Text Box: 1. A 4 blade ground powered wind machine is advertised as having a 150hp engine, and capable of protecting 6 hectares. 2. The 150HP is the maximum power output when the machine is running at 2500RPM. However, the machine only runs at 1800 RPM. 3. At 1800 RPM the power output is just over 100 HP. 4. Now we have to send this power through a clutch, then a right angled gear box, then up 30 odd feet of drive shaft, then through a 96 degree top box with a rotation worm drive. 5. At the prop shaft we have about 70 HP available to spin the fan. The fan is around 5meters in diameter. This length on its own and the fact that it is un-shrouded (an open fan) creates an enormous amount of drag consuming nearly all the HP left over before giving any airflow for frost protection. Just imagine that each blade had a horse tail tied to it. That’s a lot of drag. 6. The fan on a traditional ground powered wind machine then blows the air from the fan back over the tower of the machine, disrupting the air’s momentum, and creating a distinctive “dead” spot. 7. It is possible that the amount of energy left for actually generating air for frost protection is only a small amount of HP. Because the fan is an open style, not only is air lost off the tips of the blades, the noise generated from the blades has become a recognised environmental hazard, rendering these machines inoperable in a lot of regions where horticulture is situated near residential areas. The rotation gear box at the top of the tower cannot be set to oscillate; it must perform a full rotation. In frost conditions, there is always a drift/ drain of air in a particular direction. We call this the katabatic drift. When a wind machine blows against this drift (which it must if it is rotating through 360 degrees) its effectiveness is reduced to about 25% of its capability for that portion of the rotation. Ground powered wind machines generally require trees or vines to be permanently removed for installation and access. They require expensive permanent foundations (12 tonne), resource consents and building permits. 11. They require very expensive service using specialty service equipment (crane/ bucket truck), and spare parts are only able to be sourced from the original manufacturer. Text Box: The Inefficiencies of a Traditional Ground Power Wind Machine Text Box: Portable Frost Protection