possible starter system

BoFullerBoFuller Solar Expert Posts: 187 ✭✭✭
I'm tired of running the generator all the time. I am thinking about the following system. Please feel free to make recommendations or even tell me if something is stupid or dangerous.

3 - 200-240W panels - to be mounted flat on the roof of the travel trailer
A Xantrex C40DD charge controller
4 Trojan T-105 batteries
A Xantrex TR2412 inverter/charger
and probably a TriMetric battery meter

I have a 25 foot travel trailer on 40 acres with grid nowhere to be found.
NW AZ at 6200 feet elevation

TV, laptop, phone charger, 12v water pump, blender, lights, vacuum, furnace fan, occassional power tools and probably a 100W bulb in the utility shed to keep anything from freezing

I'm thinking of one of those metal utility sheds to put it all in - like 4' x 6'?

4 days a week - 2 people

Stove and fridge are propane although fridge needs electric for fans and thermostat

I have a 1000W and a 15000W generator for the A/C and table saw

Can I do all this for around $5000?
Too much of anything?
Too little of anything?
Thanks!
12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

«134

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,747 admin
    Re: possible starter system

    Backing up for a moment--Have you measured your AC loads with a Kill-a-Watt meter (or equivalent) yet? I.e., how many AC Watt*Hours or kWH per day is your average use?

    And, have you looked at all angles of conservation yet? Almost always cheaper to conserve a Watt*Hour than to generate a Watt*Hour.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BoFullerBoFuller Solar Expert Posts: 187 ✭✭✭
    Re: possible starter system

    Yes I have measured everything I could with my Kill-a watt meter. I get anywhere between 1500 and 2500 a day. On days that I know I'm going to be using power tools alot, I will fire up the generator to supplement, but for now I want to turn it off by 4:00 and make sure I still have power for the evening for TV, furnace motor, etc, as well as making breakfast without firing it up again so early in the morning.

    We are already used to conserving and running one thing at a time, but I expect our usage will increase as we spend more time there, so if I am a little heavy to begin with, I would think that is okay.

    If I have enough power, I would like to run a power cord out to the garage for lights and battery chargers. If not I will use the generator for that. I know that I do NOT want a system of less than 1.5Kwh per day.
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: possible starter system

    Here's an instant problem with your proposed configuration:

    450 Amp hours of battery @ 12 Volts = maximum 2700 Watt hours, not including system losses.
    Run a 100 Watt bulb for 24 hours = 2400 Watt hours.
    There goes all your power to one light bulb. Maybe you could put it on a thermostat to mitigate its power use, but chances are it will still cut in to your available power by a significant amount. Electricity is a lousy way to heat things.

    Otherwise it looks viable, but I'd recommend you go for four 200+ Watt panels (closer to 800 - 1000 Watt array) and an MPPT type charge controller. My system has about the same Watt hour capacity (albeit from a 24 Volt system) and it is marginal when the weather goes gray. Winter time use is not possible here either, so check your daylight harvest potential for your area with PV Watts.
  • solar_davesolar_dave Solar Expert Posts: 2,392 ✭✭✭✭
    Re: possible starter system

    He has a better shot at acceptable winter sun in AZ and 6500 ft elevation.
  • BoFullerBoFuller Solar Expert Posts: 187 ✭✭✭
    Re: possible starter system

    Okay, scratch the 100 watt bulb and go for more insulation.
    4 panels and Mppt
    Thanks for the input!
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: possible starter system

    i think i can agree with your system and the additions coot made of using another pv and an mppt controller. i think you may be right around the $5000 point if not a bit over and that also is considering the things you left out like disconnects, breakers, wire, mounts, etc. now in the future you may want to get a sine wave inverter for items that have electric motors on them and maybe expand the system with 2 more pvs and 2 more batteries to give you a bit more wiggle room on your consumption. the batteries can be added too if not more than a year or so on the age of the originals and providing they were not abused. let the bulk of any little things that need charged like phones and such go on the generator along with some of your other big items. it's a timing thing for some of the loads too.
  • cptdondocptdondo Solar Expert Posts: 99 ✭✭✭
    Re: possible starter system
    BoFuller wrote: »
    Okay, scratch the 100 watt bulb and go for more insulation.

    Check out the SolarHeat group on yahoo as well. Lots of stuff you can do to gather heat.
  • BoFullerBoFuller Solar Expert Posts: 187 ✭✭✭
    Re: possible starter system

    I was wondering..... One of my concerns is not having to run the generator so late in the day or so early in the morning, but I don't mind running it at midday.

    Would I possibly be better off increasing the batteries instead of the solar panels (leave it at 3-200w panels and up my batteries to 6x or even 8x, and then using the generator to assist the panels or to top them off each day that I am there. Then the panels would be sufficient for maintaing them while I am gone.

