The Roadmap 2050 Project is an ambitious study, commissioned by the European Climate Foundation (ECF), will rigorously examine the feasibility of achieving 80% greenhouse gas emission reductions in Europe by 2050. To achieve this goal the power sector must be almost fully decarbonized, which will require the integration of very high percentages of renewable power (60% to 80% or more). This is report one of three, which goes over the technical aspects of the project.