Applied Energy

Published by Elsevier
Online ISSN: 0306-2619
Publications
Number of survey respondents by farm type and government office region.
Potential area of SRC and miscanthus grown assuming 100% of UAA, for these farm types, is converted into these crops.  
P-values from the Chi-squared tests.
The importance profiles of the four on farm objectives; maximising profit, stewardship for the next generation, environmental and land stewardship and quality of life.  
Conditional probabilities: VI – very important, I – important, N – neutral and U + VU – unimportant and very unimportant combined.  
Article
Biomass will play a role in the UK meeting EU targets on renewable energy use. Short Rotation Coppice (SRC) and miscanthus are potential biomass feedstocks; however, supply will rely on farmer willingness to grow these crops. Despite attractive crop establishment grants for dedicated energy crops (DECs) in the UK, uptake remains low. Drawing on results from an on-farm survey with 244 English arable farmers, 81.6% (87.7%) of farmers would not consider growing miscanthus (SRC), while respectively, 17.2% (11.9%) would consider growing and 1.2% (0.4%) were currently growing these crops. Farmer age, location, land ownership, farm type, farm size and farmer education level were not significant factors in determining acceptance of DECs. The main reasons cited for not growing DECs were impacts on land quality, lack of appropriate machinery, commitment of land for a long period of time, time to financial return and profitability. Reasons cited for willingness to grow DECs included land quality, ease of crop management, commitment of land for a long period of time, and profitability. Farmers cited a range of 'moral' (e.g. should not be using land for energy crops when there is a shortage of food), land quality, knowledge, profit and current farming practice comments as reasons for not growing DECs, while those willing to grow DECs cited interest in renewable energy, willingness to consider new crops, and low labour needs as rationale for their interest. Farm business objectives indicated that maximising profit and quality of life were most frequently cited as very important objectives. Previous research in the UK indicates that farmers in arable areas are unlikely to convert large areas of land to DECs, even where these farmers have an interest and willingness to grow them. Assuming that those farmers interested in growing DECs converted 9.29% (average percentage of arable land set-aside between 1996 and 2005) of their utilised agricultural area to these crops, 50,700 ha and 89,900 ha of SRC and miscanthus would, respectively, be grown on English arable farms. While farm business objectives were not identified as key determinants of DEC acceptance, enhanced information exchange through extension agents, providing market security and considering land reversion grants post-production are potential policy considerations.
 
Conference Paper
This paper defines and simulates a closed-loop optimal control strategy for load shifting in a plant that is charged for electricity on both time-of-use (TOU) and maximum demand (MD). A model predictive control approach is used to implement the closed-loop optimal control model, and the optimization problem is solved with integer programming. The simulated control model yields near optimal switching times which reduce the IOU and MD costs. The results show a saving of 5.8% for the overall plant, and the largest portion of the saving is due to a reduction in MD. The effect of disturbances, model uncertainty and plant failure is also simulated to demonstrate the benefits of a model predictive control model.
 
Article
Metering, critically examining and if necessary modifying the energy flow through a system is desirable in order to achieve a high efficiency. Systematic procedures for energy management and audit of processes and products are suggested: they involve energy flow charts and assessment questionnaires and thereby facilitate the location, and reduction or elimination, of energy profligate sub-systems. Design rules for the improvement of energy flow systems are listed.
 
Article
The salt stratified solar pond is found to be a reliable solar collector and storage system. This paper discusses the effect of varying certain design parameters on pond steady-state temperatures. These significant parameters are sizing parameters--pond surface area and depth of the pond; operating parameters--storage volume and the heat extraction fraction; and geo-climatic parameters3solar radiation, water table depth and upper convective zone thickness. Studies indicate that there is an optimum depth and storage volume of the pond for each application in terms of temperature and heat load desired.
 
Article
This paper investigates the short-run and long-run causality issues between electricity consumption and economic growth in the selected 11 Middle East and North Africa (MENA) countries by using Autoregressive Distributed Lag (ARDL) bounds testing approach of cointegration and vector error-correction models. It employs annual data covering the period from 1971 to 2006. The unit root tests results indicate that some of the variables for Algeria, Jordan, Tunisia and United Arab Emirates do not satisfy the underlying assumptions of the ARDL bounds testing approach of cointegration methodology before proceeding to the estimation stage. Thus, we drop these countries from the ARDL bounds testing approach of cointegration and causality analysis. The cointegration test results show that there is no cointegration between the electricity consumption and the economic growth in three of the seven countries (Iran, Morocco and Syria). Thus, causal relationship cannot be estimated for these countries. However, the cointegration and causal relationship is found in four countries (Egypt, Israel, Oman and Saudi Arabia). The overall results indicate that there is no relationship between the electricity consumption and the economic growth in most of the MENA countries. Further evidence indicates that policies for energy conservation can have a little or no impact on economic growth in most of the MENA countries.
 
