Performance and durability

Once the rehabilitation materials are chosen, the joint design can be properly addressed. There are many factors that must be considered in the design of a bonded joint. In addition to the most evident ones (like the geometry of the area to be bonded, the properties and characteristics of the bonding materials, and the stresses to which the bonded joint will be subjected while in service), several others exist that may also condition the joint design. The design of the bonded joint should then maximize the bonded area, introduce tensions in the direction of maximum strength of the bonded joint (eg., shear 

The practical execution of the rehabilitation intervention includes the reception, storage, preparation and application of the SA and APC materials, as well as the curing of the adhesive materials. Site work should be carried out by well-informed, trained, experienced and certificated operatives, under the supervision of a qualified site manager to ensure eompliance with the specifications of the quality plan and to ensure a satisfaetory intervention programme (Petrie, 2006 Silva et al., 2011 Adams et al., 1997 Mays and Hutchinson, 1992). 

The condition of the materials that arrive at the work site should be assessed and recorded to guarantee that they ate in perfeet eondition so that if handled properly they will be able to produce rehabilitation work with adequate performance and durability. This verification also serves to confirm that the correct products have been delivered to meet project specifications and that they are under the expiry date. The storage of the materials is also very important and it should follow strictly the supplier or manufacturer indications present in the manufacturer s or supplier s Product Data Sheet. Generally, all adhesives and APC materials should be stored in a cool, dry place until they are used. While some materials are very tolerant to storage conditions, there are others that may have to be stored at low temperature or under special conditions. For instance, some adhesive systems are affected by light or moisture and others require periodic agitation to ensure that their components do not settle irreversibly (Petrie, 2006 Silva et a/., 2011 Adams et al., 1997 Mays and Hutchinson, 1992). 

Once the rehabilitation work has been completed, an inspection should be carried out to detect flaws or defects. The inspection may comprise destructive or non destructive tests. The non-destructive tests can be performed either visually or through the use of advanced analytical equipment. The destructive tests consist of tests on standard control samples, tests on prototype systems, and tests on selected areas (IStructE, 1999 Mays and Hutchinson, 1992 Petrie, 2006). 

The rehabilitation work should also include a plan for the monitoring of the rehabilitation intervention during its service life to ensure that the structure will be able to perform according to planning for its intended service life. 

Most of the evaluations on a stack are similar to those on a single cell. The V-I polarization curve is used to eshmate the stack s performance from lower to middle and to higher current densities. Parameters such as the humidi-ficahon temperature, temperatures of the coolant at the stack inlet and the outlet, the coolant flow rate, the reactant stoichiometric ratio, and the RH should be optimized through experiments. The compression force on the stack assembly should seal the stack but not cause damage to the GDM. 

If a newly built stack shows problems, they are often related to reactant leakage, either internally or externally, due to improper seal or misalignment of some components. After the problems are identified, the stack can be fixed. It is worth the effort to fix the stack because the key components, such as the PEM and the catalysts, are new and have the potential to operate for thousands of hours. 

Lifetime Targets and Maximum Allowable Decay Rates of Fuel Cells for Different Applications  

For different applications, there are different lifetime requirements. If the BOL cell voltage is 0.70 V, and the designed EOL cell voltage is 0.55 V, the required decay rate limits are summarized in Table 4.3. 

It can be seen from Table 4.3 that the current technology is more than enough to meet the backup power requirements, and adequate for cars, and reachable for buses and portable applications (using DMFCs), but difficult for stationary applications. In August of 2011, a bus developed by UTC reached 10,000 hours of cumulated operation time without replacement of the stack. 

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Defining hydrogen fuel quality specifications is a high priority for the Roadmap. Such specifications must be quantified at the vehicle-station interface and must consider how the presence of small amounts of contaminants affects the performance and durability of fuel cell and balance of plant material compatibility of onboard and stationary hydrogen storage systems and the operation and maintenance of hydrogen production, purification, and delivery systems. Most importantly, fuel quality specification must consider... 

In addition to the performance and durability of the fuel cells fabricated, cost is also an extremely important consideration in the decision of whether or not to adopt... 

