자전거 운동 시 소비되는 에너지량 계산 알고리즘 설계

임명성(Myoung-Seong Lim),정진형(Jin-Hyoung Jeong),이상식(Sang-Sik Lee),장지훈(Jee-Hun Jang) 한국정보전자통신기술학회 2021 한국정보전자통신기술학회논문지 Vol.14 No.1

본 연구는 자전거 운동 시 소비되는 에너지량 계산을 위한 알고리즘을 개발하고자 하는 목적으로 수행되었다. 대학에 재학 중인 60명(남자 30명, 여자 30명)을 대상으로 자전거 운동 시 10초 간격으로 배출하는 호흡가스를 분석하고 에너지소비량을 측정하였으며, 시판 유선속도계로 측정된 결과 및 선행연구에서의 추론식과 비교 검증하였다. 남자의 자전거운동 시 시간에 따른 소비되는 에너지량을 추정하는 알고리즘은 ‘에너지소비량(㎉)=5.048×(시간(분))–2.258(r2=0.998)’로 계산되었다. 여자의 자전거 운동 중 시간에 따른 에너지소비량 추정 회귀식은 ‘에너지소비량(㎉)=4.466×(시간(분))–1.605(r2=.999)’로 계산되었다. 남자의 자전거운동 시 시간과 속도에 따른 에너지소비량 추정 회귀식은 ‘에너지소비량(㎉)=(0.05×속도(kph))×(4.750×시간(분)+0.091)’로 계산되었다. 여자의 자전거 운동 시 시간과 속도에 따른 소비되는 에너지량 추정 회귀식은 속도 20kph 이하 조건에서는 ‘에너지소비량(㎉)=(0.05×속도(kph))×(4.151×시간(분)-0.736)’으로 계산되었고, 속도 20kph 초과 조건에서는 ‘에너지소비량(㎉)=(0.04×속도(kph))×(4.151×시간(분)-0.736)’으로 계산되었다. 결론적으로 자전거 운동 시 소비되는 에너지량을 계산하기 위한 알고리즘개발에는 시간 및 속도에 따른 에너지소비량 추론식 적용이 적절한 것으로 제언된다. The purpose of this study was to develop the mathematic algorithm for energy expenditure calculation during cycling as a part of the development of a higher value-added cycle. Participants were 60 university students (male 30, female 30). Energy expenditure was measured with breathing gas at 10 sec intervals by gas analyzer connected with stationary cycle ergometer. Values presented by commercial speedometer and preceding researches were used for verification of actual measurement values in this study. In conclusion, the mathematic algorithms for energy expenditure calculation during cycling were as follows. For male, energy expenditure(㎉)=5.048×cycling time(min)–2.258, energy expenditure(㎉)=(0.05×cycling velocity(kph))×(4.750×cycling time(min)+0.091). For female, energy expenditure(㎉)=4.466×cycling time(min)–1.605, energy expenditure(㎉)(cycling velocity≤20kph)=(0.05×cycling velocity(kph))×(4.151× cycling time(min)-0.736), energy expenditure(㎉)(cycling velocity>20kph)=(0.04×cycling velocity(kph)) ×(4.151×cycling time(min) -0.736). And it is suggested that the developed algorithm with cycling time and velocity should be applied for the development of a higher value-added cycle.

Effect of uniaxial stress on energy harvesting, storage and electrocaloric performance of BZT ceramics

Patel Satyanarayan,Yadav Harekrishna,Kumar Manish 한국세라믹학회 2021 한국세라믹학회지 Vol.58 No.4

In this work, a systematic approach of waste (thermal/mechanical) energy harvesting and storage potential is studied in Ba 0.85 Zr 0.15 TiO 3 (BZT) ceramics. The eff ect of stress on energy storage density (harvesting/storage) and electrocaloric per- formance is also studied. For this purpose, polarization–electric fi eld hysteresis loops were recorded at various temperatures and uniaxial compressive stress. The Olsen cycle and electro-mechanical cycle are used for direct waste heat or mechanical energy to electrical energy conversion. A thermal energy-harvesting density of 42 kJ/m 3 per cycle was obtained when the Olsen cycle was operated between 296–343 K and 0.25–1.5 MV/m. The electro-mechanical cycle-based energy harvesting is estimated as 78 kJ/m 3 under the applied stress of 5–160 MPa and the electric fi eld of 0.25–1.5 MV/m. The energy storage density is found as 39 kJ/m 3 at zero stress fi eld and 343 K, which increases to 53 kJ/m 3 under the biased stress of 80 MPa in a wide operating temperature range of 296–328 K. It is observed that the high energy storage is a result of the reduction of the hysteresis loss. The electrocaloric temperature is found as 0.16 K and 0.18 K under the 0 and 80 MPa stress fi elds, respectively. Overall, the reported fi ndings will enrich our understanding of the stress eff ect on BZT materials, which off ers high performance for energy harvesting and storage-based applications. Moreover, this work can be also helpful in improv- ing the energy storage density and electrocaloric eff ect via stress confi nement.