Article
The use of flat-plate solar collectors for the generation of electric power is attracting the attention of engineers and scientists for its simplicity in construction and operation. The efficiency of collection is low due to the low operating temperatures of the flat-plate collectors. In the low temperature range applicable to flat-plate collectors, refrigerants can be used as working fluid. The cost of construction can be reduced by the suitable selection of collector and refrigerants. It has been shown that R-114 has suitable characteristics for use as a Rankine cycle working fluid. By using an aluminium tube-plate type collector with 0·005 m tube diameter, 10 risers per metre width of collector, it becomes light and cheap. When the emissivity of the collector is 0·1 and a single cover is used, the maximum efficiency condition is attained. Limited to a pressure drop of 2·5 bar in the collector, 16 collectors can be used in series and the overall efficiency can be as high as 7·8% under 1000 W/m2 insolation conditions and for an outlet temperature of 380 K. Under these conditions 5600 collectors of 1·5 m x 1·5 m size will be required to produce 1000 kW of electricity.
 
Article
The objective of this paper is to analyze the most up-to-date data available on total greenhouse-gas emissions of a LNG fuel supply chain and life-cycle of city gas 13A1 based on surveys of the LNG projects delivering to Japan, which should provide useful basic-data for conducting life-cycle analyses of other product systems as well as future alternative energy systems, because of highly reliable data qualified in terms of its source and representativeness. In addition, the life-cycle greenhouse-gas emissions of LNG and city-gas 13A in 2010 were also predicted, taking into account not only the improvement of technologies, but also the change of composition of LNG projects. As a result of this analysis, the total amount of greenhouse-gas emissions of the whole city-gas 13A chain at present was calculated to be 61.91Â g-CO2/MJ, and the life-cycle greenhouse-gas emissions of LNG and city-gas 13A in 2010 could be expected to decrease by about 1.1% of the current emissions.
 
Article
To determine effective surface self-diffusion coefficients of CO2 within type 13X zeolite particles, at various temperatures (25-70 °C), inverse analyses of observed CO2-uptake curves were successfully performed. The obtained effective surface self-diffusion coefficients increase with both the amount adsorbed and the temperature and ranged from 7.8 x 10-10 to 1.95 x 10-9 m2/s under the present experimental conditions.
 
Article
In each pensioner's home investigated, the living room was heated during the afternoons and evenings to between 17 and 24°C. The rate of heating in the rest of the flat was influenced by weekly income. Temperatures there were very much lower than in the living room, generally being less than 12°C in the bedroom(s) and bathroom during average winter conditions. The lowest temperatures in these rooms were 5°C and 2°C respectively. Medical research shows that such cold conditions can be harmful to health, especially of the elderly or very young. The total annual rate of fuel expenditure was largely determined by other fuel use (e.g. for providing hot water and cooking). The rate of financial expenditure on space heating the living room was dependent upon its size, the chosen comfort temperature, and the weather conditions experienced. Financial income and the location of the flat affected the rate of expenditure on heating in the rest of the flat; the number of occupants and the use of the immersion heater influenced the rate of expenditure for other uses of fuels. The majority of factors which could lead to improvements in the thermal comfort achieved within these flats, notably by up-grading the thermal insulation of the building fabric, improving the heating system, use of better hot-water controls, or increasing the financial income of the occupants, were largely outside the control of the pensioners.
 
Composition of the alternative compared with the estimated technical potential
Article
Identification of political objectives is a very important part of making feasibility studies. Very often, energy projects are evaluated against narrow energy-sector objectives, such as securing "a sufficient energy supply" and/or securing "reasonable energy prices". Established technologies using fossil fuels are chosen, while new technologies with less pollution are regarded too risky or too expensive. Meanwhile, most countries have a number of important national objectives beside the energy sector, such as "decreasing imports", "creating better employment", "development of new products for export," etc. Very often, such objectives are not directly included in feasibility studies of energy projects, even though new technologies are likely to fulfil these objectives better than many established technologies. Based upon the case of a planned new 1400 MW coal-fired power station in Prachuap Khiri Khan in Thailand, this paper performs a feasibility study, in which a power-plant project and a proposed technical alternative are assessed in relation to a wide range of specific and general official development objectives for Thailand. The current plans of implementing a coal-fired power plant at Prachuap Khiri Khan is indeed not rational and alternatives exist, which are more suitable for Thailand in terms of economic growth, employment, rural development, industrial development and environmental sustainability.
 
Article
The results of an experimental study of the excess-air-dependent heat losses, as well as gaseous emissions (NOx, SO2 and CO), on a 150 MW boiler firing Thai lignite are discussed. The NOx emissions were found to increase with the higher excess air ratios; the NOx values in the flue gas (at 6% O2) ranged from 257 to 325 ppm, whilst the excess air ratio varied from 1.06 to 1.32 at the economizer outlet. Owing to the highly-efficient operation of the flue gas desulfurization units, the SO2 emissions from the unit were maintained at a relatively low level, 50-76 ppm for the above excess-air ratios, whereas they accounted for about 3100-3300 ppm at the inlet of the FGD units. The CO emissions were determined for the extremely low excess air ratios. Two approaches for the optimization of the excess air ratio were analyzed in this study. For the first, i.e. the conventional approach, the optimization was carried out based on minimizing the total excess-air-dependent heat losses. The second, the environmentally friendly approach, proposed in this work, was aimed at minimizing the "external" costs (or the costs of damage done by the boiler emissions to the environment and humans). As shown in this paper, the lignite firing at the optimal excess air results in a lower environmental impact by the boiler unit.
 
