• Journal of KIISE
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• v.43 no.3
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• pp.296-303
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• 2016

Mobile real-time systems with limited system resources and a limited power source need to fully utilize the system resources when the workload is heavy and reduce energy consumption when the workload is light. EDZL (Earliest Deadline until Zero Laxity), a multiprocessor real-time scheduling algorithm, can provide high system utilization, but little work has been done aimed at reducing its energy consumption. This paper tackles the problem of DVFS (Dynamic Voltage/Frequency Scaling) in EDZL scheduling. It proposes a technique to compute a uniform speed on full-chip DVFS platforms and individual speeds of tasks on per-core DVFS platforms. This technique, which is based on the EDZL schedulability test, is a simple but effective one for determining the speeds of tasks offline. We also show through simulation that the proposed technique is useful in reducing energy consumption.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2396-2402
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• 2015

Air compressor, as an essential equipment used in the factory and plant operations, accounts for around 30% of the total electricity consumption in U.S.A, thereby being proposed advanced technologies to reduce electricity consumption. When the fluctuation of the compressed airflow rate is small, the system stability is increased followed by the reduction of the electricity consumption which results in the efficient design of the energy system. In the statistical analysis, the normal distribution, log normal distribution, gamma distribution or the like are generally used to identify system characteristics. However a single distribution may not fit well the data with long tail, representing sudden air flow rate especially in extremes. In this paper, authors decouple the compressed airflow rate into two parts to present a mixture of distribution function and suggest a method to reduce the electricity consumption. This reduction stems from the fact that a general pareto distribution estimates more accurate quantile value than a gaussian distribution when an airflow rate exceeds over a large number.

• Journal of Energy Engineering
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• v.24 no.3
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• pp.115-121
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• 2015

This paper presents the introduction plan of the renewable energy in innovation city. The introduction plan to make the condition of innovation city best should consider the economical efficiency, the quality of life and the sustainable development. The design of balanced city is demanded to build environment friendly and sustainable city. Energy efficient buildings should be designed to deal with the energy efficiency and environment problem. Therefore, in this paper, we analyze the energy efficiency and provide the method to introduce the renewable energy system, in various buildings. As a result, the renewable energy plans of each innovation city are suggested and analyzed.

• Land and Housing Review
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• v.3 no.2
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• pp.169-175
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• 2012

In recent, there are many studies associated with energy piles to save initial construction cost for ground source heat pump system. In this study, to evaluate geothermal exchange rates two types (a connection type and a slinky type) of cast-in-place energy piles (PRD, 4.5m in depth, 1,200 mm in diameter) were constructed for the tests and their efficiencies were compared with numerical analysis results. As a result, starting with operation, geothermal exchange rate gradually decreases due to exchange of lower ground temperature. In the case of connection type, temperature difference is $0.37^{\circ}C$ in heating mode and $0.34^{\circ}C$, in cooling mode, respectively. In addition, in case of a connection type, geothermal exchange rate in heating mode is 2,314W/m and in cooling mode, 252.2W/m whose value is 9% higher than in heating mode. In the case of slinky type, the average geothermal exchange rate in heating mode is 168.0W/m, which is about 27% lower than that of connection type.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1249-1255
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• 2011

In modern large-scale semiconductor manufacturing clean rooms, the energy consumed by the outdoor air-conditioning system during heating, humidification, cooling, and dehumidification of the incoming outdoor air represents about 45% of the total air-conditioning load required to maintain a clean-room environment. In particular, the energy required for humidification of the outdoor air in winter is very high. Therefore, evaluation and comparison of the energy consumption in key humidification systems, viz., steam-humidification and water-spray-humidification systems, used in outdoor air-conditioning systems would be useful to reduce the outdoor air-conditioning load in clean rooms. In the present study, an experiment with an outdoor air flow of 1000 $m^3$/h was conducted to compare the air-conditioning process and energy consumption in outdoor air-conditioning systems with electrodeboiler steam humidifiers and air-washer water spray humidification systems. The experimental results showed that the water-spray-humidification-type outdoor air-conditioning system consumed less electrical power than did the steam-humidification-type system and was more energy efficient during winter.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.11
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• pp.580-591
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• 2017

In accordance with 2015 Paris agreement, each individual country around the world should voluntarily propose not only its (individual) reduction target, but also actively develop and present expansion targets of its scope and concrete reduction goals exceeding the previous ones. Accordingly, it is necessary to prepare a macroscopic, long-range strategy for reducing energy consumption and greenhouse gas emissions, which can cover a single building, town, city and eventually even a province. The purpose of this research is to gather and compile government-acquired data from various sources and (in accordance with contents and specificity), combine building data by stages by using multi-variable matrix and then analyze the significance of combined data for each stage. The first order data presents the probability and the cost effectiveness of energy saving on the scale of a city or a province, based only upon general information, size and power consumption of buildings. The second order data can identify a pattern of energy consumption for a building of a specific purpose and which tends to consume a larger amount of energy during one particular season (than others). Finally, the third order data can derive influential factors (base load, humidity) from the energy consumption pattern of a building, and thus propose an informed and practical energy-saving method to be applied in real time.

