So, you're a grad(uate) student. How is that different from being an undergraduate student (college student)?

Good question! The graduate student's day changes significantly depending on how far into a graduate program the student is. When you start graduate school, you must take some classes, but you generally devote significant amounts of time to research, as well. By the end of graduate school, you are just doing research. Research is your focus. While graduate students have a lot of time flexibility (who doesn't like sleeping in but running experiments at midnight?), they often don't have time for the clubs that are found everywhere during undergrad. Graduate students are also given many more responsibilities (laboratory keys, the ability to run their own experiments, design research plans, etc.). Since you don't have assignments with clear deadlines, work is very self-directed and you have to keep yourself on track. You are your own researcher. PhD comics sometimes makes you cringe with how true to life it is.

How do scientists from around the world collaborate? What do these collaborations look like?

Excellent question! Every collaboration is different. In our collaboration, we have bi-weekly meetings in which we bring up any issues that we are having. While we aren't all physically in a single location, we talk and present over the internet using conferencing software. At each meeting, a different sub-group presents. During these presentations, other group members will ask questions and offer suggestions for improving work and making heads or tails of confusing data. In our research group, too, we have weekly group meetings where we talk about what is going on in the lab and group members also present both on things that they are working on and things that might be interesting to the group (such as new or relevant research reports). For some collaborations, researchers will travel to physically meet with each other and discuss research. This is how many collaborations are born.

An important part of being a researcher is presenting work at conferences. At conferences, people come in often from all over the world to talk about their work and learn about what other researchers are doing.

I hear about silicon solar cells, but I have also heard mention of CdTe cells. I know that you work on CZTS and I've also heard mention of a crazy thing called CIGS. What does all this mean?

These different labels for cells refer to the material that makes up the absorber layer. CdTe, Si, Cu2ZnSn(S,Se)4 (CZTSSe), and Cu(In, Ga)Se2 (CIGS) are all materials that can be used in a specific layer of a solar cell (something used to convert energy from the sun into electricity) in which light is absorbed and the energy in that light converted into charge carriers (electrons and what are known as holes). There are a variety of solar technologies commercially available and a single technology may not immediately dominate. CdTe-based cells have been less expensive than other types recently, however there are scarcity concerns about this technology that will eventually limit the extent to which cost can be lowered. Si cells are pretty ubiquitous (and inexpensive), but are not quite as inexpensive as CdTe-based cells due to added processing requirements. CIGS cells are just recently coming to market. Technologies like CZTSSe have not been commercialized since they are still in the research stages (comparatively low, but rapidly improving efficiencies). A new technology on the block that may really shake things up are perovskite solar cells, which have had a meteoric rise in efficiency making them fairly comparable in terms of efficiency to CIGS and CdTe, but this technology has some major degradation issues (water, even the water vapor in air kills cells). Both CZTSSe and perovskite cells are earth-abundant and it is likely that they will be able to be made more inexpensively than competing technologies. Regardless, silicon-based cells will certainly remain in the overall mix. It is likely that, for a long time, solar cells based on several different materials systems will all compete, meanwhile enhancing our understanding of these systems.

Why solar and not other sources?

Good question! The answer may be surprising. In some locations, solar will not be the best, although it will work well in many locations. For example, it probably would not be wise to install solar modules above the arctic circle because, although you would generate energy during the summer, it is very dark during the winter and you wouldn't get much energy. It is important that solar energy be able to compete with other energy sources. Although it often takes some time and money to bring a competing technology to catch up to existing technologies, business dictates that there be some reason for the change. The new technology must be able to stand on its own two feet once subsidies go away. In some places solar energy will be the best option and in other locations it will not. Solar will likely play a significant role in upcoming years in the power grid (in both developed and developing countries), but it will likely not play a role in all places.

In terms of impact, solar energy is capable of making a big difference in the individual lives of people with little access to other energy sources. In addition to contributions to the larger grid used by those who have many resources, these smaller contributions are also valuable. It is important to consider these small-scale but large-impact contributions when going about research. Without light, it is hard for small isolated farmers not connected to the electrical grid to connect with larger communities, learn, read, and thrive. It is much more difficult to sell goods without the internet. Access to the internet, which we often take for granted, broadens horizons.

What are common things solar cells can be found on? Can solar cells charge a reusable battery?

Source: Tower Sign and Signal

Solar cells can and are used to charge reusable batteries. For example, you see this in solar cars. One of the limitations of solar photovoltaics is that they produce energy when the sun is shining and produce none without light. This could be a problem at night if you don't have any other energy sources or ways of storing the energy produced during the day. If we transitioned to mostly solar energy in the larger electric grid, this could be a problem if batteries can't store energy generated during the day for use at night.

