• Journal of the Korean Solar Energy Society
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• v.31 no.3
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• pp.57-66
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• 2011

A Photovoltaic/Thermal(PVT) solar system consists of PV module and thermal absorber plate which convert the absorbed solar radiation into electricity and heat. Meaningful researches and development (R&D) on the PVT technologies have been performed since the 1970s. This paper presents a review of the previous works covering the various types of PVT and their performance analysis in terms of electrical and thermal efficiency. This review compares electrical and thermal efficiency of the different types of PVT collectors and analyzes the parameters affecting PVT performance. Based on the literature review, box channel type PVT with unglazed, or flat plate PVT with glazed have the highest efficiency among them. From the literature review, R&D should be carried out aiming at improving their overall electrical and thermal efficiency, cutting down the cost, and making them more competitive in the energy consumption market.

• Journal of the Korean Solar Energy Society
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• v.32 no.4
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• pp.65-70
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• 2012

Each country has implemented various environmental policies to prevent natural disasters and destruction of ecosystem caused by global wanning. The republic of Korea also was performed building energy efficiency rating certification system as part of paradigm of 'Low carbon green growth' since 2010. However, the status on the building energy efficiency rating certification system has not been analyzed. In this study, We analyzed the elements affecting the energy efficiency of small office buildings focusing the status and certification cases of the building energy efficiency rating system. As a result, it is judged that thermal performance contribution of the building envelope is not high in the buildings certificated the first grade of the building energy efficiency rating system.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.4
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• pp.331-338
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• 2015

Solar air heaters (SAHs) are simple in design and widely used for solar energy collection devices, and a packed bed is one of typical solar energy storage systems of thermal energy captured by SAHs. This paper presents mathematical modeling and simulation on the thermal performance of various packed bed energy storage systems. A MATLAB program is used to estimate the thermal efficiency of packed bed SAH. Among the various packed bed energy storage systems considered, the wire mesh screen packed bed SAH shows the best thermal efficiency over the entire range of design conditions. The maximum of thermal efficiency of packed bed SAH with wire mesh screen matrices has been found to be 0.794 for Re=2000 - 20000 and ${\Delta}T/I=0.002-0.02$.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.965-971
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• 2017

The primary objective of this study was to assess the energy efficiency performance of an optimized hull form capable of saving energy based on existing vessels. The bow shape of existing vessels was investigated, giving consideration to design draft and speed. Resistance performances were also assessed for existing vessels according to operating conditions. Commercial CFD codes and model test materials were used to assess effective power. An optimized hull form with minimum resistance was selected given real operating conditions. The effective horsepower of existing and optimized vessels was estimated at three speeds. Resistance performance for an optimized vessel showed a 6 % improvement in effective horsepower at design speed (12 knots) compared to existing vessels. Quasi-propulsive efficiency employed experimental data, while energy efficiency performance was analyzed based on operating days, bunker fuel oil C cost, daily fuel oil consumption and specific fuel oil consumption. Energy efficiency performance for an optimized vessel showed a gain of 30 million won per year in reduced costs at design speed (12 knots) compared to existing vessels.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.6
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• pp.668-676
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• 2017

A two-dimensional numerical investigation is performed to study the influence of slot width of multi-stage stationary floating overtopping wave energy devices on overtopping flow rate and performance. The hydraulic efficiency based on captured crest energy of different device layouts is compared with that of single-stage device to determine the effect of the geometrical design. The results show optimal trends giving a huge increase in overtopping energy. Plots of efficiency versus the relative slot width show that, for multi-stage devices, the greatest hydraulic efficiency is achieved at an intermediate value of the variable within the parametric range considered, relative slot width of 0.15 and 0.2 depending on design layouts. Moreover, an application of adaptive slot width of multi-stage device is investigated. The numerical results show that the overall hydraulic efficiency of non-adaptive and adaptive slot devices are approximately on par. The effect of adaptive slot width on performance can be negligible.

• Journal of the Korea Management Engineers Society
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• v.23 no.4
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• pp.73-86
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• 2018

Most electric products produced during the manufacturing process are produced after design and mass production under a given control standard. In particular, the development phase should present the criteria for the production process by setting appropriate limits based on the performance being targeted. Even if the standard of performance is set considering the performance of the process, measuring the performance of the product after actual production results will cause nonconformities with the expected results. Among the performance of electrical products, Energy standards represented by energy consumption efficiency continue to be of importance, and are mandatory standards that correspond to national standards in most countries. Therefore, statistical quality control of these standards shall basically have a large number of test equipment for each product, ensure sufficient test time and continuous sampling of product samples. In the end, companies that produce and sell electric appliances are striving to control mass production at a great cost, but this is not acceptable. This study presents basic characteristics of the energy efficiency of electrical products and proposes and conducts a case study on statistical production control methods for performance variation across products under the standards about domestic and international regulations.

