Energies

10 pages, 286 KB

Open AccessArticle

Combustion of Corn Stover Bales in a Small 146-kW Boiler

by René Morissette, Philippe Savoie and Joey Villeneuve

Energies 2011, 4(7), 1102-1111; https://doi.org/10.3390/en4071102 - 22 Jul 2011

Cited by 27 | Viewed by 10369

Spring harvested corn stover was used for direct combustion in a 146 kW dual chamber boiler designed for wood logs. Stover had a very low moisture content (6.83 ± 0.17%), a gross calorific value (GCV) of 18.57 MJ/kg of dry matter (±0.32 MJ/kg [...] Read more.

Spring harvested corn stover was used for direct combustion in a 146 kW dual chamber boiler designed for wood logs. Stover had a very low moisture content (6.83 ± 0.17%), a gross calorific value (GCV) of 18.57 MJ/kg of dry matter (±0.32 MJ/kg DM) and an ash content of 5.88% (±1.15%). Small stover bales (8.83 ± 0.90 kg) were placed manually in the upper combustion chamber at a rate of 10.5 to 12.8 kg/h over a 24-h period, with three replications, and compared to a control wood combustion trial (12.1 kg/h during 24 h). The overall heat transfer efficiency for stover was lower than for wood (57% vs. 77%). Stover bales produced on average 7.5% ash which included about 2% of unburned residues while wood produced 1.7% ash. CO gas emissions averaged 1324 mg/m³ for stover (118 mg/m³ for wood). The corn stover showed a good calorific potential, but it would have to be densified and the boiler should be modified to improve airflow, completeness of combustion and handling of the large amount of ash formed. Full article

(This article belongs to the Special Issue Biomass and Biofuels)

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15 pages, 886 KB

Open AccessArticle

Improved Bagging Algorithm for Pattern Recognition in UHF Signals of Partial Discharges

by Tianyan Jiang, Jian Li, Yuanbing Zheng and Caixin Sun

Energies 2011, 4(7), 1087-1101; https://doi.org/10.3390/en4071087 - 21 Jul 2011

Cited by 55 | Viewed by 7698

Abstract

This paper presents an Improved Bagging Algorithm (IBA) to recognize ultra-high-frequency (UHF) signals of partial discharges (PDs). This approach establishes the sample information entropy for each sample and the re-sampling process of the traditional Bagging algorithm is optimized. Four typical discharge models were [...] Read more.

This paper presents an Improved Bagging Algorithm (IBA) to recognize ultra-high-frequency (UHF) signals of partial discharges (PDs). This approach establishes the sample information entropy for each sample and the re-sampling process of the traditional Bagging algorithm is optimized. Four typical discharge models were designed in the laboratory to simulate the internal insulation faults of power transformers. The optimized third order Peano fractal antenna was applied to capture the PD UHF signals. Multi-scale fractal dimensions as well as energy parameters extracted from the decomposed signals by wavelet packet transform were used as the characteristic parameters for pattern recognition. In order to verify the effectiveness of the proposed algorithm, the back propagation neural network (BPNN) and the support vector machine (SVM) based on the IBA were adopted in this paper to carry out the pattern recognition for PD UHF signals. Experimental results show that the proposed approach of IBA can effectively enhance the generalization capability and also improve the accuracy of the recognition for PD UHF signals. Full article

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29 pages, 390 KB

Open AccessReview

Stability Proxies for Water-in-Oil Emulsions and Implications in Aqueous-based Enhanced Oil Recovery

by Vladimir Alvarado, Xiuyu Wang and Mehrnoosh Moradi

Energies 2011, 4(7), 1058-1086; https://doi.org/10.3390/en4071058 - 18 Jul 2011

Cited by 68 | Viewed by 16878

Abstract

Several researchers have proposed that mobility control mechanisms can positively contribute to oil recovery in the case of emulsions generated in Enhanced-Oil Recovery (EOR) operations. Chemical EOR techniques that use alkaline components or/and surfactants are known to produce undesirable emulsions that create operational [...] Read more.

Several researchers have proposed that mobility control mechanisms can positively contribute to oil recovery in the case of emulsions generated in Enhanced-Oil Recovery (EOR) operations. Chemical EOR techniques that use alkaline components or/and surfactants are known to produce undesirable emulsions that create operational problems and are difficult to break. Other water-based methods have been less studied in this sense. EOR processes such as polymer flooding and LoSal^TM injection require adjustments of water chemistry, mainly by lowering the ionic strength of the solution or by decreasing hardness. The decreased ionic strength of EOR solutions can give rise to more stable water-in-oil emulsions, which are speculated to improve mobility ratio between the injectant and the displaced oil. The first step toward understanding the connection between the emulsions and EOR mechanisms is to show that EOR conditions, such as salinity and hardness requirements, among others, are conducive to stabilizing emulsions. In order to do this, adequate stability proxies are required. This paper reviews commonly used emulsion stability proxies and explains the advantages and disadvantage of methods reviewed. This paper also reviews aqueous-based EOR processes with focus on heavy oil to contextualize in-situ emulsion stabilization conditions. This context sets the basis for comparison of emulsion stability proxies. Full article

(This article belongs to the Special Issue Oil Recovery)

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7 pages, 312 KB

Open AccessCommunication

Time to Substitute Wood Bioenergy for Nuclear Power in Japan

by Nophea Sasaki, Toshiaki Owari and Francis E. Putz

Energies 2011, 4(7), 1051-1057; https://doi.org/10.3390/en4071051 - 6 Jul 2011

Cited by 8 | Viewed by 10529

Abstract

Damage to the Fukushima Nuclear Power Plant by the recent earthquake and tsunami that hit northern Japan should stimulate consideration of alternative sources of energy. In particular, if managed appropriately, the 25.1 million ha of Japanese forests could be an important source of [...] Read more.

