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Can renewable energy be stored?

  1. Sep 15, 2015 #1
    HI!
    I am wondering if electricity generated from a friction driven turbine by winding for example can actually be stored in a battery for later consumption?
    Best Regards
     
  2. jcsd
  3. Sep 15, 2015 #2

    DEvens

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    Hello Setor2y. Welcome to the forum.

    Yes it can. However, at this time, it is rather expensive.

    https://en.m.wikipedia.org/wiki/Tesla_Model_S#Battery

    So a 60 kWhr model costs about $10,000, and lasts about 8 years under use as expected in a car, something in the range of 500 charges. This means the battery cost alone is significantly more than electricity costs currently. Typically you can buy electricity for something less than $100 per MWhr. This battery would add something like $300 per MWhr to that cost.

    Wind is already typically more expensive than other forms of electrical generation, often coming in at above $150 to $200 per MWhr. So battery backed up wind is likely to be over $500 per MWhr. Coal, meanwhile, is typically somewhere around $60 MWhr. or even less if you are prepared to burn the cheaper, dirtier coal. This is why lots of places still burn coal for electricity.
     
  4. Sep 15, 2015 #3
    Thanks a lot DEvens. Your reply was much appreciated and very helpful.
    Again i was wondering, having a bicycle dynamo for example.
    Shouldn't it be possible to have such electromagnetic inductor like a dynamo attached to a rear tire of a car to generate electricity to be transferred to a detachable device with a battery which can store the current for later use? To power at a least home appliances like computers and tv's.
    Taking this image i uploaded for example, detaching the dynamo from the torch and building a device which can be installed on a car to charge a battery.
     

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  5. Sep 15, 2015 #4

    DEvens

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    Again, sure. But it would be expensive. You can buy various devices of this kind on Amazon or various other retailers. The foot-crank thing you posted a picture of is about $300. Also, you may be disappointed about the amount of physical effort required to power even small devices. An iPad mini uses 10 Watts. The device you posted a picture of runs somewhere in the range of 50 Watts to 100 Watts. So a single fairly modest (with respect to power-use) device is going to use a substantial portion of your ability to crank things. Possibly it is acceptable, even a life saver, in an emergency when the grid power is off. But it won't be enough to do anything substantial like heat a room or cook food.

    Hand cranked devices are a bit cheaper, and lighter. But they wind up being a lot smaller in power output. For example, a typical hand-cranked thing requires you to crank for 2 minutes to make a 1 minute phone call. Again, maybe a life saver in a power failure. But that is probably the only real application.
     
  6. Sep 15, 2015 #5

    billy_joule

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    Cars already have alternators driven directly by the motor and many, myself included, already charge portable devices from the electricity generated (via the cigarette outlet). It probably costs me a lot less to charge at home but it's convenient.

    this thread discusses why an engine driven alternator is a better option than driving it somewhere after the clutch, like the wheel or drive shaft.

    https://www.physicsforums.com/threads/can-you-make-the-drive-shaft-the-alternator.829421/

    Generating sufficient energy for home appliances from petrol is much more efficiently done by stand alone petrol generators than cars, and even more efficient if done at large fossil fuelled power plants. In other words, devices designed for a sole purpose (generating electricity) can most often do their job better than something with multi purpose (transportation & generating electricity). That is, power plants are cheaper and better for the environment at generating electricity than cars are.
     
  7. Sep 16, 2015 #6
    DEvens you are the Boss!! Appreciate your help a lot.
    Billy_Joule that's well understood. Thanks a lot.

    Guys, my country is suffering from power crisis and i feel its a very good opportunity for me to make some investment in renewable energy. Is the introduction of renewable energy possible in my country? Wind power and solar are in abundance but could they on their own supply electricity to a whole house? Having a solar roof for example.
    I live in Ghana.
     
