Terra Clean (TeCL), a wholly owned subsidiary of Indian Oil Corporation (IOCL), has invited bids for the empanelment of engineering, procurement, and construction (EPC) contractors for the design, engineering, supply, construction, installation, and commissioning of balance of system (BoS) and balance of plant (BoP) toward setting up interstate transmission system (ISTS) and intrastate transmission system (InSTS)-connected solar power projects.