• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.1
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• pp.44-49
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• 2015

Ceiling cooling and heating system that consider load arrangement and space in the ceiling needs to be developed. Therefore, experimental and economic changes were done to verify the performance of compact type VAV. The test results were as follow. 1) Noise test result, measuring approximately 50.4 dB~56.6 dB (before ceiling in landfill), had a better ceiling deadline than the current measure, about a 10 dB noise reduction, so that the office baseline (40~50 dB) noise was judged to be less than test. 2) For the static pressure test result, taking out an outside hydrostatic 25 mmAq, 24.8 mmAq was measured, respectively, at the point. 3) For the life-cycle cost analysis result, the initial investment cost, maintenance replacement costs, and maintenance costs increased 0.2%, but the energy savings ratio was 19.5% while the whole life cycle savings of 40 years LCC was reduced 11.9%.

• Journal of Drive and Control
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• v.16 no.4
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• pp.56-64
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• 2019

Recently, as the environmental regulation for earth moving equipment has been tightened, advanced systems using electronic control have been introduced for energy savings. An IMV(Independent Metering Valve), which consists of four 2-way valves, is one of the electro-hydraulic control systems that provides more flexible controllability and potential for energy savings in excavators, when compared to the conventional 4-way spool valve system. To fully realize an IMV, a two-stage bi-directional flow control valve which can regulate the large amount of flow in both directions, should be developed in advance. A simple design that allows proportional flow control to apply the pilot pressure from the current-controlled solenoid to the spring loaded flow control spool and thus valve displacement, is proportional to the solenoid current. However, this open-loop type valve is vulnerable to flow force which directly affects the valve displacement. Force feedback servo of which the position loop is closed by the feedback spring which interconnects the solenoid valve and flow control spool, could compensate for the flow force. In this study, linearity for the solenoid current input and robustness against load pressure disturbance is investigated by linear analysis of the static nonlinear equations for the IMV proportional flow control valve with feedback spring. Gains of the linear system confirm the performance improvement with the feedback spring design.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.3
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• pp.1-8
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• 2012

This study investigated current status of lighting environment, residents' awareness of lighting and lighting use according to behavior in the living room of apartment to determine current lighting trends and their related problems. The living rooms of newly-built apartment units(133~165[$m^2$] and larger than 166[$m^2$] within the past five years) were examined. The results are summarized as follows. 1. Resident satisfaction with current living room lighting was the highest in 'illumination' and the lowest was 'energy savings' regardless of the size of living room. 2. This kind of ceiling lighting layout, 133~165[$m^2$] unit used central lighting and larger than 166[$m^2$] units used central lighting and cove lighting. Regarding light sources, 133~165[$m^2$] linear FL, halogen, larger than 166[$m^2$] bulb-type FL are widely used. LED are now being found in the living room corridor and kitchen walls of newly-built apartment houses. 3. Watching TV and reading books were commonly behaved in the living room. Conversations between family, having desserts, resting, housekeeping, and entertaining were usually done weekdays, while having desserts and conversations between family were done weekends. Use of lighting as main behaviors is properly and differently required due to the distinct uses of lighting as residents' behaviors or their life style.

• Journal of the Korean Institute of Rural Architecture
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• v.17 no.2
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• pp.9-16
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• 2015

This study comparatively analyzed thermal characteristics of the green color, which is currently used the most, and other various colors of a rooftop urethane water proofing sheet. This study also analyzed the cooling performance by color of the water proofing sheet that fused cooling paints, and presented the effective water proofing sheet color for building energy savings. The experimental results are as follows: (1) The value of L (brightness) diminished, and brilliance also became lower from the white color to the black color, and thus, it was confirmed that relatively more heat was absorbed. In a and b chromaticity, which is the color attribute that ignores brightness, no special relationship was identified. (2) Considering that the cooling performance effect is bigger in summer than winter, due to heat reflection, the white water proofing sheet is more effective in building energy savings than the green water proofing sheet that is currently used the most. (3) The water proofing sheet's color has an impact more on cooling performance than the color of the background side of a structure on which water proofing sheet is installed. The experiment object of gray, of which background side is similar to cement mortar, was lower by $5.7^{\circ}C$ than the white background side.

• Journal of Drive and Control
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• v.15 no.4
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• pp.39-47
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• 2018

Recently, as environmental regulations for earth-moving equipment have been tightening, advanced systems such as electronic control, have been introduced for energy savings. An IMV (Independent Metering Valve) consisting of four 2-way valves, is an electro-hydraulic control systems that provides more flexible controllability, and potential for energy savings in excavators, when compared to the conventional 4-way spool valve system. To fully maximize use of an IMV, the bi-directional flow control valve that can regulate a large amount of flow in both directions, should be adopted. The hydraulic circuit of an IMV applied to an excavator from an overseas construction equipment company, reveals the flow control valve with the compound of proportional solenoid valve for first stage, and 2-way spool valve for the second stage. Moreover, the two spools are interconnected by a feedback spring, presumed to compensate for flow force acting on the second stage spool. This paper addresses the static analysis of flow control valve in an IMV to investigate the improvement of robustness, against flow force by the feedback spring. From the steady-state analysis of flow control valve model, it can be concluded that the feedback spring facilitates maintaining linearity of spool displacement for control input, and relatively constant flow for load disturbance.

