RAPS System Components

As their name suggests, RAPS systems are expected to operate reliably in a variety of inhospitable environments. They can be confronted with the searing heat of the desert, the stifling humidity of the rainforests, or the intense cold of the tundra. The facilities may even be sited on oceans or atop mountains. The systems service a diverse range of applications with widely different levels of energy consumption, such as (i) houses and villages (ii) electric fences (iii) community dwellings and services  

RAPS systems capable of supplying continuous power must have either a diesel generator in constant operation and/or a battery bank. If renewable energy is abundant, RAPS systems can also include a photovoltaic (PV) array, a wind generator, and/or a hydro-generator. An inverter to convert direct current (d.c.) to 

Other battery systems that have been suggested for use in RAPS facilities include zinc-bromine [7], vanadium redox [8], and aluminium-air [9]. It is considered unlikely, however, that these systems will be used in mainstream RAPS applications as their cost is still significantly higher than that of lead-acid alternatives, and their long-term reliability has yet to be proven. 

In terms of life-cycle costs, batteries are usually the most expensive component of a RAPS system and, therefore, it is advantageous to minimize the required capacity. The battery should, however, be sized to supply a significant portion of the anticipated daily load in the absence of diesel- or PV-generated power, e.g., from 20 to 50%. This would allow the diesel to remain idle for much of the day and to operate under relatively constant, high-load conditions for only a few hours each day. Further, the battery should be sized such that the daily depth-of-discharge (DoD) is limited in the interest of enhancing battery cycle-life. (The cycle-life of a battery is affected by several factors which include DoD, temperature, and charging procedure.) 

Diesel generators are the energy source for many RAPS systems. Such units consist of an internal combustion engine (fuelled by diesel oil) and an alternator that produces a.c. power. Generators that deliver d.c. power have also been used, but they are no longer common as they are not as efficient as their a.c. counterparts. Petrol generators can also be employed for RAPS duty, but they have greater maintenance requirements and are more expensive to operate. 

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The reduced tendency of VRLA batteries to exhibit stratification (and, the consequent reduced need for overcharge), can represent a benefit in terms of a decrease in both positive-grid corrosion and charging time. This acts to increase the life of the RAPS system components and also improves the efficiency of the system, especially when a diesel generator is included. 

RAPS systems that incorporate a component of renewable energy generally require battery energy-storage. Examples of such systems, together with their application and associated service, are summarized in Table 14.1. 

Among the multivariate statistical techniques that have been used as source-receptor models, factor analysis is the most widely employed. The basic objective of factor analysis is to allow the variation within a set of data to determine the number of independent causalities, i.e. sources of particles. It also permits the combination of the measured variables into new axes for the system that can be related to specific particle sources. The principles of factor analysis are reviewed and the principal components method is illustrated by the reanalysis of aerosol composition results from Charleston, West Virginia. An alternative approach to factor analysis. Target Transformation Factor Analysis, is introduced and its application to a subset of particle composition data from the Regional Air Pollution Study (RAPS) of St. Louis, Missouri is presented. 

The Remedial Action Priority System (RAPS) and Multimedia Environmental Pollutant Assessment System (MEPAS) are different names for an objective exposure pathway evaluation system developed by Pacific Northwest Laboratory to rank chemical and radioactive releases according to their potential human health impacts. Constituent migration and impact are simulated using air, groundwater, overland, surface water, and exposure components based on standard assessment principles and techniques. A shell allows interactive description of the environmental problem to be evaluated, defines required data in the form of problem-specific worksheets, and allows data input. The assessment methodology uses an extensive constituent database as a consistent source of chemical, physical, and health-related parameters. 

Pacific Northwest Laboratory has developed health impact assessment systems, the Remedial Action Priority System (RAPS) and the Multimedia Environmental Pollutant Assessment System (MEPAS), for the U.S. Department of Energy (DOE) to evaluate the relative importance of environmental problems. RAPS, which was developed first, applies to releases from inactive waste sites. MEPAS, the most recent version of the system, allows consideration of releases from both active and inactive sites. MEPAS differs from RAPS mainly in terms of the types of emission options. Although MEPAS retains the documented framework of RAPS (1), several enhancements have been added to the transport and exposure components (2). 

The APIOOO D-RAP identifies those SSCs that should be given priority in maintaining their reliability through surveillanee, maintenanee, and quality control actions during plant operation. The PRA importanee and sensitivity analyses identify those systems and eomponents important in plant risk in terms of either risk inerease (for example, what happens to plant risk if a system or eomponent, or a train is unavailable), or in terms of risk decrease (for example, what happens to plant risk if a eomponent or a train is perfectly reliable/available). This ranking of components and systems in such a way provides an input for the reliability assurance program. For more information on the APIOOO reliability assurance programme, refer to Section 17.4 of Reference 5.6. 

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