Pub Date : 2021-04-15DOI: 10.33430/V28N1THIE-2020-0005
H. F. Chow
This paper proposes and discusses the viability of a short-term grid maximum demand forecasting model combining autoregressive integrated moving average with regressors (ARIMAX) and support vector regression (SVR). Grid demand forecasting is essential to generation unit scheduling, maintenance planning and system security. Traditionally, grid demand is forecasted using multivariate linear regression models with parameters adjusted to past data. A disadvantage of the linear regression model is that the parameters require regular adjustment, otherwise the prediction accuracy will deteriorate over time. With recent advances in the field of machine learning and lower computational costs, the usage of machine learning in the power industry becomes increasingly practicable. The proposed model is a machine learning model that combines ARIMAX and SVR to exploit their respective effectiveness in predicting linear and non-linear data. In contrast to linear regression models, the machine learning model automatically updates itself when new data is included. The hybrid model is benchmarked against other forecasting models and demonstrated a marked improvement in accuracy, achieving RMSE of 67.7MW and MAPE of 1.32% in a seven-day forecast.
{"title":"Short-term electricity grid maximum demand forecasting with the ARIMAX-SVR Machine Learning Hybrid Model","authors":"H. F. Chow","doi":"10.33430/V28N1THIE-2020-0005","DOIUrl":"https://doi.org/10.33430/V28N1THIE-2020-0005","url":null,"abstract":"This paper proposes and discusses the viability of a short-term grid maximum demand forecasting model combining autoregressive integrated moving average with regressors (ARIMAX) and support vector regression (SVR). Grid demand forecasting is essential to generation unit scheduling, maintenance planning and system security. Traditionally, grid demand is forecasted using multivariate linear regression models with parameters adjusted to past data. A disadvantage of the linear regression model is that the parameters require regular adjustment, otherwise the prediction accuracy will deteriorate over time. With recent advances in the field of machine learning and lower computational costs, the usage of machine learning in the power industry becomes increasingly practicable. The proposed model is a machine learning model that combines ARIMAX and SVR to exploit their respective effectiveness in predicting linear and non-linear data. In contrast to linear regression models, the machine learning model automatically updates itself when new data is included. The hybrid model is benchmarked against other forecasting models and demonstrated a marked improvement in accuracy, achieving RMSE of 67.7MW and MAPE of 1.32% in a seven-day forecast.","PeriodicalId":35587,"journal":{"name":"Transactions Hong Kong Institution of Engineers","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45539913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-15DOI: 10.33430/V28N1THIE-2020-0044
A. So, K. Lam, A. C. T. Kong, Jeff H. Tse
Machine brakes and safety gears of traction lifts are two critical components of the biggest safety concerns, as the main braking system and redundant fail-safe mechanism respectively stop and hold lift cars from unintended car movement, overspeed or under a free-fall condition during emergency. There are challenges of routine maintenance on how to continually verify the effectiveness of them to mitigate risk potentials of equipment failure. This pilot study intends to design, implement and test low-cost, non-intrusive and on-line prototype testers with the aid of sensors for real-time monitoring of critical parameters of these safety devices. Critical parameters that are measurable include real-time variations of brake lining temperature, brake solenoid current, vibrational patterns of brake arms and lift car, position of lift car, and the actuating status of safety gears. Critical parameters after processing include a newly defined energy of brake arm operation and estimated deceleration rate of a fully loaded car by safety gears operation on an unloaded car. Early signs of abnormalities of these two safety devices can be detected before they fail. Additionally, the prototype testers can facilitate more frequent unloaded full-speed testing of safety gears to verify the effectiveness. The proof-of-concept prototype could be a quick monitoring alternative to existing and new traction lift systems.