Article
Changes in labour productivity can bring about economic growth or decline of a region. The factors that explain increases or decreases in labour productivity, if identified, can help policy makers control them so as to mitigate explosive changes in productivity and their concomitant effects on the utilisation of capital, employment, prices, welfare payments and social services. This paper attempts to identify these variables for five coal-producing regions in the US. Section 2 describes these regions, identifies the relevant variables and presents an econometric methodology of regression equations for underground and surface mines. These variables are the non-captive mines, continuous mining technologies in underground mines and medium- and large-sized power shovels and draglines in surface mines, capacity utilisation, accident rates and mining regulations. The literature on regional labour productivity is critically reviewed in Section 3 and it is concluded that none of the five available studies help in comparing inter-regional productivity of labour. Section 4 presents empirical results of equations estimated for underground and surface mines and concludes that the selected variables explained variation in labour productivity significantly. In particular, the results revealed that the regional variations in productivity were explained by technological changes, mine ownership and regulatory laws passed by the Federal and the State governments.
 
Article
This paper analyses technological change in coal mines in five regions--the Northern and Southern Appalachians, the Rocky Mountains, the Interior and Gulf and Northern Great Plains. Such an analysis can help identify the regions that are growth centres of the future and those that are the declining centres, so that an orderly transfer of manpower and resources from the latter to the former can be brought about efficiently and expeditiously. Section 2 deals with changes in production profiles, over time, of the regions by dividing coal mines into underground and surface mines. It concludes that the Appalachian regions are the declining regions with lower labour productivity and that the Northern Great Plains, with its increasing labour productivity, is the expanding region. Technological changes (TC) in underground mines consist of replacement of conventional mining machines by the continuous miners and the replacement of the latter by the long-wall machines. The TC in the surface mines is the substitution of intermediate- and large-sized power shovels and draglines (PS and Ds) for their smaller size counterparts. Section 3 presents a methodology of S-shaped growth curves. Section 4 reports empirical results for growth rates of adoption of the newer techniques across regions. These results reveal that the Northern Great Plains region is not absorbing the manpower and resources released by the Appalachian regions so that there are shortages in the former in the face of unemployment in the latter. There is, therefore, an opportunity for the declining Appalachian regions to inform their surplus manpower and resources about the growth centre in the north and prepare them for relocation, retraining and readjustment to the changes.
 
Article
This paper presents estimates of what a monopoly would set natural gas prices at in the inter- and intra-state markets of the United States over the period 1960-1966. The predictions are accurate but not perfect. This paper cannot conclusively prove that price setting in these markets was done in this manner, however, due to lack of assumptions on the supply side. The estimates are close enough to be interesting though, and a model of the supply side should be developed.
 
Article
This paper examines the sources of changes in energy use of the Brazilian economy of industries and households from 1970 to 1996, using structural decomposition analysis based on the logarithmic mean divisia index technique. Energy use can be decomposed into eight factors that explain changes in overall energy use over the entire time period, and within five sub-periods. The growth of energy use between 1970 and 1996 was mainly influenced by changes in affluence, population and intersectoral dependencies, while changes in direct energy intensity and per capita residential energy use had a retarding impact on energy use. The novel contributions of the paper are the alignment of a previously disparate data set, the use of supply-use tables for SDA, and the application of such an SDA to a developing country. Both contributions involve solving a range of methodological issues pertaining to handling of large data sets.
 
Article
This paper deals with the causal relationship analysis between Gross Domestic Product, Energy Intensity and CO2 emissions in Greece from 1977 to 2007, by means of Johansen cointegration tests and Granger-causality tests based on a multivariate Vector Error Correction Modeling. Results indicate that there is a set of uni-directional and bi-directional causalities among the selected time series. We performed a model Variance Decomposition Analysis using Choleski technique and we provided a comparison with other studies. The findings of the study have significant policy implications for countries like Greece as the decoupling of CO2 emissions and economic growth seems quite unlikely.
 
Article
The current automobile fuel economy standards were established in June 1977. Several studies completed since then recommended that the Department of Transportation (DOT) modify the current schedule. However, all of the studies were completed before the 1979 gasoline shortage. This paper compares the studies performed to assess alternative schedules and identifies major differences. Major differences among the studies include the definition of[`]economic practicability', cost estimates, estimates of automobile sales losses, and the impact of EPA test procedures. The results of the comparison, along with an analysis of the mix of new cars sold and used car prices since the gasoline shortage, are used to determine if the current schedule can be achieved. Observations regarding improvements to the fuel economy programme for establishing post-1985 standards are also presented.
 