    Just thinking... I may be way off.
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

  • BoFullerBoFuller Solar Expert Posts: 187 ✭✭✭
    Re: possible starter system
    BoFuller wrote: »
    I was wondering..... One of my concerns is not having to run the generator so late in the day or so early in the morning, but I don't mind running it at midday.

    Would I possibly be better off increasing the batteries instead of the solar panels (leave it at 3-200w panels and up my batteries to 6 or even 8 ), and then using the generator to assist the panels or to top them off each day that I am there. Then the panels would be sufficient for maintaing them while I am gone.

    Just thinking... I may be way off.

    I don't know why that sunglass thing is showing up. I typed the number eight. ???? I tried editing, but I can't get it to change.
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

  • BB.BB. Super Moderators, Administrators Posts: 32,747 admin
    Re: possible starter system

    I will fix the sunglasses thing--but the combination of "8 )" (without the space between "8" and ")" is a keyboard short cut for the "cool" face 8).

    Two ways around it... Put a space (or other character between the 8 and parenthesis, or click the check mark for "Disable smilies in text" to not have it do an auto convert.

    The reason for suggesting running the genset in the early AM is fuel economy/optimum use of solar energy.

    Basically, the battery bank will take "full charging" current if below ~80-90% state of charge. And with generators, they tend to be more fuel efficient (and burn cleaner) if operating at 50% of rated motor load or higher... So, charging a "low battery bank" with maximum rated/available current from your AC charger/genset will give you good kWH/Gallon fuel economy.

    If you were, for example, to charge in the middle of the day, you probably have current available from both solar array and genset power. The optimum charging current (from a solar PV point of view) is around 5%-13% rate of charge, and for an AC charge controller/genset, the maximum useful current is probably upwards of 25% rate of charge (i.e., 100 AH at 20 Hour Rated battery bank would be; 5-13 amps and up to 25 amps).

    So if the battery bank is at 80% state of charge, you have 10% current from the solar panels, then you fire up the genset, it is very possible if the genset AC charger attempts another 10% rate of charge (20% total), within a short period of time, the battery will increase to "absorb" voltage setpoint for the chargers... Basically, the battery will attempt to limit current to 10% or less current flow. And the solar/genset AC chargers will start cutting back on current flow.

    Since chargers are different, perhaps the solar will taper current back (not smart, because this is the "free" solar power that is being replaced with "expensive fuel" charging). Or, the AC charger will taper back, generator loading will fall below 50% rated power output, but fuel flow will remain at ~50% of rated fuel flow--So less power going into the battery bank with same fuel flow means poorer fuel economy.

    Now, some gensets are fairly fuel efficient at lower output power (Honda euX000i family down to ~25% of rated output, slow turning diesels are supposed to be more fuel efficient at lower output power)--But that is against the issue that diesel (and to a lesser extent gasoline) generators tend to carbon up valves and combustion chambers, wet stack (diesel), and/or glaze cylinder walls.

    So--the above is why some of us suggest here that running your genset into a discharged battery bank (50%-75% state of charge) and bring the bank back >80% state of charge in the early AM, and then let the solar finish off the charging the rest of the day.

    Of course, actual power needs, battery state of charge, weather forecast/sunny weather or not, optional loads (water pumping, shop tools, etc.), will all help you decide whether or not to run your genset in the AM/middle of the day too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BoFullerBoFuller Solar Expert Posts: 187 ✭✭✭
    Re: possible starter system
    BB. wrote: »
    So--the above is why some of us suggest here that running your genset into a discharged battery bank (50%-75% state of charge) and bring the bank back >80% state of charge in the early AM, and then let the solar finish off the charging the rest of the day.

    Of course, actual power needs, battery state of charge, weather forecast/sunny weather or not, optional loads (water pumping, shop tools, etc.), will all help you decide whether or not to run your genset in the AM/middle of the day too.

    -Bill

    That makes perfect sense. I have no problem running the gen from 9 to 11 and letting the solar take over.

    But what about my theory of using more batteries and less panels, as long as I charge them at the proper time of day.
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

  • BoFullerBoFuller Solar Expert Posts: 187 ✭✭✭
    Re: possible starter system
    BB. wrote: »
    I will fix the sunglasses thing--but the combination of "8 )" (without the space between "8" and ")" is a keyboard short cut for the "cool" face 8).

    Two ways around it... Put a space (or other character between the 8 and parenthesis, or click the check mark for "Disable smilies in text" to not have it do an auto convert.

    -Bill

    :blush: LMAO

    Thanks!
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

  • BB.BB. Super Moderators, Administrators Posts: 32,747 admin
    Re: possible starter system

    We tend to recommend more panels and less batteries (in general).

