You can do a pretty nifty heliostat with passive heat collectors and a closed loop containing a fluid which vaporizes at a convenient temperature for shifting the center of gravity. (And dampers so wind buffeting doesn't jiggle the panel too much.)

That said, $30 of motors and $50 of controller board is probably cheaper and more accurate. The passive system is good enough for orienting solar panels, probably not for aiming a mirror.

You can't use passive systems like that for pointing a mirror at a stationary source since they will aim the mirror straight at the sun. The whole point is that the mirrors form a parabola and that you point each mirror slightly different. Passive hookups like you describe would aim all the mirrors in the same direction.

I've done some toying around with this and came up with a system that can run off a limited number of motors.

http://pics.ww.com/v/jacques/renewables/concentrator/8.jpg.h...

Have you seen how large the heliostats are? They look over 2 meters on each side, and the surface looks like glass or stainless steel. That's several thousand dollars of light engineering right there. Plus shipping to a desert, plus installation crew.

So you're looking at $100-$1000 of motor. Several hundred dollars for the controller board (how do they know where to point? Are they networked or something?), or thousands if you have to design it yourself. Then you have to cable power to it, all of which has to be up to code. The whole thing also has to be weatherproof in a desert and not blow over in the wind.

(The passive one-axis heliostat does sound interesting for DIY systems, though)

Agreed, turbines are precision mechanical devices and also need regular maintenance. High-pressure steam is aggressive stuff so all the plumbing needs to be built accordingly as well.

Speaking as former Nuclear Sub technician, there isn't much maintenance on the turbines (think transmission in a car -- it's not too often that you have to open it up) but the turbine, high precision machined stainless steel piping and equipment is very expensive. Our steam ran at 1000 psi plus, which we were told was high enough to cut a man in half if a small leak was sending out a stream.

Thanks for the link. Wow: This system used a 100,000 psi (690 MPa) pump to deliver a hypersonic liquid jet that could cut high strength alloys such as PH15-7-MO stainless steel.

I've used them and plasmacutters too, you don't want to point either at something you don't want to keep.