Using LabVIEW to Develop Energy-Optimized Photovoltaic Applications
"LabVIEW, a graphical programming environment from National Instruments, has proved to be a versatile environment for PV system design, data acquisition, analysis, and presentation in PV applications." - Dr. Daniel Dunea , Valahia University of Târgovişte, Environmental Engineering Department
The Challenge: Evaluating the performance of photovoltaic (PV) grids using methods that differ in cost, accuracy, and complexity and require technical expertise.
The Solution: Developing the EnergOPTIMIZER instrumentation system using NI LabVIEW for optimal design and operation of PV installations. EnergOPTIMIZER Front Panel – Selection of the Required VI
Author(s): Dr. Daniel Dunea - Valahia University of Târgovişte, Environmental Engineering Department Dr. Adrian Dunea - Valahia University of Târgovişte PV technology is a method for generating electric power using solar cells to convert energy from the sun into electricity. PV technology is a promising alternative of renewable energy, and is growing in popularity. A PV system’s performance and efficiency depends on operation, maintenance, and climatic factors. Solar radiation conversion efficiency, which describes the ratio between electrical energy that can be output from the system to the energy delivered to the system, diminishes to a certain degree due to site conditions and PV system characteristics. We selected LabVIEW graphical design system software as the foundation for the system because of its versatility in design, data acquisition, analysis, and presentation for PV applications. We can use LabVIEW VIs to mimic instrument front panels and installation components used in PV technology. LabVIEW is also a powerful programming tool for developing automated instrumentation systems that integrates advanced data analysis and presentation capabilities, which was a great fit for the EnergOPTIMIZER application. LabVIEW software assisted in the following tasks: Designing a PV system and its performance optimization according to user and site requirements Simulating PV system functions for optimal scheme selection Monitoring the PV operation using data acquisition from specific sensors, database population, and PV performances analysis and forecasting
System Architecture The EnergOPTIMIZER structures are comprised of 12 associated VIs grouped into seven modules. Each VI is highlighted in the starting window in the following order: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.
PV load dimensioning PV array orientation Battery sizing and selection Hybrid PV diesel battery power systems sizing and analysis Structural dimensioning of the electrical installation associated to the PV system Cost assessment for the realization and operation of the designed PV installation PV performances forecasting PV system functioning simulation Data acquisition VI for monitoring the PV system and the site-specific environmental conditions PV system operation control PDA VI – pocket PC for on-site PV data collection and statistical analysis Real-time monitoring server application Life-cycle cost (LCC) analysis of the PV system
EnergOPTIMIZER Application The PV array is the most important and most expensive component of the system. Proper sizing influences the PV system’s performances and the investment amortization . The program employs the user-selected PV panel characteristics and data provided by the previous VIs as inputs. The EnergOPTIMIZER provides the main PV electrical characteristics including short-circuit current, maximum-power current, open-circuit voltage, and maximum-power voltage, as well as physical characteristics, the PV panel number, and PV panel interconnections. The dedicated VI assists the user in selecting the PV panel type from 200 available types based on measurements such as previously established load, battery type, and system voltage. Each electrical scheme of PV installation displays automatically based on the assisted configuration, showing the required PV panels and batteries, the connection schemes, and the bypass and blocking diodes. The program can establish the limits for the battery voltage regulator that assists in the connection process. In addition, the application provides expert support if a diesel back-up generator is required for a stand-alone PV application, which can occur in case of insufficient on-site solar energy. During PV system design and array sizing, users have to estimate the module operating temperature and separate it from tabulated environmental parameters, such as ambient temperature, wind speed, and irradiance. The thermal environment that dictates module operating temperature is complex and influenced by wind direction and module design, orientation, and mounting structure. Monitoring the PV system and site-specific environmental conditions is critical to assess PV performance. In addition, real-time information and data processing automation are necessary for fast response times in the PV operation surveillance process. As a result, we developed a data acquisition system to measure the electrical parameters of the PV installation and environmental conditions. This segment monitors, logs, and broadcasts real-time data from multiple PV systems to the measurement server. LabVIEW analyzes the collected data using methods such as the autoregressive integrated moving average (ARIMA).
1/8
www.ni.com
We also developed PDA VIs using the LabVIEW Mobile Module to collect data and provide online statistical analysis. The application gathers, stores, customizes, and analyzes data that is transferred from the data logger to the Pocket PC via an RS232 serial connection. Another key feature is the life-cycle cost evaluation that allows comparison between various types of solar generators, providing guidelines for improving design and infrastructure of the PV installations. Conclusions For less-experienced PV operators, the LabVIEW application for the EnergOPTIMIZER offers a user-friendly, interactive PV system design, providing complex information concerning the PV components and subsystems, the electrical scheme, and the hybrid system. The EnergOPTIMIZER. Author Information: Dr. Daniel Dunea Valahia University of Târgovişte, Environmental Engineering Department Bd. Unirii no. 18-24, Târgovişte, Dâmboviţa Romania Tel: +40 245 206 108
[email protected]
EnergOPTIMIZER Front Panel – Selection of the Required VI
2/8
www.ni.com
PV Load Dimensioning
3/8
www.ni.com
Structural Dimensioning of the Electrical Installation Associated to the PV System
4/8
www.ni.com
5/8
www.ni.com
DAQ VI – Monitoring PV System and the Site-specific Environmental Conditions Using XPV Data Logger
6/8
www.ni.com
7/8
www.ni.com
PDA VI – Pocket PC On-site PV Data Collection and Statistical Analysis
Life-cycle Cost Analysis of the PV System
Legal This case study (this "case study") was developed by a National Instruments ("NI") customer. THIS CASE STUDY IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND AND SUBJECT TO CERTAIN RESTRICTIONS AS MORE SPECIFICALLY SET FORTH IN NI.COM'S TERMS OF USE ( http://ni.com/legal/termsofuse/unitedstates/us/).
8/8
www.ni.com
