Published: 2016-07-30

Pilot application on solar energy combined electricity grid to a rural water supply station in Can Tho city

Le Anh Tuan
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Since 2008, a Clean Development Mechanism project, which can be counted towards meeting Kyoto targets, has been formed by Japan International Research Center for Agriculture Sciences and Can Tho University (JIRCAS-CTU). In this project, My Phung Hamlet, My Khanh Village, Can Tho City was chosen to implement a greenhouse-gas emission reduction model. One of the activities of the project, a domestic water supply plant was surveyed, designed and installed. A part of electricity sources used for plant operation is generated by solar panels. The selection of renewable energy is to fit the objectives of JIRCAS-CTU Project. The project objective is to introduce of renewable energy for My Phung Water Supply Station by selecting one of the natural unpolluted, clean and rich energy resources such as bio-gas, wind, river flow and solar. The research has begun by surveying works, including the workshop results, water sampling and quality analysis, selection of water source alternatives, and design drawings of water supply and power application alternatives. In My Phung Hamlet’s drinking water supply plant, water input for the plant is taken by a deep groundwater well and the power for the pump supplied partly by solar energy combined electricity grid system. Finally, some recommendations after the plant construction and pipelines are given for a future greenhouse-gas emission research and management. It is found that solar energy application is a new approach for local conditions and fitting the purpose of CDM objectives. However, the cost of solar panels is still high that leads to a limitation for the implementation if the financial is shortage.

Vietnam’s renewable energy - an overview of current status and legal normative documents

Nguyen Vo Chau Ngan, Nguyen Lan Huong
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This paper aims to overview current status on exploiting and applying energy in general and renewable energy in particular in Vietnam and to present the Vietnamese policy on renewable energy. Vietnam is located in a tropical area, which is highly potential for renewable energy development with various sources such as biomass, solar, wind, solid waste, etc. but exploitation capacities on these resources are limited. The Vietnamese Government gradually institutionalizes legal normative documents to promote energy exploitation from local potential renewable energy.

Biodiesel production and use for agricultural production in the mekong delta: current status and potential

To Lan Phuong, Bui Thi Buu Hue, Nguyen Hong Tin, Chau My Duyen, Ho Chi Thinh, Hua Nguyen Phuc, Tran Le Kim Thuy
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Mekong Delta plays an important role in Vietnam agriculture and food security. It contributes more than 90% nation rice export quantity and 70% fishery and fruit tree products. Currently, a huge amount of fossil diesel has been consuming in farming activities such as land preparation, irrigation, harvesting, and product transportation. The use of fossil diesel can cause environmental pollution and farmers’ health impacts. In the Mekong Delta, raw materials for biodiesel production are widely available, for example catfish fat (Pangasius) and coconut oils. Up to 2020, it is predicted that demands and potential use of biodiesel in agricultural production is very high, particular in rice, fruit trees production and aquaculture. Therefore, using biodiesel in the Mekong Delta’s agriculture sector is an emerging trend in the future. This paper presents current status and potential of using biodiesel in agricultural production activities in the Mekong Delta, Vietnam. Participatory approach including Focus Group Discussion-FGD, Key Informant Panel-KIP and Households Interviews (484 samples) were employed to collect data. Descriptive statistics and binary logistics were applied to analyse collected data. Results showed that biodiesel was not popularly used yet due to many reasons such as high production costs, unavailability in the local area, and users’ awareness on using it. Recently, there are many policies encouraging biodiesel use in agricultural production. More than 80% of farmers have agreed to use biodiesel in agricultural production activities with some required conditions such as information on biodiesel, quality, production costs, and use efficiency.

