With and equity bridge loan, a lender allows the sponsor of the project to borrow the amount of equity invested in the project. The loan can be paid at commercial operation or even later.
This page describes the mechanics of equity bridge loans and how they can be incorporated into a financial model. I also discuss the theory of an equity bridge loan the should come along with a parent gurantee. The question is whether the benefit in terms of a higher equity IRR for the project should be attributed to the project. One could argue that the EBL is outside of the project and any increase in IRR that comes from the EBL only arises from a parent gurantee. Futher, at least in theory, this use of a guarantee comes along with a cost.
The video below describes modelling of an equity bridge loan in the context of a Brazilian wind farm financed by BNDES.