Fuel Cell/PEM/UTC page 050917
From the Fuel Cells 2005 conference...
Porous Plate Technology Advances PEM Fuel Cell Performance, Durability and Cost Effectiveness
Reviewed by Donald Georgi
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.
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.
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.
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.
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.
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.
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.
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.)
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.