Generator sizing for a hybrid grid-tie system

AceNZAceNZ Solar Expert Posts: 104 ✭✭✭✭
I'm thinking about adding a generator to my hybrid grid-tie system, and I would appreciate some advice regarding sizing. My goal is to increase the length of time I can run my house load in the event of an extended grid failure / outage / disaster.

Existing system specs:

Typical house load: appx. 19 kWh / day
Batteries: 925 AH @ 48V (8 x Trojan IND17-6V)
Panels: 6 kWp (30 x 200W Phono Solar PS200M-24/F)
Location: 41.3 S, 173.3 E
Mounting: 315 deg azimuth, 15 deg tilt
Inverter: Delta Solivia 5.0 AP G3 TR (5 kW max output)
Inverter/Charger: Victron Quattro 48/10000/140 (10 kVA max load, 140A max charger current)

I realize total runtime is ultimately dependent on both how much sun and fuel are available, but I'd also like to size the generator to minimize costs -- acquisition, operation and maintenance -- while maximizing reliability.

The first thing I'm trying to understand better, though, is sizing. I'm thinking of using the generator mainly to charge the batteries. Minimizing time-to-charge would require supporting 10% of C/20 = 90 AH @ 48V = 4.3 kW, plus the house load of roughly 1 kVA = 5.3 kVA. With appx 85% system efficiency and no offsets for solar input, that's 6.2 kVA. However, I could also charge with less current and a longer runtime, say 5% of C/20, which would drop the size requirement to 4.2 kVA.

Beyond that, I'm also interested in suggestions on how to optimize configuration settings for both exercise and failure switchover, since a hybrid setup isn't quite as straightforward as full off-grid.

Any thoughts?
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Comments

  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system

    How much do you want to spend on the generator ?
    What fuel - gasoline, LP, diesel ?

    In a grid down situation, will you really have sustained loads of 19KWh daily ? If you can cut loads back to what the battery can support overnight, using a small, quiet 2KW generator, will let you charge the batteries and power a few loads.

    Does your inverter have Generator Support ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • AceNZAceNZ Solar Expert Posts: 104 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    mike95490 wrote: »
    How much do you want to spend on the generator ?

    I don't have a fixed budget -- it really depends on features and functions.
    mike95490 wrote: »
    What fuel - gasoline, LP, diesel ?

    Prefer LPG. Diesel is second choice. Then gasoline. I've researched LPG quite a bit, though, and while possible, in the end I think it's a bigger hassle than I'm willing to invest.
    mike95490 wrote: »
    In a grid down situation, will you really have sustained loads of 19KWh daily ?

    I could cut back, but I'd like to design so that I don't have to if the system works as expected -- then cut back when the time comes, if it doesn't.

    In a grid-down situation, it's actually possible my loads could increase, since I would volunteer to supply power to my neighbors or for emergency crews, and so on.
    mike95490 wrote: »
    If you can cut loads back to what the battery can support overnight, using a small, quiet 2KW generator, will let you charge the batteries and power a few loads.

    The batteries can already support overnight loads. In fact, they do that pretty much every night.

    What if I don't cut the loads back?
    mike95490 wrote: »
    Does your inverter have Generator Support ?

    Yes. It has a second AC input. When power is present there, it takes priority over the other input (from the grid). The inverter also has a relay and associated firmware that can be used to start a generator based on battery voltage, SOC and/or AC load threshold.
  • AceNZAceNZ Solar Expert Posts: 104 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system

    Another way to look at it is that the generator needs to be able to put 19 kWh back into the batteries each day -- let's say with a maximum of about 8 hrs of generator run time. 19 kVA / appx 85% efficiency = 22.3 kVA / 8 hrs = 2.8 kVA.

    That's within the range of a Honda EU30is.

    I feel like I'm missing something. With a battery-based system, once you're past the threshold for minimal power generation for the day, is the main capacity-related trade-off really just kVA vs. runtime (up to the point where you reach maximum battery charge current)?

    I understand best fuel efficiency tends to be close to the peak rated output. Unfortunately, that's also the highest noise level, which is a factor for me. I'm guessing engine wear is higher at higher loads, too.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    AceNZ wrote: »
    Another way to look at it is that the generator needs to be able to put 19 kWh back into the batteries each day -- let's say with a maximum of about 8 hrs of generator run time. 19 kVA / appx 85% efficiency = 22.3 kVA / 8 hrs = 2.8 kVA.