    A big battery bank has higher losses, takes more average and peak energy to properly recharge, and costs more to replace (over time and/or if there is a Oh-Heck situation when somebody left a load on then went on a two week trip and killed the battery bank).

    I would only go with a larger battery bank if generator use/fuel is expensive/difficult to justify (typically during the 3 months of winter).

    Keeping battery bank smaller also means you can use a smaller generator and possibly a smaller solar array.

    Too large of battery bank (too small of solar array, no or too small genset) can age the batteries faster (the longer they spend at less than ~75% state of charge, the faster they will sulfate and die).

    There are some things you can do to help--A few people here really like tracking solar arrays. Lower peak charging current but longer hours during the day--and they find they have very good battery life (aka poster Dave Sparks).

    There are many different ways to slice and dice these systems.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: possible starter system
    BoFuller wrote: »
    But what about my theory of using more batteries and less panels, as long as I charge them at the proper time of day.

    That's the recipe for doing solar wrong. :roll:

    Use the right amount of batteries to suit your load requirements.
    Use the right amount of charging to keep them properly recharged, even if that means "bulking" with a generator until you can afford enough panels.
    If the system is to be left on its own for extended periods of time you must have enough solar to at least maintain battery Voltage.

    Lots and lots of batteries a one little solar panel does not work. Not ever. Every system I've ever had to fix for people has been because of that mistake. Really.
  • BoFullerBoFuller Solar Expert Posts: 187 ✭✭✭
    Re: possible starter system

    OK, fine,

    4 - 200-240W panels - to be mounted flat on the roof of the travel trailer
    A Xantrex MPPT60 charge controller
    4 Trojan T-105 batteries
    A Xantrex TR2412 inverter/charger
    and a TriMetric battery meter

    Thanks!

    What's the determining factor when deciding whether to go 12V or 24?
    Distance is not a problem here. I can put everything very close to the trailer.
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: possible starter system

    There's a couple of factors for choosing 24 Volt over 12 Volt. One is the total Amp hours you need to store. This is due to the current limitations of charge controllers. The same current at double the Voltage can handle twice the stored Watt hour capacity. The other would be the maximum current draw expected on the system. If your loads stay below 1kW most of the time 12 Volts can handle that fine. But if you have consistently high Wattage being used 24 Volts becomes attractive for the same current vs. power reasons. Usually it's the stored capacity need that will induce you to change up.
  • BoFullerBoFuller Solar Expert Posts: 187 ✭✭✭
    Re: possible starter system

    Thanks for the help. I'm sure I'll have a million more questions once I actually start assembling this.
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

  • BoFullerBoFuller Solar Expert Posts: 187 ✭✭✭
    Re: possible starter system

    I'm getting closer to actually starting this system. I want to go over the setup process again to fine tune it. When I go to the Ranch this weekend and take my Kill-a-meter, I have a problem. I have measured the TV, the blender, the electric blanket, microwave, phone charger, and computer. Pretty simple. How do I measure the water pump when it is direct wired? And the refrigerator? And the fan for the furnace? And the 12 volt lights? And how do I measure the phantom load that has run the batteries down when supposedly nothing is on? A couple little lights are always on down by the electric box. Is there a way to measure the phantom load out at the battery? Do I need to get a Trimetric meter first?
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

  • BB.BB. Super Moderators, Administrators Posts: 32,747 admin
    Re: possible starter system

    Dang, three times I have lost my almost completed post here...

    Anyway, short and sweet:
    Use kill-a-watt and Doc Watson for plug-in loads.

    Use the Current Clamp Meter to estimate large/hardwired loads (may overestimate power draws for AC circuits).

    Use TED and family to hardwire monitoring for whole house/large circuit power usage.

    Phantom loads, there "are none" for solar. You need to know all of your power usage--Including Inverters which may draw 6-30 watts (or even more)--Can be significant if you leave inverter on 24x7.

    Some off-grid inverters include "search" mode--Run at much lower power until a >6 watt AC load is detected. Then turns on until loads are turned off (room lighting, computer turned on, TV, etc.).

    If you already have an off-grid system--Battery Monitors are great tools. Besides monitoring your battery bank estimated state of charge (easy for spouse, kids, guests to better understand running the off-grid system)--You can use the Battery Monitor to measure/estimate your loads too (everything off at night, turn on one load at a time and read meter. For larger/cycling loads, let load run for an hour or so during normal cycling).

    Quit and post before I drop another post.

    -Bill

    Use the Current Clamp meter to meaure current without you having to open circuits and wire in a current meter (and exposing you to high voltage/energy). You can open a panel/box and just clamp on on of the wires to measure current (safely).

