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Energies, Volume 4, Issue 10 (October 2011), Pages 1478-1839

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Research

Jump to: Review

Open AccessArticle Cost Benefit Analysis of Using Clean Energy Supplies to Reduce Greenhouse Gas Emissions of Global Automotive Manufacturing
Energies 2011, 4(10), 1478-1494; doi:10.3390/en4101478
Received: 14 July 2011 / Revised: 19 September 2011 / Accepted: 22 September 2011 / Published: 28 September 2011
Cited by 12 | PDF Full-text (344 KB) | HTML Full-text | XML Full-text
Abstract
Automotive manufacturing is energy-intensive. The consumed energy contributes to the generation of significant amounts of greenhouse gas (GHG) emissions by the automotive manufacturing industry. In this paper, a study is conducted on assessing the application potential of such clean energy power systems as
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Automotive manufacturing is energy-intensive. The consumed energy contributes to the generation of significant amounts of greenhouse gas (GHG) emissions by the automotive manufacturing industry. In this paper, a study is conducted on assessing the application potential of such clean energy power systems as solar PV, wind and fuel cells in reducing the GHG emissions of the global auto manufacturing industry. The study is conducted on the representative solar PV, wind and fuel cell clean energy systems available on the commercial market in six representative locations of GM’s global facilities, including the United States, Mexico, Brazil, China, Egypt and Germany. The results demonstrate that wind power is superior to other two clean energy technologies in the economic performance of the GHG mitigation effect. Among these six selected countries, the highest GHG emission mitigation potential is in China, through wind power supply. The maximum GHG reduction could be up to 60 tons per $1,000 economic investment on wind energy supply in China. The application of wind power systems in the United States and Germany could also obtain relatively high GHG reductions of between 40–50 tons per $1,000 economic input. When compared with wind energy, the use of solar and fuel cell power systems have much less potential for GHG mitigation in the six countries selected. The range of median GHG mitigation values resulting from solar and wind power supply are almost at the same level. Full article
(This article belongs to the Special Issue Technologies to Achieve Greenhouse Gas Mitigation)
Open AccessArticle Forecasting Monthly Electric Energy Consumption Using Feature Extraction
Energies 2011, 4(10), 1495-1507; doi:10.3390/en4101495
Received: 22 July 2011 / Revised: 14 September 2011 / Accepted: 20 September 2011 / Published: 28 September 2011
Cited by 15 | PDF Full-text (299 KB) | HTML Full-text | XML Full-text
Abstract
Monthly forecasting of electric energy consumption is important for planning the generation and distribution of power utilities. However, the features of this time series are so complex that directly modeling is difficult. Three kinds of relatively simple series can be derived when a
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Monthly forecasting of electric energy consumption is important for planning the generation and distribution of power utilities. However, the features of this time series are so complex that directly modeling is difficult. Three kinds of relatively simple series can be derived when a discrete wavelet transform is used to extract the raw features, namely, the rising trend, periodic waves, and stochastic series. After the elimination of the stochastic series, the rising trend and periodic waves were modeled separately by a grey model and radio basis function neural networks. Adding the forecasting values of each model can yield the forecasting results for monthly electricity consumption. The grey model has a good capability for simulating any smoothing convex trend. In addition, this model can mitigate minor stochastic effects on the rising trend. The extracted periodic wave series, which contain relatively less information and comprise simple regular waves, can improve the generalization capability of neural networks. The case study on electric energy consumption in China shows that the proposed method is better than those traditionally used in terms of both forecasting precision and expected risk. Full article
(This article belongs to the Special Issue Intelligent Energy Demand Forecasting)
Open AccessArticle How Will Hydroelectric Power Generation Develop under Climate Change Scenarios? A Case Study in the Upper Danube Basin
Energies 2011, 4(10), 1508-1541; doi:10.3390/en4101508
Received: 30 June 2011 / Revised: 6 September 2011 / Accepted: 22 September 2011 / Published: 30 September 2011
Cited by 16 | PDF Full-text (3798 KB) | HTML Full-text | XML Full-text
Abstract
Climate change has a large impact on water resources and thus on hydropower. Hydroelectric power generation is closely linked to the regional hydrological situation of a watershed and reacts sensitively to changes in water quantity and seasonality. The development of hydroelectric power generation
[...] Read more.
