To be able to understand the dynamics of energy systems, the interplay between a variety of factors affecting them has to be addressed. In this thesis, we look at issues like climate change, energy policy, power transmission, energy storage and energy technology, to discuss the role of hydroelectric power in present and future energy systems. A model predicting future carbon emissions and temperature change has been developed, showing the dependence of possible climate change abatement on how soon and how fast we can reduce global emissions, underlining the importance of switching from non-renewable to renewable energy sources in the future. The increasing importance of stable and predictable renewables is highlighted, arguing that hydroele...