{"title":"Development of prototype machine brake and car safety gear testers for traction lift systems","authors":"A. So, K. Lam, A. C. T. Kong, Jeff H. Tse","doi":"10.33430/V28N1THIE-2020-0044","DOIUrl":"https://doi.org/10.33430/V28N1THIE-2020-0044","url":null,"abstract":"Machine brakes and safety gears of traction lifts are two critical components of the biggest safety concerns, as the main braking system and redundant fail-safe mechanism respectively stop and hold lift cars from unintended car movement, overspeed or under a free-fall condition during emergency. There are challenges of routine maintenance on how to continually verify the effectiveness of them to mitigate risk potentials of equipment failure. This pilot study intends to design, implement and test low-cost, non-intrusive and on-line prototype testers with the aid of sensors for real-time monitoring of critical parameters of these safety devices. Critical parameters that are measurable include real-time variations of brake lining temperature, brake solenoid current, vibrational patterns of brake arms and lift car, position of lift car, and the actuating status of safety gears. Critical parameters after processing include a newly defined energy of brake arm operation and estimated deceleration rate of a fully loaded car by safety gears operation on an unloaded car. Early signs of abnormalities of these two safety devices can be detected before they fail. Additionally, the prototype testers can facilitate more frequent unloaded full-speed testing of safety gears to verify the effectiveness. The proof-of-concept prototype could be a quick monitoring alternative to existing and new traction lift systems.","PeriodicalId":35587,"journal":{"name":"Transactions Hong Kong Institution of Engineers","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44175106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-15DOI: 10.33430/V28N1THIE-2020-0036
Anutosh Das, S. Kashem, M. Hasan
Agriculture, the main economic driver of Barind Tract, is highly dependent on groundwater for surface water paucity in the area. Notwithstanding, farmers use water capriciously due to its low price that makes a substantial drop in the water table. In this context, the research attempts to determine a market-based water pricing mechanism to encourage an optimal use of the scarce non-renewable resource. Required data was collected by questionnaire survey, Focus Group Discussion (FGD), Contingent Valuation Method, expert-opinion survey and subsequent literature works. The results reveal that depletion level has arrived at 20, 11, 7.5 feet in high, mid and low tract respectively over the last 22 years, which results in a number of economic-environmental externalities in the area. The research monetarily evaluated the cost of externalities and incorporated it with the marginal cost of extraction to increase efficiency of an existing pricing system. Regarding human reaction to price elasticity, the new price can be a reliable attempt to reduce an overconsumption pattern of water. Quantity of consumed water can be reduced to 14190.4 m3, 17759.59 m3 and 38510.6 m3 in a year in high, mid and low tract area respectively with its implementation. The research will serve as an initiative to conserve the valuable groundwater resource for future generations by managing consumer practice.
农业是巴林德地区的主要经济驱动力，由于该地区地表水缺乏，农业高度依赖地下水。尽管如此，由于水价低，导致地下水位大幅下降，农民们随意用水。在此背景下，本研究试图确定以市场为基础的水价机制，以鼓励对稀缺的不可再生资源的最佳利用。通过问卷调查、焦点小组讨论(Focus Group Discussion, FGD)、条件评估法(Contingent Valuation Method)、专家意见调查和后续的文献工作收集所需数据。结果表明，在过去的22年中，高、中、低流域的枯竭水平分别达到了20、11、7.5英尺，这导致了该地区的一些经济环境外部性。这项研究从货币上评价了外部性的成本，并将其与开采的边际成本结合起来，以提高现有定价制度的效率。就人类对价格弹性的反应而言，新价格可能是减少过度用水模式的可靠尝试。实施后，高、中、低流域年用水量分别减少14190.4 m3、17759.59 m3、38510.6 m3。这项研究将作为一项倡议，通过管理消费者的做法，为子孙后代保护宝贵的地下水资源。
{"title":"Using market mechanism to stimulate sustainable use of the non-renewable environmental resource (groundwater) in Barind Tract of Bangladesh","authors":"Anutosh Das, S. Kashem, M. Hasan","doi":"10.33430/V28N1THIE-2020-0036","DOIUrl":"https://doi.org/10.33430/V28N1THIE-2020-0036","url":null,"abstract":"Agriculture, the main economic driver of Barind Tract, is highly dependent on groundwater for surface water paucity in the area. Notwithstanding, farmers use water capriciously due to its low price that makes a substantial drop in the water table. In this context, the research attempts to determine a market-based water pricing mechanism to encourage an optimal use of the scarce non-renewable resource. Required data was collected by questionnaire survey, Focus Group Discussion (FGD), Contingent Valuation Method, expert-opinion survey and subsequent literature works. The results reveal that depletion level has arrived at 20, 11, 7.5 feet in high, mid and low tract respectively over the last 22 years, which results in a number of economic-environmental externalities in the area. The research monetarily evaluated the cost of externalities and incorporated it with the marginal cost of extraction to increase efficiency of an existing pricing system. Regarding human reaction to price elasticity, the new price can be a reliable attempt to reduce an overconsumption pattern of water. Quantity of consumed water can be reduced to 14190.4 m3, 17759.59 m3 and 38510.6 m3 in a year in high, mid and low tract area respectively with its implementation. The research will serve as an initiative to conserve the valuable groundwater resource for future generations by managing consumer practice.","PeriodicalId":35587,"journal":{"name":"Transactions Hong Kong Institution of Engineers","volume":"28 1","pages":"39-48"},"PeriodicalIF":0.0,"publicationDate":"2021-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48344989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-15DOI: 10.33430/V28N1THIE-2020-0011