• Journal of Information Technology Services
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• v.18 no.1
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• pp.79-90
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• 2019

Maximizing energy efficiency minimizes the energy consumption of computation, storage and communications required for IT services, resulting in economic and environmental benefits. Recent advancement of flash and next generation non-volatile memory technology and price decrease of those memories have led to the rise of so-called AFA (All-Flash Array) storage devices made of flash or next generation non-volatile memory. Currently, the AFA devices are rapidly replacing traditional storages in the high-performance servers due to their fast input/output characteristics. However, it is not well known how effective the energy efficiency of the AFA devices in the real world. This paper shows input/output performance and power consumption of the AFA devices measured on the Linux XFS file system via experiments and discusses energy efficiency of the AFA devices in the real world.

• Journal of Information Technology Services
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• v.14 no.3
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• pp.183-196
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• 2015

The concept of energy-efficient networking has begun to spread in the past few years, gaining increasing popularity. A common opinion among networking researchers is that the sole introduction of low consumption silicon technologies may not be enough to effectively curb energy requirements. Thus, for disruptively boosting the network energy efficiency, these hardware enhancements must be integrated with ad-hoc mechanisms that explicitly manage energy saving, by exploiting network-specific features. The IEEE 802.3az Energy Efficient Ethernet (EEE) standard is one of such efforts. EEE introduces a low power mode for the most common Ethernet physical layer standards and is expected to provide large energy savings. However, it has been shown that EEE may not achieve good energy efficiency because mode transition overheads can be significant, leading to almost full energy consumption even at low utilization levels. Coalescing techniques such as packet coalescing and interrupt coalescing were proposed to improve energy efficiency of EEE, but their implementations typically adopt a simple policy that employs a few fixed values for coalescing parameters, thus it is difficult to achieve optimal energy efficiency. The paper proposes adaptive interrupt coalescing (AIC) that adopts an optimal policy that could not only improve energy efficiency but support performance. AIC has been implemented at the sender side with the Intel 82579 network interface card (NIC) and e1000e Linux device driver. The experiments were performed at 100 M bps transfer rate and show that energy efficiency of AIC is improved in most cases despite performance consideration and in the best case can be improved up to 37% compared to that of conventional interrupt coalescing techniques.

• KIEAE Journal
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• v.15 no.3
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• pp.21-28
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• 2015

Purpose: In this study, we analyzed the energy performance levels and high-performance technology trends through the case studies of foreign high-performance buildings. Method: Buildings built within 10 years were selected for the analysis of recent trends. we analyzed the buildings of U.S.A, Germany and Japan using LEED certified buildings, Passive House certified buildings and CASBEE certified buildings database for the case study of foreign high-performance buildings. A total of 20 high-performance buildings including 14 cases in U.S.A, 4 cases in Germany and 4 cases in Japan were selected. Annual energy consumption levels for 20 high-performance buildings were collected with the actual energy consumption data or data from simulation programs officially recognized by DOE. Annual energy consumption were compared with the energy performance standard of the office buildings in the CBECS database, ASHRAE Standard 90.1-2004 and Building Energy Efficiency Rating System in Korea. Result: The order of the green strategies applied in the main categories are Renewable Energy(63%), Indoor Environment Control(51%), Envelope Improvement(44%) and HVAC System & Control(28%). Specified strategies most widely used in the sub-categories are high-performance Insulation (70%), High Efficiency Heating, Cooling Source Equipment(85%), Photovoltaic&Solar Thermal(80%) and Daylighting(80%).

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.250-255
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• 2011

A Photovoltaic/Thermal(PVT) solar system consists of PV module and thermal absorber plate which convert the absorbed solar radiation into electricity and heat. Meaningful researches and development (R&D) on the PVT technologies have been performed since the 1970s. This paper presents a review of the previous works covering the various types of PVT and their performance analysis in terms of electrical and thermal efficiency. This review compares electrical and thermal efficiency of the different types of PVT collectors and analyzes the parameters affecting PVT performance. Based on the literature review, box charmel type PVT with unglazed, or flat plate PVT with glazed have the highest efficiency among them. From the literature review, R&D should be carried out aiming at improving their overall electrical and thermal efficiency and cutting down the cost, making them more competitive in the energy consumption market.