Heliotactic Press

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

What to do with solar in the economic turndown 2009/03/21

Filed under: education,energy,photovoltaics,Solar Decathlon,solar energy — nanomech @ 10:24

As you may have noted, I am in the process of developing this blog that extends beyond (Nanomech in Photovoltaics). The reasons? First, the Sun allows for a plethora of possibilities, and I wanted to work with a bigger canvas! Second, I feel the need to open up the blog to entries from guests, to create a diverse perspective of all things tied to solar (including energy efficiency, green roofs, passive solar design, energy recovery and cogeneration). And third, and most frankly, PV is the most expensive solar investment for the individual. In this economic depression, we need to know what technologies are affordable and offer the highest rewards for the initial investment. I’ve been told again and again that solar hot water is the most obvious, no-brainer tactic in the solar arsenal. It’s cheap (< $6000 for everything), it’s easy, and by replacing/complementing your electric or gas (or fuel oil) water tank (with federal and state incentives), payback is often less than 5 years.

My recent experiences have included teaching solar energy conversion, developing tools for solar resource assessment, and leading a great team to design, build, and operate a solar-powered house (www.solar.psu.edu). From these endeavors, it was obvious that it would be beneficial to pass along the great breadth of solar energy conversion possibilities.

So, I still hope to post on photovoltaics (still my favorite, and I am a materials researchers in PV), but expect to see more on diverse topics in the future.

 

Solar Jobs = Green Collar Jobs! 2008/12/28

Filed under: industry,photovoltaics,solar power,sustainability — nanomech @ 10:13
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As a researcher and instructor dealing with solar energy conversion, I am acutely aware of the immediate need (or ASAP) for a smart, flexible labor force–capable and trained to install and maintain our new solar technologies. Solar energy will be the heart of the new green collar job sector, as we will need to deploy PV and solar hot water technologies to residential and commercial buildings for a carbon-constrained future.

Analogy:
I want to use the familiar example of technologies for indoor air quality and thermal comfort: HVAC systems (Heating, Ventilation, and Air Conditioning). Think about how many air conditioning units are now an integral part of buildings in the country. Consider the labor force that is required for AC/heating installation, duct installation, monitoring and control systems (e.g. thermostats), and maintenance or repairs (hint: it is a huge industry). Now think about how little you think about these systems (because they just work). There is similar (perhaps even greater) potential for green collar jobs–earning a paycheck and helping society and the environment!

The Very Near Future:
Green collar jobs for solar technologies are here! Training is in full gear in states like California, New Jersey, and Florida, and is ramping up in Wisconsin and Pennsylvania. At Penn State, we are already working on a training course for PV installation, as well as an upper level college course in solar energy technology design.

Additional reading: NYT article on PV installers as the new wave of green collar jobs.

 

Solar technologies are really quite diverse 2008/12/25

Filed under: education,energy,interdisciplinary research,photovoltaics,solar,sustainability — nanomech @ 10:38
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In preparing for my annual Spring course “Design of Solar Energy Conversion Systems”, I am reminded of just how many diverse technologies can be derived from our nearest large-scale fusion reactor. I will make exceptions to the obvious: horticulture and wind energy are derived from the sun too.

Here are some ideas beyond PV and concentrating PV (CPV):

  1. Passive/Active Solar Water Heating Systems (in your showers, dishwashers, heating your floors)
  2. Commercial/Distributed Space Heating Systems (using Solar Walls, Phase Change materials, Pebble-bed hot air storage).
  3. Solar Cooling (Yes! you can cool with the sun and heat pumps, dessicants, refrigeration cycles).
  4. Solar Industrial Process Heat and Solar Ponds (Do you own a mine or a refinery? Look into ways that you could dramatically reduce your energy bills!)
  5. Solar Thermal Power Systems (Also called Concentrating Solar Power–CSP–this is the technology with the best odds at being the next wave of electric power from the sun).
  6. Don’t forget solar chemistry (not just growing plants) to make hydrogen and other fuels!

Solar is very close to breaking out. Why not invest in solar tech?

 

Photovoltaics: Levels of Irradiance 2008/08/02

Filed under: concentrating solar power,irradiance,light,photovoltaics,solar cells — nanomech @ 11:54

Let’s talk about light interacting with a semiconductor to yield electricity. Today’s topic is to distinguish between low levels of irradiance and high levels of irradiance. Effectively, we are asking for an estimate of the concentration of photons being delivered from a high energy source to a low energy absorber/collector.