Article
The object of this paper is to analyse economic efficiency and equity aspects of the auto-gasoline mileage regulations for 1981-1984. The paper uses data available from the US Department of Transportation to estimate both the direct benefits of gasoline and maintenance cost savings and the cost of compliance by the manufacturers. The direct benefit/cost ratios exceed unity and it is concluded that the regulations are cost-effective. The equity aspects are analysed by grouping families according to income groups in the Consumer Expenditure Survey data of the US Bureau of Labor Statistics. The analysis shows that lower income groups owning fewer cars derive fewer benefits, relative to upper income groups, from fuel economy regulations. Income compensating measures such as [`]fuel stamps' are suggested as a way of mitigating this inequity.
 
Article
Forests in Southeast Asia are important sources of timber and other forest products, of local energy for cooking and heading, and potentially as sources of bioenergy. Many of these forests have experienced deforestation and forest degradation over the last few decades. The potential flow of woody biomass for bioenergy from forests is uncertain and needs to be assessed before policy intervention can be successfully implemented in the context of international negotiations on climate change. Using current data, we developed a forest land use model and projected changes in area of natural forests and forest plantations from 1990 to 2020. We also developed biomass change and harvest models to estimate woody biomass availability in the forests under the current management regime. Due to deforestation and logging (including illegal logging), projected annual woody biomass production in natural forests declined from 815.9 million tons (16.3 EJ) in 1990 to 359.3 million tons (7.2 EJ) in 2020. Woody biomass production in forest plantations was estimated at 16.2 million tons yr−1 (0.3 EJ), but was strongly affected by cutting rotation length. Average annual woody biomass production in all forests in Southeast Asia between 1990 and 2020 was estimated at 563.4 million tons (11.3 EJ) yr−1 declining about 1.5% yr−1. Without incentives to reduce deforestation and forest degradation, and to promote forest rehabilitation and plantations, woody biomass as well as wood production and carbon stocks will continue to decline, putting sustainable development in the region at risk as the majority of the population depend mostly on forest ecosystem services for daily survival.
 
Article
The present work deals with the creation, on the basis of experimental data, of the regulation maps for the 1Â MW cogenerative internal combustion engine (ICE) installed at the Engineering Faculty of Perugia University. The regulation logic mapping is necessary for the development of a thermodynamic model of the engine behaviour to simulate the effects of possible malfunctions occurrence, such as deterioration or fouling not directly experienced on the engine. Such a work is carried out as a part of a more general research activity concerning the development of a diagnosis system for the cogenerative plant. Therefore, a first phase of the present work relates to the experimental data gathering campaign and the consequent data analysis to individuate the characteristic parameters of regulation. In the second phase, instead, a neural simulator of the control logic was developed on the basis of the experimental data for the engine operation at full load (initially considered at 980Â kW) and during transitory. Consequently, through such a simulator the regulation maps of the engine were determined considering the variation range of all the characteristic parameters. Finally, a more accurate analysis of the experimental data relative to the dependence of the produced electric power at regimen on the fuel valve position, encouraged the authors to develop a further neural simulator able to reproduce the regulation commands for different values of the target power set for the regimen operation. Consequently, also the regulation mapping was revised obtaining a synthetic representation of the regulation logic useful for the implementation in the thermodynamic model of the engine dynamic behaviour.
 
Article
The definition of an efficient optimization methodology for internal combustion engine design using 1D fluid dynamic simulation models is presented. This work aims at discussing the fundamental numerical and fluid dynamic aspects which can lead to the definition of a best practice technique, depending on the complexity of the problem to be dealt with, on the number of design parameters, objective variables and constrains. For these reasons, both single-and multi-objective problems will be addressed, where the former are still of relevant interest (i.e. optimization of engine performances), while the latter have a much wider range of applications and are often characterized by conflicting objectives. The Mesh Adaptive Direct Search (MADS) was chosen among the class of direct search methods and compared with the Genetic Algorithms to solve single-objective problems, and similarly two different algorithms were chosen and compared to solve multi-objective problems: the [epsilon]-constraint method and the NSGA-II (Non-Dominated Sorting Genetic Algorithm) A single cylinder spark ignition engine, used in a motorbike application, was chosen as test case, to allow reduced computational times, without any loss of generality of the results. The analysis evaluate the convergence and efficiency of each methodology for the different problems which are solved. The achieved goal is not the definition of an ever valid mathematical strategy, but here focus is given on the parallel application of a detailed fluid dynamic analysis and automated optimization techniques to suggest a best practice technique to be employed depending on the characteristic of the optimization problem to be solved.
 
Article
This paper contributes to the development of a thermo-dynamic model of the 1 MW cogenerative internal combustion engine (I.C.E.), including also an artificial neural network simulator of the electronic control module. Such a study is part of a more wide research activity, concerning the development of a diagnosis and monitoring system specifically for power plants. In particular, the engine model was realized to simulate the engine functioning also in the case of malfunctions and failures occurrence, taking in consideration the compensation effect operated by the regulation system.The complete model was tested in reference to several experimental conditions, in particular in a first phase relative to different values of the target electrical power and, subsequently, concerning the case of compressor fouling. Therefore it was validated both the thermo-dynamic model and the regulator operation in reference to the experimental data.
 