Climate change has a large impact on water resources and thus on hydropower. Hydroelectric power generation is closely linked to the regional hydrological situation of a watershed and reacts sensitively to changes in water quantity and seasonality. The development of hydroelectric power generation in the Upper Danube basin was modelled for two future decades, namely 2021–2030 and 2051–2060, using a special hydropower module coupled with the physically-based hydrological model PROMET. To cover a possible range of uncertainties, 16 climate scenarios were taken as meteorological drivers which were defined from different ensemble outputs of a stochastic climate generator, based on the IPCC-SRES-A1B emission scenario and four regional climate trends. Depending on the trends, the results show a slight to severe decline in hydroelectric power generation. Whilst the mean summer values indicate a decrease, the mean winter values display an increase. To show past and future regional differences within the Upper Danube basin, three hydropower plants at individual locations were selected. Inter-annual differences originate predominately from unequal contributions of the runoff compartments rain, snow- and ice-melt. Full article
(This article belongs to the Special Issue Advances in Hydroelectric Power Generation)
Open AccessArticle Intelligent Stability Design of Large Underground Hydraulic Caverns: Chinese Method and Practice
Energies 2011, 4(10), 1542-1562; doi:10.3390/en4101542
Received: 27 June 2011 / Revised: 14 September 2011 / Accepted: 29 September 2011 / Published: 10 October 2011
Cited by 6 | PDF Full-text (1562 KB) | HTML Full-text | XML Full-text
Abstract
The global energy shortage has revived the interest in hydroelectric power, but extreme geological condition always pose challenges to the construction of hydroelectric power stations with large underground caverns. To solve the problem of safe design of large underground caverns, a Chinese-style intelligent
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The global energy shortage has revived the interest in hydroelectric power, but extreme geological condition always pose challenges to the construction of hydroelectric power stations with large underground caverns. To solve the problem of safe design of large underground caverns, a Chinese-style intelligent stability design, representing recent developments in Chinese techniques for the construction of underground hydropower systems is presented. The basic aim of this method is to help designers improve the stability and design efficiency of large underground hydropower cavern groups. Its flowchart consists of two parts, one is initial design with an ordinal structure, and the other is dynamic design with a closed loop structure. In each part of the flowchart, analysis techniques, analysis content and design parameters for caverns’ stability are defined, respectively. Thus, the method provides designers with a bridge from the basic information of objective engineering to reasonable design parameters for managing the stability of hydraulic cavern groups. Application to two large underground caverns shows that it is a scientific and economical method for safely constructing underground hydraulic caverns. Full article
(This article belongs to the Special Issue Advances in Hydroelectric Power Generation)
Open AccessArticle Influences of Corrosive Sulfur on Copper Wires and Oil-Paper Insulation in Transformers
Energies 2011, 4(10), 1563-1573; doi:10.3390/en4101563
Received: 2 August 2011 / Revised: 19 September 2011 / Accepted: 9 October 2011 / Published: 12 October 2011
Cited by 10 | PDF Full-text (1057 KB) | HTML Full-text | XML Full-text
Abstract
Oil-impregnated paper is widely used in power transmission equipment as a reliable insulation. However, copper sulphide deposition on oil-paper insulation can lead to insulation failures in power transformers. This paper presents the influences of copper sulfur corrosion and copper sulphide deposition on copper
