Browsing by Author "Chen, Chiun-Hsun"

Now showing 1 - 20 of 40

A mutant strain of microalga Chlorella sp for the carbon dioxide capture from biogas
(2012-01-01)
Kao, Chien-Ya
;
Chiu, Sheng-Yi
;
Huang, Tzu-Ting
;
Dai, Le
;
Wang, Guan-Hua
To upgrade biogas produced from the anaerobic digestion of swine wastewater, an outdoor photobioreactor was established in this study. A mutant strain of microalga Chlorella sp. MM-2 was firstly isolated by ethyl methane sulfonate-induced random mutagenesis. The Chlorella sp. MM-2 grew in the presence of gas containing H2S < 100 ppm, and the growth capacity of the microalgal culture aerated with 80% CH, was similar to 70% that of the control culture (0% CH4). In the field study, CO2 capture efficiency of the Chlorella cultures, at a biomass concentration of 1.2 g L-1, from the desulfurized biogas (-20% CO2, 70% CH4 and H2S < 100 ppm) was approximate 70% on cloudy days and 80% on sunny days. CH4 concentration in the effluent biogas from the Chlorella cultures was increased to approximate 84% on cloudy days and 87% on sunny days from its original 70%. The established outdoor photobioreactor system using a gas cycle-switching operation could be used as a CO2 capture model for biogas upgrading. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.
A Nanodot Array Modulates Cell Adhesion and Induces an Apoptosis-Like Abnormality in NIH-3T3 Cells
(2009-08-01)
Pan, Hsu-An
;
Hung, Yao-Ching
;
Su, Chia-Wei
;
Tai, Shih-Ming
;
Chen, Chiun-Hsun
Micro-structures that mimic the extracellular substratum promote cell growth and differentiation, while the cellular reaction to a nanostructure is poorly defined. To evaluate the cellular response to a nanoscaled surface, NIH 3T3 cells were grown on nanodot arrays with dot diameters ranging from 10 to 200 nm. The nanodot arrays were fabricated by AAO processing on TaN-coated wafers. A thin layer of platinum, 5 nm in thickness, was sputtered onto the structure to improve biocompatibility. The cells grew normally on the 10-nm array and on flat surfaces. However, 50-nm, 100-nm, and 200-nm nanodot arrays induced apoptosis-like events. Abnormality was triggered after as few as 24 h of incubation on a 200-nm dot array. For cells grown on the 50-nm array, the abnormality started after 72 h of incubation. The number of filopodia extended from the cell bodies was lower for the abnormal cells. Immunostaining using antibodies against vinculin and actin filament was performed. Both the number of focal adhesions and the amount of cytoskeleton were decreased in cells grown on the 100-nm and 200-nm arrays. Pre-coatings of fibronectin (FN) or type I collagen promoted cellular anchorage and prevented the nanotopography-induced programed cell death. In summary, nanotopography, in the form of nanodot arrays, induced an apoptosis-like abnormality for cultured NIH 3T3 cells. The occurrence of the abnormality was mediated by the formation of focal adhesions.
A study of caprolactam storage tank accident through root cause analysis with a computational approach
(2017-11-01)
Liu, Wei-Yi
;
Chen, Chiun-Hsun
;
Chen, Wei-Ting
;
Shu, Chi-Min
;
機械工程學系
In Taiwan, the rapid development of the petrochemical industry over the past four decades has resulted in economic progress and technological advancement. However, this success has been accompanied by pollution and sporadic accidents. Numerous accidents related to crude oil and its derivatives have resulted in a loss of life, employee injuries, environmental and property damage, economic decay, social outcry, and even political turmoil. This study investigated a caprolactam storage tank accident through root cause analysis with a computational approach. The previously described approaches returned findings that indicated causes similar to the real cause of this caprolactam accident. The four summarized descriptions of false conditions of the caprolactam explosion can serve as a reference for other investigations into the causes of petrochemical accidents. Reason of the caprolactam storage tank accident was determined by root cause analysis accompanying with a computational approach. (C) 2017 Elsevier Ltd. All rights reserved.
