubes.
Ajayan

Researchers at Rensselaer Polytechnic Institute in Troy, N.Y., and Banaras Hindu University in Varanasi, India, have now devised a method for making such large-scale structures and found an application for them.

The researchers injected a solution of benzene and ferrocene—the materials needed to assemble the carbon nanotubes—into a stream of argon gas and then sprayed the mixture into a quartz tube. The tube was located inside a furnace heated to 900°C.

A dense forest of carbon nanotubes formed on the inner walls of the quartz tube, yielding a hollow black cylinder. The researchers carefully removed the cylinder, which measured several centimeters long and up to a centimeter in diameter. It was composed of trillions of nanotubes. Each nanotube was only a few hundred microns long, essentially the thickness of the carbon cylinder’s wall.

“It’s a pretty amazing structure if you think about it,” says lead investigator Pulickel Ajayan of Rensselaer.

To test their cylinder as a filter, the researchers capped one end and let petroleum flow into it. As the oil passed through the cylinder’s wall, the membrane caught the large and complex hydrocarbons—a necessary step in making gasoline.

In a second experiment, Ajayan and his colleagues tested their filter on contaminated water. The researchers had added Escherichia coli, the bacterium responsible for a common intestinal disease, to a sample of water and passed the sample through the filter. Analysis of the filtered water showed that it was devoid of E. coli. More surprising, when the researchers tried water contaminated with the poliovirus, which is much smaller, not one virus made it through the sieve.

The researchers describe their results in the September Nature Materials.

“It’s very encouraging to see the development of new applications like these for carbon nanotubes,” says Alan Windle, a materials scientist at the University of Cambridge in England. “This is a nice piece of work.”

However, because the researchers didn’t compare their material’s performance with that of conventional ceramic or polymer filters, it’s difficult to gauge how competitive a carbon-nanotube filter would be, Windle adds.

Ajayan considers the new study just a first demonstration of nanotube filtration. However, he says, because the pore sizes in his team’s membrane are more uniform than those in conventional membranes, a carbon-nanotube filter could be especially effective at filtering out selected chemicals or microorganisms. What’s more, because carbon nanotubes can tolerate much higher temperatures than polymers can, periodic doses of heat could unclog the membrane without destroying it.


A later generation carbon nanotube filter might be shaped into the form of a house sized mushroom that sits on the ocean floor not too far from the coast. The carbon nanotube filter would be on the dome of the mushroom. A ram pump would be on the stem. The ram pump would use the weight and momentum of falling water to push the water ashore.

Ram pumps have only two moving parts, making them virtually maintenance-free. The basic idea behind a ram pump is simple. The pump uses the momentum of a relatively large amount of moving water to pump a relatively small amount of water uphill. To use a ram pump, you must have a source of water situated above the pump. For example, you must have a pond on a hillside so that you can locate the pump below the pond. You run a pipe from the pond to the pump. The pump has a valve that allows water to flow through this pipe and build up speed.


Ram pump in action

Once the water reaches its maximum speed this valve slams shut. As it does so the flowing water develops a great deal of pressure in the pump because of its inertia. The pressure forces open a second valve. High-pressure water flows through the second valve to the delivery pipe and the pressure in the pump falls. The first valve can then reopen to allow water to flow and build up momentum again, and so the cycle repeats.

Kind of a neat idea I think. But a couple years from now the cost of photovoltaics might come down sufficiently to make a solar pump an attractive low maintenance option or  carbon nanotube membranes may be able to cheaply extract hydrogen from water so as to make it dirt cheap to pump the water using hydrogen as an energy source. That way you don’t have a big contraption out in the ocean. All you have is a pipe. But a Ram Pump might serve as an intermediary step.