    That's within the range of a Honda EU30is.

    I feel like I'm missing something. With a battery-based system, once you're past the threshold for minimal power generation for the day, is the main capacity-related trade-off really just kVA vs. runtime (up to the point where you reach maximum battery charge current)?

    I understand best fuel efficiency tends to be close to the peak rated output. Unfortunately, that's also the highest noise level, which is a factor for me. I'm guessing engine wear is higher at higher loads, too.
    What you understand is Old School Thinking about generators and charging, the Inverter Generator total different animal. A Honda eu 2000 will use 1 gallon a hour at rated output and 6-7 hours at 50% output. The key is to couple it to a variable charging system ( Inverter with Gen support ) and let it run. The other option is to have a pair and parallel them when you need the extra power. A EU 30is should be well within your window. You have to find the charging input that will allow the generator run in the ECO mode. In my case it's 5-6 amps charging input constant , I still can run loads ( ECO throttle takes care of them ), The charger output will go up and down with loading and if a big load comes on Generator Support will take care of it. It's all about finding the settings that make it all work together.

    Another thing that helps is to have a strategic charging strategy. Don't ever let your batteries get into a hole you can't dig out of within a run time you know. Set a level in your mind that you know your capabilities can reach. I know that I have to start charging at 60 % dod and in 6 charging hours I can get back to 80% and that 80 % will get me through the night and back to 60 % by morning. Once you slide too far down the hill, it will be much harder to recover. Power Management is all about knowing your capabilities and doing what you have to do. Fuel becomes a issue, but once you have a plan and know the consumption the plan uses, it's easy. 60 gallons is easy for me to keep rotated ( 20 gal in cans, 40 gal in vehicles ) I am good for a month + or 2 .
    .
  • AceNZAceNZ Solar Expert Posts: 104 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    What you understand is Old School Thinking about generators and charging, the Inverter Generator total different animal. A Honda eu 2000 will use 1 gallon a hour at rated output and 6-7 hours at 50% output. The key is to couple it to a variable charging system ( Inverter with Gen support ) and let it run. The other option is to have a pair and parallel them when you need the extra power. A EU 30is should be well within your window. You have to find the charging input that will allow the generator run in the ECO mode.

    Wow, 6 to 7 times the runtime with only a factor of two reduction in output. That's huge! Especially when combined with the noise factor, it suggests that I should aim for an eco-throttle capable unit with at least twice the capacity I really need -- or a pair of smaller units that can be teamed.

    Unfortunately, I'm pretty sure the diesel gen I've been looking at (Kubota PK10S) doesn't have an "eco" mode like that. In fact, fuel burned per kWh produced goes up as load goes down.

    Using the numbers above, it sounds like I could go with either two Honda EU30is units at 3 kVA each (having a spare would be nice) or a single EU65is at 6.5 kVA. In addition to redundancy, a pair of EU30is would be quieter than either the Kubota or the EU65is -- another big plus, due to city noise rules (not critical during a grid outage, but important the rest of the time, such as during exercise periods and so on).

    Comparative prices here are (yes, I know NZ prices are crazy):

    Honda EU30is -- US$4000 (add $720 for auto-start)
    Honda EU65is -- $7300 (add $720 for auto-start)
    Kubota 10 kVA with digital controller and 100L fuel tank (60 hrs runtime at low load) -- $10600
    In my case it's 5-6 amps charging input constant , I still can run loads ( ECO throttle takes care of them ), The charger output will go up and down with loading and if a big load comes on Generator Support will take care of it.

    The Victron Quattro has a mode they call "Power Assist," where the current drawn from an AC source (grid or gen) is limited, and spikes above that are provided by the batteries, up to the capacity of the Quattro (10 kVA). So it would be easy to keep the gen in eco mode, as long as it provides enough power to charge the batteries and drive the average house load at the same time.
    Another thing that helps is to have a strategic charging strategy. Don't ever let your batteries get into a hole you can't dig out of within a run time you know. Set a level in your mind that you know your capabilities can reach. I know that I have to start charging at 60 % dod and in 6 charging hours I can get back to 80% and that 80 % will get me through the night and back to 60 % by morning.

    Good advice. I'm currently using around 1% per hour at night. Bulk at 80A charges at roughly 4% per hour. Like so many other aspects of this system, I imagine it will take a little trial-and-error to help me narrow in on the right settings.
    Fuel becomes a issue, but once you have a plan and know the consumption the plan uses, it's easy. 60 gallons is easy for me to keep rotated ( 20 gal in cans, 40 gal in vehicles ) I am good for a month + or 2 .