An Experimental Study on Micro Proton Exchange Membrane Fuel Cell
(2012-06-01)
Chen, Chiun-Hsun
;
Chen, Tang-Yuan
;
Cheng, Chih-Wei
;
Peng, Rong-Guie
;
機械工程學系
This study fabricates a micro proton exchange membrane fuel cell (PEMFC) using micro electro mechanical systems (MEMS) technology. The active area of the membrane is 2 cm x 2 cm (4 cm(2)). The study is divided into two categories: [(1) the parametric experimental investigation, and (2) the durability test. This work is an attempt to find out how several parameters, including reheat temperature, the material of the current collector plates, the open ratio, and different cathode gases affect micro PEFMC performance. According to the experimental results obtained, both the conducting area and the material of the current collector plates exert great influences on the performance of the micro PEMFC, especially in the conducting area. The cell's performance is finite when the gas reheat temperature is increased. The results show that the cell performance is better for an open ratio of 75% as compared to ratios of 50% and 67%. The concentration polarization is improved by increasing the air flow rate at high current densities, and if the GDL diffusive capability in the latter cell could be promoted, the differences between these two cells' performances would be reduced. Furthermore, the performance at an operating voltage of 0.6 V was the most stable one among the four cases tested, and the performance deviation at a fixed operating voltage of 0.4 V was less than +/- 2.2%. [DOI:10.1115/1.4005612]
Analysis of Pyramidal Surface Texturization of Silicon Solar Cells by Molecular Dynamics Simulations
(2008)
Chung, Hsiao-Yen
;
Chen, Chiun-Hsun
;
Chu, Hsin-Sen
;
機械工程學系
;
Department of Mechanical Engineering
The purpose of this paper is to explore the relations between surface texturization and absorptance of multicrystalline silicon solar cells by a simple new model, based on the classic molecular (MD) dynamics simulation, alternative to complex electron-photon interactions to analyze the surface texturization of solar cells. In this study, the large tilted angle leads to the lower efficiency of solar cell. To consider the effect of incident angle, a range of high efficiency exists due to the increasing probability of second reflection. Furthermore, the azimuth angle of incident light also affects the efficiency of solar cells. Our results agree well with previous studies. This MD model can potentially be used to predict the efficiency promotion in any optical reflection-absorption cases. Copyright (C) 2008 Hsiao-Yen Chung et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Analysis of surface texturization of solar cells by molecular dynamics simulations
(2008)
Chung, Hsiao-Yen
;
Chen, Chiun-Hsun
;
Chu, Hsin-Sen
;
機械工程學系
;
Department of Mechanical Engineering
The purpose of this paper is to develop a simple new model, based on the classic molecular dynamics simulation (MD), alternative to complex electron-photon interactions to analyze the surface texturization of solar cells. This methodology can easily propose the absorptance differences between texturing and nontexturing solar cells. To verify model feasibility, this study simulates square, pyramidal, and semicircular texturization surfaces. Simulations show that surface texturization effectively increases the absorptance of incident light for solar cells, and this paper presents optimal texturization shapes. The MD model can also be potentially used to predict the efficiency promotion in any optical reflection-absorption cases. Copyright (C) 2008 Hsiao-Yen Chung et al.
Communications and Networking Technologies for Intelligent Drone Cruisers
(2019-01-01)
Wang, Li-Chun
;
Lai, Chuan-Chi
;
Shuai, Hong-Han
;
Lin, Hsin-Piao
;
Li, Chi-Yu
Future mobile communication networks require an Aerial Base Station (ABS) with fast mobility and long-term hovering capabilities. At present, unmanned aerial vehicles (UAV) or drones do not have long flight times and are mainly used for monitoring, surveillance, and image post-processing. On the other hand, the traditional airship is too large and not easy to take off and land. Therefore, we propose to develop an "Artificial Intelligence (AI) Drone-Cruiser" base station that can help 5G mobile communication systems and beyond quickly recover the network after a disaster and handle the instant communications by the flash crowd. The drone-cruiser base station can overcome the communications problem for three types of flash crowds, such as in stadiums, parades, and large plaza so that an appropriate number of aerial base stations can be accurately deployed to meet large and dynamic traffic demands. Artificial intelligence can solve these problems by analyzing the collected data, and then adjust the system parameters in the framework of Self-Organizing Network (SON) to achieve the goals of self-configuration, self-optimization, and self-healing. With the help of AI technologies, 5G networks can become more intelligent. This paper aims to provide a new type of service, On-Demand Aerial Base Station as a Service. This work needs to overcome the following live technical challenges: innovative design of drone-cruisers for the long-time hovering, crowd estimation and prediction, rapid 3D wireless channel learning and modeling, 3D placement of aerial base stations and the integration of WiFi front-haul and millimeter wave/WiGig back-haul networks.