Check out this article to find out more about it!

Solar cells are found on many things. You may be most familiar with solar calculators (the calculators that do not run out of batteries--note that, even indoors, they generate electricity since they are still receiving light, albeit not usually as bright as that seen outside). Solar cells are now used to power road signs and some traffic lights. They are also found in garden lights and other outdoor lighting. Emergency phones in remote places often also have solar cells to cut down on the cost of sending electricity to those places. You can use solar cells to charge your electronic devices. People and businesses are now starting to install solar cells on their buildings/houses in order to reduce their energy costs. Satellites also often use solar cells for power. Solar cells are found on an increasingly wide array of things!

Solar battery!

Credit: Yiying Wu, The Ohio State University

The world's first solar battery has been invented! It recharges itself using air and light.

Read more about Ohio State's research here or here!
Their work was recently published in Nature Communications entitled "Integrating a redox-coupled dye-sensitized photo electrode into a lithium-pxygen battery for photoassisted charging", DOI: 10.1038/ncomms6111.

I have heard that Germany is using a lot of solar power. I believe Germany is a relatively cloudy place, how is it that they can still generate power? Can this really be economical?

Source: NREL

It is true that Germany receives less solar energy than many regions of the United States. However, less energy does not mean no energy or that solar energy will never be competitive with other sources. Germany still receives sunlight, although not nearly as much as the southwestern U.S. One still generates energy from solar cells on cloudy days--the amount of energy generated is just reduced under such conditions. Germany is a world leader in energy production. In the 1990s, Germany initiated some policies (largely subsidies) that encouraged the construction of solar energy installations. These subsidies helped make solar energy competitive with other energy sources. These subsidies helped solar energy to make inroads and compete with other energy sources. It is yet to be determined how solar energy would fare once those subsidies are inevitably reduced or eliminated. Whenever one switches from using one technology to another, there are some upfront costs involved in that switch. These subsidies are part of that upfront cost. If the subsidies ceased to exist today, solar energy would be much less competitive, but the solar infrastructure is more of a long-term investment. A surprising amount of the cost of solar is associated with red tape.

Source: http://www.forbes.com/sites/toddwoody/2012/07/05/cut-the-price-of-solar-in-half-by-cutting-red-tape/, note that this is from 2012--I could not find more recent figures

In some regions of the U.S., solar energy is already competitive with other energy sources, just as it is in parts of Germany.

EIA Energy Kids

Check out this informative website about energy by EIA! 

EIA Energy Kids

Since power is typically transmitted as AC (alternating) current over long distances, but solar cells would seem to generate DC (direct) current, do solar farms convert the current from DC to AC first? Alternatively, if panels are installed on a house, can everything remain DC?

Photo from abb.com, original from Edward Csanyi of Electrical Engineering Portal

Solar energy must interface with existing power systems. Alternating current is used for transmission because there are fewer losses because it is very easy to transform between different voltages. Heat is dissipated when large currents heat wires, increasing their resistance. With an AC signal, currents can be kept low by transmitting high-voltage signals, decreasing losses. 

Solar cells do not produce a consistent amount of energy throughout the day. Additionally, they produce little energy at night when one often needs electricity. Consequently, the energy from the solar cell must be either stored in a battery or fed back into the grid. It is more common to feed the energy back into the grid as an AC signal due to existing payment schemes and challenges/costs and safety risks associated with storing large amounts of energy. Since these solar cells are connected to the larger power grid, the DC signal that the solar cells produce must be converted to an AC signal.

Furthermore, since many household appliances are designed to operate with an AC signal, it would not be feasible to completely remove a house from the grid and operate the building on DC energy. Already, since computers run on DC signals, you need an AC to DC converter. If one switched to all DC circuits, one would need DC to AC converters. Since most of what we have now either relies on an AC signal or has an incorporated AC to DC converter, it would be expensive to switch to DC electronics. 

I see people talking about record solar cell efficiencies, but most solar cells on the market only give 10-15 % efficiency. Why is that?

There are a lot of reasons and much of it has to do with cost. To make super efficient solar cells, you need to get rid of reflections, for example. To do this, you need to add extra anti-reflective coatings, which make you have to go through more processing steps, costing money. Furthermore, typically you are actually working with solar modules, which necessarily have lower efficiencies than the most efficient cell in them (due to, for example, empty spaces between cells or conduction losses in the cells, themselves, or wiring). For example, peak solar efficiency is obtained at the maximum power point of what is known as an I-V curve (see image below). If you put several solar cells in series in order to build up a reasonable voltage across the module (~700 mV per cell with current densities ~30 mA/cm^2), it is unlikely that the maximum power point of all these cells will line up perfectly, reducing the module efficiency.