에너지 생산이 가능한 무선 센서 네트워크에서 잔여 에너지 인지 듀티-사이클 스케줄링 기법

이성원(Sungwon Lee),유홍석(Hongseok Yoo),김동균(Dongkyun Kim) 한국통신학회 2014 韓國通信學會論文誌 Vol.39 No.10(네트워크)

네트워크 수명을 연장시키기 위해 무선 센서 네트워크에서는 idle listening에 소비되는 에너지를 줄일 수 있는 듀티-사이클 MAC 프로토콜들이 제안되었다. 일반적인 듀티-사이클 MAC 프로토콜에서 각 센서 노드는 잔여 에너지양을 기반으로 듀티-사이클 주기를 계산한다. 그러나 에너지 수집이 가능한 센서 네트워크에서 기존 듀티-사이클 주기는 에너지 수집률이 높은 센서 노드에 불필요한 sleep 지연을 발생시킨다. 따라서 우리는 이전 연구에서 잔여 에너지양과 에너지 수집률을 함께 고려하여 듀티 사이클-주기를 조절하는 듀티-사이클 스케줄링 기법을 제안하였다. 그러나 이러한 듀티-사이클 MAC 프로토콜들은 듀티 사이클-주기 변화에 따른 성능 차이를 고려하지 않고 듀티-사이클 주기를 항상 선형적으로 조절하므로, 응용의 요구사항에 맞는 최적의 듀티 사이클 주기를 얻지 못한다. 본 논문에서는 듀티-사이클 주기를 계산하는 세 가지 기법들을 제안하고 그 결과에 대해 분석한다. 실험을 통해 제안된 기법들이 기존 듀티-사이클 스케줄링 기법에 비해 네트워크 수명, 단대단 패킷 전송 시간과 패킷 전송률을 각각 최대 23%, 44%, 31% 증가시킴을 확인하였다. In order to increase network lifetime, duty-cycle MAC protocols which can reduce energy consumption caused by idle listening is proposed for WSNs. In common duty-cycle MAC protocols, each sensor node calculates its duty-cycle interval based on the current amount of residual energy. However, in WSNs with the capability of energy harvesting, existing duty-cycle intervals based on the residual energy may cause the sensor nodes which have high energy harvesting rate to suffer unnecessary sleep latency. Therefore, a duty-cycle scheduling scheme which adjust the duty-cycle interval based on both of the residual energy and the energy harvesting rate was proposed in our previous work. However, since this duty-cycle MAC protocol overlooked the performance variation according to the change of duty-cycle interval and adjusted the duty-cycle interval only linearly, the optimal duty-cycle interval could not be obtained to meet application requirements. In this paper, we propose three methods which calculate the duty-cycle interval and analyse their results. Through simulation study, we verify that network lifetime, end-to-end delay and packet delivery ratio can be improved up to 23%, 44% and 31% as compared to the existing linear duty-cycle scheduling method, respectively.

Changes in energy and carbon intensity in Seoul’s water sector

Kim, Hana,Chen, Weiming Elsevier 2018 Sustainable cities and society Vol.41 No.-

<P><B>Abstract</B></P> <P>The water sector accounts for a significant proportion of the total energy consumption in urban areas; therefore, that sector can contribute to energy transition in urban areas. Seoul, South Korea has promoted the use of renewable energy and sewer heat as part of city-wide energy transition efforts. This study built energy consumption inventories for the urban water cycle in Seoul for 2012 and 2015 and investigated changes in net energy intensity and corresponding net carbon intensity during that period. It found that Seoul’s energy transition efforts reduced net energy intensity in the water sector from 5.83 MJ/m<SUP>3</SUP> in 2012 to 5.42 MJ/m<SUP>3</SUP> in 2015, even with the increased use of energy-intensive advanced water treatment technology. In addition, this study estimated that about 8.52% of the water sector’s current energy consumption could be saved in 2020 if 18.4 million m<SUP>3</SUP>/year of water were reused and 2.40 million m<SUP>3</SUP>/year of rainwater were harvested. This study showed a way to extend energy transition efforts into the urban water sector by reducing energy demand through reducing water demand.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Wastewater treatment is the most energy-intensive stage of Seoul’s water cycle. </LI> <LI> Seoul’s energy transition efforts reduced the energy intensity of the water sector. </LI> <LI> Water reuse and rainwater harvest could save 8.5% of the current energy consumption of Seoul’s water sector. </LI> </UL> </P>