Development of an air bleeding technique and specific duration to improve the CO tolerance of proton-exchange membrane fuel cells
(2009-08-01)
Chung, Chen-Chung
;
Chen, Chiun-Hsun
;
Weng, De-Zheng
;
機械工程學系
;
Department of Mechanical Engineering
This study investigated transient CO poisoning of a proton-exchange membrane fuel cell under either a fixed cell voltage or fixed current density. During CO poisoning tests, the cell performance decreases over time. Experiments were performed to identify which method yields better performance in CO poisoning tests. The results revealed that a change in cell voltage did not affect the stable polarization behavior after CO poisoning of the cell. On the other hand, a higher fixed current density yielded better tolerance of 52.7 ppm CO. The air bleeding technique was then applied using different timings for air introduction during CO poisoning tests. Air bleeding significantly improved the CO tolerance of the cell and recovered the performance after poisoning, regardless of the timing of air introduction. The effects of different anode catalyst materials on cell performance were also investigated during poisoning tests. Without air bleeding, a Pt-Ru alloy catalyst exhibited better CO tolerance than a pure Pt catalyst. However, the air bleeding technique can effectively increase the CO tolerance of cells regardless of the type of catalyst used. (C) 2009 Elsevier Ltd. All rights reserved.
Effect of actuation sequence on flow rates of peristaltic micropumps with PZT actuators
(2009-02-01)
Jang, Ling-Sheng
;
Shu, Kuan
;
Yu, Yung-Chiang
;
Li, Yuan-Jie
;
Chen, Chiun-Hsun
Many biomedical applications require the administration of drugs at a precise and preferably programmable rate. The flow rate generated by the peristaltic micropumps used in such applications depends on the actuation sequence. Accordingly, the current study performs an analytical and experimental investigation to determine the correlation between the dynamic response of the diaphragms in the micropump and the actuation sequence. A simple analytical model of a peristaltic micropump is established to analyze the shift in the resonant frequency of the diaphragms caused by the viscous damping effect. The analytical results show that this damping effect increases as the oscillation frequency of the diaphragm increases. A peristaltic micropump with three piezoelectric actuators is fabricated on a silicon substrate and is actuated using 2-, 3-, 4- and 6-phase actuation sequences via a driving system comprising a microprocessor and a phase controller. A series of experiments is conducted using de-ionized water as the working fluid to determine the diaphragm displacement and the flow rates induced by each of the different actuation sequences under phase frequencies ranging from 50 Hz to 1 MHz. The results show that the damping effect of actuation sequences influences diaphragm resonant frequency, which in turn affects the profiles of flow rates.
Effect of opposed flow on flame spread over a finite-length PMMA slab in a two-dimensional wind tunnel
(2007)
Chang, Wen-Kuei
;
Chen, Chiun-Hsun
;
機械工程學系
;
Department of Mechanical Engineering
The ignition delay and subsequent downward flame spread over a finite-length PMMA slab with the effect of radiation included in a two-dimensional wind tunnel are investigated using the opposed flow velocity as a parameter. The gas and solid phase temperatures, preheat length and heat flux are considered in order to examine the flame ignition and spread characteristics. The numerical results reveal that the ignition delay time increases with the opposed flow velocity. However, the flame spread rate varies with the opposed flow velocity in a non-monotonic manner that can be identified as two distinct regimes with a peak value in between. The flame spread rate reaches a maximum at V-g = 32 cm/s, and then falls, regardless of whether the flow velocity is increasing or decreasing. For V-g < 32 cm/s, the flame behaviors are dominated by oxygen transport. For V-g > 32 cm/s, the flame stretch effect controls the flame behavior. Additionally, this work demonstrates that the effect of radiation delays the flame ignition and reduces both the flame strength and the corresponding spread rate. The effects of the opposed flow temperature and thickness of the solid fuel are also investigated. The predicted results indicate that a higher opposed flow temperature or a thinner solid fuel facilitates the ignition and accelerates flame spread. The effect of opposed flow velocity eventually overcomes that of opposed flow temperature as the flow speed is further increased.
