Precourt Institute for

Energy

Precourt Energy

Efficiency Center

TomKat Center for

Sustainable Energy

Seed Grant Portfolio

2010-2013

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Precourt Institute for Energy 2010

Better Models for Applying Hydraulic Fracturing to Geothermal Systems

Roland Horne, Energy Resources Engineering; David Pollard, Geological & Environmental Sciences

This award-winning research could lead to overturning 25 years of conventional thinking about the

basic mechanism of hydraulic fracturing, or stimulation, for enhanced geothermal systems, (EGS).

Instead of EGS stimulation inducing slip of preexisting fractures, this project and its follow-on work

suggests that in many cases extensive propagation of new fractures occurs. This has major

implications for site selection, design, economics and safety. The student this grant supported, now

in a tenure-track position at the University of Texas, developed a computational model for EGS. The

model fully describes the stresses induced by fracturing in complex networks with thousands of

fractures in a reasonable amount of time on a single computer. The model demonstrated how

different mechanisms can control stimulation, depending on geological setting. The researchers

also showed how field measurements can diagnose the best stimulation mechanisms. The research

should lead to greater safety of fracturing for both geothermal and natural gas. The model couples

fluid flow with highly realistic rate and state friction earthquake modeling, the first of its kind. The

model identified two strategies that could reduce the size of the induced events. Continued work at

Stanford and Texas includes development of 3D software and application to natural gas production,

which has drawn interest from four gas companies and Schlumberger.

Developing Surface-Modified Metal Electrodes for Turning CO2 Into Fuel

Matthew Kanan, Chemistry

This project developed surface-modified metal electrodes to improve the efficiency of electricity to

turn CO2 and water into a carbon-based fuel. Researchers then found that copper metal particles

derived from a copper oxide layer dramatically improved selectivity, stability and energetic

efficiency for CO2 reduction compared to all other copper materials that had been studied to date.

(Copper is the most intensively studied electrode for CO2 reduction, and no substantive

improvement to its catalytic properties had been made previously.) The project then experimented

with “oxide-derived” metal electrodes for three other metals: gold, silver and palladium. Each

greatly improved CO2 reduction properties relative to their standard metal electrode counterparts.

This work continues under a three-year grant by the Global Climate & Energy Project. Researchers

are analyzing the structural features of the new copper electrode, exploring its potential use in fuel

cells, and developing strategies for producing a liquid fuel from the CO2 reduction.

Solar Fuels: Using Composite Metal/Oxide/Semiconductor Anodes to Split Water

Paul McIntyre, Materials Science & Engineering; Christopher Chidsey, Chemistry

This work found a solution to a major technical problem for using solar power to produce hydrogen

fuel from water. The research resulted in publication in Nature Materials, a U.S. patent, a pending

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patent, and a three-year research project selected for funding by the Global Climate & Energy

Project a year ago. The project discovered that ultra-thin titanium oxide layers permit electronic

carrier movement while protecting high-quality semiconductors during water splitting.

Photovoltaic electrodes that use sunlight to help drive this reaction are usually made of silicon,

which corrodes and fails when exposed to the oxygen, as do other high-quality semiconductors.

This research used atomic layer deposition to coat silicon with ultrathin and pinhole-free layers of

titanium dioxide and iridium. The result was a corrosion-resistant and efficient solar cell for

splitting water far exceeding the performance of previously reported silicon photovoltaic anodes

for water splitting. The protected silicon anode may prove to have other possible applications, such

as producing other kinds of fuels by using other feed stocks, possibly even carbon dioxide.

Using Paper- and Cotton-Based Materials for Grid-Scale Energy Storage

Yi Cui, Materials Science & Engineering; Zhenan Bao, Chemical Engineering

The researchers made inexpensive, high-performance supercapacitors by coating renewable

resources—paper and cotton—with nanoscale conductive materials. Supercapacitors hold high

charges temporarily and can smooth

power flows on transmission

systems, considered a growing need

as wind and solar power become

greater portions of electricity supply.

In this project, graphene, which is a

one-atom-thick highly conductive

sheet of bonded carbon, was

combined with manganese dioxide and a conducting polymer. This was applied to a textile to

produce a high capacity, high power supercapacitor. Second, the investigators showed that

excellent supercapacitors can be fabricated with a graphite pencil in a precise pattern on paper. The

shear peeling of graphite produces multi-layer graphenes with a high proportion of conductive

edge structures. These supercapacitors show stable long-cycling performance and an area

capacitance much higher than previously reported. The paper supercapacitors demonstrated here

could lead to the development of all-paper electronics that are low cost and highly versatile. On the

side, the project also developed a novel hydrogel material for energy storage.