    Note that AC power is "complex". A current clamp meter may overestimate your power used.

    Technically:

    Power = Voltage * Current * Power Factor
    VA (Volt Amps) = Voltage * Current

    Generators, inverters, wiring, and breakers "care" about Volts*Amps.

    Batteries powering the inverter only "care" about Power.

    PF~1.0 for DC loads, "Power Factor Corrected" (PFC) AC Loads, and Resistive AC loads.

    PV ~0.6-0.7 for CFL lighting, motors, and many electronic devices.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: possible starter system
    BoFuller wrote: »
    What's the determining factor when deciding whether to go 12V or 24?
    Distance is not a problem here. I can put everything very close to the trailer.

    Let me add a couple of things to Cariboocoot's answer. You are planning to use four 6 volt batteries. They will contain the same amount of energy whether you hook them up in series (24 volts) or series/parallel (12 volts). There will be many less things to go wrong if you put your batteries in series (24 volts).
    I suggest you read: http://forum.solar-electric.com/showthread.php?14674

    Another thing to consider is expandability. You will be in much better position to take the next step if you start with 24 volts.

    The only thing I see in favor of 12 volts is the wider availability of 12 volt loads (lights, appliances, pumps, etc). Some folks like to use 12 volt loads (rather than 115 volt AC) because there is no inverter efficiency loss. Another way around that inverter loss is to use a second, smaller inverter for those small loads, and turn on the big inverter only for the larger loads.
    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BoFullerBoFuller Solar Expert Posts: 187 ✭✭✭
    Re: possible starter system

    I did some experimenting when at my property this past weekend. I plugged the shore line into the Kill-a-watt and then plugged it into the generator. Then I went into the trailer and turned everything off and went out to read the meter;
    .54 amps; 40 watts; and 66VA - by the way, what is VA?
    That seems really high for nothing, but I guess it was trying to charge the batteries.
    Nothing running: .54 amps; 40 watts; 66 VA
    furnace running: 2.60 amps; 194 watts; 314 VA
    all the lights (nothing else): 4.22 amps; 325 watts; 513 VA
    microwave: 15.5 amps; 1680 watts; 1750 VA
    refrigerator: 3.19; 375 watts; 381 VA
    To get what each of these use, I would subtract the .54 amp; 40 watts; and 66VA; the reading I got for nothing being on. Right?

    Then I zeroed out the meter and left it in for 24 hours. It got down to 17, so the furnace ran a lot. At the end of the 24 hours it read 3.17 KW

    The refrigerator runs on propane, I just tested the electric mode to see what it would draw.
    I watched TV for a couple hours, and was on my laptop for a few hours, so I think the bulk of that 3.17 KW was the furnace fan.

    I'll do the same test in about a month when the furnace will be used much less. I think instead of gearing up for a 3kw system, I need to put a wood burning stove in the trailer and get by nicely with 1.5 to 2 KW

    Am I thinking clearly?
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

  • BoFullerBoFuller Solar Expert Posts: 187 ✭✭✭
    Re: possible starter system
    BoFuller wrote: »
    I did some experimenting when at my property this past weekend. I plugged the shore line into the Kill-a-watt and then plugged it into the generator. Then I went into the trailer and turned everything off and went out to read the meter;
    .54 amps; 40 watts; and 66VA - by the way, what is VA?
    That seems really high for nothing, but I guess it was trying to charge the batteries.
    Nothing running: .54 amps; 40 watts; 66 VA
    furnace running: 2.60 amps; 194 watts; 314 VA
    all the lights (nothing else): 4.22 amps; 325 watts; 513 VA
    microwave: 15.5 amps; 1680 watts; 1750 VA
    refrigerator: 3.19; 375 watts; 381 VA
    To get what each of these use, I would subtract the .54 amp; 40 watts; and 66VA; the reading I got for nothing being on. Right?

    Then I zeroed out the meter and left it in for 24 hours. It got down to 17, so the furnace ran a lot. At the end of the 24 hours it read 3.17 KW

    The refrigerator runs on propane, I just tested the electric mode to see what it would draw.
    I watched TV for a couple hours, and was on my laptop for a few hours, so I think the bulk of that 3.17 KW was the furnace fan.

    I'll do the same test in about a month when the furnace will be used much less. I think instead of gearing up for a 3kw system, I need to put a wood burning stove in the trailer and get by nicely with 1.5 to 2 KW

    Am I thinking clearly?

    Can anyone tell me if any of my numbers are accurate or was it a bad idea to plug the Kill-a Watt directly into the generator?
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

  • BB.BB. Super Moderators, Administrators Posts: 32,747 admin
    Re: possible starter system

    Sorry,

    Missed your questions earlier...
    BoFuller wrote: »
    I did some experimenting when at my property this past weekend. I plugged the shore line into the Kill-a-watt and then plugged it into the generator. Then I went into the trailer and turned everything off and went out to read the meter;
    .54 amps; 40 watts; and 66VA - by the way, what is VA?

