# dissertation help!

#### mwatso32

Joined Jan 5, 2013
5
first time posting here!

i am currently designed a wind turbine to power LED lights on a bicycle for my honours year project!

have not done any electronics since first year, i am not upto to scratch to say the least.

the light will only have one led with the following specs from the website:

Continuous Forward Current: 30
Peak Forward Current: 70mA
Forward Voltage 3.4V
Power Dissapation: 120mW
Total Power Consumption 0.102 Watts

From my power = 0.5 * ∏r^2 * P * V^3 for a 7.5cm diameter blade i got 1.358W.

Does anybody know if this is at all right?

#### WBahn

Joined Mar 31, 2012
26,047
Is what right? The LED specs? The power you should get from the wind turbine you designed?

How can we possibly know the answer to either of these?

Assuming that the forward continuous current is in mA, the total power consumption is consistent with that times the forward voltage. I don't know what the 120mW power dissipation value is referring to. Perhaps maximum rated average dissipation?

As for the power available, we don't now P, we don't know V, and we certainly don't know any other details about a turbine YOU designed.

What degree program is this for?

#### mwatso32

Joined Jan 5, 2013
5
ok i can see why you would think that I am an idiot for writing such a poor question but I was just in a bit of a panic.

I haven't done any electronics/electrical stuff since first year and jumped into it without re-familiarising myself with it.

I realise that nobody could possibly answer my question.

It is for my honours year dissertation studying BEng(Hons) Mechanical Electronic systems engineering at Glasgow Caledonian University.

I was using air density at 1.23 and velocity as 7.5ms

Where I was getting confused was I was trying to work out the voltage that the turbine will produce but I had barely even looked at the permanent magnet system that I will use, the number of coils and strength of magnets etc will determine the voltage?

as you can tell this is not my main area of study ( we mostly do FAE, ProE that sort of computer based stuff) but I chose to do my thesis on this because I want to expand my knowledge base and get a job in the renewable energy sector.

i would appreciate anything you have to say

#### WBahn

Joined Mar 31, 2012
26,047
Lots of factors will determine the voltage you get out, such as the turbine rotational speed and the gearing as well as others.

I'm still at a loss to understand what you are hoping to find out from this forum.

#### mwatso32

Joined Jan 5, 2013
5
jesus man whats with the cold shoulder?

#### WBahn

Joined Mar 31, 2012
26,047
There's no cold shoulder involved. I do not understand what you are trying to learn. Are you looking for someone to confirm that your turbine is going to output 1.358W? How can we possibly do that?

What specific questions are you looking to either get answered or get guidance on how to answer them? Just saying that you would appreciate anything that anyone has to say is not at all helpful.

#### mwatso32

Joined Jan 5, 2013
5
this is my first experience using forums & i was just looking for some general input, i thought people just chatted etc

#### WBahn

Joined Mar 31, 2012
26,047
Well, if you just want random chat, then you are not very likely to get any input that is of help to you. Most people on most forums want to engage in a discussion that has some focus or sense of direction. That focus and direction generally comes form the starter of a given thread, though it often begins drifting from there and sometimes the OP needs to pull the discussion back to where they want the discussion to go. But who knows, maybe you'll get lucky.

#### mwatso32

Joined Jan 5, 2013
5
I see, ok I shall take that on board thanks.

I will return in a few weeks once I am much better equipped with the knowledge to word the questions properly.

#### WBahn

Joined Mar 31, 2012
26,047
Sounds good. See you then. Remember, the more details you can provide, the better the responses will probably be.

#### thatoneguy

Joined Feb 19, 2009
6,359
A good "back of napkin" for your idea would be assuming something around 20-30% efficiency for your turbine after mechanical and electrical losses. You may end up better or worse in the final outcome. Present production wind turbines that have a ton of engineering put into them are still only about 40% efficient. (Air power -> electric power)

The power from air moving the blades will see a lot of loss, from the friction of the blades, their shape, bearing friction, linkage to generator, etc. You can experiment, or calculate the losses, but trying to identify and quantify every single point of loss would take a while.