An overview of the renewable energy potentials in the Mekong river Delta, Vietnam

Le Anh Tuan
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The mekong river delta is the most southern region of viet nam, having a whole year strong solar radiation and a long coastal line towards both the east sea and the west sea. The delta also is recognised as a biggest agriculture - aquaculture - mangrove forest production of the nation, promising on her rich-biomass provision. So, this region is quite favourable for the potential development of renewable energy resources in different types and levels. Currently, all provinces of the mekong river delta depend mainly on thermal energy by burning non-renewable sources as coal, oil and gas fuels to produce electricity. These power energy plants are connecting throughout the country over nationwide grid-electricity system. Last three decades, vietnamese government has paid attention on hydropower development in the north and the central of vietnam, while the renewable energies from solar, wind, tide and biogas sources seem to be disregarded in the national and provincial socio-economic development strategy plans. However, during the past 5 years, vietnam has started to promote renewable energy development programs as part of the climate change mitigation and adaptation solutions of the national action plans, special in the southern region. This report will inventory some data figures on the regional renewable energy resources, focusing to solar, wind and rice husk energies. Additional discussion, renewable energy policies are noticed as possible solutions for the development and exploitation of cleaner powers that may be concerned.

Conversion of water hyacinth Eichhornia crassipes into biofuel intermediate: combination subcritical water and zeolite based catalyst processes

Felycia Edi Soetaredjo, Suryadi Ismadji, Yi-Hsu Ju
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The production of gamma-valerolactone, a biofuel intermediate, from water hyacinth is reported in this article. Gamma-valerolactone is an attractive platform chemical that can be further converted into a variety of chemical derivatives for wide use in industrial applications. In this study, we employed a combination of solid acid catalyzed and subcritical water processes to convert hemicellulose and cellulose derived from water hyacinth in levulinic acid, and subsequently followed by catalytic hydrogenation of levulinic acid into gamma-valerolactone. Prior to the catalytic conversion of water hyacinth into levulinic acid and gamma-valerolactone, the lignin content in the water hyacinth was removed by alkali pretreatment using sodium hydroxide solution. The maximum yield of levulinic acid was 173.4 mg/gram dried water hyacinth obtained at 40 bar, 200°C, reaction time of 120 min, and in the presence of acid activated zeolite catalyst. The hydrogenation reactions of levulinic acid into gamma-valerolactone were conducted at 160 to 220°C in the presence of mixed catalysts (Pt/TiO2 and acid activated zeolite). The experimental results indicated that the mixed acid activated zeolite and Pt/TiO2 catalysts gave good performance on the conversion of levulinic acid into gamma-valerolactone (more than 95% conversion).

Microalgal culture with digestate from methane fermentation - light environment in the culture solution with different digestate concentrations and microalgal cell densities

Nguyen Khanh, Maeda Yasuaki
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The light intensity decreases logarithmically in the solution according to Lambert- Beer’s law that is given by equation P2 = P1 exp(-b(Z2-Z1)). Absorption coefficient is expressed as (b) = (ln (P1)-ln (P2))/(Z2-Z1), where P1 and P2 are photosynthetic photon flux densities (PPFDs) at depth Z1 and Z2, respectively, in the culture solution. The light absorption coefficients of culture solutions with different digestate concentrations and different microalgal densities were determined by spectrophotometer in the wavelength range of photosynthetic active radiation (400-700 nm). A linear regression was obtained between the absorption coefficient (cm-1) and digestate concentration (%) expressed as bdigestate = 0.0546 × "digestate concentration" + 0.005. A linear regression was also obtained between the absorption coefficient and the microalgal density (cells ml-1) expressed as bmicroalgae = 0.0655 × "microalgal density" + 0.0402. In simulation experiment conducted with microalgal density of 30×105 cells ml-1, more than 10% of light was transmitted at the depths shallower than 15 mm, using 20% diluted digestate.

Selective adsorption of H2S in biogas using zeolite prepared by microwave-assisted method

Nguyen Quang Long, Hoang Thi Thu Binh
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This research focuses on development of a purification method for biogas - a potential sustainable fuel using Zn- exchanged zeolites. Different with traditional hydrothermal synthesis, the zeolite in this study has been synthesized via a microwave-assisted method in order to shorten the crystallization time. Various techniques were utilized for characterization of the adsorbents. The crystalline structure of the materials was analyzed by XRD (X-ray Diffraction). Scanning Electron Microscopy (SEM) was applied for morphology analysis. The H2S adsorption activity of the material was determined by a fixed-bed absorption column and the expressed by the H2S absorption capacity below a specified breakthrough point (50 ppm). H2S adsorption capacity of about 13 mgS/g was achieved. It was observed that although high concentration of CO2 was presented in the feed stream, the Zn-exchanged zeolite can selectively remove H2S in the gas mixture.

