Reactors for conducting thermochemical processes with solar heat input, and associated systems and methods. A system in accordance with a particular embodiment include a reactor having a reaction zone, a reactant source coupled in fluid in communication with the reactant zone, and a solar concentrator having at least one concentrator surface positionable to direct solar energy to a focal area. The system can further include an actuator coupled to the solar concentrator to move the solar concentrator relative to the sun, and a controller operatively coupled to the actuator. The controller can be programmed with instructions that, when executed, direct the actuator to position the solar concentrator to focus the solar energy on the reaction zone when the solar energy is above a threshold level, and direct the actuator to position the solar concentrator to point to a location in the sky having relatively little radiant energy to cool an object positioned at the focal area when the solar energy is below the threshold level.