About the Vernier Solar Power Dashboard

PVPowered Inverters

We chose to use Inverters (which change the DC electricity producted by the panels into 120-V AC) made by PVPowered. These inverters were recommended by our solar panel installation company and they are made in our home state of Oregon.

They have the option of adding a StarLink card for internet connnectivity. The StarLink card adds a computer ethernet network port to transmit data about the energy output from the inverter. In most situations the StarLink card is used to send data to PVPowered's data monitoring hosted solution, mypvpower.com. Solar panel owners can then go to the mypvpower.com web site and check on their panel's production.

However, we wanted to track the our solar data internally and to combine it with weather data taken at our building. To do this, we wrote a custom program to communicate with the inverters.

Sharing Solar Data on the Web

Our original setup used a java program provided by PVPower, which was run from a web script to collect data into a database. It worked, but it suffered from performance and reliability issues. The Java program executed every five minutes from a web script. This starting and stopping of the JVM resulted in a huge performance hit which slowed the site to a crawl. In our current system, we rewrote the Java program to run in the background all the time, collecting and storing energy data from the solar panels every five minutes.

Along with creating a new Java program to collect the solar data in our current system, we decided to redo the dashboard to be more informative, usable, and visually appealing. The hourly energy production data from the original setup was interesting since it displayed how much energy we were producing in clear and easily understandable way.

However, we were also interested in the amount each inverter was contributing to the total individually, so we changed the bar chart to a stacked column chart. Furthermore, we wanted to quick way to see the current power level of each inverter and how close we were to reaching maximum capacity. We decided power gauages were the best way to do this.

We use a charting package called AnyChart create our new charts. AnyChart provides a huge library of chart types and is highly customizable.

Adding Weather Data

Next, we wanted to see the relationship between energy production and the weather. We have a Davis Weather Station that allows us to monitor the current weather conditions. In combination with a Vantage Pro console and WeatherLink software, we were able to collect data as well. In the original setup, we had the WeatherLink software upload a text file to a separate computer that collected the solar data. It caused problems if there were ever connectivity issues or either computer had downtime.

In our current setup, we have solar and weather data collected on a single computer. The WeatherLink software is Windows only and the new setup was a Linux computer. We searched around and found an open source software package called wview which can collect and store data from a variety of different weather stations including the Davis Weather Station.

wview is able to directly store the weather data in a database which made it very easy to combine with the solar energy data. This made updating our scripts like the Logger Pro data export very easy.

Considerations

The new collection setup is much more efficient and reliable than the old setup. Consolidating all the data collection to a single computer made analyzing the data much easier and reliable. We still have the problem with the inverters misreporting numbers, however, we have decided to leave these errors in the data to preserve the integrity of the data and as an exercise to the student—no experiment is perfect.

Technical Details

For those interested in the hardware and software of our current setup:

• Solar data computer specifications
  • CPU: Intel Pentium 4 1.6 GHz
  • Memory: 768 MB
  • Operating System: Ubuntu Linux 9.04
• Web technologies
  • Web Scripting Language: PHP 5.2.6
  • Database: MySQL 5.0.75
  • Web Server: Apache 2.2.11

Closing Remarks

We hope this information was useful as a behind-the-scenes look at how we created the Vernier Solar Dashboard. If you have any comments, questions, suggestions, feel free to contact us—especially if you create one yourselves.