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  • ChrisOlson
    started a topic Sizing Off-Grid Systems And Using Gen Support

    Sizing Off-Grid Systems And Using Gen Support

    I'd like to try to make a contribution on what seems to be a very hard thing to understand for most folks looking at making a move to off-grid. This is more applicable to medium to larger full-time off-grid homes. Smaller systems like single 120V Outback setups in part-time off-grid cabins, or very small off-grid full time homes where daily energy consumption is under 5 kWh are probably not going to benefit from it.

    I am dealing with sizing of the inverter, batteries and generator(s). Sizing battery banks and solar/wind/hydro capacity is a totally different issue. But the basis of my contribution is to save money on batteries and inverters and generator fuel by properly sizing the generator and inverter to meet loads, and using Generator Support to prevent having to buy expensive stacked inverter setups and the additional battery capacity required to power them at full rated load. Stacked inverters might look impressive on the wall. But if you don't have the batteries to power them they're useless. And few off-grid folks can afford the batteries it takes to power even ONE 6.0 kVA inverter at full rated load for more than about one hour.

    There's two schools of thought on off-grid. The one assumes off-grid means never running a generator unless in extreme emergency, and using a generator is a "sin". The other (more targeted to larger systems) integrates the generator with the system with auto-start, etc. and it is run on a regular basis to enjoy a more comfortable off-grid lifestyle. If you think making the move to off-grid is "going green" you are dreaming. You only make the move to off-grid because you can't get utility power where you want to live. It has nothing to do with "going green" except for the fact that it takes a lot of green (money) to do it.

    Common mistakes I see made all the time:
    1.) Buying a generator that is way too big. The result is that you can't afford to run it because it sucks OPEC dry as soon as you turn the key. A combustion engine generator needs to be operated at 80% rated load or better for least cost/kWh. If you buy a 8.0 kVA generator do you have better than 6.0 kVA load for it when it is running? Few do - even with larger systems.

    2.) Installing stacked inverters for intermittent heavy loads when a single one with generator support will do the job.

    3.) Purchasing excessive battery storage capacity (and not near enough RE capacity to charge them, which is a separate topic), thinking you should be able to go three days without running a generator if there's no sun. This is ridiculous. 24 hours is adequate on straight battery power if you design a system using a tiny prime generator to manage how much you use from batteries during peak draw times (like in the evenings in the winter). The result is that you only need 1/3 of the battery capacity you think you need by managing loads with a little genset to keep the peak draw on the batteries below the 20 hr rate of discharge. Put the pencil to it over the expected life of batteries and you will find that even with fuel costing twice what it is presently in the US, the fuel in a tiny generator to manage battery capacity is cheaper per kWh than the battery replacement cost at 7 years.

    Off-grid power is VERY expensive. Much more expensive than utility power. Batteries are the single most expensive component of an off-grid power system. Not inverters, generators, fuel, solar panels or wind turbines. Batteries. I have seen more "hobby" hybrid grid/off-grid systems get abandoned when the batteries failed than for any other reason. Having to spend $3,000+ on a battery bank at replacement time becomes a reminder of the realities of how much off-grid power really costs.

    There is a common misconception that you cannot cycle batteries below 50% DoD or it will ruin them. This is totally and blatantly false for real deep-cycle batteries. They can regularly be discharged to 80% DoD and it doesn't hurt them one bit. And in fact, it makes them more efficient on charging.

    The rules of thumb I have developed over 14 years of doing this:

    1.) Purchase the battery capacity you need to power your average daily consumption with the batteries discharged to 80% DoD over 24 hours. Example: you use 15 kWh/day in your home on average. You need a 19 kWh battery bank. Normal cycle depth will be around 50% on the average day if you have adequate RE generating capacity to recharge them daily (under average solar insolation conditions) plus carry normal loads during the recharge period. On poor RE days you will cycle them deeper and manage how much you use from the battery by using your little prime genset. Minimizing the size of the battery bank up front prevents "sticker shock" when the day comes that you have to replace them.

    2.) Determine what your peak load will be and buy an inverter that can carry that peak load for a few minutes, then switch to using Gen Support to power the peak load.

