Demonstration of highly efficient solar water distillation system
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Comment from academist staff
Toward practical application of highly efficient sunlight-driven water evaporating material
miho otsuka
Maximize the utilization of solar energy
The sun is the most familiar renewable energy source. Among the various approaches, photovoltaic cell is the most popular and wide-spread method to convert sunlight to energy for human. Photovoltaic cells can be found in number of places from small-scale to large-scale applications; for instance, they have been used in wristwatches and houses.
The conversion efficiency is a critical factor to generate energy from the sun. Commercial photovoltaic cells have the light-to-electricity conversion efficiency around 10-20 %.
In stark contrast, the light-to-heat conversion efficiency is known to be higher than those of photovoltaic cells. We have recently demonstrated that TiN nanoparticles have light-to-heat conversion efficiencies above 90 %. Moreover, they are suited to quickly evaporate water by locally heating water only around them. Having this result, we think of using them to distill sea water with high efficiency.
Combining titanium nitride nanoparticles and ceramic wools for highly efficient sunlight driven water evaporation
Although water in pond or sea naturally evaporates, typically vapor is not visible. This is because in a natural process, the evaporation efficiency is low. However, when our composite material is under focused artificial sunlight, vapor is visible even at room temperature. The important factors behind our samples are high sunlight absorption efficiency and local heat transfer from the TiN nanoparticles to water by suppressing the heat dissipation.
In our study, we chose TiN nanoparticles as highly efficient sunlight absorbers. The average size of our TiN nanoparticles are 50 nanometer on average, which is around one thousand times smaller than the diameter of hair in terms of size. While the bulk color of TiN is quite similar to that of gold, TiN nanoparticles look black. Actually, they are “darker” than black! What we mean here is that TiN nanoparticles have even higher sunlight absorption efficiency that black nanoparticles which are conventionally considered as good sunlight absorbers. The reason for the high sunlight absorption of TiN nanoparticles are due to their optical resonances, termed as surface plasmon resonances. Different from other nanoparticles that can excite surface plasmon resonances, the surface plasmon resonances of TiN nanoparticles are broad enough to cover the majority of solar spectrum.
In addition, we developed a composite material by chemically bonding TiN nanoparticles on ceramic wool which looks like cotton. When this composite is floating on water, the ceramic wool sucks water by the capillary actions so that only the surface of TiN nanoparticles get wet and minimize the heating of surrounding water. With this rational design, the conversion efficiency from sunlight to vapor has become around 50 %.
Toward cost-effective sea water desalination system
There are number of places in the world where access to clean water is limited and the only source of water is sea. Sea water can be desalinated by, for instance, reverse osmosis system, however, it consumes huge electrical power and is expensive. Moreover, it is not suited for small-scale water desalination.
In contrast, our composite material is simple and cost-effective, which makes it suitable for personal usage. It contains only abundant metallic elements; titanium and aluminum. These features make our composite material practically attractive.
Nevertheless, so far we have perform our experiment with an artificial sunlight; it is basically an intense lamp having a spectrum similar to sunlight. Since we have been working in the lab, the sample sizes were typically a few centimeters. For future practical applications, we think it is inevitable to do experiment outside under the sun with larger amount of samples. It is also necessary to design something like a roof to collect vapor to have distilled water without blocking incoming sunlight.
Fundraising
As mentioned above, we would like to demonstrate solar water evaporation under the sun using our composite materials. For this purpose, we are planning to fabricate the sample to cover nearly 1 m² area and build a setup to keep the vapor and collect distilled water. In the outside experiment, we plan to distill sea water and make sure that the collected water is clean and drinkable. The donations raised by this crowd funding will be used to fabricate composite material and build a setup to collect distilled water. We very much appreciate your kind donations to support our project.
Profile
石井智、Manpreet Kaur
Project timeline
| Date | Plans |
|---|---|
| Dec 2018 | Start fundraising |
| Jan 2019 | Sample fabrication |
| Feb-Apr 2019 |
Design and built a setup to collect vapor
|
| May 2019 | Water distillation experiment outside |
| Jun-Jul 2019 | Improve the system design by based on the initial results |
| Aug-Sep 2019 | Outside experiment (second round) |
| 2019年9月 | 研究のまとめ |
Pledge Rewards
Research report of the project will be sent.
Research report (PDF)
32 supporters are supporting with this reward. （No quantity limit）
Acknowledgement of the donators’ name in the presentation materials at academic conferences.
Acknowledgement in academic conferences / Research report (PDF)
11 supporters are supporting with this reward. （No quantity limit）
Invitation to a private seminar (science cafe) where we present our project outcome. Transportation expenses are not included.
Invitation to a private seminar (science cafe) / Acknowledgement in academic conferences / Research report (PDF)
9 supporters are supporting with this reward. （No quantity limit）
A small amount sample that we used in our project will be shipped to you. You can see water evaporation if you focus sunlight to the sample. Please note that this reward is shipped to those who have addresses in Japan.
Sample / Invitation to a private seminar (science cafe) / Acknowledgement in academic conferences / Research report (PDF)
8 supporters are supporting with this reward. （No quantity limit）
Acknowledgement of the donators’ name in the academic journal if our work is accepted.
Acknowledgement in academic journal / Sample / Invitation to a private seminar (science cafe) / Acknowledgement in academic conferences / Research report (PDF)
0 supporters are supporting with this reward. （No quantity limit）
Invitation to a lab tour at our institute in Tsukuba, Japan. Transportation expenses are not included.
Invitation to a lab tour / Acknowledgement in academic journal / Sample / Invitation to a private seminar (science cafe) / Acknowledgement in academic conferences / Research report (PDF)
2 supporters are supporting with this reward. （No quantity limit）
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Research report (PDF)
32
supporters
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Acknowledgement in academic conferences and others
11
supporters
back
（No quantity limit）
Invitation to a private seminar (science cafe) and others
9
supporters
back
（No quantity limit）
Sample and others
8
supporters
back
（No quantity limit）
Acknowledgement in academic journal and others
0
supporters
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（No quantity limit）
Invitation to a lab tour and others
2
supporters
back
（No quantity limit）
