The Renewable Energy Forecasts from Observations and high-Resolution Modeling (REFORM) project

Renewable energy from resources like the wind and sun comprise a gradually increasing share of the energy mix. Since these resources are fluctuating, forecasts for renewable energy sources are crucial for an efficient operation of the power system. For a large part, forecasting of renewable energy production relies on the output from numerical weather prediction (NWP) models. NWP models operate at coarse mesh sizes that cannot resolve turbulence, which is one of the key processes affecting wind and clouds alike. This leads to systematic biases, most notably an overestimation of solar radiation in the presence of low (stratus) clouds, and a severe underestimation of the wind speed during the night. Both situations are frequently occuring weather conditions.Large-eddy simulation (LES) models apply a high spatial resolution (~10-100m) which is sufficiently fine to resolve turbulence. LES modeling is an established, yet computationally expensive technique. Recently a giant gain in the computational speed was obtained by running LES on a GPU (Graphics Processing Unit), which nowadays allows the TU Delft spin-off company Whiffle to operate it as a high-resolution weather forecast model. The GPUResident Atmospheric Simulation Platform (GRASP) receives the large-scale forcing conditions from the European Weather European Centre for Medium-Range Weather Forecasts (ECWMF) model. The full potential of LES-based forecasts is however not acquired since the initial state, which is also taken from the ECMWF model, contains errors.With REFORM, we aim to improve weather forecasts of solar radiation and wind by introducing a novel, hybrid approach which makes use of GRASP as well as observations to obtain the best possible estimate of the initial atmospheric state in terms of wind, temperature, humidity and clouds. We will capitilize on the recently initiated national observational platform Ruisdael, which includes ground-based in-situ measurements as well as advanced remote sensing retrievals. To fully exploit the capabilities of GRASP the proposed research will strongly focus on turbulent regimes such as the nocturnal stable boundary layer, the clear convective boundary layer, their transitions, and low clouds.