    Power = Volts * Amps * Power Factor

    Power Factor is, more or less, how "efficiently" the current is used by the device... An analogy or two:

    First: You tie a rope to a railroad car and pull with a truck. Cosine (0 degrees) = 1.0 -- Basically, all of the force on the rope from the truck is pulling the rail car forward.

    Now, put the truck off the side (60 degrees). Cosine (60 degrees) = 0.5 -- In this case only 1/2 of the force on the rope is pulling the rail car forward, and the other 1/2 is pulling the car to the side. So, if you want to pull the rail car forward with 1,000 lbs of force, you have to pull on the rope with 2,000 lbs of force. So--the rope has to be 2x as strong because of the off-angle pull... Here the "linear" PF is like the current into a motor--Inductive current "lags" the voltage by XX degrees (cos angle).

    Cosine (degrees between voltage and current is equal to PF Power Factor).

    The second, same rail car and truck, but the truck pulls for 1 second at 2,000 lbs, and 1 second at zero lbs. The average pull over time is 1,000 lbs, but because of the "jerkiness" of the pull, the rope has to be 2x as strong. PF also equals the "non-linear" linear current wave forms for electronic power supplies.

    So, more or less, the "Watts" for the Kill-a-Watt meter is the voltage*Current*PF that is doing "real work". And, roughly, this is the power coming from the battery.

    VA (volt amps) is the total current (with respect to voltage) that is carried on the AC wiring. So--In this case, a "poor" Factor of 0.5 would require 2x heavier wire and 2x larger inverter for "proper and safe" operation.

    Different electrical devices have different "current profiles". Induction motors tend to have PF around 0.67 or so. This can be corrected with a "motor run" capacitor (not to be confused with a "motor start" capacitor--different animal and mixing them up will cause problems).

    Standard CFL (compact florescent lamps) have a power factor sometimes as low as 0.5 (and cannot be "corrected" with a simple motor run capacitor because of the "jerkyness" of the waveform--not sine wave but a series of current peaks) .... This means that the wiring and inverter have to be 2x larger... However the power from the battery to run the CFL is still 13 watts (vs 26 VA for this arbitrary comparison).

    It does get more complex--Many inverters and smaller gensets are rated such that Watts=VA ... You cannot exceed either rating. And if you have a bunch of "poor" PF devices (motors+CFLs+many computers), then your 1,000 watt inverter may be only capable of supplying a maximum of ~670 Watts of load before it overloads/pops a fuse:

    • Power = Volts * Amps * PF (usually, for DC we assume PF=1.0 -- But in real life, that is not true)
    • Power = 120 Volts * 10 amps * 1.0 PF = 1,200 Watts
    • VA = Volts * Amps = 120 volts * 10 amps = 1,200 VA

    VS a poor power factor system:
    • Power = V*A*PF
    • P = 120 V * 10 A * 0.67 PF = 804 Watts
    • VA = V*A = 1,200 V * 10 A = 1,200 VA

    So, for the above load, your 1,200 watt inverter (or AC Generator) would only support 804 Watts of "work".

    AC math is very confusing--And I have forgotten most of it from my college days--But we can continue the discussion if you are interested and/or have more questions.
    That seems really high for nothing, but I guess it was trying to charge the batteries.
    Nothing running: .54 amps; 40 watts; 66 VA PF = 0.61
    furnace running: 2.60 amps; 194 watts; 314 VA PF = 0.62
    all the lights (nothing else): 4.22 amps; 325 watts; 513 VA PF = 0.63
    microwave: 15.5 amps; 1680 watts; 1750 VA PF = 0.96
    refrigerator: 3.19; 375 watts; 381 VA PF = 0.98

    So, you can see you have a mix of Power Factors here...

    To rate your inverter (or generator), you would add up all of VA numbers -- That will give you the Watt-VA rating of the inverter.

    And to figure out your battery and solar array sizing, you would add up all the watts * hours per day for each appliance and get the Watt*Hours for sizing.
    To get what each of these use, I would subtract the .54 amp; 40 watts; and 66VA; the reading I got for nothing being on. Right?