• ETRI Journal
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• v.33 no.6
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• pp.973-976
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• 2011

This letter describes an efficient technique for maximum power point tracking (MPPT) of an energy harvesting device. It is based on controlling the device voltage at the point of maximum power. Using a microcontroller with a power saving technique, the MPPT algorithm maintains the maximum power with low power consumption. An experiment shows that the algorithm maximizes the energy transfer power using an energy management IC fabricated in a 0.18-${\mu}m$ process. Compared to direct energy transfer to a battery, the proposed technique is more efficient for low-energy harvesting under variable conditions.

• Journal of the Korean Solar Energy Society
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• v.31 no.4
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• pp.34-40
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• 2011

Apartment Housing has been increasing steadily, particularly our current super high-rise apartment houses that represent the culture has become a trend in Korea. These super high-rise apartment houses' curtain wall system increases heating and cooling loads, it is expected to vary by each unit's thermal properties. In this study, measured indoor environment and energy simulation results were compared to actual energy consumption. As a result, the various factors that affect heating and cooling loads, such as direction, plan type and glazing area, influence each unit's load characteristic. In particular, according to the electricity costs savings behavior, the occupant's thermal discomfort is expected to be large in summer. Therefore, to reduce heating and cooling load for each unit requires a reasonable plan.

• Resources Recycling
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• v.23 no.5
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• pp.44-54
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• 2014

A standard plastic garbage bag which was discarded from Incheon Metropolitan City was composed of 4.5% recyclable resources (aluminum cans 0.2%, steel cans 2.5%, glass 1.8%), 92.5% resources with recoverable energy (papers 23.0%, plastics 15.5%, combustible etc. 54.0%) and 3.0% non-combustible etc. Recycling is more effective than landfilling for aluminum cans, steel cans, and glass. The energy recovery process using solid refuse fuel (SRF) is more effective than incineration for papers and plastics. Incineration is more effective than recycling for combustible etc. 2,068,948 Million Btu of total energy savings and 21,008 $MTCO_2E$ of total GHG reductions were obtained by the application of the proposed scheme. The total energy savings were equivalent to an economic benefit of 422 billion won per year. The total GHG reductions were equivalent to a GHG benefit of 4,119 passenger cars not running per year. The lower calorific value of the combustible materials was obtained to be 1,936 kcal/kg of papers, 5,079 kcal/kg of plastics and 2,462 kcal/kg of combustible other resources, respectively. If papers and plastics are properly mixed, the mixture can be used as SRF. The lower calorific value of combustible other resources does not meet the quality criteria for refuse derived fuel, therefore its components are inappropriate to used as solid refuse fuel.

• International Journal of Advanced Culture Technology
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• v.2 no.2
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• pp.1-6
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• 2014

In this paper, we propose an intelligent streetlight system that has a complex sensor module of temperature, humidity, luminance and motion detection and controlled by the fuzzy logic based central monitoring system in order to get flexible and precise manipulation of the streetlight system in USN environment. The proposed streetlight system provides low power consumption and high efficiency by using sensed data from the complex sensor module, which were collected, processed, and analyzed by the fuzzy logic based central monitoring system. The performance of the proposed streetlight system is to be evaluated by a simulation study in terms of power savings and safety at the fields constructed as a test-bed under several suggested scenarios. Finally, we know that the proposed intelligent streetlight system can maximize the energy savings efficiently with the fuzzy logic based central monitoring system and selective remote dimming control by connecting it to the wireless ubiquitous sensor network (USN) using a Zigbee module.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.10
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• pp.936-941
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• 2000

Advanced space transportation systems, such as the National Aerospace Plane or an Orbital Transfer Vehicle, have atmospheric maneuvering capabilities. For such vehicles the use of aeroassisted orbital transfer from a high Earth orbit to a low Earth orbit, with unpowered flight in the atmosphere, has the potential for significant fuel savings compared to exoatmospheric Hohmann transfer. However, to exploit the fuel savings that can be achieved by using the Earths atmosphere to reduce the vehicles energy, a guidance law is required, and it must be able to handle large unpredictable fluctuations in atmospheric density, on the order of ${\pm}$50% relative to the 1962 US Standard Atmosphere. In this paper aeroassisted orbital transfer is considered as a differential game, with Nature controlling the atmosphere density to yield a worst case (min-max fuel required) atmosphere, from which the guaranteed playable set boundary are achieved. Inside the playable set, it is guaranteed that the vehicle achieves the optimal atmospheric exit condition for the minimum fuel consumption regardless of the atmospheric density variations.