T. L. Chen, D. Wong, Yan Wang, Ming Zhang
Loads on the plantar fascia could be influenced by running speed and relate to its pathology. This study calculated and compared plantar fascia strains under different running speed conditions using a dynamic finite element foot model and computational simulations. The model was previously validated featuring twenty bones, bulk soft tissue, muscles/ligaments, and a solid part of plantar fascia. A runner performed running trials under one preferred speed (PS), two lower (PS - 10% and PS - 20%) and two higher (PS + 10% and PS + 20%) speed conditions. The movement data were processed to drive musculoskeletal modelling and calculated boundary/loading conditions for the subsequent finite element analyses. The results show that peak strains of the plantar fascia increased with increasing running speed. From PS – 20% to PS + 20%, peak strain in the proximal and distal fascia regions increased by 96.78% and 58.89% respectively. Running speed could directly affect plantar fascia loading, which should be considered in running regimens and rehabilitation programmes. However, prescribing speed control for runners is worth pondering as it influences the trade-off between maximum single-step loads and loading frequency, which in coalescence determine the risk of plantar fascia injury and warranted further investigations.
{"title":"Plantar fascia loading at different running speed: a dynamic finite element model prediction","authors":"T. L. Chen, D. Wong, Yan Wang, Ming Zhang","doi":"10.33430/V28N1THIE-2020-0011","DOIUrl":"https://doi.org/10.33430/V28N1THIE-2020-0011","url":null,"abstract":"Loads on the plantar fascia could be influenced by running speed and relate to its pathology. This study calculated and compared plantar fascia strains under different running speed conditions using a dynamic finite element foot model and computational simulations. The model was previously validated featuring twenty bones, bulk soft tissue, muscles/ligaments, and a solid part of plantar fascia. A runner performed running trials under one preferred speed (PS), two lower (PS - 10% and PS - 20%) and two higher (PS + 10% and PS + 20%) speed conditions. The movement data were processed to drive musculoskeletal modelling and calculated boundary/loading conditions for the subsequent finite element analyses. The results show that peak strains of the plantar fascia increased with increasing running speed. From PS – 20% to PS + 20%, peak strain in the proximal and distal fascia regions increased by 96.78% and 58.89% respectively. Running speed could directly affect plantar fascia loading, which should be considered in running regimens and rehabilitation programmes. However, prescribing speed control for runners is worth pondering as it influences the trade-off between maximum single-step loads and loading frequency, which in coalescence determine the risk of plantar fascia injury and warranted further investigations.","PeriodicalId":35587,"journal":{"name":"Transactions Hong Kong Institution of Engineers","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46324496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-15DOI: 10.33430/V28N1THIE-2019-0029
A. Ngan, K. Siu
Super-long escalators that are increasingly used in mega-cities take up a large number of passengers, and so their risk of sudden failure draws serious attention. As a case study, on 25 March 2017, an escalator with a 21 m elevation in Hong Kong’s Langham Place had its main drive chain suddenly snapped by metal fatigue, causing the escalator to reverse at an accelerating speed. A number of passengers were injured. In this paper, two issues will be discussed: (1) whether metal fatigue of the main drive chain can be detected with conventional protocols, and (2) what safety factor is needed to prevent metal fatigue. Analysis shows that initial fatigue cracks in escalator drive chains may not be easily detected with the commonly adopted maintenance protocol. Also, the time window from the emergence of clear signs of fatigue failure to the sudden snapping of the drive chain may be as short as weeks or even days, versus the common safety inspection intervals of six months. The safety factor to prevent metal fatigue of the drive chain should be at least 7, whereas lower values are currently allowed. It is suggested that the government should review the legal requirements to meet the recommended value.