    The .54a/40watt/66VA is sometimes called a "vampire" load. There is something drawing 40 watts and you should figure out what it is. For a larger system, 40 watts * 24 hours per day can be a significant "leak/waste" of power (40w*24h=960WH)--That could be 400+ watts of solar panels (or more in winter) just for the "lost/wasted" power.
    Then I zeroed out the meter and left it in for 24 hours. It got down to 17, so the furnace ran a lot. At the end of the 24 hours it read 3.17 KW

    Is the "17" seventeen "Hours" of logged time on the KaW meter (instead of an even 24 hours)? If so, then, roughly, your 3.17 kW*HOURS (?) would be:
    • Furnace = 3.17 kWH * 24H/17H measurement = 4.48 kWH per 24 hour period

    If I understand correctly, that is a fair amount of power (central heating?). That fan (and igniter system) would be running:
    • 4,480 WH per day * 1/194 watt average load = 23 hours per day

    Of course, if I misunderstood the "17" -- I may be off some here (closer to 16 hours a day)... But that is still a lot of run time for central heat (at least in a temperate climate).

    This is why we suggest the KaW meter and looking for conservation opportunities first. If you can cut your power usage by 1/2 -- You can cut your Solar/Off grid power by 1/2 too.
    The refrigerator runs on propane, I just tested the electric mode to see what it would draw.
    I watched TV for a couple hours, and was on my laptop for a few hours, so I think the bulk of that 3.17 KW was the furnace fan.

    If the propane fridge uses an electric heater on DC/AC power--then they are very inefficient when running from electricity. If the propane fridge has a compressor of some sort--then the electrical usage will probably a lot more efficient.
    I'll do the same test in about a month when the furnace will be used much less. I think instead of gearing up for a 3kw system, I need to put a wood burning stove in the trailer and get by nicely with 1.5 to 2 KW

    Am I thinking clearly?

    Yes, you are on the right track--but you need to be very clear about what you are measuring and logging.

    And your winter usage is important.... Can't have you freezing in the name of saving a few (or a lot of) bucks on your off-grid power system.

    I am a little lost here--Are you on Grid Power and want to move off-grid (new land/cabin) or what?

    More or less, if you are using a Solar Power system for less than 9 months a year, then many times it makes more sense to use a propane fridge and keep your power needs very low and simple.

    Once you hit 9+ months a year residency--Then a full AC electric fridge, efficient heat, cooking, laptop computers, etc. makes more sense. Of grid solar can only store ~3 days of useful power--So if you don't use the electricity when it is "fresh"--then it is lost forever.

    Very different from a Grid Tied system where you can "store" power for up to a year with 1-year net metering (or even run a negative balance in parts of the billing cycle).

    Plugging a KaW meter into the genset was fine--The only issue is many models of the KaW meters do not have battery backup--So if you kill the genset (say overnight) the readings are lost--unless you log them just before you turn the genset off (same thing with an AC inverter going into search mode--it turns of the power for about 1 second at a time when "searching").

    Please feel free to ask more questions--this is a very confusing and complex subject to grasp the first time--But the more you talk/use it--the more natural it will become. Plus, my explanations probably get a bit wrapped around the axial too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: possible starter system

    very good analogy on the power factor bill. i've never heard it quite put that way before. on the one side would be inductive loading and the other is capacitive. the middle ground has the pf of 1.0 and it is also called resonant.

    boy, you guys out there don't know how much of an electronics education you get from this site.8)
  • BB.BB. Super Moderators, Administrators Posts: 32,747 admin
    Re: possible starter system

    Hi Niel,

    I think the capacitive leading current would be more the equivalent of pushing the rail car with the truck--But that is why analogies break down if you try and carry them too far--I am too tired tonight to figure out the inverse analogy fully. :blush:

    For those that remember vector algerbra--that is really what we are talking about here (adding vectors to get the resultant vectors).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: possible starter system
    BB. wrote: »
    Standard CFL (compact florescent lamps) have a power factor sometimes as low as 0.5 (and cannot be "corrected" with a simple motor run capacitor because of the "jerkyness" of the waveform--not sine wave but a series of current peaks) .... This means that the wiring and inverter have to be 2x larger... However the power from the battery to run the CFL is still 13 watts (vs 26 VA for this arbitrary comparison).
    <snip>
    To rate your inverter (or generator), you would add up all of VA numbers -- That will give you the Watt-VA rating of the inverter.

    And to figure out your battery and solar array sizing, you would add up all the watts * hours per day for each appliance and get the Watt*Hours for sizing.

    Bill, you've got me confused. I always thought (perhaps incorrectly) that the difference between the watts and the VA was dissipated in the wiring of the inverter or generator. If that energy is dissipated, then it must be accounted for when sizing the battery and array.
    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.BB. Super Moderators, Administrators Posts: 32,747 admin
    Re: possible starter system

    VA is not energy--It is both the "real" and "imaginary" current... Remember the analogy... Only the portion of the force that is moving the rail car forward is work. The force pulling the rail car sideways off the track has "no motion", so no work is being done.

    But, the force is still real--so the rope has to be strong enough to take the combined forces.