Development of a New High-Temperature Proton Exchange Membrane for Fuel Cells

Curtis Frank, Chemical Engineering; Michael Toney, SLAC

This project began the development of a low-cost, high-performance alkaline exchange membrane

to replace the conventional water-based membrane for use in fuel cells. Previous alkaline exchange

membrane technologies degraded and conducted hydroxide ions poorly. After initial study, this

project developed a new membrane material that does not rely on water for proton conduction. The

researchers used a copolymer structure composed of water-attracting and water-repulsing micro-

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sections. The hydrophobicity mismatch between the polysulfone and the polyethylene glycol was

expected to drive micro-phase separation of the membrane into water-rich, conductive domains.

The project demonstrated the concept, showing conductivity in the first phase of development in

line with expectations. Further refinement of the membrane material continues in a follow-on

project with Thomas Jaramillo, (Chemical Engineering). The follow-on project, funded by the

TomKat Center, is developing a fuel cell that can store electricity by producing hydrogen from

water and later produce power when the hydrogen is allowed to recombine to make water.

Potentially Low-Cost Crystalline III-V Thin Film High Efficiency Solar Cells

Jim Plummer, Electrical Engineering

Solar photovoltaic cells made from compound semiconductors known as “III-V,” like gallium

arsenide, are comparatively efficient but expensive. This project aimed to dramatically improve the

cost/performance tradeoff of III-V photovoltaics with rapid melt growth technology, which was

developed at Stanford for high performance computing. This project concluded that the rapid melt

growth approach is likely more difficult to use to implement full wafer III-V photovoltaic devices

than had been hoped. However, the results the project obtained are exciting in other applications.

The III-V materials the researchers were able to integrate successfully on silicon using rapid melt

growth have drawn great interest for integrated circuits. The work enabled by Precourt Institute

funding has led to follow-on funding from Intel Corp. to pursue these applications.

2011

Novel Hybrid Materials of Carbon for Lithium-Air Batteries

Hongjie Dai, Chemistry

This project has successfully developed several novel materials for metal-air batteries and other

types of electrocatalysts that could be useful in energy generally. First, researchers developed

multi-walled carbon nanotubes riddled with defects and impurities on the outside to replace

expensive platinum and palladium catalysts used in lithium-air batteries, and other types of

batteries not in the original proposal. Then the researchers invented single-use and rechargeable

zinc-air batteries using the carbon nanotube catalyst for oxygen reduction and a nickel-iron catalyst

for the cathode. These catalysts exhibited higher catalytic activity and durability in concentrated

alkaline electrolytes than precious metal catalysts. The single-use battery showed high discharge

peak power density, current density and energy density. The rechargeable battery in a tri-electrode

configuration exhibited an unprecedented small charge/discharge voltage polarization, high

reversibility and stability. This work may lead to zinc-air batteries for electrical vehicles. Second,

the investigators chemically synthesized a nickel−iron carbon nanotube complex as a catalyst for

the electrochemical oxidation of water. It demonstrated higher catalytic activity and stability than

the benchmark commercial iridium-based catalysts for this purpose. This was a breakthrough in

the search for a non-precious metal catalyst for the electrochemical oxidation of water. This project

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has resulted in additional funding from Amperex Technology Ltd., (a major battery company), and a

grant from GCEP to further develop the rechargeable zinc-air battery. The primary investigator is

discussing the potential licensing of resulting battery materials to a U.S. battery company.

Raising Efficiency in Dye-Sensitized Solar Cells at Electrode-Electrolyte Interface

Daniel Stack, Chemistry; Michael McGehee, Materials Science & Engineering

Dye-sensitized solar cells use a special dye sandwiched between two semiconductors to convert

sunlight into electricity. To make the process more efficient, the researchers have synthesized new

dyes to better keep the negative charge carriers in one semiconductor away from the positive

charge carriers in the other semiconductor. Since the last update, two different dye-sensitized solar

cells with the same absorbing dye, yet chemically assembled by a different sequence of steps,

provide a 30 percent enhanced efficiency. Extension of these principles to more efficient dyes is the

investigators current objective.

Designing Micro-Combined Cooling, Heating and Power

Lambertus Hesselink, Electrical Engineering

This project is developing a novel, highly efficient and economical energy system combining

heating, cooling and electricity in a small unit for residences or small businesses. The research team

has modeled a Stirling thermo acoustic heat engine and is evaluating fundamental system

performance issues through the use of three-dimensional simulations. Researchers have identified

a promising system architecture that may be mass manufactured at low cost. They have raised

significant funding for further research and commercial development.

2012

Polymer Gels for High-Performance Batteries

Zhenan Bao, Chemical Engineering; Yi Cui, Materials Science & Engineering/SLAC-Photon Science

This project is developing specially designed nanostructured polymers for a new generation of

battery materials. The project has three main tasks. First, the

researchers developed an electrode of silicon nanoparticles

suspended in a highly conducting polymer hydrogel. Silicon can

hold 10 times the charge of the common graphite electrode used

in lithium-ion batteries today, but silicon materials have not

been created to overcome the rapid expansion and contraction

silicon undergoes during charging and discharging. Second, the

research team is developing self-healing polymers, which will

address the capacity decline of new battery materials due to

volume change and fracture. Finally, they will develop all-

Silicon nanoparticles in a three-dimensional

conductive polymer gel network.

