13 results on '"Chi-Hwa, Wang"'
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2. Extended exergy accounting theory to design waste-to-energy management system under uncertainty
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Jianrui Liu, Harn Wei Kua, Chi-Hwa Wang, Yen Wah Tong, Jingxin Zhang, and Yinghong Peng
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General Energy ,Mechanical Engineering ,Building and Construction ,Electrical and Electronic Engineering ,Pollution ,Industrial and Manufacturing Engineering ,Civil and Structural Engineering - Published
- 2023
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3. Analysis on solar energy powered cooling system based on desiccant coated heat exchanger using metal-organic framework
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Zhoufeng Bian, Tianshu Ge, Yuting Dai, Chi-Hwa Wang, Sibudjing Kawi, and F. Xu
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Desiccant ,Materials science ,business.industry ,020209 energy ,Mechanical Engineering ,Refrigeration ,02 engineering and technology ,Building and Construction ,Solar energy ,Pollution ,Industrial and Manufacturing Engineering ,General Energy ,020401 chemical engineering ,Chemical engineering ,Heat exchanger ,0202 electrical engineering, electronic engineering, information engineering ,Water cooling ,Relative humidity ,0204 chemical engineering ,Electrical and Electronic Engineering ,Vapor-compression refrigeration ,business ,Water vapor ,Civil and Structural Engineering - Abstract
The solar powered cooling system based on desiccant coated heat exchanger (DCHE) is an alternative to traditional vapor compression cooling system (VCCS) due to its energy-saving and eco-friendliness. To obtain improved performance, high-porosity Metal-Organic Framework (MOF) is introduced as desiccant. In our study, Cu-BTC (HKUST-1) was fabricated and certified with high purity and good crystallization by X-ray diffraction (XRD). N2 isotherm adsorption-desorption properties of MOF were investigated. Results show that MOF has co-existence of micropores and mesopores with relatively large specific surface area and pore volume. Water vapor isotherm adsorption of MOF and type B silica gel (SGB) was conducted. Isotherms indicate that moisture uptake of MOF is higher than that of SGB at low relative humidity. A dynamic mathematical model of this system was established. The solar performance was evaluated firstly. Results suggest that solar collector can provide 52.5–80.4 °C hot water from 9:00 to 19:00. Then the simulation was conducted under American Air-conditioning and Refrigeration Institute (ARI) summer and Shanghai August conditions. Results exhibit that MOF coated heat exchanger (MCHE) has more significant enhancement of dehumidification performance than SGB coated heat exchanger (SCHE) with increased regeneration temperature and MCHE is more suitable for application under ARI summer condition.
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- 2019
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4. Performance analysis of a biomass gasification-based CCHP system integrated with variable-effect LiBr-H2O absorption cooling and desiccant dehumidification
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Yanjun Dai, Tianshu Ge, Xian Li, Xiang Kan, Chi-Hwa Wang, Yao Zhao, and Xiangyu Sun
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Desiccant ,Electrical load ,020209 energy ,02 engineering and technology ,Industrial and Manufacturing Engineering ,law.invention ,020401 chemical engineering ,Natural gas ,law ,Heat exchanger ,0202 electrical engineering, electronic engineering, information engineering ,0204 chemical engineering ,Electrical and Electronic Engineering ,Process engineering ,Civil and Structural Engineering ,Wood gas generator ,business.industry ,Mechanical Engineering ,Building and Construction ,Pollution ,General Energy ,Internal combustion engine ,Absorption refrigerator ,Gas engine ,Environmental science ,business - Abstract
A novel biomass gasification-based combined cooling, heat and power (CCHP) system, which is composed of a gas-fueled internal combustion engine, variable-effect LiBr-H2O absorption cooling, and dehumidification air-conditioning with desiccant coated heat exchangers, was introduced. The temperature and humidity independent strategy was applied in the gasification-based CCHP system to enhance cooling production, in which the variable-effect absorption chiller and desiccant dehumidification air-conditioning were driven by the exhaust heat and jacket heat of the gas engine based on energy cascade, respectively. The operation strategy of the system followed the electric load. Validated by experimental data, a zero-dimensional code of the gasifier with Gibbs free energy minimization, an artificial neural network model of the variable-effect absorption chiller, and a 1-D dynamic model of the dehumidification air-conditioning, were built with reasonable deviations. The results of energetic, economic, and environmental (3E) analyses for the proposed gasification-based CCHP systems that were applied in two different buildings indicate that woody chips are the most favorable feedstock under the climate of Singapore. The total performance is more sensitive to the feedstock cost than to the natural gas cost. This work enables to contribute valuable data to the practical application of the biomass gasification-based CCHP system in Singapore's building sector.