Photo from ChemistryBlog

Already, solar cells have a decent upfront costs. Much of this cost comes from the installation of the modules and the electronics associated with controlling the module or its output. Engineering solar cells is always a balance of cost and performance and one must deal with the complexities of real-life materials and processes.

Transparent Solar Cells?

From http://spectrum.ieee.org

Can solar power go transparent? Apparently! Read more about Michigan State University's work on transparent luminescent solar concentrators here!

Why do you study solar cells?

This video presents many of the advantages of solar cells. We also study solar cells in order to better understand the materials in them, which might have other uses that are discovered later on or may exhibit behaviors similar to future materials. What is discovered about these materials may be also applicable to the other materials. New techniques are also created during this process. No one knows the future. However, by understanding a wide variety of materials, we can be better prepared to engineer solutions to future problems.

Global Experiment 2014

Since 2014 is the international year of crystallography, the
Global Experiment 2014 concerns crystal growth! The Global Experiment project is aimed at students aged between 7 and 16 years, working with their teachers to learn how to dissolve different materials, to grow crystals and to investigate the effects of changing various environmental conditions.

The Global Experiment 2014 is organized by Royal Society of Chemistry and International Union of Crystallography.

Baseball: a physics game

Baseball is a physics game. Check out this video, which discusses the physics of baseball flight, specifically, the curve ball.

Pitching physics

Fielding Physics

Go Tribe!!!

Solar Decathlon

Every second year Solar Decathlon takes place. It's an international competition presented by the U.S. Department of Energy and organized by National Renewable Energy Laboratory. The competition challenges teams to design, build and operate solar-powered houses that are cost-effective, energy-efficient and attractive. Read more and follow the preparations for the next Solar Decathlon next year here!

Coming to a seashore near you: Clean waterways using the sun!

Photo courtesy Andrew David Thaler

Check out this technology! There are at least one billion tons of plastic in the ocean. Wouldn't it be great to be able to collect this plastic before it gets to the ocean and is more difficult to clean up?

This solar-powered water wheel may be used to clean debris from water and can transfer this debris to a barge. Check out this site for more information!

P.S.: I just came across this video. It's good for a laugh.

What is a semiconductor?

"Monokristalines Silizium für die Waferherstellung". Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons

A semiconductor is a material that typically conducts electricity better than an insulator, but not as good as a metal. Electrons in the material can move around, but, in order to move around, they must overcome an energy barrier. Things at higher temperatures have more energy. Some electrons in a semiconductor are able to overcome the energy barrier (between what are known as the valence and conduction bands) and move. Dopants (other added elements) can be added to the material to change the electron concentration. Places where an electron is absent but is of low enough energy that an electron "should" be there are known as holes. It is these mobile electrons and mobile holes (absences of electrons) that conduct electricity. Semiconductors are widely used to make solar cells as well as computer chips. They are extremely useful materials.

TED talks solar

Check out these interesting TED talks on solar power!

1. Donald Sadoway, Professor of Materials Chemistry at MIT


2. Sanjit 'Bunker' Roy, founder of Barefoot College


3. Bill Gross, founder of Idealab


Recommended by Community Renewable Energy.

Light Up Nigeria!

Check out this video about what solar energy has been able to do in Nigeria!

Move over for solar!

Credit: AAP

While solar energy still has far to come, it has surpassed many milestones over the past few years to the point that it is becoming competitive with other energy sources in some locations. Check out this recent article about rooftop solar energy contributions to the grid in Australia. Rooftop solar even drove the wholesale price of electricity into negative territory and to around zero during the day for several days. It will be interesting to see how solar energy will play out in the future. Will this make coal plants less profitable and drive them out of business? What happens then when the sun isn't shining brightly? How is the energy stored? Is the rooftop model the best for consumers? For how long will those producing energy with rooftop panels be able to charge retail price for the energy instead of wholesale price? How will the utilities respond? This is another article that deals with some of this response question.

Happy 4th of July!

It's the 4th of July and perhaps a good time to fresh up your potassium nitrate knowledge?!

That's, at least, what NSF thinks and hence, nominates potassium nitrate to the crystal of the week!

The crystal-of-the-week initiative is a celebration of the International Year of Crystallography which is THIS year!

Surf Magsurf!

