PV-System, Performance

De PV-system comprises a compact array on the roof aimed East (= +115 degrees from North), in combination with a distributed setup on the flat roof, aimed South (= +205 degrees from North).

What performance under the influence of 'environment'?

Expected effiency per group is dependent on nominal power, viewing direction and 'environment'.
The first 2 aspects can be found in the table, whale the 3rd aspect is detemined by the trees & buildings in de vicinity, by actual weather and by the time of the year.
The readout by the various loggers allows to check each group in detail related to performance over the year.
In 2016 en 2017 no changes to the configuration, therefore good basis for comparison (although in February 2016 STECA1 was out).
The graphs below show the performance per group/inverter per year.
For an 'honest' comparison the performance per group/inverter is expressed in Wh/Wp, which is relative energy (Wh) vs. installed power (Wp).
Due to this calculatory correction the difference in size per group has no effect.

PV_winter PV_winter











Visible effects

  • STECA3, STECA4 and the Involars with their panels fully exposed have similar performance and set the standard.
  • SAJ1.5+CIS-panels exceeds expectation till july:
    • cool CIS-panels in combination with light-soaking have performance above spec
    • warm/hot CIS-panels perform according to spec
    • the inverter makes good use of the panels' output.
  • STECA1+CIS-panels however does not take any advantage of the cool period, and lags in the other period.
    Perhaps to be attributed to the different type of inverter?
  • STECA2 in Group C further back on the flat roof clearly is situated unfavourably with much shadow in morning and afternoon.
  • STECA5 in Group D also halfway the flat roof is not well performing either, but performs better than STECA2.
    Because the panels of Groups C and D lay in alternating sequence, the difference in performance seems an effect of different elevation of the panels (Group D = 10 degrees vs Group C =30 degrees).
In the graphs also a 'delta'-line which shows for the block of STECA-inverters the difference between the measurements by the SOLogger and the estimations by the PVLogger.
In the year-statistics this difference over 2016 and 2017 is <2%.
For other, comparable system configuration the difference is <3%.

Challenges for 2018:
1) how to get some extra performance from the 4 CIS-panels attached to STECA1?
Solved: the 4 CIS-panels shifted to another inverter (type Solis700) which can deal with them without limitations.
2 More CIS-panels connected to STECA1 raise the possible system-production by another 330Wp.
2) how to boost the groups with STECA2 and STECA5 to comparable performance as the other groups?

Additional (Dutch) PV-information

bovenkant pagina

Dutch version


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