Earticle

최근 급속한 산업화로 인하여 자원 문제와 환경문제가 대두되고 있다. 이에 따라 태양전지가 발달하여 위의 문제를 어 느 정도 해결하였지만, 1990년도부터 보급된 모듈이 15~20년의 수명으로 인하여 현재 폐 태양전지모듈 발생으로 인한 토양오염 문제가 급부상하고 있다. 폐 태양전지 모듈 발생량이 증가할 것으로 예상됨에 따라 폐 태양전지 모듈로부터 실 리콘 회수에 관한 연구를 수행하였다. 태양전지 모듈은 은(Ag), 실리콘(Si), 알루미늄(Al) 등으로 이루어져 있다. 태양전 지로부터 실리콘(Si)을 회수하기 위해서 인산과 질산을 사용하였으며, 100oC에서 2 M의 인산을 이용하여 99.99%의 Al 을 제거할 수 있었으며, Ag의 경우 40oC에서 2 M의 질산을 이용하여 99.99% 제거할 수 있었다. 또한, EDS(Energydispersive X-ray spectroscopy)와 ICP(Inductively Coupled Plasma)를 이용하여 유가금속(Al, Ag)과 실리콘(Si)의 순도 를 분석하였다.

Resource and environmental problems are emerging due to rapid industrialization. As a result, although solar cells have developed and solved the above problem to a certain extent, the soil pollution problem caused by generation of waste solar cell modules has emerged due to the life of 15 to 20 years of the modules supplied since 1990. As the generation of waste solar cell module is expected to increase, a study on the recovery of silicon from the waste solar cell module was carried out. The solar cell module is composed of silver (Ag), silicon (Si) and aluminum (Al). Phosphoric acid and nitric acid were used to recover silicon (Si). The removal ratio of Al from the solar cell was 99.99% using 2 M phosphoric acid at 100oC. In case of Ag, the removal ratio was 99.99% using 2 M nitric acid at 40oC. We also analyzed the purity of valuable metals (Al, Ag) and silicon (Si) using Energy Dispersive X-ray Spectroscopy (EDS) and Inductively Coupled Plasma (ICP).

본 연구에서는 다양한 방법들을 이용하여 태양전지 폐 모듈로부터 태양전지의 주요 구성요소인 실리콘과 강화유리를 회수하는 연구를 수행하였다. 강화유리는 유기용매를 사용하여 회수하였고, EVA수지는 열처리를 통하여 완전히 제거하였다. 실리콘은 계면활성제를 첨가한 혼산용액을 이용하여 표면물질을 제거하고 회수하였다. 90%이상의 높은 실리콘 회수율을 얻었다. 본 연구에 의하여 얻어진 강화유리와 실리콘은 태양전지 모듈의 원료로 재활용되어 실리콘 공급부족 문제해결, 태양전지 제조원가 및 폐기물 처리비용 절감에 기여할 것으로 기대된다.

We devised a procedure for the recovery of silicon and tempered glass from waste photovoltaic (PV) modules using optimized conditions. The tempered glass was recovered without any damage using organic solvents. The surface material is removed by applying an acid solution on the surface of the PV cell. Through our proposed method, we offer a much more efficient approach for recycling solar cells with a surfactant than the conventional method. This process, we obtained pure silicon with a yield of 90% by chemical treatment with the surfactant at room temperature for 18 min. The silicon yield was characterized using an inductively coupled plasma-atomic emission spectrometer.

Traditional Photovoltaic (PV) mathematical models have advantage of high accuracy, but its characteristics are multi-parameters and non-linear, which makes it difficult to be solved. Obviously, these are not suitable for engineering design since it requires both complexity and accuracy. In this paper, a simplified precision engineering PV mathematical model is proposed based on analysis of double diode PV cells mathematical model, and also gives a parameter calculation method based on Newton-Raphson method. Four different kinds of PV materials and variable resistance parameter characteristics are separately tested under different irradiance and temperature conditions. The results show that the proposed model can quickly and accurately reflect the PV model I-V and P-V characteristics, which has good versatility and sensitivity, and provides strong support for PV system related research.