    3.) Size your peaking generator so it reduces the load on the inverter during peak load to no more than the 10hr discharge rate of the battery bank. Example: your peak load is 7.5 kVA. You have a 6.0 kVA inverter that can handle the 7.5 kVA peak for 15 minutes before the load on it must be reduced to below its rated continuous output. You have a 1,000ah battery bank at the 20hr rate (40 amp draw on the bank to 80% DoD). The 10hr rate will be approximately 70 amp draw on the bank with Peukert Effect. 70A draw on a 48V system @ 90% inverter efficiency is 3.0 kVA. You need a generator capable of delivering 4.5-5.0 kVA.

    And this brings up the topic of Generator Support, which is the only way all the above works. I have talked to many people who think their Magnum PAEs et al have it. They don't. With an inverter that does NOT have generator support in it, you are relegated to purchasing an excessively over-sized generator to be able to carry the peak loads because the inverter does not have the capability to sync with the genset and assist it. This does not give you the ability to carry a wide variety of loads and always keep the genset at peak efficiency (read above about sucking OPEC dry). Nor can you even come CLOSE to efficiently use this big genset for battery charging if you charge batteries with it thru the inverter/charger. There's only a handful of off-grid inverters that have Generator Support. And these inverters are quite expensive compared to the ones that don't have it. Carefully research what you're buying for an inverter before you buy it. While the batteries are the most expensive thing, the inverter is the heart of it all that makes it work.

    So how does peak load support using this system work, exactly, and what does it do for you? In summary:
    1.) It conserves battery energy during peak load events on your system by reducing the amp draw on your battery so the Peukert Effect doesn't sack them out.
    2.) It allows the use of a smaller more efficient generator that is able to be kept at >80% rated load at all times
    3.) It saves money on batteries and inverters by not having to buy twice as much for stacked inverter setups.

    I made a demonstration video of it with our XW Power System to show you what it does in a real life off-grid home where it is used every single day. And has been used here for many years, previously with our Xantrex SW Plus before we replaced it with the XW system:


  • Sunking
    replied
    Originally posted by morgandc View Post
    ChrisOlson, you mentioned that you use a very small air cooled Diesel Gen for you small prime gen, can you give us some detail on your generator and possibly some of the selection criteria you used?
    You are talking to ghost. Chris has not been here for 2 years. So do not hold your breath. Well you can hold your breath. If you die, then you can talk to Chris.

    Leave a comment:


  • morgandc
    replied
    ChrisOlson, you mentioned that you use a very small air cooled Diesel Gen for you small prime gen, can you give us some detail on your generator and possibly some of the selection criteria you used?

    Leave a comment:


  • derekshores
    replied
    Ok this is all so new to me it is making my head spin, I am trying to run my TV, internet modem and cable box. I have one 100 watt renogy panel and a 175 ah 12v battery with a 1500 watt inverter, I live in the san luis valley of Colorado and get some of the best solar sun in the US at 7800 ft. I have 3 more batteries and 2 more panels. I am trying to use the other two panels and the other two batteries for some greenhouse applications. Is my setup for my TV and internet adequate? I really only need to use the internet and tv at night for about 4 hours max. Sorry for the newbie question but this is sooooooooo far above my level of knowledge it is scary

    Leave a comment:


  • Mike90250
    replied
    Long, thorough discussion about generators and loads. Even a section on LED light quality (color & intensity) Done by a movie company rental site.
    in the old days, generators ran lighting which was all resistive loads. Now CFL and LED's use weird ballasts that muck up the power factor and that messes up the generators
    http://www.screenlightandgrip.com/ht...enerators.html

    some great charts and links to videos in there.

    Leave a comment:


  • zed
    replied
    Thanks for a very interesting thread....it was enough to get me to register.

    I live on an island off southern Tasmania with a system that I would recommend to anybody.

    I run a system by a company called SMA.

    The main product in the room is called a Sunny Island inverter/charge controller.

    Some of it's features are full generator control, user programmable to load share and charge as per the original thread topic.

    It does this absolutely comprehensively.

    But...the best feature is that it can interact with standard grid tie inverters fooling them into thinking they are connected to a utility grid.

