Deep Decarbonization and the Supergrid – Prospects for Electricity Transmission between Europe and China

Abstract

Long distance transmission within continents has been shown to be one of the most important variation management strategies in renewable energy systems, where allowing for transmission expansion will reduce system cost by around 20%. In this paper, we test whether the system cost further decreases when transmission is extended to intercontinental connections. We analyze a Eurasian interconnection between China, Mid-Asia and Europe, using a capacity expansion model with hourly time resolution. The model is constrained by an increasingly tighter global cap on CO2 emissions in order to investigate the effect of different levels of reliance on variable sources. Our results show that a supergrid option decreases total system cost by a maximum of 5%, compared to continental grid integration. This maximum effect is achieved when (i) the generation is constrained to be made up almost entirely by renewables, (ii) the land available for VRE farms is relatively limited and the demand is relatively high and (iii) the cost for solar PV and storage is high. The importance of these two factors is explained by that a super grid allows for harnessing of remote wind-, solar-and hydro resources as well as management of variations, both of which are consequential only in cases where dispatchable resources are limited or very costly. As for the importance of the cost for storage, it represents a competing variation management option, and when it has low cost, it substitutes part of the role of the supergrid, which is to manage variations through long-distance trade. The cost decrease from a Eurasian supergrid was found to be between 0% and 5%, compared to the cost in the case of continental-scale grids. We conclude that the benefits of a supergrid from a techno-economic perspective are in most cases negligible, or modest at best.