RIT is confronting the global challenges of sustainability through interdisciplinary programs that integrate engineering and science with economics and public policy.
by: Kara Teske November 2010
RIT researchers across campus are conducting a wide array of fuel cell research to advance the widespread adoption of this clean and efficient green technology.
When man stepped foot on the moon more than 40 years ago, fuel cell technology was there electrifying the journey. Why, then, has this emission-free, clean technology not been widely adapted here on earth? There are three main challenges researchers at RIT and around the world are addressing to enable the widespread adoption of fuel cell technology: cost, durability, and hydrogen infrastructure.
Driven by industry and with support from local, state, and federal government, RIT researchers from across campus are addressing these challenges in a number of ways:
"Together, the researchers create a wealth of knowledge from fundamental understandings to testing and simulation that will help to accelerate the commercialization and introduction of fuel cell technology," says Matt Fronk, director of the Center for Sustainable Mobility at the Golisano Institute for Sustainability and former director of General Motor's Fuel Cell Research Laboratory. "When adopted, fuel cell technology, along with other alternative fuel and propulsion technologies, will help us achieve the national goal of reducing our CO2 emissions 80 percent by 2050."
As discussed in the article "Small Science Big Impact", one of the critical challenges of proton exchange membrane fuel cells is managing the water inside the cell. Dr. Thomas Smith, professor of chemistry and interim academic director of the Golisano Institute for Sustainability, is also examining a related issue described as the high-temperature membrane problem. An essential constituent of the proton exchange fuel cell is the proton exchange membrane (PEM). The PEM is typically a sulfonic acid fluoropolymer that needs to be hydrated to function well. When the temperature is elevated, above 100°C, the humidity drops and the proton conductivity in the PEM decreases dramatically. Smith has been leading an effort to explore the ability of a PEM comprised of a nanocomposite of a fluoropolymer and a novel protonated imidazole polymer to transport protons at high temperature and low humidity.
These unique polymers are synthesized at RIT and have been provided to Dr. Timothy Fuller at General Motors for evaluation of proton conductivity. Smith and Fuller have been collaborating since 2004. Jinhang Wu and Jingjing Pan, graduates of the chemistry MS program, both completed thesis research that focused on the elucidation nature of the nanocomposite membranes. Joel Walker, an undergraduate chemistry student, is continuing to synthesize imidazole polymers for proton conductivity studies at GM. While proton conductivity results to date at temperatures below 100°C have been promising, measurements at higher temperatures are needed in order to assess the viability of imidazole polymer composites as a solution to the high-temperature membrane problem.
"When we are educating students we look at a critical technology problem and say, 'What's the need? What's the critical problem?' Working on this problem allows our students to learn and see what issues need to be addressed, and that it takes time to find the answers. From this perspective this research has been an excellent learning vehicle," says Smith.
The other aspect of hydrogen fuel cells the chemists are working to address is identifying a membrane electrode system with a base metal catalyst to replace platinum. "If we can catalyze oxidation of H2 and reduction of O2 with metals that are cheaper and more ubiquitous in the environment, the economic viability of hydrogen fuels cell will be greatly enhanced," adds Smith.
Dr. Denis Cormier, Earl W. Brinkman Professor and associate professor of industrial and systems engineering, is part of a multi-university collaboration with the University of South Carolina's Hetero-FoaM Energy Frontier Research Center that is sponsored by the Department of Energy's Office of Science. The center is focused on bridging the gap between making nano-structured materials and understanding how they function in energy applications. The group Cormier leads is developing new processes to synthesize and fabricate novel materials for solid oxide fuel cells (SOFC), specifically for the anode and cathode.
Using models developed by the center's analysis and simulation groups, Cormier is synthesizing materials using novel additive manufacturing techniques. "The design of porous layers in a fuel cell involves making tradeoffs. Large pores are desired to allow hydrogen fuel to easily flow into the cell. At the same time, small pores with high surface area are preferred for increased electrochemical activity," explains Cormier. By using additive manufacturing, sometimes referred to as 3-D printing, the group hopes to be able to grade the porosity of the material from large down to fine pores, similar to that of the human vascular system.
The machine used to create the material operates similar to an inkjet printer, where each cartridge has a different color or pigment. In this case, the pigment is replaced by nano-sized particles used to make fuel cells. In the first phase of the project, Cormier is using three material print heads to mix the "inks" and grade from one material composition to another. Building on to this approach, a second piece of equipment with two material heads and a built-in laser allows for particles to be fused as the material is printed. Because each material fuses at a different temperature, the laser power can be adjusted to address the dissimilar materials.
