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solar workshop time

Discussion in 'General Electronics Discussion' started by donkey, Nov 26, 2011.

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  1. donkey

    donkey

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    Feb 26, 2011
    well its time I got off my lazy backside and finally got into building my solar workshop.
    Before I start spewing forth details please note I am NOT a licensed electrician and am trying to minimise the use of one. In fact I hope to not need one except for plugging up my inverter but will see what people say.

    Anyway the items I will use in the inverter will be chargers mostly, I know that boosting up to 240v then back down to 18v is not ideal but will have to do for now. the only exceptions I can think of would be a fan for air flow, a soldering iron and a light(will try to find an awesome LED one). the question becomes however, At any point I could be charging AND soldering with fan and light in use, what inverter, battery and solar panels should I use? given that on average I will use it for about 3 hours per day 2 days of the week.

    also is there a battery tester that comes with solar chargers to monitor battery usage? I would hate to spend money on a deepcycle and have sulphation render it useless. I would ideally like the monitor to stop overcharging the battery while at the same time switch from solar to mains if absolutely necessary, while displaying details via a bar graph or lcd if I got enough money

    and last but not least are there any decent trichargers? I mean one that charges the battery from solar first, then wind if there is any and then lastly mains if the first 2 are not working?

    edit: this IS the last thing, I am trying to make it portable as well as we don't own this house. would there be anything I should consider before putting it on a trailer?
     
    Last edited: Nov 26, 2011
  2. davelectronic

    davelectronic

    1,087
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    Dec 13, 2010
    Hi donkey.
    I cant surgest a make / model of solar panel array etc, or regulator for it, but some work shop gear is power hungry, even your soldering iron, i would think a substantial solar system and a large battery bank, or your be on mains all the time, wind will offer better charging for work shop use, ive a friend at maplins a radio amateur he plays with solar in his radio shack, ive often interrupted his work flow for chats on his latest shack venture.

    By all accounts his solar powers light duty stuff, and it works well, but he wants more power available, we went into the cost of solar for his more ambitious demands on power, but concluded it would cost a small fortune here in the uk, anyway good luck if it be modest or massive, but wind is one to think about, and at times we do get some huge gails, plus it would still charge on windy nights, solar not so at night. Or a combo, good luck with it. :)
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,412
    2,780
    Jan 21, 2010
    I have a PV array which generates a peal power of around 5kW. In practical terms this means I see a peak each day between 3.5 and 4.5 kW. If it's cloudy it can fall substantially (to maybe 2kW). If it rains (heavy cloud) it can fall to under 1kW. Added to this is the change in power I can get from the sun by time of day. I am starting to get a couple of hundred watts by 7 or 8 am, and it's back down to a couple of hundred by 5 or 6 in the afternoon. To do this, I have about 30 m^2 of panels.

    So, as you can see, variable power, and limited duration. My system is connected to the grid, so I give the grid power when the sun shines and draw it back when it doesn't. This is ideal if grid power is available because you don't need storage (cost, maintenance, loss in efficiency)

    Whatever way you go, your system should include a MPPT regulator of some sort, otherwise you'll be throwing away power.

    The type of charger you're describing doesn't really exist. I would recommend that if you have access to mains you go grid-connected, or turn on the mains charger for your batteries at night or when the charge falls below a critical value.

    Unless mains availability is a design issue (i.e. you want to use this as emergency power), I would not be looking at a system with batteries these days.

    There may be significant issues with grid connecting your system unless you have a sparkie do most of it. However, if you have a tame sparkie on hand, he may allow you to wire up the system and then check it for you.
     
  4. davenn

    davenn Moderator

    13,657
    1,888
    Sep 5, 2009
    The only thing I hate about grig connected system is that you cant use your own generated power.
    Here in Sydney, the power companies only give you about 2/3 remuneration on the price. So whatever power you give into the grid compared to what you buy off them, you are still loosing cost wise.
    Its the main reason I havent gone solar. I have had comments from many people that have installed or were thinking about installing solar, that they never realised that they couldnt directly use the power they generated. It goes directly to the grid.

    I would still want to do the battery charging system. I have the batteries, currently 3 x 12V 120AH. And have ready access to more as time goes by ( no cost). I could supply a lot of low voltage lighting, all my radio gear battery chargers etc off that. The real hassle is still the cost of the panels.
    The other hassle is with a battery system you can never supply enough power to power the household items that use the most juice. Water heater, Aircons, oven/rangetop, fridge-freezer.

    Dave
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,412
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    Jan 21, 2010
    We get paid based on net feed in. So we get 100% on anything we generate if we use more than we generate.

    If we generate more than we use (and we do) then we get 8c/unit (that sucks) plus an extra 47c/unit (which is nice)

    There are very good arguments for increasing the former and decreasing the latter.

    edit: Nett feed in tariffs make you change your behaviour to a greater extent than gross feed in tariffs
     
    Last edited: Nov 26, 2011
  6. donkey

    donkey

    1,289
    56
    Feb 26, 2011
    hey guys i think I may have been mis understood here. I only want a small plant to charge batteries on my 5 days at work then on my two days off I will use it for about 3 hours per day to charge chordless drills etc, a fan and a few led lights.
    I was thinking about 50 a/h should more than cover that but I thought I would ask to be on the safe side. i will be using an inverter for most activities and the soldering iron is 130w(thats with turbo charge to heat it up, as for the ryobi drill charger it says the input is 75w. I was thinking around 300watt inverter to cover these items and the fan (which I may just run off mains anyway) and the LED setup I plan on using (a few ultra brights directed at the work area.
    just wanted to know if this sounded right and what size panels I should look for to accomodate this.
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,412
    2,780
    Jan 21, 2010
    There are calculators on the web where you can calculate the power you can generate from a panel placed at a certain (usually optimal) angle at a certain latitude by time of year. That will effectively tell you how much power you'll get.

    If you're charging a lead acid battery, a rule of thumb is that you need to put back about 150% what you get out.

    Your inverter will have a certain efficiency, so factor that in too.

    Then calculate your total load and work backwards to the size of panel you require.

    If you want to allow for days with less sun, you need to multiply your battery capacity and also your panels by some factor (x N for the batteries but perhaps less for the panels)
     
    Last edited: Nov 29, 2011
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