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Oil-impregnated paper is widely used in power transmission equipment as a reliable insulation. However, copper sulphide deposition on oil-paper insulation can lead to insulation failures in power transformers. This paper presents the influences of copper sulfur corrosion and copper sulphide deposition on copper wires and oil-paper insulation in power transformers. Thermal aging tests of paper-wrapped copper wires and bare copper wires in insulating oil were carried out at 130 °C and 150 °C in laboratory. The corrosive characteristics of paper-wrapped copper wires and bare copper wires were analyzed. Dielectric properties of insulation paper and insulating oil were also analyzed at different stages of the thermal aging tests using a broadband dielectric spectrometer. Experiments and analysis results show that copper sulfide deposition on surfaces of copper wires and insulation paper changes the surface structures of copper wires and insulation paper. Copper sulfur corrosion changes the dielectric properties of oil-paper insulation, and the copper sulfide deposition greatly reduces the electrical breakdown strength of oil-paper insulation. Metal passivator is capable of preventing copper wires from sulfur corrosion. The experimental results are helpful for investigations for fault diagnosis of internal insulation in power transformers. Full article
Open AccessArticle On the Effects of Geometry Control on the Performance of Overtopping Wave Energy Converters
Energies 2011, 4(10), 1574-1600; doi:10.3390/en4101574
Received: 14 September 2011 / Revised: 13 October 2011 / Accepted: 14 October 2011 / Published: 19 October 2011
Cited by 5 | PDF Full-text (570 KB) | HTML Full-text | XML Full-text
Abstract
Overtopping wave energy converters (OWECs) are designed to extract energy from ocean waves based on wave overtopping into a reservoir, which is emptied into the ocean through a set of low-head turbines, and typically feature a low crest freeboard and a smooth impermeable
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Overtopping wave energy converters (OWECs) are designed to extract energy from ocean waves based on wave overtopping into a reservoir, which is emptied into the ocean through a set of low-head turbines, and typically feature a low crest freeboard and a smooth impermeable steep slope. In the process of optimizing the performance of OWECs, the question arises whether adapting the slope geometry to the variable wave characteristics at the deployment site (i.e., geometry control) can increase the overall hydraulic efficiency and overall hydraulic power compared to a fixed slope geometry. The effect of five different geometry control scenarios on the overall hydraulic efficiency and overall hydraulic power of OWECs has been simulated for three possible deployment sites using empirical prediction formulae. The results show that the effect of an adaptive slope angle is relatively small. On the other hand, adapting the crest freeboard of the OWECs to the wave characteristics increases the overall hydraulic efficiency and power. Based on the simulations, gains in overall hydraulic power of at least 30% are achievable when applying an adaptive crest freeboard compared to a fixed crest freeboard. Full article
Open AccessArticle Optimization of the Dilute Acid Hydrolyzator for Cellulose-to-Bioethanol Saccharification
Energies 2011, 4(10), 1601-1623; doi:10.3390/en4101601
Received: 1 August 2011 / Revised: 23 September 2011 / Accepted: 8 October 2011 / Published: 20 October 2011
Cited by 4 | PDF Full-text (778 KB) | HTML Full-text | XML Full-text
Abstract
The production of fermentable sugar solutions for bioethanol production is optimized. The process of acid hydrolysis using dilute H2SO4 was selected. Suitable lignocellulosics which are abundant in the Mediterranean (corn stover, hardwood and wheat straw) were investigated, and therefore their
