Heliotactic Press

Interdisciplinary exploration of solar energy conversion, photovoltaics, and integrative design, and scientific philosophy.

On a road to somewhere! 2007/08/18

Filed under: environmentally aware materials science,Penn State,photovoltaics,solar cells — nanomech @ 16:03

Greetings all. My delay in contributing to these posts was for a very good reason. After many years of graduate school, and after experiencing the transient life of a postdoc, moving from Wisconsin to France and then back to Wisconsin for positions as a research scientist, I believe I will be staying put for a while.

We’re in the process of relocating the whole family to State College, Pennsylvania for my new position as an assistant professor at Penn State, in the Department of Energy and Mineral Engineering. I will be pursuing my dream of environmentally aware materials science in the pursuit of new photovoltaic devices. I admit, I’m excited and terribly nervous at the same time. I plan to work hard and make progress in my research, and in extending my network of connections with academia, government, and industry. I also really want to be a good mentor to both undergraduates and graduate students. So much of this, you just have to do it rather than make the perfect plan. The system is dynamic and fun, and more like surfing than following a recipe.

So wish me luck, and keep an eye out for new posts from the bench of the new nanomech professor!

 

Are you Sustainable? 2007/03/31

Filed under: American Chemical Society,environmentally aware materials science,indium,photovoltaics,solar cells,sustainability,third generation — nanomech @ 03:51

The looming question of sustainable practices in chemistry and materials was a central topic at the American Chemical Society this week in Chicago. There were several symposia related to chemical education of sustainability, sustainability in water resources, and (my particular favorite): sustainability and energy. The 2007 ACS president, Dr. Katie Hunt, has made sustainability one of her core issues, and you can hear (or read) all about her in this interview on Science and Society.

Prof. Art Nozik of Center for Basic Sciences at the National Renewable Energy Laboratory (NREL) arranged a top notch session on Realizing the Full Potential of Solar Energy Conversion through Basic Research in Chemistry and Biochemistry on Tuesday (Mar. 26, 2007), with speakers Nathan Lewis, Michael Graetzel (of the dye-sensitized solar cell), A. Paul Alivisatos, and A. Nozik himself (speaking on quantum dots and multiple exciton generation from high energy photons). Prof. Nathan Lewis has presented this data to President Clinton in the past, and his talk on alternative energy was shocking, alarming, and invigorating all at once. In short, the only source of power that we have enough supply for is : solar. We don’t have enough wind, wave, geothermal, nuclear, biomass, etc. in our resources to cut our CO2 levels and to create enough energy for only 2x the amount required to feed every human by 2050. You can find a link for the talk here.

Michael Graetzel’s talk was very interesting, and I’m delighted to hear progress has been made on dye stabiliy in UV, and new electrolytes have been developed using ionic liquids that remove the sealing problem encountered in acetonitrile-based electrolytes. In Graetzel’s words, dye-sensitized cells can be made now to withstand a 20 year life cycle (estimated), and have maximum performaces at 11% efficiency. Not too bad for an inexpensive alternative!

In addition, we were treated to a wonderful movie produced by Nobel Laureate Walter Kohn (UCSB) called The Power of the Sun. The short film is narrated by John Cleese, and can be obtained for only $10 from the University of California Santa Barbara website. The package includes an educational film for students as well. This film would be appropriate for high school science classes through college or university, and could be a very useful as an educational tool. It could be combined in an educational section on energy, or solar power, and the website has additional supplemental educational materials online.

I was disappointed in most of the other talks outside of the sustainablity symposia. Often the researcher/presenter did not gear the presentation toward a more general science audience. Hence, the context of the study was lost to the outside listener, and the importance that a study may have to a peripheral research topic.

For all of the hot talk about the importance of solar energy and the importance of third generation PV technologies, almost no mention was given of studying the interface between quantum dots and the electron/hole collectors necessary for doing work as a third generation photovoltaic cell. Considering that the interface is where the electron transfer occurs (aka: “chemistry”), I was quite surprised at the vacancy in that subsection of research.

