The Illawarra Grammar School student took out the high school section of the national BHP Billiton science competition at a ceremony in Melbourne today.

His entry, the UView Protector badge, topped a field of 15 projects designed by young scientists from around the country,

The badge sticks to a person to measure when and where they are exposed to UV radiation.

It is the third time Ethan’s fascination with sun-safety has taken him to the top of the BHP contest, having won the primary school category twice in recent years, once for the UView project.

He can add today's accolade to an already-impressive list of awards, including the Young Scientist of the Year award in 2010 and 2011.

Not to be outshone, his sister Macinley, 11, took out the primary school category of the BHP competition for her invention the Reflectacon 3000, which reflects more sunlight onto solar panels to increase electricity output.

The national awards, which included a workshop with some of the CSIRO’s top science minds, attracted more than 6000 entries and Ethan said the scale of his achievement had yet to hit home.

‘‘It’s still as surreal as the last time,’’ he said.

CSIRO education national operations manager David Trotter said it was the first time a brother and sister pair had won both award categories.

‘‘They are obviously a very talented family. Both projects were extremely well researched and had very practical applications,’’ he said.

Ethan and Macinley were awarded cash prizes, while Ethan also scored a trip to Los Angeles in May, where he will compete at the Intel International Science and Engineering Fair for a share of a $3 million prize pool.