Application

We received an inquiry from a customer abroad regarding a monitoring and data logging system for an IoT-enabled photovoltaic (PV) plant monitoring. In addition to controlling electrical values such as current and voltage, the customer also wanted to monitor environmental parameters in a country with significant temperature fluctuations throughout the day.

Proposal

Our proposed system will not only measure and log the generated voltages and current, but also monitor the following parameters:

  • Temperature
  • Humidity
  • Solar Radiation
  • Wind Speed

To achieve this, we recommend utilizing the NI2400 data logger as the central component of the system. This highly durable device, designed based on the Next Instruments geotechnical data loggers series, is perfectly suited for this type of application.

The NI2400 features shielded inputs and a protective coating on all internal electronics, ensuring optimal performance even in outdoor installations where temperature changes and potential moisture build-up may occur. With 2 GB of internal non-volatile data memory and a built-in web server, this data logger offers additional practical features for efficient monitoring and data management.

Requirements

Current measurements

Current transducers type NI-T201DC are installed on the electrical cables and connected to the data logger on a 4..20mA interface to perform this fundamental measurement. Similar to a normal TA, these transducers can measure DC currents until 100A as a galvanic isolated device and are over-temperature protected. They are interfaced to the data logger on 4-20 mA connections.

Voltage measurements

To measure this value safely and reliably, we have suggested the NI20. The NI20 module can measure alternate and/or continue voltage values with high precision. These sensors can also have a current-loop interface but for this case, we have decided to configure outputs as 0..10V, with a direct connection to the data logger inputs.

Temperature and humidity measurement

This outdoor installation requires a high-quality sensor, like the device we have chosen, the NI-EE160 temperature and relative humidity sensor. This instrument has high long-term stability and resistance against pollutants. This sensor is connected to the NI2400 data logger by using a 4-20 mA interface.

Solar radiation

A device called a “solarimeter” usually measures the sun’s radiation. This sensor will continuously transmit the level of solar irradiance to the data logger. The solarimeter on our catalog, the NI-DW6450 is perfectly suited for this application, with a moderate cost. It is based on a silicon cell sensor, which is the best solar radiation measurement technology for the photovoltaic field. The instrument output is a 0-3V voltage level, that we have connected to one of the data logger’s analog inputs. NI2400 data logger will automatically transform and log the voltage values in W/m2.

Wind speed measurement

An anemometer, which is usually used in weather stations, is required to measure the wind speed. The simple, classical wind-cup type is still the more reliable anemometer for this kind of application, like the NI-WSS01. We have connected the anemometer power supply input to the data logger power output and the sensor output to one of the NI2400 analog inputs (the anemometer outputs a voltage level of up to 2.0V). The data logger can make the conversion between voltage and wind speed.

FTP Transfer, Modbus TCP, or Cloud Monitoring

In this type of application, customers usually want to monitor and analyze the data with their remote software or “PV Software Analysis”. The simplest way and first solution to communicate with this type of software is through FTP.

In this way, the NI2400 works properly. It sends data to the server through FTP and then the “PV Software Analysis” elaborates on them. The second way of working is through MODBUS TCP/IP if supported by your Scada software. The third possible solution is the “Cloud Monitoring Service” which is compatible with tablet and smartphone views.

NI2400 Cloud Web Portal is a web service to monitor and control remotely all your field devices. By logging in to the portal, you face a host portal of cloud management services that enable you to monitor and control your equipment in a fast, efficient, and professional way.

Conclusion

This is an instance of IoT-enabled photovoltaic (PV) plant monitoring utilizing the NI2400 Universal Data logger. This monitoring system goes beyond just measuring the produced energy and includes various environmental parameters. By connecting a radio modem to the data logger, customers can remotely monitor the entire photovoltaic energy plant. This outdoor installation allows for accurate measurements of solar radiation and wind speed. Additionally, the usage of IoT Cloud technology enables efficient and effective monitoring of the PV plant, with the option to receive user-defined alarms via email or SMS.