Over 86,000 terawatts of solar energy reach the Earth’s surface each year- enough to satisfy current global energy demand 1000 times over. In 2008, solar electric power amounted to a mere 0.2% of global energy produced but it is at a tipping point with a growth rate of 40% per year. Exponential growth, enormous solar resources and the global economy's unquenchable demand for electricity increasingly position photovoltaic power as vital to 21st century technology.
In this rapidly changing industry, the Solar Power Lab stands-out as having some of the most experienced researchers in the field. This, coupled with state-of-the-art facilities and institutional support, gives SPL the solid foundation necessary to push the boundaries of what has become a $20 billion sector of the economy.
Arizona State University’s Solar Power Lab serves a staging ground for the new technologies and ideas that will move us forward in our quest for a more sustainable society.
The Solar Power Lab has numerous capabilities such as:
- A full pilot line for 6 inch solar cells with an average efficiency of 18.5% for diffused cells
- New 6 inch solar cell line doe 22%+ heterojunction cells.
- Extensive capabilities for silicon solar cell characterization
- Molecular Beam epitaxy system for nano-structured solar cells
Record Open Circuit Voltage for a Silicon Solar Cell
Analysis of the recombination mechanisms of a silicon solar cell with low bandgap-voltage offset was published. http://aip.scitation.org/doi/full/10.1063/1.4984071.
The mathematical dependence of bandgap-voltage offset on Auger and radiative recombination is derived. Open-circuit voltages over 760 mV were measured on 50-μm-thick structures, leading to bandgap-voltage offsets at open-circuit down to 0.35 V. We demonstrate the potential of thin silicon devices to reach high voltages, and bandgap-voltage offsets in line with the best reported for direct bandgap materials such as gallium indium phosphide and gallium arsenide.
Picture and legend: Intrinsic open-circuit voltage (black curve) and intrinsic bandgap offset open-circuit voltage (red curve) as a function of cell thickness, considering the Auger, the radiative recombination mechanisms as well as the Lambertian light-trapping limit. Recent experimental results of high VOC for silicon and the corresponding WOC are shown.
Seminar: Demand Side Management of PV Systems in Rural Areas in Africa
Seminar: Demand Side Management of PV Systems in Rural Areas in Africa
Speaker: Catarina Augusto
May 16, in ERC 189, from 2:00 to 3:00 p.m
Renewable energy systems depend strongly on energy efficiency, impacting directly the power size of the systems, and the investment cost. In developing countries, energy supply is poor and the investment costs are high. In this scenario, energy efficiency is critical to secure proper energy supply, more than in developed economies. Demand Side Management (DSM) can help to answer to this problem. In this work, we study the potential of DSM on renewable energy microgrid systems in remote areas. Fossil fuel and batteries are the two most expensive components in these systems. We analyse the impact of DSM strategies in reducing the needs of fossil fuels and how it could improve the performance of batteries in the microgrids. Different scenarios were design based on the main DSM strategies: conservation, peak clipping, load shifting and valley filling. The study is based on Soroti community, a small town in central-east of Uganda, supplied by a PV-diesel microgrid system. The tools used in this study are LoadProGen (for load profile estimation) and HOMER (for DSM scenarios analyses). The results show that combining all DSM strategies improve the performance of the power systems, and reduce the energy supply costs. The study also demonstrate that the nominal power capacity of the system has a higher impact on the energy cost than the reduction of diesel consumption. In systems with DSM, the LCOE has an improvement of 20%. These results highlight the importance of the often-neglected DSM strategies for isolated microgrids, which have the potential for promoting access to electricity in many regions of the world with clean renewable energies.
Catarina Augusto is a final-year MSc student in Energy and Environmental Engineering at Science Faculty of University of Lisbon (Portugal). Her background is on: renewable energy systems, solar photovoltaic and energy efficiency. She also studied energy systems in Utrecht University (Netherlands). In last year, she developed comprehensive work on Demand Side Management of energy systems getting proficient in two tools: LoadProGen and HOMER. LoadProGen is a mathematical algorithm in Matlab created by the UNESCO chair Group in Energy for Sustainable Development of Politecnico di Milano that estimates daily load profiles of un-electrified communities in rural areas. HOMER is a software developed by NREL that optimizes the design of microgrid systems.
QESST at the Aprende Science Fair
At the science fair for the local middle school QESST put on a display on solar and fun to be had with liquid nitrogen. The temperature reading on the liquid nitrogen wa -309 °F. Arizona normally doesn't normally get that cold!. The display was to complement the excellent work done by the Aprende middle school student for their science fair project. Thanks very much to SPL students Max, Alex and Mark for making the night such a success.
