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Storage Reservoirs (storage + reservoir)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

Thermodynamic optimization of a solar system for cogeneration of water heating and absorption cooling

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2008
R. Hovsapian
Abstract This paper presents a contribution to understanding the behavior of solar-powered air conditioning and refrigeration systems with a view to determining the manner in which refrigeration rate, mass flows, heat transfer areas, and internal architecture are related. A cogeneration system consisting of a solar concentrator, a cavity-type receiver, a gas burner, and a thermal storage reservoir is devised to simultaneously produce heat (hot water) and cooling (absorption refrigerator system). A simplified mathematical model, which combines fundamental and empirical correlations, and principles of classical thermodynamics, mass and heat transfer, is developed. The proposed model is then utilized to simulate numerically the system transient and steady-state response under different operating and design conditions. A system global optimization for maximum performance (or minimum exergy destruction) in the search for minimum pull-down and pull-up times, and maximum system second law efficiency is performed with low computational time. Appropriate dimensionless groups are identified and the results are presented in normalized charts for general application. The numerical results show that the three-way maximized system second law efficiency, ,II,max,max,max, occurs when three system characteristic mass flow rates are optimally selected in general terms as dimensionless heat capacity rates, i.e. (,ss, ,wxwx, ,Hs)opt=(0.335, 0.28, 0.2). The minimum pull-down and pull-up times, and maximum second law efficiencies found with respect to the optimized operating parameters are sharp and, therefore, important to be considered in actual design. As a result, the model is expected to be a useful tool for simulation, design, and optimization of solar energy systems in the context of distributed power generation. Copyright © 2008 John Wiley & Sons, Ltd. [source]

The paleoecology and archaeology of long-term water storage in a Hohokam reservoir, southwestern Arizona, U.S.A.

GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 2 2004
James M. Bayman
Water storage reservoirs were an important feature of economic organization among ancient societies in the North American Southwest. Analyses of reservoir sediments from a Hohokam archaeological site in the Sonoran Desert yielded taxonomic species of ostracodes (microscopic crustaceans) and pollen grains that are indicative of a past water-rich environment. The discovery that this reservoir was capable of storing water on a long-term basis indicates that archaeological models for the region, which have relied on direct historic analogy, must be reexamined. In contrast to the local ethnographic record, paleoecological data generated by this study imply that the Hohokam could establish permanent desert settlements with water storage reservoirs away from perennial rivers and streams. Moreover, residents of these areas were geographically positioned to facilitate the circulation of marine resources (i.e., salt and shell) from the Gulf of California to territories within and beyond the Hohokam region. © 2004 Wiley Periodicals, Inc. [source]

