Curtailment of electricity occurs when there is not enough demand for the available supply. In the absence of some sort of grid storage strategy, whether batteries, pumped hydro, or other technology, the excess energy is simply wasted.
The Union of Concerned Scientists (UCS) has taken a look at the issue and found there are two primary causes of curtailment — system wide oversupply and local transmission constraints (same is the story in India).
The majority of that curtailed electricity is attributable to local transmission constraints, which UCS describes as follows. “This kind of curtailment occurs when there is so much renewable electricity in a local area that there is insufficient transmission infrastructure to deliver that electricity to a place where it could be used.”
8 strategies have been proposed for putting excess renewable energy to workes that are also endorsed by UCS.
These ideas basically center on constructing a smarter, more resilient grid that uses the available supply of electricity more efficiently. Electric cars can play an important part in that process if the charging infrastructure provides for powering chargers with excess electricity whenever possible.
Curtailment is an issue to be managed not feared. According to UCS curtailment, if managed properly, is an opportunity not a problem.
Reference- Clean Technica, UCS website