This diary will cover quite a span and will be posted in installments. I'm not going to cover the complete machine design in this diary, but focus on the alternator because I believe I have some useful things to offer.
After discovering this site around the beginning of the year, I've been a frequent visitor to learn as much as I can about the axial flux alternator. I hadn't been aware of this configuration previously, even being involved with RE for 30 years (guess I didn't keep up).
It appears that Hugh Piggott has done us a huge favor by developing this configuration into a practical DIY design. Further work, by others notably DanB, have brought the design to a fairly high level and it's often recommended that his work be emulated. The advent of neodymium magnets made it all practical, of course.
Further reading showed some problems still remained to be reckoned with. There seemed to be a fairly high failure rate among machines as shown by a recent poll, which indicated about 23%. Whether due to design, execution or whims of the gods can't be determined.
Being located on a small island (American Samoa) in the middle of the Pacific, presents its own set of problems, particularly in obtaining materials to work with. Also, services available elsewhere, such as water-jet and laser cutting are non-existent here. The cost for shipping these in from elsewhere is very expensive. One rotor disk might cost US$100, just for shipping. Clearly, some design changes were necessary to allow building a practical machine.
Problems I saw that needed attention were:
Low alternator efficiency with the attendant stator heating problems
Stator cooling
The whole resin-casting bit, magnet rotors and stator
Excessive alternator weight
Practical magnet selection
Coil design
Choice of materials
Testing procedures.
The basic design objectives are:
To produce one kilowatt in a 12 volt battery charging system at 16 mph wind speed (my site energy peak) at an efficiency of =>75% with my existing 16 foot, variable pitch air rotor.
To have NO stator overheat (failure) issues at the 25 mph feathering point (>3 kW) (not furling, this is a variable pitch, down-wind machine, but about the same as).
NO resin casting
An alternator weight of <150 lb
Minimal magnet cost
Locally available materials, mostly
.
Now, some of this may seem like fantasy to some of you, but I believe I've done the homework to show the feasibility. I'll report success or failure along the road.
The next installment will report on coils since I believe that the actual coil winding results impact the physical design of the rest of the alternator. First, it was necessary to design a special motorized winding jig to achieve the results I wanted. The bits and pieces for the jig are on the way as well as 56 lb of #14 Square Hi-Temp wire. As a teaser, the 12 coils are 13, single layer turns of 7-in-hand #14 square wire, well bonded.
Until next time.