Greater penetrations of variable renewable generation on electric grids have resulted in increased levels of curtailment in recent years. Studies of renewable energy grid integration have found that curtailment levels may grow as the penetration of wind and solar energy generation increases. This paper reviews international experience with curtailment of wind and solar energy on bulk power systems in recent years, with a focus on eleven countries in Europe, North America, and Asia. It examines levels of curtailment, the causes of curtailment, curtailment methods and use of market-based dispatch, as well as operational, institutional, and other changes that are being made to reduce renewable energy curtailment.

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Pole positions related to remagnetized components isolated in Appalachian limestone and redbed rock units range over about 60 m.y. of the Permian-Carboniferous apparent polar wander path for North America. Apparent ages of remagnetization are older in the southern Appalachians and younger to the north. H the remagnetizations are associated with fluids expelled during the Alleghany orogeny, then the apparent remagnetization age trend could describe the timing of thrust-sheet emplacement.300 km Figure 1. Simplified map from Oliver (1986) showing spatial relation of Appalachian orogenic belt (cross-hatched area) to hydrocarbon deposits (black areas) noted by Oliver as first-order evidence of fluid flow. Smallest dots are locations sampled for K/Ar or Ar/Ar dating of authigenic minerals, medium dots are locations of single paleomagnetic results, and largest dots are locations of multiple paleomagnetic studies.588