• Journal of Korea Multimedia Society
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• v.19 no.11
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• pp.1891-1899
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• 2016

Recently food problem and crop disaster have been increased continuously because of the meteorological changes. These cause rising cost for crops continuously and irregularly. Some researchers have studied straight structure of device for hydroponics and plant factory previously to solve a fundamental part of these problems. However, there are several problems such as limited crop cultivation space, providing irregular nutrients for crops, and lack of monitoring interfaces. For them, we propose an optimal growth and development crops management system using light source tracking and recirculation of nutrient solution method to supply nutrient continuously based on IoT. In order to evaluate the performance of our system, we compared and analyzed in terms of two viewpoints, the tracking analysis for natural light source measurement and the growth of crops through artificial light, LED, respectively. We confirmed that the higher the duty ratio of LED, the larger the crop's size, particularly. As well as, for about 1 month, we compared with the existing natural light growing environment and that of our system. It was confirmed that the size of the crops grown through our system is about three times larger than that of natural light natural crops.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.255-258
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• 2004

The SAR(Solar Array Regulator) of KOMPSAT(Korea Multi Purpose SATellite)-1, 2 regulates a photovoltaic power according to the duty ratio commands of the ECU. But the ECU has so many other jobs that it can not calculate the solar array condition immediately. It means the SAR cannot always generate the maximum power of a photovoltaic. Nowadays, the commercial photovoltaic systems are using a controller operated by digital processing. But the usage for satellite is not adaptable. It is not easy to find the processor of the space grade and the price is expensive. So in this paper, the simple analog MPPT(Maximum Power Point Tracking) algorithm is proposed for the small satellite in LEO. This algorithm does not need any calculation of power by multiplication of voltage and current md a measurement of the solar array temperature. It is consist of only two sample and hold circuits, two comparators, a flip-flop, and an integrator. The proposed MPPT algorithm is verified by the simulation and experimental.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.283-287
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• 2005

In this paper, one general approach is proposed for the design of power system that can be applicable for next generation LEO satellite application. The power system consists of solar panels, battery, and power control and distribution unit(PCDU). The PCDU contains solar array modules, battery interface modules, low-voltage power distribution modules, high-voltage distribution modules, heater power distribution modules, on-board computer interface modules, and internal DC/DC converter modules. The PCDU plays roles of protection of battery against overcharge by active control of solar array generated power, distribution of unregulated electrical power via controlled outlets to bus and instrument units, distribution of regulated electrical power to selected bus and instrument units, and provision of status monitoring and telecommand interface allowing the system and ground operate the power system, evaluate its performance and initiate appropriate countermeasures in case of abnormal conditions. We review the functional schemes of the main constitutes of the PCDU such as the battery interface module, the auxiliary supply module, solar array regulators with maximum power point tracking(MPPT) technology, heater power distribution modules, spacecraft unit power distribution modules, and instrument power distribution module.

• Journal of the Korean Solar Energy Society
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• v.31 no.1
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• pp.31-36
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• 2011

CF(Circular Fresnel) POF(Plastic Optical Fiber) daylighting system is a beam daylighting system utilizing solar direct beam radiation. In this study, a CF POF daylighting system has been introduced, developed and applied to KIER test buildings. The CF POF daylighting system consists of three parts: light collector, light transmitter and light diffuser. The light collector includes a Circular Fresnel lens focusing solar direct illuminance by sun tracking. The light transmitter contains the POF cable which has light transmission loss of 4.5% per meter. The light diffuser has about 80% diffuser efficiency. This study aims to evaluate of POF daylighting system performance. At the results of a CFPOF system performance evaluation, the theoretical CFPOF system efficiency was 41.9% and the actual CFPOF system efficiency at the KIER test building was 37.5%. The difference was due partly to the connecting efficiency.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.5
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• pp.21-33
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• 2012

This paper presents the new maximum power point tracking(MPPT) control of the photovoltaic(PV) module integrated converter(MIC) system considering the shadow influence. The output characteristics of the solar cell is a nonlinear and affected by a temperature, the solar radiation and influence of a shadow. Particularly, MIC system is very sensitive to the shadow influence because the capacity is very small. In order to increase an output and efficiency of the solar power generation, the maximum power point(MPP) obeying control are necessary. Conventional perturbation and observation(PO) and Incremental conductance(IC) are the method finding MPP by the continued self-excitation vibration. The MPPT control is unable to be performed by rapid output change affected by the shadow. To solve this problem, the new control algorithm of the multi-level in which the step value changes by output change is presented. In case there are the solar radiation, a temperature and shadow influence, the presented algorithm treats and compares the conventional control algorithm and output error. In addition, the validity of the algorithm is proved. through the output error response characteristics.

