It is difficult to compare the performance of solar panels from various manufacturers. The only data available is often the electrical characteristics data sheet for each solar panel. This data only reveals the performance of the solar panel under ideal laboratory conditions. It would be nice to compare the performance of various solar panels mounted side-by-side, all experiencing the same, true Australian weather conditions, with a mixture of cloudy and sunny skies in cold and hot conditions. We at Re-Energy have commenced (from 9th March 2012) an experiment that will measure the performance of 13 solar panels from various well-known manufacturers. We hope to add many more solar panels to the experiment in the future. We are always interested in anyone who is willing to include their solar panel to the experiment. The experiment is located on the roof of the Ballarat TAFE and we greatly appreciate their interest and roof space to conduct this experiment. A specially designed instrument was constructed at Re-Energy to measure the "Maximum" output power from each of the 13 solar panels. The maximum output power from each solar panel is measured every 15 minutes and recorded on a computer system using specially developed software. Data is collected over a week and then downloaded for further analysis. From the data a figure known as "Electrical Energy Yield" is calculated, this indicates how well the solar panel is
performing. Basically "Electrical Energy Yield" tells us how much energy the solar panel is producing over a day compared to the rated power output of the solar panel. It is important to measure "Electrical Energy Yield" as this is what the power providers actually pay the customers for. For example: a 100 Watt solar panel from one manufacturer with a high "Electrical Energy Yield" could produce as much energy as a 120 Watt solar panel with a lower "Electrical Energy Yield" from another manufacturer. The experiment been going from March 2012. We welcome you to visit our web site from time-to-time to check up on the performance of our solar panels and any other interesting developments that have occurred.
Dr. Henry Senko
This analyser has 16 inputs, although any number can be accommodated, each input has its own relay as a means of individually selecting a
panel. After the hundredth step the load current is reduced to zero and the energized relay de-energized. The Solar Panel Analyser commences by selecting the solar panel to be measured by means of energizing the appropriate relay connecting the selected solar panel to the input of the analyser. A microcontroller within the analyser measures the voltage of the solar panel with no load, this is known as the "Open circuit voltage, (Voc)". The microcontroller checks if the measured value of Voc approaches its rated value as a means of checking that everything is connected correctly. If Voc is well below the rated value an error message is recorded otherwise the microcontroller moves on to the next phase and instructs a variable load to draw current from the solar panel in increasing steps.
The current drawn increases until the solar panel can no longer comfortably supply the requested current and its output voltage begins to drop.
The current drawn continues to increase until the output voltage from the panel reduces to 3 volts, this in effect represents the "Short circuit current, (Isc)". The voltage and current at each step is measured and stored in the microcontroller's internal memory. One hundred steps are used to completely characterise the solar panel, each step taking 25ms resulting in 2.5 seconds for the whole measurement connecting the selected solar panel from the analyser. The microcontroller then looks back at the recorded data stored in memory and calculates the power produced by the solar panel at each step by multiplying the voltage and current values of each step. The power produced for each of the one hundred steps is calculated from which the maximum value is selected. The maximum value is known as the "Maximum power point (Mpp) which represents the maximum power the solar panel is capable of producing at that time under the available light and real life operating temperatures. The maximum power point value is then sent to a personal computer to permanently record the Mpp value along with the time at which the measurement was taken. The microcontroller then energises the next relay and the whole process is repeated. After all 16 solar panels have been measured the microcontroller waits 15 minutes and the whole process is repeated over and over, capturing the performance of each solar panel throughout the whole day.
Dr. Henry Senko