Fulltiming with pets?

Thank you everyone for your advice! The reason I am looking into a truck camper and not something larger like a motorhome, is because I dont think I could handle driving anything larger or handle a 5th wheel. I will be in Colorado, and the weather can change daily, sometimes hourly. Two days ago it was 85 degrees and clear skies and the last few days have been cold and rain/sleet. My friend used to have a truck camper and I remember it being tight, but honestly I dont mind it. My dog rarely leaves my bed now, unless we are going outside, so Im not concerned out sharing a tight area with her. Im just concerned about keeping the camper cool while Im away. Other than opening windows, is the non electric ways of cooling a camper? For instance a fan or a/c powered by solar panels.