Cheol-Yong Jang

A sensor-less LED dimming system based on daylight harvesting with BIPV systems

Artificial lighting in office buildings typically requires 30% of the total energy consumption of the building, providing a substantial opportunity for energy savings. To reduce the energy consumed by indoor lighting, we propose a sensor-less light-emitting diode (LED) dimming system using daylight harvesting. In this study, we used light simulation software to quantify and visualize daylight, and analyzed the correlation between photovoltaic (PV) power generation and indoor illumination in an office with an integrated PV system. In addition, we calculated the distribution of daylight illumination into the office and dimming ratios for the individual control of LED lights. Also, we were able directly to use the electric power generated by PV system. As a result, power consumption for electric lighting was reduced by 40 - 70% depending on the season and the weather conditions. Thus, the dimming system proposed in this study can be used to control electric lighting to reduce energy use cost-effectively and simply.

Real-time Energy Demand Prediction Method Using Weather Forecasting Data and Solar Model

This study was designed to investigate a method for short-term, real-time energy demand prediction, to cope with changing loads for the effective operation and management of buildings. Through a case study, a novel methodology for real-time energy demand prediction with the use of weather forecasting data was suggested. To perform the input and output operations of weather data, and to calculate solar radiation and EnergyPlus, the BCVTB (Building Control Virtual Test Bed) was designed. Through the BCVTB, energy demand prediction for the next 24 hours was carried out, based on 4 real-time weather data and 2 solar radiation calculations. The weather parameters used in a model equation to calculate solar radiation were sourced from the weather data of the KMA (Korea Meteorological Administration). Depending on the local weather forecast data, the results showed their corresponding predicted values. Thus, this methodology was successfully applicable to anywhere that local weather forecast data is available.

Cost-effective large-scale fabrication of diffractive optical elements by using conventional semiconducting processes.

In this article, we introduce a simple fabrication method for SiO(2)-based thin diffractive optical elements (DOEs) that uses the conventional processes widely used in the semiconductor industry. Photolithography and an inductively coupled plasma etching technique are easy and cost-effective methods for fabricating subnanometer-scale and thin DOEs with a refractive index of 1.45, based on SiO(2). After fabricating DOEs, we confirmed the shape of the output light emitted from the laser diode light source and applied to a light-emitting diode (LED) module. The results represent a new approach to mass-produce DOEs and realize a high-brightness LED module.

Microscopic and spectroscopic analyses of Pt-decorated carbon nanowires formed on carbon fiber paper.

We report the synthesis of carbon nanowires (CNWs) via chemical vapor deposition using catalytic decomposition of ethanol on nanosized transition metals such as Co, Fe, and Ni. Dip-coating process was used for the formation of catalytic nanoparticles, inducing the growth of CNWs on the surface of the carbon fiber paper (CFP). The liquid ethanol used as carbon source was atomized by an ultrasonic atomizer and subsequently flowed into the reactor that was heated up to a synthesis temperature of 600-700°C. Microscopic images show that CNWs of <50 nm were densely synthesized on the surface of the CFP. Raman spectra reveal that a higher synthesis temperature leads to the growth of higher crystalline CNWs. In addition, we demonstrate the successful decoration of platinum nanoparticles on the surface of the prepared CNWs/CFP using the electrochemical deposition technique.

Appropriate conditions for determining the temperature difference ratio via infrared camera

The temperature difference ratio is used to measure the thermal performance of a building envelope. Calculation of temperature difference ratio requires temperature differences between indoor and outdoor environments and wall surface temperatures, obtained here using an infrared camera. This approach performs well when the temperature differential between indoor and outdoor environments is greater than 10℃ and when wind speed is less than 3.0 m/s. We identify periods suitable for accurate evaluation of thermal insulation performance with an infrared camera, based on eight cities in Korea. The number of measureable hours ranges between 3183 and 1317 annually. Optimum periods for measurement are between November and March, specifically between 01:00 and 09:00 h. Measurements obtained during these periods can therefore be regarded as relatively accurate. Practical application: A thermal imaging camera provides an easy method for checking the insulation performance and construction conditions of a building. Conventionally, this would be checked experimentally, but thermal imaging allows easy visualization of conditions.

An Analysis of the Airtightness Performance and Heating Energy Demand According to Building Structural Characteristics -Focused on Newly Apartment Houses-

Purpose: The importance of building airtightness is increased as the demand and expectation of building energy efficiency is growing. Previous research only focused on airtightness of building openings only to improve building airtightness. However, the analysis of difference of airtightness performance according to the characteristic of building structure has not been performed. Therefore, this study analyzed the difference of airtightness performance according to building structural characteristics in a number of ways. Method: Airtightness that are classified as rigid-frame type or wall type are measured and analyzed the difference of airtightness performance between rigid frame type apartments and wall type apartments. This study calculated the heating energy demand and quantitatively analysis using ISO 13790. Futhermore, this study compared research trend of domestic airtightness performance with airtightness standards of the developed countries based on the field measurement. Result: Airtight performance of wall type is better than rigid frame type in terms of energy saving. The difference of heating energy demand between wall type and rigid frame type was .

Interior heating effect in an office building according to heat properties of light fixture

Purpose: Generally, 30% of the total energy consumption in office building is used for artificial indoor lightings, and almost 75-85% of electric power in fluorescent and Light-Emitting Diode (LED) lightings can be dissipated as a form of heat into indoor environment. The heat generated by indoor lightings can cause the increase of cooling load in office buildings. Thus, it its important to consider indoor lightings as a heat and light source, simultaneously. Method: In this study, we installed two kinds of indoor lightings including fluorescent and LED lightings and measured surface temperature of both indoor lightings. In addition, we obtained ambient temperature of indoor space and finally calculated total heat dissipated from plenum area and surface of lightings. Result: Total indoor heat gain was 87.17Wh and 201.36Wh in cases of six 40W-LED lightings and 64W-fluorescent lightings, respectively.