  8. Sep 16, 2015 #7

    anorlunda

    Staff: Mentor

    Yes you can do that. Many people do. But the real secret is to reduce your energy consumption first. I live on a sailboat far from the shore. 200 watts of solar panels provide for all my needs, but first I cut my total consumption for my family to 0.6 KWh per day. 80% of that is for refrigeration.
     
  9. Sep 16, 2015 #8
    That's great feedback Anorlunda. Appreciate it!! I have a clearer understanding now.
     
  10. Sep 16, 2015 #9

    DEvens

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    This is an example of a process that goes like this:

    =======
    Part of the thinking process that is NOT shown to the outside world starts here.
    Recognize big problem. Explore the background and context.
    Try to think of a solution.
    Think of a solution. Call it "X".
    Decide the solution has challenges. Call them "Y".
    Try to solve ONE of the challenges. Call it "Y part seven."
    Fail. Decide to ask for help with that challenge.
    Think up a question that only shows "Y part seven."
    =======
    On some public forum, ask how to solve "Y part seven." But don't tell anybody on the forum about all the other steps that went into arriving at the thought that you must solve "Y part seven." Get frustrated because the answers don't really solve your problem.

    Where if you had started with the fact you live in Ghana and want some electricity, things would have been much simpler. The problem isn't really "can I store power from a hand crank?" The problem is really "what can I do about electricity shortages in Ghana?" That really depends on many more things.
    - How many people will be involved?
    - What kind of budget do you have?
    - What time scale is involved in producing the solution? How long does it have to work? One hour a day? 24/7 for 20 years?
    - What kind of things do you want to power with electricity? For how many hours per day? How reliably?
    - Just one house? Just one small village? A hospital? A school? A factory?

    If what you want is to be able to power a cell phone for an hour or two per day, then a hand cranked device will cover it. The cost will be round about US$50 very roughly. If you want to buy a few hundred of them you can probably get the price down per unit by quite a lot.

    If you wanted to light a school or some such application, the hand cranked device probably isn't enough. If you wanted to do anything bigger than that you want to think about some kind of generator.

    Possible ways to power a generator:

    Wind turbines are intermediate expensive. They come in a variety of sizes. The drawback is usually that the power supply is quite irregular. And wind turbines often need picky maintenance. It might do for tasks like irrigation. It could also be used to pump water into a dam, which could then run a water turbine.

    Solar power tends to be pretty expensive. But in Ghana, an equatorial country, you might make it worth while. Again, battery backup is expensive.

    Is there a nice water falls close by? Consider a flow of 1 cubic meter per second going down a 1 meter falls. Not a very big water falls. That is 1000 * 1 * 9.8 = 9800 Watts. You can probably get 30% efficiency out of a water turbine, so you can probably get pretty close to 3 kilo Watts out of such a thing. That's enough to run quite a bit of electrical equipment. Certainly you could light a school or hospital. Maybe you could even run some medical equipment, or keep medical supplies refrigerated.

    If you build even a modest dam you can probably control the water flow fairly reliably. You might well be able to modestly supply the power needs for a village this way. At the same time, you could create a small dam that would supply things like irrigation water. In Ghana, I guess you should think whether this dam will provide a place for mosquitoes to breed.

    Do you have cows or horses or any other large domestic animal? Could you build them a tread mill or yoke them to some kind of large wheel? You might get them to power a useful sized generator for a few hours per day. If you have access to a largish herd you might get them to run this thing in shifts and even get pretty close to full time power.

    Do you have a ready supply of something to burn? Fire wood? Coal? Even animal dung in an emergency. Though the dung is probably more valuable as fertilizer. You could run a steam engine. The back-of-the-envelope estimate is 1 tonne of wood burned can produce 1 mega-Watt hour of electricity.

    A diesel generator can be fairly reliable. But diesel fuel for it can be pretty expensive. Usually diesel winds up in the 20 cents per kilowatt hour range.
     
  11. Sep 17, 2015 #10
    DEvens don't really know how to express appreciation towards this education. I learned a whole lot and will do my homework well. Will post every development i make here for more schooling. Thanks sir.
     
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