    Same things with VA--The volts and amps are still there. The wiring has to be able to take the higher Amps because of losses (I2R heating losses do not "care" about the real vs imaginary parts of the current). Same thing with other physical effects--Such as magnetization of the Iron in the transformers and Inductors--They saturate/circulate currents based on the VA, not the V*A*PF (Watts).

    So, it is not Power Lost = VA - Watts.... It is Total Power = Watts + I2R heating + magnetization losses + other losses + etc...

    Sort of make sense?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: possible starter system
    BB. wrote: »
    So, it is not Power Lost = VA - Watts.... It is Total Power = Watts + I2R heating + magnetization losses + other losses + etc...

    Sort of make sense?

    Theory and equations make perfect sense to me... I just don't have a sense for how large those losses are. I recall reading in another thread that the losses are great enough that power companies charge industrial customers for their power factor losses.
    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.BB. Super Moderators, Administrators Posts: 32,747 admin
    Re: possible starter system

    The losses we aim for in wiring are around 3% maximum.

    The losses charged for by utilities to commercial customers can be around 0.67 PF or 1/0.67 = 1.48x the kWH rate (this is the kVA or kVAR).

    The utility may charge based on pure kVAR or they may measure the worst 15 minute PF/kVAR in a month and charge for that (remember, many large commercial accounts charge for two elements... One is the actual power used, the other is "reservation" charges which is the worst 15 minute load kW or kVA in the last month/year--Typically, I have seen bill is about split between the two charges).

    For commercial power users, installing Power Factor Corrected equipment can save a lot of money (knock 1/3rd right off the top of the bill for motors). And managing peak loads can save a lot of money (or cost a lot if done wrong for 15 minute period).

    Also, it is very possible for the peak "load" to actually be a peak "source" if solar is involved... Remember solar only generates for 4-6 hours a day at peak values--So the average solar output may be higher than the average 15 minute load of the customer--driving up reservation charges. I posted an article here a while ago where some San Diego schools were finding their power bills went up with solar when reservation charges were added (plus cost of loans for installation, etc.).

    One person here said it is possible to pay 10's of thousands of dollars to engineers to review/model pay back models for industrial customers and solar installations. It is not simple.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BoFullerBoFuller Solar Expert Posts: 187 ✭✭✭
    Re: possible starter system
    BB. wrote: »
    Sorry,

    Missed your questions earlier...



    Power = Volts * Amps * Power Factor

    Power Factor is, more or less, how "efficiently" the current is used by the device... An analogy or two:

    First: You tie a rope to a railroad car and pull with a truck. Cosine (0 degrees) = 1.0 -- Basically, all of the force on the rope from the truck is pulling the rail car forward.

    Now, put the truck off the side (60 degrees). Cosine (60 degrees) = 0.5 -- In this case only 1/2 of the force on the rope is pulling the rail car forward, and the other 1/2 is pulling the car to the side. So, if you want to pull the rail car forward with 1,000 lbs of force, you have to pull on the rope with 2,000 lbs of force. So--the rope has to be 2x as strong because of the off-angle pull... Here the "linear" PF is like the current into a motor--Inductive current "lags" the voltage by XX degrees (cos angle).

    Cosine (degrees between voltage and current is equal to PF Power Factor).

    The second, same rail car and truck, but the truck pulls for 1 second at 2,000 lbs, and 1 second at zero lbs. The average pull over time is 1,000 lbs, but because of the "jerkiness" of the pull, the rope has to be 2x as strong. PF also equals the "non-linear" linear current wave forms for electronic power supplies.

    So, more or less, the "Watts" for the Kill-a-Watt meter is the voltage*Current*PF that is doing "real work". And, roughly, this is the power coming from the battery.

    VA (volt amps) is the total current (with respect to voltage) that is carried on the AC wiring. So--In this case, a "poor" Factor of 0.5 would require 2x heavier wire and 2x larger inverter for "proper and safe" operation.

    Different electrical devices have different "current profiles". Induction motors tend to have PF around 0.67 or so. This can be corrected with a "motor run" capacitor (not to be confused with a "motor start" capacitor--different animal and mixing them up will cause problems).

    Standard CFL (compact florescent lamps) have a power factor sometimes as low as 0.5 (and cannot be "corrected" with a simple motor run capacitor because of the "jerkyness" of the waveform--not sine wave but a series of current peaks) .... This means that the wiring and inverter have to be 2x larger... However the power from the battery to run the CFL is still 13 watts (vs 26 VA for this arbitrary comparison).

