Lifetimes, of fuel-cell

Besides activity, durability of metal electrode nano-catalysts in acid medium has become one of the most important challenges of low-temperature fuel cell technologies. It has been reported that platinum electrode surface area loss significantly shortens the lifetime of fuel cells. In recent years, platinum-based alloys, used as cathode electrocatalysts, have been found to possess enhanced stability compared to pure Pt. The phenomenon is quite unusual, because alloy metals, such as Fe, Co and Ni, generally exhibit greater chemical and electrochemical activities than pure Pt. Some studies have revealed that the surface stmcture of these alloys differs considerably from that in the bulk A pure Pt-skin is formed in the outmost layer of the alloys due to surface segrega-... 

The performance and lifetime of fuel cells and batteries can often be determined by the structural features (and their change) of the various components. Structural studies of these systems are generally very difficult... 

To predict the possible lifetime of fuel cell plants already in operation... 

Another fuel cell design is the molten carbonate fuel cell (MCFC) (Yuh, 1995), which operates in the temperature range 620-660°C with an efficiency of >50%. FuelCell Energy, Inc. (Danbury, CT) produces MCEC units. These units are designed as back-up generators for intermittent use. The operational lifetimes of fuel cell systems need to be extended. In order to do so, it is necessary to limit component corrosion. 

Type of fuel cell Operating fuel and temperature Power rating (kW) Fuel efficiency s (%) Power density (mW/cm ) Lifetime s (hr) Capital cost s ( /kW) Applications... 

Fuel cells based on unmediated electrocatalysis by heme-containing sugar dehydrogenases have not yet been tested in biological fluids, but may be useful for implantable applications, as they avoid the need for toxic or expensive mediators and have minimal design constraints. Realistically, the lifetime of biofuel cells is still insufficient for biomedical applications requiring surgical installation. 

In general, technical developments will lead to a decrease in overall costs of this technology per unit of installed generating capacity (kWe). Some types of fuel cells need to achieve higher power densities per kg weight or m3 most need to increase lifetimes of stacks or other plant components. For smaller applications, the technology must reach a reliable level sufficient to allow the plants to operate unattended. 

As mentioned above, fuel cells may be used for mobile, stationary and portable applications. Table 13.4 shows the currents status of fuel cells for the three respective fields of application in terms of specific investment, lifetime and system efficiency as well as target values for the future. 

The key question for mobilising further market potential is whether a steady decrease in fuel-cell costs and an increase in lifetime can be achieved. Many energy technologists believe the future of the different types of fuel cell to be very bright because of anticipated efficiency improvements and the low emissions associated... 

Rather, the success of fuel cell technology hinges on major breakthroughs, not incremental improvements, in design and implementation of advanced materials that are specifically optimized to meet targets in performance, operating conditions, lifetime, and cost. In particular, the required improvements would be impossible without advances in the... 

Lastly, cost is a crucial issue in the commercialization of fuel cells, particularly as performance and lifetimes have improved to the threshold of practicability. The major costs associated with these systems are materials-related, with separator and catalyst materials at the top of the list. It is envisioned that the cost of separator materials will decrease with increased production and competition and as alternative materials are perfected. However, the cost of conventional noble metal catalysts, particularly platinum, is expected only to increase with increased production and demand. Therefore, the cost issue could perhaps be addressed by employing alternative catalysts, including biocatalysts. Enzymes are de-... 

The steam electrolysis at high temperature (600-800°C) features a potential efficiency of -100% LHV with extra heat available. Its technology benefits from current developments made of solid oxide fuel cells. However, many uncertainties and issues remain to achieve a commercial viability. Prominent issues include improving the reliability and the lifetime of electrolytic cells and stack of cells and decreasing the investment and operating costs with a view to decreasing the currently estimated production cost from 4 to about EUR 2/kg H2 [from 5.2 to about USD 2.6/kg H2],... 

Molten carbonates, however, do have disadvantages. The fuel cell takes a considerable amount of time to reach its high operating temperature, so it is unsuitable for powering a car or truck. The liquid carbonate electrolyte is very corrosive, so there is some question about the lifetime these fuel cells will be able to achieve. They are also very bulky The 250 kW units are the size of a railroad car and weigh about forty tons. 

Types of Fuel Cell Power Rating Fuel Efficiency Power Density Lifetime Capital Cost Applications... 

Figure 3.11. Estimated effect of fuel-cell lifetime on the target cost for competitive commercialisation (Staffed etal., 2007)...

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