Prediction in off-design operation for the helical heat recovery exchanger

Nguyen Minh Phu, Hoang Trong Tran Huy, Le The Truyen, Trinh Tien Tho
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Helical heat exchangers are commonly used to exchange the thermal energy in waste heat recovery systems. Ammonia rectifier in absorption chiller and heat recovery steam generator are examples typically found in open literature. They are widely employed because of its compactness, high heat exchange rate, compensation of thermal expansion, vibration resistance, simple construction, and low capital cost. Heat exchanger researches have almost focused on straight tubes. However, study on helical heat exchanger has not been paid attention. In this study, a simplified model is developed to predict single phase heat transfer and pressure loss in the helical heat exchanger under various operating conditions without geometrical information inside the exchanger required. Methods of LMTD and e-NTU, and selective empirical correlations are presented in the model. Simulation results were achieved good agreement with the experimental data with a moderate tolerance. The model would be expected as a good tool for designers to the pre-design and correct selection of helical heat exchanger in thermal network.

Fabrication and characterization of graphene/graphene oxide based poly (vinyl alcohol) nanocomposite membranes for pervaporation dehydration of ethanol

Nguyen Huu Hieu, To Lan Anh, Ngo Nguyen Phuong Duy
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Graphene (reduced graphene oxide-rgo) or graphene oxide (go)/poly(vinyl alcohol) (pva) nanocomposite membranes were fabricated by solution-casting method. The effects of additive content on the pervaporation (pv) performance of membranes were investigated. The membrane characterizations were performed by fourier-transform infrared spectroscopy, differential scanning calorimetry, x-ray diffraction, and transmission electron microscope. The characterized results indicated that thermal stability and pv performance of nanocomposite membranes were improved compared to the neat pva membrane. In comparison with neat pva, rgo/pva membrane showed a high selectivity of 51.2, but low permeate flux of 0.056 kg.m-2h-1); and go/pva exhibited an acceptable selectivity of 34.9, however equivalent permeate flux of 0.120 kg.m-2h-1

A revisit on dissipation and its relation to irreversible processes

Nguyen Quang Long, Nguyen Chi Thuan, Hoang Ngoc Ha
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As usual, industrial process systems operate far from (stable) equilibrium. Under practical operating conditions when putting the system back in equilibrium, this gives rise to the loss of energy (or certain generalized energy). Following the second law of thermodynamics, an irreversible process generates entropy. On the basis of this property, we propose an approach that allows to investigate quantitatively the amount of (generalized) energy lost when the system reaches equilibrium. A liquid phase reactor modelled with the CSTR (continuous stirred tank reactor) in which the acid-catalyzed hydration of 2-3-epoxy-1-propanol to glycerol subject to steady state multiplicity takes place is used to illustrate the results.

Modified controls for doubly fed induction generator under unbalanced voltage for torque stability controller

Nguyen Thanh Hai, Phan Quoc Dzung, Vo Viet Cuong
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This paper presents both the previously and newly modified Stator Flux Oriented Control (SFOC) with Pulse Width Modulation (PWM) and Hysteresis Current Controller (HCC) structures for Doubly Fed Induction Generator (DFIG) in wind turbines to improve responses of active power, reactive power and generator's torque during the grid voltage unbalance. In the proposed SFOC-based scheme, which emphasizes on improvement of generator's torque performance, PI controllers with Fuzzy logic, Notch filters and the Torque Stability Controller (TSC) are utilized. The other control techniques use single or multiple applications of PI controller with anti-windup, hybrid PI-Fuzzy controller with anti-windup and Notch filter to eliminate the second-order harmonic components. The designed system consists of a wound rotor induction generator and power-electronics converters at both rotor and grid sides. The modifications are applied to the rotor side converter (RSC). Simulations in Matlab/Simulink illustrate the enhanced stability of torque, active and reactive powers delivered by DFIG in both the SFOC-based and HCC-based schemes. Moreover, comparisons in simulation results, obtained separately from all the presented control structures, are provided to evaluate the effectiveness of the newly proposed scheme.

