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Designing small generators

  1. May 21, 2013 #1

    I have a decent background in generators and my brother had an idea for building one he wants me to help him out. Without getting into specifics, it would be a natural energy generator integrated into his home electrical system. I have run into some issues though as i am more familiar with shipboard generating and electricity than household electricity. and as far as designing generators goes i have no experience. i have decided to go with a permenent magnet synchronous generator. my more simple questions are as follows:
    what is the best way to incorporate small amounts of generated power into a household electrical system?
    are lagging or leading power factors going to have an affect on the equipment powered?
    is one capacitor per phase the only way to store this ac power?
    how do i maintain the output frequency at around 60hz if the input from nature is variable?
    the permanent magnet rotor will be small, maybe 3 inches, how much voltage can i realistically expect to generate?
    sorry for the length and i appreciate any help i can get, i doubt anyone has all the answers but if you have experience with this sort of thing please let me know
  2. jcsd
  3. May 28, 2013 #2
    Hell Evan - Welcome, this type of question comes up a lot, and there are many factors. But in general the generator probably will need to be rectified to DC, then use an inverter to convert to a consistent 60Hz. To tie this directly to the household's main supply is quite dangerous, there are Backup - Battery supplied "Grid Tie Inverters" that will handle most of the work for you. The 3" rotor - does not tell us much, and we are looking to generate Power, not just voltage.
  4. May 28, 2013 #3
    Thanks! That helps a lot I hadn't ever heard of it. When my brother asked I had no idea what to say really the only thing I could think of was like an ABT but it seemed like way too much work. When I say 3" I mean in diameter, we havent really worked out the specifics yet I was just trying to get an idea of what I would be working with. And I understand I'm dealing with power just I just won't know the resistance until I get further into planning so I was hoping to get a ballpark on voltage. Your answer did help a lot though I have more of an idea of where to start
  5. May 29, 2013 #4


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    "Energy Harvesting" is a very popular subject these days and it has only a worthwhile application where there is a lot of available energy and a very small load. The oldest energy harvesting system in the book is the automatic wristwatch, I would say. If you want to use the sound in your home as a source, then forget it. If you want to use the variation in temperature around your house, then forget it. If you want to use the movement of your body then you will get very tired very quickly if you even want to keep your house lit from your own muscles.
    You have to ask yourself just how much 'available' energy there is knocking around in our lives. If you want to generate it from the movement of electrically driven devices then you would be better off making them ore efficient in the first place. We had to develop some very sophisticated senses to detect the sound and light around us - so that can tell you there isn't a lot of power - except, of course, for the energy that comes directly from the Sun and that is a seriously worth while proposition, as we all know.

    If you have ideas of hooking into the grid then you would need to be an accredited engineer and to use a device that is already 'approved' for the purpose. Plus, as has been said before, you could hurt yourself if you tried it unofficially.

    You could say that energy harvesting is a bit like expecting to pay your weekly household bills, using the spare change down the back of the sofa.
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