How would you set up your off grid shop?
Close
Login to Your Account
Page 1 of 2 12 LastLast
Results 1 to 20 of 27
  1. #1
    Join Date
    Jan 2020
    Country
    UNITED STATES
    State/Province
    Alaska
    Posts
    5
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Default How would you set up your off grid shop?

    So, imagine yourself with a pretty state of the art (but small) solar power setup- 4000 watt pure sine inverter running off a 24v battery bank supported by 1500 watts of solar panels. That’s what I have. I thus have available 24v DC, 120 and 240v AC(single phase) with a maximum power surge of 5850 watts. Inrush surges on a 2hp motor can hit 9000 watts, but most of the machines in this semi professional wood+ blacksmith shop want 1.5 hp at least. Efficiency is paramount- every watt counts.
    If it were you would you:
    A: Go DC direct somehow, using 24v DC? Maybe a buck boost transformer?
    B: Stick with VFD’s to eliminate inrush surges on 1.5-2hp machines? If so, for max efficiency, should the motors be 240v or 3ph with a 240v input?
    C: Spend $180,000 to get grid power (HAHA…)
    D: Do something else altogether?

  2. #2
    Join Date
    Jun 2001
    Location
    St Louis
    Posts
    18,184
    Post Thanks / Like
    Likes (Given)
    1956
    Likes (Received)
    3087

    Default

    If you have 240V single phase, I would use it directly if you can.

    Adding VFDs and using 3 phase is a way to avoid inrush, and may be a good idea if you have to. The efficiency will not be too bad, and the sine inverter should operate them OK. Most VFDs are 95% to 98% efficient.

  3. #3
    Join Date
    Nov 2011
    Location
    Pennsylvania U.S.A.
    Posts
    16
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    1

    Default

    i just got done with a 5 month long abusive relationship with an off grid shop. i found vfd's very effective in reducing inrush as you can set the ramp up and ramp down time. keep in mind they only work on 3phase motors and operate at reduced power if designed for 3 phase supply. Consider a diesel generator and transfer switch to supplement power.

  4. Likes swatkins liked this post
  5. #4
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    28,744
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    8910

    Default

    Quote Originally Posted by Gringo-Gaucho View Post
    So, imagine yourself with a pretty state of the art (but small) solar power setup- 4000 watt pure sine inverter running off a 24v battery bank supported by 1500 watts of solar panels. That’s what I have. I thus have available 24v DC, 120 and 240v AC(single phase) with a maximum power surge of 5850 watts. Inrush surges on a 2hp motor can hit 9000 watts, but most of the machines in this semi professional wood+ blacksmith shop want 1.5 hp at least. Efficiency is paramount- every watt counts.
    If it were you would you:
    A: Go DC direct somehow, using 24v DC? Maybe a buck boost transformer?
    B: Stick with VFD’s to eliminate inrush surges on 1.5-2hp machines? If so, for max efficiency, should the motors be 240v or 3ph with a 240v input?
    C: Spend $180,000 to get grid power (HAHA…)
    D: Do something else altogether?
    My fav'rite trick - tough places to git at for service - is to use oversized gen heads for a Diesel's rated motor power, or oversized inverters for a battr'y plant. Less likely to BBQ them.

    Dog sled, float plane or parachute drop from a dirigible, your cheap option is to double the inverter rating. The better ones are already designed for syncing to be paralleled-up. Bit of luck, you add-on rather than replace?

    Now you also have fall-back redundancy / easier scheduled maintenance, wotever woven right into the deal.

    Then add a couple of dual-duty "starter" rated marine/rv batteries to the otherwise slow discharge but DEEPER discharge battery plant. Or so we might presume you'd be using? Same again, add-on, not replace.

    May have to juggle charger control, but you get your starting surge covered, and once again more depth if something goes pear-shaped in between dirigible, dog sled, or icebreaker runs.

    Bit of a nuisance adding VFD's for motors that small? Most especially if they are single-phase, would need swapped-out for 3-Phase. Got 3-Phase, yah could do inverter-foo once instead of VFD-foo, many.

    Inexpensive VFD don't have the best longevity, either. Inverters are the better bet for durability.

    With stouter inverters in place, you can also add-on to the collector array and battery plant as budget permits.

    Batteries are wotever they are.

    Planning to skip Edisons and go from ignorant lead-acid to "saltwater" tech, but I don't have temps as cold as as to freeze my alaskaoff.

    Can't see the point in going after low mass in a fixed-plant battery. Lit-me-ums are for mobility needful goods.

    Old Lady Earth is strong enough to hold up a glacier or a forest - even a mountain or three, after all. I could hope to set a saltwater battery plant into a hole in the back garden much as one would have done with a septic tank I do NOT need?