The location of PV systems in distribution system has been increased as one of countermeasure for global environmental issues. As the operation efficiency of PV systems is getting decreased year by year due to the aging phenomenon and maintenance problems, the optimal algorithm for state diagnosis in PV systems is required in order to improve operation performance in PV systems. The existing output prediction algorithms considering various parameters and conditions of PV modules could have complicated calculation process and then their results may have a possibility of significant prediction error. To solve these problems, this paper proposes an optimal prediction algorithm of PV system by using least square methods of linear regression analysis. And also, this paper presents a performance evaluation algorithm in PV modules based on the proposed optimal prediction algorithm of PV system. The simulation results show that the proposed algorithm is a practical tool of the state diagnosis for performance improvement in PV systems.

Most PV modules are fabricated by 6 cell-strings with solar cells connected in series. Moreover, bypass diodes are generally installed every 2 cell-strings to prevent PV modules from a damage induced by current mismatch or partial shading. But, in the case of special purpose PV module, like as BIPV (Building Integrated Photovoltaic), the number of cell-strings per module varies according to its size. Differ from a module employing even cell-strings, the configuration of bypass diode should be optimized in the PV module with odd strings because of oppositely facing electrodes. Hence, in this study, electrical characteristics of special purposed PV module with odd string was empirically and theoretically studied depending on arrangement of bypass diode. Here, we assumed that PV module has 3 strings and the number of bypass diodes in the system varies from 2 to 6. In case of 2 bypass diodes, shading on a center string increases short circuit current of the module, because of a parallel circuit induced by 2 bypass diodes connected to center string. Also, the loss is larger, as the shading area in the center string is enlarged. Thus, maximum power of the PV module with 2 bypass diode decreases by up to 59 (%) when shading area varies from 50 to 90 (%). On the other hand, In case of 3 and 6 bypass diodes, the maximum power reduction was within about 3 (W), even the shading area changes from 50 to 90 (%). As a result, It is an alternative to arrange the bypass diode by each string or one bypass diode in the PV module in order to completely bypass current in case of shading, when PV module with odd string are fabricated.

In this paper, PV modules using a low-temperature conductive film(LT-CF) as a bonding material between a cell and a solder free ribbon were produced and chracterized, which is more environmental-friendly, cost effective and high efficient. Mainly, filed electrical performance of PV modules using three different types of bonding material; a convetional solder ribbon(SR), a LT-CF and a light-capturing Ribbon(LCR) were compared to comfirm the feasibility of LT-CF as a bonding material. The filed test were conducted for 3 months and results were discussed in terms of amount of output energy production and efficiency.

Photovoltaic (PV) modules output changes noticeable with variations in temperature and irradiance. In general it is has been shown that a $1^{\circ}C$ increase in temperature results in a 0.5% drop in output. In this paper, seven PV module types are analyzed for variation in temperature and irradiance, and the resulting output characteristics examined. The 7 modules types utilized are as follows; 3 poly crystalline modules, 2 single crystalline modules, 1 back contact single crystalline module and 1 HIT module. 3 groups of experiments are then conducted on the modules; tests with varying irradiance values, tests with module temperature varying under $25^{\circ}C$ and tests with module temperature varying over $25^{\circ}C$. The experiments results show that as temperature rises the follow is observed; Pmax decreases by 0.6%, Voc decreases by about 0.4%, and Isc increasing by between 0.03%${\sim}$0.08%. In addition, an irradiance decrease of 100 w/m2 translates into a 10% drop in Pmax.

The efficiency of solar cell was about 4[%] in initial stage of photovoltaic industry, but it has quite a lot of efficiency through technology advances. Today, the efficiency of c-Si solar cells is about 17 to 19[%] and the efficiency of PV modules is about 14 to 15 [%]. We called that electrical losses occurred in the Conversion of solar cells to PV modules are CTM loss(Cell To Module loss), the CTM loss typically has a value of about3~5[%]. The more efficiency of solar cell increase, differences are larger because the efficiency decrease owing to physical or technical problems occurred in the Conversion of solar cells to PV modules. In this study, the power loss factors occurred in the Conversion of solar cells to PV modules are analyzed and it is proposed that how to reduce losses of the PV module. The types of power loss factor are (1)losses of front glass and encapsulant(generally EVA sheet), (2)losses by sorting miss, (3)losses by interconnection, (4)losses by the field aging of PV modules. In further study, experimental and evaluation will be conducted to make demonstrate for proposed solutions.