A new finite element procedure for fatigue life prediction of AL6061 plates under multiaxial loadings

Tarar, Wasim,Herman Shen, M.H.,George, Tommy,Cross, Charles Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.5

An energy-based fatigue life prediction framework was previously developed by the authors for prediction of axial, bending and shear fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was based on a new constitutive law, which states the following: the amount of energy required to fracture a material is constant. In the first part of this study, energy expressions that construct the constitutive law are equated in the form of total strain energy and the distortion energy dissipated in a fatigue cycle. The resulting equation is further evaluated to acquire the equivalent stress per cycle using energy based methodologies. The equivalent stress expressions are developed both for biaxial and multiaxial fatigue loads and are used to predict the number of cycles to failure based on previously developed prediction criterion. The equivalent stress expressions developed in this study are further used in a new finite element procedure to predict the fatigue life for two and three dimensional structures. In the second part of this study, a new Quadrilateral fatigue finite element is developed through integration of constitutive law into minimum potential energy formulation. This new QUAD-4 element is capable of simulating biaxial fatigue problems. The final output of this finite element analysis both using equivalent stress approach and using the new QUAD-4 fatigue element, is in the form of number of cycles to failure for each element on a scale in ascending or descending order. Therefore, the new finite element framework can provide the number of cycles to failure at each location in gas turbine engine structural components. In order to obtain experimental data for comparison, an Al6061-T6 plate is tested using a previously developed vibration based testing framework. The finite element analysis is performed for Al6061-T6 aluminum and the results are compared with experimental results.

Energy and exergy analysis of gas turbine combined cycle with exhaust gas recirculation under part-load conditions

Keying Li,Jinling Chi,Shijie Zhang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5

This paper presents the energy and exergy analysis of the gas turbine combined cycle during part-load operation under the exhaust gas recirculation - inlet/variable guide vane control (EGR-IGVC) strategy. The exergy destruction across each component and the energy and exergy efficiency of the topping, bottoming, and combined cycle are determined. Results show that EGR-IGVC and IGVC both effectively enhance the part-load efficiency of the combined cycle compared to fuel flow control (FFC) because higher turbine exhaust temperature allows more exergy to enter the bottoming cycle and increases bottoming cycle power output. However, EGR-IGVC decreases the bottoming cycle energy and exergy efficiency compared with IGVC. Even so, EGR-IGVC increases the topping cycle energy and exergy efficiency and can obtain a higher bottoming cycle power output. The combined cycle efficiency is enhanced by 0.97-1.21 percentage points over IGVC at 40 %-90 % loads. Exergy analysis has important guiding significance for further improving the part-load performance of the combined cycle.

A new finite element procedure for fatigue life prediction of AL6061 plates under multiaxial loadings

Wasim Tarar,M.-H. Herman Shen,Tommy George,Charles Cross 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.5

An energy-based fatigue life prediction framework was previously developed by the authors for prediction of axial, bending and shear fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was based on a new constitutive law, which states the following: the amount of energy required to fracture a material is constant. In the first part of this study, energy expressions that construct the constitutive law are equated in the form of total strain energy and the distortion energy dissipated in a fatigue cycle. The resulting equation is further evaluated to acquire the equivalent stress per cycle using energy based methodologies. The equivalent stress expressions are developed both for biaxial and multiaxial fatigue loads and are used to predict the number of cycles to failure based on previously developed prediction criterion. The equivalent stress expressions developed in this study are further used in a new finite element procedure to predict the fatigue life for two and three dimensional structures. In the second part of this study, a new Quadrilateral fatigue finite element is developed through integration of constitutive law into minimum potential energy formulation. This new QUAD-4 element is capable of simulating biaxial fatigue problems. The final output of this finite element analysis both using equivalent stress approach and using the new QUAD-4 fatigue element, is in the form of number of cycles to failure for each element on a scale in ascending or descending order. Therefore, the new finite element framework can provide the number of cycles to failure at each location in gas turbine engine structural components. In order to obtain experimental data for comparison, an Al6061-T6 plate is tested using a previously developed vibration based testing framework. The finite element analysis is performed for Al6061-T6 aluminum and the results are compared with experimental results.

