• Architectural research
• /
• v.20 no.3
• /
• pp.93-102
• /
• 2018

With the change in Earth's ecosystems due to climate change, a number of studies on zero energy buildings have been conducted globally, due to the depletion of energy and resources. However, most studies have concentrated on residential and office buildings and the performance predictions were made only in the design phase. This study verifies the zero-energy performance in the operational phase by acquiring and analyzing data after the completion of an exhibition building. This building was a retention building, in which a renewable energy system using a passive house building envelope, solar photovoltaic power generation panels, as well as fuel cells were adopted to minimize the maintenance cost for future energy-zero operations. In addition, the energy performance of the building was predicted through prior simulations, and this was compared with actual measured values to evaluate the energy performance of the actual operational records quantitatively. The energy independence rate during the measurement period of the target building was 123% and the carbon reduction due to the energy production on the site was 408.07 tons. The carbon reduction exceeded the carbon emission (331.5 tons), which verified the carbon zero and zero-energy performances.

• Journal of Power Electronics
• /
• v.19 no.1
• /
• pp.278-287
• /
• 2019

In this study, a zero-crossing spike current issue in a totem-pole bridgeless power factor correction (PFC) converter is comprehensively investigated for the first time. Spike current occurs when input voltage crosses zero, becomes a noise source, and causes severe common mode emission issues. A generation mechanism for electromagnetic interference (EMI) is presented to investigate the EMI problem caused by zero-crossing issue, and a noise spectrum due to this issue is predicted by a theoretical analysis based on the Fourier coefficient of an approximate spike current waveform. Furthermore, a noise reduction method is proposed and then improved to reduce the spike current. Experimental measurements are implemented on a GaN-based totem-pole bridgeless PFC converter, and the spike current can be effectively suppressed through the proposed method. Furthermore, the noise spectrums measured without and with the reduced zero-crossing spike current are compared. Experimental results validate the analysis of the noise spectrum caused by the zero-crossing spike current issue.

• Applied Science and Convergence Technology
• /
• v.26 no.5
• /
• pp.139-142
• /
• 2017

In this paper, InP-based InGaAs/InAlAs quantum cascade lasers(QCLs) providing nearly zero emission wavelength mismatch between the measured emission wavelength and the designed transition wavelength of QCLs is presented. The zero emission wavelength mismatch of QCLs influenced by both the accurate compositions and thicknesses of the low-pressure metal-organic vapor-phase epitaxy(MOVPE) grown InGaAs and InAlAs layers throughout the core and the abrupt composition transitions between InGaAs and InAlAs layers. The abrupt interfaces between InGaAs and InAlAs layers have been achieved throughout the core structure by means of controlling individually purged vent/run valves of a closed coupled showerhead reactor. In addition, maintaining substrate temperature constant during InGaAs/InAlAs core growth was a partial factor of uniformity improvement of QCLs. These approaches for reducing the possible discrepancies between the designed and MOVPE grown epitaxial structures could lead to improvement of QCL performance.

• KSBB Journal
• /
• v.22 no.2
• /
• pp.97-101
• /
• 2007

This study was performed to examine the availability of anaerobic digestion of the remainders caused by bacterial cellulose production process using food wastes. They maybe to be considered as others second pollution sources. Thus, this study was targeted to minimize content of organic material and to obtain more energy in those remnants using two-phase UASB reactor. The working volume of first hydrolysis fermentor was 35 L (total 55 L) and the second methane fermentor was 40 L (total 50 L). The organic loading rate of hydrolysis fermentor was 3 g-VS/L${\cdot}$day and 25,000 ppm of $COD_{cr}$ for methane fermentor. The hydraulic retention time was 18 days for hydrolysis reactor and 33 days for methane reactor. The hydrolysis reactor and methane reactor were performed at 35, 40$^{\circ}C$ respectively. For the efficient stable performance, the composition of organic wastes at each stage was as follow; Food waste with bacterial culture remnants (1 : 1), bacterial cellulose remnants, bacterial cellulose culture remnants with food wastes saccharified solids (1 : 1). When the anaerobic digestion was performed stably at each stage, the COD removal efficiency was 88, 90, 91 % respectively. At this time, methane production rate was 0.26, 0.34, $0.32m^3\;CH_4/kg-COD_{remove}$. As well as the values of anaerobic digestion at third stage were more higher than values of anaerobic digestion using food wastes. It is clearly to say that the food wastes zero-emission system constructed in our lab is more efficient way to treat and reclaim food wastes.

• Journal of the Korean Institute of Gas
• /
• v.26 no.6
• /
• pp.37-44
• /
• 2022

In this study, two low-swirl nozzles with the same SN (Swirl Number) but different mass ratio (m) of the core part and the swirler part were designed to perform an atmospheric pressure combustion test. For each nozzle, a combustion test was conducted according to the adiabatic flame temperature, and the flame structure, emissions, and combustion instability mode were identified. Although the flame structure was significantly different, the CO emission was similar, and the NOx emission was also more related to combustion dynamics than the flame structure. Combustion dynamics and NOx emission were identified while adjusting the convection delay time by changing the position of the fuel injection nozzle. It was confirmed that when the convection delay time is in the region of (3+4n)/4T±1/4T (n=0,1,2,...), the combustion instability is strong, and in the opposite case, the combustion instability is very weak.