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- 2019
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5. CO2 gasification of woody biomass: Experimental study from a lab-scale reactor to a small-scale autothermal gasifier
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Zhiyi Yao, Ye Shen, Chi-Hwa Wang, Xian Li, and Xiaoqiang Cui
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Wood gas generator ,Carbon dioxide reforming ,020209 energy ,Mechanical Engineering ,Biomass ,02 engineering and technology ,Building and Construction ,Raw material ,Pulp and paper industry ,Pollution ,Industrial and Manufacturing Engineering ,Methane ,chemistry.chemical_compound ,Boudouard reaction ,General Energy ,020401 chemical engineering ,chemistry ,Bioenergy ,Biochar ,0202 electrical engineering, electronic engineering, information engineering ,Environmental science ,0204 chemical engineering ,Electrical and Electronic Engineering ,Civil and Structural Engineering - Abstract
Rapid depletion of fossil fuel and CO2 mitigation are two major challenges in the modern society. CO2 gasification of carbon-neutral biomass could be an attractive technology to cope up these two emerging problems. Replacing conventional gasifying agent air with CO2 could reduce the fraction of undesired N2 in the gas products because CO2 behaves as inert gasifying agent under low temperature and could be converted to CO at high temperature range. However, most researches on CO2 gasification are limited at the lab-scale level due to the endothermic feature of Boudouard reaction. In this work, a feasibility study of small-scale autothermal gasification using 15% CO2 and 85% air was conducted and compared with traditional air gasification. Prior to that, a lab-scale study of gasification behaviors, under N2, air and CO2 agents, were performed. It was found that using CO2 as gasification oxidant could produce comparable energy (6.67 kJ/g feedstock) to air gasification (7.45 kJ/g feedstock) at equivalent condition (800 °C, 40 min). The pH of biochar obtained under CO2 condition at 800 °C was measured to be 10.63 while the pH of biochar derived by air gasification at the same temperature could reach 12.32. In addition, a small-scale gasification experiment with 15% CO2 addition was successfully conducted in a downdraft autothermal reactor. The results showed CO production was greatly enhanced while CH4 generation was suppressed owing to Boudouard reaction and CO2 dry reforming. Cold gas efficiency and carbon conversion efficiency were both enhanced by 5.8% and 6%, respectively, with CO2 addition. Meanwhile, particulate matters (PM) emitted from both air gasification and 15% CO2 gasification experiments were measured. It was found that under the same equivalence ratio (ER), 75.4% less particle number concentration was emitted during 15% CO2 gasification compared to air gasification.