Potential of using activated sludge as feedstock for biodiesel production in Taiwan

Tran Nguyen Phuong Lan, Meng-Jiy Wang, Yi-Hsu Ju, Jhy-Chern Liu
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Commercial production of biodiesel mainly uses refined edible oil as the feedstock which constitutes about 70% to 85% of the overall cost of biodiesel. Finding cheap and abundant new feedstock for producing biodiesel is necessary. The use of non-edible oil such as waste cooking oil and algae oil may help in reducing the production cost of biodiesel. In this study, 5 wet sludge samples were collected from a wide spectrum of industries in Taiwan and which were treated by subcritical water to enhance the amount of their extractable lipids. Reaction temperature was found to be the most important factor in increasing the extractable neutral lipids (2 to 3.5 times) which can be esterified with methanol to produce biodiesel. The economic potential of using activated sludge as feedstock for biodiesel production in Taiwan was discussed.

Biological characteristics of poon trees Calophyllum inophyllum L. and its extracted oil used as starting material for biodiesel production

Nguyen Xuan Loc, Le Thi Ngoc Ly, Nguyen Huu Chiem, Do Thi My Linh
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This study was aimed to investigate the chemical and biological characteristics of Poon trees Calophyllum inophyllum L. and its extracted oil as starting material for synthesizing biodiesel. Density, seed yield and biomass of Poon trees were investigated in the field for biological characteristics while fatty acid composition and oil quality were determined as chemical characteristics. Seed yield of a ten-year Poon tree was 74.8 kg/tree/year. Poon tree density and biomass were 625 trees/ha and 0.16 ton/tree, respectively; oil yield was 13.4 L/tree/season or 17,187 L/ha/year. Fatty acid composition of poon oil was found to include 2.35%, 7.62%, 12.4% and 3.44% of stearic, oleic, linoleic and palmitic acids, respectively. Acid value; saponification value; iodine value and oil density were 10.5, 184, 88.8 and 0.94 Kg/L, respectively. Biodiesel produced from the extracted Poon oil contained 91% of fatty acid methyl esters.

Study on fermentation conditions for bioethanol production from cocoa pod hydrolysate

Huynh Xuan Phong, Nguyen Ngoc Thanh, Pham Thieu Quan, Ngo Thi Phuong Dung
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Bioethanol is an environmentally friendly fuel and renewable source in many industrial applications. Cocoa pod is an abundant agro-waste source and can be used for bioethanol production because this lignocellulosic material has high content of cellulose. The aim of this study was to investigate the ability for bioethanol production from cocoa pod hydrolysate. Four strains of Saccharomyces cerevisiae (2.1, B3, D3, D4) were examined for bioethanol production from cocoa pod hydrolysate with the initial inoculation levels at 102, 104, 106, 107 cells/mL. The fermenting medium was tested with the reducing sugar concentration in a range of 5.0, 6.0, 7.0, and 8.6% (w/v) and pH value at 4.5, 5.0, 5.5 and 6.0. The fermentation conditions were designed at different temperatures (25, 30, 37°C) and times (3, 5, 7, 9 days). The results showed that the suitable yeast strain for ethanol fermentation was S. cerevisiae D3 with the inoculum level of 106 cells/mL. The ethanol concentrations of 4.14-4.19% (w/v) were achieved after 9 days at 30°C from cocoa pod hydrolysate contained 8.6% (w/v) of reducing sugar with initial pH at 5.5, the sugar consumption efficiencies were 97.54-97.56%. These outputs indicated the promising feasibility of bioethanol production from such waste material source of cocoa pods.