I'm assuming that you have read my previous blog entries and know what I'm up to these days. For the uninitiated, I'm currently working on a research project (over the summer) at the National Chemical Laboratory (NCL) in Pune, India. My project is focused on a technology that was initially advanced by a team at Rice University (Texas, USA) - a novel method for efficient steam generation using solar energy and a nanoparticle solution.
When I first started my work here at NCL, my primary task was to sift through prior art and literature to try and understand the fundamentals of the project. This involved my reading and referring to papers written by various researchers on this topic and associated ones, some back-of-the-envelope calculations and discussions with my mentors as we left the firm ground of facts and journeyed into the murky waters of predictions and untested hypotheses.
The phenomenon basically relies on the concept of Localised Surface Plasmon Resonance of the nanoparticles, which is the collective oscillation of electrons on the surface of the particles. It occurs when the frequency of the incident light (electromagnetic radiation) matches the natural frequency of the surface electrons. When sunlight is focused onto the nanoparticle solution, plasmon resonance causes the nanoparticles to be heated up to extremely high temperatures in a very short span of time. This results in the instantaneous evaporation of a thin layer of water around the nanoparticle, forming a steam "nanobubble" with the particle as the nucleus. The low thermal conductivity of steam prevents the transfer of heat into the surrounding solution (this is also due to a fascinating phenomenon called the Leidenfrost Effect, and various thermal barrier mechanisms like Kapitza Resistance, which I shall not elaborate upon for simplicity's sake). Thus, the water does not get heated up in bulk to a significant extent. Herein lies the remarkable energy-efficiency of the process: most of the incident solar energy is utilised in steam formation, and not in the actual heating of the water. Steam is created without actually heating up the water to its boiling point! (The team at Rice demonstrated this very effectively by creating steam from ice-cold water within seconds.)
Anyway, the steam nanobubble, being considerably less dense than water, is quite buoyant, and rises to the surface of the solution. There, the bubble pops, releasing the steam into the atmosphere (or a collection chamber) and the nanoparticle falls back into the solution (in theory). That is another specialty of the phenomenon - its recyclability. However, that is something that I still have to test during the course of my work.
So, extrapolate this to billions of nanoparticles in a 50mL volume of solution and you have a very powerful technology indeed! If properly developed, this phenomenon can be applied to steam generation in resource-poor locations, as it runs entirely on solar power. And since steam is one of the most important industrial fluids, the applications of this technology are potentially limitless!
After many discussion meetings with my supervisors and browsing through innumerable papers online, I finally had an understanding of the phenomenon. We (my mentors and I) felt pretty confident that we might be able to develop it, and my next goal was to try and reproduce the experiments carried out by the research team at Rice University. And that is what I am currently working on.
Since it is currently the monsoon (rainy) season in India, the skies are overcast pretty much all of the time, and chances of obtaining strong sunlight are as high as that of a proton having a negative charge! Consequently, I will be utilising a solar light simulator for my experiments, a piece of equipment that replicates both the intensity and the exact spectrum of the midday sun.
The nanoparticles used by the team at Rice were a unique type of "nanoshells" - particles composed of a silica core and a gold shell. In an attempt to try and reduce the cost of the technology and to simplify the initial trials, I am going to be conducting the initial tests with a dispersion of simple gold nanoparticles in water. These I have already synthesised and characterised, and are ready for use.
The one aspect of preparing for my upcoming experiment that was most intellectually stimulating was designing the glassware setup. Since I would be using sensors to measure the pressure of the generated steam and to measure the temperature of the steam and the nanoparticle solution, the glassware would have had to be customised. And so it was.
Planning the design of the glassware was an interesting experience, as I had to think through all the possible scenarios and anticipate problems. Coordinating with my mentors and the glassblower, I managed to hit upon an apt design, which I gave to the glassblower to manufacture.
When I went over to the glassblowing workshop to place my order, it was as if I was Alice and had fallen down the rabbit hole! Glassblowing was a skill that I had previously never given much thought, and I was forced to change my opinions in spectacular fashion. It was as if the glass itself was in tune with the thoughts of the blower! He was an artist, but instead of paintings, sculptures or symphonies, his masterpieces were retorts, condensers and burettes, and they took form amidst the heat of his blowtorch and his fine touch. I had to undergo a painful internal struggle in order to extricate myself from the workshop and return to my work.
Designing the experiment has been a great learning experience, and I can't wait to get started with the actual trials. I finally began to appreciate all the subtleties and thought processes behind experimental science, and I am thoroughly enjoying thinking and working like a scientist, skills that I hope to apply to whatever I do in the future. In a few days the glassware should be ready, and I shall be able to finally see whether my design works or not. While the result does matter a lot, the journey itself has been totally worth it.