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The production of fermentable sugar solutions for bioethanol production is optimized. The process of acid hydrolysis using dilute H2SO4 was selected. Suitable lignocellulosics which are abundant in the Mediterranean (corn stover, hardwood and wheat straw) were investigated, and therefore their exploitation could be economically feasible. The process was studied in the two most common hydrolyzators (batch and continuous stirred) by developing a specific simulator for different raw materials. The simulation was applied in a wide range of temperatures (100–240 °C) and acid concentrations (0.5–3.0% w/w), in order to optimize the productivity of fermentable pentosans and hexosans. It was confirmed that the production of sugar-rich solutions required a two-stage process; in the first stage the degradation of sugars takes place, since pentoses are formulated under milder conditions than hexoses; in the second stage of simulation, a variety of samples with high sugar concentration and low degradation products are tested. The xylose productivity ranges between 85–95% under the most optimal conditions compared to the theoretical values, while large variations in glucose were frequent (10–55%) in comparison with the theoretical values. The best theoretical results were achieved for wheat straw hydrolysis in a batch reactor. Full article
Open AccessArticle An Inexact Mix-Integer Two-Stage Linear Programming Model for Supporting the Management of a Low-Carbon Energy System in China
Energies 2011, 4(10), 1657-1686; doi:10.3390/en4101657
Received: 13 July 2011 / Revised: 11 October 2011 / Accepted: 12 October 2011 / Published: 21 October 2011
Cited by 11 | PDF Full-text (509 KB) | HTML Full-text | XML Full-text
Abstract
In view of the great contribution of coal-fired units to CO2 emissions, the coupled coal and power system with consideration of CO2 mitigation is a typical sub-system of the highly emitting Chinese energy system for low-carbon studies. In this study, an
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In view of the great contribution of coal-fired units to CO2 emissions, the coupled coal and power system with consideration of CO2 mitigation is a typical sub-system of the highly emitting Chinese energy system for low-carbon studies. In this study, an inexact mix-integer two-stage programming (IMITSP) model for the management of low-carbon energy systems was developed based on the integration of multiple inexact programming techniques. Uncertainties and complexities related to the carbon mitigation issues in the coupled coal and power system can be effectively reflected and dealt with in this model. An optimal CO2 mitigation strategy associated with stochastic power-generation demand under specific CO2 mitigation targets could be obtained. Dynamic analysis of capacity expansion, facility improvement, coal selection, as well as coal blending within a multi-period and multi-option context could be facilitated. The developed IMITSP model was applied to a semi-hypothetical case of long-term coupled management of coal and power within a low-carbon energy system in north China. The generated decision alternatives could help decision makers identify desired strategies related to coal production and allocation, CO2 emission mitigation, as well as facility capacity upgrade and expansion under various social-economic, ecological, environmental and system-reliability constraints. It could also provide interval solutions with a minimized system cost, a maximized system reliability and a maximized power-generation demand security. Moreover, the developed model could provide an in-depth insight into various CO2 mitigation technologies and the associated environmental and economic implications under a given reduction target. Tradeoffs among system costs, energy security and CO2 emission reduction could be analyzed. Full article
(This article belongs to the Special Issue Low Carbon Transitions Worldwide)
Open AccessArticle Outdoor Storage Characteristics of Single-Pass Large Square Corn Stover Bales in Iowa
Energies 2011, 4(10), 1687-1695; doi:10.3390/en4101687
Received: 30 August 2011 / Revised: 27 September 2011 / Accepted: 17 October 2011 / Published: 21 October 2011
Cited by 17 | PDF Full-text (181 KB) | HTML Full-text | XML Full-text
Abstract
Year-round operation of biorefineries can be possible only if the continuous flow of cellulosic biomass is guaranteed. If corn (Zea mays) stover is the primary cellulosic biomass, it is essential to recognize that this feedstock has a short annual harvest window
[...] Read more.
