Energy consumption within communication networks is becoming a more significant problem as the scale of communication infrastructure increases. At the same time, large-scale electricity systems also face problems like transmission loss and energy shortage. Thus in this paper, we base our discussion on a communication system powered by a micro-grid system with renewable energy supplies, which is expected to address these problems well. Then, as a solution to the fluctuating output problem of renewable energies, we propose a transmission control algorithm to directly adapt the system power consumption in response to the fluctuation instead of using batteries as the energy buffer. Through simulation, we prove that our scheme can efficiently use such kind of fluctuating power supplies.