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polymer batteries: anodes, cathodes and electrolytes. Such batteries will be flexible and stretchable

for novel form factors, and could be manufactured at very low cost, making them potentially

feasible for grid storage requirements. Ultimately, researchers expect this project to evolve into a

new world-class energy storage research program at Stanford.

Hybrid Minerals for Reversible Capture of Atmospheric CO2

Hemamala Karunadasa, Chemistry

An unexplored and potentially inexpensive approach to capturing atmospheric CO2 may be to

develop organic-inorganic hybrid materials to exploit electric potential swing cycles. This study is

using metals to make synthetic materials with electronic properties that enable the controlled

capture and release of CO2. The material needs to be both porous and conductive, two properties

that typically arise from diametrically opposite structures. A hybrid material could meet both

requirements. The project has started with hybrid perovskites, which have been successfully used

in electronics with demonstrated ability to tune their transport properties. The successful

modification of hybrid perovskites for conductivity, porosity and inclusion of substrate binding

sites could open this class of materials to a wide range of applications in the fields of sustainable

energy and pollution management.

Water Splitting Using an Inorganic Proton-Conducting Membrane

William Chueh, Materials Science & Engineering/Precourt Institute; Nick Melosh, Materials Science &

Engineering

Most solar-driven water-splitting experiments are conducted in photo-electrochemical cells at

room temperature using either a liquid or a polymer solid electrolyte. This project is developing a

water-splitting device that operates at high temperatures (up to 400° C) by replacing these

conventional electrolytes with a

hydrogen-conducting ceramic

membrane. The higher temperature

can lower the energy required to

split water, and it provides better

mechanical and chemical stability.

The researchers are building a

proof-of-concept photo-

electrochemical cell using a

perovskite-oxide-based proton

conductor, operating at about 300° C. The solid-state approach ensures the rapid removal of

hydrogen gas molecules from the photo-electrode surface, suppressing unwanted recombination of

the water molecules. Researchers are examining and engineering the interface between various

earth-abundant light absorbers and proton-conducting membranes.

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Ultrathin Light Absorbers for Solar Cells

Stacey Bent, Chemical Engineering; Mark Brongersma, Materials Science & Engineering

One way to lower the cost of solar power is to dramatically reduce the thickness of light-absorbing

layers in solar cells. This project is addressing the fundamental question of what minimum amount

of material is required to absorb most of the light incident in the useful part of the solar spectrum.

Atomic layer deposition is being used to create nanocomposites combining plasmonic nanoparticles

with ultrathin semiconductor layers and light trapping structures to generate the right conditions

for maximum light absorption. This proof of concept demonstration could potentially reduce the

absorber layer thickness 100-fold compared to conventional thin-film solar cells. The results could

lead to production of low cost, efficient solar cells using minimal materials.

2013

Functionalized Graphene-Platinum Composites for Fuel Cells

David Goldhaber-Gordon, Physics; Fritz Prinz, Mechanical Engineering and Materials Science

The investigators plan to use a new material system they have recently developed to reduce

dramatically the amount of expensive platinum needed in fuel cells. They can grow dispersed

platinum nanoparticles on graphene, (one-atom thick sheets of carbon), without damaging the

electrical or structural properties of the graphene. This may enable catalysis of key energy

conversion reactions for fuel cells with high efficiency, in addition to reducing platinum use.

Self-Regenerating Fuel Cells Running on Natural Gas

Robert Sinclair and William C. Chueh, Materials Science & Engineering

Certain types of fuel cells can convert natural gas into electricity and back again with very high

efficiency, eliminating the traditional fuel cell’s production of hydrogen from natural gas as the

energy source. However, the catalysts used by such fuel cells degrade quickly, so the cells stop

working after a few years. Attempts to develop self-regenerating catalysts for these devices have

fallen short. Using Stanford’s Titan environmental transmission electron microscope—the only one

in the United States—this project seeks to illuminate the fundamental chemical and structural

transformations needed for developing self-regenerating catalysts for elevated-temperature

ceramic fuel cells and electrolysis cells.

An Electricity/Carbon Market Simulation Incorporating Renewables:

Mark C. Thurber, Program on Energy & Sustainable Development; Frank A. Wolak, Economics.

Research using games often reveals effects of human actors in economic outcomes that standard

economic models do not foresee. In a Graduate School of Business class last year, this project’s

investigators created a simulation in which teams of students tried to maximize profits from

portfolios of power plants operating in California’s markets for electricity and CO2 emission

permits. Among other surprises, they found that in some situations power producers benefited by

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boosting emission permit prices, which raised electricity costs dramatically. This new project will

further develop the game by adding non-hydroelectric renewable power plants into the market,

reflecting the state requirement that utilities obtain a certain amount of their electricity from

renewable sources. The refined version of the game will also let consumers respond to higher

prices more quickly. The researchers will then run multiple, controlled experiments involving a

broader swath of the Stanford students playing the game. The project could produce valuable

insights for policymakers, while providing a unique educational experience for students.