When we say low levels of irradiance, we are estimating a scale of light concentration that is typical of the diffuse and direct component of unconcentrated “global” or “total” solar radiation, or the light from a standard incandescent lamp or fluorescent lamp. This could be anywhere <1000 mW/cm2, or 10x the sun’s concentration (remember, this is just a crude scale, not a hard and fast rule–don’t take this back to your classes). The standard for testing solar cells inside the earth’s atmosphere is called Air Mass 1.5 Global (AM 1.5G), because the light from the sun passes through 1.5 lengths of a generic Earth’s atmosphere to generate a convenient irradiance of ~ 100 mW/cm2. Low levels of light such as this provide a sufficient number of photons (packets of light) to excite the electrons into an unoccupied level of energy (the conduction band). However, the population distribution of the majority carriers does not change significantly. That’s okay: the key player in a photovoltaic absorber is the minority carrier (n-type semiconductor: a hole; p-type semiconductor: an electron), and the population of minority carriers does change significantly with light absorption. Minority carrier transport gets the job done, in fact, because they are the limiting rate in the absorber reactor. You can find out more about charge carriers and carrier transport in the Photovoltaics CDROM from Honsberg and Bowden, Chapter 3 (although it doesn’t work completely for Macs, sadly)

What is high irradiance? You’ve heard the warnings about strong lasers pointing into others’ eyes? A laser is a coherent, collimated light source (the photons’ waves are in phase and heading the same direction), such that the photons can be very concentrated. If sufficient numbers of photons are absorbed by a semiconductor, the population of photoexcited charge carriers can be much greater than the majority carriers, and there a population inversion occurs, leading to stimulated emission (Light Amplification by Stimulated Emission of Radiation).

The photons from light bulbs and suns are neither coherent nor collimated, although they can be concentrated significantly to potentially cause a population inversion and stimulated emission (yes, there is the possibility for a solar laser). However, before that stage there are other phenomena that occur, making it a bit more complicated.

Concentrating cells allow an increased flux of photons to the smaller receiver/absorber using a larger aperture to collect the solar light. The geometric concentration ratio is the ratio of the area of an aperture to that of the absorber (C=Aapt/Aabs).1,2 For a perfect concentrator (as a point on the surface of Earth), the radiation from the Sun on the aperture-receiver assembly is only a fraction of the total radiation emitted by the Sun, given a half-angle subtended by the Sun of 0.27°. Assuming a blackbody, the absorber would have a maximum theoretical concentration ratio of 45,000 (for a circular concentrator) or 212 (for a linear,trough concentrator).1 The higher the concentration,the higher the photon flux (including increasing temperature),and the more precise the optics of the collector must be to deliver. This is an extreme energy flux for any semiconductor. Under high illumination levels, one will observe a decrease in minority carrier lifetimes and related diffusion path lengths. However, 45.6% of the suns power is contained in the infrared band (the part that makes things “hot”). Thermally, an imaging concentrator (C>> 10; analogous to camera lenses) can produce temperatures from 500 to 1500 °C at the absorber.2 This increased temperature can be used to drive thermal work (steam generation) or thermophotoelectrochemical reactions for concentrating solar power (CSP, not to be confused with CPV), but is not necessarily good for photovoltaic performance. High temperatures tend to decrease the efficiency of a photovoltaic device. In particular, this is why members of the microelectronics industry are getting into the concentrating photovoltaics field (CPV)–they know how to cool superhot microelectronics, and will do the same with CPV devices.

It is so interesting to see how this is all a great spread of possibilities that one can derive from our nearest fusion reactor!

Text sources:
1. Rabl, A. Active Solar Collectors and Their Applications. 1985 Oxford University Press, New York

2. Duffie, J. A.; Beckman, W. A. Solar Engineering of Thermal Processes. (3rd Ed.) 2006 John Wiley & Sons Inc, Hoboken, NJ, USA.

3. Andreev, V. M.; Grilikhes, V. A.; Rumyantsev, V. D. Photovoltaic Conversion of Concentrated Sunlight. 1997, John Wiley & Sons Ltd, Chichester, England.

 

Surfing more and more photovoltaics! 2008/07/23

Filed under: Al Gore,next generation,photovoltaics,solar,Solar Decathlon — nanomech @ 12:36

In just a few years since returning from France in 2006, I have noticed some significant improvements in the world of PV within the United States. In fact, it seems that there is a wave of solar development and deployment that is rolling across the country!

