Results 1 - 10 of 127
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[en] We describe the use of the decomposition technique for comparing energy-related CO2 emission levels between countries/regions. Application studies pertaining to total and per capita CO2 emissions for three OECD regions and three world regions are presented. These studies demonstrate how the difference in annual CO2 emission level between two regions may be expressed in terms of inter-regional differences in fuel share in energy demand, aggregate energy intensity, income, and population. We also show that the recently proposed logarithmic mean Divisia decomposition approach can be conveniently applied in such comparative studies. (Author)
[en] In recent years, thermodynamics has been applied in a number of new fields leading to a greater societal impact. This paper gives a survey of these new fields and the reasons why these applications are important. In addition, it is shown that the number of fields could be even greater in the future and could lead to savings in human effort, use of land and water and of energy and natural resources. Achieving these savings is a contribution to a sustainable society
[en] In the present paper, exergy loss analysis of newly designed compact heat exchanger (CHE) was experimentally investigated. For this reason, experimental system used for experimental analysis of the newly designed CHE and brazed plate heat exchanger (BPHE) were designed and constructed. Thermodynamic analysis of newly designed CHE and BPHE were also investigated. The experimental results of the CHE and BPHE are compared. Exergy loss values are calculated for each heat exchanger type. The experimental results show that similar exergy loss values were obtained. The highest exergy loss value for newly designed CHE has been obtained as about 7.6 kW, while the least exergy loss value has been obtained as about 4.65 kW for the same heat exchanger. The results of the experiments are compared and presented graphically. - Highlights: • Exergy loss analysis of newly designed compact heat exchanger (CHE) was experimentally investigated. • Thermodynamic analysis of newly designed CHE and brazed plate heat exchanger (BPHE) were also investigated. • The experimental results of the CHE and BPHE are compared. • The highest exergy loss value for newly designed CHE has been obtained as about 7.6 kW.
[en] Expressions of the molar exergy and of the molar flow exergy of a pure chemical fuel are deduced rigorously from the basic principles of thermodynamics. It is shown that molar exergy and molar flow exergy coincide when the temperature T and the pressure p of the fuel are equal to the temperature TB and the pressure pB of the environment; a general relation between exergy and flow exergy is proved as a consequence. The deduction of the expression of the molar exergy of a chemical fuel for non-standard values of TB and pB is clarified. For hydrogen, carbon dioxide and several hydrocarbons, tables are reported to allow a simple calculation of the molar exergy of the fuel for any value of the temperature TB and the relative humidity φB of the environment, in the range 268.15 K ≤ TB ≤ 313.15 K and 0.1 ≤ φB ≤ 1, with reference to the standard atmospheric pressure. Additional tables are provided to evaluate the difference between the exergy or the flow exergy of the fuel in its given initial state and the exergy at T = TB and p = pB. In these tables, it is assumed that fuel and environment have the same temperature and that the fuel pressure varies in the range 1.01325 bar ≤ p ≤ 200 bar; the fuel may be gas or liquid.
[en] In this paper the influence of greenhouse construction on energy efficiency in winter lettuce production was estimated for four different double plastic covered greenhouses in Serbia region. Plastic coverings were introduced in this region as a mean of making the plant production more energy efficient. Additionally, as a means of lowering energy consumption, tunnel structures were proposed. In order to see whether the greenhouse structure influences energy consumption, four different double plastic covered greenhouses. Two tunnel types, 9 x 58 m and 8 x 25 m, one gutter-connected structure and multi-span plastic covered greenhouse. The gutter-connected structure was 2 x 7 m wide and 39 m long while the multi-span structure was 20 x 6.4 m wide and 42 m long. On the basis of lettuce production output and the energy input, specific energy input, energy output-input ratio and energy productivity were estimated. Results show that the lowest energy consumption was obtained for multi-span greenhouse, 9.76 MJ/m2. The highest energy consumption was obtained in tunnel, 9 x 58 m, 13.93 MJ/m2. The highest value for output-input ratio was calculated for multi-span greenhouse (0.29), followed by gutter-connected greenhouse (0.21), tunnel 9 x 58 m (0.17) and tunnel, 8 x 25 m (0.15). Results also show that energy productivity can be higher if multi-span greenhouse structures are used.
