Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

laura1933laura1933 Registered Users Posts: 8
I'm sure you've met or heard me a million times and in a million ways. But i really need some ones and advice. I want an off grid system so I emailed some people explaining what I needed told them I that I am on a very limited budget told them what my daily output is now which is 650 Wh/d. Even sugested forklift batteries as I had heard/read that they could be more economical. Any way long story short and all that, here are the cheapest options so far;
We could supply the following 6kWp off grid Solar PV systems; By the way I should have said that I am in England now but will be moving to Spain. So can some one any one help me build this thing? ALL and I do mean ALL help will be much appreciated.
P.S
I'm in stitches, cracked a rib laughing (Is this really the price of a system minus batteries)

Option - 1
24 x Amerisolar 250W solar panels
2 x Outback FM80 MPPT Solar Charger (48V)
1 x Outback Radian 7kW (48V) Peak DC>AC Inverter

1 x Mounting kit (2 rows of 14 panels in portrait)

24 x 2V 1000AH Solar Batteries (48V System) (BATTERIES TO BE SUPPLIED BY THE CUSTOMER)
1 x All cables, clips, isolators needed for the installation
1 x Dedicated delivery within mainland UK (excluding the Highlands)

£11,550.00 inc VAT & Delivery



Option – 2

24 x Amerisolar 250W solar panels
2 x Outback FM80 MPPT Solar Charger (48V)
2 x Victron Phoenix 3kW (48V) Peak DC>AC Inverter

1 x Mounting kit (2 rows of 14 panels in portrait)

24 x 2V 1000AH Solar Batteries (48V System) (BATTERIES TO BE SUPPLIED BY THE CUSTOMER)
1 x All cables, clips, isolators needed for the installation
1 x Dedicated delivery within mainland UK (excluding the Highlands)

£10,695.00 inc VAT & Delivery.

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    Welcome to the forum Laura.

    I didn't get very far with the medical school stuff so I can't help with the brain transplant, but I'm not so bad with engineering. :p

    Not living on that side of the pond I can't advise on prices either, but I can give you some idea of what sort of equipment you'd need.

    First off there's that power requirement: 650 Watt hours per day? Are you sure? Not 6500 Watt hours? That sort of "factor of ten" error can be very expensive. Judging by the size of arrays in the examples given I'm thinking it's more likely 6.5 kW hours.

    Both show 1,000 Amp hour 48 Volt batteries. That would be up to 24 kW hours of stored power which doesn't fit with 6.5 kW hours daily use at all, unless someone was doing the "three days storage" mistake.

    That much battery would required two charge controllers because it would require 100 Amps for charging. Also at least 6234 Watts of PV. The 6kW arrays described would actually be on the small side, although perhaps not in Spain.

    Why would you need 6-7 kW of inverter?

    What a 6.5 kW hour daily system would look like:
    630-ish Amp hours of 48 Volt battery (25% DOD).
    One 80 Amp MPPT charge controller.
    4kW PV array.
    Inverter sized to meet maximum at-the-moment power needs.
    Appropriate mounting hardware, circuit protection, and wiring.

    Which I suppose brings us back to the venerable question: what are your loads?
    Without knowing accurately how many Watt hours are needed daily and what the maximum Watts need to be at any given time it's impossible to say what you actually need.
  • PhotowhitPhotowhit Solar Expert Posts: 5,014 ✭✭✭✭
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    Why do you want or need to be off grid? This has to do with off grid energy typically being much more expensive than grid tied solar or just connecting to the grid.

    If you find you still, need (or want) and off grid system, we usually like to ask 2 questions when beginning to talk with people about an off grid system. What are your energy needs? We have very conflicting information, Unless you have no need for a fridge, it's unlikely you can live on 650 watt hours. Even the system size doesn't work with 6500 watt hours (6.5 Kwhs)...

    Your system sizing might have to do with the 2nd question, where are you going to install this system, we need to know that to determine the amount of energy you can expect from your array (set of solar panels)
    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
  • mike95490mike95490 Solar Expert Posts: 8,435 ✭✭✭✭✭
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    Once installed, this will not be easy to move to Spain, or did I miss-read your message ?