Year-round operation of biorefineries can be possible only if the continuous flow of cellulosic biomass is guaranteed. If corn (Zea mays) stover is the primary cellulosic biomass, it is essential to recognize that this feedstock has a short annual harvest window (≤1–2 months) and therefore cost effective storage techniques that preserve feedstock quality must be identified. This study evaluated two outdoor and one indoor storage strategies for corn stover bales in Iowa. High- and low-moisture stover bales were prepared in the fall of 2009, and stored either outdoors with two different types of cover (tarp and breathable film) or within a building for 3 or 9 months. Dry matter loss (DML), changes in moisture and biomass compositions (fiber and ultimate analyses) were determined. DML for bales stored outdoor with tarp and breathable film covers were in the ranges of 5–11 and 14–17%, respectively. More than half of the total DML occurred early during the storage. There were measurable differences in carbon, hydrogen, nitrogen, sulfur, oxygen, cellulose, hemi-cellulose and acid detergent lignin for the different storage treatments, but the changes were small and within a narrow range. For the bale storage treatments investigated, cellulose content increased by as much as 4%s from an initial level of ~41%, hemicellulose content changed by −2 to 1% from ~34%, and acid detergent lignin contents increased by as much as 3% from an initial value of ~5%. Tarp covered bales stored the best in this study, but other methods, such as tube-wrapping, and economics need further investigation. Full article
(This article belongs to the Special Issue Biomass and Biofuels)
Open AccessArticle Valuing Expansions of the Electricity Transmission Network under Uncertainty: The Binodal Case
Energies 2011, 4(10), 1696-1727; doi:10.3390/en4101696
Received: 1 August 2011 / Revised: 27 September 2011 / Accepted: 12 October 2011 / Published: 21 October 2011
Cited by 1 | PDF Full-text (633 KB) | HTML Full-text | XML Full-text
Abstract
Transmission investments are currently needed to meet an increasing electricity demand, to address security of supply concerns, and to reach carbon-emissions targets. A key issue when assessing the benefits from an expanded grid concerns the valuation of the uncertain cash flows that result
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Transmission investments are currently needed to meet an increasing electricity demand, to address security of supply concerns, and to reach carbon-emissions targets. A key issue when assessing the benefits from an expanded grid concerns the valuation of the uncertain cash flows that result from the expansion. We propose a valuation model that accommodates both physical and economic uncertainties following the Real Options approach. It combines optimization techniques with Monte Carlo simulation. We illustrate the use of our model in a simplified, two-node grid and assess the decision whether to invest or not in a particular upgrade. The generation mix includes coal- and natural gas-fired stations that operate under carbon constraints. The underlying parameters are estimated from observed market data. Full article
(This article belongs to the Special Issue Technologies to Achieve Greenhouse Gas Mitigation)
Open AccessArticle Incorporating the Variability of Wind Power with Electric Heat Pumps
Energies 2011, 4(10), 1748-1762; doi:10.3390/en4101748
Received: 25 August 2011 / Revised: 26 September 2011 / Accepted: 30 September 2011 / Published: 24 October 2011
Cited by 10 | PDF Full-text (400 KB) | HTML Full-text | XML Full-text
Abstract
With the mass introduction of wind power in Northern China, wind power variability has appeared. In this article, both existing electric heat pumps (EHPs) and coal-fired combined heat and power (CHP) facilities, which are generally equipped with extraction-condensing steam turbines coupled with district
[...] Read more.
With the mass introduction of wind power in Northern China, wind power variability has appeared. In this article, both existing electric heat pumps (EHPs) and coal-fired combined heat and power (CHP) facilities, which are generally equipped with extraction-condensing steam turbines coupled with district heating for space heating purposes, are proposed to incorporate the variability of wind power equivalently. The authors’ proposal arises from the facts that: (1) EHPs can provide space heating in the domestic sector with little thermal comfort change (e.g., energy carriers for space heating purposes can be switched from heating water to electricity); (2) coal-fired CHP units in Northern China can usually generate more electrical power corresponding to a shaved thermal power production. Thus, it is suggested that heating water from CHP units be shaved when the wind generation is low due to the variability of wind power, so as to enable more electrical power production and compensate for the corresponding insufficient wind generation. Following this, in the future and for some space heating loads at appropriate distances, electricity used as energy carrier should be converted by electric heat pumps for space heating. Thus, more electricity consumption will be achieved so as to avoid wasting wind power when the wind generation it is high. A numerical simulation is performed in order to illustrate the authors’ proposal. It is shown that the impact of variability of wind generation can be equivalently reduced to a great extent, which enable more wind power integration instead of curtailment and potential energy conservation. Moreover, in contrast to before, both the thermal and electrical power of coal-fired CHP units are no longer constants. In addition, the ratio of electrical to thermal power of CHP units is no longer constant either, and results in less energy consumption compared with fixed ratio. Finally, electricity consumed by end users’ EHPs, which are devoted to space heating for various spatial distances and time points, is figured out. Full article
