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  • Numerical Analysis of Wood Biomass Packing Factor in a Fixed-bed Gasification Process
    Renew. Energy (IF 4.357) Pub Date : 2018-01-18
    William A. González, Juan F. Pérez, Sergio Chapela, Jacobo Porteiro

    The biomass gasification process in fixed bed was studied by means of computational fluid dynamics (CFD) numerical analysis. The aim was to evaluate the effect of the biomass packing factor on the thermochemical process. The fuel-wood used was Jacaranda Copaia in various shapes: chips, cylinders, and cubes with packing factors (PF) of 0.38, 0.48, and 0.59, respectively. The mathematical model is a transient 2D CFD model, which was developed through the implementation of User Defined Functions in ANSYS-Fluent. The model was extended to simulate the gasification process by expanding the chemical kinetic mechanism and by adapting the stages of pyrolysis, oxidation, and reduction. The model was validated with experimental data. The average relative error between experimental and numerical data was 5.45%. By means of the sensitivity analysis, it was found that with an increase in the packing factor from 0.38 to 0.59, the absorption of radiative heat transfer increases by 27% leading to increase the solid temperature in the reaction front, but due to a lower penetration of radiation, the drying and pyrolysis reaction rates decrease. But nevertheless, the higher solid temperature with packing factor favors the convective solid-gas heat transfer in the drying stage.

    更新日期:2018-01-19
  • Optimization of adsorption isotherm types for desiccant air-conditioning applications
    Renew. Energy (IF 4.357) Pub Date : 2018-01-18
    Muhammad Sultan, Takahiko Miyazaki, Shigeru Koyama

    The present study investigates five kinds of adsorbents for desiccant air-conditioning (DAC) applications. Each adsorbent yield distinctive water vapor adsorption isotherm that can be categorized as type-I, type-II, type-III, type-V, and type-linear on the basis of the International Union of Pure and Applied Chemistry (IUPAC) classification. Ideal DAC cycle is evaluated for the air-conditioning (AC) applications, and steady-state moisture cycled (MCSS) is estimated by means of adsorption isobars. Results showed that the adsorbent enabling type-linear adsorption isotherm gives maximum MCSS for industrial AC processes of matches manufacturing/drying/storage, rubber dipped goods storage and photo studio drying room. However, adsorbent enabling type-V adsorption isotherm is found the optimum adsorbent for tobacco stemming/stripping/softening and optical lenses grinding. For industrial AC process of dipped surgical articles; adsorbents enabling type-II, type-linear, and type-I adsorption isotherms are found the optimum choice at low (<68 °C), medium (68°C-87 °C), and high (>87 °C) regeneration temperatures, respectively.

    更新日期:2018-01-18
  • Integrated Hybrid Solar Drying System and its Drying Kinetics of Chamomile
    Renew. Energy (IF 4.357) Pub Date : 2018-01-18
    Baher M.A. Amer, Klaus Gottschalk, M.A. Hossain

    An integrated solar system was examined and worked for drying chamomile during the summer season 2013 in Germany. The system consisted of collector, heat exchanger, reflector, main drying chamber below collector, additional drying chamber and supplementary electric heaters immersed in water tank. It could also storage of solar energy into water during the time of sun-shine and reuse this energy at cloudy weather or off sunshine time to raise the temperature of drying air inside the system. The capacity of main drying chamber ranged 32-35 kg of fresh chamomile and 10-12 kg for the other separate drying chamber. Air temperature inside the dryer could be maintained as desired range for drying chamomile using a temperature controller. The integrated dryer was operated about 30 to 33 hours to reduce the moisture contents of chamomile from 72-75% to 6% (wb) compared to 60 hours to reduce it to 9-10% (wb) using open sun drying method. Nine mathematical models for drying kinetics of chamomile were tested to determine the parameters of the best suitable models for those plants. It is found Midili model was the best model to define drying kinetics of chamomile for the main and additional drying chambers in solar system.

    更新日期:2018-01-18
  • Water emulsified hybrid pongamia biodiesel as a modified fuel for the experimental analysis of performance, combustion and emission characteristics of a direct injection diesel engine
    Renew. Energy (IF 4.357) Pub Date : 2018-01-18
    Varatharaju Perumal, M. Ilangkumaran

    Biodiesel is widely accepted as substitute fuel for diesel engine by scientist, engineers and researchers for its superior fuel quality compared to diesel in terms of emission. The environmental and social benefits got from biodiesel attract almost all section of people. The use of biodiesel in diesel engine reduces the green house gases like CO, HC and PM emission considerably, but the smoke and NOx emissions are high compare to diesel. In order to reduce the smoke and NOx emissions caused by biodiesel in diesel engine, an experimental study was conducted by using water emulsified pongamia biodiesel in a four stroke direct injection diesel engine. The result revealed 9% increase in BSFC and 5% decrease in BTE with a reduction of around 32% in NOx emission. The smoke has been reduced to 7.4%, the emission of CO and HC has been reduced to a marginal value of 2.3% and 1% respectively compared with that of B20 blend.

    更新日期:2018-01-18
  • Optimal Sizing of PV/wind/diesel hybrid microgrid system using multi-objective self-adaptive differential evolution algorithm
    Renew. Energy (IF 4.357) Pub Date : 2018-01-18
    Makbul A.M. Ramli, H.R.E.H. Bouchekara, Abdulsalam S. Alghamdi

    Microgrid systems, such as solar photovoltaic power (PV) and wind energy, integrated with diesel generators are promising energy supplies and are economically feasible for current and future use in relation to increased demands for energy and depletion of conventional sources. It is thus important to optimize the size of hybrid microgrid system (HMS) components, including storage, to determine system cost and reliability. In this paper, optimal sizing of a PV/wind/diesel HMS with battery storage is conducted using the Multi-Objective Self-Adaptive Differential Evolution (MOSaDE) algorithm for the city of Yanbu, Saudi Arabia. Using the multi-objective optimization approach, the objectives are treated simultaneously and independently, thereby leading to a reduction in computational time. One of the main criteria to consider when designing and optimizing the HMS is the energy management strategy, which is required to coordinate the different units comprising the HMS. The multi-objective optimization approach is then used to analyze the Loss of Power Supply Probability (LPSP), the Cost of Electricity (COE), and the Renewable Factor (RF) in relation to HMS cost and reliability and is tested using three case studies involving differing house numbers. Results verify its application in optimizing the HMS and in its practical implementation. In addition, optimization results using the proposed approach provided a set of design solutions for the HMS, which will assist researchers and practitioners in selecting the optimal HMS configuration. Moreover, it is important to select optimally sized HMS components to ensure that all load demands are met at the minimum energy cost and high reliability.

    更新日期:2018-01-18
  • Experimental study of a designed solar parabolic trough with large rim angle
    Renew. Energy (IF 4.357) Pub Date : 2018-01-17
    Djelloul Azzouzi, Houssam eddine Bourorga, Khathir abdelrahim Belainine, Boussad Boumeddane

    In this paper, the design process steps of a conventional solar parabolic trough with large rim angle are presented. The various parameters which intervene to obtain the suitable parabolic trough form of the concentrator are applied. Through an experimental characterization, the real focal distance and the focal zone size of the designed concentrator have been determined and compared with those calculated theoretically. Then, its concentration ratio is evaluated and the focused solar flux at the focal zone along the absorber tube is calculated using Soltrace code. It should be noted that the wind speed effect was not taken into account in the experimental tests which are conducted under a solar irradiation of 970 W/m2 and a receiver inclination angle of 36° which corresponds to the experimentation site latitude.

    更新日期:2018-01-17
  • Experimental investigation of physicochemical properties of diesel, biodiesel and TBK-biodiesel fuels and combustion and emission analysis in CI internal combustion engine
    Renew. Energy (IF 4.357) Pub Date : 2018-01-17
    György Szabados, Ákos Bereczky

    Nowadays, there is a lot of research done with renewable diesel fuels. The number of parent materials (especially sludge oil, used oil, edible and non-edible oils), production technologies, and additives of biodiesel is increasing. In our work a comprehensive comparison test series of three fuels (fossil diesel, conventional biodiesel (rapeseed oil methyl ester), and a new type of biodiesel (which is called Triglycerides of Modified Structure)) have been performed. Comparison tests have been conducted with respect to their physicochemical properties and their effect on the combustion and emission of a bus engine. Referring to the physicochemical properties, the tested biodiesel fulfil all the requirements of the EN (European Norm) 14214 standard, but the tested TBK (Thész-Boros-Király) doesn't fit some of the requirements of the EN standard. Based on the indicator and heat release results it can be established, that there is no significant, but a moderate improvement of the combustion process with bio fuels. As for the emission it can be stated, that bio fuels are advantageous as well, but the results are near to measurement accuracy, except smoke and opacity, which decreased in a high degree in case of the two tested bio fuel compared to the fossil one.

