On the left you can see a reasonable day of sunsunshine on an untracked PV systemthe gradual increase in power to the mid day peak (system was pointing south) roughlyly an hour at the peak power then followed by a gradual decrease and return to zero. On the right you can see a gradual in crease to maximum power to a peak at about 10:10hrs then max power maintained till 1430 and a gradual decrease and return to zero.

Observations of the of the system showed:-

• The same PV's were used both tracked and Untracked
• The two chosen days were similar winters days.
• There was a fare amount of haze on the horizon for the sun to rise above before full power could be attained. Equally the sun sank into this haze at the end of the day. This accounts for some of the gradual rise and fall to max power.
• The battery was near fully charged on the second test and the gradual decrease in max power was the battery charge regulator maintaining a 28V max voltage and so reduceing the total power requested from the PV's.

Raw Data:-

• You'll need Open Office (free), Excel viewer (free) or Excel (well overpriced)
• 2009/12/25
• 2010/01/07

Conclusions:-

• The system untracked reached an max power of 298W at 1120hrs and maintained it till 1220hrs a total of 1hour 10 mins. Giving a total kWh for the day of 1.3kWh
• The tracked system reached peak power at 1010hrs and maintained it till 1430 at total of 4hrs and 20mins. Giving a total kWh for the day of 1.7kWh.
• The increase in energy out of the system is 1-(1.3/1.7) *100% = 23.5% more.
• On a (good) Summers day the period at max power would be longer still and the increase would be greater.