Wind Turbine Blades
Given a specific size (diameter) and shape of a lift-type blade, there are three other variables that have a significant impact on the maximum power output of a wind turbine.
1)The blade angle of attack can either increase (or decrease) the amount of drag that is created as air passes across a turbine blade. The angle of attack is the angle between the chord of the blade and the direction of the air flow (assuming that the air flows approximately parallel to the ground). Basically, with a given wind speed, the higher the attack angle, the greater the lift–up to a certain extent. Also, at higher wind speeds, a lower angle of attack will produce the same lift as a higher angle of attack at lesser speeds. On a rotating propeller, air moves faster towards the tip of a propeller blade. Therefore, the angle of attack of the blade can be lessened towards the tip of the blade. This is the reason why some propeller blades have a slightly twisted shape. Less sophisticated blades do not have this twist and are merely set at a fixed angle (or “pitch”) with respect to the plane of rotation. (Whether “twisted” or not, most blades still have varying blade widths and curvatures across the length of each blade.)
2)The weight of the propeller assembly (hub and blades) affects the rotational speed of the blade at a given wind speed. Lighter propellers are easier to turn (by slower moving wind) but once the wind stops blowing, the lighter propellers loose their speed faster than the heavier propellers (the effect of momentum). Propeller weight depends upon the material from which it was made and from the inner structure of the blades and hub. Also, denser (and heavier) propellers are generally less prone to flexing and bending, which wastes the energy of the wind. Newer blades are light but stiff enough to resist flexing.
3)The number of the blades: generally, the more the blades, the greater the surface area that is present to “catch” the wind. But the trade-off with more blades is that they need to be bunched closer together which results in putting each blade closer to the backwash of the preceding blade. Propellers with more blades (>3 or more) are applicable when wind speeds are low. These propellers are efficient at low speeds and turn more slowly but because of the greater surface area that catches the wind, these propellers also deliver more torque.
There are other variables that impact on blade performance. Additional information is available on my website.
How To Live Off The Grid And Say Goodbye To Utility Bills
Every day more and more people are coming to realize that they can still enjoy all the things that modern life can offer and still maintain independence and an off the grid lifestyle. When we talk about how to live off the grid, were talking about complete independence from third party sources for your energy supply. Basically supplying your own energy.
No more electricity bills.
No more being at the mercy of on grid utility suppliers.
No more rising costs to your bills every year.
You will be doing your bit for the environment too.
Anybody who owns a home will benefit.
People are now becoming more and more aware of the benefits that living off the grid can bring to the modern world. Wind power turbines and solar panels are the popular choices for home owners now. The need for breaking away from the use of fossil fuels and the harm that the use of these fuels can do to the environment is a big issue that should not be ignored.
Only a few years ago, installing solar and wind power systems in the home was so expensive that it just wasn’t a viable option for the average home owner. Times have changed, and these systems have become far more affordable. There are now even DIY systems that you can install for a very low price indeed.
For those who choose to make the switch, they can rest assured that as time passes by they will have full control of their energy costs, whilst others on the grid will have to face big yearly cost increases.
Some people may be thinking that living off the grid will mean that they will have to give up on using their power hungry electric equipment, and all their gadgets and gizmos. This simply is not true. You just simply have to moderate the use of how you use the electricity in your home. This can mean switching off lights when you are not really using them, in other rooms for example.
You can purchase electric equipment that does not use electricity when you’re not using them, such as microwave ovens and electric stoves. You can unplug things when you are not using them and stop putting televisions, hi-fi’s and DVD players into standby mode. That will waste more electricity than you realize. Going off grid doesn’t mean you have to give up anything. You just have to think smarter.
Learning how to live off the grid is now becoming so popular that within a few short years a large percentage of people with be happily relying on producing their own power and not depending on the utility companies anymore. The home system kits are by no means ugly things either. They are very compact and streamlined in design. They will serve you well for many years to come.