Let me preface this glowing remark by commenting that not all was so great even two or three years ago. I had been working for a year in a laboratory in France that specialized in basic research for silicon and eta-cell (extremely thin absorber) thin film photovoltaic devices. While there, I was working with members of industry, the French government and power company, and the French national lab system. It seemed that there was a great vertical integration of research, industry, and deployment in France (and even more occurring in Germany). It was therefore a bit of a let down to return and learn how far behind the US was in terms of this integration. Yes, there are two major centers for research in Colorado (NREL) and Florida (FSEC), but as a national whole, the system seemed a bit worn, frumpy, and patchwork in nature. In truth, the USA went through about a 25 year period where not much was visible at all in solar research. The funding had dried up, leaving room only for the biggest four or five names in materials research and computer simulation (who supplemented their funding with studies in refrigeration). Now, many of the notable solar researchers are either retired scientists, microelectronics specialists, or emeritus professors.

However, in the two years since I returned there has been a dramatic bootstrapping occurrence. Just as we are looking to “next generation” PV technology, so are we seeing “next generation” researchers, educators, and industrial developments! Gunther Portfolio is a great blog for keeping us informed about developments for investing, and SolarBuzz and PVNews/Greentech Media also have regular installments of more and more PV industry growth.

In education, Penn State launched a new Spring 2008 course from the Dept. of Energy & Mineral Engineering, focused on solar energy conversion (with emphasis on photovoltaic conversion). Penn State also has plans to develop another more hands-on course in photovoltaics for extended education in the near future. Prof. Tonio Buonassisi of MIT has also announced a course in photovoltaics set for this Fall 2008 semester. The students have spoken, and they want more information on the current state of the art in solar and photovoltaics!

In the federal government realm, we are still sadly lacking a signal to encourage PV via incentives. The residential tax credit is slated to expire at the end of this year (following an extension). You will find much better luck for incentives on a state by state basis (see DSIRE). However, we did just receive a call to action by former Vice President Al Gore that may put more senators and representatives “in the mood” for renewable electricity generation. Also, the Solar Decathlon is to continue until 2015, the projected year for levelized cost of electricity generation from PV to be competitive with coal-fired electricity generation. The sponsor (DOE/NREL) projects half a billion visitors to the Mall area over a three-week period in September 2009, and anticipates global exposure to the Solar Decathlon concept to over one billion people. The Solar Decathlon is also exerting a viral effect on solar engineering and design, as it is inspiring similar competitions globally. Even now, a Solar Decathlon Europe is planned for 2010 in Madrid, Spain. The city of Beijing will be holding the 2009 Delta Cup – International Solar Building Design Competition, where the winning homes will be deployed in the earthquake-hit areas of Sichuan.

Keep up the good work, solar community! Let’s continue to work together to provide more information and more incentive for the broad public to adopt solar renewable energy. Of course, if a major component of that is photovoltaics, I would be pretty ecstatic!

 

Natural Fusion recap 2008/04/19

Filed under: Natural Fusion,Penn State,photovoltaics,Solar Decathlon — nanomech @ 08:25

It has been a very busy semester at Penn State. I’ve served as the faculty director for the Solar Decathlon 2009 effort (Natural Fusion project), I’m developing a course in solar energy conversion, I’m establishing my materials research laboratory, and I’m the outreach and recruiting coordinator for my department. Even so, one of the fun aspects of my job is that so many things overlap each other, and there seems to be an unusually high rate of “moments of synchronicity”. The class overlaps with the project, and the project helps with recruiting, and I’ve gotten to know more people on campus than I ever would have hoped for in my first year at University Park. What a blast!

In the Natural Fusion project, I have 15 amazing students serving as project managers from multiple colleges. They all have the vision and energy to turn this competition into a brilliant learning experience for integrated design, green building, and entrepreneurship. We also already have a team of over 100 (!) students that are helping in our design and marketing process.

I am also fortunate to have two other experienced faculty members deeply involved in the mentoring experience, and several more faculty available for support in the future. The team has been out to several industries seeking support in mentoring, materials, and direct funding–and things are looking very good. Even in the first four months, it appears that we will be testing and deploying many new technologies in photovoltaics and energy efficient materials. It’s not without its stressful periods, but I feel that we have a really great thing going that will be both memorable and valuable to all of our futures.

 

Solar Decathlon…ho! 2007/12/11

Filed under: Morning Star,NREL,Penn State,photovoltaics,Solar Decathlon,sustainability — nanomech @ 16:44

The Solar Decathlon is a progressive competition, offered to selected universities across the nation and outside of the USA every other year, in which students from multiple disciplines design and build a home completely powered by the sun. The focus of the competition is to combine BIPV (Building Integrated PhotoVoltaics) with new energy efficient architecture and its engineering systems. The competition was initiated in 2002 by NREL/DOE in conjunction with major sponsorship by British Petroleum, and the official two-year cycle was continued as of 2005 (SD2005).

