Optimizing frost protection in vineyards through numerical simulations of wind machines and heating systems

Abstract

Spring frosts pose a significant threat to viticulture by damaging buds and, in severe cases, leading to their destruction. Climate change has exacerbated this issue by advancing phenological stages, making plants more vulnerable to prolonged frost events and increasing agronomic losses, yield reduction, and economic impacts on the wine industry.

In the Centre-Val de Loire region, winegrowers are increasingly adopting wind machines – fans mounted on masts that mix warmer air from upper layers with cold ground air, raising the temperature around the vines by a few degrees. Traditional frost-mitigation methods such as heaters and candles are still used, locally diffusing heat in vulnerable areas to safeguard the buds.

While scientific literature has primarily focused on field observations of the combined use of wind machines and heating systems, applying numerical simulation to this context is innovative. Field datasets on frost events are spatially sparse and limited in number, as frost occurrences are infrequent and depend on specific meteorological and topographic conditions. In contrast, numerical simulations allow dense, parametric exploration of frost scenarios, enabling systematic assessment across a wide range of configurations.

Large Eddy Simulation (LES) models, such as the open-source PALM model, offer advanced capabilities for studying the Atmospheric Boundary Layer (ABL). The PALM model, which includes a module based on actuator disk theory, has been adapted to simulate the airflow from wind machines in nocturnal stable ABL flows. Calibrated with field measurements, the model accurately reproduces the flow at vine height and the thermal signature of the jet during each tower rotation.

Findings from the European Innovation Partnership (EIP) SICTAG project (2019–2024) have raised two key questions :

• How can heating devices be strategically placed around a wind machine, considering topography and frost severity, to enhance efficiency and reduce environmental impact ?
• Does the continuous airflow from the wind machine create a crosswind strong enough to maintain generated heat at bud height ?

Exploring these questions paves the way for sustainable frost-protection strategies. This research is part of the EIP OPTITAG project (2025–2028), which aims to optimize wind machine use through a multidisciplinary approach integrating agronomy, aerodynamics, acoustics, sociology, and economics.

The model will incorporate topographic and ABL data for realistic frost-event simulations. A dedicated module will reproduce the thermal plume from heat sources, and sensitivity analyses on key parameters will guide the development of efficient combined protection strategies under varying frost conditions.