Open AccessArticle Kaolinite and Silica Dispersions in Low-Salinity Environments: Impact on a Water-in-Crude Oil Emulsion Stability
Energies 2011, 4(10), 1763-1778; doi:10.3390/en4101763
Received: 11 August 2011 / Revised: 17 October 2011 / Accepted: 19 October 2011 / Published: 24 October 2011
Cited by 5 | PDF Full-text (2010 KB) | HTML Full-text | XML Full-text
Abstract
This research aims at providing evidence of particle suspension contributions to emulsion stability, which has been cited as a contributing factor in crude oil recovery by low-salinity waterflooding. Kaolinite and silica particle dispersions were characterized as functions of brine salinity. A reference aqueous
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This research aims at providing evidence of particle suspension contributions to emulsion stability, which has been cited as a contributing factor in crude oil recovery by low-salinity waterflooding. Kaolinite and silica particle dispersions were characterized as functions of brine salinity. A reference aqueous phase, representing reservoir brine, was used and then diluted with distilled water to obtain brines at 10 and 100 times lower Total Dissolved Solid (TDS). Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) were used to examine at the morphology and composition of clays. The zeta potential and particle size distribution were also measured. Emulsions were prepared by mixing a crude oil with brine, with and without dispersed particles to investigate emulsion stability. The clay zeta potential as a function of pH was used to investigate the effect of particle charge on emulsion stability. The stability was determined through bottle tests and optical microscopy. Results show that both kaolinite and silica promote emulsion stability. Also, kaolinite, roughly 1 mm in size, stabilizes emulsions better than larger clay particles. Silica particles of larger size (5 µm) yielded more stable emulsions than smaller silica particles do. Test results show that clay particles with zero point of charge (ZPC) at low pH become less effective at stabilizing emulsions, while silica stabilizes emulsions better at ZPC. These result shed light on emulsion stabilization in low-salinity waterflooding. Full article
(This article belongs to the Special Issue Advances in Petroleum Engineering)
Open AccessArticle Polymer Combustion as a Basis for Hybrid Propulsion: A Comprehensive Review and New Numerical Approaches
Energies 2011, 4(10), 1779-1839; doi:10.3390/en4101779
Received: 28 July 2011 / Revised: 11 October 2011 / Accepted: 12 October 2011 / Published: 24 October 2011
Cited by 3 | PDF Full-text (2314 KB) | HTML Full-text | XML Full-text
Abstract
Hybrid Propulsion is an attractive alternative to conventional liquid and solid rocket motors. This is an active area of research and technological developments. Potential wide application of Hybrid Engines opens the possibility for safer and more flexible space vehicle launching and manoeuvring. The
[...] Read more.
Hybrid Propulsion is an attractive alternative to conventional liquid and solid rocket motors. This is an active area of research and technological developments. Potential wide application of Hybrid Engines opens the possibility for safer and more flexible space vehicle launching and manoeuvring. The present paper discusses fundamental combustion issues related to further development of Hybrid Rockets. The emphasis is made on the two aspects: (1) properties of potential polymeric fuels, and their modification, and (2) implementation of comprehensive CFD models for combustion in Hybrid Engines. Fundamentals of polymeric fuel combustion are discussed. Further, steps necessary to accurately describe their burning behaviour by means of CFD models are investigated. Final part of the paper presents results of preliminary CFD simulations of fuel burning process in Hybrid Engine using a simplified set-up. Full article
(This article belongs to the Special Issue Combustion for Aerospace Propulsion)

Review

Jump to: Research

Open AccessReview A Review on Optimization Modeling of Energy Systems Planning and GHG Emission Mitigation under Uncertainty
Energies 2011, 4(10), 1624-1656; doi:10.3390/en4101624
Received: 19 July 2011 / Revised: 1 September 2011 / Accepted: 5 September 2011 / Published: 21 October 2011
Cited by 29 | PDF Full-text (289 KB) | HTML Full-text | XML Full-text
Abstract
Energy is crucial in supporting people’s daily lives and the continual quest for human development. Due to the associated complexities and uncertainties, decision makers and planners are facing increased pressure to respond more effectively to a number of energy-related issues and conflicts, as
[...] Read more.