    NB: I don't have to dog-sled in diesel. I'm ON good mains.

    Even so. Those "in the know" say that for STABLE machine-tool operation at a 10 KW load? My 10 KVA Diesel should be as much as a 100 KVA.

    Sanity check sez 2:1 minimum, four or five to one, practical, and just not EXPECT really high-grade stability.

    Similar deal, your plant.

    As presently spec'ed for 4 KW, your tool operation "quality" can be expected to start tailing off at ONE KW and degrade progressively.

    Numbers?

    Numbers are a snapshot.

    Life is the FULL MOTION video. Old third-world Telco and laterite and canvas tent field MIL-SPEC gut sez you got about HALF the power you are actually going to need.

    Right about what I'd call as Goldilocks size just for running my fridge-freezers, "with out fail", IOW.

    PS: Me late Dad had a significant hand, ALCAN highway, 1942. Seems to me he said Alaska has these long spells it don't git dark atall. And then another spell where it don't get LIGHT? Old workmate, ACS / ALASCOM vet, SIG-C Master Sgt. "Tanana Charlie" Wilson confirmed it. Gets dark. Stays dark for a spell.

    Solar? Year-round?

    B'lieve I'd want fired steam run off a Methane "digester". Mosquito-biomass fueled part year, wood waste the other.

    Mosquitos still run about the length of a Hudson's Bay double-bitted axe handle up there? Between the eyes?

    'Bout the same power as a Vespa motor scooter, but too much like work to get 'em onto a treadmill to work as pairs.

  6. #5
    Join Date
    Oct 2005
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    16,499
    Post Thanks / Like

    Default

    Maybe add in a couple (or several) small windmills, can you tap a local stream for "microhydro"
    as well ?

    Diversity is a good thing.

  7. #6
    Join Date
    Sep 2002
    Location
    People's Republic
    Posts
    3,705
    Post Thanks / Like
    Likes (Given)
    326
    Likes (Received)
    2373

    Default

    I think that I would go looking for a used generator

    The amount of time you would actually use your highest load machines would amount to very low fuel usage.

    That amount of solar is not likely to give you significant usage of 240v equipment.

  8. Likes Dumpster_diving, Citxmech liked this post
  9. #7
    Join Date
    Jun 2001
    Location
    St Louis
    Posts
    18,184
    Post Thanks / Like
    Likes (Given)
    1956
    Likes (Received)
    3087

    Default

    The big problem with the numbers you have shown is the recharge rate. The 1500 W of panels is small.

    The more interesting number is the battery capacity. That sets your run time per day, and your reserve capability to run without sun for a few days.

    Since you are in Alaska, I expect your sunny day percentage is fairly low in winter. Not usually known as a hot solar area, looks like it is about the same latitude as Northern Scotland.

    You likely would want a good sized battery, and the biggest array you can put up. Not sure it would pay. The genset is likely a decent idea.

  10. Likes JCByrd24, Dumpster_diving liked this post
  11. #8
    Join Date
    Oct 2005
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    16,499
    Post Thanks / Like

    Default

    How is everyone else in your immediate locale doing electricity ?

  12. #9
    Join Date
    Jan 2009
    Location
    Maine, USA
    Posts
    203
    Post Thanks / Like
    Likes (Given)
    100
    Likes (Received)
    92

    Default

    I think JST is right, 1500W of panels is measly for Alaska. I have 3800W in Maine, and my parents have about double that. Here this produces more than my/our usage in summer, but not in winter (we are grid tied and net meter). You will not avoid generator use, and because of that, my suggestion would be to size your generator to your tools, and run it when using tools, and to charge batteries when they need it. Use solar/batteries to power lights, fridge, TV, etc.

    Most tools in that power range will not be 3 phase by default, so will not run on a VFD. If you really want to run them on batteries, the simple answer is upsize the inverter to handle the inrush. You could then maybe downsize your generator to a quieter more fuel efficient model running higher duty cycle compared to a generator sized run the tools.

  13. Likes JST, jimmy s liked this post
  14. #10
    Join Date
    May 2017
    Country
    UNITED STATES
    State/Province
    Massachusetts
    Posts
    373
    Post Thanks / Like
    Likes (Given)
    399
    Likes (Received)
    188

    Default

    I will follow the comments closely, because I've confronted a version of the same.

    My experience (with a 220v 2 hp well pump) and research (limited Googling) is that 4000 watts of inverter and 1500 watts of PV panels 'aint going to do it. And the battery bank and inverter capacity upgrades are not particularly cost-effective. Unless you place a hefty premium on 'green'.

    What is cheap and easy is generator capacity. A 6,000 Honda generator running on gas is easily capable of handling in-rush current on a 2 hp motor (or driving a decent welder). Like $1,000 or less cheap.

