Selecting DAS Equipment on Utility Scale PV Projects

Data acquisition systems (DAS) are often employed on small utility scale solar projects to gather information about the performance and conditions of a site. Various sensors, meters, and equipment collect the data that must then be evaluated and visualized within a database. Operators then assess this data to ensure that the solar power plants are operating optimally. 

In the HeatSpring Megawatt Design course, instructor Randy Batchelor explains why selecting and installing appropriate DAS equipment is critical to the success of your small utility scale project. DAS gives system owners and operators comprehensive data and visibility into how the equipment and full system are working and alerts them if there are any problems. 

In residential solar systems, installers typically use the built-in monitoring functions provided by the inverter manufacturer to give the homeowner and installation company visibility into the operation of the system. As companies begin to scale into commercial and small utility scale projects, dedicated DAS are required due to the increased complexity of the systems. This includes third party verified metering, weather data, and more.

When choosing a DAS vendor, there are many things to consider. At the top of the list is good service and fast response time. As their client, you will often need quotes, equipment specifications, and answers to technical questions. Being able to get timely responses on technical concerns is critical to move forward in a project. 

Another critical factor when evaluating DAS vendors is the documentation and support provided. Great DAS companies provide detailed design documents, complete single-lines, and comprehensive, clear installation manuals with good pictures and diagrams.  

DAS vendors must also be able to support design flexibility, accommodating any topology or complexity of system. Megawatt scale solar is not “one size fits all.” Expect to have custom designed DAS solutions on every project. That also means DAS vendors should offer a good selection of high quality components to fit the needs of a particular system. Components include sensors, current transformers (CTs), pyranometers and more. It is also critical that the DAS be compatible with inverters and any other electronics on site. 

The DAS interface should allow for good reporting with analytics and alarms that meet the needs of the operations and maintenance and asset management teams. 

It is important to remember that you are investing a lot in a DAS vendor. Be sure to do your homework when evaluating options. Ask for references. Look for companies who have been around for a while and have proven themselves in the marketplace. While it is possible to switch DAS vendors once a system is established, it is very challenging. It is best to take the time to select the best fit prior to moving forward. 

Another area to consider is connectivity as DAS must be able to export the information collected onsite. There are essentially two primary methods to connect to the internet. The first method is the local area network (LAN), connecting via an existing network switch at the site host facility. This typically adds additional complexity to a project as it requires coordination with the local IT team. The second method is through cellular which requires buying a cell modem and paying a monthly fee for cell service. There are a few additional connection options, like microwave and phone line, but those tend to be rare. 

Weather station configurations have many options and will ultimately depend on the needs and requirements of the system owner. Standard configurations include ambient temperature sensors, module temperature sensors, a pyranometer, and wind speed and direction sensors. Pyranometers are of particular importance when it comes to capacity and performance testing as well as production guarantees.

As the scale increases on solar power plants, utilities will likely require SCADA systems. SCADA stands for Supervisory Control and Data Acquisition. The main difference between DAS and SCADA is that SCADA allows for the utility and/or operators to send commands back to the solar power plant, such as curtailing or shutting down the plant remotely. It is recommended to utilize a SCADA integration specialist as these systems are quite complex and typically must meet the North American Electric Reliability Corporation (NERC) security requirements. 

To learn more about equipment selection, software tools to help the design process, National Electrical Code application and other important subjects for megawatt-scale PV systems, join Randy Bachelor and Ryan Mayfield in their comprehensive Megawatt Design course.