Measuring solar radiation with a distillometer

E. Linacre


A simple yet reliable instrument to measure the amount of solar radiation at ground level within a defined period is shown below. It is for. The outside is made of glass, including an upper sphere through which solar radiation passes, to heat a black copper sphere within. This sphere heats alcohol inside. Depending on the amount of radiation received, alcohol will vaporise at a certain rate, to condense in the stem, which is buried in the ground and therefore relatively cool. The amount of distillate collected there shows how much radiation has been received since last the instrument was reset. The instrument is reset by lifting it from the ground and reversing it, so that the distillate returns into the upper sphere. Advantages of the device are it is cheap to build, it needs no electricity and it can be used for periods longer than a day. This distillometer is ideal for developing countries.