This 2012 project evaluated temperature changes resulting from wind machine operation for both upward-blowing wind machines and conventional horizontal-blowing machines. Measurements were conducted at dozens of locations in commercial vineyards throughout the counties of Santa Barbara, San Luis Obispo, Sonoma and Mendocino.
The study relied almost entirely on wind machines which had been previously installed by vineyard operations for their own frost protection needs, and which were operated by the cooperators during the study period whenever they felt that frost protection was needed. Instrumentation was installed at 34 wind machines; not all sites experienced frost conditions, but machines were operated sufficiently at 29 of the 34 sites. These included 22 sites with upward-blowing wind machines and seven sites with conventional machines. We compared the observed air temperatures at distances of 15, 30 and 60 m from each wind machine, compared to the predicted temperature values if the wind machines had not been operated.
Overall, the operation of the conventional wind machines showed useful temperature increases which were similar to results from previous studies, while the operation of the upward blowing wind machines had minimal effect on increasing air temperatures. Additional detailed studies were conducted with a medium-sized upward-blowing wind machine at a future vineyard site. Comprehensive temperature measurements were made using 52 sensors surrounding the machine in all directions, over 12 operation nights. Little or no temperature gains were observed from the operation of this machine under the particular conditions of the study.
Improved information on the relative benefits of different types of wind machines and their ability to alter vineyard temperatures is important for vineyard operations that require some form of frost protection. As water supplies for sprinkler frost protection become more limited, there is increasing attention being paid to wind machines as a potential alternative in many areas. This study will provide growers with useful information to help them to make the most informed frost protection decisions possible.