Developing a Renewable Energy Laboratory Using NI ELVIS, NI LabVIEW, and NI myDAQ

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"The RELab and miniRELab systems offer students extremely useful tools to learn about renewable energy sources. We achieved a compact solution using the NI ELVIS platform, which we can use in other laboratories by switching the prototyping board to greatly decrease lab costs. NI myDAQ gave us the small size and low cost we needed to create a portable version of RELab."

- Petru Adrian Cotfas, Lecturer, Transylvania University of Brasov, Romania

The Challenge:
Developing a system for students to study photovoltaic, wind, and solar thermal energies, along with a small, portable version of the system.

The Solution:
Using NI ELVIS and a modular add-on board with an NI LabVIEW driver to create a system for studying renewable energies with an NI myDAQ device for the portable version.

Author(s):
Petru Adrian Cotfas, Lecturer - Transylvania University of Brasov, Romania
Daniel T. Cotfas, Lecturer - Transylvania University of Brasov, Romania

Our society is based on energy, and our energy needs continue to grow, leading us to search for new energy sources. Renewable energy sources are a major part of the solution for humankind’s energy demand. Qualified engineers are key to installing and maintaining renewable energy sources, so we aim to provide our students with high-quality theoretical material as well as practical training with suitable hardware.

We developed the Renewable Energy Laboratory (RELab) to train engineers in renewable energy fields. RELab is an add-on board for the NI Educational Laboratory Virtual Instrumentation Suite II (NI ELVIS II) combined with a LabVIEW project. With the system, students can characterize and find all parameters of a solar cell, wind turbine, and thermal solar collector.

RELab Hardware

The RELab add-on board is modular for easy adaptability to a photovoltaic, wind, or solar thermal lab. Students also can use the modules independently with the NI ELVIS II prototyping board. The three portions dedicated to three renewable energy sources include SolarLab, WindLab, and ThermalLab.

RELab takes advantage of the VIs built into the NI ELVIS platform, resulting in a compact system. The board provides ±15 V and +5 V power supplies for the following circuits:

  • A variable power supply for prepolarizing the I-V characteristic measurement circuit
  • Analog output to control the light source level and the heater temperature
  • Analog input channels for measuring the signals from sensors
  • Digital channels to control the system
  • An impedance analyzer for the spectral impedance spectroscopy of the solar cell

We developed the entire circuit design of the RELab and miniRELab systems using NI Multisim SPICE simulation software and the NI Ultiboard design environment, which offer an easy–to-learn and easy-to-use environment for circuit design— from schematic design and simulation to designing a printed circuit board for manufacturing.

RELab Software

We developed the RELab software in LabVIEW, basing the structure of the software on the LabVIEW driver project. With LabVIEW, we achieved a rapid development time. Using NI-DAQmx driver and measurement services software and the Express VIs, we found the data acquisition and control easy to use. Another strong benefit of LabVIEW is the presentation of results. Using the LabVIEW controls and indicators, we easily built user-friendly interfaces.

Figure 1 shows the developed LabVIEW project for the RELab system. The user can start the laboratories or examples from the RELab labs launcher (see Figure 2).

The RELab labs launcher contains a tab with three pages: SolarLab for the photovoltaic study, WindLab for the wind turbine study, and ThermalLab for the solar thermal collector study. With the VIs from the project, users can implement their own methods to characterize the three renewable energy sources.

SolarLab

Students use SolarLab to characterize and find all parameters of a solar cell. Figure 3 shows RELab in a SolarLab configuration. The system is composed of:

  • An NI ELVIS platform and a RELab board with a light control module
  • A heat control module
  • An I-V curve measurement module
  • A stepper control module
  • Solar cell sensor support and furnace module
  • A light source
  • A stepper motor

The student can illuminate the solar cell from just a few watts per square meters, up to 1,000 watts/m2. The temperature can increase from room temperature to 70 °C. The solar cell can rotate from 0 deg to 90 deg using the stepper motor.

Figure 4 presents the first lab interfaces. The application contains a tab with three pages. A theory page offers students theoretical information about the lab work performed with this application. With an I-V measuring page, students can set up the conditions to measure the I-V characteristics of the solar cell and present the results. Students use cursors and indicators to manually determine the solar cell parameters. The power and I-V characteristics page shows the automatically determined solar cell parameters. Students can compare the manually determined results with the automatically determined results. They also can use this application offline by saving the measured data. Students generate a lab report by pressing the report button from the third page.

