February 16th, 2011: “Ultrafast Nanoscale Electrothermal Energy Conversion Devices and Measurements ” Dr. Ali Shakouri (slides)

Abstract: Energy consumption in our society is increasing rapidly. A significant fraction of the energy is lost in the form of heat. In this talk we introduce thermoelectric devices that allow direct conversion of heat into electricity. Novel metal-semiconductor nanocomposites are developed where the heat and charge transport are modified at the atomic level. Theory and experiment are compared for the case of embedded ErAs nanoparticles in a InGaAlAs semiconductor matrix. Potential to increase the energy conversion efficiency and bring the cost down to $0.1-0.2/W will be discussed. We also describe how similar principles can be used to make micro refrigerators on a chip with cooling power densities exceeding 500 watts per centimeter square.

Finally, we describe some recent advances in nanoscale thermal characterization and modeling. Thermoreflectance imaging is used to measure the transient temperature distribution in LDMOS power transistors at different ambient temperatures. Resolution down to 100ns in time, submicron spatial and 0.1C in temperature are achieved using megapixel CCDs. It is possible to measure both the temperature on top of the metal interconnect as well as at the transistors using near infrared illumination through the substrate. Recent results in transient thermal imaging of ESD protection devices, submicron interconnect vias, solar cells and LEDs are also briefly presented. Finally, in analogy with image blurring, a new technique is developed to estimate the temperature profile in integrated circuit chips with calculation speeds hundreds of times faster than the standard finite element methods.

Bio: Dr. Ali Shakouri is a Professor of Electrical Engineering at University of California Santa Cruz. He received his Ph.D. from the California Institute of Technology in 1995. His current research is on nanoscale heat and current transport in semiconductor devices, high resolution thermal imaging, micro refrigerators on a chip, and waste heat recovery. He is also working on a new sustainability curriculum in collaboration with colleagues in engineering and social sciences. He has initiated an international summer school on renewable energy sources in practice. He is the director of the Thermionic Energy Conversion center, a multi-university collaboration aiming to improve direct thermal to electric energy conversion technologies. He received the Packard Fellowship in Science and Engineering in 1999, the NSF Career award in 2000, and the UCSC School of Engineering FIRST Professor Award in 2004.

May 18th, 2011: “Capacitive Power Transfer for Contactless Charging” Mitchell Kline (slides)

Abstract: The simplicity and low cost of capacitive interfaces makes them very attractive for wireless charging stations. Major benefits include low electromagnetic radiation and the amenability of combined power and data transfer over the same interface. We present a capacitive power transfer circuit using series resonance that enables efficient high frequency, moderate voltage operation through soft-switching. We discuss limitations on the maximum efficiency for a given amount of coupling capacitance and present an optimal design which achieves this efficiency. Automatic tuning loops ensure the circuit operates at the optimum frequency and maximum efficiency over a wide range of coupling capacitance and load conditions.

An example interface achieves near 80% efficiency at 3.7 W with only 63 pF of coupling capacitance. An automatic tuning loop adjusts the frequency from 4.2 MHz down to 4 MHz to allow for 25% variation in the nominal coupling capacitance. The duty cycle is also automatically adjusted to maintain over 70% efficiency for light loads down to 0.3 W.

Bio: Mitchell graduated from Texas A&M University with a B.S. in Computer Engineering in 2008. He received his M.S. in Electrical Engineering from the University of California, Berkeley in 2010. His research interests include power electronics, integrated circuits, and MEMS sensor interfaces.

June 15th, 2011: “The Role of Power Electronics in the Future Smart Electric Grid” Ram Adapa (slides)

Abstract: Future Smart Electric Grid needs not only smart meters but also smart transmission and distribution technologies. Power Electronics will play an important role in the future smart transmission by enhancing the transmission capacity, reliability, and security. Currently transmission systems are becoming increasingly stressed because of growing demand and because of restrictions on building new lines. However, most high voltage transmission systems are operating below their thermal ratings due to such constraints as stability limits.

EPRI has been pioneering power electronic controllers (also known as FACTS – Flexible AC Transmission System technology) over the last two decades to make it possible to load lines at least for some contingencies up to their thermal limits without compromising system reliability. In order to understand what is required of the FACTS controllers, EPRI has been in the forefront by initiating more than fifteen system studies with different utilities to evaluate possible application of FACTS controllers. EPRI also took leadership role in demonstrating the FACTS technologies at various utilities – TCSC (Thyristor Controlled Series Capacitor) at BPA, STATCOM (Static Synchronous Compensator) at TVA, Unified Power Flow Controller at AEP, and CSC (Convertible Static Compensator) at NYPA.

