reported By Jeanny Lim (swied@infothe.com)

Please give us an overview of National Instruments’ activities in the photovoltaics market.

Established in 1976, National Instruments (NI) has been transforming the way engineers and scientists design, prototype and deploy systems for measurement, automation and embedded applications. NI empowers customers with off-the-shelf graphical programming software such as NI LabVIEW and modular cost-effective hardware, and sells to a broad base of more than 30,000 different companies worldwide, with no one customer representing more than 3% of revenue and no one industry representing more than 15% of revenue.

As we provide our products to a wide variety of industries, we may not have been regarded as a solution provider capable of providing specialized solutions. However, in the solar industry, NI has been watching closely at the market since 2007 and found that there were unmet customer needs that NI could satisfy with our expertise and experience in test and measurement. NI has been focusing on developing eqiupment and solutions that are not available in the market. Using our easy-to-program software and modular hardware, customers in the solar industry can simplify development, increase productivity, and dramatically reduce time to market.

In Korea, development of thin-film solar modules has been booming lately and the need for PV module performance test systems rises fast. NI is focused on offering PV module performance test systems to solar cell manufacturers; especially on chronical variance of PV modules’ efficiency outdoor. From 2007, we have been marketing our solutions to the solar industry and now customers approach us first with their own unmet needs for PV module test solutions.

We understand that you hold an event every year to show your capabilities in the green energy industry, which is called NI Green Days. Could you introduce this year’s event, which were held in five major cities in Korea in May?

In 2008, NI’s biggest event NI Days introduced a new session for renewable energy. The session generated huge attention, so we turned the session into an independent technology conference starting from 2009. At NI Green Days, we introduce our solutions tailored for the green industry including renewable energy, energy management and smart grid and show how they are applied. We believe our solutions can address emerging market needs of the green energy industry which traditional approaches couldn’t satisfy, thus helping PV companies in achieving their goals and contributing to the growth of the industry.

For NI’s solar operations, NI Korea plays an important role. Unlike many other global companies whose global-scale marketing campaigns are initiated by the headquarters, NI’s solar marketing is planned at NI Korea and executed in the Korean market first and the approach is adopted by the headquarters. NI Korea is well-positioned to spot market needs because the Korean solar industry has been going through rapid changes in a relatively short period of time, presenting an ideal environment for studying market challenges and finding breakthroughs. When NI Korea produces an idea to meet new market requirements, the corporate then mobilizes our excellent infrastructure to materialize it.

How well are NI’s products accepted in the solar PV market?

Graphical programming environment LabVIEW has been used by millions of engineers and scientists to develop sophisticated measurement, test, and control systems using intuitive graphical icons and wires that resemble a flowchart. LabVIEW offers unrivaled integration with thousands of hardware devices and provides hundreds of built-in libraries for advanced analysis and data visualization. The LabVIEW platform is scalable across multiple targets and operating systems, and since its introduction in 1986 has become an industry leader.

With its capabilities of easy programming and fast development, NI believes LabVIEW can meet the changing needs of the solar market and help solar companies remain competitive in a fast-paced market environment. In particular, LabVIEW’s flexibility to integrate with many industrial protocols makes it an ideal choice for testing and monitoring performance of PV cells and modules.

In the photovoltaics industry, NI provides solutions for PV test and monitoring. Could you introduce them?

To expose the performance and efficiency of new Photovoltaic (PV) technologies, solar engineers must perform IV curve tracing to elicit the forward characteristics of cells in addition to performing breakdown tests to find reverse characteristics. These tests require an instrument capable of sourcing and sinking power from a cell and precisely measuring voltage and current. Software analysis can then help derive important performance parameters such as maximum power and fill factor.

With the announcement of a new PXI Source Measure Unit (SMU) from National Instruments, engineers can now apply the benefits of the PXI platform to testing and characterizing PV cells. The NI PXI-4130 SMU offers a four-quadrant output that can source up to 40 W and sink up to 10 W, which is useful for exposing both the forward and reverse characteristics of PV cells. The SMU also incorporates precision current measurements as well as remote (4-wire) sense capability, making it a flexible instrument for testing new PV technologies. Occupying only a single PXI slot, engineers can use this new power SMU in parallel test applications to achieve up to 17 SMU channels in a 19 in., 4U space. The PXI-4130 complements the existing NI platform of tools and technologies that facilitate green engineering.

