Passive Cooling for Medicine Storage in a Hot Clinic Without Reliable Power: A Radiative, Evaporative and Thermal-Mass Cabinet Design and Its Computed Climate Envelope

Design study for a passive drug cabinet for a hot clinic with no reliable power, combining night-sky radiative cooling, an indirect evaporative jacket, an 80 kg water thermal store and 100 mm polyurethane insulation. A lumped thermal model integrated over 48 hours finds the cabinet holds at or below 25 C on a 40 C peak, 20% daytime humidity day (maximum 24.95 C radiative only, 23.84 C with evaporation). A sweep of 48 climate combinations (peaks 32-45 C, humidity 10-80%) finds 23 combinations hold on radiative cooling alone, 3 hold only with the evaporative stage, and 22 fail, including all 45 C peaks and humid 40 C conditions. Parts cost is estimated at 670 USD. All results are simulated, not measured.