The Madrid-based group, which has assets in Europe and South America, aims to raise funds to finance new projects, the sources said.
Law firms Uria Menendez and Linklaters have been hired as advisors, the sources added. Spokespeople for Cox, Deutsche Bank, Uria Menendez and Linklaters declined to comment.
Cox owns solar plants in Spain and Portugal with potential capacity to supply 1,300 gigawatt hours per year. Last month, it signed a long-term deal to provide solar energy to fellow Spanish firm Audax Renovables. ($1 = 0.8169 euros)