    更新日期:2018-01-17
  • Comparison of late PCCI combustion, performance and emissions of diesel engine for B20 and B100 fuels by KIVA-CHEMKIN coupling
    Renew. Energy (IF 4.357) Pub Date : 2018-01-17
    Alborz Zehni, Rahim Khoshbakhti Saray

    A numerical study is performed by KIVA-CHEMKIN code to compare the combustion, performance and emission characteristics of neat biodiesel (B100) and biodiesel blend including a mixture of 20% biodiesel and 80% diesel (B20) resulting from the PCCI combustion mode in a light-duty diesel engine. For the biodiesel reaction mechanism, multi-chemistry surrogate mechanism using methyl decanoate (MD) and methyl-9-decenoate (MD9D) is used in this study. The results show that PCCI combustion like high temperature conventional combustion cannot cover the lower ISFC of the biodiesel blend fuel compared to the diesel fuel. A detailed analysis of combustion and emissions, involving the role of formaldehyde (CH2O) and hydroxyl (OH) radicals as well as O and H radicals, was performed in the PCCI combustion stages and emissions formation for the B100 and B20 fuels. The results indicate that higher concentration of formaldehyde as well as lower concentration of hydroxyl radicals for the B20 case advances low temperature heat release (LTHR) and retards high temperature heat release (HTHR) respectively compared to the B100 case. In addition, O and OH radicals as well as cylinder temperature are effective parameters regarding higher NO and CO concentrations for the B20 case compared to the B100 case.

    更新日期:2018-01-17
  • Dynamic modeling of vortex induced vibration wind turbines
    Renew. Energy (IF 4.357) Pub Date : 2018-01-16
    A. Chizfahm, E. Azadi Yazdi, M. Eghtesad
    更新日期:2018-01-17
  • Catalytic gasification characteristics of cellulose, hemicellulose and lignin
    Renew. Energy (IF 4.357) Pub Date : 2018-01-16
    Haimiao Yu, Zilu Wu, Geng Chen

    In this paper, catalytic gasification experiments of three major biomass components (cellulose, hemicellulose, and lignin), straw, and pine were performed with dolomite and Na2CO3 as catalysts on a small-scale entrained-flow gasifier. We focused on the differences of catalytic gasification characteristics among three major biomass components. Sodium carbonate and dolomite largely positively promoted hemicellulose gasification, significantly improved the gasification efficiency, calorific value of gas, and carbon conversion, and significantly reduced the tar yield. Sodium carbonate showed the optimal catalytic effect. Dolomite positively catalyzed the gasification of cellulose, hemicellulose, lignin, straw, and pine. Sodium carbonate significantly catalyzed the gasification of hemicellulose, but it inhibited the gasification of cellulose, lignin, straw, and pine. Sodium carbonate is suitable to catalyze the gasification of biomass with a high content of hemicellulose. The influences of different catalysts on the catalytic gasification characteristics of cellulose, hemicellulose and lignin were different. Therefore, the selection of biomass gasification catalyst should be based on the components and properties of biomass.

    更新日期:2018-01-17
  • Heat Recovery from Multiple-Fracture Enhanced Geothermal Systems: The Effect of Thermoelastic Fracture Interactions
    Renew. Energy (IF 4.357) Pub Date : 2018-01-16
    Hedda Slatlem Vik, Saeed Salimzadeh, Hamidreza M. Nick
    更新日期:2018-01-17
  • Utilization of de-oiled algal biomass for enhancing vehicular quality biodiesel production from Chlorella sp. in mixotrophic cultivation systems
    Renew. Energy (IF 4.357) Pub Date : 2018-01-16
    Richa Katiyar, Randhir K. Bharti, B.R. Gurjar, Amit Kumar, Shalini Biswas, Vikas Pruthi
    更新日期:2018-01-17
  • Evaluation of classification methods according to solar radiation features from the viewpoint of the production of Parabolic Trough CSP plants
    Renew. Energy (IF 4.357) Pub Date : 2018-01-16
    S. Moreno-Tejera, M.A. Silva-Pérez, L. Ramírez-Santigosa, I. Lillo-Bravo

    In this work, the representativeness of the day-types classified according to the solar radiation features by two classification methods is evaluated from the perspective of the production of two parabolic trough plants. A new methodology to characterize the representativeness of the day-types using a novel index is proposed, based on the characterization of the daily production. As a previous step to the use of a classification method, the evaluation methodology helps to select the most adequate model and to improve it from the perspective of a concentrated solar power project. This methodology is applied to 16 years of measurements from Seville (Spain) classified by two methods: a method based on daily clearness index values (kt), and a method that uses clustering techniques to define the day-types. From the application of the methodology to the clustering classification some improvements are identified and applied. As a result, from the 10 day-types identified by the clustering classification method a new classification based on 8 day-types with different features for each type of plant is proposed. The use of this classification to estimate the daily yield outperforms the results obtained with the kt classification, with a mean yearly RMSE value more than 20 % lower.

    更新日期:2018-01-17
  • The integration of Semi-transparent photovoltaics on greenhouse roof for energy and plant production
    Renew. Energy (IF 4.357) Pub Date : 2018-01-16
    Reda Hassanien Emam Hassanien, Ming Li, Fang Yin

    The aim of this study was to investigate the effect of semi-transparent building integrated photovoltaics (BIPV) mounted on top of a greenhouse, on the growth of tomatoes and microclimate conditions as well as to estimate the generated energy and the payback period of this system. Three modules were settled at 20 % of the greenhouse roof area at a tilt angle of 30º facing south at a distance of 0.08 m between the plastic cover and the BIPV. Each module has a peak power of 170 Wp and efficiency of 8.25 %. Results revealed that the annual generated electric energy of the BIPV was 637 kWh. Furthermore, there were no significant differences (P< 0.05) in the growth of tomatoes between shaded greenhouse by the BIPV and the un-shaded greenhouse. The reduction of solar radiation under the BIPV was 35 % - 40 % more than the Polyethylene covers on clear days. The BIPV shading decreases the air temperature by (1 ºC - 3 ºC) on clear days and has no effect on relative humidity. The payback period was found to be 9 years. Moreover, this system can provide most of the annual energy demands for the greenhouse environmental control systems.

    更新日期:2018-01-17
  • High efficiency design of an impulse turbine used in oscillating water column to harvest wave energy
    Renew. Energy (IF 4.357) Pub Date : 2018-01-12
    Rameez Badhurshah, Prasad Dudhgaonkar, Purnima Jalihal, Abdus Samad

    Wave energy harvesting systems mostly have low power production capability because of unoptimized design of the system components. A bidirectional flow impulse-turbine used in such a system has efficiency less than 40%, and it is required to design the turbine for a higher efficiency. Present work finds an optimal design and shows design-variable sensitivity to the turbine efficiency. The problem is solved using numerical analysis technique. The flow through the turbine was analyzed by solving the Reynolds-averaged Navier-Stokes equations (RANSE). The design variables; namely number of rotor blades and number of guide vane, guide vane angle and guide vane profile were modified to maximize the turbine efficiency. Using the Latin hypercube sampling technique, sample points were selected from a design space defined by lower and upper limits of the variables. Then, several surrogates were constructed using the RANSE calculated results, and the turbine performance was optimized. The results show that guide vane angle is the most sensitive parameter, while the guide vane profile has negligible effect on efficiency. A hybrid genetic algorithm searched the optimal design point. The relative mean efficiency enhancement over a wide range of flow coefficient was approximately 24%, while it was 28% at maximum efficiency point.

    更新日期:2018-01-12
  • Application of extended vortex theory for blade element analysis of horizontal-axis wind turbines
    Renew. Energy (IF 4.357) Pub Date : 2018-01-12
    D.H. Wood

    Vortex theory is used in blade element analysis (BEA) of wind turbines to account for the finite number of blades, N, usually in terms of Prandtl's “tip loss function”, F. Wood et al. [1] calculated alternative “trailing vorticity functions” using helical vortex theory. F was found to be inaccurate over the entire blade at low tip speed ratio and in error near the hub at any tip speed ratio. Further, the trailing vorticity function is not constrained to be less than unity as is F. Wood & Okulov [2] analyzed the nonlinear terms in the streamtube equations for angular and axial momentum and found an accurate way of including these in BEA. This paper describes the use of the trailing vorticity functions, which can be different in the axial and azimuthal directions, in an otherwise standard blade element analyses. Comparison is made to wind tunnel tests of model rotors and to calculations using F. There is only a small difference in the calculated power and thrust coefficients. The present calculations show higher induced axial velocities in the tip and hub regions and it is suggested that the trailing vorticity functions can be used in situations where F cannot.

