There is nothing fundamentally wrong with a solar powered steam turbine, although Bram's description needs a pump between condenser and the boiler. Pressure in the boiler is higher than in condenser (this is why the turbine turns), and so a water pump is needed to counteract it. The pump can be mechanically driven by the turbine. The system looks like a perpetum-mobile, but it isn't, because it's not closed: energy is delivered into it by the Sun radiation.
A note regarding depressurizing the boiler is that any thermal cycle machine's efficiency is directly proportional to the temperature gradient. The temperature of the condenser in Bram's case cannot be lower than the temperature of the atmosphere, therefore it is advantageous to raise the temperature of the boiler (I think this is the primary reason why a plant's turbine is driven by superheated steam at 200 degrees Centigrade or more).