Energy is crucial in supporting people’s daily lives and the continual quest for human development. Due to the associated complexities and uncertainties, decision makers and planners are facing increased pressure to respond more effectively to a number of energy-related issues and conflicts, as well as GHG emission mitigation within the multiple scales of energy management systems (EMSs). This quandary requires a focused effort to resolve a wide range of issues related to EMSs, as well as the associated economic and environmental implications. Effective systems analysis approaches under uncertainty to successfully address interactions, complexities, uncertainties, and changing conditions associated with EMSs is desired, which require a systematic investigation of the current studies on energy systems. Systems analysis and optimization modeling for low-carbon energy systems planning with the consideration of GHG emission reduction under uncertainty is thus comprehensively reviewed in this paper. A number of related methodologies and applications related to: (a) optimization modeling of GHG emission mitigation; (b) optimization modeling of energy systems planning under uncertainty; and (c) model-based decision support tools are examined. Perspectives of effective management schemes are investigated, demonstrating many demanding areas for enhanced research efforts, which include issues of data availability and reliability, concerns in uncertainty, necessity of post-modeling analysis, and usefulness of development of simulation techniques. Full article
(This article belongs to the Special Issue Low Carbon Transitions Worldwide)
Open AccessReview Experimental Study of Formation Damage during Underbalanced-Drilling in Naturally Fractured Formations
Energies 2011, 4(10), 1728-1747; doi:10.3390/en4101728
Received: 2 June 2011 / Revised: 1 September 2011 / Accepted: 17 October 2011 / Published: 24 October 2011
PDF Full-text (381 KB) | XML Full-text
Abstract
This paper describes an experimental investigation of formation damage in a fractured carbonate core sample under underbalanced drilling (UBD) conditions. A major portion of this study has concentrated on problems which are often associated with UBD and the development of a detailed protocol
[...] Read more.
This paper describes an experimental investigation of formation damage in a fractured carbonate core sample under underbalanced drilling (UBD) conditions. A major portion of this study has concentrated on problems which are often associated with UBD and the development of a detailed protocol for proper design and execution of an UBD program. Formation damage effects, which may occur even if the underbalanced pressure condition is maintained 100% of the time during drilling operation, have been studied. One major concern for formation damage during UBD operations is the loss of the under-balanced pressure condition. Hence, it becomes vital to evaluate the sensitivity of the formation to the effect of an overbalanced pulse situation. The paper investigates the effect of short pulse overbalance pressure during underbalanced conditions in a fractured chalk core sample. Special core tests using a specially designed core holder are conducted on the subject reservoir core. Both overbalance and underbalanced tests were conducted with four UBD drilling fluids. Core testing includes measurements of the initial permeability and return permeability under two different pressure conditions (underbalanced and overbalanced). Then the procedure is followed by applying a differential pressure on the core samples to mimic the drawdown effect to determine the return permeability capacity. In both UBD and short pulse OBP four mud formulations are used which are: lab oil, brine (3% KCL), water-based mud (bentonite with XC polymer) and fresh water. The return permeability measurements show that a lab oil system performed fairly well during UBD and short OB conditions. The results indicate that a short overbalance pressure provides a significant reduction in permeability of the fractured formations. In most tests, even application of a high drawdown pressure during production cannot restore the initial permeability by more than 40%. Full article
(This article belongs to the Special Issue Advances in Petroleum Engineering)

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