The system measures solar cell impedance by removing the I-V curve measurement module and connecting the solar cell terminal to the two terminals of the impedance analyzer. Figure 5 presents the panel of the impedance spectroscopy application, used for measuring the solar cell impedance spectroscopy. This application is based on the NI ELVIS impedance analyzer instrument.

The lab experiments often use a simulation method. Students can use the simulation software to learn the principles of the system. We use Multisim software to simulate the circuit to study the solar cell. Figure 6 shows the circuit for simulating the measurement of the solar cell I-V characteristic. With the AC analysis in Multisim, students can study the impedance spectroscopy of the solar cell (see Figure 7).

WindLab

With the WindLab part of the system, students can determine the influence of wind speed, number of turbine blades, shape of the blades, and attack angle of the blades on the wind turbine efficiency.

Figure 8 presents the RELab board in the WindLab configuration. We replaced the I-V curve measurement module with the turbine parameters measurement module. WindLab includes a laptop running the LabVIEW application, the NI ELVIS platform, and the RELab board, which includes the turbine parameters measurement module, the wind turbine, and a ventilator. With the turbine parameters measurement module, students can apply a variable load to the wind turbine and the measurement of the voltage and current generated by the wind turbine. The wind turbine features a three-phase generator and a redressing bridge. The ventilator generates wind for spinning the wind turbine.

The application interface for studying the wind turbine function of the wind speed is presented in Figure 9. The application allows the measuring of the voltage, current and power generated by the wind turbine depending on the wind speed. Using the LabVIEW Control Design and Simulation Module , students can create different simulations for a wind turbine. There are several wind turbine simulation LabVIEW examples using this toolkit.

ThermalLab

With the ThermalLab portion of the system, students can achieve the efficiency of a solar thermal collector function of the irradiance level, the incidence angle of irradiance, and the debit of the fluid through a collector.

Figure 10 shows the RELab board in the ThermalLab configuration. We replaced the I-V curve measurement module with the solar collector’s parameters measurement module. WindLab includes a laptop running the LabVIEW application; the NI ELVIS platform; the RELab board with a solar collector’s parameters measurement module and a solar collector; and a thermostatic box with a water pump and a flowmeter. With the solar collector’s parameters measurement module, students can measure the fluid temperature at the solar thermal collector’s input and output. The solar collector absorbs heat from the irradiance emitted by the light source and heats the passing fluid.

The application interface for studying the solar thermal collector function of the fluid flow is shown in Figure 11. With the application, students can monitor the fluid temperature at the collector’s input and output as well as calculate the efficiency of the collector.

miniRELab

To achieve a student-oriented education, we created a portable version of RELab based on the NI myDAQ low-cost system. We consider NI myDAQ similar to an NI ELVIS system with reduced functionality. The dedicated device makes it possible for students to perform hands-on lab work anytime, anywhere.

The basic characteristics of the NI myDAQ device are:

  • Two analog input channels that students can configure either as general-purpose high-impedance differential voltage input or audio input
  • Two analog output channels configured either as general-purpose voltage output or audio output
  • Eight digital I/O channels with programmable function interfaces with one used as the counter
  • Fixed power supplies
  • One digital multimeter

We created two modules that directly connect to the NI myDAQ system to condition and control the signal for measuring the characteristics of solar cells and wind turbines.

Using the NI myDAQ device, students can perform lab work outside laboratories. They need a laptop running LabVIEW and the RELab LabVIEW project, an NI myDAQ device, and the miniSolarLab and miniWindLab to create experiments that study the solar cell and wind turbine at home or in parks.

Saving Time, Lowering Cost

The RELab and miniRELab systems offer students extremely useful tools to learn about renewable energy sources. We achieved a compact solution using the NI ELVIS platform, which we can use in other laboratories by switching the prototyping board to greatly decrease lab costs. NI myDAQ gave us the small size and low cost we needed to create a portable version of RELab.

With LabVIEW as the programming language, we minimized development time and created a friendly, easy-to-use user interface. The LabVIEW VIs that come with NI ELVIS, such as the impedance analyzer, helped us increase the complexity and amount of the lab work. LabVIEW offers students the possibility to implement their own methods by developing new applications with subVIs.

Author Information:
Petru Adrian Cotfas, Lecturer
Transylvania University of Brasov, Romania
pcotfas@unitbv.ro

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