Foiling - the Future or a Folly

[robherc]

I don't think I even remember what "light wind" is since I've been living here in El Paso for so long...if we go a week without the wind speed topping 30mph, somebody must've stolen the weathervane...because that just DOESN'T happen here (I live almost within throwing distance of a ridge of 1500ft "mountains"...and my house is at almost 4000' elevation).
I'll probably try to install some form of CVT for it though, if I have any problems.

[Rick Willoughby]

Rob
The limits that you need to work within for the PMDC Mars motor are 100A rated current and 70rpm per volt.

If you want to get 5kW from it with the 100A limit you need to produce 50V. That means spinning it at 3500rpm. If you are using an open bladed turbine it will be spinning much slower than this so you will need to gear up. This will make the cogging even more pronounced. You may need some smarts in the system to automatically motor it if the wind drops and then kicks back up.

I have not gone into a lot of detail on the Kelly controller other than using it as a motor controller. It is intended for vehicle use so the regen function is used like a brake with separate control input. From memory the level of braking is adjustable so you need smarts to optimise power output at any given wind speed.

There is a larger Mars motor but it has brushes and I wanted to avoid these.

I am impressed with the motor and controller. The connection diagram provided was wrong but once past this it all worked well. The motors are quite impressive. I can see why they get a lot of positive comment.

Rick W

[robherc]

Yes, I'm still working with a ducted design. Probably using 0.3m blades spinning in 2 1m counter-rotating discs & sucking air from a 1.8m diameter section of aerial real-estate. Do you think that will be roughly adequate for harvesting 5KW off of the 20-25mph winds, and still giving me something >1KW from the 10-15mph breezes (or do I need to scale down to avoid burning up my equipment)?
Oh yes, we're talking land-based here...I'm working for max energy extraction per $, not low-drag, or low-weight application.

[Rick Willoughby]

Do the power numbers for the air flow. I think you will find it is about 2kW at 25mph. Even with very good recovery beating Betz limit with the ducting you will need at least 3m diameter at 25mph.

Have a look at the size of unducted to get 5kW. You will need an intake area not a lot smaller than this. This will give you an idea:
http://www.aerogenesis.com.au/5kW_turbine.html

Rick W