The solar plant will be built on the Pirdop site, which is located 80 kilometres east of the Bulgarian capital Sofia, CEZ Bulgaria said in a statement.
The plant, which will have 20,200 solar panels and cover 10.4 hectares, is expected to become operational within 18 months.
"This project is part of the long-term investment programme of the company and is in line with our policy for sustainable development and transition to green economy," said Tim Kurt, chief executive of Aurubis Bulgaria.
Aurubis Bulgaria aims to produce 20% of the electricity needed for the operation of its copper smelter from own renewable energy sources by 2030, Kurt added.
The Pirdop copper smelter and refinery is the biggest facility for smelting and refining of copper in south-eastern Europe, with a capacity of 340,000 tonnes per year.