{"title":"Are super-long escalators safe? Lessons learned from the Langham Place escalator incident in Hong Kong","authors":"A. Ngan, K. Siu","doi":"10.33430/V28N1THIE-2019-0029","DOIUrl":"https://doi.org/10.33430/V28N1THIE-2019-0029","url":null,"abstract":"Super-long escalators that are increasingly used in mega-cities take up a large number of passengers, and so their risk of sudden failure draws serious attention. As a case study, on 25 March 2017, an escalator with a 21 m elevation in Hong Kong’s Langham Place had its main drive chain suddenly snapped by metal fatigue, causing the escalator to reverse at an accelerating speed. A number of passengers were injured. In this paper, two issues will be discussed: (1) whether metal fatigue of the main drive chain can be detected with conventional protocols, and (2) what safety factor is needed to prevent metal fatigue. Analysis shows that initial fatigue cracks in escalator drive chains may not be easily detected with the commonly adopted maintenance protocol. Also, the time window from the emergence of clear signs of fatigue failure to the sudden snapping of the drive chain may be as short as weeks or even days, versus the common safety inspection intervals of six months. The safety factor to prevent metal fatigue of the drive chain should be at least 7, whereas lower values are currently allowed. It is suggested that the government should review the legal requirements to meet the recommended value.","PeriodicalId":35587,"journal":{"name":"Transactions Hong Kong Institution of Engineers","volume":"28 1","pages":"49-57"},"PeriodicalIF":0.0,"publicationDate":"2021-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47839158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-15DOI: 10.33430/V28N1THIE-2019-0044
A. Chan, Charles H C Yeung, A. Westmoreland, S. Fok, C. Ng, F. Guedon
The entire Tuen Mun–Chek Lap Kok Link (TM-CLKL) was commissioned on 27 December 2020 and it comprises a 9km-long dual 2-lane carriageway between Tuen Mun and North Lantau, Hong Kong. Construction of the 5km-long sub-sea tunnels was carried out by two 14m diameter Tunnel Boring Machines (TBMs). The tunnel alignment for the TM-CLKL sub-sea tunnel section is in mixed ground condition with the first 500 m in mixed geology of slightly to moderately decomposed granite and completely decomposed granite (CDG), followed by soft ground condition with CDG, alluvial sand, alluvial clay and marine deposit. This mixed ground geology requires regular TBM cutterhead interventions to change the worn-out cutting tools during the tunnelling operation. As the tunnel alignment is up to 55 m below the sea level with the deepest seabed level at -21 mPD, in order to maintain the cutting face stability during the intervention, the intervention pressure could be up to 6 bars. This paper describes different techniques used for TBM interventions under the sea such as trimix bounce mode and saturation mode that appears first time in Hong Kong under a high hyperbaric pressure to change the worn-out cutting tools at the TBM cutterhead.