    Harder for me with a gasoline-power generator, since my car uses diesel. In fact, one of the advantages of using diesel would be that the fuel tanks for the generator and the car could act as backups for each other. With gas, I'm probably limited to a few jerrycans.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Generator sizing for a hybrid grid-tie system

    You get the general Idea. The noise is proportional to the rpm, the Honda EU2000 is just idling along @ 5-6 amp output. I run it right outside my window and I can hardly hear it run. If it's running full throttle you can sure hear it.

    Could you rent / borrow a EU 30is from some place or someone to try it ?? I like having the pair better than one big one, the redundancy and keeping the use divided between them is a good thing. I have a 20 KW but that hog uses 2 + gallons a hour and I only run it anymore when I have to. I am a old dog with new thinking on charging, nothing wrong with long and slow.

    Wow, your pricing is high for sure. The EU3000 was more weight than I could deal with in a portable, like 140 lb. Electric start would be nice if it was in my day in, day out plan, but I don't need that for standby operation. I have a " Dog House " type shed welded out of 1/8" aluminum open on one end and a # 10 drop cord. I just wheel it in place, hook up the extended tank, put the cover over it and let it run.
    .
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system

    When you try the 'borrowed' inverter models, one point which you need to watch, is when the charger first kicks in and it cannot get enough input current...it will 'hunt' up and down as the electronics try to sync the current, then you find it is a 'just a tad too small' a unit... I have 2 different chargers that 'should ' have run, but stalled out the inverter gen set at start up, as both were 'testing' to see just how much current the battery needed or could take.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    westbranch wrote: »
    When you try the 'borrowed' inverter models, one point which you need to watch, is when the charger first kicks in and it cannot get enough input current...it will 'hunt' up and down as the electronics try to sync the current, then you find it is a 'just a tad too small' a unit... I have 2 different chargers that 'should ' have run, but stalled out the inverter gen set at start up, as both were 'testing' to see just how much current the battery needed or could take.
    Yeah, thats true. That is one reason I steered him to using it with the inverter and use it's charger. If they will work together you can limit the Input. It's always a big if to see if everything will work right, it takes some experimental time to work all the settings out. I usually start everything with the ECO off and after it settles down turn it on. Stand alone charger are fine and have their place, but if you can get it all integrated it's a joy.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system

    I agree, combined is a nice feature if you can match it with needs and $
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    westbranch wrote: »
    I agree, combined is a nice feature if you can match it with needs and $
    That said, I have a new Magnum Inverter in the box that I never could integrate into my system. No matter what you set the charger limit to it will go to 100% before it cut back to what you have it set at, say 50 % . Thats a killer on a small generator.
  • AceNZAceNZ Solar Expert Posts: 104 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    Could you rent / borrow a EU 30is from some place or someone to try it ??

    Good idea. Not sure, but I'll look around.
    westbranch wrote: »
    When you try the 'borrowed' inverter models, one point which you need to watch, is when the charger first kicks in and it cannot get enough input current...it will 'hunt' up and down as the electronics try to sync the current, then you find it is a 'just a tad too small' a unit...

    The Quattro has a feature called "Dynamic current limiter" that's supposed to address this problem. What it does is to limit the maximum current draw from the AC source (such as a generator) to a level below the specified maximum, and then increases the limit slowly as the load increases.

    The example they give in their documentation is: assume a 2 kVA generator, with the current limit set to 8A and Power Assist enabled. No loads are connected, and the batteries are fully charged, so no current is drawn from the generator. Then connect a 7A load. Normally, the Quattro wouldn't react, because that's below the 8A limit; the full load would immediately be presented to the generator, which would cause a voltage drop since the generator can't deliver it instantly. If the voltage drops below the AC low disconnect limit, the Quattro would switch back to inverter mode, disconnecting the generator from the load. With the Dynamic current limiter feature enabled, the effective AC input current would be lower than 8A, because the initial load was zero. In that case, connecting a 7A load would result in the Quattro starting in Power Assist mode, providing most of the load from the batteries. As the generator starts to supply power, the effective AC input current limit would increase to 8A, and the Quattro would stop filling the gap from the batteries, as the full load is presented to the generator.
  • AceNZAceNZ Solar Expert Posts: 104 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system

    Just got back from seeing and listening to a Kubota 10 kVA generator running at both full load and half-load. Very nice unit, I have to say. It's certainly much larger than the Hondas, of course. Not too loud on half-load. I would probably add a second muffler to reduce noise further.