Damage to the Fukushima Nuclear Power Plant by the recent earthquake and tsunami that hit northern Japan should stimulate consideration of alternative sources of energy. In particular, if managed appropriately, the 25.1 million ha of Japanese forests could be an important source of wood biomass for bioenergy production. Here, we discuss policy incentives for substituting wood bioenergy for nuclear power, thereby creating a safer society while better managing the forest resources in Japan. Full article

(This article belongs to the Special Issue Biomass and Biofuels)

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15 pages, 371 KB

Open AccessArticle

Joint Operation of the Multi-Reservoir System of the Three Gorges and the Qingjiang Cascade Reservoirs

by Shenglian Guo, Jionghong Chen, Yu Li, Pan Liu and Tianyuan Li

Energies 2011, 4(7), 1036-1050; https://doi.org/10.3390/en4071036 - 4 Jul 2011

Cited by 69 | Viewed by 9976

Abstract

Optimal utilization of available water resources has become more urgent due to the rapid growth of the economy and population. The joint operation of the Three Gorges cascade and Qingjiang cascade reservoirs in China was studied in this paper. Choosing maximization of hydropower [...] Read more.

Optimal utilization of available water resources has become more urgent due to the rapid growth of the economy and population. The joint operation of the Three Gorges cascade and Qingjiang cascade reservoirs in China was studied in this paper. Choosing maximization of hydropower generation and hydropower revenue as objective functions respectively, optimal models were established for individual and joint operation of the cascade reservoirs. The models were solved by the progressive optimality algorithm. The storage and electric compensation benefits among cascade reservoirs were analyzed. The daily inflow data of consecutive hydrological years of 1982–1987 were selected for a case study. Compared with the design operation rule, the joint operation of the multi-reservoir system can generate 5.992 billion kWh of extra power or an increase of 5.70% by the objective function of maximum hydropower generation. Through reservoir storage compensation, the spilled water of the Three Gorges and Qingjiang cascade reservoirs was decreased by 78.741 and 5.384 billion m³, respectively. Full article

(This article belongs to the Special Issue Advances in Hydroelectric Power Generation)

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11 pages, 169 KB

Open AccessArticle

Discussions on the Architecture and Operation Mode of Future Power Grids

by Liye Xiao, Liangzhen Lin and Yi Liu

Energies 2011, 4(7), 1025-1035; https://doi.org/10.3390/en4071025 - 4 Jul 2011

Cited by 21 | Viewed by 7268

Abstract

The new energy revolution, of which the primary energy will be based on renewable energy sources and the terminal energy will be based on electric power, will have a revolutionary impact on the future power grids. In order to develop the corresponding power [...] Read more.

The new energy revolution, of which the primary energy will be based on renewable energy sources and the terminal energy will be based on electric power, will have a revolutionary impact on the future power grids. In order to develop the corresponding power grid for the future energy system, first of all, the architecture and mode of operation of the future power grid must be investigated. In this paper, we suggest that the DC—dominant operation mode for transmission system, distribution network and distributed power system should be developed, and a MP-MC dominated transmission architecture (multiple powers to multiple consumers) and the two-way power exchange control (TPEC) should be employed to build “wide-area super virtual power plants” (WASVPPs) which cover all the major power plants in a wide range, allowing the consumers to obtain a stable and reliable supply of electricity from the “cloud powering” created by WASVPP and the distributed power system which is connected to the grid. Full article

(This article belongs to the Special Issue Future Grid)

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15 pages, 1068 KB

Open AccessArticle

Towards an Analysis of Daylighting Simulation Software

by Ignacio Acosta, Jaime Navarro and Juan J. Sendra

Energies 2011, 4(7), 1010-1024; https://doi.org/10.3390/en4071010 - 29 Jun 2011

Cited by 35 | Viewed by 8845

Abstract

The aim of this article was to assess some of the main lighting software programs habitually used in architecture, subjecting them to a series of trials and analyzing the light distribution obtained in situations with different orientations, dates and geometry. The analysis [...] Read more.

The aim of this article was to assess some of the main lighting software programs habitually used in architecture, subjecting them to a series of trials and analyzing the light distribution obtained in situations with different orientations, dates and geometry. The analysis examines Lightscape 3.2, Desktop Radiance 2.0, Lumen Micro 7.5, Ecotect 5.5 and Dialux 4.4. Full article

(This article belongs to the Special Issue Energy Savings in the Domestic and Tertiary Sectors)

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Energies, Volume 4, Issue 7 (July 2011) – 7 articles , Pages 1010-1111

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