Oxana Pantchenko

Miniaturized concentration cells for small-scale energy harvesting based on reverse electrodialysis

We describe experimental and theoretical results that demonstrate the feasibility of power generation using concentration cells based on ionic concentration gradients and reverse electrodialysis. A peak power density of 0.2 (0.7) μW cm−2 and a maximum energy density of 0.4 (0.4) mJ cm−3 delivered in 3 h to a 2 (5) kΩ resistor were recorded using a microfiltration (anion exchange) membrane, respectively. A comprehensive model is developed to predict the evolution of the output voltage with time in relation to the solute concentration in each cell and derive the power density and efficiency limits.

Work in progress — Enhancing students learning through instructional videos during hands-on laboratories on renewable energy sources

At the University of California Santa Cruz, a renewable energy sources course is a theory based course that includes six hands-on laboratory experiments. The course is designed for engineering and non-engineering undergraduate students and does not require any advanced mathematics or physics background. Each laboratory experiment introduces a miniature version of an energy conversion device that mimics the insights and workings of a real scale device. The hands-on laboratory experiments illustrate principles of the; solar pathfinder, flywheel, hydroelectricity, wind turbine, thermoelectricity and a fuel cell. In the past, each laboratory consisted of paper based instructions, pre and post questionnaires and a laboratory kit. Since many students in the class were non-science majors and had difficulty following the paper based instructions, we substituted the paper based instructions with instructional videos to ease the kit assembly and enhance student learning by providing more time to focus on the data gathering and analysis processes by minimizing the assembly time. The instructional videos demonstrate the experimental set-up and a method for collecting the data during each hands-on experiment. This work in progress paper presents description of our methods.

Application of MEMS technology and engineering in medicine: a new paradigm for facial muscle reanimation

Translational research may lead to development of micro-electromechanical system-based devices to treat muscle and nerve dysfunctions whose current treatments are inadequate and, at best, palliative. This paper discusses the development of engineered microsystems as a treatment option for palsies of the seventh cranial nerve and the potential application of these devices as a platform technology for treatment of other nervous dysfunctions. The engineering techniques for electrical and chemical stimulation of denervated muscle are discussed along with current caveats from clinical and engineering standpoints. As opposed to current treatments, miniaturized implants offer the possibility of the reduced toxicity and increased specificity of direct drug delivery. As with the increased miniaturization of other technologies, engineering of these increasingly small implantable microsystems holds great promise for the future development of yet smaller, even nanoscale, implantable devices.

Design of unique simulators to evaluate medical device susceptibility to radio frequency identification exposure

Background: The use of radiofrequency identification (RFID) in healthcare is increasing, but one of the biggest obstacles for widespread adoption is electromagnetic compatibility (EMC). Numerous studies have documented that RFID can interfere with medical devices. No recognized standard test methods currently exist to address medical device EMC from RFID emitters. This study identifies a potential protocol to test the effect of RFID exposure on medical devices. Methods: We developed four separate simulators which cover four distinct RFID frequency bands: Low frequency (LF): 125 kHz; High frequency (HF):13.56 MHz; Ultra high frequency (UHF): 915 MHz; and 2.4 GHz. The RFID Test Library includes actual RFID input signals and recommended field strength values for each simulator. The simulators consist of Helmholtz coils for LF and HF and use IEC 61000 4-3 exposure methods for UHF and 2.4 GHz. Discussion: The protocol presented in this paper represents one way to test if your medical device could be affected from exposure to RFID readers. The antennas chosen are used to produce repeatable tests. The input signals and field strengths are chosen to represent a wide variety of actual RFID reader technologies. Summary: The protocol needs to be tested with actual medical devices to understand the effects of the varying RFID test signals and to determine if the RFID Test Library is adequately defined. These tests are currently being conducted independently by the Food and Drug Administration (FDA) and MET Laboratories. Suggested maximum field levels are calculated and presented as a reasonable worst case exposure. It is the intent that after test validation this protocol will be submitted to the Association for Automatic Identification and Mobility (AIM) for publication.

