How Do Wind Turbines Work?
Generating electricity from kinetic energy via the wind could well be the next frontier for home electricity generation.
The PV cells on the garage roof have been performing very well, the house is using about 6 more kWh per day than we produce so the next thing we want to look at is wind power.
The house is about 800m off the coast so coastal winds will help but is there enough wind to drive a turbine. We have measured the wind speed here, it averages 7. 5mps which means we are a viable site for the installation of a real wind turbine.
The small turbine we are looking at is from Swan Energy, they have jointly developed it and it’s the first of its kind to be released here. Until now the inverters that allow us to put power back into the grid have been a challenge for turbine manufacturers.
Before we install the wind turbine we need approval from local authorities and our energy provider. In the past one of the problems with wind turbines in residential areas is noise.
Well I’m going to check out an installation and find out just how much noise they make. Well here we are and there is the first installation of the Zephyr and it’s turning very well.
The wind is quite strong here but it’s not making any noise so whatever the wind noise problems are with the larger turbines this one, doesn’t have them. They seem to have corrected or fixed it with the design it’s virtually silent.
The turbine is compact and relatively light, but it has the potential to generate more electricity than the PV cells on our roof. It is precision manufactured from ultra-light material and is perfectly balanced.
Swan’ Energy’s engineers have designed a mast and mounting system that is fixed to the brick section to the front of the house. The fixings are set deep into the wall providing solid support and prevent any movement or vibrations in the strongest winds.
The mast will position the turbine 3m above the roof to take advantage of the wind here. The Zephyr is the first of this kind of turbine in Australia. Swan Energy expect sales to ramp up over the next 12 months as energy conscious home owners and government organisations look for new solutions in renewable energy.
Like photovoltaic cells, electricity generated by the Zephyr is passed through an inverter and then directly into the grid. Even in light winds the blades could self-start to overcome start-up inertia and optimise energy production.
Because the Zephyr is so compact and quiet it’s suitable for any residential area. We believe it will soon become a common sight throughout the suburbs.
Windmills have been assisting mankind to convert the energy contained in wind to many other useful forms for the last two thousand years.
Today’s wind turbines can convert a great amount of energy in the wind into electricity. This is due to the blades which are developed using state-of-the-art aerodynamic analysis and the other performance-enhancing equipment.
In this article, we will explore these different sets of technology in a simple yet scientific way. First, let’s get into its basic working. If the blowing wind can turn the wing, we will receive electricity from the generator that is attached to it.
However, how does the blowing wind turn the wing? Let’s have a close look at the blade. The Blade has a lot of air foil cross-sections consisting of different sizes and shapes from the root to tip.
The simple air foil technology makes the wind turbine blade turn. That means that a lift force is produced when a fluid moves over an air foil. This way the wind turbine achieves the basic rotation we are accustomed to seeing.
Just as in a moving train you experience things relatively, the moving wind turbine blade also experiences the wind relatively. For the moving blade the relative wind velocity is as shown.
Therefore, the wind turbine blade is positioned in a tilted manner to align with the relative wind speed. As the blade velocity increases to the tip the relative wind speed becomes more inclined towards the tip.
This means that a continuous twist is given to the blade from the root to tip. However, this rotation cannot be directly coupled to a generator.
Because the wind turbine blades typically turn at a very low rate of rpm due to the issues of the noise and mechanical strength. Considering this low-speed rotation we cannot produce any meaningful electricity frequency from a generator.
So before connecting to the generator the speed is increased in a gearbox. The gearbox uses a planetary gear set arrangement to achieve the high-speed ratio. A break also sits in the nacelle.
The function of the brake is to arrest wind blade rotation during excessively windy conditions. Consequently the electricity that is passed through the cables towards the base where a step-up transformer is situated.
The wind turbine should face the wind normally for maximum power extraction. But the wind direction can change at any time. A velocity sensor on the top of the nacelle measures the wind speed and direction.
The deviation in the wind’s directions sent to an electronic controller which in turn sends an appropriate signal to the yawing mechanism to correct the error. You can see how the yaw motors turn the nacelle.
Thus, the wind turbine will always be aligned with the wind direction: According to the wind speed the relative velocity angle of the wind also changes. A blade tilting mechanism tilts the blades and guarantees a proper alignment of the blade with the relative velocity.
Thus, the blades are always at the optimum angle of attack with the relative wind flow. Efficiency of the wind turbine is the interesting topic. To gain a good insight into wind turbine efficiency assume that you are measuring wind speed at upstream and downstream over wind turbine.
You can note that the wind speed at the downstream is much smaller than the upstream. This is because the blades absorb some kinetic energy from the wind.
The same amount of energy is converted as mechanical power of the wind turbine. It is interesting to note that a wind turbine absorbs 100 percent of the available kinetic energy only if the downstream wind speech becomes zero.
However, zero wind speed at downstream is a physically impossible condition. This cartoon animation clearly depicts this fact. Zero downstream speed simply means the whole flow is stock. This physical reality of the flow demands a certain amount of exit wind speed.
That means that there is a theoretically maximum efficiency a wind turbine can achieve. This limit is known as Betz’s limit. Essentially it means that no wind turbine in the world can ever cross the efficiency limit of 59. 3 percent.
We hope you have now developed a good inside of the operation of a wind turbine. Thank You!