    I keep bouncing back-and-forth between the diesel and gas units. Don't know why I thought this should be an easy choice, but it's not.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    AceNZ wrote: »
    Good idea. Not sure, but I'll look around.
    Even if you could find a smaller one or a Yamaha you'd be able to get a idea. It gets expensive doing trial and error. Sounds like your Inverter will do just fine. I unhooked all mine stand alone stuff once I got the integrated stuff working, it gives you 4-5 different variables working together. I couldn't ask for anything more.
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    A Honda eu 2000 will use 1 gallon a hour at rated output and 6-7 hours at 50% output.
    It does NOT use a gallon per hour at rated output.
    AceNZ wrote: »
    Wow, 6 to 7 times the runtime with only a factor of two reduction in output. That's huge!
    Don't believe everything your read on the internet:D

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    vtmaps wrote: »
    It does NOT use a gallon per hour at rated output.

    Don't believe everything your read on the internet:D

    --vtMaps
    Thats what you say, I know what mine uses, it might not be a gallon a hour, but it's close to it. Go test yours. You know that you can't believe everything people post here.
    .
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    Thats what you say, I know what mine uses, it might not be a gallon a hour, but it's close to it. Go test yours.

    Honda web-site claims:

    3.64 hours per gallon at rated load of 1,600 watts
    8.73 hours per gallon at 1/4 load

    I haven't accurately tested mine, but the honda specs don't seem too far off. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    vtmaps wrote: »
    Honda web-site claims:

    3.64 hours per gallon at rated load of 1,600 watts
    8.73 hours per gallon at 1/4 load

    I haven't accurately tested mine, but the honda specs don't seem too far off. --vtMaps
    I meant to say 3 hours to a gallon, but didn't, I stand corrected. I am to busy worrying about parallel strings of batteries today, any thoughts.
  • AceNZAceNZ Solar Expert Posts: 104 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    vtmaps wrote: »
    Honda web-site claims:

    3.64 hours per gallon at rated load of 1,600 watts
    8.73 hours per gallon at 1/4 load

    I haven't accurately tested mine, but the honda specs don't seem too far off. --vtMaps

    Or, put another way:
    5,824 Wh per gallon @ rated load
    3,492 Wh per gallon @ 1/4 load

    This makes more sense. Broadly speaking, the closer you can run to rated load, the more fuel efficient in terms of Wh generated. The tradeoff is more noise. Not sure about engine wear per Wh, but since maintenance is based on hours not watts or engine revolutions, I suspect higher loads may be better there as well (at least to a point).
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    AceNZ wrote: »
    Or, put another way:
    5,824 Wh per gallon @ rated load
    3,492 Wh per gallon @ 1/4 load

    This makes more sense. Broadly speaking, the closer you can run to rated load, the more fuel efficient in terms of Wh generated. The tradeoff is more noise. Not sure about engine wear per Wh, but since maintenance is based on hours not watts or engine revolutions, I suspect higher loads may be better there as well (at least to a point).
    What I didn't say was I have blown one of my pair up twice running it maxed out with a 75 amp charger, so my fuel consumption may be more than what they have listed. I have no clue if it's max load or the rated load. I have a extended run 3 gallon tank and I don't think I ever ran over 4-5 or so hours on it, there is no way it will run 9-10 hours on it good or bad PF. Period !!
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    AceNZ wrote: »
    Not sure about engine wear per Wh, but since maintenance is based on hours not watts or engine revolutions, I suspect higher loads may be better there as well (at least to a point).

    Actually, as I understand it, wear and maintenance have more to do with number of starts (especially cold starts) and operating temperature.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: Generator sizing for a hybrid grid-tie system
    AceNZ wrote: »
    Just got back from seeing and listening to a Kubota 10 kVA generator running at both full load and half-load. Very nice unit, I have to say. It's certainly much larger than the Hondas, of course. Not too loud on half-load. I would probably add a second muffler to reduce noise further.

    I keep bouncing back-and-forth between the diesel and gas units. Don't know why I thought this should be an easy choice, but it's not.