Article
The two-stage heat transformer (TSHT) is an advanced heat–transformer which can widen the operating range compared to that which can be achieved with a single-stage heat–transformer (SSHT). This paper analyzes three kinds of two-stage heat transformers and puts forward the two-stage heat–transformer with H2O/LiBr for the first stage and 2,2,2-trifluoroethanol (TFE)/N-methy1-2-pyrrolidone (NMP) for the second stage. The results show that it can reach the same high delivered temperature as the two-stage heat–transformer with only TFE/NMP as working–fluid combinations and can achieve a higher system performance than the two-stage heat transformer with TFE/NMP.
 
Article
This paper presents rigorous experimental outdoor performance of a 2.32Â kWP stand-alone photovoltaic (SAPV) system in New Delhi (India) for four weather types in each month such as clear, hazy, partially cloudy/foggy and fully cloudy/foggy weather conditions respectively. The daily power generated from the existing SAPV system was experimentally found in the range of 4-6Â kWÂ h/day depending on the prevailing sky conditions. The number of days and daily power generated corresponding to four weather types in each month were used to determine monthly and subsequently annual power generation from the existing SAPV system. There are three daily load profiles with and without earth to air heat exchanger suitable for three seasons like summer (3.75-6.15Â kWÂ h/day), winter (2.79-5.19Â kWÂ h/day) and rainy (3.75Â kWÂ h/day). The hourly efficiency of the SAPV system components are determined and presented in this paper. The life cycle cost (LCC) analysis for the existing typical SAPV system is carried out to determine unit cost of electricity. The effect of annual degradation rate of PV system efficiency is also presented in this paper. The energy production factor (EPF) and the energy payback time (EPBT) of the SAPV system was also determined and presented in this paper.
 
Article
We measured various operational parameters of a 200-MWe, wall-fired, lignite utility boiler under different loads. The parameters measured were gas temperature, gas species concentration, char burnout, component release rates (C, H and N), furnace temperature, heat flux, and boiler efficiency. Cold air experiments of a single burner were conducted in the laboratory. A double swirl flow pulverized-coal burner has two ring recirculation zones that start in the secondary air region of the burner. With increasing secondary air flow, the air flow axial velocity increases, the maximum values for the radial velocity, tangential velocity, and turbulence intensity all increase, and there are slight increases in the air flow swirl intensity and the recirculation zone size. With increasing load gas, the temperature and CO concentration in the central region of burner decrease, while O2 concentration, NOx concentration, char burnout, and component release rates of C, H, and N increase. Pulverized-coal ignites farther into the burner, in the secondary air region. Gas temperature, O2 concentration, NOx concentration, char burnout and component release rates of C, H, and N all increase. Furthermore, CO concentration varies slightly and pulverized-coal ignites closer. In the side wall region, gas temperature, O2 concentration, and NOx concentration all increase, but CO concentration varies only slightly. In the bottom row burner region the furnace temperature and heat flux increase appreciably, but the increase become more obvious in the middle and top row burner regions and in the burnout region. Compared with a 120-MWe load, the mean NOx emission at the air preheater exits for 190-MWe load increases from 589.5 mg/m3 (O2 = 6%) to 794.6 mg/m3 (O2 = 6%), and the boiler efficiency increases from 90.73% to 92.45%.
 
Article
An analysis of the pattern of energy use in 44 sub-sectors of manufacturing industry in the UK is presented. It draws on detailed information from published statistics. Account is taken of trends in structural change and likely uptake of energy efficiency measures to examine the prospects for improved energy efficiency up to the year 2000. It is estimated that the uptake of energy saving measures will reduce total energy consumption by 2l 25%, depending on the level of industrial output.
 
Article
The homogeneous charge compression ignition is an alternative combustion technology that can reduce automobile pollution, provided that the exhaust emission can be controlled. A parametric study can be useful in order to gain more understanding in the emission reduction possibilities via this new combustion technology. For this purpose, the inlet temperature, the equivalence ratio and the compression ratio are changed, respectively, from 30 to 70 °C, 0.28 to 0.41 and 6 to 14. Also the diluting, thermal and chemical effects of exhaust gas recirculation were studied. The emission of CO, CO2, O2 and hydrocarbons has been measured using primary reference fuels. It appears that an increase in the inlet temperature, the EGR temperature, the equivalence ratio and the compression ratio results into a decrease of the emissions of CO and the hydrocarbons of up to 75%. The emission of CO2 increased, however, by 50%. The chemical parameters showed more complicated effects, resulting into a decrease or increase of the emissions, depending on whether the overall reactivity increased or not. If the reactivity increased, generally, the emissions of CO and hydrocarbons increased, while that of CO2 increased. The increase of CO2 emissions could be compensated by altering the compression ratio and the EGR parameters, making it possible to control the emission of the HCCI engine.
 