A fuel cell consists of three layers, each made from a different material. Because virtually all materials expand when they are heated, dissimilar expansion rates between the layers can lead to cracking and degradation of the cell. "By gradually blending the composition of the material between layers, issues of durability can be addressed. At the same time, we can control the porosity of the material," explains Cormier.
The printed fuel cells are provided to the characterization and validation group based at the University of South Carolina to test and determine how well the models predict the performance of the fuel cells.
"The work Dr. Cormier is doing is very important, especially in a new technology area like fuel cells. Many times the manufacturing process of integrating materials is not addressed upfront to insure that the effects of various process parameters on ultimate system performance and durability are taken into consideration," adds Fronk.
Research at the Hybrid Sustainable Energy Systems (HySES) Laboratory, based in RIT's department of mechanical engineering, is focused on model development, real-time simulation, and control design for solid oxide fuel cell systems. The lab's research is supported by the National Science Foundation and the Office of Naval Research. Led by Dr. Tuhin Das, assistant professor of mechanical engineering, the laboratory has developed models for a number of SOFC configurations, reformer types, and fuel types. The models capture the primary physical phenomena of SOFC systems, such as thermodynamics, heat transfer, reaction kinetics, pressure dynamics, and electrochemical phenomena.
"Fuel cells are complicated systems with numerous interconnected physical phenomena. The challenges involved in these model development efforts lie in model management and in reducing computational burden while capturing the essential system characteristics," explains Das. "The use of modular modeling practice and hierarchical model architecture that we have developed at HySES is instrumental in addressing these challenges."
The laboratory also focuses on system characterization, which gives a clearer understanding of the transient and steady-state behavior of SOFC systems. The research provides insight into the different and varied time-scales involved in the overall functioning of SOFC systems. The time-scales arise due to both the presence of varied physical phenomena and the interaction of balance-of-plant components with each other and the fuel cell. "Understanding of the system characteristics helps us to develop control strategies that lead to optimal performance," adds Das.
Controlling the transient behavior of SOFC systems is critical for preventing fuel starvation, a phenomenon that SOFCs are susceptible to, especially when exposed to power transients. Difficulty in sensing the internal conditions of the SOFC makes this issue particularly challenging.
Traditional approaches require many extra sensors that significantly increase cost and also pose reliability issues. Alternately, detailed models may dramatically increase computational burden on the controller. Das and his team of researchers have developed an innovative approach using a fundamental property of the SOFC system obtained through characterization studies. The approach not only reduces sensing requirement, but also reduces the reliance on a computer model and specific knowledge of the system.
Simultaneously, the laboratory is also exploring ways to improve the responsiveness of SOFC systems to fluctuations in power demand. Addressing this issue would expand the use of SOFC systems from uniform power applications to rapid-response scenarios. However, for SOFCs, improving responsiveness and preventing fuel starvation are conflicting control objectives. The laboratory's research handles this limitation by augmenting the SOFCs with energy storage elements, such as batteries or ultra-capacitors, and other energy storage concepts. Such hybridization leads to a spectrum of control problems where control of the storage element and power-split algorithms must be developed that effectively handle system and sensing uncertainties. The research team is exploring the use of robust nonlinear control strategies to address these control problems.
The Golisano Institute for Sustainability (GIS) is home to a suite of full-scale testing and simulation capabilities for fuel cell systems. In 2009, the Center for Sustainable Mobility, based at GIS, constructed a facility to conduct system-level testing onsite for solid oxide fuel cells. The first-class facility is equipped with three test stations and hook-ups to alternative fuels, including natural gas, hydrogen gas blends, biodiesel blends, and US07 ultra low sulfur diesel. In partnership with Delphi, researchers at the Center for Sustainable Mobility are conducting tests to identify options to further develop the product durability and reliability, as well as develop cost-effective manufacturing processes of solid oxide fuel cells. This joint project is sponsored in part by the U.S. Office of Naval Research and the Army Tank Automotive Research, Development, and Engineering Center.
"This lab plays a key role in the overall product development cycle by working on the connection of materials research into first scale up products or systems. We provide some of the early durability work or development testing at small scale, while our industry partner's work on the larger scale issues. Ultimately this will help to accelerate the whole process toward commercialization," adds Fronk.
