David Kirkpatrick

October 20, 2010

Fresh drinking water through solar power

This has the potential to be a real game changer. Among all the other problems out there, one very pervasive issue that gets intermittent lip service is potable, or the lack thereof, water. A portable desalination device could save lives in a variety of situations.

From the link:

The portable system could also be used in remote areas where supplying energy and clean water can be logistically complex and expensive, such as desert locations or farms and small villages in developing countries.

Led by Steven Dubowsky, a professor in both the Department of Mechanical Engineering and the Department of Aeronautics and Astronautics, and graduate students Amy Bilton and Leah Kelley, the group built a small prototype of the system last spring to test algorithms they had developed to run it. They have since demonstrated that the prototype is capable of producing 80 gallons of water a day in a variety of weather conditions. They estimate that a larger version of the unit, which would cost about $8,000 to construct, could provide about 1,000 gallons of water per day. Dubowsky and his students also estimate that one C-130 cargo airplane could transport two dozen desalination units — enough to provide water for 10,000 people.

The team presented a paper reporting preliminary results about its prototype system last week at the EuroMed 2010-Desalination for Clean Water and Energy Conference.

September 10, 2010

Single ions crossing a nano bridge

Filed under: Science — Tags: , , , , , — David Kirkpatrick @ 11:11 am

Don’t see any current practical applications — aside from desalination — on this right now (but now with a proof-of-concept I bet this’ll be leveraged in new research), but it is impressively cool.

From the link:

In the Sept. 10 issue of Science, MIT researchers report that charged molecules, such as the sodium and  that form when salt is dissolved in water, can not only flow rapidly through carbon nanotubes, but also can, under some conditions, do so one at a time, like people taking turns crossing a bridge. The research was led by associate professor Michael Strano.

The new system allows passage of much smaller molecules, over greater distances (up to half a millimeter), than any existing nanochannel. Currently, the most commonly studied nanochannel is a silicon nanopore, made by drilling a hole through a silicon membrane. However, these channels are much shorter than the new nanotube channels (the nanotubes are about 20,000 times longer), so they only permit passage of large molecules such as DNA or polymers — anything smaller would move too quickly to be detected.

Strano and his co-authors — recent PhD recipient Chang Young Lee, graduate student Wonjoon Choi and postdoctoral associate Jae-Hee Han — built their new nanochannel by growing a nanotube across a one-centimeter-by-one-centimeter plate, connecting two water reservoirs. Each reservoir contains an electrode, one positive and one negative. Because electricity can flow only if protons — positively charged , which make up the electric current — can travel from one electrode to the other, the researchers can easily determine whether  are traveling through the nanotube.

September 7, 2010

Low cost desalination for potable water

Via KurzweilAI.net — A theoretical device from the recently concluded Singularity University. This sounds like a fresh water solution with real promise.

From the first link:

Our approach leverages advances in 3 exponentially growing fields: synthetic biology, nanotechnology, and solar energy.  Synthetic biology is a factor because synthetic molecules are currently being developed that can create ionic bonds with sodium and chloride molecules, enabling fresh water to pass through a nanofilter using only the pressure of the water above the pipe.

Nanotechnology is relevant for reverse osmosis, because using thinner filter further reduces the amount of pressure required to separate fresh water from salt water. A filtration cube measuring 165mm (6.5 inches) per side could produce 100,000 gallons of purified water per day at 1 psi. Finally, as advances in solar energy improve the efficiency of  photovoltaics, the throughput of solar pumps will increase significantly, enabling more efficient movement and storage of fresh water.

Although the individual components described above have not advanced to a point where the solution is possible at present, we were able to speak with leading experts in each of these areas as to the timeline for these capabilities to be realized.

Synthetic molecules capable of bonding with sodium and chloride molecules have already been created, but have not yet been converted to an appropriate form for storage, such as a cartridge. This is expected to occur in the next 2-3 years. Filters are currently in the 10-15nm range, and are expected to reach 1nm over the next 3-5 years. As with the synthetic molecules, 1nm tubes have been built; just not assembled into a filter at this point. Photovoltaics are currently approximately 12% efficient, but it is anticipated that 20% efficiency is achievable in the next 5 years.

A possible implementation of our Naishio solution. The pressure from the water volume is sufficient to propel fresh water across the membrane (A), and photovoltaics (D) generate all the energy needed to pump water from the repository (C) to the water tank and circulator (E). Sensors (B) communicate between the solar pump and membrane to regulate the water level and ensure it doesn’t become contaminated. (Image: Sarah Jane Pell).