Green Stack: Wind

Unknown to many, wind is actually a form of solar energy. Wind is caused by not only the varying contours of the Earth but also from the infared radiation given off by the Sun and Earth. Air in different locations across the Earth are heated differently due to these factors. This leads to areas of colder and thus more dense air pockets, as well as less dense and warmer areas. The air flows from areas of higher pressure to low pressure, and is directed differently due to the  varying pressures as well as other factors mentioned. This wind can be harvested into energy through the use of wind turbines. The kinetic energy in the wind is converted into electricity as the wind turns the blades of a turbine, powering an electric generator. This power is considered a renewable energy source because wind is an infinite power source (it will never run out). As with all energy sources however, it has its drawbacks. One such drawback is that they are often best placed in remote locations away from cities and other areas with high energy demand. Another disadvantage is the initial investments to create a wind turbine farm are considerably expensive compared to other energy sources.

To estimate the amount of kWh/day of energy could be created using wind turbines in Hong Kong, the power per Unit Area of Land first needs to be calculated using the equation (pi/400)*pv^3. With an average temperature of 23 degrees C in Hong Kong, the air density is about 1.2 kg*m^-3. The average wind velocity is 3.32 m/s. Inserting these values into the above equation reveals a Power per Unit of Land of 0.34 W/m^2. The average wind speeds in Hong Kong varies from 0.15 to 6.49 m/s.The Area per person in Hong Kong calculates out to be: 1104 km^2 / 6.9 million people = 160 m^2 per person. The power per person then is 0.34 W/m^2 * 160 m^2 = 54.4 W per person. Multiplying this by 24 hours per day gives 1.3056 kWh/person. Assuming 15% of the land could be used for wind turbines, a total of 0.2 kWh/day of available energy from wind turbines.