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Precourt Energy Efficiency Center 2010

Paying for Good Deeds: Using Financial Incentives to Achieve Energy Efficiency

Matthew Harding, Economics

This project helped establish several fundamental findings in the developing research area of

energy and behavior. The researchers conducted experiments with utility customers in Chicago and

Massachusetts to determine the extent to which financial incentives, and reward schemes in

particular, can achieve energy efficiency. Partnering with a leading energy efficiency company,

Efficiency 2.0, the researchers found that some behavioral nudges, when well designed, can cut

energy consumption significantly. Goal setting was particularly potent. In Chicago, households

saved on average about 8 percent immediately after adoption, but savings over a 12 months period

slipped to just 2-3 percent. Households that chose realistic goals of 1-15 percent reduction, saved

almost 10 percent, and the effect persisted. Households that chose unrealistic goals saved for a few

months, then gave up. Families that

joined the program for the financial

incentives saved only for a limited

period of time, though this may

have been due to poor construction

of the rewards. The experiment in

Massachusetts showed that giving

families information about how

they can save energy is not

sufficient for significant savings.

Also, combining goal setting and

neighbor comparisons worked very well. Rank comparisons did not work. With support from

NRDC, this work has continued in a large program implemented by OPower and Facebook.

Reducing Barriers to Diffusion of Energy-Saving Technologies in the Building Industry

Raymond Levitt, Civil & Environmental Engineering; Erica Plambeck, Business

Up to 34 percent of energy used in buildings is wasted, despite available technologies. This project

identified the key organizational, inter-organizational and industry barriers to widespread

adoption of energy-saving technologies in the building industry. The project’s case study of the

company ZETA Communities documented examples of government regulations and incentives, as

well as corporate strategies, that have successfully overcome these barriers. ZETA Communities

integrates architecture, engineering, functional construction to produce zero-net energy homes for

15–20 percent less cost than conventional homes. The project also developed preliminary

hypotheses about strategic and policy interventions that can overcome these barriers. The project’s

results showed that integration of supply chains from manufacture through maintenance can help

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overcome the barriers of the decentralized U.S. building industry. This represents a business

opportunity for penetrating mature markets with integral innovations. The work also found that

modular innovations are implemented almost three times as often as integral innovations. In

follow-on work, researchers are investigating strategies to increase implementation of integral

innovations. They are also working with Johnson Controls’ booming energy efficiency division.

Improving Airflow Parameterizations in Energy Simulation Tools

Gianluca Iaccarino, Mechanical Engineering; Martin Fischer, Civil & Environmental Engineering

This project developed a building energy model using the current best practices in computational

fluid dynamics, coupled with heat transfer information from an existing energy simulation tool. The

project also applied the tool to Stanford’s Y2E2 building’s nighttime air purge, which was

underperforming expectations. Initially,

researchers found that cost savings for

cooling Y2E2 could be increased from

15 percent to 20 percent savings by

modifying the night purge algorithm.

Ultimately the study found that detailed

computational fluid dynamics

simulations can provide a flexible tool to

parameterize geometry and flow-

specific coefficients, specifically those for discharge though openings. This study found that the

popular EnergyPlus software used a formula to calculate the effective area of pivoted windows that

tended to underestimate the flow rate through such openings by up to 50 percent. A modification to

this expression was proposed that takes into account the airflow through the sides as well as the

bottom of an open, horizontally-pivoted window. Both computational fluid dynamics results and

data from window manufacturers agree well with the modified formula.

Santa Clara County Jail—Energy Efficiency Retrofit, Monitoring, and Modeling

Martin Fischer, Civil & Environmental Engineering

Santa Clara County Jail is one of four buildings studied by PEEC to compare simulation models of

energy use with actual outcomes in order to improve the models. This project dealt with the more

complicated and less well understood modeling of retrofits. The researchers collaborated with the

jail on energy retrofits—within a modest budget—to reduce the operating costs of the jail and its

greenhouse gas emissions. The team recommended a set of cost-effective efficiency improvements

after extensively monitoring the building’s energy consumption, analyzing historical data and

simulating 30 possible retrofits. In a smaller, follow-on project funded by PEEC, investigators are

analyzing outcomes of the retrofits made and comparing them with earlier simulations.

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2012

Experiments with Appliance Choice

Brian Knutson, Psychology

This study is examining whether some groups of consumers alter their decision-making process

when buying major household appliances due to behavioral nudges, such as eco-labeling. The study

is characterizing consumer classes and monitoring neural activity in each group via brain imaging

with functional magnetic resonance imaging. Observations of shifts in the manner of decision

processing would imply a need to reassess policies for behavioral nudges. Current approaches

assume that nudges do not alter the decision-making process a consumer employs, for example,

switching attention from financial to environmental concerns. If the work finds that some

consumers do alter their decision-making process in response to nudges, behavioral economic

policy design and analysis will need to consider the impact of policy on the distribution of decision-

making processes and the normative implications of subsequent choices. Moreover, if differences

are found between the neural structures recruited for financial decision-making and those for

appliance decision-making, this work would provide insight into the unique cognitive or affective

processes engaged when consumers are making appliance purchase decisions.

