I was a bit excited to watch this rare event of a regrettably not total, but nevertheless heavy partial solar eclipse. In 1999 we had a total eclipse in parts of Luxembourg, and I made some measurements and wrote a small comment on the meteorological impacts. So today I built up a telescope with a small projection screen and a datalogger with T/H sensor and an old pyranometer (which had its output amplified by an instrumentation amplifier I assembled a couple of years ago). The following picture shows this material, and also gives an impression of the heavy fog covering the whole valley of the river Sauer where Diekirch is located.
The next picture is a close-up on the datalogger (a vintage faithful German 12bit Mikromec logger from 1990), with the instrumentation amplifier and the Kip and Zonen gray pyranometer; the Rotronic T/H sensor lies below the table, visible at the lower border of the picture. The white sensor at the rear is our Solarlight UVA sensor.
Alas, the fog was very persistent, so that the sun became visible only during the last part of the eclipse.
The next close-up shows the big sunspot AR2303 close to the moon’s border:
So despite the disappointing viewing conditions, we nevertheless had at least the beautiful view of a big and nearly circular sunspot close to the vanishing moon shadow.
The last figure shows the variations of air temperature and solar irradiance during the eclipse; at the moment of maximum cover the solar disc was still completely invisible, but nevertheless the dip in solar irradiance is clearly visible:
Air temperature also goes down by about 0.5 °C with a possible small delay. This is similar to the observations made in 1999 (see 3rd figure).
added 21 March 2015:
Here is the graph of German solar electricity production; the sharp dip of 7 GW was filled by conventional fossil producers. As great parts of the country were covered by fog, the ramp up was not so spectacular as feared (it took a bit more than an hour from trough to peak), and the electrical grid remained stable (graph from here). Be careful with the left axis: the numbers do not seem correct, as DW gives those inserted in the graph.:
The HTW (Hochschule für Technik und Wirtschaft, Berlin) has published (prior to the eclipse) an interesting study with several simulations of the effect on German solar electricity production.