NTPC Green Energy (NGEL), a wholly-owned subsidiary of NTPC, has invited bids for the appointment of a consultant and the hiring of a designated operational entity (DOE) for the validation and verification of a 50 MW solar project in Rajgarh, Rajasthan, up to December 31, 2020, and renewal of the project for an additional seven years to continue receiving clean development mechanism (CDM) benefits and carbon credits.