The systematic approach to flooding problems,

IRRIGATION AND DRAINAGE, Issue S1 2006
J. (Hans) van Duivendijk
maîtrise des crues; mesures non-structurelles; gestion des inondations Abstract Since 1987 one of the working groups of the International Commission on Irrigation and Drainage (ICID) has, inter alia, been preparing two manuals concerning approaches to flooding problems. The Manual on Non-Structural Approaches to Flood Management was issued in 1999 while the Manual on the Planning of Structural Approaches to Flood Management has been issued recently (2005). In this paper a broad outline of both manuals is presented. The first manual describes in detail the various planning and response measures in flood management, which are known as non-structural measures. The latter are measures which alter the exposure of life and property to flooding but do not change the flood(ing) phenomenon as such. The said planning and response measures comprise such actions as floodplain land use management, flood forecasting and warning, flood fighting, flood proofing, etc. It is explained that such measures are sometimes the only ones feasible in the prevailing circumstances and that, moreover, non-structural measures should always be added to the so-called structural measures if the latter are considered feasible (i.e. feasible from a technical, economic, socio-economic and ecological point of view). In the second manual a methodology is presented for the planning of structural measures. This type of measure alters the physical characteristics of the floods and in this connection one must think of the operation of flood storage reservoirs, upstream catchment management, modification to river channels, construction of levees, special flood diversion channels (bypasses) and operation of hydraulics works. The idea behind this methodology is that it is difficult for planners and decision makers to select the appropriate flood protection system for a given situation including a range of possible floods if the problem is not approached in a systematic manner. Copyright © 2006 John Wiley & Sons, Ltd. Depuis 1987 un des groupes de travail de la CIID prépare, entre autres, deux manuels sur la manière d'approcher les problèmes d'inondation. Le ,Manuel d'approche non-structurelle de la gestion des crues' a été publié en 1999, tandis que le ,Manuel de la planification de l'approche structurelle de la gestion des crues' a été publié plus récemment (2005). Le présent article présente une vue d'ensemble de ces deux manuels. Le premier manuel donne une description détaillée des différentes mesures de préparation et de réponse à la gestion des crues, connues comme étant non-structurelles. Ces mesures changent l'exposition de la vie et des propriétés aux inondations mais ne modifient pas le phénomène proprement dit des crues et des inondations. Elles comprennent des actions telles que la gestion de l'espace dans les plaines d'inondations, les prévisions et alertes, la lutte contre les crues, la protection contre les inondations, etc. On y explique que ces mesures sont parfois les seules faisables dans les circonstances données et que, en outre, des mesures non-structurelles devraient toujours être ajoutées aux mesures dites structurelles si ces dernières sont considérées comme faisables (c'est-à-dire faisables d'un point de vue technique, économique, socio-économique et écologique). Dans le second manuel une méthodologie est présentée pour la planification des mesures structurelles. Ce type de mesures modifie les caractéristiques physiques des crues, comme par exemple réservoirs d'écrétage de crue, gestion des hauts bassins, modification des lits des fleuves, construction de digues, canaux spéciaux de déviation des crues (courts circuits) et fonctionnement d'ouvrages hydrauliques. L'idée qui est derrière cette méthodologie est qu'il est difficile aux planificateurs et aux décideurs de choisir le système de protection contre les crues correspondant exactement à une situation comprenant une large gamme d'inondations possibles si le problème n'est pas approché de manière systématique. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Responses of riparian plants to flooding in free-flowing and regulated boreal rivers: an experimental study

JOURNAL OF APPLIED ECOLOGY, Issue 6 2002
M. E. Johansson
Summary 1The long history of river regulation has resulted in extensively changed ecosystem structures and processes in rivers and their associated environments. This fact, together with changing climatic and hydrological conditions, has increased the need to recover the natural functions of rivers. To develop guidelines for river restoration, comparative ecological experiments at contrasting water-level regimes are needed. We compared growth and survival of transplanted individuals of four riparian plant species (Betula pubescens, Carex acuta, Filipendula ulmaria and Leontodon autumnalis) over 2 years on four free-flowing and four regulated riverbank sites in northern Sweden. The species were chosen as representatives of dominating life-forms and species traits on different elevations of the riverbanks. 2In Betula and Filipendula, mean proportional growth rates were significantly higher at free-flowing sites than at regulated sites, whereas no consistent differences between free-flowing and regulated sites were found in Carex and Leontodon. Differences among species were generally in accordance with natural distribution patterns along riverbank elevation gradients and with experimental evidence on flooding tolerance, although plants of all species survived and even showed positive growth rates on elevations below their natural range of occurrence. 3Partial least squares regression was used to relate plant performance (growth and survival) to duration, frequency and timing of flooding at the different sites. Flood duration and frequency typically reduced performance in all species and during all time periods, although to various degrees. Flood events early in the experiment determined the outcome to a high degree at all sites. Variables indicating a regulated regime were mostly negatively related to plant performance, whereas free-flowing regime variables were positively related to plant performance. 4We used two of the regression models generated from our data with an acceptably high predictive power to simulate a hypothetical re-regulation scenario in run-of-river impoundments. With an overall reduction in flooding duration and frequency of 50,75%, plant performance of Filipendula at low riverbank elevations showed predicted increases of about 20,30%, levelling off to zero at the highest elevations. Reductions in summer floods represented about one-third to half of this increase. 5We conclude that for a range of species individual plant performance is clearly reduced on banks of impoundments and storage reservoirs due to changes in the water-level regime. Furthermore, our model simulation suggests that rather substantial reductions of flood duration and frequency are needed to improve plant performance on riverbanks upstream from dams in impounded rivers. River restoration principles should, however, be based on a combination of experimental data on plant performance of individual species and observed long-term changes in plant communities of regulated rivers. Consequently, successful re-regulation schemes in boreal rivers should include both reductions of summer and winter floods as well as re-introduced spring floods. [source]