    更新日期:2018-01-12
  • Co-ensiling of cattle manure before biogas production: Effects of fermentation stimulants and inhibitors on biomass and methane preservation
    Renew. Energy (IF 4.357) Pub Date : 2018-01-12
    Rúben Teixeira Franco, Pierre Buffière, Rémy Bayard

    The impact of formic acid and glucose addition on the co-ensiling of cattle manure with straw was assessed during 4 months at laboratory scale. Feedstock deprived of additives lost 67% of its methane potential for prolonged ensiling. This was mainly due to the lack of water-soluble carbohydrates and to the high methanogenic activity of cattle manure. The use of co-substrates enhanced biomass and energy conservation during ensiling. The best result was obtained for co-ensiling of cattle manure with glucose (100 g/kg of feedstock). For this condition, lactate production was extensive, which enabled biomass acidification, suppressed ammonia emissions and led to full preservation of methane potential after 4 months. Therefore, in field-scale storage, co-ensiling with a sugar-rich co-substrate appears to be the most resourceful method to optimize cattle manure preservation. Application of this promising technique will have a major impact on the methane yield of agricultural biogas plants where cattle manure has to be stored for long periods.

    更新日期:2018-01-12
  • Clean vs. Green: Redefining renewable energy. Evidence from Latvia, Lithuania, and Romania
    Renew. Energy (IF 4.357) Pub Date : 2018-01-12
    Konstantinos P. Tsagarakis, Amaryllis Mavragani, Andrius Jurelionis, Iulia Prodan, Tugui Andrian, Diana Bajare, Aleksandrs Korjakins, Sarune Magelinskaite-Legkauskiene, Veres Razvan, Laura Stasiuliene

    As the role that the society plays in energy and use of resources is of importance, what is vital is early education, as it is one of the pillars significantly influencing the planning of a “cleaner future” energywise, especially through utilizing energy-specific education techniques. Up to this point, it has been suggested that younger students tend to describe Renewable Energy Sources (RES) as ‘Clean’ rather than ‘Green’, while their selection in the color that best describes them is Yellow or White rather than Green. On the subject of redefining RES, a total of 1689 face-to-face surveys are conducted in schools in the Baltics and Eastern Europe countries, i.e. Latvia, Lithuania, and Romania, in order to further contribute on the discussion of which term -‘Clean Energy’ or ‘Green Energy’- is the term of choice for students of younger age with no or less formal education and experience on the subject of best naming RES. As far as the color to best represent RES is concerned, younger students tend to choose Yellow or White instead of Green, a choice that shifts to Green in higher grades. The results, with the exception of Lithuania where older students chose the term ‘Clean Energy’, confirm those of previous studies in Greece and Bulgaria, enhancing the importance of the elicitation of such preferences in order for energy issues to become part of the educational system of all levels. As Clean and Yellow or White are the terms of choice for naming and describing Renewable Energy Sources according to young students, it is imperative that the scientific community reconsiders and adjusts said preferences in education and research, for the better -future- implementation of renewable energy practices and use of resources.

    更新日期:2018-01-12
  • Biodiesel synthesis from Mesua ferrea oil using waste shell derived carbon catalyst
    Renew. Energy (IF 4.357) Pub Date : 2018-01-12
    Akash Pratim Bora, Sumit H. Dhawane, Kumar Anupam, Gopinath Halder

    The present study investigates the feasibility of synthesis of environmentally benign heterogeneous carbonaceous catalyst and biodiesel production from a single source i.e. Mesua ferrea Linn (MFL) seeds. The study primarily focuses on the optimisation of biodiesel synthesis process considering four parameters viz. reaction time, temperature, catalyst loading and methanol to oil ratio (M/O). The parametric influence on the free fatty acid (FFA) conversion has been studied to evaluate the most significant parameters. The contribution factor and analysis of variance results reveal that temperature is the most significant parameter influencing the FFA conversion followed by reaction time and catalyst content. The optimum conditions observed for maximum FFA conversion of 95.57% were: temperature 55 °C, time 2 h, catalyst content 10 wt% and M/O 6:1. The physico-chemical properties of the produced Mesua ferrea oil methyl ester (MFOME) were analysed following ASTM standard methods and found to be within limit; and compatible with the conventional diesel. Thus, the study suggests that the MFL seeds could be a promising source for the synthesis of an effective heterogeneous catalyst; and eco-friendly energy efficient sustainable fuel through the concept of green chemistry by converting waste into valuable commodity towards mitigation of increased energy demand.

    更新日期:2018-01-12
  • Melting enhancement of a latent heat storage with dispersed Cu, CuO and Al2O3 nanoparticles for solar thermal application
    Renew. Energy (IF 4.357) Pub Date : 2018-01-11
    Dawit Gudeta Gunjo, Smruti Ranjan Jena, Pinakeswar Mahanta, P.S. Robi

    The performance of all latent heat storage system depends on the quality of phase change material used. In the present study, paraffin-based nanofluid dispersed with 5% of Cu, 5% of CuO and 5% of Al2O3 nanoparticles are used to investigate its effect on the storage characteristics. A 3-D numerical model of a shell and tube regenerative type latent heat storage is developed using®COMSOL Multiphysics 4.3a to predict the average temperature and melt fraction of paraffin-based nanofluid. The validation with the established pieces of literature and experiments indicated a sound agreement. The effect of adding nanoparticles on melting/solidification rate and energy storing/releasing rate are also studied. The result revealed that addition of 5% of Cu, 5% of Al2O3 and 5% of CuO nanoparticles improved the melting rate by 10 times, 3.46 times and 2.25 times and the discharged rate by 8 times, 3 times and 1.7 times, respectively compared to the pure paraffin filled latent heat storage system. However, it decreased the specific heat and heat of fusion which reduced the sensible and latent heat storing capacity. Additionally, orientations of cylinder and tube arrangement are also studied numerically using paraffin as phase change material.

    更新日期:2018-01-12
  • Sugarcane can afford a cleaner energy profile in Latin America & Caribbean
    Renew. Energy (IF 4.357) Pub Date : 2018-01-10
    Simone Pereira Souza, Luiz Augusto Horta Nogueira, Johan Martinez, Luís A.B. Cortez

    Latin American and Caribbean's (LAC) external dependency on fossil fuels and the pursuit for renewable energy leads to the need for a strategy to afford a cleaner and reliable domestic energy supply. Sugarcane presents high photosynthetic efficiency and it is a well-spread crop in LAC. Our study aims to explore the potential of different approaches of modern energy production from sugarcane, at a national level, and its implication to the environmental aspects. We found that Guatemala, Nicaragua and Cuba would be able to replace 10% of the gasoline and about 2–3% of the diesel consumption by only using the current molasses. With a slight expansion on sugarcane production, Bolivia can replace 20% of the gasoline and diesel, besides providing surplus ethanol for exportation or other purposes. With a minor investment, bagasse may enlarge the electricity access in many countries whereas in other may represent an alternative to replace fossil fuel sources. We also found relevant potential on reducing the GHG emissions specially in Bolivia, Paraguay and Nicaragua. However, the implementation of such strategies must be supported by appropriate policies to ensure competitive prices, overcome opportunity costs, and stimulate investments.

    更新日期:2018-01-11
  • Feasibility of WEC installations for domestic and public electrical supplies: A case study off the Calabrian coast
    Renew. Energy (IF 4.357) Pub Date : 2018-01-10
    Francesco Aristodemo, Danilo Algieri Ferraro

    This paper presents a performance evaluation of Wave Energy Converters (WECs) in terms of electricity production for domestic and public supplies of coastal towns located near hot spot areas. The study was conducted off the coast of Calabria (Southern Italy), a Mediterranean region characterized by a mild wave climate which is quite representative of mean sea states in the Mediterranean basin. The wave energy potential was assessed in deep waters by means of ECMWF wave data validated against RON buoys and UKMO data. Thirteen types of offshore WECs were considered, comparing the performances of full-scale and downscaled devices in terms of yearly and seasonal mean electricity production and operating days. Based on the domestic electricity supplies and those related to the public plants of some selected coastal cities, the number of differently sized devices was calculated in order to satisfy the above needs. To preserve the wave energy production level, the spatial arrangement of wave energy farms was determined in order to minimize possible park effects. The obtained results highlight that the occurrence of offshore WEC farms in a typical Mediterranean zone can lead to a significant number of WECs for domestic and public electricity supplies with a progressive reduction for more energetic sites.

