Load Estimation and Sizing

BleuSoleilBleuSoleil Registered Users Posts: 14
I am refining my system design and I'm looking for advice on sizing my batteries and array for a south Louisiana off grid project. I understand my household consumption is a bit high for a typical off grid application but since we are in Louisiana our credits total 80% of installed system cost so I have the luxury of oversizing and staying within a $50K budget(10K net)

I had previously estimated my peak loads to run at 15kW/day but have been cutting to the bone and now avg 9.68kW/day. ((7-8 weekdays 10 to 12 weekends) Breaks down as follows:

1250 w/day 32" LED TV and Satellite Avg.
300w/day ceiling fans
400w/day lights
375w/day microwave
86w/day ASKO W6222 Washing Machine
236w/day clothes dryer
472w/day dishwasher
24w/day alarm clock
1750w/day Septic Pump
165w/day computer
200w/day coffee maker
2500w/day dehumidifier
969w/day fridge
320w/day ERV ventilator
120w/day cell phone booster
265w/day router & modem
137w/day misc chargers etc.

I list my load estimation calculations as a final collection of data and not as a prelude to a discussion on conservation( I have cut as much as my wife will allow).

I am thinking of using the Sanyo HIT 215's and have a 15' x 47' roof facing true south at 22 degree pitch. I am considering using the Generac EcoGen 6kW generator to assist charging my batteries so as to shorten days of autonomy to 1.5 and also to use AGM' so my wife will never have to work with the batteries other than tightening occasionally.

My worst design month is December with 2.68 avg hours of isolation and annual avg is just under 5 hrs so I will likely have many "opportunity loads" to run in the summer months(mainly a Sanyo Mini Split AC).

So my questions for the experts here are :
1. Is the Sanyo a good choice for off grid?

2. What AGM batteries and inverter/controller combinations are best for this size system?

I have been reading these forums alot and have learned much but I still would appreciate some guidance.

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Load Estimation and Sizing

    My opinion, for what it's worth:

    You can save on power by running the gen when you need to do laundry or use other heavy loads. Also try to plan a little "load shifting" to make use of the "surplus" or "unharvested" solar power available after the batteries reach Float stage.

    Otherwise, the standard drill:
    Inverter size is dependent on peak draw at any one time. You've got some healthy loads there, and if more than one thing over 1 kW clicks on simultaneously ... Big inverter need.
    Second, your daily Watt hours will give you the base info for sizing the battery bank. At rough 10 kW hours per day, you're looking at a whole lot of battery. Over-all this looks like it should be a 48 Volt system, wherein you'd need a minimum of 400 Amp hours to provide that load (at 50% DOD). If you want to keep DOD down to 25% (thus giving a potential second day's supply without gen) it would be double.
    Third, you're going to need a sizable array to recharge that. Using the minimum bank size (go up to 450 as it fits with commonly available battery capacity) your looking at 3 kW or larger array. Definitely MPPT charge controller too.

    As for what specific equipment you should get, work out the details first then see what you can buy that fits the budget. Ultimately any good brand of batteries, inverter, controller, panels will work. It's just a matter of what you can get for the money. Cost per Amp hour on the batteries, cost per Watt on the panels.

    I wouldn't be too quick to jump for AGM's first off, as mistakes are easily made on a first system and they are not tolerant of such errors. Flooded cells really are not the maintenance nightmare some people make them out to be. If you do go with AGM's a battery monitor is a must.

    Again, just my opinion. Others may have different suggestions/ideas.
  • BB.BB. Super Moderators, Administrators Posts: 29,241 admin
    Re: Load Estimation and Sizing
    BleuSoleil wrote: »
    south Louisiana off grid project....Louisiana our credits total 80% of installed system cost

    Double check on the credits/rebates... Very few "local" rebates are available for Off-Grid installations (they are typically funded through utility taxes and fees--and therefore only usually apply to grid connected installations).

    In any case, get as iron clad guarantee in writing as you can--You probably don't want to be left holding a $50,000 bill because somebody changed their mind and/or that fund has been exhausted for the current fiscal year, etc.
    I had previously estimated my peak loads to run at 15kW/day but have been cutting to the bone and now avg 9.68kW/day. ((7-8 weekdays 10 to 12 weekends)

    Good deal on the energy savings... Always a great place to start before going solar.

    By the way, the units are Watt*Hours and kWatt*Hours (WH, kWH)...

    Watts is just a "rate" like miles per hour.

    I am assuming that you are talking about kWH here. But want to confirm... You numbers are fairly low in most areas (good conservation) but they are close enough the "watts" average load/rate that I want to be sure.

