Practice Solar Panel

Practice Solar Panel to AIMSC & VMSVC  2017 Regulations

The 2017 regulations governing the student designed car event have changed significantly from all previous regulations in the area of the solar panel used to drive these cars.

Under the 2017 regulations the car must race with a panel provided by the organisers, however for practice the competitors must provide their own solar panel.

This should not present any problems to most previous competitors as the panel to be provided by the organisers is a single Scorpio No. 26 panel (14 cells) calibrated to output 5.5 watts in full Sun. The majority of competitors have been using two such panels in past competitions, a simple reconfiguring of their existing panels will give them a practice panel.

 

To make a practice panel that exactly matches the panel to be provided by the organisers two actions are necessary, firstly mount the single Scorpio panel to an aluminium backing identical to the backing the organisers will be providing and secondly, calibrate the panel to produce 5.5 watts at full Sun.

 

The aluminium panel backing:

Details of the wiring and connectors is provided in the regulations, the aluminium backing will be manufactured to the following sketch.

 

Calibrating the panel:

Without a calibrated light box, it is difficult to achieve exact calibration, however the simple process described below detailing how calibration can be performed in Sunlight will give reasonable accuracy.

 

To calibrate the panel in Sunlight it is necessary to know the Sun level prevailing, this can be measured using a Scorpio No. 10 calibrated cell. For accuracy, it is essential to have the calibration cell and panel being measured in the same plane when measurements are being taken.

 

At a known Sun level measure the panel’s open circuit voltage (OCV) and short circuit current in amps (ISC). Make these measurements with the solar panel at 25 Degrees C and at a Sun level greater than 70% for best accuracy.

Approximate power can be calculated by multiplying voltage and current together then multiplying by 0.7 which is an average fill factor for these panels.

 

OCV × ISC × 0.7 = Power in watts

 

Having calculated the power at a specific Sun level as described above, ratio the power obtained up to the power expected at full Sun.

 

To calibrate the panel to produce 5.5 watts at full Sun, mask a portion of the panel with a light excluding covering to reduce the power produced to 5.5 watts. Note this covering should cover the same proportion of every cell in the panel.  The approximate size of the mask can be calculated using the calculated full Sun power and the desired 5.5 watt maximum and using the ratio of these powers to reduce the panel surface area by the same ratio.

 

Always recheck the panel power after masking to ensure the correct size of masking has been applied.   


(Special note: Not all Scorpio No.26 panels will produce 5.5 watts, some panels may only produce 5.2 watts. In past years Scorpio provided “standard panels” with a power output of from 5.2 to 5.8 watts at a lower cost than their “premium panels” which had power output above 5.8 watts.)