Economizer cycle을 채용한 전열교환형 환기시스템의 에너지 절감 효과 분석 : 국내 학교를 대상으로

김주욱(Joo Wook Kim),박재형(Jae Hyung Park),송두삼(Doo Sam Song),주의성(Euy Sung Chu),권영철(Young Chul Kwon) 대한설비공학회 2009 대한설비공학회 학술발표대회논문집 Vol.2009 No.-

Maintaining an IAQ with fresh in school building is very important because the good IAQ can be possible to improve the academic performance. Since school buildings are very dense and require a lot of fresh air, the need for ERV(Energy Recovery Ventilator) has become obvious. While opening a window does provide ventilation, the building's heat and humidity will then be lost in the winter and gained in the summer, both of which are undesirable for the indoor climate and for energy efficiency. ERV technology offers an optimal solution: fresh air, better climate control and energy efficiency. However, when the outdoor air condition is favorable to control the indoor environment such as spring and autum in Korea, heat exchange in ERV would rather increase the cooling load than diminish. Economizer cycle control which using the outdoor air in controlling the indoor thermal environment has many benefit in terms of energy saving and IAQ control. In this study, the ERV with economizer cycle control will be suggested. And then the system control characteristics and energy saving effect will be analyzed through the TRSNSYS Simulation.

Combining Life Cycle Assessment and Manufacturing System Simulation: Evaluating Dynamic Impacts from Renewable Energy Supply on Product-Specific Environmental Footprints

Jan-Markus Rödger,Jan Beier,Malte Schönemann,Christine Schulze,Sebastian Thiede,Niki Bey,Christoph Herrmann,Michael Z. Hauschil 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.3

The eco-efficiency of actual production processes is still one dominating research area in engineering. However, neglecting the environmental impacts of production equipment, technical building services and energy supply might lead to sub-optimization or burden-shifting and thus reduced effectiveness. As an established method used in sustainability management, Life Cycle Assessment aims at calculating the environmental impacts from all life cycle stages of a product or system. In order to cope with shortcomings of the static character of life cycle models and data gaps this approach combines Life Cycle Assessment with manufacturing system simulation. Therefore, the two life cycles of product and production system are merged to assess environmental sustainability on product level. Manufacturing simulation covers the production system and Life Cycle Assessment is needed to relate the results to the final product. This combined approach highlights the influences from dynamic effects in manufacturing systems on resulting life cycle impact from both product and production system. Furthermore, the importance of considering indirect peripheral equipment and its effects on the manufacturing system operation in terms of output and energy demands is underlined. The environmental flows are converted into impacts for the five recommended environmental impact categories. Thus, it can be demonstrate that Life Cycle Assessment can enhance the process simulation and help identify hot-spots along the life cycle. The combined methodology is applied for analysing a case study in fourteen scenarios for the integration of volatile energy sources into energy flexible manufacturing control.

BUCKET: Scheduling of Solar-Powered Sensor Networks via Cross-Layer Optimization

Sungjin Lee,Beom Kwon,Sanghoon Lee,Bovik, Alan Conrad IEEE 2015 IEEE Sensors Journal Vol. No.

<P>Renewable solar energy harvesting systems have received considerable attention as a possible substitute for conventional chemical batteries in sensor networks. However, it is difficult to optimize the use of solar energy based only on empirical power acquisition patterns in sensor networks. We apply acquisition patterns from actual solar energy harvesting systems and build a framework to maximize the utilization of solar energy in general sensor networks. To achieve this goal, we develop a cross-layer optimization-based scheduling scheme called binding optimization of duty cycling and networking through energy tracking (BUCKET), which is formulated in four-stages: 1) prediction of energy harvesting and arriving traffic; 2) internode optimization at the transport and network layers; 3) intranode optimization at the medium access control layer; and 4) flow control of generated communication task sets using a token-bucket algorithm. Monitoring of the structural health of bridges is shown to be a potential application of an energy-harvesting sensor network. The example network deploys five sensor types: 1) temperature; 2) strain gauge; 3) accelerometer; 4) pressure; and 5) humidity. In the simulations, the BUCKET algorithm displays performance enhancements of ~12-15% over those of conventional methods in terms of the average service rate.</P>