    Mike
    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 ,

  • laura1933laura1933 Registered Users Posts: 8
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    Hi, Thank you all for your comments. As I said I am a novice about all things solar and I think that I did not explain clearly what my needs are.
    I live in the UK at the moment, the system that I want will be built in Spain.
    The information on costings are quotes supplied by a company that I approached.
    Hi Photowit nice to meet you. As I will be using most of the appliances that I have at the moment, I had a look at my electric bill to give a better idea of how much electricity I will need and it shows an annual usage of 5,205.38 kWh it does not show daily usage for some reason. Hope this information is helpful.
    Once again thank you all for your input.
  • PhotowhitPhotowhit Solar Expert Posts: 5,014 ✭✭✭✭
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!
    laura1933 wrote: »
    As I will be using most of the appliances that I have at the moment, I had a look at my electric bill to give a better idea of how much electricity I will need and it shows an annual usage of 5,205.38 kWh it does not show daily usage for some reason.

    Well daily usage during a year is easy 5,205 ÷ 365 = 14 kwh a day. This is a huge load for off grid solar. So is the property 'off grid'? is there no possibility of connecting to the electrical grid?

    In general off grid solar is MORE EXPENSIVE than grid electric with very minor exceptions. I likely run 14 kwh a day in the summer time, when I have long periods of sunshine and run an air conditioner continuously but only in a single bedroom. If I was to try to run 14kwhs in the winter I could not afford the system!

    I'd say the system was sized close to your needs, but unless your absolutely drawing the same power every day, it might even be undersized! I think Spain has some very good areas for solar insolation (sun shine...lol)

    Have you priced the battery bank yet? It's likely half again the quote on the rest of the system or more, and you will also want a dependable generator. Doubling your quote as a guesstimate would be a good idea, until you figure out what your situation will be.

    I know you've give your electric bill, but what are your heavy uses? Do you heat and or cool with electric? Likely to use more electric in Spain cooling? Do you heat electrically? could gas or wood heat be an option? water heating is the next largest loads in most systems could you use gas to heat water? The fridge is the last of the big 3 energy uses, could you switch out for a new inverter type fridge? Are you willing to convert a chest freezer into a fridge? Basically I'm asking if your willing to make changes to move to this property?
    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
  • laura1933laura1933 Registered Users Posts: 8
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    Hi Photowit,
    The usage I quoted is for the UK. Yes the property is off grid and I imagine I will have to make changes, for instance I will not be using an electric oven which in itself is expensive to run, low wattage light bulbs will be used, no dryer.
    So basically I will be using a fridge, freezer, washing machine, lighting and the odd appliance. About the batteries I can get new Forklift truck ones at a reasonable price, I just need help choosing the right one.
    I visited one of those solar calculation sites and input all the things that I would be using and the results are;
    Energy


    Energy usage (per day) 7.822 kWh
    Maximum (Peak) load 256 W
    Power from other sources (wind, hydro, etc) 0 Ah a day at 48 V


    Solar System


    System voltage 48 V
    Current required (factoring loss) 183 Ah at 48 V
    Solar Panels 32 × Solarfun 175Watt 24Volt Solar Module
    Solar Charge Controller 2 × Plasmatronics 40A Multi-voltage Solar charge controller
    Inverter 1 × Latronics Sinewave Inverter 600Watt 48Volt
    Days of battery backup 3 days
    Battery depth of discharge 50 %
    Battery bank required (factoring loss) 1098 Ah
    12 × Raylite Deep Cycle Battery 4V 1380Ah
  • PhotowhitPhotowhit Solar Expert Posts: 5,014 ✭✭✭✭
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    I would tend to add a bit for forgotten loads.

    Also the "Maximum (Peak) load 256 W" doesn't make sense, as it looks like the daily load spread across 24 hours, your washer will use more energy than this.

    The inverter looks like it was chosen using those numbers though, a 600 watt inverter, might not even serve a standard fridge, and if you ran anything with it I doubt it would function. I need a larger inverter to run more comfortably, I have an 1800 watt inverter, and I can kick it off if I run too may high drain appliances at once, washer and microwave and the fridge kicks on.

