The radiation is slightly affected by the solar panel, but the sensor is mounted at the end of a long cross arm to minimize this effect. We see a larger effect from the nearby buildings and trees, especially during the low sun angles of winter. We estimate that the shading effect is about 5% in the summer months and about 10% in the winter months. This means that our measurements are representative of this location.

We are working on adding a reference pyranometer on the roof of a nearby building to get unobstructed solar radiation data.

Regarding the best location for measuringsolar radiation in a greenhouse; I recommend characterizing the percent shading for each greenhouse section and then measuring the radiation outside the greenhouse in an unobstructed location. The shading fraction for the greenhouse should be constant for each season of the year and it only needs to be characterized once (as long as the covering material stays clean).

Bruce Bugbee