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Energies, Volume 7, Issue 9 (September 2014), Pages 5502-6224

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Open AccessCorrection Correction: Rees, S. and Curtis, R. National Deployment of Domestic Geothermal Heat Pump Technology: Observations on the UK Experience 1995–2013. Energies 2014, 7, 5460–5499
Energies 2014, 7(9), 6224; https://doi.org/10.3390/en7096224
Received: 27 August 2014 / Accepted: 1 September 2014 / Published: 25 September 2014
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Abstract
We have found the following error in the publishing history of this article which was recently published in Energies [1].[...] Full article
Open AccessCorrection Correction: Budea, S. Solar Air Collectors for Space Heating and Ventilation Applications—Performance and Case Studies under Romanian Climatic Conditions. Energies 2014, 7, 3781–3792
Energies 2014, 7(9), 6223; https://doi.org/10.3390/en7096223
Received: 27 August 2014 / Accepted: 15 September 2014 / Published: 25 September 2014
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Abstract
An inadvertent error was found in the pdf version of paper [1]. On page 3785, Equation (2) was not displayed well and should be read...[...] Full article
Open AccessArticle Estimating the Technical Improvement of Energy Efficiency in the Automotive Industry—Stochastic and Deterministic Frontier Benchmarking Approaches
Energies 2014, 7(9), 6196-6222; https://doi.org/10.3390/en7096196
Received: 10 July 2014 / Accepted: 15 September 2014 / Published: 25 September 2014
Cited by 9 | PDF Full-text (1462 KB) | HTML Full-text | XML Full-text
Abstract
The car manufacturing industry, one of the largest energy consuming industries, has been making a considerable effort to improve its energy intensity by implementing energy efficiency programs, in many cases supported by government research or financial programs. While many car manufacturers claim that
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The car manufacturing industry, one of the largest energy consuming industries, has been making a considerable effort to improve its energy intensity by implementing energy efficiency programs, in many cases supported by government research or financial programs. While many car manufacturers claim that they have made substantial progress in energy efficiency improvement over the past years through their energy efficiency programs, the objective measurement of energy efficiency improvement has not been studied due to the lack of suitable quantitative methods. This paper proposes stochastic and deterministic frontier benchmarking models such as the stochastic frontier analysis (SFA) model and the data envelopment analysis (DEA) model to measure the effectiveness of energy saving initiatives in terms of the technical improvement of energy efficiency for the automotive industry, particularly vehicle assembly plants. Illustrative examples of the application of the proposed models are presented and demonstrate the overall benchmarking process to determine best practice frontier lines and to measure technical improvement based on the magnitude of frontier line shifts over time. Log likelihood ratio and Spearman rank-order correlation coefficient tests are conducted to determine the significance of the SFA model and its consistency with the DEA model. ENERGY STAR® EPI (Energy Performance Index) are also calculated. Full article
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Open AccessCommunication Optimization of Alkaline Flocculation for Harvesting of Scenedesmus quadricauda #507 and Chaetoceros muelleri #862
Energies 2014, 7(9), 6186-6195; https://doi.org/10.3390/en7096186
Received: 11 June 2014 / Revised: 13 August 2014 / Accepted: 17 September 2014 / Published: 24 September 2014
Cited by 7 | PDF Full-text (467 KB) | HTML Full-text | XML Full-text
Abstract
A response surface methodology (RSM) was used to evaluate the effects of pH and microalgal biomass concentration (BC) on alkaline flocculating activity for harvesting one freshwater green algae Scenedesmus quadricauda #507 and one marine diatom Chaetoceros muelleri #862. The pH value and BC
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A response surface methodology (RSM) was used to evaluate the effects of pH and microalgal biomass concentration (BC) on alkaline flocculating activity for harvesting one freshwater green algae Scenedesmus quadricauda #507 and one marine diatom Chaetoceros muelleri #862. The pH value and BC were in range of 9.0–12.0 and 0.20–2.30 g/L, respectively. Very high regression coefficient between the variables and the response indicates excellent evaluation of experimental data by second-order regressions. Optimum conditions for flocculating activity were estimated as follows: (i) pH 11.6, BC 0.54 g/L for strain #507 and (ii) pH 11.5, BC 0.42 g/L for strain #862. The maximum flocculating activity was around 94.7% and 100%, respectively. Furthermore, the addition of synthetic ocean water (SOW) to the freshwater #507 culture can increase the flocculating activity from 82.13%–88.79% in low algae concentration (0.52 g/L) and 82.92%–95.60% in high concentration (2.66 g/L). Full article
(This article belongs to the Special Issue Algae Based Technologies)
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Open AccessArticle Experimental Investigation of the Performance of a Hermetic Screw-Expander Organic Rankine Cycle
Energies 2014, 7(9), 6172-6185; https://doi.org/10.3390/en7096172
