First of all, let’s have a look at the solar radiation which has been almost 5% lower than expected (about 1 312 instead of 1 376 kWh/m2.year). This situation is linked to the height of the trees which cast larger shadows than what expected during the design phase.
Nevertheless, in spite of this lower availability of ‘fuel’, the measured total yield is 485 500 kWh/year which means a 13% surplus related to the projected yield, calculated to be 429 571 kWh/year. This was due above all to the higher solar efficiency which, in the summer months, ranged from about 45% to 50%. For some months this higher efficiency was caused by the lower return temperature, if compared with the design value. However, July is a relevant exception: In spite of a solar radiation in line with the design figure and a return temperature slightly higher than the project value, the monthly yield was about 19% more than expected.
In the picture below, the monthly yields are reported by blue lines (‘Atteso’) for the design values and by orange lines (‘Effettivo’) for the measured results.
Source: SDH Energy, Varese Risorse.