Some kind of large aerostat / inflatabe chimney reaching up till the tropopause largely insulating for most of its length, but with heat engines on top and on bottom. I'm not proposing to use water / ice transition, but just consider a hypothetical strong suspension system, heaving a bucket of water weighing 1 mass unit can be powered by lowering a bucket of ice weighing 1 mass unit (ignore tiny density difference). So one can simultaneously bring 2 thermal baths close together, both at the bottom of the heat loop (where ambient temperature and tropopause temperature in the loop are close by each other) as well as at the top (where ambient cold tropopause temperature and surface temperature in the loop are close by each other). So both at the top and the bottom mechanical power can be generated with a heat engine.

The ground level vs tropopause temperature difference is not perfectly stable but largely maintained throughout day and night cycles, it is effectively base load, no nuclear required! We could generate energy while helping the planet cool.

Best to place these in seas, at least 1 structure length away from coastline, not in the middle of densely populated area. Salty sea water can be frozen (purifying it because ions get pushed into the brine) for desalination, brought to conventional thermal power plants, melted on their cold sides producing potable water while improving the thermodynamic efficiency of the thermal power plant (more electric energy per unit of fuel / rod spent).