{"title":"Use of saturation diving technique for tunnel boring machine cutterhead intervention in the Tuen Mun–Chek Lap Kok Link Sub-sea Tunnel Project, Hong Kong","authors":"A. Chan, Charles H C Yeung, A. Westmoreland, S. Fok, C. Ng, F. Guedon","doi":"10.33430/V28N1THIE-2019-0044","DOIUrl":"https://doi.org/10.33430/V28N1THIE-2019-0044","url":null,"abstract":"The entire Tuen Mun–Chek Lap Kok Link (TM-CLKL) was commissioned on 27 December 2020 and it comprises a 9km-long dual 2-lane carriageway between Tuen Mun and North Lantau, Hong Kong. Construction of the 5km-long sub-sea tunnels was carried out by two 14m diameter Tunnel Boring Machines (TBMs). The tunnel alignment for the TM-CLKL sub-sea tunnel section is in mixed ground condition with the first 500 m in mixed geology of slightly to moderately decomposed granite and completely decomposed granite (CDG), followed by soft ground condition with CDG, alluvial sand, alluvial clay and marine deposit. This mixed ground geology requires regular TBM cutterhead interventions to change the worn-out cutting tools during the tunnelling operation. As the tunnel alignment is up to 55 m below the sea level with the deepest seabed level at -21 mPD, in order to maintain the cutting face stability during the intervention, the intervention pressure could be up to 6 bars. This paper describes different techniques used for TBM interventions under the sea such as trimix bounce mode and saturation mode that appears first time in Hong Kong under a high hyperbaric pressure to change the worn-out cutting tools at the TBM cutterhead.","PeriodicalId":35587,"journal":{"name":"Transactions Hong Kong Institution of Engineers","volume":"28 1","pages":"31-38"},"PeriodicalIF":0.0,"publicationDate":"2021-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46652416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Special Issue with Awarded and Shortlisted Papers from the HKIE Outstanding Paper Award for Young Engineers/Researchers 2020","authors":"","doi":"10.33430/v27n4","DOIUrl":"https://doi.org/10.33430/v27n4","url":null,"abstract":"","PeriodicalId":35587,"journal":{"name":"Transactions Hong Kong Institution of Engineers","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43786354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-30DOI: 10.33430/v27n3thie-2019-0055
M. Leung, C. Tso, Wei Wu, Zhanying Zheng, Jingyu Cao
In tropical and subtropical regions, air-conditioning commonly consumes the most energy in buildings. The chillers used in existing air-conditioning systems are largely based on thermodynamic vapour compression cycle because the cycle is highly effective, efficient and practical. Moreover, the system installation and operation are convenient when grid electricity is available. Popular vapour compression chiller types include air-cooled, water-cooled, seawater-cooled and oil-free chillers. In addition, thermal-driven absorption and adsorption chillers have become available in the market. Viable sources of thermal energy input include fuel combustion, renewable solar energy, waste heat, and so on. This paper provides an overview of different types of chillers and system configurations in terms of mechanisms, characteristics, energy efficiency, environmental performance and costs. The technical information and comparisons should help engineers select the chiller type in air-conditioning system design for achieving high sustainability.
{"title":"Chillers of air-conditioning systems: An overview","authors":"M. Leung, C. Tso, Wei Wu, Zhanying Zheng, Jingyu Cao","doi":"10.33430/v27n3thie-2019-0055","DOIUrl":"https://doi.org/10.33430/v27n3thie-2019-0055","url":null,"abstract":"In tropical and subtropical regions, air-conditioning commonly consumes the most energy in buildings. The chillers used in existing air-conditioning systems are largely based on thermodynamic vapour compression cycle because the cycle is highly effective, efficient and practical. Moreover, the system installation and operation are convenient when grid electricity is available. Popular vapour compression chiller types include air-cooled, water-cooled, seawater-cooled and oil-free chillers. In addition, thermal-driven absorption and adsorption chillers have become available in the market. Viable sources of thermal energy input include fuel combustion, renewable solar energy, waste heat, and so on. This paper\u0000provides an overview of different types of chillers and system configurations in terms of mechanisms, characteristics, energy efficiency, environmental performance and costs. The technical information and comparisons should help engineers select the chiller type in air-conditioning system design for achieving high sustainability.","PeriodicalId":35587,"journal":{"name":"Transactions Hong Kong Institution of Engineers","volume":"27 1","pages":"113-127"},"PeriodicalIF":0.0,"publicationDate":"2020-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46513942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-30DOI: 10.33430/v27n3thie-2019-0019
J. Li
Due to the rising concerns regarding food waste disposal as well as the increasing demand for renewable energy nowadays, a number of European countries have adopted anaerobic co-digestion, a technology that deals with food waste and sewage sludge. As stated in the HKSAR Government’s Policy Address 2016, the feasibility of using existing sewage treatment facilities for co-digestion of food waste and sewage sludge has been under exploration. A trial scheme has been commenced in 2019. This paper aims to compare the efficiency of biogas production and volatile solid reduction in co-digestion of food waste and sewage with mono-digestion in laboratory scale.