The elephants of new PV technology were also in the room: the toxic heavy metal cadmium used in new solar materials (CdSe, CdS, CdTe by A. Paul Alivisatos), and the proposed superiority of CIGS (copper indium gallium selenide) PV cells, despite the very relevant indium shortages from limited supplies and competitive markets in flat panel displays. I felt these topics were not properly addressed, or maybe the main scientists are just not aware of the environmental implications of their research. We should present these materials issues to international audiences such as the ACS conference–as they are being developed–to create an environmental and ecological awareness of the most probable impact of our materials research should they be implemented on a national or global scale.

However, the meeting was indeed a recharging event for me. I left with a lot of positive momentum from the discussions on sustainability and the surrounding research that photovoltaic solar cell materials research. Most definitely PV is a strong route of scientific pursuit, and has many opportunities for new lines of research. If Prof. Nathan Lewis is correct, it will become one of the largest industries of our generation, and we should need a considerable amount of minds working toward sustainable solutions.

 

Environmental Chemistry in Review 2007/03/04

Filed under: Chemical Reviews,environmental chemistry,environmentally aware materials science,solar cells — nanomech @ 19:30

I was recently reading a the introductory statements in an older issue of the American Chemical Society’s journal Chemical Reviews. The issue was devoted to Environmental Chemistry, and the guest editor was Prof. István T. Horváth, currently a professor at the Institute of Chemistry at Eötvös University, in Budapest, Hungary (formerly a senior staff chemist at the Exxon Research and Engineering Company). I admit, I was originally looking for an article on dye-sensitized solar cells, but this introduction has an outstanding comment on ethical behavior in materials development. Something to mull over:

*Introduction: Chemists should be aware of the environmental implication of their chemistry.

“I hope that dedicating an issue of Chemical Reviews to environmental chemistry will increase environmental awareness among chemists. For example, it is no longer sufficient to make “marvelous” new molecules solely on the basis of their marketable properties. Although marketability is an appropriate goal, we, as scientists, must also be concerned with our creations’ potentials for environmental impact. At the same time, we should constantly tighten our scientific standards for generating experimental data, so that any conclusions drawn from such are and will be unambiguous …

It is in our interest, indeed, in the interest of all of society, to remain vigilant to the impacts of chemicals on the environment. We would strive to keep environmentally acceptable processes alive and minimize our activities that involve unmanageable environmental risks.“

I find it interesting that over 10 years after his comments, we are only beginning to realize the huge environmental influence that chemists and materials scientists hold in their hands when they introduce ”marvelous“ new materials (including photocatalytic nanoparticles, quantum well lasers, ultracapacitors, and carbon nanotubes). Once a material is introduced and developed on a global scale, the waste component arises for material disposal, followed by issues of materials fate in the environment. As scientists and engineers, we have a responsibility to remain aware of the global environment when we make new materials for society.

*From Chemical Reviews, 1995 (95)1, pg. 1

 

Environmental Technology: What is it? 2006/08/12

Filed under: environmentally aware materials science — nanomech @ 03:01

I pursue my research interests in solar cells because I find that science is always more interesting at the interface of things (both literally and figuratively). The juxtaposition of materials development, earth science and environmental awareness is termed environmental technology. Because I have developed the building blocks from my multidisciplinary background into unique tools to fuel the opening field of environmental technology, I believe I am well positioned to have a little discussion about the subject.

My research deals with new designs and materials for non-silicon solar cells, and my background is that of a non-traditional environmental chemist and mineralogist (geoscientist). How is it that I find myself extending my education to non-traditional applications? One could say that both geology and environmental chemistry are already interdisciplinary fields of study, and to add another layer of interest only makes the process more interesting. However, the overlay of that additional element may act as a lens to help to focus a field onto those areas that are significantly helpful to mankind and those which may also stimulate the new post-fossil fuel economy. Yes, I believe there are ethical and financial incentives for pursuing environmental technology. But what is it?

