Photovoltaics aren't very efficient.
Solar collectors heat water (and can provide space heating) but don't produce electricity.
The idea is simple and obvious but a Web search showed nothing much like it.
A tubular solar collector is mounted in an appropriate location. It is fed with liquid
octane (B.P. about 150C) from a feed/expansion tank.
When the panel gets hot, the octane vapourises. The vapour passes through a triple expansion reciprocating piston engine which converts the energy to mechanical rotation which drives a generator.
The exhaust gas passes to a condenser located in a large tank of water. Since the water cannot exceed 100C without boiling, the octane is always condensed. This provides hot water from "waste" heat.
The liquid is pumped back into the feed/expansion tank through a non-return valve. The feed pump is powered either by power tapped off the generator, or (better) directly off the engine's driveshaft.
The working fluid circulation is a closed system.
Octane is widely available and its physical chemistry is well understood.