Superconductors are really cool materials! One property called the Meissner effect makes superconductors expel magnetic fields. To do this,  currents are induced in the superconducting material, generating its own magnetic field to cancel the field of the approaching magnet. This group from Paris made a superconducting hoverboard and magnetic track, which they demonstrate in this video. Check it out!

This is another cool video describing a superconducting material on a magnetic track. Check it out!

This TED talk talks a little about the physics of this phenomenon.

Can you imagine how this could be useful? What challenges would engineers need to tackle before using this in practical applications? Comment in the comments section.

Motivating squares!

I find these three squares very motivating!

They represent the area that would be enough for solar power plants to produce a quantity of electricity consumed by the world, in Europe (EU-25) and Germany (De) according to data provided by the German Aerospace Center in 2005 within the project Desertec. Read more about this interesting project and their current activities here!

Solar Energy Usage Record

Microsoft Clipart

Hey, check out this article talking about how Germany is using solar energy. They just set a record for single day energy use coming from solar power. Also, the benefits and costs of their approach to using solar energy is discussed.

Real or Not?

Check out this video? What do you think? Real or not?

This is a real phenomenon. With your parent or guardian's permission you can do this at home. It's a fun and easy demonstration. In science, when something is observed, we must always think about whether what we are observing is the result of the thing that we are trying to measure or if it is affected by something else. For example, it would be fruitless to use a setup like this to measure the force of gravity (it could be done, theoretically, but would be complicated to do in practice; it is much better to use a non-magnetic material or an insulating pipe (a pipe that wouldn't allow these eddy currents). It is important to always know what you are measuring and the things that could effect those measurements. For this reason, we run controlled experiments.

Solar Impulse

From www.hashslush.com

Have you heard about the Swiss Solar Impulse project? If not – read about it and follow the project activities here. Their aim is to develop an aircraft that uses only solar power! And they have already come pretty far!

I'm a scientist. Is science fun?

I just found this really cool site where scientists from all different disciplines are interviewed. Check it out! Also, check out this video, where scientists are interviewed about what excites them about science.

For me, I like learning stuff. I like gathering information and strategizing how to get more information about the real world. Although the contributions of an individual scientist are often small, I like contributing to something larger that can have real benefits to society, in general. I find science to be a lot of fun. It is like a real-life mystery novel.

Ice cream and science!

From http://www.subzeroicecream.com

One practical property of the element nitrogen is that it, at atmospheric pressure, boils at –320.4 F. This makes it suitable to use in cold traps for laboratory equipment and to cool detectors such as the X-ray detector in scanning or transmission electron microscopes.

Another, more unexpected, application of liquid nitrogen is SUPER fast ice cream making! Liquid nitrogen has made the ice cream café, Smitten, in San Francisco very popular.

                                                         From CCN Tech

The Art of Capturing the Sun and Nature, Itself

Sputtered polycrystalline Cu2Se film grown on oxidized silicon substrate

 In our research group, we study thin films of materials. Because these films and are too thin to see with the naked eye and the details of the film surface are important, we must use a variety of techniques to image our samples. These images can be quite beautiful.
The above image is a colorized image of a sputtered polycrystalline Cu2Se thin film. The film has a very rough surface (it was a bad film for what we wanted to do with it), but shows some interesting things. The micrograph shows that Cu2Se prefers to grow in certain directions and on certain surfaces, since the shapes are faceted (not rounded, flattened along certain sides). The film was extremely rough and has pinholes, as the color contrast suggests. It also looks pretty cool!

Polycrystalline Cu2ZnSnSe4 film grown on molybdenum-coated soda-lime glass 

This image shows the surface of a polycrystalline Cu2ZnSnSe4 thin film. You can see that the space is filled well (there are no holes). Similarly, the film did not grow perfectly flat, although it is much flatter than the previous image.
There are actually science photo contests. Check out the FEI image gallery or the FEI Flickr photostream.
One of my best friends is a photojournalist. I am sometimes struck by the similarities between aspects of our work. We both depict reality through images to further understanding. We both worry about our very investigative presence interfering with or altering the reality that we are trying to capture and show. I just focus on inanimate objects and how they are made, while she focuses on people and their interactions with the inanimate objects. I typically image using electrons, while she images using light. Science incorporates a lot of art.

Clean drinking water with solar energy!!

From basurillas.org

There are, of course, many different methods to clean drinking water. One is with the so-called “Solvattendunk” – an invention by the Swedish artist and inventor Petra Wadström – which makes it possible to fetch, store and purify drinking water by the help of solar energy, requiring no electricity from batteries or mains. Read more about how it works here or here.  

Solar Roadways!

