Dok-Ki Jo

Operation Results of Dish-Stirling Solar Power System

As the final step for developing a small-scale solar thermal power generation technology in Korea, a demonstration project for a dish-Stirling power system has been carried out by KIER. During the two years project period, 10 kW dish-Stirling power system was built in Jinhae city and successful solar operations were demonstrated. The system consists of mechanical part for solar tracking, parabolic dish-type concentrator, a number of mirror facets, Stirling engine generator, and control/monitoring devices. Close analysis of operation results revealed that the minimum DNI value for power generation by the system was around 200 W/m2 and the efficiency of solar-to-power conversion reached over 19 % at above 400 W/m2 DNI condition. In this paper an example of typical clear day operation and analysis results were introduced.

Electro-Optical Characteristics and Analysis of 1×1 mm 2 Large-Area InGaN/GaN Green LED

We investigated the effects of piezoelectric field on the electro-absorption characteristics in InGaN/GaN multiple-quantum well (MQW) green light emitting diodes (LED). Double crystal X-ray diffraction measurement was performed to study the crystalline property and indium (In) composition in the MQW active layer. To measure the electro-luminescence and electro-reflectance (ER) spectroscopy, we fabricated the large-area green LED chip. The piezoelectric field inside the LED structure was evaluated from the Vcomp in active layer by the ER spectra. Finally, we analyzed the electro-absorption characteristics of the green LED by using the photo-current spectroscopy.

An Evaluation of Uncertainty for Reference Standards Solar Radiation Data

The energy makes the basic element which improves the quality of life with motive power of industry and life. However, using the fossil fuel resources was restricted through it`s abuse and exhaustion, and that cause a global warming resultingly. According to the reason, the world increased the interest that are stability and use of new and renewable energy which is clean energy with environment. Therefore, the property data of new and renewable is needed for developing and supplying the energy. In other words, the data of new and renewable energy becomes the standards for supply and evaluation of new and renewable energy with development of industry and technology. Also, the necessity came to the fore as the reference and standards of new and renewable energy data. Therefore, in this study, we evaluate and collect the solar radiation data as the new and renewable data and process the collected data through the standards for valuation. We evaluate uncertainty with standards which are NREL, WMO, and GUM. Whereby the data becomes reference standards data and gains the credibility. For the reliability data, we correct the measuring instrument with correction period. Using the DQMS and SERI QC, we efficiently manage and evaluate the solar radiation data. As a result, we evaluate uncertainty as 1,120 case about 16 area. we achieve credibility of data from evaluated solar radiation data and provide an accurate information to user. The annual average of horizontal radiation presents between 1,484 and 4,577, then the uncertainty evaluates from 163 to 453. The error of uncertainty presents smaller than the measurement values. So, we judge a credibility of data by expression of reliability quantitatively. In additional, the reference standards data which is possible to approach anywhere will be used for the supporting related industry and policy making.

A Change of Yearly Atmospheric Clearness Index in Korea

Since the atmospheric clearness index is main factor for evaluating atmosphere environment, it is necessary to estimate its characteristics all over the major cities in Korea. We have begun collecting clearness index data since 1982 at 16 different cities and considerable effort has been made for constructing a standard value from measured data at each city. The new clearness data will be extensively used by evaluating atmospheric environment as well as by solar application system designer or users. Yearly mean 64% of the atmospheric clearness index was evaluated for clear day all over, and significant difference of horizontal global insolation is observed between 1982~1986 and 1987~1991, 1992~1996, 1997~2001, 2002~2009 through 16 different cities in Korea.