The fast development of mobile computing has raised ever-increasing diverse communication needs in wireless networks. To catch up with such needs, cloud-radio access networks (CRAN) is proposed to enable efficient radio resource sharing and management. By CRAN, it is possible to realize software defined access networks. At the same time, the massive deployment of radio access networks has caused huge energy consumption. Incorporating renewable green energy to lower the brown energy consumption also has become a widely concerned topic. In this chapter, we are motivated to investigate a green energy aware remote radio head (RRH) activation problem for coordinated multi-point (CoMP) communications in green energy powered CRAN, aiming at minimizing the network brown energy power consumption. The problem is first formulated into a non-convex optimization form. By analyzing the characteristics of the formulation, we further propose a heuristic algorithm based on an ordered selection method. Extensive simulation based experiment results show that the proposed green energy aware algorithm provides an effective way to reduce brown energy power consumption, well fitting the goal of developing green communications.