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Fuel Cell/PEM/UTC page 050917
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From the Fuel Cells 2005 conference...
Porous Plate Technology Advances PEM Fuel Cell Performance, Durability and Cost Effectiveness
Reviewed by Donald Georgi
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If any company has a long and successful presence in the field of fuel cells, it is UTC Fuel Cells, a part of UTC Power, a business unit of United Technologies Corporation. The graphical progression on the cover shows the practical beginnings with the Apollo Moon Program. Later, UTC alkaline fuel cells powered the Space Shuttle which obtained its electrical power, cabin cooling and drinking water from the fuel cell system from the very first flight to the latest successful STS 114 flight. Since 1992, the high power phosphoric acid 200 kW stationary systems have been used in commercial applications which have now provided over one billion kWh. The units installed in the Condé Nast Building have provided the base load power to the building since the turn of the century. (See BD Oct. 99 issue #43-13.) Current PEM fuel cell developments are finding applications in auxiliary power units, auto and bus propulsion, industrial uninterruptable power and backup applications. This rich history of implementation gives UTC Fuel Cells an experiential base second to none and generates expectations of their technical leadership in fuel cells.
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Commercialized fuel cells have been just around the corner for a decade as many wonder if they will ever emerge from the curiosity stage. For a moment, set the issue of a hydrogen distribution system aside and view this fledgling period of fuel cell development as a technology which can call on any available or convenient fuel source to focus on the more fundamental question of whether a fuel cell can compete with alternate energy conversion devices.
Looking only at the fuel cell system, the problems of performance, durability and cost have been limitations, often with orders of magnitude in improvements needed to make the cell competitive. Some improvements in one limitation can have a negative impact on another limitation such as cost reductions which would reduce durability. The technical world is searching for disruptive improvements which in the simplest implementation remedy only one limitation, and at best, enhance performance, increase durability and reduce costs simultaneously.
Inherent in the challenges of a dynamic system is the gradual change in the relative humidity (RH) as oxygen is delivered to the stack and water is produced from the reaction. Ordinary PEM fuel cells address the problem with a complex addition of system air and water conditioning to achieve the best possible combination for operation. Uniform RH can be improved by the microporous plate material developed by UTC Fuel Cells. (Reproduction permission is by UTC Fuel Cells, facilitated by author, Mike Perry.) +
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Such is the case with a radical improvement introduced by Mike Perry of UTC Fuel Cells at the Fuel Cells 2005 Conference. The audience was expecting a research report with many graphs and hopeful statements of incremental improvements which will make the fuel cell practical. This presentation, however, had an alternate bright ray of hope based on a way to improve water management in PEM fuel cells.
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The focal point of this presentation was the introduction of microporous-plates which allow water to exist in a liquid phase alone. This allows for uniform moisture distribution which improves performance and removes the need for support hardware, increasing reliability and reducing system cost. (Reproduction permission is by UTC Fuel Cells, facilitated by author, Mike Perry.) +
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The fundamentals of a PEM fuel cell appear to be simple enough; a solid membrane is used to isolate the anode from the cathode. Batteries do the same thing, but in the PEM membrane, water is needed to transport ions for conduction and to ensure long membrane life. At this membrane, hydrogen from the anode combines with oxygen from the cathode, producing water continuously as the cell generates electricity. At the same time, the cathode reaction combines oxygen with the hydrogen ions being transported through the membrane and external electrons to produce more water. The bottom line is that excess water is produced and must be transported away from the reaction sites to allow a continuous conduction process.
 Beyond the performance improvements inside the MEA, it is easy to see the contribution of cost reduction of the MP in the elimination of water handling hardware. These items not only require additional costs but also offer additional ways the system can degrade and fail. (Reproduction permission is by UTC Fuel Cells, facilitated by author, Mike Perry.) +
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Despite being pure and usable externally, the cell-generated water creates a problem. Water buildup leads to poor performance and high decay rates. Removing the water is accomplished with two phase (liquid and gas) flow, still leaving uneven distribution and poor system efficiency. On the other hand, if cell humidity is too low, performance again decreases and membrane life is sacrificed. The key then is to manage this water with humidifiers, condensers, recycling blowers, water recovery devices and air exit valves. These devices make up a major part (and expense) of the balance of plant (BOP) which also reduces system durability because any of these components can be the source of ‘something else to go wrong.’ This water process, while necessary, complicates the PEM fuel cell system.
