Wind machines are tall, fixed-in-place engine-driven fans that pull warm air down from high above ground during strong temperature inversions, raising air temperatures around cold-sensitive crops such as grapes and tender tree fruits.
They are different from wind turbines which are designed to create electricity from wind energy.
In Ontario, wind machines are primarily used to protect grapes. Although grape growers are planting more cold-susceptible cultivars than in past, due to market pressures as there is little demand for more cold tolerant cultivars. There are three critical times growers need to protect crops against cold injury:
Spring's late frosts (early growing season), autumn’s early frosts (late growing season), winter’s very cold temps (dormant season)
Significant spring damage or early frost damage are not that common for grapes or tender tree fruits in Ontario, approx. 1 year in 10 in Ontario. However, the winters of 2003, 2004 and 2005 all had sufficiently cold temperatures resulting in observed vine and tender tree fruit bud injury. Grape yields in Niagara in 2005 were about half the normal. Wind machines proved beneficial. Growers with machines harvested near normal crops in 2005. Those growers nearby without machines experienced total crop failures.
Wind machines help protect crops from cold-injury which can affect the following year's crop as well as long-term plant health. Wind machines cost $30,000-$50,000 CDN to install, including the concrete base, and then $30-$50/h to run using propane, diesel, gas, or natural gas as fuel. While the blades spin, the head of the fan rotates around the tower's vertical axis. Air is circulated north then east, south, west, then back where it started 5 minutes earlier. Air flows in all directions over time, covering at least 4 hectares(10 ac) Most growers decide to operate wind machines by monitoring air temperatures about 0.6 m (2 ft) above ground compared to air temperatures as high as 20 m (66 ft) in the air.
Wind machines need large engines operating at high RPM, and long pitched blades to blow a lot of air a long distance. Some people do not like wind machine sound. They describe it like a helicopter.
The region’s temperatures are influenced by the Niagara Escarpment and Lake Ontario, which acts as a hot water bottle in winter — raising winter temperatures on land from its summer-warmed waters. In spring, breezes from its winter-cooled waters help to hold back the development of fruit buds until the danger of late spring frosts have passed. Lake Ontario also cools the summer air so that grapes do not ripen too quickly, and then keeps the fall air comparatively warm so that the first frost is delayed, thus extending the growing season. Most of Ontario’s wineries are located in the Niagara Peninsula.