Until now, minimal investigation has been done on the life cycle and failure analysis of fuel cell systems. Researchers at the center are conducting accelerated durability testing based on failure modes identified through failure mode and effects analysis (FMEA) evaluations. Once these failure modes are understood, environments are created to accelerate them and further analyze how they affect performance and durability trends, as well to begin building a database for future products to assist in predicting failures before they occur. For example, carbon formation has been identified as one of the key performance issues, so carbon formation is accelerated to understand the key operating signals and trends that could be used in forecasting future failures.
Dr. Thomas Trabold, associate research professor at GIS, is also conducting fundamental parametric studies to identify parts of the operating envelope where carbon formation occurs and providing recommendations to mitigate the problem. The studies show that temperature changes, which occur during SOFC startup, result in excessive carbon formation, leading to the degradation of system performance and durability. By simulating the temperature gradients at startup, the operating protocols can be customized to allow the system to reach higher temperature before supplying the fuel and air to the fuel reformer.
"This research directly supports industrial partners like Delphi, and provides an understanding of the fundamental underpinnings to their commercialization process," says Trabold.
One of the cornerstones of the Center for Integrated Manufacturing Studies, from which GIS emerged, is built on remanufacturing strategies. In solid oxide fuel cells, the materials must withstand extreme temperatures up to 800°C, and as a result are typically expensive. The group is also identifying key component areas of this fuel cell technology that are ripe for remanufacturing. "If you could reuse one or more of these high-value subsystems nearing the end of its useful life by harvesting the valuable raw materials or components within them, they could be utilized for three to four lifetimes," explains Daniel Smith, senior program manager at CIMS. "By incorporating these considerations into the design upfront we will be able to maximize the system value."
"'Reman,' as the term is commonly used in industry, is not always applied to new technology programs. We believe that by involving the concepts around design for remanufacturing that the early commercialization and technology insertionplans can more easily and more cost effectively be executed," says Fronk.
While scientists and engineers work to advance fuel cell technology to reach mass commercialization, public policy experts are analyzing the policy mechanisms and how they affect market penetration.
Dr. James Winebrake, professor and chair of the department of science, technology, and society/public policy, and a team of master's degree students have been analyzing how different levels of subsidies might pull a market forward and how mandates at either the state or federal level might allow for the penetration of hydrogen fuel cell vehicles. "The role of the public sector is critical in moving fuel cells into the market," says Winebrake. "Policies and programs at the federal, state, and local levels that help reduce the upfront costs of fuel cell vehicles are important, as well as programs that encourage the development of hydrogen refueling stations."
The group is also conducting dynamic systems modeling to simulate the evolution of the fuel cell vehicle market and the role policies play in affecting market trajectories. The simulations help to explain the dynamics between vehicles and the infrastructureneeded to refuel those vehicles.
The models show that "clustering" hydrogen refueling stations at a higher density in fewer locations is more effective in creating sustainable hydrogen vehicle markets than spreading these stations out at lower density in more locations. For example, building 30 stations in each of 10 areas is a more effective strategy than building 10 stations in 30 areas. "The modeling and simulation affirms this approach. Hydrogen station density is a key factor in fuel cell market development, and a critical mass of stations is needed for fuel cell vehicles to obtain market traction," explains Winebrake. "Rochester is one area where clustering could be successful."
The city is home to research and development for fuel cell technology, with three fueling stations already in place: the GM Facility in Honeoye Falls, N.Y.; the Monroe County Green Fuel Station near the airport; and on campus at RIT. "This network has supported our demonstration of the viability of fuel cell vehicles in five years. It's an important point of confidence for developing public awareness that you can deal with hydrogen in a safe way and fueling can occur quickly. RIT's participation is just another way they are supporting our program and helping to advance the technology," adds Dr. Mark Mathias, lab director for fuel cells and batteries at GM.
To get the technology and the infrastructure to a point where consumers are able to enjoy the benefits of fuel cell technology, Winebrake believes there is a need for early involvement from the public sector by continuing to support companies and universities with research and development; encouraging consumers with tax incentives; and facilitating the infrastructure development to ensure the technology and infrastructure move forward simultaneously.
New York state is taking the lead in developing real plans to reduce their carbon footprint by 2050, and both Winebrake and Fronk have been asked to participate in the New York Climate Action Council focused on important policy and planning programs.