  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.17
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