To what extent can European-wide power transmission balance overproduction and deficits of intermittent energy sources? Engineers and mathematicians from Germany and Denmark did the math.

The European Union has set the target to reduce CO2 emissions by 80% in 2050. To reach that goal fossil fuel fired power plants need to be phased out and replaced by renewable energy sources. The intermittent nature of Europe's most prolific renewables wind and solar presents the challenge of grid integration while maintaining energy security.

There are different approaches to mitigating the unreliability of fluctuating sources such as energy storage and demand side management. These methods have in common that they shift load or generation in time to reduce the mismatch between the two.

A team of engineers and mathematicians took a different approach and looked into the spatial distribution of energy over large areas to balance supply and demand in the European Union. For instance, on a cloudy windy day the surplus of German offshore wind farms could be offloaded to solar dependent regions and when weather conditions change energy can flow the other way. They calculated the reduction of overall shortages if electricity could be shared unrestrictedly across the European transmission network.

In their paper What Can Transmission Do For A Fully Renewable Europe? Sarah Becker and four colleagues from Frankfurt University, Germany and Aarhus University, Denmark posit the hypothetical case of an European electricity system which is supplied by 100% renewables in 2050.

When the network is optimized for sharing transmission alone can reduce shortages by 40%. The remaining 60% must be mitigated by other measures such as storage and smart grid technologies. To attain the 40% target the network must be enforced over time. The transmission lines must quadruple in number by 2050 compared to today. That sounds like a lot but is actually comparable to the build-up that took place in the last decade.

The study shows that a significant part of the mismatch between electricity demand and intermittent energy supply can be reduced by improved connectivity and unrestricted sharing.