However, if either the buyer or seller thinks there is a risk some of the generation won't be produced, there's still lots of ways to manage that risk in a relatively simple way. Probably the simplest is a variation on "take-or-pay" where the buyer holds some of the risk when the generator is curtailed, i.e., not dispatched by the system controller. Essentially that means that the buyer is committing to have load available to generate against.

I've also seen renewable PPAs with time of use specified either in volume for purchase, or in the price structure.