    This makes it scaleable to almost any depth, utilising cheap grid tie MPPT inverters which the Sunny Island then uses to keep the batteries maintained.

    Battery charge controllers and the array connectivity here is 15kw to 48 volts...done cheaply...

    It does this by phase shifting (or mis-matching) to keep the input load under control.

    Absolutely bullet proof and state of the art.....worth a look for anyone contemplating a new setup.


    My setup:-

    Sunny Island 8.0H controller
    Sunny Island SB5000TL 5kw grid tie inverters in off grid mode X3
    BP monocrystalline 190W panels x 72
    200AH 12v AGM lead acid batteries organized as 8 banks of 4 in series/parallel 48V strings...1600AH in total @ 48v
    Auto start 5kw diesel generator.

    I run a seawater desalination unit and stock standard resistive element hot water system, clothes dryer, microwave ovens etc.

    Desal uses 3kw and produces 300L an hour....or 10w/Litre to make drinking water from seawater with reverse osmosis.

    The Sunny island can be user programmed to charge batteries, when batteries full hea tthe hot water, when water hot desalinate seawater....etc etc

    Our aim was to make living as close to being on grid as possible.

    We consume around 25kw a day, with washing etc done when the sun is shining to keep battery DOD to around 10-20% maximum.

    I cannot remember the last time the generator kicked in.

    Panels are so cheap now we sized our arrays for worst case conditions...winter/overcast....so most days by 10am batteries are charged to 100%.


    .
    Last edited by zed; 03-19-2016, 07:30 AM.

    Leave a comment:


  • solar pete
    replied
    Originally posted by Riley5781 View Post
    This is an interesting first thread for me.
    We are building a cabin on a lake that's off grid. I wish I had power but it's not in the plans for at least 5 years.
    Chris - I like your thoughts on sizing and using the Gen Set for peaks. I hate buying batteries (consumables).

    I skimmed the other pages but I now wonder about type of Gen set. Everybody where I am uses gas or propane and I was thinking propane but maybe not.

    Thanks again and I hope to learn more at this site over the coming months.

    Riley

    Hello Riley, welcome to the neighborhood.

    Leave a comment:


  • Riley5781
    replied
    This is an interesting first thread for me.
    We are building a cabin on a lake that's off grid. I wish I had power but it's not in the plans for at least 5 years.
    Chris - I like your thoughts on sizing and using the Gen Set for peaks. I hate buying batteries (consumables).

    I skimmed the other pages but I now wonder about type of Gen set. Everybody where I am uses gas or propane and I was thinking propane but maybe not.

    Thanks again and I hope to learn more at this site over the coming months.

    Riley

    Leave a comment:


  • Sunking
    replied
    Originally posted by armourereric View Post
    I have been reading this thread over several times and am fascinated with the results. Would it be possible to get a "shopping list" of the specific components used? That way I can price out this system with real time cost.
    Sure I will do it for a fee. No one here is a Professional Engineer eexcept me who can legally help you. But I do not work for FREE.

    Leave a comment:


  • armourereric
    replied
    I have been reading this thread over several times and am fascinated with the results. Would it be possible to get a "shopping list" of the specific components used? That way I can price out this system with real time cost.

    Leave a comment:


  • Sundetective
    replied
    Originally posted by SunEagle View Post
    I figured he move his yacht out before the winter freeze. He certainly has built an impressive off grid system and has the fortitude to keep upgrading it.

    Maybe he will drill for oil to run that Cummins.
    On top of all that in his most recent YouTube video Chris talks about
    how much time he is spending on his radio station to boot-ie
    dis winter. AC9KH radio. (See YouTube.)

    One of the fanboy's liable to be flying him back and forth from PR.
    Will a jet helicopter make it dat far.

    Sunking, (his Junior Engineer) may know.

    It may go forever if old Bill kept reading and cross checking -
    But he won't.
    Give me a dollar.

    It was fun looking at the story just a tad.

    Equipment is one thing.
    The story is another.

    Bill Blake

    Leave a comment:


  • SunEagle
    replied
    Originally posted by Sundetective View Post

    Actually the Yacht is Located in Puerto Rico now.