FACTS technologies are offering competitive solutions to future smart transmission systems in terms of increased power transfers, improved system damping, and better system control. The application of FACTS devices are very much system dependent. It is important to consider both technical and economic considerations while evaluating FACTS options.

Bio: Dr. Ram Adapa is a Technical Leader in the Transmission and Substations area of the Power Delivery and Utilization Sector. His research activities focus on Fault Current Limiters, High Voltage Direct Current (HVDC) transmission, Flexible AC Transmission Systems (FACTS), dynamic circuit ratings to increase transmission capacity, and transmission system reliability performance metrics.

Dr. Adapa joined EPRI in 1989 as a Project Manager in the Power System Planning and Operations program. Later he became Product Line Leader for Transmission, Substations, and Grid Operations where he developed the research portfolio and business execution plans for the Grid Operations and Planning areas, a portfolio that focused on the needs of a deregulated utility environment. Some of the tools in this portfolio included market restructuring, transmission pricing, ancillary services, and security tools to maintain the reliability of the grid. Before joining EPRI, Dr. Adapa worked at McGraw-Edison Power Systems (presently known as Cooper Power Systems) as a Staff Engineer in the Systems Engineering Department.

Dr. Adapa received a BS degree in electrical engineering from Jawaharlal Nehru Technological University, India, an MS degree in electrical engineering from the Indian Institute of Technology, Kanpur, India and a PhD in electrical engineering from the University of Waterloo, Ontario, Canada. Dr. Adapa has been honored several times by the IEEE for his outstanding contributions to the profession. He has authored or coauthored more than 125 technical papers and is an IEEE Distinguished Lecturer. He is an individual member of CIGRE and a Registered Professional Engineer.

Sept. 21st, 2011: “A Better Place – The Storage Story” Hugh McDermott, Vice President Global Utilities & Energy (slides)

Abstract: Better Place is a global electric vehicle network operator and most known for the concept of battery switching to enable range extension and a “no-compromise” solution for drivers to make the switch to electric vehicles. What is less known publicly is the ability of BP to operate its networked charging infrastructure as a virtual generator and electric grid storage asset in coordinate with utility and grid operations. With little or no operating cost, utility integrated EV charging operations could be the “killer app” for utility-scale storage. This talk introduces Better Place from a utility operations perspective and will share how networked and centrally controlled EV charging infrastructure could become the “smartest part of the smart grid” for a generation to come.

Bio: Mr. McDermott is the Vice President Global Utilities & Energy where he leads Better Place utility partnering and energy services initiatives. Mr. McDermott possesses over 25 years of experience in energy technology and energy infrastructure development encompassing over 40 countries. His career background includes executive management, business development, and project management roles involving development of large energy infrastructure projects and clean technologies. Prior to joining Better Place, Mr. McDermott served as senior vice president of Nexant, where he was a founding management team member and lead the firms emerging markets and utility practices. Mr. McDermott is a frequent speaker in clean-tech and utility industry forums around the world and has served on numerous advisory panels including a recently appointment by US Secretary of Commerce to serve on the U.S. Industry Trade Advisory Committee on Energy in support of international trade development for the US energy industry. Mr. McDermott holds a B.S. in mechanical engineering in power systems from Virginia Tech.

Nov. 16, 2011: “The Impact of Microinverters in Photovoltaic Systems” Brandon Pierquet, Senior Design Engineer, Enphase Energy (slides)

Abstract: Interest in photovoltaic (PV) systems has increased significantly over the past decade, in both the public and private sector. With the cost of photovoltaic modules dropping, and increasing energy costs, many installations are proving to be a fiscal benefit. In traditional installations, a single central dc-ac inverter is fed by a series connected string of modules; mismatch between the ideal maximum power point tracking (MPPT) of each module reduces the realisable energy capture of the system. A new style of inverter, often referred to as a microinverter, provides the MPPT and dc-ac conversion at each PV module, allowing direct connection to the grid.

This talk will cover the trade-offs presented by microinverters in various system configurations, from kilowatt sized residential systems through multi-megawatt utility scale installations. Focus will be placed on the challenges faced in cost, efficiency, reliability, safety, and overall market acceptance. Some depth into the common power electronic topologies and control algorithms will be covered, along with grid interconnection challenges and standards compliance issues.

Bio: Dr. Brandon J. Pierquet is currently a Senior Design Engineer at Enphase Energy, where he is working on the development of new microinverter implementations and control strategies. He received his Ph.D. and S.M. degrees in from the Massachusetts Institute of Technology in 2011 and 2006 respectively, and his B.S. degree from the University of Wisconsin-Madison in 2004, all in electrical engineering. His research interests include resonant power conversion for ac systems, multi-port converter topologies, embedded system control, and solar energy applications.