A Mechanism for Electric Vehicles to Support the Power Grid of the Future

Yinyu Ye, Management Science & Engineering

Plug-in electric vehicles likely will be integral to the reliability of the future power grid for two main

reasons. Charging stations at home and work will create the ability to shift significant power

demand in time when needed. Also, in the future these vehicles likely will be able to transmit

electricity back to the grid, creating a network of

millions of distributed batteries for supply when

needed. However, realizing this vision requires

overcoming several barriers. Various technologies

still need development, as does the optimal market

mechanism to organize this distributed trading.

New business and service industries may be

needed. This project aims to address these

challenges. In particular, the researchers are

building an automated demand response

mechanism for a fleet of electric vehicles. A demand-response aggregator, a new kind of energy

service company, will communicate energy needs between the fleet and the utility, and it will

regulate electricity use. The aggregator being developed uses a simple price equilibrium to instantly

and automatically determine feasible energy exchange schedules for tens of thousands of vehicles

as they plug-in to the grid, based only on a relatively small amount of aggregated historical data.

Such a system would not only benefit grid stability, but reduce charging costs for consumers.

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The Dynamic Effects of the Light Bulb Ban

Mar Reguant and Lanier Benkard, Business

Economists have long pondered “the light bulb puzzle,” which asks why consumers appear to make

poor financial decisions when continuing to use inefficient light bulbs. However, new regulations

effectively ban incandescent light bulbs in much of the world, and lighting alternatives—compact

fluorescent, LED, halogen incandescent—have flourished. The researchers are exploring whether

the new choices cause consumers to consider not only immediate prices but long-term costs. Or will

the light bulb puzzle persist? On the producer side, this project is examining whether the

incandescent bans were essential to the spurt in lighting innovation and whether previous

manufacturer inertia was due to consumer inattention. The project’s findings may illuminate the

role of government policy in spurring innovation. The researchers are developing an econometric

dynamic industry model that takes into account the interaction of consumers and firms to quantify

the effects of various policies in a comprehensive fashion.

2013

Trip Estimation Techniques to Better Manage Hybrid Vehicle Batteries:

John D. Fox, SLAC; William Dally, Computer Science; Jonathan Levav, Business.

The environmental and economic value of hybrid vehicles is maximized by using the least amount

of fossil fuel and exhausting battery power before recharging. Most hybrid cars use simple

protocols for managing the battery. This project will develop techniques to predict the most

probable trip a car is taking while the vehicle is in motion based on the driver, time of day, starting

point, and other parameters. Such predictive ability combined with mapping of charging stations

and real-time traffic data could direct the hybrid motor to use its electric charge optimally.

Improving Predictions of the Efficiency of Natural Ventilation in Buildings

Gianluca Iaccarino, Mechanical Engineering; Martin Fisher, Civil & Environmental Engineering

Designing buildings that rely on natural ventilation for temperature control is a relatively new

science. Due to limited analytical tools, such buildings to date have too often resulted in

uncomfortable occupants. This work seeks to improve the design and operation of such buildings to

yield increased overall building efficiency (in mixed-mode ventilation) without sacrificing comfort.

The researchers will use high-fidelity simulations and rigorous sensitivity analysis based on

available weather and building data to inform designers on the amount of time in a year the

building is not operating in the mode expected. The tools developed will also evaluate and

incorporate mitigation strategies, and identify what to monitor in order to assure building

performance.

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Better Decision Making for Policies and Programs to Reduce Electricity Use

Roy Pea, Education; Michael Bernstein, Computer Science; Martha Russell, H-STAR

This project seeks to aid decision making in energy-efficiency initiatives from government policies

to business campaigns. Researchers will first create a crowd-sourced process for feedback on

critical assumptions in residential energy conservation. Then they will develop analytics and

metrics to identify critical changes in factors influencing public opinion regarding efficiency

technologies and their adoption. The end product will also include visualizations of the data for

easy access by targeted decision makers and group processes for augmented decision systems.

Visualization of smart meter data for critical peak pricing for commercial energy consumers

Ram Rajagopal, Civil & Environmental Engineering; June A. Flora, H-STAR

Most electric utilities have multiple programs offering customers

financial incentives for using electricity efficiently and reducing use

when power demand is very high. But utilities often do not know what

programs are effective, or how to market the specific incentives to the

customers most likely to respond. Working with PG&E, the

investigators have developed a system using data from 200,000 smart

meters to identify residential customers who are good targets for such

incentives. This new project will extend their system to 2,000 small and medium business

customers of PG&E and, to a lesser extent, the Los Angeles Department of Water & Power. In

addition to its data analysis component, the system includes a visualization and interaction front

end for engaging selected users via email, the Internet and print.