Environmental technology is a subfield of research in environmental science concerned with topics of sustainable development in terms of energy, water quality, air quality, and waste treatment. Environmental technology is not necessarily a new topic, but I would have to say it has not yet come into its “own” in the larger umbrellas of environmental science or civil and environmental engineering. Past research in environmental technology has been strongly related to water remediation and waste treatment, and hence has had a close association with civil and environmental engineering. Currently, research has included alternative energy materials development, such as ultracapacitors, inorganic fuel cell membranes, and yes even solar cell development.

There is also a development to fold in the principles of green chemistry developed by chemists (largely organic), with the environmental technology goal of sustainable chemical development “upstream”. The metaphor being a river in which any waste products are minimized and with the goal of environmental premediation (including the 12 Principles of Green Chemistry*). Normally, waste is simply released into the river or sewer system and subsequently remediated, or treated after the fact, “downstream” from the point source of pollution. This goal of materials premediation will require new technologies that adapt learning from the earth sciences and environmental sciences for the common goal of sustainable resource development and low enviromental impact.

I have mixed scientific disciplines before and found that it can reveal amazing new discoveries. For example, if you overlay interests in geochemistry and mineralogy with genetics and microbiology, you have a curious field called geomicrobiology, where scientists have found fascinating results about microbial influences on the chemistry of mines, their survival near toxic “black smokers” in the ocean, and their influence on arsenic removal from groundwater by precipitating nanoparticles. In a similar fashion, if you combine interests in materials science with environmental chemistry and earth science, you have a burgeoning field called environmental technology with much potential for the new science economy.

Note: links of interest and examples of Environmental Technology

* The 12 Principles of Green Chemistry were first published by Paul Anastas and John Warner in Green Chemistry: Theory and Practice (Oxford University Press: New York) 1998.

 

Case Study: Indium and Tin 2006/06/17

Filed under: environmentally aware materials science,indium,ITO,tin — nanomech @ 06:38

Where does any raw material come from? Meaning, where on the surface of this planet can we find an ore body to mine? Once you know where a ore body is, how much can you take out of the earth and still have the product be economically viable (considering clean-as-you go mining)? Once you get a metal ore out of the ground (you must dig a mine), think about how it is processed and refined, and then think of the environmental impact of the purified substance once it has been liberated and refined from the raw ore. What do you do with the raw material when you have it? What happens to the the purified material/chemical when you don’t want it any more? How much energy is required to recycle it? What is the fate of the material when you release it back into the environment? This is a cradle-to-grave study, and is a core principle in environmentally aware materials science.

We don’t need to just think in an abstract way about the global ore reserves of a mineral or element, there are information resources on-line at our web fingertips via the USGS (United States Geological Survey). As an aside, I truly enjoy the transparency of operation, open access to information, and the hands-on attitude of the USGS. Sure, it may be a bloated government operation, but it’s one that probably does far more positive action for the improved quality of life of Americans than several other, more aggressive modern mega-gov-departments.

One of the sub-disciplines is in geology is economic geology. An economic geologist is responsible to find an ore body (using scientific principles of ore formation); estimate the size, purity (for valued minerals), and accessibility of the ore body via prospecting (drilling, satellite imagery, GIS global positioning information, and a battery of geophysical tests); and then report the findings and estimates to the public or to an interested private company. In our case, the USGS has done this sort of work for the public and reported annual estimates of major minerals of interest. If you visit the Commodity Statistics and Information page, you’ll find a virtual treasure trove (literally and figuratively) of information on mined materials on a global scale.

As two examples, I will use the elements “Indium” that is used in ITO (Indium Tin Oxide), and “Tin” used in ITO and fluorine-doped tin oxide (FTO, or SnO2:F). Both are used with Transparent Conductive Oxides (TCOs) that are popular right now for the LCD industry, and some use is being channelled to new solar cell designs.