    更新日期:2018-01-11
  • In-vessel co-composting of biosolid: Focusing on mitigation of greenhouse gases emissions and nutrients conservation
    Renew. Energy (IF 4.357) Pub Date : 2017-02-24
    Mukesh Kumar Awasthi, Quan Wang, Hongyu Chen, Meijing Wang, Sanjeev Kumar Awasthi, Xiuna Ren, Hanzhen Cai, Ronghua Li, Zengqiang Zhang

    In this paper study the feasibility of Calcium-bentonite (Ca-B) combined with biochar (B) as an effective amendment for the co-composting of dewatered fresh sewage sludge (DFSS) mixed with wheat straw (WS), focusing on mitigation of greenhouse gases (GHG) emission and nutrients loss. The 12%B mixed with three different concentration of Ca-B (2%, 4% and 10%) was supplemented into 1:1 ratio mixture of DFSS and WS (dry weight basis), while compared with a 12%B alone and control or without any amended treatments. This experiment lasted for 42 days in a 130-L reactor. The CH4 and N2O emission profiles were clearly indicated that 12%B alone and 12%B + Ca-B addition effectively buffered the composting mass and enhanced the rate of organic matter mineralization as compared to control treatment. Among the all treatments, minimum TOC (16.83%), TKN (0.38%) and dry matter (29.73%) losses were observed in 12%B+4%Ca-B applied treatment; and also improved compost quality compared to control. Furthermore, 12%B+4%Ca-B amendment was beneficial to the efficient organic matter degradation and low quantity of total GHG production from the feedstock without inhibition to composting compared with control treatment. Therefore, 12%B+4%Ca-B amendment is a promising ecofriendly solution for DFSS co-composting because it contributes to reduce the total GHG emission and produced matured compost with sound management of DFSS in China.

    更新日期:2018-01-10
  • Feasible use of microbial fuel cells for pollution treatment
    Renew. Energy (IF 4.357) Pub Date : 2017-02-04
    Jianjun Hu, Quanguo Zhang, Duu-Jong Lee, Huu Hao Ngo

    The microbial fuel cells (MFC) can directly transform chemical energy in feed substance to electricity by anodic aspiration pathways. This mini review provides an order-of-magnitude argument that MFC has much lower catalyst density at electrode surface and much higher diffusional resistance for substrates than the chemical fuel cell, the former should not be used as an energy generation unit; rather, it should be applied in low power density level applications such as biofilm wastewater treatment. The literature studies using MFC for pollution treatment are discussed.

    更新日期:2018-01-10
  • Pentose rich acid pretreated liquor as co-substrate for 1,3-propanediol production
    Renew. Energy (IF 4.357) Pub Date : 2017-01-30
    Narisetty Vivek, Meera Christopher, M. Kiran Kumar, Eulogio Castro, Parameswaran Binod, Ashok Pandey

    Lignocellulosic biomass is considered to be a potential raw material for production of renewable fuels like bioethanol and biodiesel. Cellulose and hemicelluloses constitute major portion of the lignocellulosic biomass. Cellulose can be converted to glucose by hydrolysis and subsequently to ethanol by fermentation. The hemicellulosic portion mostly contains pentose sugars which cannot be utilized by many microorganisms for ethanol production. Acid pretreatment results in separation of a pentose-rich fraction which can be utilized for the production of various high value chemicals. The present study evaluates the utilization of pentose sugars as co-substrate, along with biodiesel industry-generated crude glycerol, for the production of 1,3-propanediol (1,3-PDO). Bioconversion of these low value byproducts into a high value chemical would be an economically advantageous strategy in terms of waste disposal for biorefineries. In this study, the production of 1,3-propanediol from the acid pretreated liquor obtained from rice straw was evaluated using Klebsiella pneumonia. Different carbon sources like pure hexose and pentose sugars, mixed pentose sugar containing acid pretreated liquor (APL) from rice straw and different concentrations of pentose sugars and acid pretreated liquor were evaluated. There is 65% increase in titers from 9.55 g/L to 15.75 g/L using APL as co-substrate. With addition of 0.5% (v/v) APL, 1,3-propanediol production reached 20.88 g/L with 0.69 g/g yield and 0.87 g/L/h productivity. The study comprehensively explains the behavior of Klebsiella pneumoniae strain utilizing pentose rich APL and crude glycerol which enroute to an integrated biorefinery approach.

    更新日期:2018-01-10
  • Water/MWCNT nanofluid based cooling system of PVT: Experimental and numerical research
    Renew. Energy (IF 4.357) Pub Date : 2018-01-08
    R. Nasrin, N.A. Rahim, H. Fayaz, M. Hasanuzzaman

    In this research, an indoor experiment has been carried out of a PV module under controlled operating conditions and parameters. A novel design of thermal collector has been introduced, a complete PVT system assembled and water/MWCNT nanofluid used to enhance the thermal performance of PVT. An active cooling for PVT system has been maintained by using a centrifugal pump and a radiator have been used in the cycle to dissipate the heat of nanofluid in the environment to maintain proposed inlet temperature. 3D numerical simulation has been conducted with FEM based software COMSOL Multiphysics and validated by an indoor experimental research at different irradiation level from 200 to 1000 W/m2, weight fraction from 0 to 1% while keeping mass flow rate 0.5 L/min and inlet temperature 32 °C. The numerical results show a positive response to the experimental measurements. In experimental case, percentage of enhanced PV performance is found as 9.2% by using water cooling system. Higher thermal performance is obtained as approximately 4 and 3.67% in numerical and experimental studies, respectively by using nanofluid than water. In the PVT system operated by nanofluid at 1000 W/m2 irradiation, the numerical and experimental overall efficiency are found to be 89.2 and 87.65% respectively.

    更新日期:2018-01-08
  • Heat transfer analysis of PV integrated modified greenhouse dryer
    Renew. Energy (IF 4.357) Pub Date : 2018-01-06
    Prashant Singh Chauhan, Anil Kumar, Chayut Nuntadusit

    A PV integrated greenhouse dryer has been fabricated with a unique solar collector and tested in no-load condition under forced convection mode. Various important thermal performance indicators such as heat utilisation factors, convective heat transfer coefficient, coefficient of performance and percentage of net heat gain have been evaluated to validate the effectiveness of modifications. Energy, electrical and exergy efficiencies have been also analysed for installed PV system for exhaust fan. Greenhouse dryer experiments have been conducted for with and without solar collector conditions. The enhancement in the highest convective heat transfer coefficient for the greenhouse dryer with solar collector condition is 150% in comparison to the absence of solar collector. Heat utilisation factor and coefficient of performance are found 10.1% and 7.9%, respectively, higher than greenhouse dryer without solar collector. The maximum energy and exergy efficiencies are found 16.8% and 21.4% for greenhouse dryer with and without solar collector, respectively. These results represent the effectiveness of solar collector placed inside the dryer and insulated north wall. The designed greenhouse dryer with solar collector is proposed as most suitable dryer for crop drying in the temperature range of 40–70 °C.

    更新日期:2018-01-06
  • Application of heliostat in interior sunlight illumination for large buildings
    Renew. Energy (IF 4.357) Pub Date : 2018-01-05
    Jifeng Song, Geng Luo, Lei Li, Kai Tong, Yongping Yang, Jin Zhao

    Heliostat daylighting systems, used to transmit sunlight deep into rooms where natural light cannot reach, are increasingly applied in buildings. A roof-mounted heliostat with an area of 22.95 m2 was developed in this work to verify the feasibility of high flux and long distance daylighting in large building interior. The developed heliostat system consists of a heliostat, a secondary reflector, and glass windows forming the light path within the building. The problem of gravitational deformation of the steel beams base of the heliostat was solved by a rectification algorithm embedded into the computer program, to realize vertical daylighting. The spectrum and chromaticity of the heliostat daylighting system developed was measured, and the results verify the good visual quality of the interior illumination. The light transmission distance is more than 70 m, and the system can provide a level of 20-80 klux daylighting illuminance in the daytime. An economic analysis was carried out, and data indicates a good cost-effectiveness of the heliostat daylighting system developed. It is hoped that this research will be of some reference value to the design of heliostat daylighting systems in large buildings.

