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A simple mathematical model is presented for a box-type solar cooker with outer-inner reflectors. It is based on analytical solution of the energy-balance equations for different elements of the cooker. The cooker performance is investigated by computer simulation in terms of the cooker efficiency as well as characteristic and specific boiling times. Numerical calculations have been carried out...
About 50% of the primary energy supply in The Netherlands is used for heat production. To achieve a sustainable heat-supply system, it is necessary to obtain insight into costs, efficiency and environmental impacts for existing and possible future technologies. We have performed a comparative system analysis on six possible heat-supply chains (distribution and conversion) providing low-temperature...
Univariate Box-Jenkins time-series analysis has been used for modeling and forcasting monthly domestic electric energy consumption in the Eastern Province of Saudi Arabia. Autoregressive integrated moving average (ARIMA) models were developed using data for 5 yr and evaluated on forecasting new data for the sixth year. The optimum model derived is a multiplicative combination of seasonal and nonseasonal...
A method based on fractal geometry is suggested to simulate the porous structure of calcined limestone, in which a model similar to the Menger sponge is employed for the porous calcine. The bulk fractal dimension is calculated on the basis of the experimentally obtained poresize distribution density. The effects of various factors (such as particle size, calcination temperature and environment,...
The praseodymium oxide redox system releases and incorporates oxygen into an inert gas. Reductions of Pr 6 O 11 to Pr 5 O 9 and Pr 5 O 9 to Pr 9 O 16 were analyzed while heating a mixture of air with N 2 at O 2 partial pressures of 2 10 2 -6 10 3 Pa from 373 to 833 K. Oxidations of Pr...
Developing countries of Asia account for most of the world's animal population. The animal wastes produced annually in these countries constitute a major source of methane and other greenhouse gases (GHG). For 23 countries of Asia, we estimate that 17,730 Gg of CH 4 , 1,290.000 Gg of CO 2 and 179 Gg of N 2 O are emitted from animal wastes. Using the biogas that can be produced...
Fluidized-bed combustion of coal has been investigated in a pilot-plant combustion facility. The test bed section has an internal diameter of 0.154 m and an overall height of 3.5 m. Sand with an average particle diameter of 1421 μm is used as inert bed material. The inert bed is heated to a temperature of about 1000 K by two propane burners installed in the preheater and calming sections. Experiments...
We present a new exergoeconomic approach to optimize energy systems. After tracing the energy evolution and degradation within the system, a binary subsystem model is proposed and optimization strategies are introduced. The method is applied to optimization of the CGAM problem.
Redox systems of iron-based oxides (ferrites) mixed with coal powder have been studied to determine the most reactive and selective working materials for thermochemical conversion of coal and water to CO and H 2 . Reactions were performed in a two-step redox cycle in which the ferrites were reacted with coal powder at 900°C to produce CO, H 2 , and reduced ferrites (coal-gasification...
The design concept and optimization procedure are presented. The total heat load for both systems at peak conditions is estimated to be 1,216 MJ/s in 2001. The thermal power plant consists of six steam-condensing units with a total electric capacity of 1650 MW e at the generator terminals. It will be converted for CHP operation and will supply heat to both systems. The energy-efficiency...
We present a new approach which identifies the number of customers within particular categories living in a chosen area of energy supply. This identification is made from total energy consumption measured at distribution feeders by applying characteristic patterns of energy use and nonlinear programming techniques. Customers were segmented into four main categories with six sub-groups in each category...
The fate of CO 2 hydrate disposed of in the ocean is analyzed based on thermodynamic theory. It is found that CO 2 hydrate and seawater form a stable system only when (a) the system pressure p and temperature T fall within the hydrate-formation region in the ocean (i.e. p > 4.5 MPa and T < 283 K) and (b) seawater is saturated or supersaturated with respect to CO 2 ....
Current practices for operation of a water-chilling plant (WCP) in the cement product industry in Kuwait have been studied and evaluated under different load conditions. Experimental results and weather data are used to demonstrate deficiencies in the present design. An analysis has been conducted to arrive at the optimum use of a cooling tower (CT) and chillers for year-round application. A significantly...
We analyze determinants of technology diffusion in the European electric utility sector during the period 1950-1992. Structural, economic, technological, and institutional features were introduced into a hazard model. Kaplan-Meier functions were used for non-parametric estimations.
An air-to-earth heat exchanger (ATEHE) consists of pipes buried in soil. We have evaluated the technical and economic performance of an ATEHE coupled to the system for heating or cooling of a building that uses 100% fresh air as heating or cooling medium during winter and summer. The soil is divided into elementary layers. The problem solved, is non stationary; however, steady state-energy equations...
This theoretical study deals with a domestic heating system assisted by solar energy stored in an underground spherical container. The system includes a heat pump. The analytical model employed calculates the water temperature in the storage vessel, as well as the temperature distribution in the surrounding geological structure, by using the monthly-average solar radiation and ambient temperature...
When an amount of high-temperature molten material is suddenly and finely mixed with a body of liquid water, the ensuing mixture expands because of the volumetric generation of steam. At the same time, the expanding mixture is accelerated away from the surfaces with which it comes in contact. In this paper, we address the fundamental thermodynamic aspects of the energy-conversion process, with emphases...
A stratification sampling method has been applied to investigate 384 households in 12 villages of four towns in Yangzhong county. Responses to a questionnaire show that the average annual energy consumption per rural household is 298.7 kgce (we use 7000 kcal/kgce), with average energy of 0.59 kgce per day mainly in the form of straw. The average energy consumption depends on income, stalk yield,...
MODEST, an energy-system optimisation model is described. It has been applied to a typical local Swedish electricity and district-heating utility and to the national power system. Present and potential installations and energy flows should be considered and their best combination can be obtained through optimisation. MODEST uses linear programming to minimise the capital and operation costs of...
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