If I look down the USGS list to find Indium, I see a whole host of information summarized just in the introduction. Wow, that’s great! We need to mine zinc sulfide ore to get indium, so in order to get more indium there needs to be more demand for zinc. But wait, there’s more! In the Indium 2006 Mineral Commodities Summary we get access to a full PDF of data. What do we find out? Well, indium use grew by 15% from 2004 to 2005, we don’t have any of our own on reserve (stockpile), and we import the majority of our indium from China, Canada, and Japan (from highest to lowest). Also, only 15% of all ITO goes into actual products. Due to difficulties, length of processing, and high costs, the rest of the unused ITO is scrapped and not recycled at all.

OK, now compare Indium to the element found in TCOs, Tin. Fluorine-doped tin oxide (SnO2:F) has many of the same uses as ITO, but costs less and is often more useful in solar cell research (because indium tends to diffuse into the light absorbing materials with thermal annealing). In the Tin 2006 Mineral Commodities Summary, we again get some juicy information. We see that, again, we don’t mine tin much at all inside the US, but the countries that we do import it from are much more diversified. The applications of tin itself are much more diversified, and it is not nearly the trace metal resource that indium is (right up there with silver). While tin is not an abundant element, we do have tin stockpiled, and tin recycling is around 61% as of 2005. No words about SnO2:F recycling, though–my suspicion is that it is just as difficult to recycle as ITO thin films.

Which of the two would you choose to work with?

I will make one additional note on the environmental impact of both of these materials in their oxide state as thin films. Both tin oxide and indium oxide are pretty stable at Earth’s surface, relatively inert (they don’t dissolve easily), and have not been found to cause dramatic toxicity problems as oxides. Given the small amount of information at hand regarding toxicity, if you don’t recycle either of these, you are unlikely to significantly alter the environment at the waste repository. So it’s more a choice of economics and reserve materials at the moment. Phew, at least something that we make for new technologies is useful and not horribly toxic!

But you know what? Sometimes even oxides are altered, and then there may be a toxicity risk in the dissolved species. This is the true weak spot in the case study, where we assume the small amount of research on tin oxide and indium oxide is sufficient to assure environmental fate. Once upon a time, not so long ago, in a county not far from your home, scientists perceived PCBs (polychlorinated biphenyls, used as electrical insulators, liquid coolants, and fire retardants) as “safe” (on the basis of a small amount of information). They are quite inert and not many people had researched their toxicity, until after they were widely distributed in our everyday technologies–and then it became apparent that things were not so safe with PCBs. In the organic chemistry laboratories, you also tended to wash your hands with benzene then, but that’s another story.

In environmental materials science, we need to know the extremes at which our materials break down, and if those conditions exist in the outside environment. Research on the chemical stability of these films, and the fate of dissolved tin and indium species would be handy information. A classic euphemism in materials science was make it, then break it. This used to be used for building materials like cement, steel, aluminum alloys, and brass. We now need to adapt it to a new wave of materials science that also includes molecular compounds and nanoparticles and thin films.

 

Environmentally Aware Materials Science 2006/06/17

Filed under: environmentally aware materials science — nanomech @ 06:36

Form and Function have new roles in materials science when viewed through different watch glasses. Environmental consistency or awareness is one of those lenses through which I inspect those roles. Is improved Function (e.g. a new “wow” compound or nanostructure) worth application if the materials used disruptively change the outdoor environment and human/animal physiology? Is better Form (on the small scale a core element or molecule, or on the large scale a wind or solar station) worthy of development if the supplier cannot meet demand for a growing industry?

Let’s view the materials in advanced photovoltaic design from an environmental perspective. Not necessarily as a pejorative concept of “bad for the environment”, so before passing this post off as a tree hugger’s celebration, read on. The environment is more than an idealistic biological greenspace–it is also the raw minerals from the crust that drive our technologies, the water we cannot live without and the air that we breath. With all our metals and semiconductors used in industry, one must “dig up” the raw ore, then separate the ore into constituents, and finally refine the element or salt before research and industry can use it and convert it into a specific chemical compound. This takes energy, land space, water, and green space. But if you want your next i-pod, blackberry, laptop, television, hybrid car, electric car, solar cell, or wind farm; you need to dig into the dirt to get the materials to make them function with such an appealing form. As a formally trained geologist and an environmental materials scientist (and the grandson of a mining engineer), these reflections are smack in the middle of my think-space. As such, I am constantly reminded of the links tying technologies to geology and environmental chemistry.

