Existing Designs
Most common applications of wind turbines, used in either rural or commercial applications are based upon the horizontal axis design, seen in the image below.
Exploded view of typical horizontal-axis wind turbine. (Click to enlarge) - Source Wikipedia
The turbine consists of normally 3 blades (but can have more) and they spin upon a shaft which drives an alternator or electrical motor which is outputted into storage batteries. (This is a very general description). To account for wind direction, the turbine must employ the use of a wind vane, which attaches to the rear end of the turbine and will rotate the unit until it is facing opposite to the wind stream. However, this method does have drawbacks - specifically the often long delay before the unit is appropriately positioned and the inherent difficulties with maximizing wind usage from variable directions.
Our solution, was to use a vertical axis design. Using a vertical axis wind turbine, blades are always in-line with the wind and therefore do not encounter issues when wind direction is changing. Due to its design, blades will be either "catching" the wind and spinning the unit, or "cutting" the wind as it completes a rotation. The figure below is one such example of a common vertical axis design.
Vertical Axis Wind Turbine. Source DIYTrade.com
In general, there are two main categories of vertical axis wind turbines (VAWT) - the Savonius and Darrieus models. Each has its own unique design features, and there own drawbacks. The Darrieus model features long curved blades which use airfoil design in order to capture the wind to convert it into mechanical energy. However, as seen in the picture below, large guide wires are needed in order to keep the structure upright, therefore the unit itself has an extremely large footprint - not useful for residential applications.
Darrieus Model VAWT. Note large guide wires. Source Wikipedia
The Savonius model can be easily described as a cylinder halved, and each half is offset in the opposite direction an equal distance. These halves rotate around a center shaft, and the resultant rotation is converted to mechanical energy. The image below depicts how the wind is captured in the Savonius model, and converts wind energy into rotation. Note the unique transfer of wind from one blade to the other around the center shaft.
Darrius Model VAWT (Top View). Source Wikipedia.
Wind Speed and Direction
Our initial concepts were based on previous research, completed to gain an understanding of the environmental issues attributed to Urban/Residential areas. Wind paths, diagrams and average wind speed were all measured for the Hoboken, NJ metro area and further concepts were modeled around these statistics. Statistics for the nearest major city were used - Newark, NJ.
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Average Wind Speed diagram in meters per second |
These figures provided the team with a baseline for what to expect in the NJ/NYC metro area. This enables the team to conclude what should be identified as an estimated Wind Startup Speed - the point at which the blades begin rotation and produce energy. This information proved extremely valuable when choosing the electrical and drive components.
Further reinforcement for the production of wind turbines in the NYC metro area can be seen below.
Wind Resource Potential for United States (Click to Enlarge) - Source Wikipedia