    A 10kVA kubota is a completely different beast to a Honda EU30i. Going back to your original requirements of cost effectiveness and use only in the case of a power outage I think the kubota is overkill for those needs. Just to recap and get this into perspective again:
    - You have 6kWp of solar which can be used in grid-down situations
    - The quattro can supply 10kW of peak power
    - You need 19kWh/day
    - You only need the generator for grid-down use, not full time off-grid duty

    From the above, would it be realistic to say that you're only going to be using the generator for less than 200 hours a year? If so, IMO all you need is a smallish Honda to keep the batteries charged in the rare(?) case that the grid fails during cloudy weather. In that case you'll need the gen to work at full load (or near full load) for a few hours to get the batts up to > 80% SoC. You can use the PV to do absorb, and the quatro can handle the high peak loads. So an EU style generator that is more fuel efficient at less than full load is a wasted investment IMO, because you'll never take advantage of that feature.
    A regular Honda with AVR in about the 2-5kW range should work fine. You can then run it at 80% load constantly.
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    AceNZ wrote: »
    Just got back from seeing and listening to a Kubota 10 kVA generator running at both full load and half-load.
    stephendv wrote: »
    I think the kubota is overkill for those needs.

    Based on what I understand of your needs, I agree with stephendv. Also, diesels do not like running at half load, especially in cold temperatures. If you go diesel, look at smaller units.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • AceNZAceNZ Solar Expert Posts: 104 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    stephendv wrote: »
    - You have 6kWp of solar which can be used in grid-down situations
    - The quattro can supply 10kW of peak power
    - You need 19kWh/day
    - You only need the generator for grid-down use, not full time off-grid duty

    Yes.
    stephendv wrote: »
    From the above, would it be realistic to say that you're only going to be using the generator for less than 200 hours a year?

    Sounds reasonable.
    stephendv wrote: »
    If so, IMO all you need is a smallish Honda to keep the batteries charged in the rare(?) case that the grid fails during cloudy weather.

    Or an extended outage, such as in an earthquake or other natural disaster.
    stephendv wrote: »
    In that case you'll need the gen to work at full load (or near full load) for a few hours to get the batts up to > 80% SoC.

    Yes, but of course one of the factors is what "a few" hours really means.
    stephendv wrote: »
    You can use the PV to do absorb,

    Maybe. Sort of.
    stephendv wrote: »
    and the quatro can handle the high peak loads.

    Yes.
    stephendv wrote: »
    So an EU style generator that is more fuel efficient at less than full load is a wasted investment IMO, because you'll never take advantage of that feature.

    Good point. With one EU30is, I would be running it at full load, not eco -- in which case its advantage on the noise side goes away. I could possibly run a pair of them, each in eco, but that costs in fuel consumption, and at that point cost-wise, it's not a big jump to the Kubota.
    stephendv wrote: »
    A regular Honda with AVR in about the 2-5kW range should work fine. You can then run it at 80% load constantly.

    They're noisy, though, aren't they?


    Rephrasing my original question:

    What's the best generator size to minimize acquisition cost, operation cost and noise, while maximizing fuel storage? For this application, is it better to charge long-and-slow, and short-and-fast?

    The maximum useful power would be: 925AH * 59V * (1/0.77) * 13% = 9.2 kVA + 0.8 kVA for house load = 10.0 kVA
    Minimum useful would be (19 kVAh charge in 8 hours): 19000 * (1/0.77) * (1/8 hours) = 3.1 kVA + 0.8 kVA for house load = 3.9 kVA

    So, another confirmation that a single EU30is would be too small.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    With one EU30is, I would be running it at full load, not eco -- in which case its advantage on the noise side goes away.

    Even at full load that EU3000i gen set is quiet!
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • jcheiljcheil Solar Expert Posts: 722 ✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    vtmaps wrote: »
    Honda web-site claims:

    3.64 hours per gallon at rated load of 1,600 watts
    8.73 hours per gallon at 1/4 load

    I haven't accurately tested mine, but the honda specs don't seem too far off. --vtMaps

    My friend has the 2000i and runs a 5000btu ac unit (550ish watts with compressor on) and he gets just about 8hrs on the 1.1gallon tank. So they are pretty accurate.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    jcheil wrote: »
    My friend has the 2000i and runs a 5000btu ac unit (550ish watts with compressor on) and he gets just about 8hrs on the 1.1gallon tank. So they are pretty accurate.
    Thats sounds pretty close at that level of output. I am still waiting on a post with some real numbers besides mine. You know you can't believe anything from the internet except what some post over and over.

