High-Fidelity Multisite Distributed Solar-Farm Monitoring System

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"For this project, LabVIEW was used to program the WSN nodes, the WSN gateway, the CompactRIO device, the server, the web page, the kiosk, and the offline analysis software. It is truly revolutionary that a single programming language can be used for every part of this project."

- Chris Fronda, Certified LabVIEW Architect, VI Design Group, Inc.

The Challenge:
Designing a high-fidelity solar-farm monitoring system distributed across multiple sites around The University of Texas at San Antonio (UTSA) campus to measure inverter (AC), combiner (DC), irradiance, thermocouple, and weather data at high rates with 100 percent reliability.

The Solution:
Using NI CompactRIO, an NI wireless gateway, and NI wireless sensor network (WSN) nodes to create an industry-leading, distributed high-fidelity monitoring system with central server data collection and processing as well as a web page and kiosk display for external user interaction.

Chris Fronda, Certified LabVIEW Architect - VI Design Group, Inc.

VI Design Group, a certified National Instruments Alliance Partner, is a professional system integrator of NI technology. The VI Design Group team consists of Certified LabVIEW Architects committed to the highest quality of system development. VI Design Group has experience developing turnkey products such as remote data loggers, control systems, and automated test systems. It has delivered medical, renewable energy, oil and gas, and other industrial products.

The development of a custom solar-farm monitoring system based on NI technology was necessary because of the distributed nature of the system and the high-fidelity rates needed. There was not a commercial off-the-shelf (COTS) solution that met the requirements for this project. Furthermore, UTSA wanted the ability to integrate control logic into the same system in the future for battery storage control and sun tracking. The ability to integrate control into the same monitoring system was what differentiated the NI platform from other suppliers’ technology.

Figure 1. Three sites featured equipment, including a 313 kW system, that was deployed for this effort.

This project was part of the NI Green Engineering Grant. The system received the award because of its innovative design and the teaching capabilities it provided. It was also funded by the Department of Energy under the American Recovery and Reinvestment Act.

Gerardo Trevino, research assistant at UTSA, gave the following presentation as part of this award:

VI Design Group was selected as the system integrator for this project because of its expertise with monitoring systems. It has extensive experience in working with CompactRIO to perform remote monitoring. It also has experience with reliable data transfer to a central server for storage and postprocessing. VI Design Group developed and deployed this system in multiple phases for multiple physical locations at UTSA.

System Design Overview

At a high level, the system consists of three major pieces, which are shown in figures 2 and 3. The red portion is the data acquisition part of the system, which is replicated across multiple sites. It consists of a CompactRIO device collecting data either wirelessly from the WSN gateway or physically through directly connected sensors. The CompactRIO device collects that data and then transmits that data to the central server for storage, postprocessing, and web hosting. The server, which is the blue portion, is an active server that pulls data from the CompactRIO systems and sounds an alarm if any data is corrupt or if communication is lost. It also stores that data in a database and publishes a web page for external viewing.

Finally, the green portion highlights all of the user interfaces for system interaction. The web page is available to everyone at any time. The kiosk displays are physically located on-site at UTSA for student interaction, and the host PC consists of private access to the raw data for the professors to download and manipulate.

Figure 2. High-Level Points for the Three Parts of the System

Figure 3. Detailed Overview of the System Components for Each of the Three Parts

NI hardware and NI LabVIEW system design software made the design of this system fast and easy. NI helped by developing all of the low-level design work and abstracting that to a high-level API. NI had already completed the following items, so VI Design Group did not have to develop them:

  1. ZigBee wireless protocol design
  2. Embedded OS design/microcontroller implementation
  3. Printed circuit board layout and 24-bit delta-sigma A/D incorporation
  4. Heat-transfer analysis and passive cooling system design
  5. TCP/IP or user datagram protocol network protocol design
  6. Secure sockets layer encryption and security features
  7. Complex memory management compared to C/C++
  8. VHSIC hardware description language FPGA programming
  9. Microsoft Silverlight web control design
  10. Web server configuration with web services

Essentially, all of the low-level work is done, leaving just the high-level work. To design and implement this system, the user must understand the high-level configuration of NI equipment and the singular programming language LabVIEW. For this project, LabVIEW was used to program the WSN nodes, the WSN gateway, the CompactRIO device, the server, the web page, the kiosk, and the offline analysis software. It is truly revolutionary that a single programming language can be used for every part of this project. With the extensive training courses offered by NI, anyone can become an expert at using NI technology to design this complex monitoring system.

System Deployment and Next Steps

The following images show system deployment:

Figure 4. Inverter Installation and AC Monitoring Equipment Installation

Figure 5. CompactRIO Data Logger Deployed at Each Site

Figure 6. NI WSN Node Collecting Irradiance and Thermocouple Data

Some of the analysis was implemented using NI DIAdem software for postprocessing data analysis. DIAdem is helping professors at UTSA execute queries across all of the data being collected and then analyze and present that data. This analysis is already being used to perform solar forecasting comparisons. The following figures show the actual photovoltaic (PV) output compared with the forecasted PV output.

Figure 7. Captured Raw Data Graphed in DIAdem Comparing Actual and Forecasted Power

Figure 8. Smoothed Data Capture Demonstrating How Close Actual Was to Forecasted Power

This system provided UTSA with a reliable, high-fidelity, distributed solar-farm monitoring system. It met all of the objectives for the project. Now the open platform and control logic capabilities of CompactRIO are being explored by UTSA to extend the functionality of the system beyond that of any COTS system, and it is helping UTSA perform cutting-edge research that can benefit the solar energy industry.

For more information, please watch the following NIWeek presentation:


A National Instruments Alliance Partner is a business entity independent from National Instruments and has no agency, partnership, or joint-venture relationship with National Instruments.

Author Information:
Chris Fronda, Certified LabVIEW Architect
VI Design Group, Inc.

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