This report summarizes the challenges to integrating increasing amounts of variable renewable energy (RE), identifies emerging practices in power system planning and operation that can facilitate grid integration, and proposes a unifying concept-economic carrying capacity-that can provide a framework for evaluating actions to accommodate higher penetrations of RE. There is growing recognition that while technical challenges to variable RE integration are real, they can generally be addressed via a variety of solutions that vary in implementation cost. As a result, limits to RE penetration are primarily economic, driven by factors that include transmission and the flexibility of the power grid to balance supply and demand. This limit can be expressed as economic carrying capacity, or the point at which variable RE is no longer economically competitive or desirable to the system or society. Studies have demonstrated that carrying capacity is not fixed and can be improved through technical and institutional changes. This creates the possibility to achieve even higher penetration levels through strategic investments in both demand- and supply-side sources of flexibility.
National Renewable Energy Laboratory
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