Purdue University Bifacial Module Calculator (PUB)

Transcription

1 Purdue University Bifacial Module Calculator (PUB) Date: 02/18/2018 Purdue University Bifacial Module Calculator (PUB) is a module-level simulator that can accurately model and optimize the performance of a bifacial module at any arbitrary location. PUB can also simulate bifacial modules with different installation parameters (e.g., tilt and azimuth angles, module height) installed in regions with different ground albedo coefficients. By PUB, a user can compare the location-specific energy yield of a bifacial module to that of its monofacial counterpart to evaluate the financial viability of the bifacial technology. The results can also be used to facilitate the optimization of bifacial solar farms. This tool is developed by Binglin Zhao, Xingshu Sun, Mohammad Ryyan Khan, and Muhammad A. Alam at Purdue University. The authors acknowledge the helpful discussion with Chris Deline from the National Renewable Energy Laboratories, and Joshua Stein and Clifford Hansen from the Sandia National Laboratories. The global meteorological database used in PUB can be found in: Purdue University Meteorological Tool (PUMET) [1]:

2 1. INTRODUCTION A bifacial solar module collects light from both the front and the rear sides to generate electrical power. Therefore, it can produce more energy than a monofacial module. Existing technologies, e.g., Si heterojunction solar cells, can also be easily reconfigured into bifacial mode without extensive modification in the manufacturing processes. The dual-glass structure of a bifacial module may also improve the long-term reliability. All these advantages make bifacial modules a very compelling alternative to monofacial modules for both stand-alone and farm-level applications. The energy yield from a bifacial module, however, depends strongly on the local meteorological environment (e.g., diffuse versus direct light) and the installation parameters (e.g., tilt and azimuth angles, elevation above the ground). Hence, a bifacial module must be simulated locally to assess this geographic- and installation-specific performance and to optimize the installation to maximize energy yield. Existing software packages, such as PVlib [2] and PVSyst [3], either requires conversance with programming languages (Matlab or Python) or a commercial license. A rigorous yet easy-to-use simulation tool that can model and optimize the performance of solar modules will benefit the PV community. In this regard, we have developed an online simulation tool, named Purdue University Bifacial Module Calculator (PUB) to assess the potential performance of a bifacial module at a given location. PUB utilizes a view-factor based approach to calculate the incident irradiance on both the front and rear sides analytically [4]. Our tool explicitly accounts for two types of self-shading effect of albedo light: 1) direct blocking of direct/circumsolar light, and 2) sky masking of diffuse light. An opto-electro-thermal simulation framework converts the total incident irradiance into electricity. The detailed calculation procedures are discussed in [4] [6]. In the following session, we will introduce the input and output parameters in PUB, and demonstrate the use of the tool by a simple example (i.e., optimize the tilt angle of a south-facing bifacial module installed in West Lafayette, IN, USA). 2. LAUNCHING PUB PUB is deployed on nanohub.org, which provides web-enabled simulation tools. A user can register an account to log in to the website. After logging in, the user can launch PUB and then enter the input parameters in the interface as shown in Figs. 1 and 2. After running the simulation, PUB can visualize the output results in a set of plots, which also allows direct download the data for future analysis.

3 3. INPUT PARAMETERS Figure 1. Specify installation parameters needed for simulation. a) Specify Simulation Parameters: Latitude: Enter the latitude of the location. The value entered should be positive for the northern hemisphere, and negative for the southern hemisphere. For the example in Fig. 1, the latitude of West Lafayette is entered. A web search can quickly locate the latitude of any location in the world. Longitude: Enter the longitude of the location. The value entered should be positive and negative for East and West of the Prime Meridian, respectively. For the example in Fig. 1, the longitude of West Lafayette is entered. A web search can quickly locate the longitude of any location in the world. Module Height: Enter height (from top to bottom) of the solar module in the unit of meter. The module in 1 meter high in the example in Fig. 1. Module height for a specific technology can be found in the datasheet provided by the manufacturer. Azimuth Angle: Enter the azimuth angle of the solar module in the unit of degree. (southfacing is 180 degree). In the example, the module is south-facing. Therefore, we have entered 180 o. Tilt Angle: Enter the tilt angle of the solar module in the unit of degree. The module in the example is tilted 45 degrees. Reference [4] provides a set of empirical equations to optimize tilt angles analytically.