    更新日期:2018-01-05
  • 更新日期:2018-01-05
  • Carbon nanotube nanofluid in enhancing the efficiency of evacuated tube solar collector
    Renew. Energy (IF 4.357) Pub Date : 2018-01-04
    I.M. Mahbubul, Mohammed Mumtaz A. Khan, Nasiru I. Ibrahim, Hafiz Muhammad Ali, Fahad A. Al-Sulaiman, R. Saidur
    更新日期:2018-01-05
  • A methodology to determine the optimal size of a wells turbine in an oscillating water column device by using coupled hydro-aerodynamic models
    Renew. Energy (IF 4.357) Pub Date : 2018-01-04
    Fernando R. Torres, Paulo R.F. Teixeira, Eric Didier

    This paper describes a methodology to determine the optimal size of a Wells turbine to be used in an OWC device taking into account hydro-aerodynamic coupling, performance curves of the turbine and air pressure control by a relief valve. The proposed model, named turbine diameter optimization (TDO) model, considers the movement of the water surface inside the OWC chamber as a piston movement in response to the hydrodynamic forces from the incoming waves. The aerodynamic is based on the first law of thermodynamics applied to the air column of the chamber. The power-pressure curve of the turbine and the air pressure control by relief valve are implemented in the model to determine the turbine power output for several regular incident waves. The TDO model is initially calibrated by a numerical model based on Reynolds-Average-Navier-Stokes (RANS) equations for each wave component of an expected sea state distribution. Thereafter, the power output generated by turbines of several sizes is calculated with lower computational cost (few minutes) in comparison with RANS based models (thousands of hours) in a personal computer. This developed methodology is an important support to the process of turbine sizing for an OWC device for an expected sea state distribution.

    更新日期:2018-01-05
  • Geographic Maps of the Impact of Government Incentives on the Economic Viability of Solar Power
    Renew. Energy (IF 4.357) Pub Date : 2018-01-04
    Hillary MacDougall, Steve Tomosk, David Wright
    更新日期:2018-01-04
  • Assessing the growth of residential PV exports with energy efficiency and the opportunity for local generation network credits
    Renew. Energy (IF 4.357) Pub Date : 2018-01-04
    Sebastian Oliva H

    An unprecedented expansion of household photovoltaic (PV) systems coincided with a marked decline in household electricity demand in several jurisdictions around the world. This was driven by falling PV prices and the installation of more energy efficient residential appliances (EE). However, existing net metering arrangements value self-consumption of PV far more than PV exports to the grid. As a result, energy savings from EE that considerably reduce household PV self-consumption could also reduce the value of PV systems. Since PV exports generally utilise only part of the distribution grid, ‘local generation network credits’ (LGNCs) have been proposed to increase the value of PV exports. LGNCs also have the potential to improve the combined value of PV and EE. Given the large variability of the household PV generation and load and the time-varying structure of LGNCs, an empirical probabilistic method is proposed in this paper in order to assess the combined PV-EE value with the LGNC arrangements. The results show how simplistic feed-in tariffs have an adverse impact on the combined PV-EE value and how LGNCs can assist in removing barriers to the combined uptake of these two key clean energy technologies.

    更新日期:2018-01-04
  • Low cost realisation of a high temperature solar cooker.
    Renew. Energy (IF 4.357) Pub Date : 2018-01-04
    Ian Edmonds

    This paper describes a low cost solar cooker for high temperature, traditional pan style, cooking. A non-imaging concentrator comprised of eight flat reflective panels is linked via a cylindrical light guide to a cooking pan that sits at convenient height in a reflective cooking enclosure to minimise radiant and convective losses. The cooker can be manually tracked in azimuth and in altitude. Low temperature cooking and water sterilisation can be achieved in conventional cooking pans. High temperature cooking is achieved by modifying the base of a conventional cooking pan to be either solar selective or windowed with a transparent glazing. The solar cooker is inexpensive to fabricate and simple and safe to use.

    更新日期:2018-01-04
  • Maximum power output and parametric choice criteria of a thermophotovoltaic cell driven by automobile exhaust
    Renew. Energy (IF 4.357) Pub Date : 2018-01-04
    Zhimin Yang, Yanchao Zhang, Qingchun Dong, Jian Lin, Guoxing Lin, Jincan Chen

    An unreported model of the cylindrical thermophotovoltaic cell (TPVC) composed of an emitter and a photovoltaic (PV) cell is proposed and used to recycle the waste heat released by the automobile exhaust pipe to generate electricity. To theoretically analyze the performance of this system, expressions of the power output and the conversion efficiency of the thermophotovoltaic cell driven by the automobile exhaust are derived analytically. The optimal functions of the temperature distributions of the automobile exhaust pipe and TPVC are obtained by the variational method and the modified Lagrangian formulation. The maximum power output is calculated. The performance characteristics of the whole system at the maximum power output are represented. The optimal regions of the voltage output of the PV cell, the energy gap of the material in the PV cell, and the inlet heat flow of the gas pipe are determined. The effects of the size of the gas pipe on the performance of the TPVC are discussed. The theoretical efficiencies of the TPVC and thermoelectric generator driven by the automobile exhaust are compared. The advantages of the TPVC are revealed. The results obtained show that the optimally designed TPVC can significantly harvest the waste heat of the automobile exhaust.

    更新日期:2018-01-04
  • GHG avoided emissions and economic analysis by Power Generation Potential in Posture Aviaries in Brazil
    Renew. Energy (IF 4.357) Pub Date : 2018-01-03
    Eruin Martuscelli Ribeiro, Regina Mambeli Barros, Geraldo Lúcio Tiago Filho, Ivan Felipe Silva dos Santos, Luma Canobre Sampaio, Ticiane Vasco dos Santos, Fernando das Graças Braga da Silva, Ana Paula Moni Silva, João Victor Rocha de Freitas

    Intensification and mechanization of agricultural activities have brought numerous benefits, among which, is the increase in food production. However, waste generation from animal has also increased tremendously. Creation of laying hens in cage system produces many wastes, which must be removed daily. This is important for the cage and farm environmental protection; which should be properly managed to ensure public health protection. In the pursuit for effective management, by using experimental data of a chicken farm in Itanhandu-MG, Brazil, the possible production at national level, of electric energy by anaerobic digesters from dejections collected in laying hens cages. In the present study, the GHG emissions impacts assessment, by tCO2eq, in the COP21 from Paris 2015 context was evaluated using the Intergovernmental Panel on Climate Change (IPCC) methodology. For the economic viability of these wastes in energy generation, six scenarios of ten years were evaluated, all resulting from the combination between scenarios with and without funding, and with or without internal use of electrical power generated, but with real and presumed profit (in the framework of ANEEL no. 482/2012 and no.687/2015 resolutions) on micro-generation distribution. In all scenarios, energy was considered available to the Brazilian National Interconnected System (SIN), according to the 5th auction average price in 2015. The annual emissions avoided by methane burning and subsequent electricity generated was of 8.02 million of tCO2eq and 38.4 thousands of tCO2eq, respectively. Farms with more than 100,000 birds presented good probability in simulations of certainty, with regards to expected financial return. The most promising scenario was C6, tax modality of presumed profit, internal energy use, and sale of surplus energy (it would be also considered as credit on the next account), with financing of invested capital.

    更新日期:2018-01-04
  • Surface turbulence intensity as a predictor of extrapolated wind resource to the turbine hub height: method’s test at a mountain site
    Renew. Energy (IF 4.357) Pub Date : 2018-01-03
    Giovanni Gualtieri

    Following testing at the Cabauw (Netherlands) flat and inland site, and at the FINO3 offshore platform in the North Sea (Germany), the α–I wind resource extrapolating method was tested at the Boulder (CO, USA) mountain site (1855 m), another substantially different location in terms of surface characteristics, stability conditions, and wind energy pattern. Data from local 82-m M2 met mast between 10 and 80 m were used, with extrapolations to 50-m and 80-m turbine hub heights performed based on 10-m and 20-m turbulence intensity observations. Trained over a 2-year period (1997–1998), the method was validated on the year 1999.Slightly better results than those at both Cabauw and FINO3 were achieved in 50-m and 80-m wind speed extrapolations, with bias within 5%, NRMSE=0.17–0.23, and r=0.96–0.98. In predicting the annual energy yield, a bias within 1% was achieved at 50 m, which at worst increased to 6.44% at 80 m. The method was less stability-sensitive than at Cabauw and particularly FINO3. It proved to be reliable even over a mountain site affected by fairly complex terrain, which is noteworthy if considering the power law the method is based upon was actually developed for flat and homogeneous terrain.