[en] Energy demand depends on outdoor temperature in a 'u' shaped fashion. Various studies have used this temperature dependence to investigate the effects of climate change on energy demand. Such studies contain implicit or explicit assumptions to describe expected socio-economic changes that may affect future energy demand. This paper critically analyzes these implicit or explicit assumptions and their possible effect on the studies' outcomes. First we analyze the interaction between the socio-economic structure and the temperature dependence pattern (TDP) of energy demand. We find that socio-economic changes may alter the TDP in various ways. Next we investigate how current studies manage these dynamics in socio-economic structure. We find that many studies systematically misrepresent the possible effect of socio-economic changes on the TDP of energy demand. Finally, we assess the consequences of these misrepresentations in an energy demand model based on temperature dependence and climate scenarios. Our model results indicate that expected socio-economic dynamics generally lead to an underestimation of future energy demand in models that misrepresent such dynamics. We conclude that future energy demand models should improve the incorporation of socio-economic dynamics. We propose dynamically modeling several key parameters and using direct meteorological data instead of degree days. (author)
[en] The impacts of societal and regulatory impediments on the cost of generating electricity from nuclear power plants are addressed in this study. Economic losses are incurred as the result of interest payments for capital and excessive incremental costs for replacement power (resulting from construction delays or from cancellation of partially or completely built reactors). The total costs for these delays or cancellations are estimated to be approximately $500 billion each for the US and non-US countries (including the Eastern Block). (author)
[en] This paper analyzes the evolution of real energy efficiency in the European Union and the attribution across countries of its percent change. Relying on a multiplicative energy intensity approach that is implemented through the Sato-Vartia Logarithmic Mean Divisia Index method, we decompose the change in aggregate energy intensity in 20 European countries for the period from 1995 to 2010. A comparative analysis of real energy intensity indices is also carried out. In addition, a new tool to monitor changes in real energy intensity in greater detail is applied. The attribution analysis of IDA (Index Decomposition Analysis) as proposed by Choi and Ang (Choi KH, Ang BW. Attribution of changes in Divisia real energy intensity index – an extension to index decomposition analysis. Energy Economics 2012;34:171–6) is used in order to assess the contribution of each individual sector to the percent change in real energy intensity. Results indicate that the European countries, particularly the former communist ones, made a remarkable effort to improve energy efficiency. Our analysis also suggests some strategies –including promotion and adaptation to more efficient techniques, innovation, improved use of technologies, R and D, and substitution for higher quality energies-, which are of particular interest to the industry sector -including construction- in ex-communist EU members, and to the industry and transport plus hotels and restaurants sectors in Western countries. - Highlights: • We apply a single and multi-period attribution analysis approach . • Technical change, improved use of tech and quality energies, keys to AEI drop. • Real energy intensity shows valuable progress in former communist European members. • The biggest attribution of percent change in real energy intensity was to Industry. • Western EU: Services and Agriculture poor contributors to real energy intensity drop
[en] It has been shown that scavenging energy from raindrop impacts has the potential as a power source for electronic devices and act as an alternative method of generating electrical power. In this paper an energy harvesting module is developed consisting of multiple piezoelectric devices which use impacts of raindrops to generate electrical power. The effect on efficiency of the module with non-rectified or rectified outputs of each device connected in parallel is investigated. Additionally, the voltage, power and energy were found for different surface angles, surface conditions and impact regions for single devices with a view to maximise module efficiency. The main findings of this work are that: a) a technique is found to identify the efficiency of the impact mechanism as the droplet interacts with the device and the efficiency of the mecheno-electric conversion mechanism due to internal losses in the device; b) values for the impact mechanism efficiency and the conversion mechanism efficiency are ascertained; and c) the optimum arrangement for a single device is determined. - Highlights: • A technique is found to identify the efficiency of the impact mechanism. • A technique is also found for the mechano-electric conversion mechanism. • Values for the impact and conversion mechanism efficiencies are ascertained. • The optimum arrangement for a single device is determined.
[en] We analyse firewood consumption along altitudinal gradient by households according to their socio-economic conditions in Garhwal Himalaya. Consumption of fuelwood was 789, 664, 518, and 544 kg/cap-yr and energy consumption for fuelwood collection was 41, 53, 52 and 80 x 103 kg/cap-yr, respectively, above 2000, for 1500-2000, 1000-1500, and 500-1000 m. Commercial fuel consumption constituted 0.6-4.5%. (author)