Received: 6 June 2014 / Revised: 15 August 2014 / Accepted: 22 September 2014 / Published: 23 September 2014
Cited by 21 | PDF Full-text (1514 KB) | HTML Full-text | XML Full-text
Abstract
In this study, the authors experimentally investigate the performance of the organic Rankine cycle (ORC) and screw expander under the influence of supply pressure and pressure ratio over the expander. Three tests were performed with expander pressure ratios of 2.4–3.5, 3.0–4.6, and 3.3–6.1,
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In this study, the authors experimentally investigate the performance of the organic Rankine cycle (ORC) and screw expander under the influence of supply pressure and pressure ratio over the expander. Three tests were performed with expander pressure ratios of 2.4–3.5, 3.0–4.6, and 3.3–6.1, which cover the over-expansion and under-expansion operating modes. The test results show a maximum expander isentropic efficiency of 72.4% and a relative cycle efficiency of 10.5% at an evaporation temperature of 101 °C and condensation temperature of 45 °C. At a given pressure ratio over the expander, a higher supply pressure to the expander causes a higher expander isentropic efficiency and higher cycle efficiency in the over-expansion mode. However, in the under-expansion mode, the higher supply pressure results in a lower expander isentropic efficiency and adversely affects the cycle efficiency. The results also show that under the condition of operation at a given pressure ratio, a higher supply pressure yields a larger power output owing to the increased mass flow rate at the higher supply pressure. The study results demonstrate that a screw-expander ORC can be operated with a wide range of heat sources and heat sinks with satisfactory cycle efficiency. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
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Open AccessArticle Business Models in the Smart Grid: Challenges, Opportunities and Proposals for Prosumer Profitability
Energies 2014, 7(9), 6142-6171; https://doi.org/10.3390/en7096142
Received: 5 July 2014 / Revised: 7 September 2014 / Accepted: 9 September 2014 / Published: 23 September 2014
Cited by 26 | PDF Full-text (980 KB) | HTML Full-text | XML Full-text
Abstract
Considering that non-renewable energy resources are dwindling, the smart grid turns out to be one of the most promising and compelling systems for the future of energy. Not only does it combine efficient energy consumption with avant-garde technologies related to renewable energies, but
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Considering that non-renewable energy resources are dwindling, the smart grid turns out to be one of the most promising and compelling systems for the future of energy. Not only does it combine efficient energy consumption with avant-garde technologies related to renewable energies, but it is also capable of providing several beneficial utilities, such as power monitoring and data provision. When smart grid end users turn into prosumers, they become arguably the most important value creators within the smart grid and a decisive agent of change in terms of electricity usage. There is a plethora of research and development areas related to the smart grid that can be exploited for new business opportunities, thus spawning another branch of the so-called “green economy” focused on turning smart energy usage into a profitable business. This paper deals with emerging business models for smart grid prosumers, their strengths and weaknesses and puts forward new prosumer-oriented business models, along with their value propositions. Full article
(This article belongs to the Special Issue Energy Transitions and Economic Change)
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Open AccessArticle Methane Flux and Authigenic Carbonate in Shallow Sediments Overlying Methane Hydrate Bearing Strata in Alaminos Canyon, Gulf of Mexico
Energies 2014, 7(9), 6118-6141; https://doi.org/10.3390/en7096118
Received: 11 August 2014 / Revised: 4 September 2014 / Accepted: 9 September 2014 / Published: 23 September 2014
Cited by 6 | PDF Full-text (4789 KB) | HTML Full-text | XML Full-text
Abstract
In June 2007 sediment cores were collected in Alaminos Canyon, Gulf of Mexico across a series of seismic data profiles indicating rapid transitions between the presence of methane hydrates and vertical gas flux. Vertical profiles of dissolved sulfate, chloride, calcium, magnesium, and dissolved
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In June 2007 sediment cores were collected in Alaminos Canyon, Gulf of Mexico across a series of seismic data profiles indicating rapid transitions between the presence of methane hydrates and vertical gas flux. Vertical profiles of dissolved sulfate, chloride, calcium, magnesium, and dissolved inorganic carbon (DIC) concentrations in porewaters, headspace methane, and solid phase carbonate concentrations were measured at each core location to investigate the cycling of methane-derived carbon in shallow sediments overlying the hydrate bearing strata. When integrated with stable carbon isotope ratios of DIC, geochemical results suggest a significant fraction of the methane flux at this site is cycled into the inorganic carbon pool. The incorporation of methane-derived carbon into dissolved and solid inorganic carbon phases represents a significant sink in local carbon cycling and plays a role in regulating the flux of methane to the overlying water column at Alaminos Canyon. Targeted, high-resolution geochemical characterization of the biogeochemical cycling of methane-derived carbon in shallow sediments overlying hydrate bearing strata like those in Alaminos Canyon is critical to quantifying methane flux and estimating methane hydrate distributions in gas hydrate bearing marine sediments. Full article
