Nowadays, datacenters are one of the most consuming devices due to the increase in cloud, web-services and high performance computing demands all over the world. To be clean and without connection to the grid, datacenters projects tempt to feed electricity with renewable energy sources and storage elements. This power production needs an energy management providing power envelopes as a constraint to the datacenter management system. This paper presents an optimization module that optimizes the IT load under renewable energy constraints and outputs the power consumed by the computing resources of a datacenter. We are able to obtain a reduction of up to 73% in the tasks violations while respecting a given power envelope