FY2011 Annual Report for NREL Energy Storage Projects

Abstract

Printed on paper containing at least 50% wastepaper, including 10% post consumer waste.iii ForewordThe Energy Storage Team within the Center for Transportation Technologies and Systems at the National Renewable Energy Laboratory performed the work detailed in this report under the Energy Storage Research & Development (R&D) activity of the Vehicle Technologies Program, which is managed by David Howell within the U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy, in support of the automotive and battery industries. In fiscal year 2011, NREL identified several R&D projects in its Annual Operating Plan submitted to DOE on materials, battery modeling, computer-aided engineering of batteries (CAEBAT), battery testing, life trade-off study modeling, techno-economic analysis of battery-powered vehicles, and secondary use of batteries. A summary of each project was prepared and submitted to DOE for inclusion in the Energy Storage FY11 Annual Progress Report. This report is a collection of the individual reports submitted to DOE.This research and report would not have been possible without the support and guidance of many people. The authors wish to thank Brian Cunningham, Tien Duong, Peter Faguy, and David Howell from Vehicle Technologies Program of the U.S. Department of Energy for funding support and guidance. We also wish to thank Taeyoung Han of General Motors, Steve Hartridge of CD-adapco, and Christian Schaffer of EC Power for their contributions to the CAEBAT program. iv Executive SummaryThe National Renewable Energy Laboratory (NREL) supports energy storage R&D under the Vehicle Technologies Program at the U.S. Department of Energy (DOE). The DOE Energy Storage program's charter is to develop battery technologies that will enable large market penetration of electric drive vehicles. These vehicles could have a significant impact on the nation's goal of reducing dependence on imported oil and gaseous pollutant emissions. DOE has established several program activities to address and overcome the barriers limiting the penetration of electric drive battery technologies: cost, performance, safety, and life. These programs are: • Advanced Battery Development [through the United States Advanced Battery Consortium (USABC)]• Testing, Design and Analysis (TDA)• Applied Battery Research (ABR) • Focused Fundamental Research, or Batteries for Advanced Transportation Technologies (BATT)In FY11, DOE funded NREL to make technical contributions to all of these R&D activities. This report summarizes NREL's R&D projects in FY11 in support of the USABC, TDA, ABR, and BATT program elements. In addition, we continued the enhancement of NREL's battery testing facilities funded through the American Reinvestment and Recovery Act (ARRA) of 2009.The FY11 projects under NREL's Energy Storage R&D program are briefly described below. Each of these is discussed in depth in the main sections of this report. ARRA -Battery Thermal Test Facility:With investment from ARRA, the size of our battery doubled, significant ...

Stack Models and Designs for Improving Fuel Cell Startup From Freezing Temperatures

“…Assuming that water vapor is at saturation everywhere in the cell during the experiment then the temperature difference across the MEA causes a water vapor concentration difference. It should be mentioned here that the water flux in equation [1] is significantly higher than the water vapor diffusion flux across the MEA generated by the water vapor concentration difference. Equation [1] is extensively used in the design of fuel cell stacks at Ballard Power Systems to achieve appropriate water distribution in the stack at startup.…”

“…Using correlation [1] for water flux through MEA due to temperature gradients, a model is also developed to predict the MEA water content during the natural cooling of the partially insulated stack in Figure 1 after shut down. The model consists of a transient heat conduction model for stack cooling after shut down and a water migration model based on equation [1] and a calculated temperature profile in the stack.…”

“…The model consists of a transient heat conduction model for stack cooling after shut down and a water migration model based on equation [1] and a calculated temperature profile in the stack. Before shutdown the stack is operated with a very small temperature differential between inlet and outlet so that we can assume that the stack cooling and the MEA water migration is one dimensional along the stack.…”

“…However, several aspects of fuel cell startup from freezing temperatures can still be found in a small number of research papers, most of which are mentioned in a comprehensive review by Pesaran [1]. For example, membrane properties such as ionic conductivity and water diffusion coefficient at cold temperatures were evaluated by Saito et al [2].…”

Electrochemical characterisation of fuel cell stack during cold start

“…Since the 90's, many works have been done aiming at reaching the self start up of FCs from cold temperatures compatible with transportation applications [1]. Numerous patents have been registered on this subject but many of them suggest warming the FC by means of an external circuit before to start it up [2].…”