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Abstracts

Forum on Research and Organizational Efforts in Sustainability and Green Technology

Panelists

Dan Davids
HMC Alum and President of Plug In America
Jeffrey Byron
Commissioner of the California Energy Commission
Devon Hartman
Co-founder HartmanBaldwin Design/Build
Freeman Allen
Professor Emeritus of Chemistry Pomona and Representative from Sustainable Claremont
Richard Elderkin
Professor of Mathematics, Pomona College
Richard Haskell
Professor of Physics and Director of the Center for Environmental Studies, Harvey Mudd College

Examples of questions that will be addressed:

  1. Given a limited amount of resources to invest in sustainability (such as time and money), what are the most important ways to spend them? For example, if you wanted to donate $1000 or $1,000,000? Or if you wanted to volunteer 3 hours per month?
  2. If you are a student, what are the most important things you can do to prepare yourself for a career in sustainability and green technology?
  3. What are some of the most exciting cutting edge developments happening now?
  4. What are the most important behaviors people should engage in to help sustainability efforts (recycling, water conservation, less driving, buy local...)?

Harry Atwater: Light–Matter Interactions for Solar Energy Conversion

Solar energy is currently enjoying substantial growth and investment, owing to worldwide sensitivity to energy security and the importance of renewable energy as a means to mitigate carbon emissions.

In this talk I will describe approaches to control of light-matter interactions leading to enhanced absorption in solar photovoltaic structures. Conventionally, it is thought that semiconductor photovoltaic absorbers should have a physical thickness comparable to the “optical thickness” to enable nearly complete light absorption and photocarrier current collection.

Solar cell design and material synthesis considerations are strongly dictated by this simple optical thickness requirement. Dramatically reducing the absorber layer thickness or volume confers several fundamental and practical benefits, including increased open circuit voltage and conversion efficiency, and also expansion of the scope and quality of absorber materials that are suitable for photovoltaic devices by, for example, enabling efficient photocarrier collection across short distances in low dimensional structures. Semiconductor wire array solar cells have a geometry that both facilitates photogenerated carrier collection and enhanced light absorption; results for enhanced optical absorption and carrier collection in Si wire array solar cells will be given, and limits to enhanced absorption will be explored.

To date, little systematic thought has been given to the question of how plasmonic and metamaterial structures might be exploited to advantage in photovoltaics. I will describe design approaches using metallic nanostructures to excite localized and propagating surface plasmons which can dramatically increase the optical path length in thin active photovoltaic layers to enhance overall photoabsorption. Examples of plasmon-enhanced absorption in thin Si, GaAs and InGaN solar cells will be described. Future metamaterial optical design directions for dramatic reduction of solar cell active volume will be outlined.

Kenneth M. Golden: “Climate Change and the Mathematics of Transport in Sea Ice”

Sea ice is both an indicator and agent of climate change. It also hosts extensive algal and bacterial communities, which sustain life in the polar oceans. The dramatic decline of the summer Arctic ice pack is perhaps the most visible, large-scale change on Earth's surface in recent years. Most global climate models, however, have underestimated this decline, while the Antarctic sea-ice pack has increased. We will discuss some key sea ice processes which must be better represented in climate models, such as snow-ice formation and the evolution of melt ponds and ice pack reflectance. Recent mathematical advances in characterizing the porous microstructure of sea ice, and fluid flow through it, shed new light on these processes. Our work will help in predicting and monitoring the impact of global warming on sea ice and the response of polar ecosystems. Video from a 2007 Antarctic expedition where we measured fluid and electrical transport in sea ice will be shown.

Julie K. Lundquist: “Harnessing the Power of the Wind”

Wind energy offers the promise of a robust and inexhaustible domestic energy source. Not only do wind turbines provide power with minimal greenhouse gas emissions, but virtually no fresh water is required for power production. Wind energy capacity in the U.S. now produces enough electricity to power the equivalent of approximately 7 million households (American Wind Energy Association, 2009). Despite impressive recent growth, wind energy still constitutes less than 2% of US electricity sources. Several attainable technical challenges must be surmounted if electricity generated by wind is to provide a significant source of domestic power.

This presentation will highlight the mathematical aspects of some of these challenges. The integration of large fractions of fluctuating quantities of renewable energy into power grids required accurate prediction of power availability. These predictions in turn depend on accurate forecasts of wind and atmospheric conditions, nuanced understanding of the impacts of complex terrain on flow and turbulence in the lower atmosphere, and even delineation of the impacts of turbines on each other through turbulent wake effects. As society considers large-scale implementation of wind energy, an assessment of the local environmental impacts of turbines will also be required.

Ron Lloyd: “Modeling Problems in the Green Economy”

Any problem that requires new ways of thinking in order to be solved, also requires breakouts in the analytical models used to evaluate potential solutions. A green economy challenges engineers with converting one form of energy—sunlight, wind, waves, heat—into useful forms with reliable and economically viable transformation technologies. This talk will focus on three examples from the green economy that require new analytical models to properly evaluate their technical and economic viability.

  1. Electric vehicles—Conventional internal combustion engines operate at 20–25% efficiencies, with a tremendous amount of waste heat to shed. Battery electric vehicles, while more efficient, have very limited on-board energy storage and most ancillary systems are a load on the vehicle's battery system. Vehicle energy use models need a major overhaul to support electric vehicle development.
  2. Energy data load and storage—The confluence of Smart Grid, telematics, distributed energy, wireless technologies, and increasing capacities for network traffic and data storage create an explosion of time-sequenced data to be stored and mined in the current and future economies. Predicting storage requirements and system load from data transfer and user mining is an increasingly difficult challenge.
  3. Sustainability—Macroeconomics focuses on large-scale societal systems driving the economy. On a global scale, this presumes that economic health is predicated on growth. Constant growth, if predicated on resource consumption, is inconsistent with most views of “sustainability”—a steady state energy system, with finite resources in the biosphere. Reconciling these two fundamental viewpoints is one of the most important macro problems of 21st century society.