Optimizing capacity extensions in power systems: A case study of Bavaria and a comparison to Texas

As the German Energiewende policy enters the latter stages of its goal to dismantle the country's nuclear power plant fleet, the southern state of Bavaria must decide how it will replace its nuclear generation capacity. This study extends a renewable capacity expansion model that was initially developed to find optimal extensions of wind and solar generation and transmission for Texas, United States. Here, additional options for the development of the Bavarian electricity supply are added: combined-heat-and-power (CHP), improving transmission connections to the non-Bavarian German generator fleet, and constructing new natural gas combined cycle (CCGT) power plants within Bavaria. The model's solution suggests that an optimal mix includes 3.5 GW of transmission to the non-Bavarian generator fleet, 6.0 to 9.5 GW of new CCGT capacity, and 8.5 to 10.0 GW of transmission capacity to the on-shore wind resources of the Schleswig-Holstein state in northern Germany, depending on the CO
₂
price. Compared to the model results for Texas, Bavaria's system is less sensitive to a CO
₂
price in both the optimal system configuration and the resulting emissions. While Texas emissions can be reduced by 55% with a CO
₂
price increase from 10 to 100 $/ton, the reduction in Bavaria is only 28% with a price increase from 0 to 100 EUR/ton.