Article
The paper studied by Subbaraj et al. (2009) considers the feasibility of using self adaptive real-coded genetic algorithm for enhancement of combined heat and power economic dispatch. The paper includes some problems about the considered feasible operating region. In this discussion, the controversial point of the paper are given.
 
Article
Cogeneration is proved to be one of the promising energy management techniques, which offers an efficient method of producing electricity and useful thermal energy from a common source. In the present study various cogeneration options for a plywood industry in south India with power export is analyzed. It is found that the industry has a good potential for cogeneration. Three schemes such as steam turbine gas turbine and combined cycle are evaluated on the basis of Annualized Life Cycle Cost (ALCC). The steam turbine based cogeneration is found to be the best option as it has the least ALCC. The comparison was based on lean gas as fuel but the industry can save the fuel cost by utilizing the waste wood available which enhances the scope and economic feasibility of cogeneration. It is found that the proposed scheme can provide a tremendous saving in the annual operating cost compared to the existing facility with a payback period of 2.6 years.
 
Article
Tidal energy has the potential to play a valuable part in a sustainable energy future. It is an extremely predictable energy source, depending only on the gravitational pull of the moon and the sun and the centrifugal forces created by the rotation of the earth-moon system. Tidal energy has been exploited on a significant scale since the construction of the La Rance tidal barrage in France in 1967. A tidal barrage utilises the potential energy of the tide and has proven to be very successful, despite opposition from environmental groups. Kinetic energy can also be harnessed from tidal currents to generate electricity and involves the use of a tidal current turbine. This is the more desired method of capturing the energy in the tides. However, tidal current turbine technology is currently not economically viable on a large scale, as it is still in an early stage of development. This paper provides an up-to-date review of the status of tidal energy technology and identifies some of the key barriers challenging the development of tidal energy. The future development of tidal current devices and tidal barrage systems is discussed as well as examining the importance of a supportive policy to assist development.
 
Article
A novel technique for forecasting the supply and extraction life-cycle of depleting fossil-fuel resources has been applied to crude-oil and natural-gas productions in the unified Germany. The supply side utilises a [`]skewed-normal production-profile' model, that yields a better representation than earlier approaches. A simple model for extrapolating crude-oil and natural-gas demands for Unified Germany has also been devised and based on the so-called [`]modified logit function'. The projected crude-oil and natural-gas balances for the period up to ad 2010 indicate the increasing disparities between both the indigenous crude-oil and natural-gas productions and the future consumption requirements for Germany. The magnitudes of these forecasts depend on current estimates of the remaining oil and gas reserves. Therefore it will be necessary to revise periodically the present projections as more reliable reserve-estimates become available.
 
Article
A novel technique for forecasting the supply and extraction life-cycle of a depleting fossil fuel resource has been developed. The supply side utilises a [`]skewed-normal production-profile' model that yields a better representation than earlier approaches. A simple model for extrapolating crude oil and natural gas demands has also been devised, based on the so called [`]modified logit function'. The predicted crude oil and natural gas balances for the period up to 2010 indicate the disparity between indigenous production and future consumption for France. These forecasts depend on current estimates of remaining oil and gas reserves. It will consequently be necessary to revise periodically the present projections as more reliable reserve estimates become available.
 
Article
A novel approach to the modelling of the extraction life-cycle of depleting fossil fuel resources has been applied to the case of oil and natural gas production within the UK Continental Shelf. This utilises skewed normal production profiles that yield a better representation than do earlier approaches. Simple methods for extrapolating oil and gas demand in the UK have also been devised. The projected oil and gas balances for the period up to 2010 indicate when oil production will cease to meet indigenous consumption, and the increasing need to import natural gas supplies. These results depend quite heavily on estimates of remaining oil and gas reserves. It will consequently be necessary to revise periodically the present projections as more reliable reserve estimates become available.
 
Article
The Polish [`]Development Strategy for Renewables', approved by the Council of Ministers in 2000 and by Parliament in 2001, called for a 7.5% contribution of renewable energy to total primary-energy production in 2010, and 14% in 2020 as development targets for renewables. The purpose of this project was to investigate further what this Strategy meant in terms of the types and amounts of renewable-energy (RE) systems that would need to be installed and the support mechanisms that would need to be put in place to enable this to happen. Development scenarios for RE to 2020 were elaborated and their financial, environmental and social implications were calculated with the Strategic Assessment Framework for the Implementation of Rational Energy (SAFIRE) computer model, devised by Energy for Sustainable Development Ltd (ESD, UK).
 
