System simplification

Extrapolation of historical data to larger scale operations may overlook hazards introduced by scale up to larger equipment Limitation of fault tree tlieory requires system simplification Incompleteness in fault and event hee analysis Uncertainties in data -... 

Further system simplification would occur if a sulfur-free fuel was used or if the fuel cell were sulfur tolerant, in that case, the fuel can be provided directly from the reformer to the fuel cell. 

In order to make quantitative description of a system, simplifications have to be made. The complexity of the system, as described in the conceptual model, must be reduced to something that can be handled mathematically. Still it must be complex enough to capture the essence of the system characteristics. Obviously there is not a unique way of developing a conceptual model based on the available basic information and there is not a imique way of developing a mathematical model based on the conceptual model. 

This allows to say that the goal of system simplification of the MRX is achieved. The simplification of the systems leads to improvement of economy and reliability through the reductions of plant construction and maintenance cost, the human error during maintenance, and the probabilities of equipment failure. 

SAFETY IMPROVEMENTS INVOLVING SYSTEM SIMPLIFICATIONS AND AVAILABILITY IMPROVEMENTS... 

Figure 11.21 illustrates the principle of this new concept. Its major positive features include the realization of notable system simplification and process intensification thermal losses significantly reduced and cooling and heating steps avoided increased activity of catalysts and sorbents abatement of particulates and tar in the gasifier outlet. In all, a combination of the benefits of traditional primary and secondary hot gas treatments without... 

A small Boiling Water Reactor (BWR) design concept has been developed at GE which maximizes the use of BWR design, technology and operating experience. Modest innovations are included to simplify the performance of safety functions. These, as well as other system simplifications, and a reduced power rating less than 600 MW(e) can reduce total costs and speed construction. 

The counterpart of hard modelling is soft modelling. This theoretical approach is characterized by analytic methods with a minimum of computational efforts (soft theorists consider solved a problem when it has been reduced to quadratures) tailored models obtained by a reduced description of the system (simplification ) generality of the results which hold true usually for a large class of systems, but usually lack of specificity. 

The PSRD is an indirect cycle light water cooled tank-type small reactor with an integral design of the primary circuit. Steam generator is located inside the reactor vessel. The PSRD is designed to achieve system simplification, resulting in the reduction of costs for construction, operation and maintenance. The assessments of the plant economy are... 

System simplification no pumps in the primary and emergency core cooling systems, no accumulators and no external pressurizer or steam generator. ... 

As is well known, and as discussed by Neyerlin and others, there is an increase in polarization losses with phosphoric acid-based fuel cells, in comparison to low-temperature PFSA-based fuel cells, and this effect is thought to be due to the presence of phosphoric acid and/or its anions that adsorb onto the surface of the catalyst [47]. Because of this, high-temperature stacks based upon phosphoric acid-doped polymer electrolyte membranes are larger in order to get the same power output. The overall question is whether the benefit in system simplification overcomes the need for larger stacks, so that there is an overall net system benefit. Reducing the effect of the adsorbed anion species would, of course, have significant benefit at the stack and system levels. 

Fig. 15.22 Improvements in power density, Pt loading, and system simplification Iot last two generations of General Motors FCV stacks [24]...

Trends in short- and lOTiger-term directions for key fuel cell components including electrocatalysts/supports, membranes, and bipolar plates have been elaborated in this section improvement of the performance and durability of these components will directly impact the entire automotive fuel cell system requirements, complexity, and cost. Durable catalysts with enhanced ORR activity, durable membranes that perform at very low humidity and durable bipolar plates that have low contact resistance will not only increase the power density and cost of the fuel cell stack but also simplify and lower/eliminate system component costs of the air compressor, humidification systems, recycle pumps, radiator, start-up/shutdown and freeze-start-related components, etc. A combination of advances in all the fuel cell components discussed above, system simplification, governmental policies that are sensitive to sustainable clean energy, and development of a hydrogen infrastructure will enable achieving the projected technical and cost targets needed for automotive fuel cell commercialization. 

Further system simplification would occur if a sulfur-free fuel was used or if the fuel cell were sulfur tolerant in that case, the fuel could be provided directly from the reformer to the fuel cell. In order to minimize system volume, (and minimize the associated system weight and start-up time) integration of the system components is a key design issue. By recycling the entire anode tailgas to provide steam, a water management system can be avoided, though a hot gas recirculation system is required. 

The issue of carbon corrosion has received considerable attention in recent years. There are several drivers for this (1) the cost drivers for commercialization require the use of high performance catalysts with less durable carbon catalyst supports, (2) the need for system simplification and low cost prevents additional control systems to be implemented to avoid the carbon corrosion conditions, and (3) the use of the fuel cells subjected to "real world" conditions as opposed to carefully controlled demonstration projects, with very dynamic duty cycles and many start-up/shutdown cycles. This increased attention has resulted in new or improved measurement techniques and several studies and reviews on the high cathode potential and associated carbon corrosion mechanism [39,40,48-51]. 

Improved material robnstness to enable system simplification and cost... 

Since the economy and reliability of LWRs might also be improved, the economy and reliability of a commercial FBR must be improved still further by system simplification and rationalization. 

---