Lecture 4 Review

Lecture 4's focus was wind power. An inherent advantage of wind power was highlighted straight away in that it is direct in it's power generation. The wind pushes the turbines round, which are directly coupled to the generator, contrary to fossil fuel and nucleur (i.e. no intermediate burning, steam generation and turnbine is needed). Another interesting fact is that around 100 times more energy is converted to wind than is converted to biomass by plants. These are some of the reasons why wind is among the fastest growing sources of energy.


Historically wind power was used in the form of windmills, which performed such tasks as grinding crops. The basic idea has not changed, only now the blades of the turbine drive a generator. Currently a wind turbine can generate up to 5 MW of electricity, at a cost of about 5 cents/kiloWatt-hour. Denmark is the biggest wind power user, with over 20% of it's energy production coming from wind farms. This makes it a clear leader in wind power usage, however many countries plan to expand their renewable energy usage through wind power.

In the United States, less than 1% of the electricity generated is from wind, with the leading state being Texas, generating over 4 MW. However with the decreasing costs involved, and and increase in the power capacities of turbines, predictions for 2020 state that 6% of US energy could be through wind power. There is a maximum efficiency of a wind turbine of about 60%, due to Betz's Law, and it is impossible to exceed this.
 

Wind power technology has moved from drag type devices which had many blades, to lift devices, which have only a few blades, which are designed in a similar way to airplane wings.  The turbine can either have a horizontal axis or a vertical axis. With a vertical axis, you do not need a yaw mechanism to turn the rotor into the wind. However the turbine does need a motor to start moving. The Horizontal axis is the more conventional design which is used in the majority of cases. They typically have two or three blades, and do not require a motor in the turbine. A downside is that they do generate more noise. The different available technologies, along with the components that make up a horizontal axis wind turbine, were covered in some details.

Some cases brought against wind power are that it is noisy, kills birds and requires too much land. These arguments can be seen to be weak, as the noise is non mechanical, and it is possible to have a conversation above it at they base of the turbine without difficulty. Wind turbines are currently only responsible for 0.003% of bird deaths in the US, and they land that they require can also be used for other things as they take up very little space on it.