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The efficiency of fuel cell systems is an inherent and dramatic advantage over internal combustion engines. Progress in the increase of fuel cell efficiency at UTC is shown in the above data which now meets the longer term market requirements. (Reproduction permission is by UTC Fuel Cells, facilitated by author, Mike Perry.) +
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UTC Fuel Cells presented a new path in the design of a PEM fuel cell by addressing this water dilemma. Water is initially required for conduction but additional water produced during the process must be removed. UTC bypassed conventional humidification control with a proprietary ‘Microporous-Plate’ (MP) - a foam-like construction of the anode, cathode and membrane material. The MP allows water generated to remain in the liquid phase, simplifying the process.
Fuel cells which power transportation vehicles are subject to start/stop cycles which reduce the durability of the system. Data shown shows improvement in start/stop performance and lends a large degree of credibility to the information from UTC which realizes that representative testing must precede the introduction of even prototype product. (Reproduction permission is by UTC Fuel Cells, facilitated by author, Mike Perry.) +
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At first glance the improved system suggests expensive construction and operational limitations. But the surprise is that within the cell, the stack costs are lower than with conventional PEM cells. Due to the greater resulting efficiency, the stack sized is reduced, and the transient performance in enhanced. This is a truly disruptive improvement.
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The industrial battery market, in addition to the automotive propulsion and large power generation markets, is desirable for fuel cells because of its large existing base of applications and need for both mobile and stationary units. Fuel cells can begin in applications which favor fuel cell characteristics, establish a base and history of performance and grow into further segments of the market. (Reproduction permission is by UTC Fuel Cells, facilitated by author, Mike Perry.)
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Another benefit is reduction of the system cost and increase of durability. Because the water is simply removed in single phase liquid flow, the traditional humidification BOP components, which include the humidifier, compressor, recycling blower, water recovery devices and exit valves, are eliminated. Without these devices, there is nothing to go wrong, so system reliability improves. Since these devices are not needed, their installation cost goes away and space is saved, thus shrinking the system volume.
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Fuel cells which power transportation vehicles are subject to start/stop cycles which reduce the durability of the system. Data shown shows improvement in start/stop performance and lends a large degree of credibility to the information from UTC which realizes that representative testing must precede the introduction of even prototype product. (Reproduction permission is by UTC Fuel Cells, facilitated by author, Mike Perry.) +
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The market has repeatedly been buoyed by earthshaking announcements, only to be forgotten in the ensuing months. This is where the experience base of UTC should be counted on to realize the benefits of MP technology if it produces the performance and price advantages heralded. The rash opportunist would create a flash in the pan hoping to make a bundle of money quickly, but UTC realizes that the system needs to be characterized, defined in implementation, and tested until suitable system durability is proven. This is the present challenge for UTC; and data presented since 2002 indicates the efficiency and durability is on its way to providing the promised improvements.
Beyond performance, the cost cutting contributions from the less expensive MEA will have to be proven. UTC already has an additional system answer to cost improvements which includes utilizing common parts from suppliers to other OEM fuel cell manufacturers. At this time, when there is a large gap between manufactured cost and competitive power converters, using industry standard parts increases the total manufactured volume of such parts, resulting in economies of scale.
(Ed note: Fuel cell developers, in this embryonic stage, could learn from the mistakes of the portable electronics industry which has almost never used industry standard Lithium-ion packs. Not only does the one-time-only design increase the user’s cost, but it also makes replacement acquisition and cost many times higher. If one wants to see an even more extreme version of non-standardization, he/she need only look at the computer connector nightmare where power and data connectors defy standardization.)
Applications
Three big questions always surround the subject of fuel cells: If? When? and Where?
Using UTC as a dynamic model for the pursuit of these questions is justifiable because UTC has the longest customer-based fuel cell supply experience, and the comapny has been associated with a variety of technologies and markets. In addition, the corporate expertise in building profitable business ventures makes UTC one of the most credible sources of fuel cell implementation.
The ‘if’ question: Will fuel cells ever make it to market? Over the years, technologies such as DC power transmission have ebbed and fallen; yet, many have found specific niche applications. If the desire for low temperature and clean power generation were the only driving force, fuel cells with Microsoft-like bugs would be available today. But the problems of high reliability, durability and cost hover over any competitive introduction of fuel cells since this technology will be applied where users expect ruggedness at an already perceived price. With the improvement of water management through microporous plate technology, a major addition to both the cost and durability is possible. Today, UTC is continuing a long test program for the PEM performance and durability with published data indicating success of the MP concept. In summary, data shows the ’if’’ question is closer to a ‘yes’ answer with MP in the hands of a capable business such a as UTC.