• Journal of Korean Society of Environmental Engineers
• /
• v.38 no.7
• /
• pp.353-363
• /
• 2016

In this study, traditional treatment scenario of food wastes that collected and transported food waste is recycled in large treatment facilities and suggested treatment scenario of onsite zero discharge system that food waste is treated in housing complex were supposed. The scenarios were compared and analyzed by capital expenditure, oil consumption, $CO_2$ emission quantity, operating expenditure and management expenses. The capital expenditure, oil consumption and $CO_2$ emission quantity of small scale dispersion dealing method is the lowest compared to traditional treatment method. As a results, it is possible to obtain the effect that operating expenditure was reduced by 91% and management expenses was reduced by 40% with suggested treatment method. The treatment method that have low capital expenditure is tend to lower oil consumption and $CO_2$ emission quantity. The small scale dispersion dealing method have the lowest capital expenditure, oil consumption and $CO_2$ emission quantity and the linked method with sewage treatment have the highest expenditure and $CO_2$ emission quantity. Eventually, the optimal model of onsite zero discharge system in housing complex is small scale dispersion dealing method.

• Korean Chemical Engineering Research
• /
• v.46 no.2
• /
• pp.397-401
• /
• 2008

The nanoparticle-agglomerates are synthesized by laser ablation, which have the morphology of dendrite structure. The filtration performance of a conventional micron-fibrous metal filter was improved by adhering nanoparticle-agglomerates onto the filter surface. The Sintered-Nanoparticle-Agglomerates-adhered Filter (SNAF) adhered with nanostructured material was made by heat treatment after deposition of nanoparticle-agglomerates sintered in aerosol phase onto the micron-fibrous metal filter. As the sintering temperature increases, the pressure drop of the filter increases a little but the filtration efficiency increases remarkably. This is due to increase of surface area of nanoparticle-agglomerates adhered onto the micron-fibrous metal filter.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.6
• /
• pp.257-262
• /
• 2014

This paper describes an experimental study for heating performance that can be used in R-134a automobile heat pump systems. The heat pump system is widely studied for heating system in zero-emission vehicles to attain both the small power consumption and the effective heating of the cabin. This paper presents the experimental results of the influence on heating capacity and coefficient of performance of heat pump system. Tests were performed with different sizes of internal and external heat exchangers, and refrigerant flow rate was also considered in two-way flow devices. In addition, the heat, air, and water sources with the heat pump system were examined. The experimental results with the heat pump system were used to analyze the impact on performances. The best combination of performance was A-inside heat exchanger, B-outside heat exchanger, and B-flow device, respectively. In addition, a water heat-source was found to give roughly 40% of better performance than an air heat-source heat pump system.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.04a
• /
• pp.168-169
• /
• 2022

The continuous development of science and technology since the Industrial Revolution and the development of human civilization are based on the use of fossil fuels. However, the use of fossil fuels is increasing the greenhouse gas, the main cause of global warming, and global warming is an extreme climate anomaly that is rapidly increasing human and material damage. Therefore, efforts are being made worldwide to return greenhouse gases to pre-industrial levels. In Korea, 2050 carbon neutrality has been set as a major policy and efforts are being made to curb carbon emissions in the overall industry. Carbon emission suppression is based on the minimization of fossil fuel use, and research and development are underway on building a zero-emission house that minimizes the energy used in buildings in the construction field. Therefore, in this study, as part of the zero-emissions water system construction, waste resources generated at industrial sites were utilized and an integrated lightweight concrete solar panel grafted with a concrete lightweight panel and solar panel was manufactured and the possibility of its use was evaluated.

• Journal of the Society of Naval Architects of Korea
• /
• v.60 no.3
• /
• pp.146-154
• /
• 2023

Efforts have been made to reduce the greenhouse gas emissions from ships by limiting the energy efficiency index, and net zero CO₂ emission was proposed recently. The most ideal measure to achieve zero emission ship is electrification, and fuel cells are considered as a practical power source of the electrified propulsion system. The electric efficiency in the electrochemical reaction of fuel cells can be achieved up to 60% practically. The remaining energy is converted to heat energy but most of them are dissipated by cooling. In the author's previous research, a hybrid propulsion system utilizing not only electricity but also heat was introduced by combining electric motor and steam turbine. In this article, long term efficiency is evaluated for the introduced hybrid propulsion system by considering a virtual 24,000 TEU class container carrier model. To reflect a more practical operating condition, the actual navigation data of a similar real ship in the real world were collected from automatic identification system data and applied. From the result, the overall efficiency of the hybrid propulsion system is expected to be higher than a conventional electric propulsion fuel cell ship by 30%.