    I personally don't want a generator, but my unique(?) situation is my heavy drain is running an A/C in summer, and our heat normally comes with sunshine. While I have 3 days reserve(backup) in winter I have maybe 1 in summer. We just went through 7 days of minimal charging. I use less energy this time of year and was fine, but I did "load shift" I have a load of laundry to do and I also heat water with solar manually(not on a relay directed by charge controller yet!) so I didn't heat water and after 3 days (my luck warm shower after 3 days, use a low flow shower head with a switch to shut off when shampooing, these are more common in Europe so perhaps you're familiar!) I took a 'camper bath' and made an excuse to visit some good friends after a couple days and showered there.

    I'm a fan of forklift batteries, I suspect you understand they may require a bit more maintenance. Monthly equalizing and a bit more watering. also they can be discharged 80%, while I don't like to do it, some are routinely taken that low. if you chose to have a generator, you might find that you could halve the size of your battery bank and have a healthier system, while only needing to run the generator a few time a year.

    If your new to solar/off grid living, you might find it a bit intimidating, and it will take a little time to adjust, just be able to roll with the changes. It's not the same as reaching thoughtlessly for the light switch, though I find I do that more now with a larger system. I've even caught my self leaving a light on once in a while when I'm running around the house!
    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
  • AguarancherAguarancher Solar Expert Posts: 285 ✭✭✭
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    Don’t know where in Spain you will be located (you might want to specify) , but another member stephendv lives near Barbastro. You might want to read his blog for some real life experiences in the area. Good Luck and make a workable plan before you make your solar purchase.
    http://www.casanogaldelasbrujas.com
  • laura1933laura1933 Registered Users Posts: 8
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    Thanks Aquarancher. I will be located in Murcia.
  • BB.BB. Super Moderators, Administrators Posts: 29,644 admin
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    Laura,

    Just to give you some math that you can play with and start getting some prices for your system... Assume you will need around 4 kWatt*Hours per day (fridge+freezer+lights+deep well pump+clothes washer+computer+network+TV). And that you are reasonably energy efficient. Will use propane/other fuels for heating/hot water/cooking.

    For Murica Spain, fixed array tilted to your latitude (52 degrees from vertical):

    http://solarelectricityhandbook.com/solar-irradiance.html

    Murcia
    Average Solar Insolation figures


    Measured in kWh/m2/day onto a solar panel set at a 52° angle:
    (For best year-round performance)

    Jan
    Feb
    Mar
    Apr
    May
    Jun


    3.70
    4.27
    5.10
    5.44
    5.42
    5.97


    Jul
    Aug
    Sep
    Oct
    Nov
    Dec


    6.23
    5.78
    5.19
    4.28
    3.60
    3.29


    Full off grid home, 2 days of energy storage (no sun) and 50% maximum discharge (longer life for lead acid battery bank). Use 48 volts for relatively large off grid system:
    • 4,000 WH per day * 1/0.85 AC inverter efficiency * 1/48 volt battery bank * 2 days storage * 1/0.50 max discharge = 392 AH @ 48 volt battery bank
    (note any solar numbers +/- 10% range are "dead on" for solar predictions--I am just carrying out more digits so that you can follow the math and how I use the numbers)

    We can estimate the "practical" size of solar inverter for the battery bank... for a 392 AH @ 48 volt battery bank, that would be a maximum of ~3.92 kWatt AC inverter (call it 4 kWatt or ~1kWatt per 100 AH @ 48 volt battery bank capacity)--Any larger inverter for that size battery bank would be a waste (you would "kill the batteries" with any higher current draw on a lead acid flooded cell storage battery type bank).

    Next, we need to size the solar array... Two calculations. One is based on the size of the battery bank (larger battery bank, more solar array needed to meet charging requirements). Second is to size the array to the planned daily load.

