Comment by infogulch

Send up a spacecraft with back-to-back / equal area solar panels and radiators (have to reject heat backwards, can't reject it to your neighboring sphere elements!). Push your chip temp as much as possible (90C? 100C?). Find a favorable choice of vapor for a heat pump / Organic Rankine Cycle (possibly dual-loop) to boost the temp to 150C for the radiator. Cool the chip with vapor 20C below its running temp. 20-40% of the solar power goes to run the pumps, leaving 60-80% for the workload (a resistor with extra steps).

There are a lot of degrees of freedom to optimize something like this.

Spacecraft radiator system using a heat pump - https://patents.google.com/patent/US6883588B1/en