Check this out! I am not sure if this will become competitive (cost) with current cement and concrete roads, but it is a pretty cool idea.

Samsø - a Danish experiment

From EDIN - Energy Development in Island Nations

Have you heard about the Danish island Samsø?
Less than two decades ago the residents living on the island were entirely dependent on oil and coal imported from the mainland.
Today, however, 100% of their electricity comes from wind power and 75% of their heat comes from solar energy and biomass energy.
Read more about this interesting danish experiment here!

Curling Physics

To cool down from this hot weather, let's look at the physics of curling. While it may appear as though you just lob a rock down some ice and then sweep like your life depended on it, there is a lot of physics involved--and not all of it is well-understood. Check out this video to learn more!

Solar Art!

Night Garden by O*GE Architects. A Solar Artworks' project.

One ill-considered argument against solar energy is
that it is ugly and takes up a lot of space. As with all new technologies we need some time to adopt and get used to the solar technology.
The more common as an energy resource it becomes, the more integrated and natural part of our society it will be. Concepts like solar architecture and solar artwork already exist and are most likely here to stay!

Solar powered art is not only an amazing combination of art, architecture and science, but takes also an important part in increasing public environmental awareness.

Have a look at some great solar artworks here and here!

Balloon Momentum

What happens to helium and air-filled balloons when you speed up or slow down? Check out this video to find out and learn why?

This is similar to the difference in behavior between electrons and holes in semiconductors. Holes are an absence of an electron (kind of like the helium-filled balloon, which is an absence of mass). Electric fields accelerate electrons and holes in different directions due to the presence or absence of negative charge.

How are theory, experiment, and simulation related continued: a conversation

Hey, after the last post, I had a good conversation with a fellow graduate student/scientist from electrical engineering. With his permission, I wanted to post this discussion, since it illustrates nicely how theory and simulation interact within different fields (no pun intended this time, although he does work in applied electromagnetism/antenna design).

I enjoyed your blog post, and I'll post some thoughts on it later when I have more time!
I noticed that the title talks of simulations, but when you break research down into catagories, you instead use engineering.
(Simulations were lumped into theory.)
Granted, the theory/simulation/experiment breakdown isn't perfect or without overlap, but I personally think it's more accurate than putting engineering as a catagory.
"Engineering" to me is a process or tool, not a type of research

EE

Yeah. As I was going about it, I found it difficult to break down theory and simulations

Elizabeth Pogue

ahh, ok
Simulations use theory, that's true

EE

I think I might leave it as-is for the blog title. There are journals that just focus on instrumentation and engineering technologies and it is really distinct from the other two.

Elizabeth Pogue

Fair enough.
It hit me, I think why simulation and theory are different in my mind is that theory tends to build up more models and more complicated models
whereas simulations sometimes are built on repeated (and thus numerous and tedious) applications of first principles
This is a very broad generalization

EE

I think I know why we see different degrees of space between theory and simulation. For materials, you are already fairly close to first principles. You have theory that describes first principles but, that theory is often too tedious to totally do, so you end up doing simulations.

Elizabeth Pogue

The same is true for E&M: simulations usually are based on Maxwell's equations and derivations thereof

EE

True.

Elizabeth Pogue

Theory, such as transmission line theory, builds on that behavior to create larger, simpler models
There are usually assumptions or approximations built into theory, less so for first principles
It depends on the number and degree of approximations, of course
I think the difference I'm seeing could be between our fields
In my mind, theory is something that you can do on paper (possibly with a calculator) and get useful, practical results out
Whereas the theory you're talking about describes what happens, but may not always be directly and easily useful for predicting results or doing design
heck, even that's not always true
dunno
lol

EE

It is possible. If you look at something like density functional theory, you are making approximations about electron density inherent in the theory. It is based on quantum theory, but is generally still referred to as theory, not a simulation.

Elizabeth Pogue

Agreed
Simulation (or calculation) to me is number-crunching on more accurate models
Stuff you wouldn't do by hand

EE

That is why I was having difficulty clearly distinguishing them, other than saying, within theory, that simulations implement theory.
I agree with you on that.

Elizabeth Pogue

Yeah, that's a good point
simulation/calculation is a subset of theory
but given the number of researchers devoted to implementing such programs, it's really a realm of research distinct from theory
It builds off theory, but uses computer science (algorithms, data structures, etc) to practically model/simulate/calculate with said theory

EE

Yes. I changed it to say that generally simulations can't be done by hand, where theory can often be implemented by hand.

Elizabeth Pogue

Sure
And I'm sure physicists would nit-pick that definition too
Depends on your field, I guess!

EE