(This article belongs to the Special Issue Coastal Ocean Natural Gas Hydrate 2014)
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Open AccessArticle Optimization of Design Pressure Ratio of Positive Displacement Expander for Vehicle Engine Waste Heat Recovery
Energies 2014, 7(9), 6105-6117; https://doi.org/10.3390/en7096105
Received: 31 July 2014 / Revised: 15 September 2014 / Accepted: 16 September 2014 / Published: 22 September 2014
Cited by 8 | PDF Full-text (1012 KB) | HTML Full-text | XML Full-text
Abstract
This study investigated the effect of the built-in volume ratio of an expander on the performance of a dual-loop Rankine cycle system for the engine waste heat recovery of a vehicle. Varying vehicle operating conditions can cause a positive displacement expander to operate
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This study investigated the effect of the built-in volume ratio of an expander on the performance of a dual-loop Rankine cycle system for the engine waste heat recovery of a vehicle. Varying vehicle operating conditions can cause a positive displacement expander to operate in both under- and over-expansion states. Therefore, analysis of the off-design performance of the expander is very important. Furthermore, the volume and weight of the expander must be considered in its optimization along with the efficiency. A simple modeling of the off-design operation of the expander showed that a built-in volume ratio that causes under-expansion rather than over-expansion at the target condition is more desirable. Full article
(This article belongs to the Special Issue Organic Rankine Cycle (ORC))
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Open AccessArticle Performance Characterization and Auto-Ignition Performance of a Rapid Compression Machine
Energies 2014, 7(9), 6083-6104; https://doi.org/10.3390/en7096083
Received: 15 August 2014 / Revised: 7 September 2014 / Accepted: 15 September 2014 / Published: 22 September 2014
Cited by 9 | PDF Full-text (3107 KB) | HTML Full-text | XML Full-text
Abstract
A rapid compression machine (RCM) test bench is developed in this study. The performance characterization and auto-ignition performance tests are conducted at an initial temperature of 293 K, a compression ratio of 9.5 to 16.5, a compressed temperature of 650 K to 850
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A rapid compression machine (RCM) test bench is developed in this study. The performance characterization and auto-ignition performance tests are conducted at an initial temperature of 293 K, a compression ratio of 9.5 to 16.5, a compressed temperature of 650 K to 850 K, a driving gas pressure range of 0.25 MPa to 0.7 MPa, an initial pressure of 0.04 MPa to 0.09 MPa, and a nitrogen dilution ratio of 35% to 65%. A new type of hydraulic piston is used to address the problem in which the hydraulic buffer adversely affects the rapid compression process. Auto-ignition performance tests of the RCM are then performed using a DME–O2–N2 mixture. The two-stage ignition delay and negative temperature coefficient (NTC) behavior of the mixture are observed. The effects of driving gas pressure, compression ratio, initial pressure, and nitrogen dilution ratio on the two-stage ignition delay are investigated. Results show that both the first-stage and overall ignition delays tend to increase with increasing driving gas pressure. The driving gas pressure within a certain range does not significantly influence the compressed pressure. With increasing compression ratio, the first-stage ignition delay is shortened, whereas the second-stage ignition delay is extended. With increasing initial pressure, both the first-stage and second-stage ignition delays are shortened. The second-stage ignition delay is shortened to a greater extent than that of the first-stage. With increasing nitrogen dilution ratio, the first-stage ignition delay is shortened, whereas the second-stage is extended. Thus, overall ignition delay presents different trends under various compression ratios and compressed pressure conditions. Full article
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Open AccessArticle False Shades of Green: The Case of Brazilian Amazonian Hydropower
Energies 2014, 7(9), 6063-6082; https://doi.org/10.3390/en7096063
Received: 30 June 2014 / Revised: 15 August 2014 / Accepted: 1 September 2014 / Published: 16 September 2014
Cited by 21 | PDF Full-text (563 KB) | HTML Full-text | XML Full-text
Abstract
The Federal Government of Brazil has ambitious plans to build a system of 58 additional hydroelectric dams in the Brazilian Amazon, with Hundreds of additional dams planned for other countries in the watershed. Although hydropower is often billed as clean energy, we argue
