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The effect of collector aspect ratio of the collector efficiency of flat-plate solar air heaters has been investigated theoretically and experimentally. With constant collector area, the collector efficiency increases when the collector aspect ratio increases. The theoretical predictions agree reasonably well with experimental results.
The first and second laws of thermodynamics have been utilized to optimize the convective heat transfer in a packed duct with constant wall temperatures. Introducing packing into the fluid-flow passage increases the wall-to-fluid heat transfer considerably and hence reduces entropy generation due to heat transfer across a finite temperature difference; at the same time, entropy generation due to...
A mathematical model is described of an intermittent, solar-powered, solid-absorption refrigerator using CaCl 2 as absorbent and NH 3 as refrigerant. Finite difference forms of the governing equations were written in BASIC. Real performance data are used to test the model. The peak-tube temperature is predicted within 4%. The onset and termination of generation and the mass of...
We show in this study that a full fuel-cycle analysis of the greenhouse gas (CO 2 ) implications of biomass energy systems has not only to take into account the inputs and outputs of energy (and associated carbon content) but must recognize that many biomass systems have by-products that are produced along with the biofuel. The analysis must also account for the temporal variability of carbon...
Atmospheric As, Cd, Pb, and Zn emissions from coal combustion in the Upper Oder River Basin (Poland) have been estimated for the period 1989-1992. The main power and heating plants achieved reductions of more than 40% while energy production remained unchanged. Power plants equipped with stoker-fired boilers or incorporated in industrial plants were relatively heavy polluters per unit of output energy...
Replacing fossil fuels with sustainably-produced biomass will reduce the net flow of CO 2 to the atmosphere. We express the efficiency of this substitution in reduced emissions per unit of used land or biomass and in costs of the substitution per tonne of C. The substitution costs are calculated as the cost difference between continued use of fossil fuels at current prices and the use of...
We introduce a safe and permanent method of CO 2 disposal based on combining CO 2 chemically with abundant raw materials to form stable carbonate minerals. Substantial heat is liberated in the overall chemical reaction so that cost will be determined by the simplicity and speed of the reaction rather than the cost of energy. Preliminary investigations have been conducted on two types...
A new multiple-resistivity drift-region structure which leads to an improvement of the on-resistance of high voltage LDMOS devices is proposed. The distinctive feature of the novel structure is the low sensitivity of the breakdown voltage to process variations. The important parameters of the structure such as on-resistance, threshold voltage and punchthrough voltage in the channel are discussed,...
We discuss some methodological and application issues related to decomposing national industrial energy consumption into changes associated with aggregate industrial production level, production structure and sectoral energy intensity. Past studies are classified and reviewed with respect to study scope and decomposition technique. A framework for decomposition method formulation which incorporates...
The design and performance of the Ghazlan power plant (Kingdom of Saudi Arabia) are described. The study is based on first- and second-law analyses. A full energy analysis is carried out to identify the potential for improving the plant efficiency. The energy analysis shows a detailed breakdown of energy losses for the different plant components. Alternative arrangements to improve the efficiency...
We have performed an evaluation of the end-use price of photovoltaically produced hydrogen. Our evaluation is optimistic as current estimates of photovoltaic energy costs by other authors generally correspond to higher figures, and evaluations of process and transportation costs have usually taken into account only the main components. Hydrogen is considered to be tax-free. A more realistic evaluation...
A new multiple-resistivity drift-region structure which leads to an improvement of the on-resistance of high voltage LDMOS devices is proposed. The distinctive feature of the novel structure is the low sensitivity of the breakdown voltage to process variations. The important parameters of the structure such as on-resistance, threshold voltage and punchthrough voltage in the channel are discussed,...
The effect of slat angle and absorptance on the heating and cooling loads of buildings in Seoul (South Korea) has been studied. An analytical model of a window system with venetian blinds is developed and validated with published experimental data. The validated model has been successfully incorporated into the TRNSYS computer program. Hour-by-hour heating/cooling loads of a typical building, with...
We examine the experiences that states and utilities are having with the NLRA approach. Contrary to concerns raised by some industry analysts, our results indicate the NLRA is a feasible approach to the lost-revenue disincentive. Seven of the 10 states we studied report no substantial problems with their approach. We observe several conditions linked to effective NLRA implementation and, for those...
We have developed an algorithm to disaggregate short-interval (hourly) whole-building electrical load into major end uses. Hourly load data, hourly load-temperature regression coefficients and simulation end-use results comprise the algorithm input. The algorithm produces hourly load profiles for air conditioning, lighting, fans and pumps, and miscellaneous loads. Measured data from two end-use...
An optimal performance analysis of a combined Carnot cycle (two single Carnot cycles in a cascade), including internal irreversibility for steady state operation, has been carried out. It is shown that the effects of internal irreversibility on maximum power may be characterized by two cycle-irreversibility parameters representing the ratios of the entropy differences for each of the cycles. The...
During the past 20 years, responses to the 1973 Arab oil embargo and the subsequent unprecedented world-oil price increases established by the Organization of Petroleum Exporting Countries by oil-poor member countries of the OECD, such as France, Germany, Italy, Japan, and Sweden, have spawned formidable competitors in the global energy-technology marketplace for U.S. firms. Protection from the economic...
Strategies for reductions of emissions and depositions are described, with special regard for countries in transition. The influences of structural changes and energy-saving measures, as well as the effects of reductions of multiple pollutants, are analyzed for four countries in Central and Eastern Europe and for different scenarios with varying final energy demands, assumed CO 2 -emission...
The electricity market in Sweden is changing from being a geographic monopoly to allowing competition in areas other than transmission and distribution. When it was announced that the rules were about to change, a conflict arose between two of the larger generators concerning which of them should transmit electricity to a nearby distributor. The arguments used coincide with market theory but not...
A first- and second-law analysis is presented for a process developed for simultaneous generation of a fuel gas and electric power (gas and power cogeneration) based on atmospheric circulating-fluidized-bed (ACFB) combustion of coal. The mathematical model has a zone structure, multi-species equilibrium calculations for applicable zone conditions at high temperatures (50 gas-phase and seven solid-phase...
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