    And some seem a little high for WH usage...
    1250 w/day 32" LED TV and Satellite Avg.
    300w/day ceiling fans
    400w/day lights
    375w/day microwave
    86w/day ASKO W6222 Washing Machine [double check--250-1,000 WH/day?]
    236w/day clothes dryer
    472w/day dishwasher [using energy saver mode?--could be >1,000 WH per load]
    24w/day alarm clock
    1750w/day Septic Pump [is this air pump or water pump? If water, sounds high]
    165w/day computer [small laptop for this low energy usage?]
    200w/day coffee maker [20 minutes to make coffee every day?]
    2500w/day dehumidifier [may be low--can be real energy hog]
    969w/day fridge
    320w/day ERV ventilator [double check--may consume more energy if running many hours per day]
    120w/day cell phone booster
    265w/day router & modem
    137w/day misc chargers etc.
    I am thinking of using the Sanyo HIT 215's and have a 15' x 47' roof facing true south at 22 degree pitch. I am considering using the Generac EcoGen 6kW generator to assist charging my batteries so as to shorten days of autonomy to 1.5 and also to use AGM' so my wife will never have to work with the batteries other than tightening occasionally.
    My solar installer loves Sanyo HIT modules... I guess they are about the only modules he has never had a warranty return for. Not cheap.
    My worst design month is December with 2.68 avg hours of isolation and annual avg is just under 5 hrs so I will likely have many "opportunity loads" to run in the summer months(mainly a Sanyo Mini Split AC).

    Is the A/C in the above list (dehumidifier or something)?

    So you do not have too much problems with marine layer in your area? The solar surveys are only as good as their location... if you are on the coast and have more fog/low clouds than the reference station, your isolation will probably be less.
    So my questions for the experts here are :
    1. Is the Sanyo a good choice for off grid?
    The Sanyo seems to be well liked here so far... In heat pump mode (if you get that option), it appears that a few of them seem to draw a lot of power. One user here has designed a current/power limit switch which seems to have addressed his issues so far.
    2. What AGM batteries and inverter/controller combinations are best for this size system?

    Lets say you use 4 hours of sun for your "break even" number and 10kWH per day. Using the typical 0.59 derating factor for a AGM equipped battery bank and otherwise well designed:
    • 10,000 WH * 1/0.59 derating * 1/4 hours sun = 4,237 watts of solar panels to support your daily load
    Battery bank wise, assume 48 volt bank (large inverter/bank/array) system with 1.5 day of no-sun:
    • 10,000 WH * 1/0.85 inverter eff * 1/48 volts * 1.5 days of no sun * 1/0.50 max battery discharge = 735 AH @ 48 volt battery bank
    The maximum surge rating (inverter output) from the battery bank would be around (note this is for Flooded Cell Surge Current--AGM's can do much better--but I still like to be conservative):
    • 735 AH * 48 Volts * 0.85 inverter eff * 1/2.5 surge rating = 11,995 Watts surge
    And, the 5%, 10%, 13% recommended charging rule of thumb in Solar Panel rating:
    • 735 AH * 59 volts charging * 1/0.77 pv derating * 0.05 rate of charge = 2,816 Watts of solar panels
    • 735 AH * 59 volts charging * 1/0.77 pv derating * 0.10 rate of charge = 5,632 Watts
    • 735 AH * 59 volts charging * 1/0.77 pv derating * 0.13 rate of charge =7,321 Watts
    So, from the above sets of solar pv panel calculations, it would look like around 4,237 watts (solar array to support daily load) to 7,321 watts (more or less maximum cost effective solar array size) range for your solar array.

    Battery charger rating for your genset--around 5% to 30% (min recommended to maximum recommended charging setup) with 10% or so being a nice number:
    • 735 AH * 0.05 rate of charge = 36.75 Amp minimum
    • 735 AH * 0.10 rate of charge = 73.5 Amp nominal
    • 735 AH * 0.30 rate of charge = 200.5 Amp maximum practical
    For your 6kW genset--For a bunch of reasons, minimum/maximum loading on your genset:
    • 6,000 watts * 0.6 power factor * 0.80 charger efficiency * 1/59 volts = 48.8 amps maximum (worst case)
    • 6,000 watts * 0.95 power factor * 0.90 charger efficiency * 1/59 volts = 86.9 amps maximum (best case worst case):
    Depending on your choice of battery charger, the largest battery charger for a 6kW genset would be around 50-85 amps... If you get an integrated Inverter/Charger, many of those have power factor corrected battery chargers and higher efficiency than the standard off-the shelf battery chargers (50 vs 85 amps or so)... Also many of the integrated chargers include programmable maximum AC current draw--very handy to tune your charger to your exact generator/battery bank setup...

    Anyway, that is where I would start. Hope it makes sense.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,292 ✭✭✭✭✭
    Re: Load Estimation and Sizing

    I've heard many good things about the Sanyo Mini Split, but there is some debate about keeping the crankcase heater running all winter.