    更新日期:2018-01-03
  • Institutional and Community Solar Cooking in India using SK-23 and Scheffler Solar Cookers: A Financial Appraisal
    Renew. Energy (IF 4.357) Pub Date : 2018-01-03
    Sunil Indora, Tara C. Kandpal

    Financial appraisal of two solar cookers (SK-23 and Scheffler dish) that may be used for institutional/community cooking is presented. For each solar cooker type, three different categories in terms of performance and cost as prevailing in the market have been considered. Annual numbers of solar cooked meals and consequently the values of several measures of financial performance are estimated for three locations in India with varying climatic conditions. As per the estimates obtained in this study a SK-23 solar cooker can cook from 39% to 60% of the meals during the year while, the corresponding range for Scheffler dish based solar cooker is from 59% to 85% at these locations. The discounted payback for SK-23 varies 6.2 to 9.2 years while the same for Scheffler dish varies from 9.5 to 11.7 years. The financial attractiveness of SK-23 is adversely affected by its poor performance in high wind, while the relatively higher capital cost of the Scheffler direct cooker apparently makes it financially unattractive. Thus, there is an urgent need to encourage research and development on solar cookers to reduce their cost and also to improve performance.

    更新日期:2018-01-03
  • Optimal network reconfiguration and renewable DGs integration considering time sequence variation of load and DGs
    Renew. Energy (IF 4.357) Pub Date : 2018-01-03
    Imen Ben Hamida, Saoussen Brini Salah, Fouzi Msahli, Mouhamed Faouzi Mimouni

    Several studies of distribution network enhancement focused only on the optimization of either the integration of distributed generations (DG) or network reconfiguration. However, very few researches have been done for distribution network reconfiguration simultaneously with the DG location and sizing. This paper presents a multi-objective management operations based on network reconfiguration in parallel with renewable DGs allocation and sizing for minimizing active power loss, annual operation costs (installation, maintenance, and active power loss costs) and pollutant gas emissions. The time sequence variation of wind speed, solar irradiation and load are taken into consideration. An efficient evolutionary technique based on the Pareto optimality is adopted to solve the problem. A fuzzy set theory is used to select the best compromise solution among obtained Pareto set. The obtained results prove the efficiency and the accuracy of the suggested method for the network manager to find the optimal network configuration simultaneously with DG location and sizing considering multiple criteria.

    更新日期:2018-01-03
  • Analysis of wind speed data and wind energy potential in Faya-Largeau, Chad, using Weibull distribution
    Renew. Energy (IF 4.357) Pub Date : 2018-01-03
    M.H. Soulouknga, S.Y. Doka, N Revanna, N Djongyang, T.C. Kofane

    In this work, we aimed at analyzing the wind speed of Faya-Largeau and making decisions of the cost effective wind turbine for the said zone. The characteristics of the wind speed and the energy potential of Faya-Largeau in the Saharan zone of Chad were studied using monthly wind speed data collected over eighteen years (1960-1978) and measured at 10 m height. In order to determine the wind power density and the available energy for the Faya-Largeau site in the Saharan zone of Chad, the Weibull probability density function was used. Thus, the annual values of the Weibull parameters k and c are respectively 3.75 and 3.60 (m/s), whereas the power density and available energy are respectively 343.31 W/m2 and 249.87 kWh/m2. Three commercial wind turbine models were used. Based on the capacity factor, the 1.MW/54 Bonus model is cost-effective for the Faya-Largeau site and could be strongly recommended for installation.

    更新日期:2018-01-03
  • A feedback control system with reference governor for a solar membrane distillation pilot facility
    Renew. Energy (IF 4.357) Pub Date : 2018-01-02
    Juan D. Gil, Lidia Roca, Guillermo Zaragoza, Manuel Berenguel

    This work presents the development of a feedback control system for a pilot membrane distillation facility powered with solar energy located at Plataforma Solar de Almería (PSA), Spain. The control system allows to fix a suitable operating temperature at the inlet of the distillation system, improving the operation quality. Four direct control schemes based on Proportional Integral (PI) controllers and Feedforward (FF) are designed as well as a reference governor which generates temperature references for the heat generation circuit direct control layer. Simulations and experimental tests are shown to demonstrate the effectiveness of the proposed scheme.

    更新日期:2018-01-03
  • Control-oriented modeling of geothermal borefield thermal dynamics through Hammerstein-Wiener models
    Renew. Energy (IF 4.357) Pub Date : 2018-01-02
    Ercan Atam, Daniel Otto Schulte, Alessia Arteconi, Ingo Sass, Lieve Helsen

    Geothermal energy is considered a clean and sustainable form of renewable energy, that can be exploited directly or indirectly by means of specific devices. Ground-coupled heat pumps are widely used systems to obtain this energy. Control of ground-coupled heat pump systems, where thermal energy is extracted or injected from and to a geothermal borefield, is important for optimal geothermal energy use in the building sector and smart grids. Model-based control of such systems is potentially an optimal solution but this requires control-oriented models for the borefield thermal dynamics, which is quite complicated due to thermal interactions between the boreholes, large-scale nonlinear system dynamics, transient surface boundary conditions, etc. In this paper, we propose and demonstrate the successful identification of these complex dynamics through simple and well-structured nonlinear Hammerstein-Wiener models, which can be used in some advanced convex model-based control algorithms. The results are validated for different borefield configurations and parameters with reference to a detailed finite-element borefield thermal model. Finally, a set of advanced convex model-based control methods are shortly described where Hammerstein- Wiener models can be used as control models.

    更新日期:2018-01-02
  • Supercritical ethanolysis of wheat stalk over calcium oxide
    Renew. Energy (IF 4.357) Pub Date : 2017-12-30
    Wei-Gang Li, Wei Zhao, Hao-Miao Liu, Lei Ao, Kai-Shuai Liu, Yin-Shuang Guan, Shi-Feng Zai, Shang-Long Chen, Zhi-Min Zong, Xian-Yong Wei

    Catalysts C600, C700, and C800 prepared from Ca(CH3COO)2 calcination at 600, 700, and 800 °C, respectively, were characterized with an X-ray diffractometer, scanning electron microscope, and specific surface area analyzer. Over the catalysts, bio-oils (BOs) were obtained by the supercritical ethanolysis (SCE) of wheat stalk powder (WSP). Their yields, ultimate analyses, chemical composition and some fuel properties were investigated. WSP and the residues from the SCE of WSP were analyzed with a Fourier transform infrared spectrometer. The results show that C700 has a small particle size and large specific surface area, and can effectively catalyze the SCE of WSP. The BO yields from non-catalytic, C600 single bond , C700 single bond , and C800-catalyzed SCE of WSP ae 30.1, 22.9, 70.7 and 34.4%, respectively. BO700 from C700-catalyzed SCE of WSP has relatively higher H/C and H/O ratios and calorific value but lower acidity, kinematic viscosity, and water content. The relative content of alcohols in the BO obviously increased, while the contents of carboxylic acids, ethyl esters, and anhydrides decreased over C700.

    更新日期:2017-12-31
  • Role of multiple solar heaters along the walls for the thermal management during natural convection in square and triangular cavities
    Renew. Energy (IF 4.357) Pub Date : 2017-12-30
    Debayan Das, Leo Lukose, Tanmay Basak

    The role of multiple discrete solar heaters have been studied for energy efficiency in the heating of fluids. Current work involves natural convection studies with the various locations of the double heat sources along each side wall of the triangular-design 1 (regular isosceles triangle), triangular-design 2 (inverted isosceles triangle) and square enclosures for various cases (case 1: larger heater in lower half and smaller heater in central half, case 2: larger heater in central half and smaller heater in lower half, case 3: two heaters of identical lengths are located at the central and lower halves) involving various fluids (Pr=0.015 P r = 0.015 and 7.2) for various Rayleigh numbers, 103≤Ra≤105 10 3 ≤ R a ≤ 10 5 . The thermal mixing and energy flow in the cavities are visualized using the mathematical tool of heatlines. Also, the overall rate of heat transfer in conduction and convection dominant regimes is evaluated using Nusselt numbers (average and local). The case 2 discrete heating configuration is inferred as the optimal heating configuration based on the larger zone of uniform temperature and thermal mixing. Also, the thermal management is significantly improved in triangular-design 2 and square cavities.