Cover Story of the latest Journal of Engineering Education
We made the cover story of the latest edition of the Journal of Engineering Education (JEE). Katherine Nelson's PhD work on "Students’ Misconceptions about Semiconductors and Use of Knowledge in Simulations" was featured as the cover story on the April 2017 edition of the Journal of Engineering Education. Solar Cells are based on the principles of semiconductor device physics. Dr Nelson and her co-authors used the instructional materials at the pveducation.org website to explore how student's misconceptions are either reinforced or overcome by the animations. Her findings will enable instructors to create better simulations to aid student learning.
The full paper is at: http://onlinelibrary.wiley.com/doi/10.1002/jee.20163/full
Little research exists on students’ misconceptions about semiconductors, why they form, and what role educational resources like simulations play in misconception formation. Research on misconceptions can help enhance student learning about semiconductors.
This project sought to identify students’ misconceptions about three semiconductor phenomena – diffusion, drift, and excitation – and to determine if prior knowledge, knowledge acquired from watching animated simulations, or both were related to students’ misconceptions. We hypothesized that students would hold misconceptions about those phenomena and that students’ prior knowledge and knowledge acquired from watching animated simulations would be associated with their misconceptions.
Forty-one engineering students completed an instrument that asked questions about three semiconductor phenomena after the students had observed the animated simulations. Responses were analyzed and coded using two frameworks: misconception and knowledge use.
Misconceptions were prevalent for all three phenomena. Misconceptions were associated with use of incorrect prior knowledge, a combination of correct or incorrect prior knowledge, and the knowledge acquired from watching the animated simulations alone or in combination with correct and incorrect prior knowledge. Misconceptions indicated a lack of understanding of chemistry and physics concepts.
Findings indicate that students hold many misconceptions about semiconductor phenomena. These misconceptions were common among our participants. The knowledge acquired from the animated simulations alone or in combination with prior knowledge could reinforce or contribute to misconception formation. Our findings can guide instructors to use or create better simulations to aid student learning.
Photovoltaics now 1.8 % of the world's electricity
The latest report from the International Energy Agence (IEA) shows that photovoltaics supplies 1.8% of the world's electricity consumed. Photovoltaics (PV) grows exponentially while electricity demand grows slowly so it was only two years ago that photovoltaics supplied less than 1% of the world's electrcity. At current growth rates photovoltaics will suppply all the world's electcity in 2030. A more likely scenario is that the declining costs of photovoltaics will enable access for the 1.1 billion people without electrcity, and new technologies such as electric cars.
Solar research facility on Tempe campus poised for big developments
Federal officials tour ASU's photovoltaics lab, the nation's largest
New Solar Cell Tester
ASU took delivery of a new advanced solar cell efficiency tester from Sinton Instruments this week. The new tester is a FCT-450 and is an upgrade of our previous tester also from Sinton Instruments. A significant advantage of the new system is the ability to measure smaller area cells, a broader range of temperature measurements and the extraction of substrate doping from the completed solar cell.
Like the previous model, the new tester is capable of autmoated SunsVoc and LightIV measurements giving unambigous extraction of cell series resistance and shunt resistance. The tester uses a voltage modulation technique to neutralize the capacitive effects in high performance solar cells. With our record voltages we experience decay lifetimes of 2 ms in the completed cells. Most testers have problems with our cells as the sweep rate is a similar order of magnitude. We have found that the voltages from the FCT match those measured at NREL even for cells where the voltage approaches 750 mV.
All About Solar on YouTube
All About Solar cells is a series of lectures on the use and fabrication of solar cells.
The solar cell industry continues to grow in leaps and bounds and will have a major impact on energy production in the future. The Solar Power Laboratory at Arizona State University has been running the student led pilot line for the past six years as part of the QESST research Engineering Research Center and more recently included the NCI-SW. The line has had taught over 200 people how to make a solar cell in hands on setting where the learners get to make a solar cell from start to finish. Many of the learners are already experienced in the industry while for others it is their first time in a laboratory.
One of those students, Edward LeBeau, wanted to give something back to the pilot line. He recognized that while there were lots of resources on the fabrication of solar cells they weren’t always relevant to what happens in the lab. “The Pilot Line was a great introduction to research during my first year at ASU. I wanted to give something back, and thought a set of introductory lectures for people who are new to solar would be a good contribution,” said Eddy. Using resources from SPL, he developed a series of lectures to provide the background information to the fabrication of the cells that we make. He starts out with an overall introduction on the solar cell industry and then continues through cell fabrication and characterization.
These lectures are now available for free on youtube. We hope that they will be useful not only for people learning how to make solar cells at the ASU pilot line but also for people who want an introduction to the way solar cells are made.
Each lecture is about 10 minutes in length and the whole series takes about an hour.