    Attachment not found.
  • VicVic Solar Expert Posts: 3,171 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system

    To continue the small derailment;

    BC04, my EU 2000 will start and run a 6000 BTu A/C in Eco mode for about 8 hours on about 1 gallon of fuel. Usually, the first four hours the A/C runs continuously, and then cycles. Of course , this is not real exact data. And about once in every 100 compressor starts, the gen trips off due to excessive load (in Eco mode). Here, it is better to use the EU2000 to charge the batts, and let the inverters run the A/C.

    Ace, YES, these trade-offs can get involved.

    Have EU1000, 2000, 3000s and an EU6500 here. The 'sweetest' of them all is the EU3000 --relatively llarge tank, very, very quiet. The noise frequencies are less penetrating (to me than the EU2000, for example). These things are all subjective. The EU gensets are almost always a number of dB quieter than almost any other type of genset.

    IMHO, pairing Honda EU gensets is a bit of a kludge, and almost doubles the maintenance requirements, and must reduce the overall reliability, compared to a single larger unit. YES, EU2000s are much more portable than a 3000 or 6500.

    Diesel gensets have much better fuel economy vs load than do gasoline (and especially LPG) fueled gensets.

    Many, many trade-offs. Opinions, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    Vic wrote: »
    To continue the small derailment;

    BC04, my EU 2000 will start and run a 6000 BTu A/C in Eco mode for about 8 hours on about 1 gallon of fuel. Usually, the first four hours the A/C runs continuously, and then cycles. Of course , this is not real exact data. And about once in every 100 compressor starts, the gen trips off due to excessive load (in Eco mode). Here, it is better to use the EU2000 to charge the batts, and let the inverters run the A/C.
    Opinions, Vic
    Thats a hard one to figure with cycles. A kicker start capacitor will help with the drop out problems " Sometimes " It's trial and error. My charging scheme is to Charge off cycle, I set the Inverter so that it will 0 ( zero ) out the charging when the A/C is on and when it cycles the charger goes back to 100% of the amp setting, if there other loads the Generator Support will pick it all up. When I run the generator it's to use as much for loads as I can and charge with the remainder. The most overall sweet spot for a Honda EU 2000 is 800 watts on ECO throttle, it's where all the lines intersect.

    The point was I know what a Honda EU 2000 uses at rated output ( 1,600 watts ) and at Max load ( 2,000 watts ), It sure in not what Honda Publishes.
  • jcheiljcheil Solar Expert Posts: 722 ✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    Vic wrote: »
    Here, it is better to use the EU2000 to charge the batts, and let the inverters run the A/C.
    Vic

    I kinda do thing same thing with my little Champion 1400/1800.
    I use it to run an IOTA DLS-27-15 and just run my 5000BTU AC from the inverter.

    It ends up pretty much being a wash in the morning of what was drawn from the batteries vs what the DLS put back in, BUT the real benefit I get is that since the Champion is not an inverter generator, the wide fluctuations in voltage/frequency when the compressor is on vs off is really annoying and you (or at least I) can hear the slight variations in the fan motor speed when the generator is loaded with only the fan and it drives me crazy when trying to sleep.

    Sure there is likely a bit of inefficiency doing it that way, but I gotta think that it is cleaner power running the AC from my PSW inverter rather than directly from that little 'borderline voltage regulated" generator.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Generator sizing for a hybrid grid-tie system
    jcheil wrote: »
    I kinda do thing same thing with my little Champion 1400/1800.
    I use it to run an IOTA DLS-27-15 and just run my 5000BTU AC from the inverter.
    <snip>
    Sure there is likely a bit of inefficiency doing it that way, but I gotta think that it is cleaner power running the AC from my PSW inverter rather than directly from that little 'borderline voltage regulated" generator.

    Of course there is inefficiency going AC to DC to AC, but that's what an inverter type generator does. You've built an inverter generator from components, rather than just buying an all in one package like a honda inverter generator. Since you have components, you have much greater flexibility... for example, you can use your inverter (from batteries) without running the generator... its not easy to use your honda inverter without running its engine.

    btw, what you are doing is called 'DC coupling'. In general, DC coupling is not as efficient as AC coupling (such as gen support), but DC coupling tends to be very robust and allows a greater choice of components (mix and match brands of controllers, battery chargers, and inverters).

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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