    更新日期:2017-12-31
  • Extracting potable water from humid air plus electric wind generation: A possible application for a Brazilian prototype
    Renew. Energy (IF 4.357) Pub Date : 2017-12-30
    J.S. Solís-Chaves, C.M. Rocha-Osorio, A.L.L. Murari, Valdemir Martins Lira, Alfeu J. Sguarezi Filho

    This work shows a technical review for two promising technologies and two commercial systems that can be applied in Hybrid Wind Systems —also known as Extraction Water from Air Systems (EWAS) — for the special weather conditions presents in Brazilian northeast. Additionally, a full description of the main components for the innovative technologies and for commercial solutions are explained. An energy consumption analysis for each one of these systems is made for comparison purposes. Water extraction capacity and energy efficiency are evaluated (for two commercial EWAS) for a theoretical operation point in the middle of the North–eastern semi–desert region. This point is obtained by means of the well–known humid air diagram. Important information about minimum environmental conditions for Membranes and Coils are also considered. Three main types of electric generators are described, including its advantages and disadvantages, for the estimation of the power ratio to generating electricity and water. For all above, the right sizing of the future Brazilian EWAS prototype and its possible application in a semi-arid region is the objective of this paper.

    更新日期:2017-12-31
  • Small wind turbines: A numerical study for aerodynamic performance assessment under gust conditions
    Renew. Energy (IF 4.357) Pub Date : 2017-12-30
    L. Menegozzo, A. Dal Monte, E. Benini, A. Benato

    In the present work, a numerical study aimed to analyse the effect of an extreme loading event on a Horizontal Axis Wind Turbine (HAWT) is performed. A 3D unsteady CFD model of the NREL Phase VI small-sized wind turbine is validated against experimental data, with the incompressible solver of ANSYS Fluent and an unstructured moving mesh strategy. Then the Extreme Operating Gust (EOG) model from IEC 61400-2 is considered as the inlet condition. The results of the aerodynamic response and of the structural ultimate check, based on the IEC guidelines, are presented for both the operating and the parked turbine, in order to underline the benefit of the safety position in terms of lower stress transferred to the critical root section.

    更新日期:2017-12-31
  • Influence of hybrid nanofluids on the performance of parabolic trough collectors in solar thermal systems: Recent findings and numerical comparison
    Renew. Energy (IF 4.357) Pub Date : 2017-12-29
    Alina Adriana Minea, Wael M. El-Maghlany

    Research on solar energy depicted its ability to be converted into thermal energy using trough collector system and solar concentrators, and then to electrical energy using a steam turbine. In this article authors tried to review some solar applications of nanofluids with reference to hybrid nanofluids and their possible use for solar energy systems. The heat transfer performance of ordinary heat transfer fluids (for example: water, ethylene glycol, oils etc) is limited due to their low thermal conductivity. Hence, to increase the overall heat transfer performance of a solar system, a new fluid have to be considered by adding high conductive solid nanoparticles. This was accomplished with the appearance of nanofluids and later on hybrid nanofluids. In almost all studies and reviews authors are recommending the increase of the research efforts in nanofluids further application in solar systems and this review tries to shed some light on the importance of using new heat transfer fluids, too. Our study demonstrated clearly an enhancement in Nu number for all considered hybrid nanofluids. The highest increase in average Nu is noticed for the Cu-MgO hybrid at 2% volume concentration, where the escalation is almost 14% in comparison with the base fluid. However, the high viscosity escalation for some hybrids determined a high pressure drop penalty. Plus, the collector efficiency rises while Re increase and the 2% Ag-MgO-water hybrid nanofluid offers the maximum efficiency of the solar collector. As a conclusion, hybrid nanofluids are a very good candidate for solar energy systems, especially with reference to solar collectors. Nevertheless, a tremendous experimental and numerical work is needed in order to implement new heat transfer fluids in solar specific applications.

    更新日期:2017-12-31
  • A decision support tool to assist with lifetime extension of wind turbines
    Renew. Energy (IF 4.357) Pub Date : 2017-12-29
    T. Rubert, D. McMillan, P. Niewczas
    更新日期:2017-12-31
  • Conversion of atmospheric variations into electric power – Design and analysis of an electric power generator system
    Renew. Energy (IF 4.357) Pub Date : 2017-12-29
    S. Ganesh, G. Ali, D. Moline, T. Schweisinger, J. Wagner

    Given its abundant availability, ambient thermal energy harvesting has the potential to power standalone microelectronic systems. The challenge in efficiently harvesting temperature and pressure variations is the low thermal to electric conversion ability of current harvesters. Most thermal harvesters require high temperature gradients. This paper presents the design, analysis, and implementation of an energy harvesting system that effectively harnesses naturally occurring temperature variations using ethyl chloride filled mechanical bellows. A mechanical drivetrain scales the bellows displacement and a coil spring stores the potential energy. This energy is periodically released and converted into useable electric power by a DC generator. A series of mathematical models are developed and accompanying numerical analyses completed on the harvester system. For a low frequency sinusoidal temperature cycle of ±1 °C about 22 °C, 9.6 mW of electrical power was produced using a 1.5 V micro DC generator for a 24 h harvesting period. The power generation capacity of the proposed harvester is sufficient to indefinitely operate low power sensors and microelectronics in environments with small temperature gradients.

    更新日期:2017-12-31
  • International vs. domestic bioenergy supply chains for co-firing plants: the role of pre-treatment technologies
    Renew. Energy (IF 4.357) Pub Date : 2017-12-29
    Caterina Mauro, Athanasios A. Rentizelas, Damiana Chinese

    Co-firing of solid biomass in existing large scale coal power plants has been supported in many countries as a short-term means to decrease CO2 emissions and rapidly increase renewable energy shares. However, many countries face challenges guaranteeing sufficient amounts of biomass through reliable domestic biomass supply chains and resort to international supply chains. Within this frame, novel pre-treatment technologies, particularly pelletization and torrefaction, emerged in recent years to facilitate logistics by improving the durability and the energy density of solid biomass. This paper aims to evaluate these pre-treatment technologies from a techno-economic and environmental point of view for two reference coal power plants located in Great Britain and in Italy. Logistics costs and carbon emissions are modelled for both international and domestic biomass supply chains. The impact of pre-treatment technologies on carbon emission avoidance costs is evaluated. It is demonstrated that, for both cases, pre-treatment technologies are hardly viable for domestic supply. However, pre-treatment technologies are found to render most international bioenergy supply chains competitive with domestic ones, especially if sourcing areas are located in low labour cost countries. In many cases, pre-treatment technologies are found to guarantee similar CO2 equivalent emissions performance for international compared to domestic supply chains.

    更新日期:2017-12-31
  • Economic potential of flexible balloon biogas digester among smallholder farmers: a case study from Uganda
    Renew. Energy (IF 4.357) Pub Date : 2017-12-29
    Moris Kabyanga, Bedru B. Balana, Johnny Mugisha, Peter N. Walekhwa, Jo Smith, Klaus Glenk

    Biogas technology, as a pro-poor renewable energy source, has been promoted in Uganda since the 1980s by the government and NGOs. However, many of the biogas designs promoted have proved to be too expensive for the average Ugandan to afford. A cheaper flexible balloon digester has been proposed, but there have been lack of evidence on the economic viability of this design. The purpose of this study was to analyze the economic potential of a flexible balloon digester among smallholder farmers in Uganda using the tool of cost-benefit analysis. Primary data were obtained from survey of experimental households and 144 non-biogas households in central Uganda. The results revealed that the net present value was negative and the payback period was greater than the economic life of the digester. However, sensitivity analysis revealed that with a 50% reduction in investment cost the technology is financially viable for 67% of the households and to all households as a group (NPV= UGX5,804,730). The initial investment cost is a critical factor to viability and potential adoption. We suggest that government and development partners interested in the sector should consider strategies that could reduce strategies that could reduce the technology cost e.g., manufacturing low cost balloon digester locally.

    更新日期:2017-12-31
  • The experimental evaluation and improvements of a novel thermal diode pre-heat solar water heater under simulated solar conditions
    Renew. Energy (IF 4.357) Pub Date : 2017-12-29
    M. Smyth, P. Quinlan, J.D. Mondol, A. Zacharopoulos, D. McLarnon, A. Pugsley

    This paper presents the development through experimental performance characterisation of a pre-heat Integrated Collector Storage Solar Water Heater using a novel thermal diode operation to reduce ambient heat loss during non-collection periods. Using a solar simulator facility at Ulster University, the novel prototype pre-heat Mark IV unit was tested and evaluated. The concept has been designed and developed to be a sustainable pre-heat alternative to other types of solar water heating systems traditionally used in domestic hot water installations. The highest 6 h collection efficiency was 36.17% under solar simulated conditions. The lowest system ‘U’ value was 0.98 Wm−2K−1 with no draw-off conditions. When the current prototype ICS units are compared with other conventional ICS systems, particularly in terms of thermal retention during non-collection periods, an improved performance is clearly demonstrated. The measured thermal losses were approximately 40% less than other similarly measured systems.

