New way of planning of the national transmission grid within the Italian context

Abstract

In the next future, the Italian National Electricity Transmission Grid Development Plan (NDP) will be increasingly plastered, with the growing difficulty in building new overhead lines (OHL) useful for the country, due to authorization and economic constraints. The changing of the generation mix and growing demand for carbon-free electricity will require drastic and challenging changes in the infrastructure and topology of the electricity system. Today there is a substantial "asynchrony" between the faster Renewable Energy Sources (RES) transmission grid connection requests and the related permitting process with respect to the authorization and construction procedures of the grid reinforcements. The projects envisaged in the Terna’s NDP 2021 are adequate to contain overgeneration by renewable generation. However, considering the actual development of RES and their territorial distribution as well as the actual development of storage systems (and their regulation), new grid reinforcements that are not yet planned may also be required. Thus, among different alternatives, an HVDC overlay concept has been evaluated as suitable cost-competitive solution for complete decarbonization, a better renewables and territory exploitation and growing electrical demand, through its Net Transfer Capacity increase between bidding zones. Rather than building new AC OHL, the described development strategy contemplates to increase the transmission capacity of existing corridors minimizing local opposition and regulatory obstacles through the DC conversion and multiterminal type projects. Given the strong rise of EU electricity prices, begun during the second half of 2021, the DC layer concept might represent a solution to faster RES integration.