An online simulator for thermoelectric cooling and power generation

We present an online simulator that can be used to teach the principles of thermoelectric energy conversion, and analyze the detailed performance of Peltier coolers or thermoelectric power generators with simple user interfaces [1]. The simulation tool is implemented on nanoHUB.org, so it can be run on any web interface without the need to install commercial software. The simulation tool solves the heat balance equations at the top and bottom sides of the thermoelectric device using 1D thermal network model and the electric circuit model to analyze the steady-state temperatures of the device and the thermoelectric energy conversion efficiency. Both cooling and power generation modes can be solved upon users input. Using this simulator, users are able to optimize the performance of a thermoelectric device with a variety of different design parameters such as the device dimensions and material properties. In particular, this simulator can be very useful to teach the importance of the thermoelectric figure of merit, ZT, of the material used on the performance of the device. This simulation is also instructive to show that as material properties improve Carnot limit can be achieved at negligible output power, while efficiency at maximum output power converges to Curzon-Ahlborn limit.

A hands-on laboratory experiment on concentrating solar power in a renewable energy sources course

At Hartnell Community College in Salinas, California, a renewable energy and energy efficiency course is a theory based course with several hands-on laboratory experiments. The course is designed for engineering and non-engineering students who are looking to transfer to a 4 year institution. Similar courses at 4 year universities, usually meet general education requirements. This course does not require any advanced mathematics or physics background. In order to enhance student learning in this course, we offered an additional hands-on laboratory experiment on concentrating solar power. The laboratory kit consisted of affordable and widely available materials that included 24 telescoping mirrors, stands, steel cup, thermometer, timer, and a cup of water. We asked the students to design, assemble, and test a central receiver concentrator with the goal to boil water contained in a steel cup. Upon achieving this goal, students were then asked to calculate the efficiency, define losses, and recommend ways of increasing efficiencies and therefore improving their systems through. The design challenge for the students is to determine the optimum position for the mirrors. Additionally, we asked the students to comment on the following; the effects of the time of the day and weather conditions, direct commercial applications, the process of generating electricity from solar concentrators. In order to record the level of improvement, each student was given the same questionnaire before and after completing the laboratory experiment. Upon grading the questionnaires, our assessment showed a 30% average on pre questionnaires scores and a 73% average on post questionnaire scores, suggesting a 43% improvement. This paper presents the results of our findings on performance improvements in further detail.

A retrospective study of a personal energy audit assignment in a renewable energy sources course

A retrospective study was conducted on analyzing student performances on the personal energy audit assignment in the renewable energy sources course. We analyzed student scores from 2006, 2009, and 2012 years respectively and categorized them by declared major. In this assignment, we asked our students to calculate the amount of energy that they consumed in one week of their life in college and identify the activities that consumed the largest amount of energy. We also asked them if they would consider any habit changes after completing this assignment. The goal of this assignment was to introduce non-science and engineering students to the concepts of energy, power, electricity, heat, temperature, first and second laws of thermodynamics, embedded energy and world energy consumption. The most common categories included; energy consumed in heating up water, transportation, and electricity. Additionally, on calculating energy used by electricity, we asked the students to confirm their calculations by reading labels and using Kill-a-Watt reading devices. In total, the scores of more than 500 students were evaluated. We found that the average of the scores increased by 19% between 2006 and 2012, and by 14% between 2009 and 2012. Since we used a similar rubric for grading, this shows that the students were able to perform better as we provided more step-by-step instructions, and streamlined the lectures on basic physics and energy concepts in the first three weeks of the course. Moreover, we grouped the students scores by their declared major. The four categories were engineering, social sciences, natural sciences, and undecided/other majors. We found that in 2006 the students with social science majors on average received the highest scores and in 2009 the students with natural science majors received the highest scores. Interestingly, the students with engineering majors showed the highest improvement in their scores between 2006 and 2012. The paper provides analysis of the student performances on this assignment and the overall effectiveness of this assignment.