Posters

Abstract

Germany plans to install ~200 GW of onshore wind capacity by 2050, in line with its Net-Zero ambition. Its technical potential or the expected annual electrical yield is expressed as a capacity factor, or the ratio of the deployment's actual electrical output to its installed capacity. This large-scale capacity factor includes effects of wind speed, turbine characteristics, and array efficiency losses. Its estimates vary over a narrow range of 25 - 28% for the 9 to 24 MW km-2 of proposed capacity density over onshore Germany by 2050. It is implicitly assumed that these estimates are independent of regional wind resource depletion. However, they reduce because turbines extract kinetic energy (KE) to generate electricity, resulting in a slowing of regional winds. This raises a question about what the relationship between large-scale capacity factors and proposed capacity density over Germany is? This is important because capacity factors are an important control on the deployment costs. Here, we establish the link between large-scale capacity factors that include the effects of regional wind resource depletion and proposed capacity densities over onshore Germany. Further, we evaluate the role of KE removal in shaping this relationship. Therefore, we simulate the atmospheric circulation and yields for a range of deployment scenarios over onshore Germany using the Weather Research and Forecasting (WRF) model and a simple momentum - balance approach (vKE). Over the range of scenarios, regional mean wind speeds reduce by up to 10% and capacity factors by up to 30%. Despite potential wind speeds biases, regional wind speeds reduce by an average of 0.4 m s-1, relative to the case where resource depletion impacts are excluded, for the planned scenario of ~200 GW deployed over 13.8% of land. Similarly, large-scale capacity factors reduce, on average, from ~40 to ~30%. We isolate the impact of KE removal by comparing WRF and vKE estimates. The former includes all effects of regional wind resource depletion while the latter only includes KE removal effects. We find that the KE removal effects play the dominant role in shaping the reductions in wind speeds and capacity factors, thus providing a simple tool to capture these effects at the national scale. We conclude that with increased deployment of wind energy in the context of the energy transition, regional wind resource depletion effects need to be accounted in energy scenarios. However, this can be done in a comparatively simple and physical way.