The ‘where’ question: Market selection is critical to the implementation of fuel cell technology. Taking a lesson from the failed CARB attempt to develop electric transportation for California, the choice of replacing the family sedan was a guarantee of failure. Had a more conservative and evolutionary approach been taken with niche markets and suitable time frames, there could still be a healthy battery transportation program in California because the need for cleaner, fuel-efficient power has not gone away.
Setting the product/market application for phosphoric acid/large power plants and alkaline/aerospace aside, UTC is focused on applications in automotive and industrial battery replacement markets for the MP PEM technology. Both markets require configurations with moving vehicles where PEM features provide the greatest advantage in the families of fuel cell technologies.
In the area of industrial applications, UTC sees an existing need both for mobile and stationary units. Using the niche approach, early offerings can provide the foothold while continued presence and technological improvement can expand the product offering.
In the area of automotive power, UTC has formed partnerships with Hyundai, Nissan and BMW. By July of 2005, an s500 UTC fuel cell had provided a Nissan X-Trail with power to take the vehicle for 25,000 trouble-free kilometers over a wide range of road conditions. Busses have also been UTC fuel cell-powered. Necessary test bench and road durability data is beginning to positively answer the ‘where’ question for automotive and industrial applications.
The ‘when’ question: This question has a broad answer because in certain applications such as aerospace and large power generation, there are already units in operation. But to look at the big transportation and industrial markets, the arrival is still in the future. Besides durability, the big hurdle is cost. Here the promise of a simpler system with MP technology could be a bright new contributor to bring costs down. With targets of two orders of magnitude of price reduction needed, the question centers on the size of the decrease which will initiate market acceptance. Convergence of lower fuel cell costs, increasing oil prices and growing global warming are all forces for the success of fuel cells and a hydrogen economy. UTC Fuel Cells Microporous Plate technology is facilitating that success.
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Comments from the author...
The major barriers to the commercialization of fuel cells continue to be cost and lifetime. However, I am very optimistic about the successful commercialization of PEM fuel cells because they have already demonstrated most of the technical attributes required to be viable in a wide variety of applications. Because PEM cells have high power density and rapid start-up times, they are suitable for transportation applications, as well as stationary applications. This ability to be used in a variety of applications, including some niche applications where batteries are dominant today, will allow PEM fuel cells to begin to generate the production volumes required to further reduce their cost.
This is a key differentiator for PEM relative to previously developed fuel-cell types,  which have attributes that prevented their successful deployment in many applications. For example, phosphoric-acid fuel cells (PAFC) were developed by UTC into an excellent stationary power plant that operates reliably for over 40,000 hours on natural gas. However, the modest power density and extremely long start-up time required prevents this technology from being seriously considered for transportation or back-up power applications. Similarly, alkaline fuel cells (AFC) were successfully developed by UTC for NASA’s manned space missions, but their inherent intolerance to carbon dioxide makes them unattractive for most terrestrial applications. These limited markets also limited their ability to grow in volume and thereby reduce cost. The ability to be suitable for a variety of applications is very important; just look at the investment that the auto companies are making in PEM today because of the progress that has been demonstrated to date.
In terms of lifetime, UTC has been making tremendous progress in this area with our proprietary water-management technology. The key to lifetime in a PEM cell is essentially effective water management and UTC’s passive system has shown excellent results in both steady-state and transient operations. In many respects, lifetime challenges in PEM are much less challenging than in PAFC because the operating temperature is much lower (~ 80 C vs. 200 C).
Lastly, I would like to emphasize that all fuel-cell power plants should ideally be hybrid systems (i.e., fuel cells combined with some form of energy storage such as batteries and/or super capacitors). Such all-electric power hybrids are relatively simple in comparison to the mechanical/electrical hybrid cars being sold today. And, the advantages are tremendous (e.g., improved efficiency, faster transient response capability, reduced size and cost, etc.). So, not only will fuel cells never displace batteries in most applications where batteries are used today (e.g., where run times are short and recharging is acceptable), but they will also be combined with their electrochemical cousins to make the best products. Therefore, as fuel cells begin to displace the internal-combustion engine (in the more distant future), hybrid-type batteries should benefit as well.
Mike L. Perry
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