Inflatable wind turbine project

[Bigdavevw]

Hi guys, I have just joined the forum but have been watching Dave's videos for a couple of years.

Right, I am studying a bachelors degree in electrical power engineering and have a group project to design for a class called integrated engineering studies 

So my group and I have decided on an inflatable wind turbine based on the Altaeros BAT but on a smaller scale.

http://www.altaerosenergies.com/


We are planning on using this generator (167V) http://www.energistar.com/wind.html for its lightweight design, low cut in speed and efficiency.


The plan with the turbine is to tether it to the ground in three places and send it up around 30m into smooth, laminar wind. The three phase from the generator will be rectified on the turbine and sent down 2.5mm squared copper cables as DC.


The turbine will be used to charge a 115Ah SLA leisure battery as well as run items directly from an inverter.


The main issue I'm facing at the moment is controlling the speed in high winds. We initially thought about dumping the load but this would cause overheating of the windings would it not?

As the turbine is essentially a floating ducted fan, we thought about pulling the back of the turbine body down at the rear tether point via a winch to decrease the wind flow through it but I don't really know how to control this!

I'm guessing that the voltage will keep rising the faster it spins and therefore a control circuit could be designed to winch the back end down when the voltage goes above a certain value?


Any help with this would be great! I'll try and get some pics up to explain what I mean as they will give a good idea of what I'm after!

Dave

[CatalinaWOW]

You could always follow Alteros lead and ground the aerostat in high winds.  Your approach of tilting the turbine to reduce flow is conceptually sound, but will require lots of design work.  Remember you are increasing angle of attack in a flow field, and therefore generating lift and increasing drag.  Your tether system and the structure of your turbine will have to deal with both.  Stability will also change.  For a senior design project I would make a valiant attempt at working through the tilting solution and then fall back on grounding the system.  You can always claim a small victory by "extending" the operating regime with a few degrees of tilt, even if you are only buying a couple mph of acceptable wind speed.

[Smokey]

...
We initially thought about dumping the load but this would cause overheating of the windings would it not?
...

Figure out the continuous power rating and max operating temp of the motor (from the data sheet hopefully) and see if you are exceeding it with the leads shorted with worst case wind load.  On the up side, the condition exists in high winds so you should have about optimal cooling at that time.

[DenzilPenberthy]

Have you considered using aluminium wire rather than copper? Presumably you want to reduce weight as much as possible..

I wonder if it would be worth either rewinding the alternator to produce a higher output voltage or having a system on the alternator (either an ac system or a DC-DC converter)to increase the voltage before sending it down to the ground.

Anyway, dumping excess power into a resistor is the usual way of controlling overspeed in wind turbines like this.

[LabSpokane]

What problem are you trying to solve with this project?  This is a serious question.  What comparisons have you made with this solution versus others that make tethering a ballon the optimal solution?