• Journal of Climate Change Research
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• v.3 no.3
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• pp.183-193
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• 2012

In this study, the S University's energy usage, greenhouse gas emissions situation and potential reduction amount were analyzed using a long-term energy analysis model, LEAP. In accordance with the VISION 2020 and university's own improvement plans, S University plans to complete a second campus through expansion constructions by 2020 and by allocating the needed land. Accordingly, increases in energy usage and greenhouse gas emissions seem inevitable. Hence, in this study, the calculations of potential reduction amount by 2020 were attempted through the use of LEAP model by categorizing the energy used based on usage types and by proposing usage typebased reduction methods. There were a total of 4 scenarios: a standard scenario that predicted the energy usage without any additional energy reduction activity; energy reduction scenario using LED light replacement; energy reduction scenario using high efficiency building equipment; and a scenario that combines these two energy reduction scenarios. As scenario-based results, it was ascertained that, through the scenario that had two other energy reduction scenarios combined, the 2020 greenhouse gas emissions amount would be 14,916 tons of $CO_2eq$, an increase of 43.7% compared to the 2010 greenhouse gas emissions amount. Put differently, it was possible to derive a result of about 23.7% reduction of the greenhouse gas emissions amount for S University's greenhouse gas emissions amount through energy reduction activities. In terms of energy reduction methods, changing into ultra-high efficiency building equipment would deliver the most amount of reduction.

• Journal of Korean Society of Transportation
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• v.20 no.1
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• pp.19-38
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• 2002

To evaluate the effects of transportation system operation, usually measures of effectiveness(MOE) such as travel time, space mean speed, stop/delay ratio have been used. But, energy consumption as well as the existing MOE in transportation receives more attention as an alternative MOE in transportation operation. The purpose of this study is a development of procedure, which could measure the relative energy consumption for each alternative and compare the results. A mesoscopic simulator called INTEGRATION is used to evaluate the operation of high occupancy vehicle lane, signal optimization, lane expansion, and the application of ITS. Among those, the application of ITS shows the greatest effectiveness in energy reduction, and then lane expansion, signal optimization, and the operation of high occupancy vehicle lane in the order named. Because we don't consider the characteristics of vehicle class, Potential demand and the simulation time is just for an hour. it is recommended that a procedure for precise economic analysis and an improvement in methodology are needed in the future for the expanded application of this study.

• Journal of Energy Engineering
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• v.23 no.2
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• pp.49-56
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• 2014

It is important to keep stable effluent water quality and minimize operation cost in biological wastewater treatment plant. However, the optimal operation is difficult because of the change of influent flow rate and concentrations, the nonlinear dynamics of microbiology growth rate and other environmental factors. Therefore, many wastewater treatment plants are operated for much more redundant oxygen or chemical dosing than the necessary. In this study, the optimal control scheme for dissolved oxygen (DO) is suggested to prevent over-aeration and the reduction of the electric cost in plant operation while maintaining the dissolved oxygen (DO) concentration for the metabolism of microorganisms in oxic reactor. For optimal control, The oxygen uptake rate (OUR) is realtime measured for the identification of influent characterization and the identification of microorganisms' oxygen requirement in oxic reactor. Optimal DO seT-Point needed for the microorganism is suggested based on real time measurement of oxygen uptake of microorganism and the control of air blower. Therefore, both stable effluent quality and minimization of electric cost are satisfied with a suggested optimal setpoint decision system by providing the necessary oxygen supply requirement to the microorganisms coping with the variations of influent loading.

• Journal of Convergence for Information Technology
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• v.9 no.1
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• pp.19-27
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• 2019

In recent years, with the advancement of IT technology, we expect data size of the world to increase 10 times in 2025. The rapid development of this Internet technology leads to the downsizing of the server system of the data center which manages and operates the data, the capacity of the storage medium, and the power consumption of the data center. In this paper, we propose an energy conservation policy and analyze it in real time by analyzing the power consumption pattern of the server system of the data center. The proposed system can monitor and analyze the power consumption pattern of the individual server system in the data center, and it can be expected that about 10% of the total power consumption of the data center will be saved by efficiently managing the actual operation time of the server system.