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- 2019
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6. Evaluation of a combined cooling, heating, and power system based on biomass gasification in different climate zones in the U.S
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Chao Li, Ye Shen, Jingyi Wu, Yuting Dai, Chi-Hwa Wang, and Xiang Kan
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Chiller ,Electrical load ,business.industry ,020209 energy ,Mechanical Engineering ,Mode (statistics) ,Biomass ,02 engineering and technology ,Building and Construction ,Grid ,Pollution ,Industrial and Manufacturing Engineering ,Automotive engineering ,Electric power system ,General Energy ,020401 chemical engineering ,0202 electrical engineering, electronic engineering, information engineering ,Environmental science ,Electricity ,Sensitivity (control systems) ,0204 chemical engineering ,Electrical and Electronic Engineering ,business ,Civil and Structural Engineering - Abstract
A combined cooling, heating, and power system based on biomass gasification is modeled via experiment and its performance is evaluated. The system operation is simulated using load data of small offices located in different climate zones in the U.S. The operation strategy comprises following the electric load (FEL) and following the thermal load (FTL). Based on the operation data, energetic, economic, environmental, and overall performances of the system are evaluated. Results show that the annual integrated performance (Swhole) of the system ranges from 0.229 to 0.473 in FEL mode and from 0.067 to 0.457 in FTL mode, in different regions. The system has a better performance in FEL mode, and is more attractive to install in the regions with more thermal load. Furthermore, the match degree of heat to power ratio between load and output also has an effect on the system performance. Sensitivity analysis shows that the system performance is more sensitive to the cost of biomass, cost of grid electricity and CO2 emission rate of the grid in both modes, and COP of thermally activated chiller in FTL mode. By changing the above-mentioned parameters, Swhole can be improved by up to 13.7%, 8.2%, 11.0%, and 19.7% respectively.
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- 2018
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7. Thermodynamic assessment of a solar/autothermal hybrid gasification CCHP system with an indirectly radiative reactor
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Chi-Hwa Wang, Xian Li, Yanjun Dai, Ye Shen, Timothy Kurnia Hardiman, and Xiang Kan
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Gibbs free energy minimization ,Primary energy ,Wood gas generator ,Chemistry ,020209 energy ,Mechanical Engineering ,Thermodynamics ,02 engineering and technology ,Building and Construction ,Pollution ,Industrial and Manufacturing Engineering ,Continuous production ,Volumetric flow rate ,Power (physics) ,General Energy ,0202 electrical engineering, electronic engineering, information engineering ,Radiative transfer ,Electrical and Electronic Engineering ,Civil and Structural Engineering ,Syngas - Abstract
The solar/autothermal hybrid gasifier (SAHG) is an attractive approach to provide continuous production of the syngas via coupling autothermal and solar gasification together, where the SAHG mainly includes fully solar, hybrid, and fully autothermal modes. An ICE CCHP system driven by the SAHG with an indirectly irradiative two-cavity reactor introduced conceptually and investigated thermodynamically. Considering the effects of solar flux inputs and various reactant ratios, a zero-dimensional steady-state model of the SAHG was established by using Gibbs free energy minimization, and was validated with the reported data. The optimal steam-to-feedstock and oxygen-to-feedstock ratios has been achieved based on the restrictions of temperature over 1000 K and minimization of steam input. The results of two consecutive days indicate mole flow rates of H 2 and CO were increased by over 38.8% and 11.8%, respectively, leading to an increment in LHV s by 51.7%. An increment in primary energy ratio by 11.5% can be achieved by using the SAHG-CCHP system. The yearly assessment of the SAHG-CCHP system shows that the yearly average increments in heat, power, and cooling for the SAHG system were reached by 19.5%, 23.8%, and 4.5%, respectively. A yearly average increment of 14.2% in primary energy ratio can be obtained under the solar radiation condition of Singapore.
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- 2018
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8. Multi-criteria decision making of biomass gasification-based cogeneration systems with heat storage and solid dehumidification of desiccant coated heat exchangers
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Xiangyu Sun, Clive Chong, Yanjun Dai, Xian Li, Yao Zhao, Jialing Chen, and Chi-Hwa Wang
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Payback period ,Waste management ,020209 energy ,Mechanical Engineering ,02 engineering and technology ,Building and Construction ,Sensible heat ,Thermal energy storage ,Pollution ,Industrial and Manufacturing Engineering ,Heat capacity rate ,Cogeneration ,General Energy ,020401 chemical engineering ,Heat recovery ventilation ,Heat exchanger ,0202 electrical engineering, electronic engineering, information engineering ,Environmental science ,Electric power ,0204 chemical engineering ,Electrical and Electronic Engineering ,Civil and Structural Engineering - Abstract
Biomass gasification-based cogeneration systems integrated with dehumidification of desiccant coated heat exchangers, covering the cogeneration system inclusive of sensible heat storage and internal heat recovery (SC-1), the cogeneration system inclusive of sensible heat storage (SC-2), and the cogeneration system exclusive of heat storage and internal heat recovery (SC-3), are introduced and comparatively investigated on the energetic and economic performances. The developed models of the cogeneration systems are embedded into a multi-criteria decision-making framework to find the optimal system configuration and parameters. The most favorable scheme (SC-1) – that reaches an overall energy efficiency of 0.963, net present value of 1,429,400 USD, levelized total cost of 646,835 USD/year, payback period of 3.7, heat storage tank of 7 m3, heat recovery tank of 2.1 m3, jacket heat rate of 290 kW, and nominal electric power of 629 kWe – is determined. The sensitivity analysis indicates that the net present value is most sensitive to the electricity tariffs, followed by the biomass feedstock price and the selling price of electricity to utility grid. The overall energy efficiency of 0.81–0.995, the net present value of −470,400–6,166,900 USD, and the payback period of 1.5–13.1 were achieved against the price variation range of ±80%.
