View the project assignment sheet, which includes deadlines and a description of the work product.

Following is a list of the projects completed by students in the course. Click on the project title to access the full project report.

1. Title: Battery Optimization Methodology For Hybrid City Bus Applications, Paper, Presentation
Student Members: Ryan Balliet, Robert Carr, Adam Gross, Priya Jayachandran, Hannah Murnen
Executive Summary :
In 2005, The Alameda-Contra Costa Transit District (AC Transit) began a hybrid demonstration program using zero-emission hybrid electric hydrogen fuel cell buses. The hybrid drive on these buses derives motive power from a 120 kW fuel cell engine and a 95 kW, 53 kWh nickel sodium chloride battery system. Currently, the bus design is based on a desire to match the capabilities of a standard diesel bus, and does not take into account the actual power or energy requirements of specific routes. AC Transit has expressed a desire to tailor the battery system of the next-generation hybrid bus to the requirements of specific routes that it will be servicing. This approach should enable lower bus mass and reduced cost, but requires a more detailed analysis of how route parameters affect battery size and durability.

2. Title: Maximizing Lifetimes of Lead Acid Batteries in Rural Applications, Paper, Presentation
Student Members: Christian Casillas, Paul Cordeiro, Michael Geier, Devesh Khanal, Adrianne Rosales
Executive Summary :
Power generation using small-scale renewable sources such as solar and wind can be the
lowest cost option in areas where populations are widely distributed and power
consumption rates are low. The intermittency of such power sources demands energy
storage with batteries. However, the energy usage and power generation characteristics
can greatly affect the lifetimes of the batteries. Failure of the battery system leads to high
costs and loss of access to power. Herein, we present cycle-life and cost analysis of lead
acid batteries for rural applications, based on communities in Nicaragua powered by wind
and solar systems established by the non-profit organization blueEnergy.
We base our analysis on two types of applications of lead acid batteries: (1) Battery
banks, where multiple batteries are kept at a single location, permanently connected to
the power sources and used for routine predictable loads at their location (e.g. school
lighting near a wind and solar system). (2) Single-user batteries that are used in private
homes and brought back to charging stations semi-regularly.

Cycle life analyses are performed using several simulation models: HOMER, KiBaM,
and a MATLAB-based model. The lifetime estimates of HOMER and KiBaM provide an
upper bound since neither model currently account for specific aging mechanisms due to
charging and usage. In order to order to determine which aging mechanisms would be
most prevalent, a group of stress factors were determined for a number of particular
system configurations.

We find that the current system configuration being used by blueEnergy make the
permanent battery banks highly susceptible to irreversible sulfation due to prolonged time
a low states of charge, and recommend increasing the solar generation component of the
charging systems, increasing the setting low voltage disconnect, and increasing the
capacity of the battery bank to reduce Ah throughput. For the single user systems it is
beneficial to also increase the low-voltage disconnects on the home systems, and
continue to utilize payment systems that encourage frequent charging (pay per month,
rather than per charge). In terms of the types of batteries, deep cycle flooded lead acid
batteries are the most cost-effective options for these systems.

3. Title: Batteries for a Solar Powered Home, Paper, Presentation
Student Members: Yeon Choi, Becca Jones, Joe Swisher, James Wilcox
Executive Summary :
We investigated the cost of using batteries and solar cells to power a home in California. We considered four battery chemistries: lead acid, nickel metal hydride, sodium sulfur, and lithium ion. Using the HOMER micropower optimization software from the National Renewable Energy Laboratory, we compared the net present costs of systems with each of the different chemistries. For the average household consumption of 30 kWh per day, no system was cost competitive with grid electricity. We considered the effect of shifting demand to periods of high PV output, known as a deferrable load. This reduced the cost of a given system by 25% to 45%, but the lowest system cost was still more than twice as expensive as grid electricity at its current price. Finally, we considered the price trends necessary to bring the cost of these systems within reach of grid electricity prices. We found that an 80% reduction in the installed cost of PV and a doubling of the net present cost of electricity would be needed to make PV/battery systems immediately competitive. In this best case, only lead acid was cheaper than grid electricity without modification, and the other chemistries required a 50% reduction in price to be competitive.