    First based on battery bank capacity and 5% to 13% rate of charge:
    • 392 AH * 59 volts charging * 1/0.77 panel+solar charger deratings * 0.05 rate of charge = 1,502 Watt array minimum (suggested for weekend/seasonal cabin/home usage)
    • 392 AH * 59 volts charging * 1/0.77 panel+solar charger deratings * 0.05 rate of charge = 3,004 Watt array nominal (minimum recommended for a full time off grid home)
    • 392 AH * 59 volts charging * 1/0.77 panel+solar charger deratings * 0.05 rate of charge = 3,905 Watt array "cost effective" maximum (if you charge during day and use power at night)
    The second array calculation is based on how much power you use over 24 hour period. From looking at the hours of "noon time equivalent sun" in your area, planning on your "break even" point for solar vs running a genset to make up for bad weather/winter sun, ~4.0 hours per day would cover 9+ months of the year on solar only.
    • 4,000 WH per day * 1/0.52 system efficiency * 1/4.0 hours of sun = 1,923 Watt array minimum for "break even" solar vs genset.
    So--The suggested array for your system (based on my made up/suggested power usage) would be around 1,923 watt array minimum--And for a full time off grid home, I would suggest a 3,004 to 3,905 Watt array.

    A 3,004 Watt array and 4 hours of sun would generate around:
    • 3,004 Watt array * 0.52 system efficiency * 4.0 hours of sun per day = 6,248 Watt*Hours = 6.2 kWH per day for ~9+ months a year, minimum average
    Assuming that fuel costs are expensive in Spain/Europe, you will want to run your generator a minimum amount of hours per year. Also, you probably would want to run some extra loads during the summer day time (Air Conditioning, water pumping for irrigation, etc.)--So the "extra" summer energy can be used during the day (if there is good sun, run your "optional loads").

    My suggestion is to not "over size" your battery bank. Batteries are expensive, heavy, and need maintenance, plus they can drive up the size of your array and have additional losses (an old fork lift battery can use upwards of 1-2% per day of its storage capacity as self discharge). Ideally, you want to size the system to your needs/loads.

    If you want to avoid fuel usage for cooking/hot water... Look at solar hot water systems or even various "heat pump" systems (take the waste heat from an A/C system and use it to heat water, or there are Heat Pump based water heaters that are ~2-3x more efficient than standard "resistance" type water heaters:

    http://water.nyle.com/residential/ (US brand--I am sure you can find European brands that will work well for you)

    Neat thing about heat pump water heaters is that take hot air as input and output cold/dry air as "waste"--Great if you need A/C for your home... Not so good if you live in a colder region (in cold regions, heat pump water heaters need outside air to keep from over cooling the room/building they are in--especially in winter).

    In the end, how much energy you use is the result of a highly personal set of choices you will make. We can give you estimates as too how much power you will use--But they are little more than guesses. We have people here that live off a 300 Watt AC inverter and 4x golf cart batteries are are ecstatic over having any electricity at all without having to fire up a generator.

    And others run their full home+business entirely off of solar (plus generator usage in bad weather) will full A/C, additional water+pumps for fire fighting, etc...

    Even if the system generates 4kWatt*Hours per day in early November--You cannot use 4.000 kWH per day--Some days there will be a little more sun, others less... You should plan on using around 66-75% of your "predicted loads" as your "base load", and if you have the extra energy, then turn on some optional loads (cooking/canning, doing the wash, vacuuming, run some extra water into the cistern, etc.).

    Your first step should be to know your loads. And it is almost always cheaper to conserve power than it is to generate power. Refrigerator/Freezers, Computers, Well Pumps (and of course A/C and Heat pumps) are usually the huge consumers of power. Sometimes lighting can be too (lights for work, greenhouse, etc.).

    And do not spend too much on your first battery bank... It may be the "wrong size" for you (need larger/smaller after a few years of living there) and/or most people murder their first set of batteries (under charging, forget to water with distilled/filtered rain water, guests/kids come by for a visit and kill the battery bank by leaving everything turned on, using hair driers and curling irons, etc.). Your second (or third) bank, you will have learned more about your own needs and will be able to make better choices/take care of issues before they kill your bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • laura1933laura1933 Registered Users Posts: 8
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    Hi Bill,
    Thank you so much for your info and Input. Now I'll just have to get my maths hat on:grr
  • AguarancherAguarancher Solar Expert Posts: 285 ✭✭✭
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    You never want to buy used batteries. Batteries are the last thing to be purchased in setting up a new system as their life expectancy clock starts the day you receive them. It is also best to purchase batteries local if possible for both shipping costs and any future warranty issues.
  • jimindenverjimindenver Solar Expert Posts: 59 ✭✭
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    When I first got into solar I saw batteries on craigslist for incredibly low prices. Since then I have learned that if they let them sit partially discharged...oops. If they abused them and let them run too far down maybe just once or twice...oops. One person had 6 "brand new, never used" 6v batteries that he had bought for his golf cart. The thing is his cart needed 8v jars and all of the nuts, etc were missing from the 6v. Now will he tell you he tried to use them in the cart and probably even tried to charge them with the charger intended for the 8v batteries...NO. You may be buying some REALLY expensive cores.
  • BB.BB. Super Moderators, Administrators Posts: 29,644 admin
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    Do not buy any hardware until you understand the system you are trying to build... If you start purchasing bits and pieces before you pencil out a system--You will (probably) be very unhappy.

