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Hot water produced by the thermic solar panel, solar irradiance measured by the pyranometer and electricity produced by the photovoltaic panel on 27-05-2017.

The cumulated volume of hot water used today since 0:00 AM is 48 liters.

The solar panel is a Viessmann Vitosol 300 vacuum tube collector. It is installed on the roof of our home in Louvain-la-Neuve, Belgium (longitude : 4° 36'; latitude : 50° 40' 6). The roof faces directly south and has a slope of 45°. Technical specifications about the panel can be found on this site by Viessmann. The panel was installed by SANIFLO.

The upper graph displays the minute by minute evolution of the temperatures mesured using four temperature probes. The location of the probes are depicted in the figure hereunder. Each probe is represented by a different colour (blue, red, green and orange). The scale for temperature is on the left hand side of the graph. In addition, the number of liters of hot water drawn from the tank is represented by black vertical bars. The length of each bar is proportional to the number of liters which have been drawn during the corresponding minute. The scale for the water volumes is on the right hand side of the graph.
The second graph plots the solar instant (magenta, W/sq.m) and cumulated (black, kWh/sq.meter) irradiance measured using an Eppley PSP pyranometer.
The lower graph shows the electric power produced by the photovoltaic panel (cyan, watt for a total panel area of 21 sq.m), along with the cumulated yield (black, kWh).

Pictures and additional explantion about the solar collector, the data acquisition system and the pyranometer.

The Gaisma Website, which provides solar and meteorologic data about Louvain-la-Neuve