Efficiency and Group Behavior in Power Distribution Networks

Ramesh Johari, Management Science & Engineering; Ram Rajagopal, Civil & Environmental

Engineering

The electricity system of the future is expected to include many local energy devices that can either

generate electricity, like rooftop solar panels, or store energy, like electric cars. Such distributed

energy resources could reduce power losses in the traditional central power plant paradigm and

reduce purchases of backup power supplies. A potential complication to the hoped-for gains in

efficiency, however, is that the owners of these resources—homeowners and small businesses—

likely will form groups in order to have more leverage in negotiating deals with their local utilities.

Researchers in this project will investigate the nature of such “micro grids” likely form, in terms of

size and geographical proximity of the members, as well as whether such groups will improve the

overall efficiency of the power system. The researchers will also study whether the efficient

operation of a network with many distributed energy resources requires a communication system

much more robust than what the researchers see emerging currently.

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TomKat Center for Sustainable Energy

2010 - Smart Grid

GridSpice: A Virtual Platform for Modeling, Analysis, and Optimization of the Smart Grid

Abbas El Gamal, Stephen Boyd, Benjamin Van Roy, Amit Narayan and Dan O'Neill, Electrical

Engineering

The electrical network of the future will have many devices, such as generators, fixed demand,

flexible demand and storage devices, and each device will have its own objective and dynamic

limitations. This project supported the development of GridSpice, an open-source, cloud-based

platform for modeling and simulation of the smart grid. GridSpice was developed in collaboration

with industry mentors at Cisco Systems. This research project also developed a messaging system

for quickly optimizing a dynamic system based on a

great deal of data. Maximizing the efficiency of the

total network over an instantaneous time horizon,

subject to device and line constraints, is a large

optimization problem. Stephen Boyd’s research group

developed a decentralized method for solving this

problem. At each step, each device exchanges simple

messages with its neighbors in the network and then

solves its own optimization problem, minimizing its

own objective function, augmented by a term

determined by the messages it has received. The

method is completely decentralized, and needs no

global coordination other than synchronizing

iteration. The method can solve a problem with over

10 million variables in 17 minutes for a serial implementation; with decentralized computing, the

solve time would be less than one second. More than 20 groups from industry and other academic

institutions have submitted project proposals to the researchers to be considered for use in the

next version of GridSpice. The research team is adding several applications to the platform, such as

energy storage and electric vehicles, and they are standardizing the software to the electric power

industry’s Common Information Model.

Improving Wind Power Operations with Sensing, Statistics and Control

Ram Rajagopal, Civil & Environmental Engineering

This project developed three approaches to enable high penetration of wind energy by reducing the

planning, safety and operating costs due to wind’s uncertainty. The three approaches developed:

novel control for power dispatch by the system operator, improved forecast algorithms for wind

power generation and improved sensing for wind energy generators. The dispatch algorithm

researchers developed reduces the costs of integrating wind power up to 60 percent by using

forecast information appropriately. The algorithm addresses the full market model and includes the

possibility of network congestion. It can be directly implemented in existing system operator

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software. The forecasting method developed is able to predict wind generation with reasonable

accuracy for the next day without complex computing tools. The researchers have also developed

the first wind ramp detection and characterization methodology to improve dispatch against large

swings in wind production. Finally, the researchers began development of an airborne wind sensor

that is less expensive than those currently used because it does not require a tower. The concept is

that these sensors can be deployed in greater quantity and at greater distances from the wind

power farms to more accurately forecast production. The researchers have worked with the

California Independent System Operator and other grid operators to implement their research.

Facilitating Renewable Energy in a Wholesale Market by Expanding Transmission

Frank Wolak, Economics; Stephen Boyd, Electrical Engineering; Mark Thurber, Program on Energy &

Sustainable Development

This work quantified the economic benefits and costs of expanding a transmission system operating

in a wholesale power market environment. The work found that transmission expansions increase

competition among power suppliers, who offer electricity to the wholesale market at prices closer

to their variable costs of production. The researchers also performed a cost/benefit analysis for

Alberta’s wholesale power market. The analysis found positive net benefits for transmission

upgrades that would not be built without accounting for these financial benefits. Also, the

researchers found that the intermittent nature of renewable resources such as wind and solar

energy increases the expected magnitude of the competitiveness benefits. However, as the share of

renewable resources on a given system increases economically, beneficial expansions may not be

undertaken if this source of economic benefits is not accounted for. The researchers also examined

a zonal-pricing market where transmission congestion is explicitly priced. Using data from

Australia’s national power market, they implemented an enhanced version of the methodology to

quantify the competitiveness benefits of several proposed transmission expansions in Australia.