A commercial-scale Improved B-1, with a capacity of 10 000 metric tonnes per year (caustic base), came into operation successfully at the AGC Kashima factory in July 1999. Since then, the plant has demonstrated a long-run operation to prove its stable performance and durability under high current density. For the first 3 months, the electrolyser was operated at 5kA m-2. Then the current density was increased step by step up to 7kA m-2. An Fx-8964 membrane, which had just been developed as one of the optional membranes for high current density, was installed. The operation was observed to be stable for each current density. As is shown in Fig. 19.7, the power consumption at present is approximately 2300 (d.c.) kWh tonne-1 at 7 kA m-2. 

Once the plate starts to corrode, many problems appear to affect performance and durability, even serious failure, of fhe fuel cells. For example, fhe interface contact resistance between the corroded metal plates and GDL will increase to reduce the power output. The corrosion products (mainly various cations) will contaminate the catalyst and membrane and affect eir normal functions because the polymer membrane essentially is a strong cation exchanger and the catalyst is susceptible to the ion impurity. Hence, adding a corrosion-resistant coating to the metal plate will almost inevitably assure the performance and long-term durability of a sfack. 

Development of New Materials with Better Performance and Durability... 

Mepsted, G. O., and J. M. Moore. 2003. Performance and durability of bipolar plate materials. In Handbook of fuel cells—Fundamentals, technologies, and applications, ed. W. Vielstich, H. A. Gasteiger, and A. Lamm. Vol. 3 Fuel cell technologies and applications, 286-293 (chap. 24). New York John Wiley Sons. 

The Effect of Halogens on the Performance and Durability of Reverse-Osmosis Membranes... 

Standard Methods fot the Exahmiation of Water and Waste Water XIV Edition - APHA, AWWA, WPCF, Part 909, 928 and following. Glater, J., Effect of Halogens on Performance and Durability of RO Membranes, presented at 2nd Chemical Congress of the North American Continent, Las Vegas, 1980. 

No.7, July 2003, p.84-5 MULTI-LAYER POLYPROPYLENE SYSTEM IMPROVES THERMAL PERFORMANCE AND DURABILITY... 

To avoid misleading results, the electronic characteristics of a device always have to be analyzed in a proper statistical manner to characterize the results of the process in terms of device structure details, yield, electrical performance, and durability. 

A few demonstrations of phosphoric acid fuel cells were carried out to evaluate and validate the performance and durability of small on-site co-generation systems, including 50 kW at Eniricerche in Milan and 200 kW at ACoSeR in Bologna. 

D. A. Becker, ed., Joint Conference on Measurements and Standards for Recycled Oil/ Systems Performance and Durability, NBS Special Publication 584, National Bureau of Standards, Washington, D.C., Nov. 1980. 

The chemical sensitivity or life expectancy of reverse osmosis membranes is very important for manufacturing application. Thus chlorine is the most well known reagent for water disinfection. Glaster et al. 61 inspected the influence of halogens on the performance and durability of reverse osmosis membranes. Cellulose acetate was unresponsive to halogen agents but polyamide-type membranes deteriorated rapidly when exposed to halogens. 

W. M. Burkmyre, W. E. Liss, and M. Church, Natural Gas Converter Performance and Durability, SAE 930222, Society of Automotive Engineers, Warrendale, Pa., 1993. 

Proper water management in proton exchange membrane fuel cells (PEMFCs) is critical to PEMFC performance and durability. PEMFC performance is impaired if the membrane has insufficient water for proton conduction or if the open pore space of the gas diffusion layer (GDL) and catalyst layer (CL) or the gas flow channels becomes saturated with liquid water, there is a reduction in reactant flow to the active catalyst sites. PEMFC durability is reduced if water is left in the CL during freeze/thaw cycling which can result in CL or GDL separation from the membrane,1 and excess water in contact with the membrane can result in accelerated membrane thinning.2... 

In Table 1, the consequences of requiring large areas for collection, the cost because of competition with currently available energy forms, materials specificity for performance, and durability (to reduce life-cycle costs) are summarized. These criteria dictate a multilayer stack collector design in which polycrystalline thin film(s) of the active material must be protected from a hostile terrestrial environment. 

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