Will doubling your evacuated tube array produce an increase in flow?

Question: What affect does addition of an additional array of 30 tubes (30 to 60 tubes) and an increase in flow (double flow from 1 gpm to 2 gpm)

Note: T1 is located at the exit manifold of the first array. T* is located at the exit of the second array. T2 is the bottom of tank temperature.

Day 1: November 16, 2010.
Weather Condition: Partly sunny


Observation: The second array appears to contribute as many btus as the first array.

Day 2: November 22, 2010.
Weather Condition: Partly sunny


Conclusion: Cold, cloudy conditions severely diminish production, while sun quickly restores production.