Analysis and Control of Smart Electrical Distribution Systems

Sanjay Lall, Aeronautics & Astronautics and Electrical Engineering; Dimitry Gorinevsky, Electrical

Engineering

This project questioned whether a high penetration of distributed generation, like rooftop solar

installations, would make the electrical distribution system unreliable or unstable. The answer,

thankfully, is “no.” The researchers’ model found that for tie-in inverter connection of distributed

generation, the transient oscillations can remain stable and grid frequency disturbances will not be

amplified, so long as the inverter controller is well-tuned. This conclusion holds for a broad range of

parameter values explored in this work, including the percentage of the distributed generation and

transmission line impedance. The team also studied statistical monitoring in power-generating gas

turbines. They developed scalable algorithms that can process the large amount of data generated

by such equipment and flag the anomalous units. Applying statistical process control methodology

to the anomalies could improve reliability and energy efficiency, as well as reduce maintenance

costs. The initial results were very promising. Both efforts stirred interest at GE Energy, and follow-

on research discussions are underway.

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2011 - Large-Scale Solar Power

Storing Electricity: An Alkaline Exchange Membrane Unitized Regenerative Fuel Cell

Thomas Jaramillo and Curtis Frank, Chemical Engineering

The device the researchers are developing is an alkaline anion exchange membrane unitized

regenerative fuel cell (AEM-URFC). Such a device has never been demonstrated previously. The

AEM-URFC uses renewable energy to split water into H2 and O2 when renewable electricity is

available. Later, the H2 and O2 are recombined to provide electricity to the grid. The alkaline

environment of the new AEM-URFCs can avoid the conventional need for precious metals. The team

is researching non-precious metal catalysts and functional alkaline membranes that can work

together in this device. The researchers have developed the first working prototype of a precious-

metal free, low temperature AEM-URFC. They cycled it eight times between electrolyzer mode and

fuel cell mode demonstrating reasonable durability with round-trip efficiencies of 34-40 percent

throughout cycling. The team is now working to improve the key components of the device in order

to boost performance for both round-trip efficiency and durability.

Consuming Renewable Power: Information and Reliability as a Resource

Ram Rajagopal, Civil & Environmental Engineering

In this project the researchers address more efficient ways of offering and consuming renewable

power generation. Current approaches backup the renewable energy generation so it is as reliable

as traditional generators. This approach can significantly increase emissions and cost. Instead, this

research group is developing mechanisms that can benefit from existent flexibility in demand. For

example, demand can be scheduled to follow renewable power profiles in real-time, eliminating the

necessity for reserves. The researchers have designed several smart and simple scheduling

algorithms capable of following random power profiles. The researchers are also in the process of

designing a slotted mechanism that accepts user bids for different time slots offering available

power. Appliances could be programmed with a budget and simple rules to obtain slots for each

day. Finally, the researchers are starting to investigate models that estimate available flexibility in

existing demand from sensor data collected from 1,000 homes when utilizing these mechanisms.

The methodologies reveal that the reductions in emissions required can be drastic, if sufficiently

large populations of schedulable loads are available. As part of the project the researchers have

been building Snowflake, a wireless system capable of implementing the load scheduling algorithms

and interfacing with Zigbee radios present in most appliances and other devices.

Upconverter-Enhanced Molecular Photovoltaics: Cost-Effective, Broadband Solar Energy

Jennifer Dionne and Michael McGehee, Materials Science & Engineering

The conversion efficiency of thin-film solar cells may be enhanced by adding upconverters, which

allow more light from the sun to be absorbed by the solar cell. The researchers have modeled how

up conversion dyes could be used to improve the performance of the most common kinds of solar

cells. These dyes convert low energy photons to higher energy photons that can be utilized by the

cell. The researchers find that coupling up conversion dyes with dye-sensitized solar cells to be

most attractive, because dye-sensitized cells have a larger band gap than the other kinds of cells

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and can easily be made with two transparent electrodes. Their calculations indicate that

upconverting materials could improve these cell efficiencies significantly. The researchers have also

developed a new process for depositing transparent electrodes on solid-state dye-sensitized solar

cells that involves spraying silver nanowires. The researchers are using these silver nanowires and

related metallic nanostructures to enhance the absorption and emission of upconverting materials,

improving their efficiency.

Market-Based Valuation of Ecosystem Services for Competitive Large-Scale Solar†

Michael Lepech and David Freyberg, Civil & Environment Engineering; John Weyant, Management

Science & Engineering; Stefan Reichelstein, Business

This project captures the benefits of natural ecosystem preservation from large-scale solar power

production by quantifying valuable biological functions such as phosphorus removal. These

functions are valued using option pricing theory to result in a new class of biological assets, which

can be recognized on a generating company’s balance sheet. In cooperation with Combined Power

Cooperative, the research team has quantified the value of nitrogen cycling within the preserved

ecosystem on a concentrated solar power site in southern California. They are adapting financial

accounting tools to recognize this asset class on the cooperative’s balance sheet. The researchers

completed a life cycle analysis of the impacts associated with the materials and equipment

necessary for construction of the site. This was done to determine the effluents, wastes, pollutants

and resources that may alter the ecosystem. Also, by adopting a multi‐nutrient modeling tool, the

effect of multiple ecosystem services when evaluating a single natural environment can be

evaluated. The team has developed a case study on the levelized cost of energy from solar

production. Within this new model, the value of ecosystem services on the solar power generation

facility’s land is now being considered.

