Building an Embedded Renewable Energy Performance Monitor for Rural India

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"There is an old saying: If you give a man a fish, you feed him for a day, but if you teach a man to fish, you feed him for a lifetime. That’s what Planet NI embodies for us. What Planet NI did for us, we want to do for the country—we want to empower people in rural areas through renewable technology tools. Planet NI program team members helped us complete a project with a significant social impact in rural India by making their products accessible and helping us ultimately be successful."

- Hari DK, FluxGen Engineering Technologies

The Challenge:
Developing a compact, accurate, and embedded performance analyzer and logger for a solar PV power system that is intuitive to use, takes advantage of plug-and-play technology, and is fully network enabled.

The Solution:
Working with the Planet NI program by using the NI sbRIO-9641 embedded control and acquisition device, along with NI LabVIEW system design software, to develop the application and deploying it to guarantee performance in a scientific way for the customer.

Author(s):
Hari DK - FluxGen Engineering Technologies

Renewable energy is derived from sources that are naturally replenished, such as sunlight, wind, tides, and geothermal heat. With falling silicon prices, solar PV systems that generate electricity from sunlight are becoming economically viable. In urban areas, solar PV provides clean energy for homes, institutions, and industries. In rural areas, it can bring energy to places where it is prohibitively expensive to extend the existing electricity grid.

Solar PV systems can range in size from small, rooftop-mounted subkilowatt plants to large solar farms that generate many megawatts of commercial electricity. Regardless of size, all solar PV installations contain some common components, such as solar panels for harvesting sunlight and converting it to electricity, batteries for storing energy, and inverters that convert the DC solar energy into AC form. The performance of the whole system depends on the performance of the individual components and the system-level interaction.

Once a system is installed, there is often no indication of whether it is performing according to the system design specifications. For small household installations, the only indication of optimum operation might be a reduced electricity bill. High-end inverters sometimes provide some data on power levels in the system, but this is nonstandard, and an independent study may need to be conducted for some customers. To bridge this gap, we developed a solar PV plant performance meter using NI technology to accurately measure and log the performance of a system.

Our System Based on NI Technology

We used the NI sbRIO-9641, an advanced embedded data acquisition and control platform that is programmable using LabVIEW software. The device contains a 1M gate Xilinx FPGA, a real-time OS (RTOS), and Ethernet connectivity, and it provides 128 MB of secondary storage, which was ample for our purposes.

Our application, the renewable energy performance monitor (RPM), works as follows:

  1. Take the RPM to the solar PV plant that needs to be assessed
  2. Wire the device to various parts of the plant (for example, at the battery terminals)
  3. Give the device Ethernet access, and power it up

The device then automatically collects various signals from the system. It runs and logs the data in a format suitable for analysis in any spreadsheet tool. There is no need for an external PC for it to run. When the network connection is available, the device also seamlessly transfers data to a configurable server that can trigger a web update with graphs that provide information on the day’s energy yield.

Since the RPM is built on sophisticated hardware and the LabVIEW platform from NI, it is highly extensible. The system can easily be configured to operate on a variety of system topologies, from small residential setups to huge power plants. The abundance of I/O on the device ensures that it scales to even large plants. The FPGA device on the RPM provides high-resolution acquisition of the necessary signals.

The RTOS, with its rigorous hardware timing and parallel processing, ensures that data is not lost or misrepresented during operation. It also helps us apply sensitive multipoint calibration on the raw data. The ample secondary storage means that the device can run unattended for days, weeks, or even months. Because the RPM is fully network-enabled, it automatically performs web updates whenever possible.

After we developed the RPM, we deployed it at one of our customer’s installations. This particular customer is a highly experienced engineer and asked us many tough technical questions about the performance and technology of the solar PV systems. Using the RPM, we were able to convince him of the system’s superior performance using hard data. We also had the luxury of monitoring his system’s performance in real time from our lab over the Internet.

The Future of the RPM System

We foresee the RPM system being a tool that engineers can carry in the field for troubleshooting or installing plants of almost any size. We emphasize that the device is not limited to solar PV system use. For example, with little modification, it can be used for wind or hybrid PV-wind systems. An interesting extension of the tool for rural areas with no network connectivity would be to make it transmit summarized statistics of operation via text messages over the regular cellphone network. While we have not implemented this, it is certainly possible with little overhead. In short, NI technology helped us to develop a useful tool for renewable-energy workers in the lab and in the field.

Editor Contact
Anita Shekhar
National Instruments
Email: planetni@ni.com

Author Information:
Hari DK
FluxGen Engineering Technologies
FluxGen Engineering Technologies, #1064, 18th Main, 2nd Stage BTM Layout
Bangalore
India
Tel: +91 9481426107
hari@fluxgentech.com

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