Solar Light Bulbs: Effect of the Volume and Shape of the Pet Bottles on the Luminous Flux

The solar light bulb is a one-liter bottle filled with water that uses the refraction of sunlight. In many places, it is not expected the consumption of 1-liter bottles but other capacities. This study shows the effect of the shape of the PET bottles and how the capacity influences the luminous flux resulting from the solar refraction. A total of nine solar bulb models were used with different shapes and capacities (600 mL, 1 L, and 1.5 L). The results showed no interaction between the two factors where the best luminous flux was obtained using the 1 L and 1.5 L bottles regardless of the shape, ranging from 116 to 143 lux. This outcome expands the variety of PET bottles that can be recycled to build solar light bulbs.