    It does get more complex--Many inverters and smaller gensets are rated such that Watts=VA ... You cannot exceed either rating. And if you have a bunch of "poor" PF devices (motors+CFLs+many computers), then your 1,000 watt inverter may be only capable of supplying a maximum of ~670 Watts of load before it overloads/pops a fuse:

    • Power = Volts * Amps * PF (usually, for DC we assume PF=1.0 -- But in real life, that is not true)
    • Power = 120 Volts * 10 amps * 1.0 PF = 1,200 Watts
    • VA = Volts * Amps = 120 volts * 10 amps = 1,200 VA

    VS a poor power factor system:
    • Power = V*A*PF
    • P = 120 V * 10 A * 0.67 PF = 804 Watts
    • VA = V*A = 1,200 V * 10 A = 1,200 VA

    So, for the above load, your 1,200 watt inverter (or AC Generator) would only support 804 Watts of "work".

    AC math is very confusing--And I have forgotten most of it from my college days--But we can continue the discussion if you are interested and/or have more questions.



    So, you can see you have a mix of Power Factors here...

    To rate your inverter (or generator), you would add up all of VA numbers -- That will give you the Watt-VA rating of the inverter.

    And to figure out your battery and solar array sizing, you would add up all the watts * hours per day for each appliance and get the Watt*Hours for sizing.



    The .54a/40watt/66VA is sometimes called a "vampire" load. There is something drawing 40 watts and you should figure out what it is. For a larger system, 40 watts * 24 hours per day can be a significant "leak/waste" of power (40w*24h=960WH)--That could be 400+ watts of solar panels (or more in winter) just for the "lost/wasted" power.



    Is the "17" seventeen "Hours" of logged time on the KaW meter (instead of an even 24 hours)? If so, then, roughly, your 3.17 kW*HOURS (?) would be:
    • Furnace = 3.17 kWH * 24H/17H measurement = 4.48 kWH per 24 hour period

    If I understand correctly, that is a fair amount of power (central heating?). That fan (and igniter system) would be running:
    • 4,480 WH per day * 1/194 watt average load = 23 hours per day

    Of course, if I misunderstood the "17" -- I may be off some here (closer to 16 hours a day)... But that is still a lot of run time for central heat (at least in a temperate climate).

    This is why we suggest the KaW meter and looking for conservation opportunities first. If you can cut your power usage by 1/2 -- You can cut your Solar/Off grid power by 1/2 too.



    If the propane fridge uses an electric heater on DC/AC power--then they are very inefficient when running from electricity. If the propane fridge has a compressor of some sort--then the electrical usage will probably a lot more efficient.



    Yes, you are on the right track--but you need to be very clear about what you are measuring and logging.

    And your winter usage is important.... Can't have you freezing in the name of saving a few (or a lot of) bucks on your off-grid power system.

    I am a little lost here--Are you on Grid Power and want to move off-grid (new land/cabin) or what?

    More or less, if you are using a Solar Power system for less than 9 months a year, then many times it makes more sense to use a propane fridge and keep your power needs very low and simple.

    Once you hit 9+ months a year residency--Then a full AC electric fridge, efficient heat, cooking, laptop computers, etc. makes more sense. Of grid solar can only store ~3 days of useful power--So if you don't use the electricity when it is "fresh"--then it is lost forever.

    Very different from a Grid Tied system where you can "store" power for up to a year with 1-year net metering (or even run a negative balance in parts of the billing cycle).

    Plugging a KaW meter into the genset was fine--The only issue is many models of the KaW meters do not have battery backup--So if you kill the genset (say overnight) the readings are lost--unless you log them just before you turn the genset off (same thing with an AC inverter going into search mode--it turns of the power for about 1 second at a time when "searching").

    Please feel free to ask more questions--this is a very confusing and complex subject to grasp the first time--But the more you talk/use it--the more natural it will become. Plus, my explanations probably get a bit wrapped around the axial too.

    -Bill

    I agree with the later comment about a fabulous education! And I like the example of the train. Thank you.

    The 17 was the temperature. I was stating that the reason the KW were so high was that it was so cold that the furnace ran a lot.
    This place is totally off-grid, no power lines for miles. We are building a retirement home there. The trailer is to stay in while we are there building, but that is not full-time. So for a solar setup, I don't need 3Kw yet. Maybe on the home, but not the trailer. While I may be there for a week or two at a time from April through October, I am not there more than a weekend at a time in the winter. So no need to worry about freezing. And even if we were there full-time, I would put a small wood-burning stove in instead of running that ineffeicient furnace.
    As far as the phantom load of .54, I don't think that is mostly phantom. I think the majority of it was the generator trying to charge the batteries? For testing purposes, could I disconnect the batteries and then do the same experiment? Can I fun the system with the generator with the batteries disconnected, or would that possibly damage something?

    Thanks for the help!
    Bo
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

Sign In or Register to comment.