The article insists on the plant's low maintenance costs, so this may be a stupid question, but won't the greenhouse* have to be washed regularly of dust? I imagine the accumulation of detritus would significantly impact power production.
Edit: I previously had written mirrors. The concept art looked misleadingly shiny.
Compared to the cost of buying coal or natural gas and keeping all the machinery that moves and burns that clean, cleaning out the dust and debris this building takes in should cost relatively little.
if you think about the temperatures and pressures inside of modern combined cycle gas fired power plants, they need an exceptional amount of maintenance and repair. i'm sure the dirt loading is going to be a problem for these guys, but nowhere near the complexity and cost of super heated steam lines and huge boilers.
Edit: I previously had written mirrors. The concept art looked misleadingly shiny.