4. Title: Evaluation of Battery Format for HEVs and PHEVs, Paper, Presentation
Student Members: Kurt Amundson, Jonathon Germain, Megan Hoarfrost, Zack Subin
Executive Summary :
We have investigated the properties of batteries for use in hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs). We were specifically interested in how battery format, meaning battery size and shape, affects battery performance, meaning energy and power. Our investigation began with a survey of the literature to determine current knowledge about various battery chemistries being considered for HEVs and PHEVs and an analysis of available manufacturer data to determine trends between specific energy and specific power and battery mass. It continued to include a theoretical analysis of the relationship between energy, power, and cell size, determination of chemistry-specific battery properties and the creation of a model which was used to the ability of currently available batteries to meet hybrid vehicle needs. Based on our analysis of manufacturer data and our theoretical analysis of scaling, we found that the influence on battery performance of the design expertise of the manufacturer outweighs the influence of the physical relationship between size/shape and energy/power. Furthermore, based on our model we recommend a battery pack made from Lithium Technologies’ HE-602050 lithium iron phosphate batteries for use in PHEVs today.

5. Title: Cycle Life Analysis of Battery Modules for Plug-in Hybrid and Full Battery Electric Vehicle Applications, Paper, Presentation
Student Members: Christine Ho, Michael Lin, Lisa Onishi, Peter Stone
Executive Summary :
This report summarizes the cycle and calendar life of nickel metal hydride,
lithium-ion, and ZEBRA batteries. All three battery chemistries met the EV
requirements, which are 1000 deep cycles at 80% depth of discharge (DOD) and a 10
year calendar life. Cycle life was shown to decrease with increasing DOD. In addition,
nickel-cadmium, nickel-metal hydride, and Li-ion batteries’ cycle life was fit to an
exponential relationship involving cycle life and DOD at high DOD. The degradation
mechanisms for all three battery chemistries are summarized in this work as well. One
common cause of all three batteries’ degradation is material fracture. Since all three
battery types meet the EV goals, we suggest that EV batteries be chosen based on other
factors, such as power and energy density, cost, safety, and toxicity.

6. Title: A 2-D Modeling Investigation of Lithium Deposition in Li-ion Batteries, Paper, Presentation
Student Members: Anthony Goodrow, Will Regan, Jakod Spjut, Maureen Tang
Executive Summary :
Lithium deposition on the negative electrode during charging is one of the key factors that
degrade the capacity of lithium-ion cells. To better understand this process, a model of the
galvanostatic charge of a lithium-ion cell was developed. Of particular interest was the effect of
electrode geometry on lithium deposition, since geometries for commercial cells are presently
chosen empirically. The final goal was to make a 2-D model which could show the deposition
behavior in two kinds of cells, one in which the positive electrode overlapped the negative and
one in which the negative overlapped the positive. Our cell chemistry was a common
configuration: a composite graphite anode (C6, MCMB 2528), a separator consisting of LiPF6 in
EC : DMC (ethylene carbonate : dimethyl carbonate), and a composite LiCoO2 cathode. We
began with transport and electrochemical equations, as well as system parameters from previous
literature.1-6 The programs COMSOL Multiphysics and Mathcad were used for computation.
The problem of solving for the current distribution was divided into three orders of increasing
complexity: (1) primary (solving Laplace’s equation in the separator), (2) secondary (primary
plus kinetics across electrode-separator boundaries), and (3) tertiary (secondary plus solid-phase
lithium diffusion). We successfully solved for the primary distribution in 2-D with COMSOL
and up to the secondary distribution in 1-D with Mathcad. Our results give some preliminary
insights into the 2-D current distribution for different electrode geometries and an approximation
of the critical state of charge before deposition for various constant charging currents.