Electricity Generation Using Biogas From Swine Manure for Farm Power Requirement
(2015-01-01)
Chang, Chia-Wei
;
Lee, Tsung-Han
;
Lin, Wei-Tsung
;
Chen, Chiun-Hsun
;
機械工程學系
This study conducted 30 kW-generator experiments at a small biogas plant on a swine farm to serve as a preliminary study for the construction of a 300-kW power plant for a larger scale biogas plant in the near future. The experimental results showed that the optimum biogas flow rate for the engine was around 240 to 260 L/min, and the maximum power generation, the corresponding thermal efficiency, and the percentage of consumed CH4 were 26.8 kW, 28.7%, and 95.4%, respectively, at a biogas supply rate of 260 L/min. With 3% oxygen-enriched air, the maximum power generation, thermal efficiency, and percentage of consumed CH4 increased up to 28.2 kW, 30.2%, and approximately 100%, respectively, for a biogas supply rate of 260 L/min, and the engine can operate normally at a lower limited fuel supply rate of 220 L/min. The heat exchanger could recover 923 kJ/min of heat from the flue gas, leading to an overall efficiency of 47.3%, at a biogas supply rate of 240 L/min. With the total swine population (around 4.3 million heads) from the farm scale of over 1,000 heads of pigs in Taiwan, the estimation, based on the data obtained from this study, shows the economic benefits of using biogas, including an annual electricity generation of 2.67 x 10(8) kWh(e) (corresponding to electricity charge savings of US$ 26.7 million), where natural gas charge savings total US$ 8.7 million, and the carbon dioxide reduction totals 180,000 tons.
Encapsulated droplets with metered and removable oil shells by electrowetting and dielectrophoresis
(2011)
Fan, Shih-Kang
;
Hsu, Yao-Wen
;
Chen, Chiun-Hsun
;
機械工程學系
;
材料科學與工程學系
A water-core and oil-shell encapsulated droplet exhibits several advantages including enhanced fluidic manipulation, reduced biofouling, decreased evaporation, and simplified device packaging. However, obtaining the encapsulated droplet with an adjustable water-to-oil volume ratio and a further removable oil shell is not possible by reported techniques using manual pipetting or droplet splitting. We report a parallel-plate device capable of generation, encapsulation, rinsing, and emersion of water and/or oil droplets to achieve three major aims. The first aim of our experiments was to form encapsulated droplets by merging electrowetting-driven water droplets and dielectrophoresis-actuated oil droplets whose volumes were precisely controlled. 25 nL water droplets and 2.5 nL non-volatile silicone oil droplets with various viscosities (10, 100, and 1000 cSt) were individually created from their reservoirs to form encapsulated droplets holding different water-to-oil volume ratios of 10 : 1 and 2 : 1. Secondly, the driving voltages, evaporation rates, and biofouling of the precise encapsulated droplets were measured. Compared with the bare and immersed droplets, we found the encapsulated droplets (oil shells with lower viscosities and larger volumes) were driven at a smaller voltage or for a wider velocity range. In the dynamic evaporation tests, at a temperature of 20 +/- 1 degrees C and relative humidity of 45 +/- 3%, 10 cSt 10 : 1 and 2 : 1 encapsulated droplets were moved at the velocity of 0.25 mm s(-1) for 22 and 35 min until losing 16.6 and 17.5% water, respectively, while bare droplets followed the driving signal for only 6 min when 11.4% water was lost. Evaporation was further diminished at the rate of 0.04% min(-1) for a carefully positioned stationary encapsulated droplet. Biofouling of 5 mu g ml(-1) FITC-BSA solution was found to be eliminated by the encapsulated droplet from the fluorescent images. The third aim of our research was to remove the oil shell by dissolving it in an on-chip rinsing reservoir containing hexane. After emersion from the rinsing reservoir, the bare droplet was restored as hexane rapidly evaporated. Removal of the oil shell would not only increase the evaporation of the core droplet when necessary, but also enhance the signal-to-noise ratio in the following detection steps.
Evaluating the performance of a portable water-mist fire extinguishing system with additives
(2008-11-01)
Chang, Wen-Yao
;
Fu, Ping-Kun
;
Chen, Chiun-Hsun
;
Shu, Yi-Liang
;
機械工程學系
This study investigates how high-pressure water-mist system discharge methodologies influence the fire extinction performance for pan pool fires and the corresponding mechanisms of restraining fire. The fire source is a pool-fire burner. Fine water spray is injected using a portable device. The additive in the water-mist is neither toxic nor corrosive. All the tests are regarded as fuel controlled. The fire test parameters are fuel type, nozzle discharge angle, and additive solution volume. The fuels used are heptane, gasoline, and diesel. Nozzle discharge angles are 30, 45, and 60 degrees with respect to the ground. Additive solution volumes are 0% (pure water), 3, 6, and 10%. Test results indicate that the nozzle discharge angle and additive solution volume in a water-mist fire extinction system play a significant role. Fire extinguishing efficiency is influenced by mist effects and the additive. Furthermore, the water-mist system can reduce radiation and can provide good protection for operators using portable fire extinguishing equipment. Copyright (C) 2008 John Wiley & Sons, Ltd.