{"title":"Thermophilic co-digestion of food waste and sewage sludge","authors":"J. Li","doi":"10.33430/v27n3thie-2019-0019","DOIUrl":"https://doi.org/10.33430/v27n3thie-2019-0019","url":null,"abstract":"Due to the rising concerns regarding food waste disposal as well as the increasing demand for renewable energy nowadays, a number of European countries have adopted anaerobic co-digestion, a technology that deals with food waste and sewage sludge. As stated in the HKSAR Government’s Policy Address 2016, the feasibility of using existing sewage treatment facilities for co-digestion of food waste and sewage sludge has been under exploration. A trial scheme has been commenced in 2019. This paper aims to compare the efficiency of biogas production and volatile solid reduction in co-digestion of food waste and sewage with mono-digestion in laboratory scale.","PeriodicalId":35587,"journal":{"name":"Transactions Hong Kong Institution of Engineers","volume":"27 1","pages":"128-134"},"PeriodicalIF":0.0,"publicationDate":"2020-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45991003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-30DOI: 10.33430/v27n3thie-2018-0035
Zhili Sun, Cui Qi, Qingzhao Liu, Caiyun Wang, Jiamei Li, Yang Lijie
To determine the suitable vapour compression refrigeration system for different temperature ranges, this paper established thermodynamic models for a single-stage vapour compression refrigeration system with an economiser (SSRS+E), a two-stage vapour compression refrigeration system (TSRS), and a cascade vapour compression refrigeration system (CRS) and conducted an energetic and economic analysis of it. The results show that compared with TSRS, SSRS+E can save energy by 13.6% and 7.1%, in the evaporating temperatures of -20°C and -25°C, respectively. R744/R717 CRS is superior to TSRS in terms of energy consumption and refrigeration unit investment costs. Compared with TSRS, R744/R717 CRS can save energy by 14.1% and 18.8%, in the evaporating temperatures of -45°C and -50°C, respectively. Based on the energetic and economic analysis, SSRS+E is recommended for use above the evaporating temperature of -25°C. TSRS is recommended for use in the evaporating temperature range of -45°C to -25°C, and R744/R717 CRS is recommended for use below the evaporating temperature of -45°C.
{"title":"Energetic and economic analysis of vapour compression refrigeration systems applied in different temperature ranges","authors":"Zhili Sun, Cui Qi, Qingzhao Liu, Caiyun Wang, Jiamei Li, Yang Lijie","doi":"10.33430/v27n3thie-2018-0035","DOIUrl":"https://doi.org/10.33430/v27n3thie-2018-0035","url":null,"abstract":"To determine the suitable vapour compression refrigeration system for different temperature ranges, this paper established thermodynamic models for a single-stage vapour compression refrigeration system with an economiser (SSRS+E), a two-stage vapour compression refrigeration system (TSRS), and a cascade vapour compression refrigeration system (CRS) and conducted an energetic and economic analysis of it. The results show that compared with TSRS, SSRS+E can save energy by 13.6% and 7.1%, in the evaporating temperatures of -20°C and -25°C, respectively. R744/R717 CRS is superior to TSRS in terms of energy consumption and refrigeration unit investment costs. Compared with TSRS, R744/R717 CRS can save energy by 14.1% and 18.8%, in the evaporating temperatures of -45°C and -50°C, respectively. Based on the energetic and economic analysis, SSRS+E is recommended for use above the evaporating temperature of -25°C. TSRS is recommended for use in the evaporating temperature range of -45°C to -25°C, and R744/R717 CRS is recommended for use below the evaporating temperature of -45°C.","PeriodicalId":35587,"journal":{"name":"Transactions Hong Kong Institution of Engineers","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69753679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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