4 Front-Side Efficiency: Enter the front-side efficiency of the solar module in percentage. The front-side efficiency in the example is 18%. The information can be found in the datasheet. Elevation: Enter the elevation above the ground of the solar module in the unit of meter. The elevation in the example is 0.5 meter. Elevating module above the ground can reduce self-shading. Bifaciality: Enter the bifaciality of the solar module in percentage. The bifaciality in the example is 90%. Bifaciality can be found in the datasheet as well. Ground Albedo: Enter the ground albedo coefficient in percentage. A value of 25% (typical for vegetation and concrete) is used in the example. A set of albedo coefficients for different groundcovers can be found in [7]. Electro- Thermal Model (Faiman Model) [8]: YES: Simulate temperature-correlated efficiency. NO: Module temperature will be fixed at 300K. Our example in Fig. 1 uses the electro-thermal model. Temperature Coefficient: Enter the temperature coefficient of the solar module in %/K. The temperature coefficient in the example is %/K. Module datasheet contains this information. U0: This parameter is to calculate the constant heat transfer component in the Faiman Model. The parameter is set to be 22.7 W/m 2 /K in the example. U1: This parameter is to calculate the convective heat transfer component in the Faiman Model. The parameter is set to be 6.84 W.s/m 3 /K in the example. Compare to a Monofacial Module: Click YES to display comparison to a monofacial module. b) Select Simulation Mode: Simulation Mode: Choose to simulate monthly output or to sweep installation parameters. For simulating monthly output, the user can specify the monthly time window to view the energy output. For sweeping installation parameters, the output result will be the annual energy output as a function of the chosen parameter. For the example in Fig. 2, we will sweep tilt angle.

5 Start Month (only for monthly simulation): Enter the start month from 1 to 12 (Jan. to Dec.). End Month (only for monthly simulation): Enter the end month from 1 to 12 (Jan. to Dec.). The end month must be larger than the start month. Specify Sweeping Parameter: The user can choose from longitude, latitude, elevation, tilt angle, azimuth angle, albedo coefficient, and bifaciality. We will sweep tilt angle in the example. Minimum Value: Enter the minimum value of the chosen parameter. In the example, we start with zero degrees. Maximum Value: Enter the maximum value of the chosen parameter. In the example, we sweep the tilt angle up to 90 degrees. Number of Data Points: Enter number of data points in the simulation. In the example, we simulation 10 data points between 0 to 90 degrees tilt angle. Note that increasing the number of data points requires longer simulation time. 4. OUTPUT RESULTS Figure 2. The interface to choose simulation mode. Energy Yield of the Bifacial Module: This plot shows the energy output of a bifacial module, see Fig. 3. These results include energy yield from diffuse light, direct light, albedo light, and their total.

6 Figure 3. Energy yield of the simulated bifacial module. Bifacial Gian: This is the bifacial gain of a bifacial module relative to an identically configured monofacial module, see Fig. 4. Figure 4. Bifacial gain of the simulated bifacial module. Total Absorbed Insolation: Figure 5 shows the total insolation absorbed by a solar module. The total insolation absorbed by the bifacial and monofacial modules is both included in this plot.

7 Figure 5. The total absorbed insolation of the simulated bifacial and monofacial modules. Energy Yield of the Monofacial Module: Figure 6 shows the energy output of a monofacial module. These results include energy yield from diffuse light, direct light, albedo light, and their total. Figure 6. Energy yield of the simulated monofacial module. 5. CONCLUSION The simulation results produced by PUB can be valuable to optimize bifacial modules and evaluate their optimum performance. For instance, we have found that a ~40 o tilted bifacial module installed in West Lafayette, IN, USA, gives the maximum annual energy yield of ~310 kw.h/m 2, as shown in Fig. 3. This value is higher than a monofacial module with an optimal tilt angle of ~30 o and a maximum energy yield of ~275 kw.h/m 2, see Fig. 6. Moreover, the simulation results in Fig. 3 also indicate that the electricity (~180 kw.h/m 2 ) from direct light is almost twice higher than that (~100 kw.h/m 2 ) from diffuse light, whereas albedo light only provides limited energy (~30 kw.h/m 2 ) due to the low albedo coefficient (25% in Fig. 1).

8 6. ACKNOWLEDGEMENT This work was supported by the National Science Foundation through the NCN-NEEDS Program, Contract EEC, and the US-India Partnership to Advance Clean Energy-Research (PACE-R) for the Solar Energy Research Institute for India and the United States (SERIIUS), U.S. Department of Energy under Contract No. DE-AC36-08GO28308 with the National Renewable Energy Laboratory. 7. REFERENCES [1] B. Zhao, X. Sun, M. A. Alam, and M. R. Khan, Purdue University Meteorological Tool. [Online]. Available: [2] PV_LIB Toolbox. [Online]. Available: [3] PVSYST user s manual. [Online]. Available: [4] X. Sun, M. R. Khan, C. Deline, and M. A. Alam, Optimization and performance of bifacial solar modules: A global perspective, Appl. Energy, vol. 212, pp , Feb [5] M. R. Khan, A. Hanna, X. Sun, and M. A. Alam, Vertical bifacial solar farms: Physics, design, and global optimization, Appl. Energy, vol. 206, pp , Nov [6] B. Zhao, X. Sun, M. R. Khan, and M. A. Alam, Online Simulation Tools for Global Photovoltaic Performance: Purdue University Meteorological Tool (PUMET) and Bifacial Module Calculator (PUB), in the 7th World Conference on Photovoltaic Energy Conversion, [7] U. Feister and R. Grewe, Spectral albedo measurements in the UV and visible region over different types of surfaces, Photochem. Photobiol., vol. 62, no. 4, pp , Oct [8] D. Faiman, Assessing the outdoor operating temperature of photovoltaic modules, Prog. Photovoltaics Res. Appl., vol. 16, no. 4, pp , Jun