How was Nils Gustaf Dalén awarded the Nobel Prize?

Name: Nils Gustaf Dalén. 
Country: Sweden.
Date of Birth: 30 November 1869.
Died: 9 December 1937.
Known as: Wien’s law blackbody.
Noble Prize Year: Nobel Prize for Physics in 1912 for their research on the automatic regulators for use in conjunction with gas accumulators for illuminating lighthouses and buoys.