A Stirling engine is simpler than reciprocating ICE -- no cams or poppet valves, etc. The engine in production cars is only $1,000 or $10 /kW.
In contrast photovoltaic is still over $5000/ kilowatt.
What is expensive with stirling solar are mirrors mounted on structures. They need to eliminate the structures, dig a lot of holes, pour some concrete, mount the mirrors on rollers in the holes and have the engine slide back & forth over well designed humps on the ground.
Fence it off so coyotes don't get sleep on the mirrors at night.
Bret Cahill