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The Federal Government of Brazil has ambitious plans to build a system of 58 additional hydroelectric dams in the Brazilian Amazon, with Hundreds of additional dams planned for other countries in the watershed. Although hydropower is often billed as clean energy, we argue that the environmental impacts of this project are likely to be large, and will result in substantial loss of biodiversity, as well as changes in the flows of ecological services. Moreover, the projects will generate significant greenhouse gas emissions from deforestation and decay of organic matter in the reservoirs. These emissions are equivalent to the five years of emissions that would be generated by gas powered plants of equivalent capacity. In addition, we examine the economic benefits of the hydropower in comparison to new alternatives, such as photovoltaic energy and wind power. We find that current costs of hydropower exceed alternatives, and the costs of costs of these alternatives are likely to fall substantially below those of hydropower, while the environmental damages from the dams will be extensive and irreversible. Full article
(This article belongs to the Special Issue Energy Transitions and Economic Change)
Open AccessArticle Multiagent-Based Distributed Load Shedding for Islanded Microgrids
Energies 2014, 7(9), 6050-6062; https://doi.org/10.3390/en7096050
Received: 22 July 2014 / Revised: 5 September 2014 / Accepted: 9 September 2014 / Published: 15 September 2014
Cited by 5 | PDF Full-text (718 KB) | HTML Full-text | XML Full-text
Abstract
This paper addresses a multiagent-based distributed load shedding scheme to restore frequency for the microgrids during islanded operation. The objective of the proposed scheme is to realize a distributed load shedding considering its associated cost and the capacity of the flexible loads. There
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This paper addresses a multiagent-based distributed load shedding scheme to restore frequency for the microgrids during islanded operation. The objective of the proposed scheme is to realize a distributed load shedding considering its associated cost and the capacity of the flexible loads. There are two advantages of the proposed scheme: (1) it is a distributed scheme using average-consensus theorem, which can discover the global information when only communications between immediate neighboring agents are used, moreover it can meet the requirements of plug-and-play operations more easily than a centralized scheme; (2) it is a new adaptive load shedding through the comprehensive weights which take into accounts the cost of load shedding and the capacity of flexible loads, these comprehensive weights are evaluated locally by making use of the adaptability and intelligence characteristics of agents. Simulation results in power systems computer aided design (PSCAD) illustrate the validity and adaptability of the proposed load shedding scheme. Full article
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Open AccessArticle Induced Voltages Ratio-Based Algorithm for Fault Detection, and Faulted Phase and Winding Identification of a Three-Winding Power Transformer
Energies 2014, 7(9), 6031-6049; https://doi.org/10.3390/en7096031
Received: 6 August 2014 / Revised: 5 September 2014 / Accepted: 9 September 2014 / Published: 12 September 2014
Cited by 13 | PDF Full-text (396 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes an algorithm for fault detection, faulted phase and winding identification of a three-winding power transformer based on the induced voltages in the electrical power system. The ratio of the induced voltages of the primary-secondary, primary-tertiary and secondary-tertiary windings is the
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This paper proposes an algorithm for fault detection, faulted phase and winding identification of a three-winding power transformer based on the induced voltages in the electrical power system. The ratio of the induced voltages of the primary-secondary, primary-tertiary and secondary-tertiary windings is the same as the corresponding turns ratio during normal operating conditions, magnetic inrush, and over-excitation. It differs from the turns ratio during an internal fault. For a single phase and a three-phase power transformer with wye-connected windings, the induced voltages of each pair of windings are estimated. For a three-phase power transformer with delta-connected windings, the induced voltage differences are estimated to use the line currents, because the delta winding currents are practically unavailable. Six detectors are suggested for fault detection. An additional three detectors and a rule for faulted phase and winding identification are presented as well. The proposed algorithm can not only detect an internal fault, but also identify the faulted phase and winding of a three-winding power transformer. The various test results with Electromagnetic Transients Program (EMTP)-generated data show that the proposed algorithm successfully discriminates internal faults from normal operating conditions including magnetic inrush and over-excitation. This paper concludes by implementing the algorithm into a prototype relay based on a digital signal processor. Full article
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Open AccessReview Towards a Friendly Energy Management Strategy for Hybrid Electric Vehicles with Respect to Pollution, Battery and Drivability
Energies 2014, 7(9), 6013-6030; https://doi.org/10.3390/en7096013
Received: 16 April 2014 / Revised: 11 July 2014 / Accepted: 31 July 2014 / Published: 12 September 2014
Cited by 4 | PDF Full-text (427 KB) | HTML Full-text | XML Full-text
Abstract
The paper proposes a generic methodology to incorporate constraints (pollutant emission, battery health, drivability) into on-line energy management strategies (EMSs) for hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs). The integration of each constraint into the EMS, made with the Pontryagin