Experimental and numerical studies of micro PEM fuel cell
(2011-10-01)
Peng, Rong-Gui
;
Chung, Chen-Chung
;
Chen, Chiun-Hsun
;
機械工程學系
;
Department of Mechanical Engineering
A single micro proton exchange membrane fuel cell (PEMFC) has been produced using Micro-electro-mechanical systems (MEMS) technology with the active area of 2.5 cm(2) and channel depth of about 500 mu m. A theoretical analysis is performed in this study for a novel MEMS-based design of a micro PEMFC. The model consists of the conservation equations of mass, momentum, species and electric current in a fully integrated finite-volume solver using the CFD-ACE+ commercial code. The polarization curves of simulation are well correlated with experimental data. Three-dimensional simulations are carried out to treat prediction and analysis of micro PEMFC temperature, current density and water distributions in two different fuel flow rates (15 cm(3)/min and 40 cm(3)/min). Simulation results show that temperature distribution within the micro PEMFC is affected by water distribution in the membrane and indicate that low and uniform temperature distribution in the membrane at low fuel flow rates leads to increased membrane water distribution and obtains superior micro PEMFC current density distribution under 0.4V operating voltage. Model predictions are well within those known for experimental mechanism phenomena.
Fire suppression performance of water mist under diverse desmoking and ventilation conditions
(2020-01-01)
Liu, Wei-Yi
;
Chen, Chiun-Hsun
;
Shu, Yi-Liang
;
Chen, Wei-Ting
;
Shu, Chi-Min
This paper described full-scale tests of water mist fire suppression system under forced desmoking conditions. Pool fire was effectively suppressed in 25.0 and 37.0 s for 1,500.0 (test 1) and 3,000.0 (test 2) mL of oil with no ventilation, respectively. Moreover, under ventilation rates of 50.0 and 75.0 m(3)/min, the suppression time were lengthened to 54.0 s (test 1) and 202.0 s (test 2), and 102.0 s (test 1) and 222.0 s (test 2), correspondingly. However, the smoke exhaust had a strong effect on the water mist to result in fire could not extinguish, when the ventilation rate increased to 120.0 m(3)/min. The temperature distribution during the early period in the scenario of no ventilation has a higher magnitude than those scenarios of 50.0, 75.0, and 120.0 m(3)/min, because combustion proceeds smoothly to result in temperature increased rapidly at no ventilation. Furthermore, similar results presented in smoke concentration distribution at four scenarios (0, 50.0, 75.0, and 120.0 m(3)/min), and combustion occurred steadily at no ventilation to result in more smoke during the early period. This study employed a computer modeling to verify water mist system in a compartment space and determine how the water mist system could be optimized. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
High-efficiency combustion of natural gas with 21-30% oxygen-enriched air
(2010-09-01)
Wu, Kuo-Kuang
;
Chang, Yu-Cheng
;
Chen, Chiun-Hsun
;
Chen, Young-Da
;
機械工程學系
This investigation was aimed at studying the influence of 21-30% oxygen concentration on the heating rate, emissions, temperature distributions, and fuel (natural gas) consumption in the heating and furnace-temperature fixing tests. Increase in the oxygen concentration led to a more rapid heating rate and lesser fuel consumption due to lower levels of the inert gas (N(2)). When the oxygen concentration was increased from 21% to 30%, the heating rate was increased by 53.6% in the heating test and the fuel consumption was reduced by 26.1% in the furnace-temperature fixing test. Higher oxygen concentrations yielded higher flame temperature; hence, the NO(x) emission increased with increasing oxygen concentration. However, the increase of NO(x) emission in the furnace-temperature fixing test was less than that in the heating test. Moreover, the NO(x) emission was more sensitive to the excess oxygen at higher oxygen levels. The CO(2) concentration in the flue gas increased linearly with the oxygen concentration. Additionally, the temperature distributions became progressively nonuniform with increasing oxygen concentration because the convective heat transfer coefficient was altered. (C) 2010 Elsevier Ltd. All rights reserved.