7. Title: Analysis of EEstor and Capacitive Energy Storage Technologies, Paper, Presentation
Student Members: Wei-Cheng Lien, Bryan McCulloch, Jason Stauth, Kevin Wang, David Wong
Executive Summary :
EEstor has filed a patent for a capacitor that challenges conventional wisdom and outperforms current battery technology. Adding credibility to the claims, ZENN Motor Company and KPCM have invested a combined $7.8 million in EEstor. EEstor has been very secretive and many experts have been very skeptical of the claims made by EEstor. The objective of this report is to investigate the validity of the claims that EEstor makes and attempt to predict whether this technology is feasible. The report also compares EEstor’s capacitor to current ultracapacitor technologies and looks into the challenges of incorporating capacitors into electric vehicles.

The EEstor patent contains designs for a parallel plate capacitor with a capacity of 52 kWh and weighs 150 kg. This amounts to an energy density of 350 Wh/kg, at which EEstor claims to achieve a capacity cost of $40/kWh while most advanced battery technologies are only able to deliver around 150 Wh/kg and $100/kWh. They also claim that their capacitor will last for at least one million cycles and charge within minutes. EEstor is able to achieve very high energy density because they are they use an exotic dielectric material of coated barium titanate which supposedly has an extremely high dielectric constant (29,500) and breakdown voltage (5 MV/cm).

There are many reasons to doubt EEstor. First, it is very difficult to tell if they will be able to create a dielectric material which will meet these specifications. Although there is some scientific basis that may allow them to create such a material, it seems unlikely at this point. The implementation of this technology may also be difficult because dealing with high voltages necessitates charging stations. Finally, it is difficult to tell whether their lifetime targets are accurate and whether this high voltage capacitor can be operated safely. In the end, there is not enough information to conclude whether EEstor will be able to produce a capacitor that lives up to the hype. It appears that we will need to wait and see what happens in the near-future to discern more about how effective their technology is in actuality.

8. Title: Campus Fleet Evaluation Using Alternative Energy Vehicles, Paper, Presentation
Student Members: Sean Dee, Shrayesh Patel, Ting-Ying Wong
Executive Summary :
The University of California at Berkeley emits 209,000 metric tons of carbon dioxide annually. The 577 vehicles in the campus fleet contribute 1,040 metric tons of CO2 (0.4%) annually. The University has set a goal to reduce annual emissions to 167,000 metric tons (20% reduction) by 2014. This project’s objective was to examine the economic feasibility and impact of converting the vehicle fleet from gasoline to alternative fuel sources.

Our study found that electric vehicles proved to be the most effective and economically feasible solution to the vehicle fleet conversion. Pacific Gas and Electric (UC Berkeley’s electric supplier) provides a very “clean” source of electricity with very little use of coal. Electric vehicles are at least an order of magnitude cheaper compared to E-85, Bio diesel, and hybrid vehicles when examining the cost per tons of CO2 reduction. To replace the current fleet sedans, pickup trucks, and mini vans, the University would have to absorb a loss of approximately $1,200, $2,300, and $4,300 per car respectively. Replacing all the sedans, pickup trucks, and mini vans would cost the University roughly $962,000 and reduce CO2 emissions annually by 580 metric tons.

While electric vehicles prove to be the best alternative for fleet replacement, accomplishing the emission reduction goal in 2014 will require the university to look at other alternatives to replacing the fleet. Reducing electricity and steam usage on campus will play a much bigger role, and could possibly be much more cost effective, than replacing all the vehicles in the fleet.

9. Title: Life Cycle Analysis of the Tesla Roadster
Student Members: Greg Bogin, Robert Broesler, Jr., Gopal Choudhary, Nate Craig
Executive Summary :
Not available due to NDA.

10. Title: Who Threw Away the Tesla Battery Pack? An Economic and Environmental Assessment of Battery Recycling
Student Members: Keith Beers, Scott Mullin, Thomas Schwei, Justin Virgili, Nisita Wanakule
Executive Summary :
Not available due to NDA.