    Ditto on flooded batteries for the "learning set"

    Septic Pump - what is motor size and starting current 240V ?

    I don't see a well pump ?
    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 ,

  • BleuSoleilBleuSoleil Registered Users Posts: 14
    Re: Load Estimation and Sizing

    Mike, I neglected to list the well pump but it is included in my daily total WH of 9968. The well pump is 120v and draws 100WH daily. The septic pump is an aerator and and runs constantly at 73W(kill a watt verified)

    Bill, yes I meant to designate all as watt hours. The washing machine is very energy efficient rated at 100kW per year by Energy Star and I simply extrapolatedn that to watts per load and our usage of 2.5 loads per week and then came up with the daily portion thereof. I may have complicated my configurati0n b3ecause ot that washer which is 240v--that is not a typo it is the washer that takes 240 because it only accepts cold in and uses an element for cycles that call for hot water(which we don't use). This is the only 240 appliance in our home and now I understand that will complicate our inverter configuration.

    Yes, dishwasher always runs in energy saving mode. Again, it is an ASKO which is the most efficient out there.

    Computer is a Lenovo netbook so that figure is kill a watt verified average over three weeks of data.

    Coffee Maker--well we do love coffee but i will have to double check that one!!!

    The ERV draws 40w but it only runs 16 hrs per day at 50% duty(i.e. on timer to cyle on and off every 15 minutes).

    I did not list my Sanyo Mini Split in my load estimation because it will be seasonal use far removed from my worst design month. Our Summer insolation is 4.92 so I expect the days I will need to run the AC will be the days I will have plenty of power for "opportunity Loads" when the batteries are well satisfied. We live in a 1200 sq foot passive solar cottage that is sprayfoam sealed tight so this unit has performed very well and worst case in the summer is we would only need 1-2kWH/day in summer.

    You are correct the dehumidifier is oru biggest energy hog even with the highest pints per kW rating in that price range(EBAC Triton). We have it running on a humidistadt at 55%RH. Down here in the Bayou, humidity control was our biggest design concern of the house. We call it "air your can wear".

    We do not experience marine layer so much where we are ( about 5 miles north of lake pontchartrain.)

    Thank you for your battery calculations, I will review them in detail when I get home from work.


    The tax credits do indeed apply to off grid and the 50% state portion is without limit.
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: Load Estimation and Sizing

    The Sanyo HITs are expensive modules and usually chosen where space is limited. For the same money you could buy more regular mono or poli modules. The Canadian Solar Inc modules look to be pretty good for off-grid use because of their poor summer performance. This may seem a counter intuitive thing to say, but the worse a module does in summer, the better it does it winter - and for off-grid, it's winter that really counts for production.
  • BleuSoleilBleuSoleil Registered Users Posts: 14
    Re: Load Estimation and Sizing

    I should clarify. I was asking if the Sanyo HIT Panels are a good choice for off grid.

    I know for sure my Sanyo Mini Split AC is ! :D
  • PhotowhitPhotowhit Solar Expert Posts: 4,913 ✭✭✭✭
    Re: Load Estimation and Sizing

    As my mom ages, I've been curious about areas to move closer to our traditional home of North Florida, so when You said Lousiana has a 50% rebate, I went to check, and I just don't see it...

    Louisiana incentives

    Found it;

    50% of the first $25,000 of the cost of each system....

    Carryover Provisions:Excess credit is refundable
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • BleuSoleilBleuSoleil Registered Users Posts: 14
    Re: Load Estimation and Sizing
    50% of the first $25,000 of the cost of each system....

    The Louisiana Dept of Revenue has clarified that an inverter and other components may be classified as "shared components" and allows each PV string to be written up as a system. This makes 6kW or greater systems here a viable option for many.
  • henry1henry1 Solar Expert Posts: 51 ✭✭✭✭
    Re: Load Estimation and Sizing

    first off this a set of simple question where you might what to rethink some of the items for your place

    fist question
    do really need a dish washer for the place

    second question

    did you look at a 12.volt or other off grid fridge and freezer system that will help also

    third question

    think about the socalled rv models combo washer and dryer unit along with good weather hanging the cloths outside to help cut down on daily draw from the battie bank ..

    fourth question ..

    go back and look at some of the socalled enegry star rated operatering hours draws and see if you can find a better unit to replace ..