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The paper proposes a generic methodology to incorporate constraints (pollutant emission, battery health, drivability) into on-line energy management strategies (EMSs) for hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs). The integration of each constraint into the EMS, made with the Pontryagin maximum principle, shows a tradeoff between the fuel consumption and the constraint introduced. As state dynamics come into play (catalyst temperature, battery cell temperature, etc.), the optimization problem becomes more complex. Simulation results are presented to highlight the contribution of this generic strategy, including constraints compared to the standard approach. These results show that it is possible to find an energy management strategy that takes into account an increasing number of constraints (drivability, pollution, aging, environment, etc.). However, taking these constraints into account increases fuel consumption (the existence of a trade-off curve). This trade-off can be sometimes difficult to find, and the tools developed in this paper should help to find an acceptable solution quickly Full article
(This article belongs to the Special Issue Advances in Hybrid Vehicles)
Open AccessArticle An Adaptive Gain Nonlinear Observer for State of Charge Estimation of Lithium-Ion Batteries in Electric Vehicles
Energies 2014, 7(9), 5995-6012; https://doi.org/10.3390/en7095995
Received: 24 July 2014 / Revised: 25 August 2014 / Accepted: 1 September 2014 / Published: 10 September 2014
Cited by 17 | PDF Full-text (500 KB) | HTML Full-text | XML Full-text
Abstract
The state of charge (SOC) is important for the safety and reliability of battery operation since it indicates the remaining capacity of a battery. However, it is difficult to get an accurate value of SOC, because the SOC cannot be
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The state of charge (SOC) is important for the safety and reliability of battery operation since it indicates the remaining capacity of a battery. However, it is difficult to get an accurate value of SOC, because the SOC cannot be directly measured by a sensor. In this paper, an adaptive gain nonlinear observer (AGNO) for SOC estimation of lithium-ion batteries (LIBs) in electric vehicles (EVs) is proposed. The second-order resistor–capacitor (2RC) equivalent circuit model is used to simulate the dynamic behaviors of a LIB, based on which the state equations are derived to design the AGNO for SOC estimation. The model parameters are identified using the exponential-function fitting method. The sixth-order polynomial function is used to describe the highly nonlinear relationship between the open circuit voltage (OCV) and the SOC. The convergence of the proposed AGNO is proved using the Lyapunov stability theory. Two typical driving cycles, including the New European Driving Cycle (NEDC) and Federal Urban Driving Schedule (FUDS) are adopted to evaluate the performance of the AGNO by comparing with the unscented Kalman filter (UKF) algorithm. The experimental results show that the AGNO has better performance than the UKF algorithm in terms of reducing the computation cost, improving the estimation accuracy and enhancing the convergence ability. Full article
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Open AccessArticle A Semantic Middleware Architecture Focused on Data and Heterogeneity Management within the Smart Grid
Energies 2014, 7(9), 5953-5994; https://doi.org/10.3390/en7095953
Received: 3 June 2014 / Revised: 23 August 2014 / Accepted: 2 September 2014 / Published: 10 September 2014
Cited by 10 | PDF Full-text (2615 KB) | HTML Full-text | XML Full-text
Abstract
There is an increasing tendency of turning the current power grid, essentially unaware of variations in electricity demand and scattered energy sources, into something capable of bringing a degree of intelligence by using tools strongly related to information and communication technologies, thus turning
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There is an increasing tendency of turning the current power grid, essentially unaware of variations in electricity demand and scattered energy sources, into something capable of bringing a degree of intelligence by using tools strongly related to information and communication technologies, thus turning into the so-called Smart Grid. In fact, it could be considered that the Smart Grid is an extensive smart system that spreads throughout any area where power is required, providing a significant optimization in energy generation, storage and consumption. However, the information that must be treated to accomplish these tasks is challenging both in terms of complexity (semantic features, distributed systems, suitable hardware) and quantity (consumption data, generation data, forecasting functionalities, service reporting), since the different energy beneficiaries are prone to be heterogeneous, as the nature of their own activities is. This paper presents a proposal on how to deal with these issues by using a semantic middleware architecture that integrates different components focused on specific tasks, and how it is used to handle information at every level and satisfy end user requests. Full article
(This article belongs to the Special Issue Green IT and IT for Smart Energy Savings)
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