Article
When discussing how society can decrease greenhouse gas emissions, the transport sector is often seen as posing one of the most difficult problems. In addition, the transport sector faces problems related to security of supply. The aim of this paper is to present possible strategies for a road transport system based on renewable energy sources and to illustrate how such a system could be designed to avoid dependency on imports, using Sweden as an example. The demand-side strategies considered include measures for decreasing the demand for transport, as well as various technical and non-technical means of improving vehicle fuel economy. On the supply side, biofuels and synthetic fuels produced from renewable electricity are discussed. Calculations are performed to ascertain the possible impact of these measures on the future Swedish road transport sector. The results underline the importance of powerful demand-side measures and show that although biofuels can certainly contribute significantly to an import-independent road transport sector, they are far from enough even in a biomass-rich country like Sweden. Instead, according to this study, fuels based on renewable electricity will have to cover more than half of the road transport sector’s energy demand.
 
Article
In 2008, South Africa experienced a severe electricity crisis. Domestic and industrial electricity users had to suffer from black outs all over the country. It is argued that partially the reason was the lack of research on energy, locally. However, Eskom argues that the lack of capacity can only be solved by building new power plants. The objective of this study is to specify the variables that explain the electricity demand in South Africa and to forecast electricity demand by creating a model using the Engle-Granger methodology for co-integration and Error Correction models. By producing reliable results, this study will make a significant contribution that will improve the status quo of energy research in South Africa. The findings indicate that there is a long run relationship between electricity consumption and price as well as economic growth/income. The last few years in South Africa, price elasticity was rarely taken into account because of the low and decreasing prices in the past. The short-run dynamics of the system are affected by population growth, too After the energy crisis, Eskom, the national electricity supplier, is in search for substantial funding in order to build new power plants that will help with the envisaged lack of capacity that the company experienced. By using two scenarios for the future of growth, this study shows that the electricity demand will drop substantially due to the price policies agreed - until now - by Eskom and the National Energy Regulator South Africa (NERSA) that will affect the demand for some years.
 
Article
Four major themes will dominate United States energy-security in the 21st century. One is the need to diversify the fuel mix (i.e., oil, natural gas, nuclear power, hydro-electricity and other renewable and alternative energy resources). Another is the need to diversify the geographic origin of energy. A third theme is conservation and energy efficiency. And the final theme is devising new ways of managing growing dependence on oil imports rather than aiming at achieving “energy independence”. This paper will examine the new frontiers of the United States’ energy security in the 21st century. It will argue that fossil fuels will continue to dominate US energy needs well into the 21st century and that the Gulf region will maintain its strategic importance for US energy security for the foreseeable future. The paper will conclude that US energy-security could be better served by devising ways of managing dependence on oil imports rather than engaging in meaningless debate over energy independence.
 
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Energy experts project that global oil supplies will only meet demand until global oil production has peaked sometime between 2013 and 2020. Declining oil production after peak production will cause a global energy gap to develop, which will have to be bridged by unconventional and renewable energy sources. Nuclear, solar and hydrogen are destined to become major energy sources during the 21st century, but only if their enabling technologies improve significantly to ensure affordability and convenience of use. This paper will argue that global oil production will probably peak between 2004 and 2005, causing a serious energy gap to develop sometime between 2008 and 2010 rather than 2013-2020 as the energy experts projected. It will also argue that a transition from fossil fuels to renewable energy sources is inevitable. The paper will conclude, however, that fossil fuels with a growing contribution from nuclear energy, will still be supplying the major part of the global energy needs for most, perhaps all, of the 21st century.
 
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Les modeles theoriques montrent que de substantielles economies peuvent etre realisees en densifiant les cites plutot qu'en les etirant. La structure spatiale de la maille urbaine est l'element cle. Les villes organiques qui ont pousse pendant de longues periodes semblent optimiser certains aspects fondamentaux de l'utilisation de l'espace et de la facilite de mouvement. Les civilisations denses paraissent devenir une possibilite de plus en plus attractive, ouvrant la voie vers une economie du mouvement
 
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This paper discusses the theoretical differences in performance between using R-12 and R-22 resulting from changes in thermodynamic properties. It also assesses the potential for using R-22 as a replacement for R-12 by considering a case study of an R-12 reciprocating air-conditioning unit conversion to an R-22 unit.
 
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Bio-fuels are important because they replace petroleum fuels. A number of environmental and economic benefits are claimed for bio-fuels. Bio-ethanol is by far the most widely used bio-fuel for transportation worldwide. Production of bio-ethanol from biomass is one way to reduce both consumption of crude oil and environmental pollution. Using bio-ethanol blended gasoline fuel for automobiles can significantly reduce petroleum use and exhaust greenhouse gas emission. Bio-ethanol can be produced from different kinds of raw materials. These raw materials are classified into three categories of agricultural raw materials: simple sugars, starch and lignocellulose. Bio-ethanol from sugar cane, produced under the proper conditions, is essentially a clean fuel and has several clear advantages over petroleum-derived gasoline in reducing greenhouse gas emissions and improving air quality in metropolitan areas. Conversion technologies for producing bio-ethanol from cellulosic biomass resources such as forest materials, agricultural residues and urban wastes are under development and have not yet been demonstrated commercially.
 