Improvement of CO tolerance of proton exchange membrane fuel cell (PEMFC) by an air-bleeding technique
(2005)
Chung, Chen-Chung
;
Chen, Chiun-Hsun
;
Lin, Hsiang-Hui
;
Yan, Yi-Yie
;
機械工程學系
The investigation studies improving PEMFC carbon monoxide by a periodic air dosing. The carbon monoxide in the fuel gas leads to a significant loss in power density due to CO poisoning in the anode. The method involves bleeding air into the anode fuel stream (H-2-CO), which contains CO in various concentrations (20, 52.7, 100 ppm). In the transient CO poisoning test, air-bleeding is performed for four different periodic air dosing and cell voltage is fixed at 0.6 V. The result of a dosing of air during 10 sec in intervals of 10 sec is similar to that of continuous air-bleeding except 100 ppm CO. The CO tolerance of the fuel cell and cell performance recovery from poisoning can be improved by air-bleeding.
Improvement of CO tolerance of proton exchange membrane fuel cell by an air-bleeding technique
(2008-02-01)
Chen, Chiun-Hsun
;
Chung, Chen-Chung
;
Lin, Hsiang-Hui
;
Yan, Yi-Yie
;
機械工程學系
This study investigates the improvement of proton exchange membrane fuel cell (PEMFC) carbon monoxide by periodic air dosing. The carbon monoxide in the fuel gas leads to a significant loss in power. density due to CO poisoning in the anode. The method involves bleeding air into the anode fuel stream (H(2)-CO), which contains CO in various concentrations (20 ppm, 52.7 ppm, and 100 ppm). In the transient CO poisoning test, air bleeding is performed for four different periodic air dosing and cell voltage is fixed at 0.6 V. The result of a dosing of air for 10 s in intervals of 10 s is similar to that of continuous air bleeding except for 100 ppm CO. The CO tolerance of the fuel cell and cell performance recovery from poisoning can be improved by air bleeding.
Investigation of cell operation conditions for co tolerance improvement of PEMFC
(2007-12-01)
Chung, Chen-Chung
;
Chen, Chiun-Hsun
;
Weng, Der-Cheng
;
Yan, Yi-Yie
;
Lin, Hsiang-Hui
The investigation is to experimentally study the transient CO poisoning test with different cell operation conditions. One is fixing the cell voltage and the other is fixing the current density. In the former condition, the voltages are fixed at 0.5, 0.6, 0.7V, respectively, whereas the current densities are fixed at 600, 1000, 1200mA/cm(2), respectively, in the latter one. In the transient poisoning test, the cell performance will be declined with time. The poisoned polarization curves are determined as soon as the performance subjected to CO poisoning reaches a steady state. Then, it will determine which one has a better performance in CO poisoning test and find out the difference between these two methods. With fixed cell voltage to perform transient CO poisoning test, it indicates that changing cell voltage cannot transform the stable poisoned polarization behaviors, whereas with fixed current density, it can get a better recovery performance at a fixed CO concentration (52.7ppm).
Lipid accumulation and CO(2) utilization of Nannochloropsis oculata in response to CO(2) aeration
(2009-01-01)
Chiu, Sheng-Yi
;
Kao, Chien-Ya
;
Tsai, Ming-Ta
;
Ong, Seow-Chin
;
Chen, Chiun-Hsun
In order to produce microalgal lipids that can be transformed to biodiesel fuel, effects of concentration of CO(2) aeration on the biomass production and lipid accumulation of Nannochloropsis oculata in a semicontinuous culture were investigated in this study. Lipid content of N. oculata cells at different growth phases was also explored. The results showed that the lipid accumulation from logarithmic phase to stationary phase of N. oculata NCTU-3 was significantly increased from 30.8% to 50.4%. In the microalgal cultures aerated with 2%, 5%, 10% and 15% CO(2), the maximal biomass and lipid productivity in the semicontinuous system were 0.480 and 0.142 g L(-1) d(-1) with 2% CO(2) aeration, respectively. Even the N. oculata NCTU-3 cultured in the semicontinuous system aerated with 15% CO(2), the biomass and lipid productivity could reach to 0.372 and 0.084 g L(-1) d(-1), respectively. In the comparison of productive efficiencies, the semicontinuous system was operated with two culture approaches over 12 d. The biomass and lipid productivity of N. oculata NCTU-3 were 0.497 and 0.151 g L(-1) d(-1) in one-day replacement (half broth was replaced each day), and were 0.296 and 0.121 g L(-1) d(-1) in three-day replacement (three fifth broth was replaced every 3 d), respectively. To optimize the condition for long-term biomass and lipid yield from N. oculata NCTU-3, this microalga was suggested to grow in the semicontinuous system aerated with 2% CO(2) and operated by one-day replacement. (C) 2008 Elsevier Ltd. All rights reserved.