Going green. Starting with my computing

Discussion in 'Electronics & Electrics' started by Yoodaa, Jul 12, 2010.

  1. Yoodaa

    Yoodaa Member

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    Ok so going green is something that I have wanted to do for a long time, but due to cost restraints, or not owning a property, it has made things difficult.

    I plan to install a household solar system hopefully next year. Yeah I know it costs a lot, but I have a fairly well paying job, and by looking at it as an investment in the future, and environment, it makes the choice so much easier. At this stage I am unsure If I should go grid/offgrid. If going grid, I want to make sure I generate more than I use as I am not interested in paying power bills.

    So I am coming to the electronics gurus of OCAU to help me take a bite into the solar world.

    I have done some tests with a power meter I bought from Jaycar. I found the following results when measuring computing devices.

    I have a desktop PC with 4 screens, speakers, etc, It pulls about 200 watts on average.

    I just bought a new Toshiba T130 ultra low voltage laptop which pulls only 25 watts when charging, and 15 watts when it if fully charged! That's a huge difference! My ADSL modem pulls 7 watts.

    So I was going to sell the desktop machine, and use that to fund my green solution. This is a small project to get me familiar with how solar works, and the technologies involved.

    I was wondering if someone can help me calculate what size panel and battery/batteries I would need to sustain my new laptop and modem. Again I understand this is not a conclusive solution to my overall solar needs, but I am hoping to merge this system with the big system I plan to install down the track.
     
  2. Franc

    Franc Member

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    FWIW id recommend staying on the grid, plus you get those nice amounts for elec from the govt/retailer :)

    Even without this consideration, going off the grid and your usage overnight would mean you would have to invest in batteries and all the other ancillary stuff to support this..rather than just panels/inverter etc

    The money you spend on this could probably be better economically and enviromentally invested in other ways.
     
  3. @rt

    @rt Member

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    Sounds like you need to return the power consumption meter.

    It's a very large project to power all of the devices you mentioned.
     
  4. Jonchilds

    Jonchilds Member

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    Definitely go for panels and a grid-tie inverter. The money you save on batteries will pay for extra capacity, and you won't waste any solar energy if your batteries are fully charged and not running any appliances. The downside to this is that you still lose power if the grid goes down, even if the sun is shining (for very valid safety reasons).

    Batteries also have a limited life of 2-5 years (depending on usage pattern). Replacing lead-acid batteries every few years isn't really 'green'.

    Grid connected solar is also a reasonably modular enterprise, so you can add extra capacity down the track without too many issues.
     
  5. -badlad-

    -badlad- Member

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    +1
    Grid connection is a no-brainer if you are already connected or close to mains power. I think you are definitely on the right track too with reducing your consumption before harvesting solar power. Are you installing solar hot water as well? This can account for around 30% of your energy usage.
     
  6. OP
    OP
    Yoodaa

    Yoodaa Member

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    Thanks for the input guys.

    This initial project I speak of was to power just my new low voltage laptop and modem.
     
  7. aXis

    aXis Member

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    With the mony you waste setting up a small scale battery system just for the laptop, you may aswell start preparing a low capacity grid tie system, with a big enough inverter to cope with the extra increase in capacity later.

    Any offset power is an improvement, it doesnt have to be connected directly to the laptop to save.
     
  8. Delator

    Delator Member

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    the laptop has a battery though :p

    I have too thought about something similar, like getting a cheap ebay solar panel to run a laptop.. just for more of a project
     
  9. Franc

    Franc Member

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    Sealed Gel batteries designed for the purpose can last 15 or so years
     
  10. RussellK

    RussellK Member

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    Yeah, I think many missed that. It is true, however, that the various govt. subsidies make it cheaper to grid-connect, as there are no subsidies for off-grid (that I know of).

    If you want to futz a little with solar power, your laptop might be a good starting point.

    You say it draws 15W, while the ADSL modem draws 7W, so 23W. What you haven't mentioned is how many hours a day you want to use both. That plus the power draw will determine how many watt-hours you need a day. Also, you need to know how many of those hours will be after dark, as this will determine what battery capacity you need.

    At a very under-thought guess, I'd say you want something like 40W panel (panels cost about $6 per watt) maybe 3 x 7AH 12v sealed lead acid batteries ($18 a pop) a solar regulator to go between the two (MPPT would be nice), and switching voltage converters to power your laptop and modem (I would not use a 240v inverter for efficiency reasons).
     
  11. 3stars

    3stars Member

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    sorry for the highjack, but where do you get those batterys that you speak of.
     
  12. Goth

    Goth Grumpy Member

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    12 V 7 Ah is a very common size for SLAs, get them at Jaycar or many other places.
     
  13. paulvk

    paulvk Member

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    Solar power will take 20 plus years to just to pay for the cost of the system better to put the money into reducing power consumption eg double glazing, insulating roof walls and floor, you can also get off peak heating for the home. I have a 4 bedroom home with wall and roof insulation during summer a 1hp and 1.5hp aircons keep it cool I was told I would need twice this!

    And just some info 185watt solar for $770 = $4.16/watt
     
    Last edited: Jul 12, 2010
  14. Franc

    Franc Member

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    Not with pfit though...
     
  15. teno45

    teno45 Member

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    where did you come up with that number? a couple guy from work have recently got solar panels, and one guy got a credit for over $250 after his night time usage and gas usage. from that one three monthly bill, he calculated around 4 years to pay off his system.
     
  16. 3stars

    3stars Member

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    not for 18 dollars you don't
     
  17. OP
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    Yoodaa

    Yoodaa Member

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    I was planning on spending $1000 on this solution.

    My thoughts were to buy a 200 Watt panel or so (it can be used once I expand system also).

    As for the rest of the components and costs, I have no idea.

    My laptop battery runs for 8 hours which is a working day for me. So I need, at a guess, 4 hours of charge time which is very generous which the solar setup will provide.

    The laptop will be charged off a car 12V charger so no need for inverter, and the modem runs off 12V anyways.

    So I need to run 7 Watts 24/7
    30ish watts for 4 hours of night
     
  18. Privatteer

    Privatteer Member

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    Add a extra 30% to your figures you got from your power meter.
    Those cheap pieces of **** are not accurate with switch mode power supplies.
    They are a bit closer if you have a new power supply with PFC.

    As an example my PC reads at 210W, real usage is 375W using a proper true rms meter.

    Try this site its not too bad for doing an estimation of what size panel, solar regulator etc you need.
    Don't skimp on battery size, repeatably draining them flat shortens the lifespan considerably.
     
  19. FantoM_CircuiT

    FantoM_CircuiT Member

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    For anyone else interested, the new Mac Mini has surprisingly low power usage. Around 8 watts for web browsing. I was pretty shocked - though there's no screen with that

    http://computershopper.com/desktops/reviews/apple-mac-mini-2010-version
     
  20. paulvk

    paulvk Member

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    1850watt (1.85kw) is 10 x 770 = $7700 for panels say 6 hours a day (being very generous) 1.85 x $0.22 x 6 = $2.44 a day, perfect year 365 days of sun $891.33 dolars over 8 years just to get the panels in a perfect desert. Note the rebates ect only last for less than 10years!
    If you put the money into what I said you could bring your bill to one quarter or less!
     

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