    Also, Jim says, batteries start aging the day they are built at the factory. Add if they have been sitting for more than 1 month without charging (for flooded cell), they will start to sulfate--And can be worth zero in as little as 6 months of sitting uncharged (AGM/Sealed batteries can store upwards of 6 months without charging). Add that batteries are heavy, and flooded cell batteries are hazardous items (filled with acid)--So shipping internationally can be a problem too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,435 ✭✭✭✭✭
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    have you gotten a bid to have utility power run to the house ?
    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 ,

  • laura1933laura1933 Registered Users Posts: 8
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    Hi Mike,
    The house has not been built yet, I am in talks with my architect. I am choosing not to use a company to supply and install the solar as I am on a very tight budget. What I would really like is some one to tell me what I need to be buy and then I could source it. People are throwing battery sizes and wattage at me and I am completely lost.:grr:cry:cry:
  • BB.BB. Super Moderators, Administrators Posts: 29,644 admin
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!

    Laura,

    Unfortunately, it is a bit like buying a vehicle... Vehicles run from motor cycles to cars to pickups to box vans to semi-tractors+trailers. You cannot buy a mini-cooper and grow it into a box van. And if you buy a semi-tractor, it will not make a good vehicle to go shopping in.

    You have several ways to go... You can build the house (conservation rules--lots of insulation, skylights, efficient appliances) and run the home on a genset for a month or so--Measure your loads and then install a system to support those loads (probably another month or so on a genset)...

    Or you can can build out a smaller system that meets a minimum set of needs (say 3.3 kWH per day for a base system, and if you have any special needs--Say a 2nd freezer, add ~1 kWH per day, etc.)... Buy "cheap" set of batteries and see how it goes for a couple of years (run more generator power as needed)--Then redesign the system (if needed), toss/sell the cheap batteries, and then buy/build the system that meets your needs.

    Or visit some folks around you that have solar and see how their systems and life style work for you... Then build accordingly.

    Power usage is the result of a highly personal set of choices. What works for me may not work for you.

    Let's look at your original quote and figure out how much power it would produce. Note that the price does not include batteries--In the USA that would be ~USD$10,000 worth of fork lift batteries that would last ~15-20 years (if well taken care of):
    24 x Amerisolar 250W solar panels
    2 x Outback FM80 MPPT Solar Charger (48V)
    1 x Outback Radian 7kW (48V) Peak DC>AC Inverter

    1 x Mounting kit (2 rows of 14 panels in portrait)

    24 x 2V 1000AH Solar Batteries (48V System) (BATTERIES TO BE SUPPLIED BY THE CUSTOMER)
    1 x All cables, clips, isolators needed for the installation
    1 x Dedicated delivery within mainland UK (excluding the Highlands)

    Using rules of thumbs for a "typical/optimum" off grid grid home:
    • 1,000 AH * 48 volt batteries * 1/2 days of no sun * 0.50 maximum battery discharge * 0.85 AC inverter eff = 10,200 WH = 10.2 kWH per day (306 kWH per month)
    That is a pretty large off grid power system... About 3x what I would call a minimum system of 3.3 kWH per day (and 3x as expensive). I could run my grid connected home off such a system very nicely.

    Looking at the solar array:
    • 24x 250 Watt panels * 0.77 panel+controller derating * 1/58 volts charging = ~80 amps peak charging current
    • 80 amps charging current / 1,000 AH battery bank = 8% rate of charge
    We recommend 5% to 13%+ rate of charge... 8% is a bit on the small side for a full time off grid home--10% to 13%+ rate of charge would be better (especially for tall/fork lift type batteries which usually need ~10% minimum rate of charge).