• ETRI Journal
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• v.45 no.3
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• pp.519-533
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• 2023

This paper implements a simultaneous solar and thermal energy harvesting system, as a hybrid energy harvesting (HEH) system, to convert ambient light into electrical energy through photovoltaic (PV) cells and heat absorbed in the body of PV cells. Indeed, a solar panel equipped with serially connected thermoelectric generators not only converts the incoming light into electricity but also takes advantage of heat emanating from the light. In a conventional HEH system, the diode block is used to provide the path for the input source with the highest value. In this scheme, at each time, only one source can be handled to generate its output, while other sources are blocked. To handle this challenge of combining resources in HEH systems, this paper proposes a method for collecting all incoming energies and conveying its summation to the load via the current mirror cells in an approach similar to the maximum power point tracking. This technique is implemented using off-the-shelf components. The measurement results show that the proposed method is a realistic approach for supplying electrical energy to wireless sensor nodes and low-power electronics.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_1
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• pp.967-976
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• 2023

Currently, with the thriving development in the field of solar energy, the widespread adoption of solar grid-connected power conversion systems is rapidly expanding. As the market continues to grow, the efficiency of solar power conversion systems is steadily increasing, while prices are rapidly decreasing. Photovoltaic panels often produce low output voltages, and Boost converters are commonly employed to elevate and stabilize these voltages. They are also utilized for implementing Maximum Power Point Tracking (MPPT), ensuring the full utilization of solar power generation. Recently, synchronous control techniques have been introduced, using controllable switching devices like Si IGBT or SiC MOSFET to replace the diodes in the original circuits. However, this has raised concerns related to costs. This paper offers a compromise solution, considering both the performance and economic factors of the converter. It proposes a hybrid high-efficiency synchronous converter structure that combines Si IGBT and SiC MOSFET. Additionally, the proposed topology has been practically implemented and tested, with results confirming its feasibility and cost-effectiveness.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.2
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• pp.110-118
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• 2008

The regulated peak power tracking (RPPT) systems such as the series structure and the parallel structure are commonly used in the satellite space power system. However, this structure processes the solar array power to the load through two regulators during one orbit cycle, which reduces the energy transfer efficiency. The series-parallel structure for the RPPT system can improve the power conversion efficiency, but an additional regulator increases the cost, size and weight of the system. In this paper, a simplified series-parallel space power system that consists of two regulators is proposed. The proposed system has the similar energy transfer efficiency with the series-parallel structure by adding one switch to the series structure, which reduces the cost, size and the weight. The large signal stability analyses is provided to understand the four main modes of system operation. In order to compare the energy efficiency with a series structure, the simulation is performed. The experimental verifications are performed using a prototype hardware with TMS320F2812 DSP and 200W solar arrays.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.7
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• pp.876-884
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• 2012

The worldwide CPV(Concentrated Photo Voltaic) market has been increased rapidly due to the increase in large-scale PV(Photo Voltaic) plants which are situated in sun-rich areas with either a Mediterranean or equatorial-type climate. CPV systems are arguably some of the most important devices in the production of electricity within regions with a sun-rich climate, particularly those which benefit from abundant direct solar irradiation. We have developed a 500X CPV module with rated power of 170Wp. The CPV module must satisfy the constraint of having a sensitive tracking accuracy due to the limited tolerance of the acceptance angle in intrinsic optical design. In this study, the module's acceptance angle used was designed with a tolerance angle of ${\pm}1^{\circ}$ in the secondary optics design. In general, non-concentrated module type 2-axis trackers have a tolerance angle larger than ${\pm}1^{\circ}$ due to standard silicon-type modules which are insensitive to the tracking accuracy of the sun. They have a tolerance angle of ${\pm}2{\sim}4^{\circ}$, which fails to exert a significant influence on the performance of the module. This paper provides a study of an experimental variation of the efficiency of the CPV module in terms of its tracking accuracy. Also, the performance of the module is studied from the perspective of temperature and direct irradiation.

• Journal of The Korean Astronomical Society
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• v.42 no.1
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• pp.1-7
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• 2009

The e-CALLISTO is a global network of frequency-agile solar radio spectrometers that was constructed in a collaboration between Swiss Federal Institute of Technology Zurich (ETH Zurich) and local host institutes. It is intended to monitor solar radio bursts 24 hours a day in frequency range between 45 MHz and 870 MHz. One of e-CALLISTO spectrometer was installed at Korea Astronomy and Space Science Institute (KASI) in 2007 October. The spectrometer gets signals from a horizontally polarized log-periodic antenna mounted on an automatic Sun-tracking system. Tracking status and data are monitored in Space Weather Monitoring Laboratory (SWML) of KASI in real time, and flare time data are transferred to ETH Zurich data archive daily. Using this spectrometer we obtained a couple of type II solar radio bursts on 2007 December 31, and found that these bursts are associated with a CME which occurred on the east limb.