    Fifth question

    cooking stove and it load on the bank along with water heating for the place for showering and cleaning of the home ..


    also look at the computer gear that can be ran off 12.volt batties system as i picked out everything for the cabin to run off the 12volt system ..
  • BleuSoleilBleuSoleil Registered Users Posts: 14
    Re: Load Estimation and Sizing

    Great suggestions Henry but we have already completed our construction and all new appliances are installed and in use. This will be a full time residence and we are using conventional yet undersized appliances and every single item was researched for highest efficiencies. Always room for improvement ,however !
  • henry1henry1 Solar Expert Posts: 51 ✭✭✭✭
    Re: Load Estimation and Sizing

    i just went through my stuff late last night and redo some of the items that i moved into the socalled wish list and then reworked the numbers again and i was comeing out to just under a 940.watts a day

    the heavyest load are the day of laundry and cooking day and that shot up to 1600 watts a day and those two load are staggered so not on the same day i'm doing them ..

    I took out the freezer unit and add the laptop travel usb powered scanner and..hp.protable printer unit that can run off a cig lighter set up along with my laptop makes up the home office instead of a desktop computer ..

    I did make sure i had a cable modem to get the fastest speeds i need for downloading tv shows from hulu to watch on the 27.inch lcd flat screen tv

    The nice thing about useing the laptop as a way to watch tv without cable is that most of the shows i like are on the next day or after midnite and i watch them then when i get home in the morning
  • mike95490mike95490 Solar Expert Posts: 8,292 ✭✭✭✭✭
    Re: Load Estimation and Sizing

    Your Fridge is nearly 1KWh / day How can you "rework the list" to get .940KWh ?
    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 ,

  • BleuSoleilBleuSoleil Registered Users Posts: 14
    Re: Load Estimation and Sizing
    mike90045 wrote: »
    Your Fridge is nearly 1KWh / day How can you "rework the list" to get .940KWh ?

    Henry is not me. It was my fridge that is nearly 1KWh
  • henry1henry1 Solar Expert Posts: 51 ✭✭✭✭
    Re: Load Estimation and Sizing
    mike90045 wrote: »
    Your Fridge is nearly 1KWh / day How can you "rework the list" to get .940KWh ?

    it was me who said i have reworked the items going into my place to get the amount under 1000 watts a day without the useing the oven on the stove and the washing machine and those two unit are useing diff days of the week


    here is some basic thing i have started to pratice for when i move to the off grid place and i'm praticeing these things now ..

    wait intill i have a full load before putting into the laundry now so it once a week i do laundry

    use a small cable modem to surf the internet and watch tv through hulu and few other websites and gotten rid of the sat dish ..

    wash the dish by hand instead of the dish washer running in the place

    since i'm single most of my meal prep time is less than 8 to 12 mins total a meal for cooking of the meal useing the single burner of the stove and the mircowave oven to cook the meal

    when makeing the morning cup of tea for me to drink i mainly use a single burner of the electric stove i have installed in the place to make hot water for me to use ..in the morning i make a large pot of tea and that last for a while or in the winter time a cup of hot chocolater here or there dureing the cold nights there in the mountains


    when i do bake it once a week not every day like most people as part of the plan i have i bake once a week of three loafs of bread and three diff desserts that day and then the oven is not used the rest of the week ..

    i put a kill a watt meter on every device i want to take with me to the new place to see there numbers to see if i did plan the right sized system for the place

    i also made sure that every last appliance that i picked that was 110.volt powered i study long and hard on this area and i picked the most the enegry star rated appliances i found to put into the place

    also picking my home office set up i went with a laptop and protable printer and scanner that all can work off a 12.volt cig ligther set up .. the laptop doubles as the tv computer system ..

    once i find a show on hulu i like i downloaded and it plays on the flat screen through the cable set up from the computer to the tv for my tv watching enjoyment when i do watch tv

    these are some of the things i learned to do for the move to a off grid house i have planned here in the future..
  • mike95490mike95490 Solar Expert Posts: 8,292 ✭✭✭✭✭
    Re: Load Estimation and Sizing
    henry1 wrote: »
    ...when makeing the morning cup of tea for me to drink i mainly use a single burner of the electric stove i have installed in the place to make hot water for me to use ..in the morning i make a large pot of tea and that last for a while or in the winter time a cup of hot chocolater here or there dureing the cold nights there in the mountains ....

    Look at an electric tea (water) kettle or an induction hot plate, instead of an electric stove. They are MUCH more efficient at heating only the pan and contents, instead of an electric element the pan sits upon, and only gets 40% of the wattage.
    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 ,

  • henry1henry1 Solar Expert Posts: 51 ✭✭✭✭
    Re: Load Estimation and Sizing

    your going to think this was a little stange to do ..But when i first thought about going compeletely off grid i started to keep track of how long it took to make up meals on a burner of the stove with a pen and paper ..

    i would take a digtal stopwatch and start the stop watch and make the meal then stop the stopwatch at the moment the meal hit the plate and i was putting the pot or pan into the sink for washing ..

    i keeped tracked of how long it took to make each meal i make in my socalled meal plan
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