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- 2021
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9. Life cycle assessment of a sewage sludge and woody biomass co-gasification system
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Zhiyi Yao, Tobias Massier, Siming You, Chi-Hwa Wang, Srikkanth Ramachandran, and Ulrich Stimming
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Municipal solid waste ,020209 energy ,Biomass ,Sewage ,02 engineering and technology ,010501 environmental sciences ,01 natural sciences ,Industrial and Manufacturing Engineering ,Bioenergy ,Biochar ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,0105 earth and related environmental sciences ,Civil and Structural Engineering ,Waste management ,business.industry ,Mechanical Engineering ,Environmental engineering ,Building and Construction ,Pollution ,Incineration ,Waste-to-energy ,General Energy ,Environmental science ,business ,Sludge - Abstract
Replacing a part of energy derived from fossil fuels with bioenergy derived from solid waste streams may be a promising method to tackle the dual crisis of increasing waste pile-up and global climate change. In this study we propose a decentralised sewage sludge and woody biomass co-gasification system for Singapore. We evaluate the greenhouse gas emission of the proposed system and compare it to the existing system through life cycle assessment. The proposed system is expected to provide a net annual emission reduction of 137.0–164.1 kilotonnes of CO 2 eq. Increase in electricity recovery, carbon sequestration in the biochar produced and the avoidance of the use of supplementary fuel for sewage sludge incineration are the major contributors for the emission reduction. The proposed system is able to increase the net electricity production from sewage sludge and woody biomass by 3–24%. This could lead to an annual increase in electricity recovery of 12.1–74.8 GWh. It is estimated that the proposed system can produce 34 kilotonnes of biochar annually. It is found that decentralisation helps to reduce the annual tonne-km driven by 4.23 million tonne-km which could decrease the number of on-road vehicles required for waste handling.
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- 2017
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10. Anaerobic digestion and gasification hybrid system for potential energy recovery from yard waste and woody biomass
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Yanjun Dai, Xiang Kan, Zhiyi Yao, Yen Wah Tong, Chi-Hwa Wang, and Wangliang Li
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Energy recovery ,Moisture ,Waste management ,020209 energy ,Mechanical Engineering ,02 engineering and technology ,Building and Construction ,010501 environmental sciences ,01 natural sciences ,Pollution ,Industrial and Manufacturing Engineering ,Anaerobic digestion ,General Energy ,Biogas ,Hybrid system ,0202 electrical engineering, electronic engineering, information engineering ,Environmental science ,Electrical and Electronic Engineering ,Water content ,0105 earth and related environmental sciences ,Civil and Structural Engineering ,Efficient energy use ,Syngas - Abstract
There is a rapid growing interest in using biomass as an alternative source for clean and sustainable energy production. In this work, a hybrid system was developed to combine anaerobic digestion (AD) and gasification for energy recovery from yard waste and woody biomass. The feasibility of the proposed hybrid system was validated experimentally and numerically and the energy efficiency was maximized by varying energy input in the drying process. The experiments were performed in two stages. At the first stage, AD of yard waste was conducted by mixing with anaerobic sludge. At the second stage, co-gasification was added as post-treatment for the AD residue for syngas production. The co-gasification experiments of AD residue and woody biomass were conducted at varying mixing ratios and varying moisture contents of AD residue. Optimal energy efficiency was found to be 70.8% at mixing ratio of 20 wt% AD residue with 30 wt% moisture content. Two kinetic models were then adapted for prediction of biogas produced in AD process and syngas produced in gasification process, respectively. Both experimental and numerical results showed that full utilization of biomass could be realized to produce energy through the combination of these two technologies.