    Getting to the equivalent out of PV is going to be 10x that cost and run-time, stand-by availability, and reserve capacity will be inherently limited.

    At least that's been the result of my research thus-far.

  15. #11
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    28,744
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    8910

    Default

    Quote Originally Posted by digger doug View Post
    Maybe add in a couple (or several) small windmills, can you tap a local stream for "microhydro"
    as well ?

    Diversity is a good thing.
    If the OP really IS in "Alaska"? Depends WHERE. Diesel may have a watchacallit .. ah.. "transport" premium, is it?

    Seasons can give "diversity". Summer days can be like Alabama or Arkansas.

    And yah think Kane, Pennsylvania or Hibbing, Minnesota, or Cow Hamshpire's Mount Washington are COLD, wintertimes?

    Only now and then.

    Meet Alaska. "Enduring" cold, yah might class it?

    Hydropower is a challenge...


  16. Likes neilho liked this post
  17. #12
    Join Date
    Oct 2005
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    16,499
    Post Thanks / Like

    Default

    Quote Originally Posted by thermite View Post
    If the OP really IS in "Alaska"? Depends WHERE. Diesel may have a watchacallit .. ah.. "transport" premium, is it?

    Seasons can give "diversity". Summer days can be like Alabama or Arkanasas.

    And yah think Kane, Pennsylvania or Hibbing, Minnesota are COLD?

    Meet Alaska. Hydropower is a challenge...

    Yup, that's why I asked "what are your neighbors doing for electricity ?"

    No need to wing it.

  18. #13
    Join Date
    Aug 2012
    Location
    California, Central Coast
    Posts
    4,035
    Post Thanks / Like
    Likes (Given)
    2226
    Likes (Received)
    1587

    Default

    Can any equipment with small motors be swapped out with 24VDC motors to run direct from the battery? Would this eliminate any conversion loss from DC to AC, or that loss to small to consider?

  19. #14
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    28,744
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    8910

    Default

    Quote Originally Posted by JST View Post
    Since you are in Alaska, I expect your sunny day percentage is fairly low in winter. Not usually known as a hot solar area, looks like it is about the same latitude as Northern Scotland.
    Or the North of Germany. Alaska is "tall", North slope to Southernmost "tail", so "it depends".

    Solar power in Alaska - Wikipedia

    Wind, maybe?

    Wind power in Alaska - Wikipedia


    .. The genset is likely a decent idea.
    If... ya can get Diesel, "mains" natural gas, or decent storage & delivery of LPG, IC gen set could work well, year-round.

    Can't think of ANYTHING "off grid" nor even ON grid, as will be as cheap as the lower-48 average though.

    Alaska - State Energy Profile Analysis - U.S. Energy Information Administration (EIA)

  20. #15
    Join Date
    Mar 2006
    Location
    Vershire, Vermont
    Posts
    2,101
    Post Thanks / Like
    Likes (Given)
    1369
    Likes (Received)
    657

    Default

    Where in Alaska is huge. In the Aleutians? Very windy, amongst the windiest places in the nation. Wind in the winter, solar in the summer. Kotzebue, too. But if you're in a valley, wind ain't so good. Maybe hydro, again depending where you are, ice can be a factor.

    If you're far enough south, more panels. Panels are cheaper than batteries and last longer. Is your array set up with an MPPT charger? That can increase output 10-30% or so.

    If you can go wind, Bergey is the best off the shelf unit. If you want to build your own, Fieldlines.com: The Otherpower discussion board - Index is the place to go. Hugh Piggott DIY version works very well, but you do have to be willing to educate yourself and to keep after it. Once you learn to fish....

    Let us know where you are in Alaska and we'll be willing to speculate even more wildly

  21. #16
    Join Date
    Jun 2001
    Location
    St Louis
    Posts
    18,184
    Post Thanks / Like
    Likes (Given)
    1956
    Likes (Received)
    3087

    Default

    He's down the coast, look it up. In the "thin part" along Canada.

    That's still up at Hudson Bay type latitude, but well below the circle. Like I said, think North Scotland, Orkneys maybe.

    On the coast, fishing town, so possible fog and "ocean weather".

  22. Likes neilho, Milacron liked this post
  23. #17
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    28,744
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    8910

    Default

    Quote Originally Posted by JST View Post
    He's down the coast, look it up. In the "thin part" along Canada.

    That's still up at Hudson Bay type latitude, but well below the circle. Like I said, think North Scotland, Orkneys maybe.

    On the coast, fishing town, so possible fog and "ocean weather".
    Haven't had the Orkneys experience, but have been all OVER Iceland, more than just the one time. Perhaps the world's best at geothermal, the Islanders are, The proper name means "Isle land" or island, not "Ice land", BTW.