I encourage all materials researchers to use tools of environmental awareness to assess the practicality of going down each road of materials research. If the impact of our research is a global technology that everyone will want–can everyone get access to the materials to produce it, or will it be a short term solution that will be isolated to the very rich? Will the use of that material require an energy intensive processing? What will the emissions be from refining, and how easily is the product recycled? Finally, what is the fate of the material when it is reintroduced into the environment in a waste repository, and what is the toxicity of the altered chemicals in the environment. This is termed a cradle-to-grave perspective, and while I don’t really enjoy the anthropomorphic connotation, it is a fairly new concept to advanced materials research.

Summary
Consider a material used for technology. The following factors are valid in a global economy of technological development:
1. Raw resources (local or imported)
2. Energy use from refining
3. Gas and particulate emissions from refining
4. Recyclable?
5. Energy use from recycling
6. Toxicity
7. Fate of the material as it is exposed to the environment

 

Why should an environmental scientist be performing materials development? 2006/03/04

Filed under: environmentally aware materials science — nanomech @ 08:02

Environmental science is fairly well devoted to sampling from natural open systems (rivers, lakes, mines, groundwaters, and air), characterizing the samples by various analytical methods, and applying the data towards aiding local, state and federal policy changes in environmental regulation. There may be a way to expand the influence of environmental science into practical applications and new technologies. Perhaps we can change the source of the pollutants by working directly with the materials scientists and chemists responsible for generating new technologies. I feel there is a niche for environmental scientists to merge with the materials sector and help guide the development of materials that may have a minimum impact on the environment. This builds upon my philosophy of environmental premediation, where the environmental scientist actively pursues materials research with the goal of establishing a link between environmental awareness and engineering new technologies.

This shift would be analogous to the changes that mining industry took in the USA and Canada during the past century. Mining engineers communicated directly with geoscientists to find out what steps could be taken (e.g. microbial bioremediation, clay linings for tailing ponds, and replanting trees and brush) to minimize harsh impacts of cyanide disposal, surface water acidification, and erosion run-off that contaminated drinking waters and destroyed local ecologies. Note: these steps were performed in order to avoid heavy fines when the mines closed down, so the people who influence policy change do have a critical complementary role. The industrial policy of “clean as you go” was developed to minimize costs, which had the added benefit of greatly reducing the impact of mining on North American locales. Mining is never a happy shiny green experience, but it is distinctly better than 100 years ago, because of the communication between environmentally aware scientists and savvy materials engineers.

From my own experience as a materials researcher in an environmental chemistry program, I am very conscious of the residues of past materials developments, and how they impact our natural water resources. An excellent example of these impacts can be seen in the successful synthesis of high dielectric, flame retardant materials such as PCBs (polychlorinated biphenyls) that contaminated our water sheds in the past generation, inducing problems with immune, endocrine, neurological and reproductive systems as well as being carcinogenic; only to be replaced by the successive generation of chemically similar PBDEs (polybrominated diphenyl ethers) in computer devices and flame retardant furniture. One of the impacts of this type of materials development, one without an equal awareness of materials fate, is huge economic loss from clean-up fees, or corporate and personal taxation for land maintenance. Materials development cannot be pursued without ecological awareness, and environmental science programs can set an excellent core value for green materials engineering. Developing a strong awareness of the fate of materials and a strategy for creating alternatives (direct lines of communication between the developers and those whose monitor the ramifications of those developments) are key elements to be taught to the future students of materials science.

Clean accessible water, easily accessed energy, and a multitude of energy storage systems will drive future markets. I project that green technologies, motivated by environmental premediation (the focus of designing technologies that minimize our footprint on the environment) will be the impetuses for the next wave of materials development.

 

 
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