I've bought 15 mhs of Zen. Makes a decent return but I got pissed off because every time, without exception, the withdrawal of BTC does not work until multiple attempts are made. I asked for my money back and they told me to fuck off. Well I am still within the window of my credit card purchase and can tell them to fuck off and there is not a damn thing that they can do. It was only $350 CDN so I may just ride it out to get my ROI as I do get my BTC eventually.

Usually surplus power is stored up in batteries... but yes... they only work in the day.