최근 박막 태양전지에 대한 관심이 증대되면서 이를 이용한 태양광 PCS에 대한 연구가 활발히 진행되고 있다. 박막 태양전지는 모듈의 특성상, 기존의 비절연형 PCS를 사용하여 시스템을 구성하기에 적합하지 않다. 본 논문에서는 승압형 컨버터, 계통 연계형 단상 인버터 2단으로 구성된 비절연형 PCS에 고주파 절연형 컨버터가 추가되어 3단으로 구성된 박막모듈용 3kW급 고주파 절연 PCS를 소개한다. 또한 각종 시험 결과를 통해 적합성 및 성능을 검증하였다.

Int this paper, we studied the analysis on long-term durability and output power characteristics of PV modules by variation on local thermal property. Using 5 modules(80W), we measured the maximum output power change during the test period. And the optical transmittance of glass was compared with PV module's maximum power fluctuation. The external environment change effected contamination on the entire or local surface of module. This caused the local temperature variation of each solar cell on PV module. The specific analysis is shown in the following paper.

A bidirectional flyback converter is a suitable topology for use in a PV-to-bus differential power processing (DPP) module for PV applications due to its electrical isolation capability, bidirectional power transfer, high step-up ratio, and simple circuit structure. However, the bidirectional flyback converter design should consider the effect of the output-side power switch utilized for bidirectional operation compared with that of the conventional flyback converter. This study presents the structure and design methodology of the bidirectional flyback converter for a PV DPP module. Magnetizing inductance is designed by calculating the power loss of converter components within the rated load range under the discontinuous conduction mode, which is unaffected by the reverse recovery characteristics of the anti-parallel diode of the output-side power switch. The validity of the proposed design methodology is verified using a 25 W bidirectional flyback converter prototype. The operational principles and the performance of the DPP operation are verified using practical DPP modules consisting of bidirectional flyback converters implemented according to the proposed design methodology.

양방향 플라이백 컨버터는 1, 2차 간 절연이 가능하고, 양방향 전력전달을 할 수 있으며, 전력밀도가 높기 때문에 PV 용 차동 전력 조절기 (DPP) 모듈의 응용분야에 적합하다. 차동 전력 조절기 모듈 용 플라이백 컨버터는 양방향 동작을 위해 1, 2차 측 모두 능동 소자 및 스너버 회로로 구성 되어있다. 그러나 양방향 동작을 위해 추가된 회로는 플라이백 컨버터의 효율을 감소시키기 때문에 고효율의 양방향 플라이백 컨버터를 설계하기 위해서는 기존의 플라이백 컨버터와는 다른 설계 고려 사항들이 존재한다. 본 논문에서는 양방향 플라이백 컨버터의 각 소자별 손실을 고려하여 정격 부하 시 정방향 동작과 역방향 동작의 최대 효율을 얻을 수 있는 변압기의 자화 인덕턴스의 값을 제시한다. 본 설계 방법은 25 W 급 양방향 플라이백 컨버터 시작품을 이용하여 정격부하에서 전력변환 효율과 설계의 타당성을 실험적으로 검증하였다.

The excess heat that is generated from PV modules can be removed and converted into useful thermal energy. A photovoltaic-thermal(PVT) module is a combination of photovoltaic module with a solar thermal collector, forming one device that receives solar radiation and produces electricity and heat simultaneously. In general, two types of PVT can be classified: glass-covered PVT module, which produces high-temperature heat but has a slightly lower electrical yield, and uncovered PVT module, which produces relatively lower temperature heat but has a somewhat higher electrical performance. In this paper, the experimental performance of two types of the PVT combined module(water type), glazed(glass-covered) and unglazed, was analyzed. The electrical and thermal performance of the PVT combined modules were measured in outdoor conditions, and the results were compared.