    Remember there was 6 feet of snow on the solar panels
    and the Wind Turbine was froze solid when he got back from
    2 months of sailing dis winter.

    Going to be hell on wheels mountain climbing 500 gallons
    of fuel oil at a clip into dat place once Chris has that Cummins
    Power Plant running 24 / 7 and throws the Rolls 5000 batteries out.
    No more batteries at all. 25,000 Watt generator.
    Thousands of gallons.
    Give me a dollar
    The man is the LeRoy of the whole bunch of you.
    I figured he move his yacht out before the winter freeze. He certainly has built an impressive off grid system and has the fortitude to keep upgrading it.

    Maybe he will drill for oil to run that Cummins.

    Leave a comment:


  • Sundetective
    replied
    Originally posted by SunEagle View Post
    Sounds like you have done so searching for his location. The only other data I can add is concerning his yacht which he stated he kept at a marina in Bayfield and that being on the lake has help increase the output of his wind turbine. He also mentioned about his "scooter" day trip to Duluth so I figured he was in upper WI near the lake.

    Of course he could have any number of places he calls home.
    Actually the Yacht is Located in Puerto Rico now.

    Remember there was 6 feet of snow on the solar panels
    and the Wind Turbine was froze solid when he got back from
    2 months of sailing dis winter.

    Going to be hell on wheels mountain climbing 500 gallons
    of fuel oil at a clip into dat place once Chris has that Cummins
    Power Plant running 24 / 7 and throws the Rolls 5000 batteries out.
    No more batteries at all. 25,000 Watt generator.
    Thousands of gallons.
    Give me a dollar
    The man is the LeRoy of the whole bunch of you.

    Leave a comment:


  • Sundetective
    replied
    Originally posted by SunEagle View Post
    Sounds like you have done so searching for his location. The only other data I can add is concerning his yacht which he stated he kept at a marina in Bayfield and that being on the lake has help increase the output of his wind turbine. He also mentioned about his "scooter" day trip to Duluth so I figured he was in upper WI near the lake.

    Of course he could have any number of places he calls home.
    To be honest with you all I did was check how much wind was up there
    for the fun of it after the Midnite Solar story about the Bergy Windmill
    popped up in Barron.

    Chris has his GPS Coordinates and the elevation on at the top of his
    Weather Underground KWIBARRO3 page so its kind of hard to miss.

    His whole story sounds facinating.
    It a goodie.

    Bill Blake

    Leave a comment:


  • SunEagle
    replied
    Originally posted by Sundetective View Post
    I can believe Chris is very busy - indeedie.
    Over at the Fieldlines Forum some of his
    3400 posts are in his thread called Ethanol Plant.
    He grows so much corn that he shows pictures of his and hers matching
    full blown tractor trailers (one for his wife) delivering 28 tons of corn each - at a clip.
    Now THAT is growing some serious corn.
    Old Bill ain't lyin.

    Just assumed he was with the Chris and Kristin Olson Weather Station
    KWIBARRO3 near downtown Barron, WI.

    The GPS numbers match up with what is shown in the YouTube videos.
    Perhaps they go north in the winter to do battle with the winter.

    That may be where the 24 Rolls 4000 Series T12 250 batteries are located
    in the 12 Long String that we discussed in one of my threads at Fieldlines.

    Here he has Rolls 5000 but wants to dump them so there must be a second
    Location.
    Up North is where he is probably the Engineer like Sunking is as he writes
    about here at SPT.
    Unless he squeezes it in with the farming and the trucking
    at Barron.

    At YouTube (Chris Olson Olson Farms) and Fieldlines he is definitely a
    Bigtime farmer.

    Midnite Solar (Chris Olson Midnite Solar at Google) has Wind Turbine
    Installation pictures at Barron, WI.

    Chris must have moved the Turbine up North as well.
    You can't blame an old detective for getting it all messed up.
    There were other things as well.

    Bill Blake
    Sounds like you have done so searching for his location. The only other data I can add is concerning his yacht which he stated he kept at a marina in Bayfield and that being on the lake has help increase the output of his wind turbine. He also mentioned about his "scooter" day trip to Duluth so I figured he was in upper WI near the lake.

    Of course he could have any number of places he calls home.

    Leave a comment:

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