    Further ISTR it was an Islander who invented a type of wind turbine that needs no furling or feathering even in the most extreme of winds, nor is it all that vulnerable to icing.

    So yes, one can DO this off-grid basic survival craft workshop "thing". Island has smelted and cast aluminium on an industrial scale off geothermal power. I still have a couple of their "Look" pressure-cast items bought there over 30 years ago.

    It is just not likely to work very well without (at least) a 4:1 upscale if not 10:1 over what the OP came in the door with.

    PV isn't like just turning on a tap anywhere all that far from a Mexican desert or Luke AFB - blessed with very nearly all-year-round clear skies.

    PV efficiency and value-for-investment spend have gotten rather good. Even so, if mounted on Earth's surface, not out in space, the Sun cannot reach it "24" even where 7 X 365 is right close to reality.

    "PV" - "Pollyanna Voltaic".

    Photo-thermal is often far the better value-for-money and durability route.

  24. #18
    Join Date
    Nov 2008
    Location
    Madera county california usa
    Posts
    2,489
    Post Thanks / Like
    Likes (Given)
    21
    Likes (Received)
    622

    Default

    Batteries with some batteries then add some more

    Last switch had 10000 amp hours of batteries and has a 1000 amp load, came in handy when generator failed to start.

    Did engineer a solar plant on the roof to provide the full power needs of everything in battery but company wanted 3 year RTI so did not get to install it.

    Cycle service batteries good for short runs of high loads and float service long runs of lesser loads.

    Parallel strings of float batteries allow for long runs of high loads.

    Your loads are tiny in reality.

    What is budget for build and what are power budgets?

    Largest load for longest time.

    Daylight hours?

    Having large battery allows for running under no light as well as high starting currents.

    Tesla power walls already being used for similar use except for time shift.

    A local large warehouse size place installed a bunch of power wall industrial models on the roof (floor space is in use so roof) and during day plant runs on battery with utility available and charges at night when power cheap.

    Some local solar companies now doing same for homeowners where solar charges during day and battery is prime source for when peak needs greater than solar.

    Lots of ways to fleece the feline...

    You need to determine actual needs now and future then determine how to build it.

    Sent from my SAMSUNG-SM-G930A using Tapatalk

  25. #19
    Join Date
    Jan 2020
    Country
    UNITED STATES
    State/Province
    Alaska
    Posts
    5
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Default Southeast AK, 56 degrees n, annual avg 3.5 hours/day sun, supplies by boat only.

    Killer set of replies, thanks all- I like the imagination.
    I think a summery here is currently to add power instead of searching for higher efficiency.

    Generators are possible but sure, fuel, like everything is expensive(in AK) and I have to boat it in. The sun boats itself in, which I like, it also lets me hear the wolves howl once in a while. Our site isn't reliably windy, too far from any good streams (though hydro is THE way to go in this rainforest of course.) Essentially, power is either genset or solar.

    What I do know- for lighting, 24 VDC is terrific. epic-ally more efficient than running the inverter/AC LED's. you'll think I'm lying but I can get by on 4 watts total to light a 600sf house. This is using 24vdc LED strip lights with dimmer switches. To make a bright 600sf shop it will be more like 60 watts total- with 15 bulbs.

    I can expand the system, adding second inverter would get surge capacity to almost 12000 watts, but the battery to support that is BIG and would wipe out all $ for other changes to motors/machines.
    inverter is a Magnum MS PAE model, making 120/240v AC -it puts out a perfect 4KW all day long. It starts the 2 hp 9000w inrush saw, but it sure doesn't like it, and the saw (12" tablesaw) is already severely underpowered.

    DC Direct??
    Leeson makes motors up to at least 2hp in 24vdc. 2 hp at this low voltage is 70 amps. What is the typical application for such a motor, anyone have experience with a reliable make? right now my 240v 2 hp through the inverter is pulling more like 110 amps and hitting 300 inrush. (on the battery side at around 25v)
    Another (paired)inverter is 2 thousand, or I could buy two of these DC motors, but which would be better?)
    Thanks all, I was hoping this would be a fun thread!

  26. #20
    Join Date
    Jan 2020
    Country
    UNITED STATES
    State/Province
    Alaska
    Posts
    5
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Default

    incidentally, if I were to start the system over, and had more budget(spent budget on building), I'd do this: three stacked outback inverters each doing 3500 watts and synched to produce 3 phase. That would support machines up to at least 3 hp.
    Batt banks probably Silicon Salt (if it proves out) or maybe LifePO with something like 5 thousand usable watts at an acceptable depth of discharge.
    5 thousand watts of solar running through a high voltage MPPT controller or two.

    This would outpace my needs most of the year but if I want to use this shop in the fall, I should just move to Colorado!


Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •