**3. Double-glazed PV module**

In Korea, it is an obligatory requirement that building materials such as windows and doors for a residence should be double glazed in order to ensure adequate heat insulation. Moreover, as the demand for energy efficiency buildings increases, the efficiency of double glazed window systems is improving with respect to heat insulation, as is the efficiency of exterior wall systems of buildings. Therefore, the photovoltaic characteristic of thin-film solar cells was measured in terms of the transmittance of the cell prior to evaluation of the PV module (Figure 1). The results of this measurement showed an average transmittance of 10 % at the range of visible radiation between 390 nm and 750 nm.

Using this thin-film solar cell, a single plate PV module was manufactured to a thickness of 10 mm, and the PV module was then modified as a double glazed module of 27 mm thick, consisting of a 12 mm air space and a 5 mm thick layer of common transparent glass, as shown in Figure 2.

vigorous research on PV with respect to the application of crystalline silicon solar cells. An example of such research includes the evaluation of the power output of PV modules with respect to the ventilation of the rear side of the module. However, research on the transparent thin-film solar cell as a building façade application including windows and

Therefore, the objective of this study is to establish building application data for the replacement of conventional building materials with thin-film solar cells. In this study, an evaluation is carried out on the performance of the thin-film solar cell through long-term monitoring of the power output according to the inclined slope (the incidence angle). This is conducted by using a full-scale mock-up model of the thin-film solar cell applied to a double glazed system. In addition, the aim of the application data of the thin-film solar cell is to analyze the effect of both the inclined slope and the azimuth angle on the power output

In this study, a full-scale mock-up model was constructed in order to evaluate the power output performance of a PV module laminated with a transparent thin-film solar cell. A mock-up model was designed for a PV module that had a range of inclined slopes, and was used to measure the power output according to the slope (incidence angle) and the azimuth angle. The collected experimental data was then compared with the simulated data for a

A commercialized single plate transparent thin-film solar cell with amorphous silicon was used in this study (KANEKA, Japan). This was modified into a double glazed PV module in

Using the full-scale mock-up model, the system output was monitored for 9 months. A computer simulation (TRNSYS, University of Wisconsin, USA) of the PV module was also performed at the same time, and empirical application data was calibrated for the statistical analysis of power performance based on the inclined slope and the azimuth angle. In particular, the annual power output of the PV module was obtained by analyzing the data obtained from the remaining 3 months on the basis of the 30 years' standard weather data in

In Korea, it is an obligatory requirement that building materials such as windows and doors for a residence should be double glazed in order to ensure adequate heat insulation. Moreover, as the demand for energy efficiency buildings increases, the efficiency of double glazed window systems is improving with respect to heat insulation, as is the efficiency of exterior wall systems of buildings. Therefore, the photovoltaic characteristic of thin-film solar cells was measured in terms of the transmittance of the cell prior to evaluation of the PV module (Figure 1). The results of this measurement showed an average transmittance of

Using this thin-film solar cell, a single plate PV module was manufactured to a thickness of 10 mm, and the PV module was then modified as a double glazed module of 27 mm thick, consisting of a 12 mm air space and a 5 mm thick layer of common transparent glass, as

10 % at the range of visible radiation between 390 nm and 750 nm.

performance by comparing this data with the simulation data for PV modules[9].

doors is only in its early stages.

**2. Methodology** 

Korea.

shown in Figure 2.

power performance analysis.

**3. Double-glazed PV module** 

order to install the mock-up model for this study.

Fig. 1. Transmittance of PV module depending on the wavelength

Fig. 2. Preparation for single plate of double-glazed PV module using transparent amorphous silicon (A-Si) thin-film cell.

From the performance evaluation of the heat insulation, the prepared PV module exhibited a 2.64 W/m2-℃ thermal transmittance, as shown in Figure 3. However, it showed an 18 % solar heat gain coefficient (SHGC), which was much lower than that measured for the common double glazed window. WINDOW 6.0 and THERM5.0 (LBNL, USA) were used to analyze the heat insulation of the standard type of double glazed PV module widely used

Power Output Characteristics of Transparent a-Si BiPV Window Module 191

**Item Specification**  Module thickness (mm) 10 Module efficiency (%) 7 Maximum power output (W) 44.0 Maximum voltage (V) 59.6 Maximum electric current (A) 0.74 Open circuit voltage (V) 91.8 Short circuit current (A) 0.972

slope (incidence angle) on the power output, the inclined angles were varied on the mockup by installing both a tilted roof at 30º and a common roof without any slope. The mock-up faced south in order to maintain a compatible solar irradiance with the location of Yongin, Gyeonggi, Korea. Two separated spaces were prepared in order to test the thin-film PV module (Test room A in Figure 5(a)) and the common double glazed window (Test room B in Figure 5(a)) as a reference. The spaces were 2 m long, 3 m wide, and 2.7 m high. The double glazed PV module and the common double-glazed window were installed in each

A mock-up model was also constructed in order to monitor the electric current, voltage, power, temperature, and solar irradiation depending on the inclined angle of the PV module. The double glazed thin-film PV module revealed only a 10 % transmittance (See Figure 1), but this was as sufficient as the common double glazed window for observing the

The total solar irradiance and power output of the PV module, depending on the inclined angle of double glazing, were monitored through the mock-up model for 9 months from November 2006 to August 2007. Data obtained from the mock-up was collected based on minute-averaged data, and the final data of 12,254,312 was statistically analyzed based on 56 variables. Firstly, daily data was rearranged into monthly data. Secondly, minute-based data was averaged and combined into an hourly data. Finally, each group was analyzed in terms of an arithmetic mean, standard deviation, minimum, and maximum value. The empirical data in this study was limited in DC output, which was obtained from the load using resistance without an inverter. Thus, it is assumed that there may be a number of differences between the data measured in this study and the empirical data controlled by maximum

Figure 6 shows the hourly data, which was yearly-averaged, of the intensity of solar irradiance and DC output depending on the inclined angle of the double glazed PV module. Based on the data measured at noon, the inclined slope of 30 º (SLOPE \_30) revealed an insolation of 528.4 W/m2, which shows a greater solar irradiation than that for the slopes of 0 º (SLOPE\_0, 459.6 W/m2) and 90 º (SLOPE\_90, 385.0 W/m2), as shown in Figure 6(a). Consequently, the average power output at noon also exhibited 19.9 W for SLOPE\_30, which was higher than that shown

in the data for SLOPE\_0 (15.76 W) and SLOPE\_90 (8.6 W) (See Figure 6(b)).

Table 1. Specification of the tested thin-film PV module

**5. Power performance of PV module** 

power peak tracking (MPPT) using an inverter.

outside.

separated test room at different inclined angles (0 º, 30 º, and 90 º).

**5.1 PV module performance measured in mock-up model** 

for the heat insulation of building windows and doors. This analysis allowed for the evaluation of heat transfer under a two dimensional steady state for the user defined fitting system at a given circumstance.

Fig. 3. Optical and thermal characteristics of double-glazed PV module (T\_sol is the solar transmittance, T\_vis is the transmittance of visible radiation, SHGC is the solar heat gain coefficient, and U\_value is the thermal transmittance of PV module).module

Figure 4 shows a plane figure of a 10 mm thick and 980 × 950 mm single plate PV module, and a PV module consists of 108 cells in series. The electrical characteristics of the prepared PV module are listed in Table 1.

Fig. 4. Plane figure of a single plate PV module.
