If you're lucky as hell that is. I did roughly 5 public events and my only rewards were two energies because they were the first publics in the day.
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You did pay attention to the 10-20% right? That means only 1 in 5-10 events would net you additional energy/shards, so since you did only 5, that's not really a surprise. I did 5 today as well, and go an additional energy in one of those 5. The key is to know the basic time cycle of Public events so you can do them more often.