- Lecture 1: Introduction to Solar Cells
- Lecture 2 part 1: Operation of solar cells - Electrons and Holes
- Lecture 2 part 2: Operation of solar cells - Voltage and Current
- Lecture 3 part 1: Physical construction of the solar cell
- Lecture 3 part 2: Manufacturing process from sand to cell
- Lecture 4: Characterisation of Solar Cells
- Lecture 5: Past, Present, and projected cost of solar energy
Quantum Energy and Sustainable Solar Technologies (QESST) is an Engineering Research Center (ERC) sponsored by the National Science Foundation (NSF) and the U.S. Department of Energy (DOE) that focuses on advancing photovoltaic science, technology and education in order to address one of society’s greatest challenges: sustainably transforming electricity generation to meet the growing demand for energy.
Nanotechnology Collaborative Infrastructure Southwest ( NCI-Southwest) supports the advanced tool-set, faculty expertise, and knowledgeable staff required by academic and industrial users performing research at the frontiers of nanoscience and engineering.
Industry and Innovation Program
Regher Solar LLC, a QESST spinout company, recently announced reaching a cell efficiency of 21.3% as confirmed by the National Renewable Energy Laboratory in Colorado. Regher is cofounded by Dr. Stanislau ‘Stas’ Herasimenka, a postdoc and QESST alumni.
While at QESST, Stas developed all aspects of silicon-heterojunction technology from wafer cleaning to commercial PV panel prototyping. With five patents and two disclosures to his name, Stas intends to develop a patent portfolio that will help create a defensible market position for Regher.
The cell with 21.3% efficiency had open circuit voltage of 730 mV, short circuit current of 38.5 mA/cm2 and fill factor of 75.8%. “We expect to quickly increase the efficiency of our cells to over 22.5%, which we are routinely measuring on 100 cm2 aperture area cells,” Stas said. “This will open a route to potential customers from the PV industry interested in scaling next generation manufacturing technologies for high efficiency silicon solar cells.”
Pictured below is the photo of silicon heterojunction solar cells with plated copper contacts developed by Regher Solar in collaboration with QESST Scholars at the QESST Solar Power Laboratory.
Undergraduate Presents at IEEE Conference
QESST scholar Antony Aguilar was invited to present an extended oral talk at the 2016 IEEE Photovoltaics Specialist Conference (PVSC) in Portland, Oregon. Antony presented the paper, Development of Cu Plating for Silicon Heterojunction Solar Cells, representing the High Efficiency Silicon Solar Cell (HESSC) team directed by QESST faculty, Stuart Bowden. Co-authors included other QESST scholars and industry partners from Technic (Krystal Munoz, Lynne Michaelson, and Tom Tyson). The presentation described an alternative metallization to the standard low temperature Ag paste for Silicon Heterojunction Cells (SHJ) cells.
Impacts and Benefits
- Antony reported the results of a study comparing various patterning and plating methods for the deposition of Cu electrodes on transparent conductive oxides for silicon heterojunction solar cells. The best silicon heterojunction cell with Cu contacts directly electroplated on the sputtered Ag seed achieved 21.9% efficiency on 153 cm2area.
- A talented QESST undergraduate scholar transitioned to an ASU graduate program in Electrical Engineering with experience and confidence
Explanation and Background
Presenting the extended oral talk at PVSC is an unusual honor for an undergraduate student. It was Antony Aguilar’s first paper presentation; “I nearly passed out before presenting on the day of the conference because I was so nervous - I get nervous just thinking about it”. Antony received a lot of support in preparing to present, particularly from the HESSC lab manager, Stanislau Hersasimenka. Antony also appreciated the feedback he received from the PVSC audience, “Some people stayed after to talk to me about my research. They wanted to know what future work I was doing. They approached me like an experienced researcher.”
Antony was born in California, but grew up in Mesa, Arizona. Following high school, he enrolled in community college with an interest in forensic science, but soon switched to electrical engineering. Bouncing between four colleges to fulfill credit hours, Antony took numerous classes while working Dave & Busters to support himself. “I worked there way too long and decided if I was going to do anything with my life I had to quit.” After successfully applying to and participating in the QESST REU, Antony transferred to Arizona State University and began working in the HESSC lab. There he became known for fixing lasers, designing Arduino circuits, and installing new safety measures for lab equipment. “That’s when Stas asked me if there was a way to contact probes to a solar cell. Little did I know that would become an IEEE paper and even my dissertation research.” Antony transitioned to graduate school in fall 2016.
In addition to being a committed scholar, Antony participates often in QESST outreach. “I think it’s important to inspire the next generation... I know for a fact if we were missing one of these brilliant people who work at our lab, there would be a huge gap in research. Everything we do here [at QESST] is important; the more people who do it the more chance we have of developing better solar cells, better, safer, cheaper products… I wish QESST came to my high school; I probably would have got interested a long time before I did. I was good at math and science, but there wasn’t much to hold my interest. If I had some inspiration like that, seeing what you could do with science, I might have got here a lot sooner.”