Expect to see many more posts on my ongoing work here at NCL!
When I first started my work here at NCL, my primary task was to sift through prior art and literature to try and understand the fundamentals of the project. This involved my reading and referring to papers written by various researchers on this topic and associated ones, some back-of-the-envelope calculations and discussions with my mentors as we left the firm ground of facts and journeyed into the murky waters of predictions and untested hypotheses.
The phenomenon basically relies on the concept of Localised Surface Plasmon Resonance of the nanoparticles, which is the collective oscillation of electrons on the surface of the particles. It occurs when the frequency of the incident light (electromagnetic radiation) matches the natural frequency of the surface electrons. When sunlight is focused onto the nanoparticle solution, plasmon resonance causes the nanoparticles to be heated up to extremely high temperatures in a very short span of time. This results in the instantaneous evaporation of a thin layer of water around the nanoparticle, forming a steam "nanobubble" with the particle as the nucleus. The low thermal conductivity of steam prevents the transfer of heat into the surrounding solution (this is also due to a fascinating phenomenon called the Leidenfrost Effect, and various thermal barrier mechanisms like Kapitza Resistance, which I shall not elaborate upon for simplicity's sake). Thus, the water does not get heated up in bulk to a significant extent. Herein lies the remarkable energy-efficiency of the process: most of the incident solar energy is utilised in steam formation, and not in the actual heating of the water. Steam is created without actually heating up the water to its boiling point! (The team at Rice demonstrated this very effectively by creating steam from ice-cold water within seconds.)
Anyway, the steam nanobubble, being considerably less dense than water, is quite buoyant, and rises to the surface of the solution. There, the bubble pops, releasing the steam into the atmosphere (or a collection chamber) and the nanoparticle falls back into the solution (in theory). That is another specialty of the phenomenon - its recyclability. However, that is something that I still have to test during the course of my work.
So, extrapolate this to billions of nanoparticles in a 50mL volume of solution and you have a very powerful technology indeed! If properly developed, this phenomenon can be applied to steam generation in resource-poor locations, as it runs entirely on solar power. And since steam is one of the most important industrial fluids, the applications of this technology are potentially limitless!
After many discussion meetings with my supervisors and browsing through innumerable papers online, I finally had an understanding of the phenomenon. We (my mentors and I) felt pretty confident that we might be able to develop it, and my next goal was to try and reproduce the experiments carried out by the research team at Rice University. And that is what I am currently working on.
Since it is currently the monsoon (rainy) season in India, the skies are overcast pretty much all of the time, and chances of obtaining strong sunlight are as high as that of a proton having a negative charge! Consequently, I will be utilising a solar light simulator for my experiments, a piece of equipment that replicates both the intensity and the exact spectrum of the midday sun.
The nanoparticles used by the team at Rice were a unique type of "nanoshells" - particles composed of a silica core and a gold shell. In an attempt to try and reduce the cost of the technology and to simplify the initial trials, I am going to be conducting the initial tests with a dispersion of simple gold nanoparticles in water. These I have already synthesised and characterised, and are ready for use.
 |
| The dispersion of Gold nanoparticles in water (also called a Gold colloid) that i synthesised for my experiments. |
The one aspect of preparing for my upcoming experiment that was most intellectually stimulating was designing the glassware setup. Since I would be using sensors to measure the pressure of the generated steam and to measure the temperature of the steam and the nanoparticle solution, the glassware would have had to be customised. And so it was.
Planning the design of the glassware was an interesting experience, as I had to think through all the possible scenarios and anticipate problems. Coordinating with my mentors and the glassblower, I managed to hit upon an apt design, which I gave to the glassblower to manufacture.
When I went over to the glassblowing workshop to place my order, it was as if I was Alice and had fallen down the rabbit hole! Glassblowing was a skill that I had previously never given much thought, and I was forced to change my opinions in spectacular fashion. It was as if the glass itself was in tune with the thoughts of the blower! He was an artist, but instead of paintings, sculptures or symphonies, his masterpieces were retorts, condensers and burettes, and they took form amidst the heat of his blowtorch and his fine touch. I had to undergo a painful internal struggle in order to extricate myself from the workshop and return to my work.
Designing the experiment has been a great learning experience, and I can't wait to get started with the actual trials. I finally began to appreciate all the subtleties and thought processes behind experimental science, and I am thoroughly enjoying thinking and working like a scientist, skills that I hope to apply to whatever I do in the future. In a few days the glassware should be ready, and I shall be able to finally see whether my design works or not. While the result does matter a lot, the journey itself has been totally worth it.
Expect to see many more posts on my ongoing work here at NCL!
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