Solar Cooking by Season and Latitude: Where and When a Small Box Cooker Actually Cooks

This study simulates a small horizontal box cooker, with an aperture of 0.25 m2, an optical efficiency of 0.70 and a lumped heat-loss coefficient of 1.2 W/K, at latitudes of 0, 15, 30 and 45 degrees on four representative days, using computed solar geometry, a stated clear-sky irradiance model and stated cloud fractions. The work is simulated, not measured. In 8 of the 16 latitude and season combinations the pot never reaches 100 degrees C at all. Water pasteurisation, defined here as at least 0.5 hours above 65 degrees C, succeeds in 14 of 16 combinations; rice, defined as at least 0.75 hours above 95 degrees C, succeeds in 10 of 16; soaked beans, defined as at least 3.0 hours above 100 degrees C, succeed in 8 of 16; and flatbread, defined as requiring a peak of 150 degrees C, succeeds in none. At 45 degrees in winter the peak pot temperature is 19.8 degrees C and the time above 100 degrees C is 0.0 hours, so the device does not cook in that place and season under the stated assumptions. At 45 degrees in summer, by contrast, the peak is 120.2 degrees C with 5.57 hours above 100 degrees C. The honest map is therefore strongly seasonal and strongly dependent on latitude: the cooker is a fair-weather, low-to-mid-latitude, midday device, not a year-round cooker at higher latitudes.