[en] The purpose of this paper is to define a finite-time closed Brayton cycle and apply it to optimize an indirect gas-cooled nuclear reactor plant. Practical engineering heat engine power optimization usually takes the form of determining minimum heat exchanger area per unit net power output or minimum cost per unit power output, rather than determining the maximum cycle efficiency. The objective function of the optimization described in this paper is specific power, power output per total heat exchanger surface area. The specific power output of a real indirect gas-cooled nuclear reactor plant coupled with its heat source and sink is analyzed. It is found that there is an upper bound on the specific power output of the nuclear power plant. This bound can guide the evaluation of existing real plants or influence design of future power plants. (author)

[en] Sensitivity analysis is carried out to validate model formulation. A modified model has been developed to predict the future energy requirement of coal, oil and electricity, considering price, income, technological and environmental factors. The impact and sensitivity of the independent variables on the dependent variable are analysed. The error distribution pattern in the modified model as compared to a conventional time series model indicated the absence of clusters. The residual plot of the modified model showed no distinct pattern of variation. The percentage variation of error in the conventional time series model for coal and oil ranges from -20% to +20%, while for electricity it ranges from -80% to +20%. However, in the case of the modified model the percentage variation in error is greatly reduced - for coal it ranges from -0.25% to +0.15%, for oil -0.6% to +0.6% and for electricity it ranges from -10% to +10%. The upper and lower limit consumption levels at 95% confidence is determined. The consumption at varying percentage changes in price and population are analysed. The gap between the modified model predictions at varying percentage changes in price and population over the years from 1990 to 2001 is found to be increasing. This is because of the increasing rate of energy consumption over the years and also the confidence level decreases as the projection is made far into the future. (author)

[en] A study was conducted to evaluate the performance of silicon photovoltaic systems exposed to isotropic irradiation by protons and electrons which approximate the effects of space irradiation. In addition to the normal damage mechanism of lifetime degradation in the base region, another important damage mechanism of series resistance increase was produced by the particles incident. Significant degradation was experienced in the output characteristics of cells after bombardment with either protons fluence (10¹⁴-10¹⁶ p/cm²) within the energy range from 0.6 to 6.0 MeV or electron fluences up to 1 x 10¹³ electron/cm² at energies up to 12 MeV. For low energy protons (from 0.6 MeV to 2.0 MeV), the damage rate per particle decreases as the energy increases. Computer programs were developed to solve the general equations for solar cells and to introduce the radiation effects upon their performances. (author)

[en] Pico hydro power is a renewable energy system which has the potential to provide millions of rural people world-wide with a cheap, sustainable source of electricity. The development of new, cost-reducing approaches, including local manufacture and implementation in developing countries, has increased the accessibility of this technology to large numbers of people. The new approaches are investigated and some of the present constraints to wider adoption of this technology are analysed. (Author)

[en] Short Rotational Coppice is an energy crop that can be grown on surplus agricultural land for energy production. It can be used in wood burning gasifiers for production of electricity and this process is well documented. The logistics of collecting wood chips from the production site and delivering to a central sustained power station are complex and the costs not inconsiderable. The need for a method of assessing the economics of short rotational coppicing for gasification and on site electricity production are recognised. For this reason a flexible spreadsheet was developed to calculate the costs and profitability of the crop. The spreadsheet was designed to be adjustable to suit particular circumstances of any given project. The results of this calculation can be used as an indicator to whether the project is viable or not. The program requires input data such as agricultural expenditure, including preparation and harvesting costs. Capital costs for the gasifier, filtration units and generator connection charges are included. A maintenance program is also required to ensure continuous smooth running, although unexpected failure may occur with extra costs and power loss not accounted for. Using the spreadsheet it will be possible to compare different parameters such as land area used, generator efficiency, fuel calorific value and preparation costs. (author)

[en] In the UK, about 30 million tonnes of Municipal Solid Waste (MSW) is generated each year and the disposal of this waste has become a national problem. The growing scarcity of landfill sites for municipal solid waste disposal and the increasing environmental problems with landfill waste has led to more stringent regulations and high cost of waste disposal. The landfill tax in the UK is designed to encourage energy efficient waste management strategies aimed at reducing the amount of waste to be landfilled through incineration while maximising the recovery of the waste energy. Efficient recovery of energy from waste is therefore an important aim for modern incinerator design. The incineration of MSW is known to be a very complex process since the waste is poorly specified and its composition varies from moment to moment. Hence, the research into waste combustion is fundamental to rational incinerator operation and the evolution of innovative processes such as co-incineration and integrated incinerator/gas turbine plants. This paper reviews the current research activities at Sheffield University Waste Incineration Centre (SUWIC) in MSW incineration. (Author)

[en] In this study changes in the surface pressure field over Europe are analysed to see if they are reflected in the statistical structure of the wind field over the Great Hungarian Plain. The data base consists of hourly wind speed data of three meteorological stations (Debrecen, Bekescsaba and Szeged) at the Great Hungarian Plain, coming from the periods between 1968-72 and 1991-95, respectively. A new statistical test is also shown in the paper, in order to apply it for determining significance of statistical differences between expected values of non-independent time series. Decrease of wind energy might be expected at the Great Hungarian Plain, however no definite results were obtained on the data base considered. (author)

[en] A Green Certificate (GC) is a 'document' that proves that a unit of electricity has been produced from a Renewable Energy (RE) source. Generators receive a certificate for reach pre-defined unit of electricity produced from their RE scheme that is delivered to the electricity network. Electricity from RE schemes is indistinguishable from other electricity, so the certificate is used to represent the 'renewableness' or the 'greenness' of a unit of the renewable energy generation. A GC becomes a Tradable Green Certificate (TGC) when the mechanism allows trading of GCs as a means of meeting an obligation. Note that for practical purposes Green Certificates are more likely to be electronic documents than paper documents. (Author)

[en] The Energy-GNP ratio in India, has an increasing trend which indicates that there is a real need for an all round increase in energy efficiency levels similar to those obtained in developed countries. As prices increase, the ratio declines for a developed country while the reverse is noticed for India. The Mathematical Programming Energy Economy Environment (MPEEE) model is developed to determine the optimum allocation of energy resources and to simultaneously reduce pollution levels. The model is run for different percentage reductions in CO₂. At various percentage reductions in CO₂, a critical electricity generation capacity is obtained using the model. The model helps to plan for the future in an economically and environmentally optimum way so as to stabilise the ratio. (Author)

[en] The aim of this study is to begin to formulate tools for comparison for policy makers, planners and designers. The great variety and diversity of renewable sources and technology makes this desirable yet difficult. The analysis is based on the degree of interference to natural energy flows which power processes in the natural environment. A sensitivity analysis could indicate the degree of tolerance to abstraction of energy. The analysis is also based on the categorisation of the environment into three sectors: inanimate, animate, and human. The analysis described represents work in progress and much of it cannot yet be validated. However, even with this raw model some interesting results emerge; harnessing diffuse natural energy flows such as wind or solar tends to result in low levels of impact to the inanimate and animate environments, but higher levels of impact to the human environment. Harnessing concentrated or high energy density flows such as hydro power results in higher impact to the animate and inanimate environments but low impact to the human environment. Wave and tidal energy fall somewhere in between. (author)