Comparison of 100% renewable energy system scenarios with a focus on flexibility and cost

In this study, a particular class of energy system scenarios assuming 100% renewable energy (RE) are selected and compared. The purpose is to compare the relative characteristics of the scenarios, focusing on the amount and types of flexibility used and the predicted electricity generation cost. The approach included the screening of 45 studies (some of which contained multiple scenarios) to down-select to 8 studies, which used high-fidelity short-term energy system models. The compared scenarios applied many strategies for providing flexibility, which was found to be a crucial and significant component of a 100% RE system. Accordingly, only two of the fifteen examined scenarios contained a variable generation fraction greater than 65% of total scenario capacity (73% and 69%). Predicted electricity costs varied drastically in all regions. Some studies provided multiple scenarios (including business-as-usual scenarios and costs) that could be compared. In 3 out of the 4 studies including a business-as-usual cost, the 100% RE scenarios were found to be between 41% and 104% more expensive. The fourth study showed electricity costs to be the same for a 100% RE system and business-as-usual system, and the 100% RE system to be 62% cheaper when externalities are included.