Effects of Large-Scale Solar Energy on Land and Water Resources in the U.S. Southwest†

Chris Field, Noah Diffenbaugh and David Lobell, Environmental Earth System Science

Researchers are developing a framework that establishes “big-picture” impacts of utility-scale solar

power plants in the dessert, a popular location. This study is investigating such installations in

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three ways: climate consequences of allocating land to large PV versus irrigated agriculture, which

could be used for bioenergy crops; possible synergies of integrating PV plants with bioenergy

agriculture; and whether some sites may simply be too dusty for large-scale solar, especially given

the expected effects of climate change and the projects’ disruption of local soil. One initial finding is

that, relative to irrigated agriculture, utility-scale PV tends to produce local cooling but warming

farther away. Also, researchers have found that the benefit of using PV-cleaning water to agave

plants would be quite small, approximately one-tenth the direct energy benefit of the cleaner PVs.

† Administered by the TomKat Center; funded by the TomKat Center and the Precourt Institute

2012 Wireless Power Transfer to a Moving Vehicle

Shanhui Fan, Electrical Engineering

In a follow-up to an earlier study, the research team is testing the feasibility of using magnetic

resonance technology to transmit electricity from roads to moving vehicles. In the earlier study, the

researchers showed that efficient wireless power transfer can be achieved in the presence of

metallic plates. In this study,

they have confirmed this earlier

finding experimentally by

demonstrating an efficient

wireless power transfer system.

In two different configurations,

they demonstrated maximum

efficiency exceeding 94 percent

over a distance of 23.6 inches

between the transmitting and

receiving coils. The long-term

goal is to develop roadways that wirelessly charge electric cars and trucks cruising at highway

speeds. The proposed technology could dramatically increase the driving range of electric vehicles

and transform highway travel.

Reliability vs. Cost Tradeoffs in California Renewable Energy Investments

Frank Wolak, Economics; Burton Richter, SLAC and Physics

This project is quantifying the added costs of serving California's electricity demand with an

increasing share of intermittent renewable generation, such as wind and solar energy. The analysis

is accounting for the major drivers of these costs, such as backup generation resources, large

energy storage systems, active demand-side participation and alternatives, such as transmission

upgrades and changes in how the system is operated. The research also is assessing the

management of intermittency under different wholesale power market rules and different

mechanisms for financial support of renewables.

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2013 Electrochemical Splitting of Supercritical CO2

Mark A. Cappelli and Reginald Mitchell, Mechanical Engineering; Tsuyohito Ito, Graduate School of

Engineering, Osaka University

In theory, excess power created by intermittent renewable power can be used to remove CO2 from

the environment and extract carbon monoxide, which can later generate electricity when the wind

is not blowing and the sun is not shining. Previous attempts at breaking the carbon-oxygen bond,

however, have consumed too much energy for an efficient storage system. This project will examine

the fundamentals of splitting CO2 under supercritical temperature and pressure to form CO, which

can be used as a fuel to produce electricity as needed. The researchers hope to establish that the

process can recover much of the energy used in breaking down the CO2 and form the basis for a

carbon-neutral way to store renewable power.

Junctionless solar cell for enabling third generation photovoltaics

Krishna Saraswat, Electrical Engineering

This project will seek to increase efficiency and decrease manufacturing costs of solar photovoltaic

panels by developing junctionless solar cells with transparent electrodes on commonly available

semiconductor materials, such as silicon or germanium. The researchers will eliminate the need for

doped positive/negative junctions by using conducting oxides which form a selective contact for

either electrons or electron holes. Such cells could also be stacked on top of each other to enable

greater than 50 percent efficiencies. The metal-insulator-semiconductor approach has already been

demonstrated to obtain low resistance contacts for nanoscale transistors and photonic devices.

Making Large Wind Farms More Productive, Less Expensive†

Sanjiva K. Lele, Aeronautics & Astronautics, and Mechanical Engineering; John Weyant, Management

Science & Engineering

Power output by large wind farms is typically 25 percent less than what it should be due to rear

windmills operating in the turbulent wakes of those up front. These wakes also increase strain on

the downwind blades and, thus, raise operating costs. This project, funded jointly by the TomKat

Center and Stanford’s Precourt Institute for Energy, will test whether positioning smaller, mixing

turbines among the primary turbines in conjunction with other new management approaches, will

significantly increase output and cut costs. The researchers will also develop an optimization model

for designing new wind farms and operational algorithms based on a given farm’s terrain and

environment.

† Administered by the TomKat Center; funded by the TomKat Center and the Precourt Institute