The Decathlon operates within the general goals of the Solar America Initiative of the DOE, to make photovoltaic solar energy cost-competitive with conventional energy forms by 2015 (levelized costs of $0.10/kWh for PV). A major focus is to encourage relations between Academia and Industry for integrated design of photovoltaics within standard building practices. However, it includes the incorporation of the project into the curriculum of the students, as well as their involvement with industry. The Decathlon is projected to continue until 2015.

The winner of SD2007 was: Technische Universität Darmstadt. That’s correct; Germany won the USA solar home competition on their first try (why shouldn’t the biggest PV player in Europe be a strong competitor?). Perhaps this was an appropriate challenge to wake up integrated PV education in the states.

My own new home, Penn State University, took 4th place on their first attempt, Morningstar Pennsylvania. We’re looking forward to the opportunity to return and improve upon that standing in SD2009. It’s a great opportunity for students and faculty alike, and all products displayed in the Solar Decathlon homes are commercially available, which will make the project pretty interesting as the competitions progress to 2015.

 

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!

 

PV Documetaries: The Power of the Sun vs. Saved by the Sun 2007/05/13

Filed under: photovoltaics,Saved by the Sun,The Power of the Sun,Walter Kohn — nanomech @ 12:35

When making a science documentary, shouldn’t a good science background be involved in the production?

Please note: The solar power of today is not the solar power of the 1970s (or the 80s, or the 90s…)!

I have viewed the two recent big documentaries on solar power: The Power of the Sun and Saved by the Sun. In comparison, my summary argument: a scientific background goes a long, long way to gelling the message of a science documentary.

For those short on time: watch The Power of the Sun and show it to all of your friends. You can purchase the DVD for US$10 +shipping (half price if you are a teacher!). It provides the scientific background of silicon photovoltaics (PV), as well as a future for solar power. The latter documentary is a highly-diluted and out-dated science commentary with a generous mix of 60s and 70s nostalgia to mask the lack of content and vision.

Both films are produced in the US, and deal with the recent boost in development and financial interest in solar power. The executive producer of The Power of the Sun was Nobel Laureate Walter Kohn, while Saved by the Sun was produced by Steven Latham, Larry Klein, and Evan I. Schwartz (scientific backgrounds unknown) under the NOVA series of PBS television.

While the NOVA special has some value in getting people aware of commercially available PV, there is a distinct lack of presentation of the science and the broad range of industries already involved in major PV businesses. They don’t give credit where it is due, and misplace other credits by a lack of depth of inquiry. Instead of talking about the fact that PV in Japan is now unsubsidized, and many new Japanese homes have PV funding incorporated into home loans, the film implied how “curious” the Germans are for creating a heavily subsidized solar market and entire farms of PV. Skeptical economists are called in to reassure us that solar energy is still a long way off folks. That could never happen in the USA, economic analysts scoff. Except that it is happening in the rest of the world, and we’ve woven ourselves into a global economy. A market with a 37% cumulative growth rate (meaning a doubling time of 2.2 years), and a 2006 peak power output of ~2.5 GW (Gigawatts) is not an economic fringe commodity.

Following this disjoint, Prof. Nate Lewis of Cal Tech is interviewed for his contributions to photoelectrochemistry (which are very significant). However, instead of going into the new chemistry his group works on, he is essentially given credit for recently creating dye-sensitized solar cells (that were first developed by Brian O’Regan and Michael Grätzel in Switzerland and reported in Nature in 1991). Couldn’t the filmmakers have asked Nate, so how long has this been around?

Add on top of all of this, a penchant for 1960s and 1970s counter cultural pop tunes including the word “sun” or “sunshine”, and you have officially alienated the new generation of PV consumers. Thank you NOVA and PBS.

Prof. Kohn had informed us at the American Chemical Society’s viewing of The Power of the Sun, that PBS turned down the opportunity to show this film. It was deemed too controversial, due to a comment by narrator John Cleese that the world was “dangerously dependent on fossil fuels, even addicted to them”, and due to a suggestion that fossil fuel combustion may even be linked to “global warming”. Curiously, one G. W. Bush did see The Power of the Sun in a personal viewing, and something of that phrase slipped into one of his speeches.

Hmm, I guess good science does have an influence on policy.

* Plot developed by JRSB from data by PVNews and the Prometheus Institute for Sustainable Development.

 

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.

 

 
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