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Sugar cane bagasse was submitted to ethanol organosolv pre-treatment using a 50 L pilot scale reactor. The influence of catalyst type (H2SO4 or NaOH), catalyst concentration (1.25–1.50% w/w on dry fiber) and process time (60–90 min) on total solid recovery and solid composition (glucan, xylan and lignin contents) was evaluated by performing a 23 full factorial experimental design. Pretreated sugar cane bagasse was further submitted to enzymatic hydrolysis using a commercial enzyme complex formed by cellulases and β-glucosidases. Glucose concentration in the hydrolysates and glucose yield referred to initial raw material (g glucose/100 g sugar cane bagasse) were used to select the best operational conditions. Concerning the enzymatic hydrolysis, the resulting glucose concentration was found to be dependent on xylan contents of the pretreated material. The modelling equations for glucose concentration and glucose yield as a function of the pre-treatment variables and the statistical analysis are also discussed in this work.
 
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Cofiring biomass with fossil fuels is emerging as a viable option for promoting the use of low quality renewable biomass fuels including energy crops. In the current work, dairy biomass (DB) is evaluated as a cofiring fuel with coal in a small scale 29 kWt boiler burner facility. Two types of coal (Texas lignite, TXL and Wyoming Powder River Basin coal, WYO) and two forms of partially composted DB fuels were investigated (low ash separated solids LA-PC-SepSol-DB and high ash soil surface HA-PC-SoilSurf-DB). Proximate and ultimate analyses performed on both coals and both DBs reveal the following: higher heating value (HHV) of 28,460–29,590 kJ/kg for dry ash free (DAF) coals and 21,450 kJ/kg for DB; nitrogen loading of 0.36 and 0.48 kg/GJ for WYO and TXL, respectively and 1.50 and 2.67 kg/GJ for the LA-PC-SepSol-DB and the HA-PC-SoilSurf-DB respectively; sulfur loading of 0.15 and 0.42 kg/GJ WYO and TXL, respectively and 0.33 and 0.43 kg/GJ for the LA-PC-SepSol-DB and the HA-PC-SoilSurf-DB respectively; ash loading from 3.10 to 8.02 kg/GJ for the coals and from 11.57 to 139 kg/GJ for the DB fuels.
 
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In order to investigate the characteristics of the reaction between ammonium sulfite, the main desulfurizing solution, and the flue-gas-contained sulfur dioxide during the process of ammonia-based WFGD (wet flue gas desulfurization) in a power plant, the gas-liquid absorption reaction between sulfur dioxide and an ammonium sulfite solution was studied in a stirred tank reactor. The experimental results indicate that the absorption of sulfur dioxide is controlled by both the gas- and liquid-films when the ammonium sulfite concentration is lower than 0.05Â mol/L, and mainly by the gas-film at higher concentrations. In the latter case, the reaction rates are found to be zero-order with respect to the concentration of ammonium sulfite. The absorption rates of sulfur dioxide increase as the concentration of sulfur dioxide in inlet gas and the temperature increase. The reaction rate is of 0.6th-order with respect to the concentration of sulfur dioxide.
 
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Full-scale experiments were performed on a 300Â MWe utility boiler retrofitted with air staging. In order to improve boiler thermal efficiency and to reduce NOx emission, the influencing factors including the overall excessive air ratio, the secondary air distribution pattern, the damper openings of CCOFA and SOFA, and pulverized coal fineness were investigated. Through comprehensive combustion adjustment, NOx emission decreased 182Â ppm (NOx reduction efficiency was 44%), and boiler heat efficiency merely decreased 0.21%. After combustion improvement, high efficiency and low NOx emission was achieved in the utility coal-fired boiler retrofitted with air staging, and the unburned carbon in ash can maintain at a desired level where the utilization of fly-ash as byproducts was not influenced.
 
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In this paper we examine the long-run relationship between gold and oil spot and futures markets. We draw on the conceptual framework that when oil price rises, it creates inflationary pressures, which instigate investments in gold as a hedge against inflation. We test for the long-run relationship between gold and oil futures prices at different maturity and unravel evidence of cointegration. This implies that: (a) investors use the gold market as a hedge against inflation and (b) the oil market can be used to predict the gold market prices and vice versa, thus these two markets are jointly inefficient, at least for the sample period considered in this study.
 
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Ambient temperature bin data are used for estimating the energy consumption for heating and cooling of buildings. This well-known method is a steady-state approach and the energy requirements are determined at various outdoor temperatures, in order to account for the effect of outside temperature on the HVAC equipment efficiency. The application of the method requires detailed bin data. In this paper, the dry-bulb temperature bin data for 38 Greek cities are determined by using a reliable estimating methodology, based on monthly-average outdoor temperatures and solar clearness index. The data are calculated from -18 °C to 42 °C with 2 °C increments in six daily 4-h shifts, and are presented in tabular form.
 
Top-cited authors
Jinyue Yan
  • Applied Energy, The International Journal published by Elsevier
Hongxing Yang
  • The Hong Kong Polytechnic University
Luisa F. Cabeza
  • Universitat de Lleida
Henrik Lund
  • Aalborg University
Rui Xiong
  • Beijing Institute of Technology