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- 2017
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11. Solar-driven thermochemical redox cycles of ZrO2 supported NiFe2O4 for CO2 reduction into chemical energy
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Bachirou Guene Lougou, Boshu Jiang, Fuqiang Wang, Azeem Mustafa, Hao Zhang, Yong Shuai, Jiupeng Zhao, and Chi-Hwa Wang
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Energy Dispersive Spectrometer ,Thermogravimetric analysis ,Materials science ,020209 energy ,Mechanical Engineering ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,Building and Construction ,Pollution ,Redox ,Oxygen ,Industrial and Manufacturing Engineering ,Energy storage ,Chemical energy ,General Energy ,020401 chemical engineering ,chemistry ,Yield (chemistry) ,0202 electrical engineering, electronic engineering, information engineering ,0204 chemical engineering ,Electrical and Electronic Engineering ,Chemical composition ,Civil and Structural Engineering - Abstract
In this study, solar thermal power coupled with a direct irradiated solar thermochemical reactor using porous-medium NiFe2O4@ZrO2 oxygen exchange material was investigated by combining experiments to the numerical models. The ability of ZrO2, NiFe2O4, and NiFe2O4@ZrO2 to release/uptake O2 and their CO2-splitting characteristics are analyzed by the thermogravimetric analyzer (TGA) and the microstructural changes and chemical composition of NiFe2O4@ZrO2 are examined by scanning electron microscopy (SEM) and x-ray energy dispersive spectrometer (EDS). The experiment performed with a redox thermochemical reactor under a high-flux solar spectrum resulted in a total of 337.89 mL of CO collected during 46 min of CO2-splitting over NiFe2O4@ZrO2 redox material. Higher CO2-splitting activity of NiFe2O4 resulting in 186.545 μmol/g and 130.707 μmol/g of CO yield at 1293-795 °C and 100 sccm of CO2 flow rate were obtained by TGA at the first and second cycle, respectively. The results of both experiments showed significant CO yield at the early stages of oxygen carriers’ re-oxidation with CO2. This study provided important results that could have significant contributions to the solar thermochemical energy storage and CO2 chemical transformation processes.
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- 2021
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12. Advanced technologies on sustainable energy and environment: SET2016 virtual special issue
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Ruzhu Wang, Xian Li, Chi-Hwa Wang, Yen Wah Tong, and Kai-Chee Loh
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Architectural engineering ,020209 energy ,Mechanical Engineering ,02 engineering and technology ,Building and Construction ,Pollution ,Industrial and Manufacturing Engineering ,Sustainable energy ,General Energy ,020401 chemical engineering ,0202 electrical engineering, electronic engineering, information engineering ,Environmental science ,0204 chemical engineering ,Electrical and Electronic Engineering ,Civil and Structural Engineering - Published
- 2017
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13. Corrigendum'Performance analysis of a biomass gasification-based CCHP system integrated with variable-effect LiBr-H2O absorption cooling and desiccant dehumidification'[Energy 176 (2019) 961–979]
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Chi-Hwa Wang, Xiang Kan, Xiangyu Sun, Xian Li, Yanjun Dai, Tianshu Ge, and Yao Zhao
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Desiccant ,business.industry ,Mechanical Engineering ,Building and Construction ,Pollution ,Industrial and Manufacturing Engineering ,law.invention ,Variable (computer science) ,General Energy ,law ,Absorption refrigerator ,Environmental science ,Electrical and Electronic Engineering ,Biomass gasification ,Process engineering ,business ,Energy (signal processing) ,Civil and Structural Engineering - Published
- 2019
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