In addition, NI offers MW-scale Real-Time field I-V monitoring system for PV modules with monitoring efficiency of PV module simultaneously. Existing solutions in the market focuses on monitoring how much power is produced from which PV plant, but the recent trend is towards extracting more data.

The key in PV module efficiency monitoring lies in accurate measurement of performance. Weather conditions such as sunlight, wind and cloud change every minute and comparing performances based soley on Pmax is not going to work.

NI has found that there was no monitoring solution taking a wide range of variables into consideration. We also found that the market required a solution that did not need an expensive solar simulator and was capable of measuring PV module performance changes with time. In responding to the market demand, NI has devleoped a efficiency monitoring solution for PV modules/cells that is cost effective and can help cell/module manufacturers perform tests with greater accuracy and increased throughput.

Essentially this solution involves the integration of a Personal Computer (PC), Data Acquisition (DAQ), a battery array and a Solar Array Simulator (SAS) to create a stand-alone PV system and to test and simulate the system. This new system boasts of high accuracy measurements coupled with the commercial viability of low cost. The basic idea of this system is that the SAS simulates solar power which is utilized to charge batteries. The information obtained by monitoring parameters, such as average battery’s temperature, voltage and current, is fed to the PC via the DAQ for analysis. This customized control interface has been developed by utilizing LabVIEW software, which forms the programming backbone of inter-instrument communication via IEEE-GPIB bus. The software created for this system is highly generic and can be used for other instances where different hardware is used.

NI’s Real-Time field I-V monitoring system for PV module performs tests with natural light without using an expensive solar simulator, which is why the solution is gaining its popularity in the PV industry. It dominates about 70% of the market for continuous and pulsed I-V curve monitoring in the open air.

Please tell us about the market for solar control and monitoring systems. Can you comment on market size and growth potential?

From a test and measurement company’s point of view, the solar market can be divided into three areas: control, test and monitoring. Solar companies around the world are developing a technology that improves the efficiency of a PV cell in producing electricity and want to test the performance of their prototypes under various meteorological conditions and installation types. Therefore, demand for cell/module performance test is here to stay. In the meantime, the market is also seeing the growth in production equipment. As countries strive to replace import equipment with indigenous ones, technologies for PV manufacturing have great potential for growth.

Then, what is NI doing in the PV manufacturing equipment area?

At NI, PV module performance monitoring plays an important role in generating revenues, but we believe stable income should come from the manufacturing equipment sector. NI is now working on developing advanced manufacturing solutions for PV equipment manufacturers.

NI hardware and software can be used to increase efficiency throughout the solar panel production process, from purifying silicon ore to manufacturing and testing the final product.

On the manufacturing equipment side, we use CompactRIO hardware. It performs better than PLC and has built-in Field-Programmable Gate Array (FPGA), a silicon chip with unconnected gates. Based on this, we will provide Maximum Power Point Tracking (MPPT).

Solar cells have an optimization point, known as the maximum power point, where the power transfer from the cell to the load is optimal. This maximum power point varies with environmental conditions such as the temperature and amount of sunlight illumination. If the output voltage of the solar array is fixed, the maximum power output cannot be continuously generated. We use maximum power point tracking algorithms to increase the overall power generation efficiency by continuously locating and tracking the maximum power point by adjusting the voltage output of the array using a DC to DC converter. MPPT techniques reduce PV array system costs by reducing the number of solar panels needed to obtain a given amount of output power.

To improve the control design of solar cell MPPT, we developed an MPPT system that fits a quadratic equation to the power-voltage curve of the cell and calculates the maximum value of the quadratic function to locate the maximum power point. The system must produce high-speed Pulse-Width Modulation (PWM) signals to control the voltage converter and provide high-speed data acquisition. In addition, we wanted to develop a portable, embedded maximum power point calculation system to ship for future applications.

We used NI CompactRIO with the NI LabVIEW FPGA Module to develop a stable, efficient, and integrated system. To minimize the power consumption, the CompactRIO system also contains a power switch controlled by a turn-on timer. We used analog measurements and actual test results to validate the feasibility of the system to develop an MPPT controller. 

Jeanny Lim is Editor-in-Chief of InterPV. Send your comments to mail%20to%20swied@infothe.com.

For more information, please send your e-mails to pved@infothe.com.

ⓒ www.interpv.net All rights reserved