    更新日期:2017-12-31
  • Model-based fault detection, fault isolation and fault-tolerant control of a blade pitch system in floating wind turbines
    Renew. Energy (IF 4.357) Pub Date : 2017-12-29
    Seongpil Cho, Zhen Gao, Torgeir Moan

    This paper presents model-based fault detection, fault isolation, and fault-tolerant control schemes focused on blade pitch systems in floating wind turbines. Fault detection, isolation, and accommodation techniques are required to achieve high power capture efficiency and structural reliability in floating wind turbines. Faults in blade pitch systems should be detected at an early stage to prevent catastrophic failures. To detect faults of the blade pitch systems, a Kalman filter is designed to estimate the blade pitch angle of the system. The fault isolation algorithm is based on inference methods and capable of determining the fault type, location, magnitude and time. The fault-tolerant controller based on a reconfiguration block with a virtual sensor and shutdown mode controls the floating wind turbine to avoid unexpected external loads. The proposed methods are demonstrated in case studies with stochastic wind and wave conditions that considering different types of faults, such as biases and fixed outputs in pitch sensors and stuck pitch actuators. The simulation results show that the proposed methods can detect and isolate multiple faults effectively at an early stage. Additionally, the effectiveness of the fault-tolerant control systems for different load cases for single and multiple fault conditions is verified by numerical simulations.

    更新日期:2017-12-31
  • On the Welfare Effects of Subsidy Game for Renewable Energy Investment: Toward a Dynamic Equilibrium Model
    Renew. Energy (IF 4.357) Pub Date : 2017-12-29
    Yong-cong Yang, Pu-yan Nie, Hui-ting Liu, Ming-hao Shen

    This paper focuses on the welfare effects of subsidy game for renewable energy investment between two neighboring regions. By employing a dynamic control model, the stationary equilibrium is solved under various scenarios. The major findings indicate that, the optimal subsidy strategies for both regions depend on a series of factors, including social capital, emission intensity of traditional energy and production efficiency of renewable energy and so on. Meanwhile, neither competitive strategy nor cooperative strategy is necessarily better than the other in the bidding game. Furthermore, the effects of Pigouvian tax on subsidy intensity are negative, while the changes of the equilibrium investment of renewable energy are uncertain.

    更新日期:2017-12-31
  • Design of pico-hydro turbine generator systems for self-powered electrochemical water disinfection devices
    Renew. Energy (IF 4.357) Pub Date : 2017-12-28
    D. Powell, A. Ebrahimi, S. Nourbakshsh, M. Meshkahaldini, A.M. Bilton

    Previous research has demonstrated the potential of pico-hydro turbines to provide reliable electricity in applications such as rural electrification. However, the literature has primarily focused on the development of turbine systems for design environments where spatial and flow rate constraints tend to be non-restrictive. The work detailed in this paper presents the development of a novel, compact, high efficiency turbine capable of powering a compact electrochemical cell for off-grid water disinfection. The turbine with the generator is capable of generating nearly 100 W of power with a footprint of only 8″ in length and 4″ in diameter. A basic mathematical model of a DC generator is coupled to a computational fluid dynamics (CFD) turbine model to evaluate different system configurations. Following a Taguchi Method study to computationally explore the turbine design space, experimental testing of improved turbine configurations is shown to provide electrical power output improvements of 20%. Selection of a more compatible DC generator also provides electrical power output and efficiency improvements of a factor of 2 and 2.5 respectively.

    更新日期:2017-12-31
  • Highly efficient conversion of glucose into methyl levulinate catalyzed by tin-exchanged montmorillonite
    Renew. Energy (IF 4.357) Pub Date : 2017-12-28
    Jie Liu, Xue-Qian Wang, Bei-Bei Yang, Chun-Ling Liu, Chun-Li Xu, Wen-Sheng Dong

    Tin-exchanged montmorillonite catalysts were prepared by an ion exchange method and examined as solid acid catalysts. The synthesized catalysts were characterized by X-ray fluorescence spectroscopy, inductively coupled plasma optical emission spectroscopy, N2 adsorption–desorption analysis, powder X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, NH3 temperature-programmed desorption analysis, and pyridine adsorption Fourier transform infrared spectroscopy. Subsequently, the catalysts were examined for use in the conversion of glucose into methyl levulinate in methanol. A high yield of methyl levulinate of 59.7% was obtained upon conversion of 0.3 g glucose in 24 g methanol over 0.15 g catalyst at 220 °C under 2 MPa N2 for 6 h. The recyclability of the catalyst was also examined, and the conversions of glucose and methanol remained mostly unchanged under repeated usage of the catalyst in five catalytic runs; in contrast, the yield of methyl levulinate decreased slightly. The excellent catalytic performance of the tin-exchanged montmorillonite catalyst was attributed to a combination of the presence of a large amount of acidic sites and balanced amounts of Lewis and Brønsted acid sites on the catalyst.

    更新日期:2017-12-31
  • A Novel approach for extraction of algal oil from marine macroalgaeUlva fasciata
    Renew. Energy (IF 4.357) Pub Date : 2017-12-28
    Theresa Veeranan, Ramachandran Kasirajaan, Baskar Gurunathan, Renganathan Sahadevan

    In this present investigation, lipid extraction was performed in marine macro algae Ulva fasciata using soxhlet and super critical fluid extraction apparatus. The ultrasonic pretreatment was done for the algal biomass. Extraction parameters for High extraction yield of algal oil were obtained at 5 % moisture content, 0.25 mm particle size, 90 ºC, 180 min time, 5:1 solvent-to-solid ratio and solvent flow rate 1 l/hr. After the optimization process 9.85% of oil extraction was obtained from Ulva fasicataalgal biomass. The aromatic groups, indicating the presence of 12-Hydroxy-9-octadecenoic acid was confirmed by FT-IR analysis. Thus the algal oil obtained from Ulva fasicata biomass can be used for the biodiesel production. The saturated fatty acid (SFAs) was found to be 75.43% in the produced algal oil. The properties like Acid value, Iodine number, specific gravity, Saponification value, calorific value, Flash point, Fire point and kinematic viscosity was also characterized.

    更新日期:2017-12-31
  • Variable Gain Control Scheme of DFIG-based Wind Farm for Over-Frequency Support
    Renew. Energy (IF 4.357) Pub Date : 2017-12-28
    Yujun Li, Zhao Xu, Jianliang Zhang, Kit Po Wong

    In order to mitigate over-frequency events in the power systems, this paper proposes a new variable gain based control strategy to maximize the frequency support while minimizing impacts to the overall energy production for a wind power plant (WPP). Because of different wind conditions, the energy production by each WT is not equally compromised by adaptively adjusting the droop gains according to the different rotor speeds so that minimal reduction of energy production can be ensured. The control performance was fully investigated in a doubly fed induction generator (DFIG) based WPP and the results clearly indicate the proposed variable droop gain scheme can harness more wind energy than the conventional same droop gain scheme while providing similar frequency support.

    更新日期:2017-12-31
  • Energy and economic losses caused by dust on residential photovoltaic (PV) systems deployed in different climate areas
    Renew. Energy (IF 4.357) Pub Date : 2017-12-28
    Julius Tanesab, David Parlevliet, Jonathan Whale, Tania Urmee

    Results of the study revealed that when dust impinged on the surface of the PV modules, monthly maximum power output of a 1.5 kWp system in Perth, Australia and a 50 Wp system in Nusa Tenggara Timur (NTT), Indonesia decreased, on average, by about 4.5% and 8%, respectively. Economic modelling showed that, the cost of production per kWh lost due to dust exhibited by these systems were A$ 0.26/kWh and A$ 0.15/kWh, respectively. Comparison of the cost of energy losses and maintenance revealed that, the Perth system would require manual cleaning in October while the system in NTT would require cleaning in August and October. Although the saving in production losses is not economically significant, this cleaning schedule was recommended, particularly for small systems in NTT since the extra output can have a significant effect on the quality of life in remote villages. The key finding was that higher dust de-rating factors and more cleaning activity may be more appropriate for PV systems deployed in tropical climate areas than that in temperate climate regions. It is recommended that PV system Standards that use the 5% performance de-rating factor due to soiling are reviewed and consideration given to climate-dependent de-rating factors.

    更新日期:2017-12-31
  • Synthesis and characterization of PEG/ZSM-5 composite phase change materials for latent heat storage
    Renew. Energy (IF 4.357) Pub Date : 2017-12-28
    Chaoen Li, Hang Yu, Yuan Song, Mei Zhao
    更新日期:2017-12-31
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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