    If we assume 1.25x larger array for 10% rate of charge:
    24 panels * 1.25 larger (10% minimum charge) = 30 panel array (approximately) = 7,500 Watt array (nominal)

    Now, how much energy could such an array supply for 9+ months of the year? Using the Murica numbers from earlier in the thread:
    For Murica Spain, fixed array tilted to your latitude (52 degrees from vertical):

    http://solarelectricityhandbook.com/...rradiance.html

    Murcia
    Average Solar Insolation figures


    Measured in kWh/m2/day onto a solar panel set at a 52° angle:
    (For best year-round performance)

    Jan
    Feb
    Mar
    Apr
    May
    Jun


    3.70
    4.27
    5.10
    5.44
    5.42
    5.97


    Jul
    Aug
    Sep
    Oct
    Nov
    Dec


    6.23
    5.78
    5.19
    4.28
    3.60
    3.29


    The "break even month" (when you may need generator for bad weather) would be February at 4.27 hours of sun average (typical weather average of ~20 years usually). And lets use a 7,500 Watt array (10% rate of charge):
    • 7,500 Watt array * 0.52 average system efficiency * 4.27 hours of sun (Feb) = 16,653 WH = 16.7 kWH per day (500 kWH per month)
    You can run the math for summer and winter months to see where that puts you vs your power needs.

    A 1,000 AH @ 48 volt battery bank would supply:
    • 1,000 AH * 48 volts 0.85 inverter eff * 1/20 hour discharge rate = 2,040 Watts for 5 hours per night (average power)
    • 1,000 AH * 48 volts 0.85 inverter eff * 1/8 hour discharge rate = 5,100 Watts for 2 hours per night (recommended max continuous load)
    • 1,000 AH * 48 volts 0.85 inverter eff * 1/5 hour discharge rate = 8,160 Watts for minutes to hour or so (short term max load)
    • 1,000 AH * 48 volts 0.85 inverter eff * 1/2.5 hour discharge rate = 16,320 Watts for seconds to minutes (starting pump loads, etc.)

    So, your 6-7 kWatt of AC inverters looks practical for the battery bank you are looking at.

    Note that you will (on average) need to purchase new AC inverters and Solar Charge Controllers around every 10+ years. And a new battery bank after ~15 years (if good quality forklift batteries that have not been abused).

    Very roughly--On average assuming you use ~66% to 75% of your generated solar power (you cannot use 100% of solar power every day with an off grid solar power system):
    • 7,500 Watt array * 4.86 yearly average sun * 0.52 system eff * 365 days per year * 0.70 usage = 6,918,210 = 6,918 kWH per year
    Assume that you spend something like $10,000 USD to install the system:
    • ($20,000 for hardware + $10,000 for batteries + $10,000 labor to install + $10,000 for replacment inverter+controllers + $10,000 new battery bank) / (20 years * 6,918 kWH per year) = $0.43 per kWHour
    That is not bad at all for off grid power costs over 20 year life of system... Of course, I made some guesses and did the calculations in USD$--You need to do the same calculations in your currency and with your assumptions.

    Anyway--A different way of looking at your questions.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!
    laura1933 wrote: »
    Hi Mike,
    The house has not been built yet, I am in talks with my architect. I am choosing not to use a company to supply and install the solar as I am on a very tight budget. What I would really like is some one to tell me what I need to be buy and then I could source it. People are throwing battery sizes and wattage at me and I am completely lost.:grr:cry:cry:

    Are your sure? This is somewhat like saying: i cant afford a surgeon so im going to do my own brain tumor operation!

    Saw this bumper sticker in Providence MA. For most people its about right.

    Attachment not found.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • laura1933laura1933 Registered Users Posts: 8
    Re: Newbie Needs Help For Off Grid System Or Brain transplant. HELP PLEASE !!!!!
    zoneblue wrote: »
    Are your sure? This is somewhat like saying: i cant afford a surgeon so im going to do my own brain tumor operation!

    Saw this bumper sticker in Providence MA. For most people its about right.

    Attachment not found.

    Thank you Zoneblue, that's the problem. I can perform brain surgery but can work out battery values !!!!
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