Measurements of Photovoltaic Solar Panel Efficiency Using NI Data Acquisition Devices

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"For C users, LabVIEW is still very easy to use, but requires a different way of thinking about system architecture. Fortunately, there were plenty of examples available in the LabVIEW Example Finder and on the web, and we received very quick answers from the NI technical support team."

- Sławomir Suski, Lean-Soft sp. z o.o.

The Challenge:
Developing a monitoring system that can analyze the various parameters of photovoltaic (PV) solar panels in different weather conditions, and another similar system that can be used inside the production facility to measure the quality of the air to comply with European Union safety regulations.

The Solution:
Using NI CompactDAQ hardware and LabVIEW software to develop a PV solar panel monitoring solution that can monitor the parameters of the environmental variables online, store the data in text files, and access the historical data in the database.

Author(s):
Sławomir Suski - Lean-Soft sp. z o.o.

Solar panel technology is becoming more popular in both industry and the private sector. There are various reasons for choosing solar panels including government regulations such as country-level limits on carbon dioxide pollutions and the trend toward green engineering. When using PV cells, no harmful substances are produced, unlike with coal plants, which emit carbon dioxide, sulfur, and nitrogen oxide. According to the European Photovoltaic Industry Association, worldwide growth in new PV systems connected to the grid reached more than 66 percent, from 16.6 GW in 2010 to 27.7 GW in 2011. It’s estimated that Europe delivers almost 21 GW [1].

Bauer Solar Production, a customer of Lean-Soft, is a company that produces world-class solar panels used both in the industry and private sectors. The recently opened facility in Dąbrowa Górnicza, Poland, produces various types of solar panels, including those based on monocrystalline and polycrystalline silicon cells. To better fit customers’ needs, it is important to understand which types of panels (mono- or polycrystalline) are better-suited for various weather conditions.

Approach and Measurements

Bauer Solar Production’s previous monitoring system was based on SolarLog, and it didn’t give the company the flexibility it needed to perform more advanced measurements. Thus, when looking to develop a new system, our customer requested a few important features, including:

• Firebird database logging
• Online and offline analysis capabilities
• Connection to an existing DAQ system (Lean-QS)

We chose the NI cDAQ-9188 eight-slot Ethernet chassis for this system because it was easy to connect to the facility’s network infrastructure and it did not require a supervising computer close to the weather station. The device was mounted in a special case placed on the roof of the building, so we required the system to be rugged enough to survive cold winters and hot summers.

Our customer needed a monitoring system that considered the following solar panel environmental variables and parameters:

• Outside temperature
• Moisture
• Air pressure
• Wind speed and direction
• Solar panel output voltage
• Solar panel output current
• Solar radiation

We used a DELTA OHM weather station to help us obtain all environmental variables without the need to buy and mount additional sensors.

The application for our project was written in NI LabVIEW software, with NI-DAQmx drivers, using a state machine architecture. For C users, LabVIEW is still very easy to use, but requires a different way of thinking about the system architecture. Fortunately, there were plenty of examples available in the LabVIEW Example Finder and on the web, and we received very quick responses from the NI technical support team.

The measured parameters are displayed on waveform charts on the front panel to give online access to all the necessary data. The data is also stored in text files (every 24 hours we create another file), and it is continuously stored in the Firebird open source relational database. All connectivity with the database is accomplished using the LabVIEW Database Connectivity Toolkit. Data stored in text files helps our customer analyze all changes in the power output of the solar panels using third-party tools such as Microsoft Excel. It is very important for our customers to have access to the historical data because they need to understand how much power is delivered by the panel because of variances in solar radiation and sky clearness during different periods of the year. Also, the customer would like to understand how panel efficiency changes with time because of dirt and aging.

Future Plans

Our customer is planning to perform additional measurements with various types of loads connected to the solar panel. The first approach will be to use a sheer resistive load with something as simple as a water pump that can work with currents up to 8 A and voltages within a 23 V to 30 V range.  Also, we would like to create a system that is similar to the one that can be used inside the facility. Its main purpose would be to analyze environmental factors such as harmful gases. Knowledge about air quality in the building can help us guarantee that we comply with all European Union safety regulation.

Benefits of using NI platforms

The solution based on NI data acquisition hardware helped us develop a monitoring system for the solar panels. We can monitor the parameters of the environmental variables online, store the data in text files, and access the historical data in the database. All of these functions make the solution flexible, easy to use, and expandable in future.

Author Information:
Sławomir Suski
Lean-Soft sp. z o.o.
55/2 Szarych Szeregów
Katowice 40-750
Poland
slawomirsuski@lean-soft.com

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