Hello, looking for direction

The student · August 2013

Hello everyone, I am planning on moving to a location inside of the US next year that I will have to make my own power or run a generator and burn fuel. I have started looking into solar and wind generation for power. I am looking for information where to go to try and learn more. I know the cost of the system is proboly going to be 80K plus so knowing that I am wanting to do this with overkill, with top grade parts in the entire system. What I am wanting to know and do not the feasability of this this is a 200 amp system that can run strictly on battery power for 14 days. I will be in a harsh environment temps in the mid 90's in summer maybe 10 below without wind chill in winter. Winds in my area are almost daily but they range from 10 mph to 60 mph. I would like to use solar and a wind generator to try and have both sides of power production. It is common for storms to last in winter for 5 days or more, it is in the mountains elavation is 8K feet above sea level. The reason I am trying to run 14 days on pure battery is there maybe not enough or too much wind to generate or be dim sunlight conditions. So I would need 2800 amp capacity in batteries, 200 amp a day for 14 days?

I have read that most battery systems you do not want alot of batteries tied together on 1 string in a parallel circuit. I am looking at 48 volt system. 2 questions I have about batteries is would it be better to have forklift batteries that store 48V with a 20 hr AH capacity of 768 to limit the amount of batteries needed so the total number in the parallel circuit is less.Most of the batteries I have seen batteries used for this application are 2 volt units, would the forklift be better route since it would be 1 to store 48 volt instead of 24 2V batteries, so in the end it may be possible to reduce the amount of batteries and circuits needed.? How many batteries would be required to store power at 48 volts for a 2800 amp system if that is what I need.

I am trying to find out some sort of calculator so I will know how large of a wind generator is needed and how many solar panels. I was thinking about a 10KW wind generator and solar panels for the rest but since I know really nothing about this I very well could be out in left feild.

The size of the house will be 3K sq feet with all the goodies, ac included. I am going to build a work shop that will have tig welder, mig welder industrial size not what you get a home improvemnt store, 12 inch lathe,bridgeport mill, they will require either 220 or 440 ac 3 phase power. For hot water will be using electric hot water tanks 3 50 gal units.I dont think I will use all 200 amps a day but would like to have a over build if possible to avoid having lack of power issues or if I loose a battery the system is not down or on a reduced level of output. For heat will burn wood.

Let me say thank you ahead of time for your input and thoughts on this. I do not have the knowledge yet to know if this is feasible, so looking to the experts to try and give me some direction on what I need to look into to understand these systems.

Photowhit · August 2013

Re: Hello, looking for direction

You don't appear to have an understanding of power, "2800 amp capacity in batteries" Batteries can be described as having 2800 amps but you have to give the voltage with that to understand the amount of energy you can store in the battery. Even a modern well insulated home of 3000Sq feet, will likely use 20+ Kw during the summer, with A/C and 3 water heaters... 20,000 watts of 120v would be 167 amps at 120 volts or 416 amps at 48 volts for a 14 day reserve expecting NO other charging, 416x14 x 2(with out outside source of charging you'll not want to drain below 50%) would be a 11,640 Amp hour battery at 48 volts, this is outside of all practical reason. You need to look at what is practical...

icarus · August 2013

Re: Hello, looking for direction

Why on God's green earth would you use 3 ELECTRIC water heaters? Why not design a solar water heating system, which will e much cheaper per BTU than an off grid PV system! Or why not use hot water recovery heat pump, a technology that allows the A/C to run moe efficiently, AND, creates "free" hot water in the process?

It looks like you might use as much as 30-50 kwh/da. (WAG) and you want a battery that will give 14 days of autonomy? Do you have any idea how big ( and expensive) that is going to be ? At 50 kwh/day, witha 48 vdc battery, discharged to 50% that is going to be a battery in the 28,000 ah size! That is roughly equivilant to nearly 500 golf cart batteries, close to $70,000 just in batteries! That would need a 2800 amps of charge current (at 48 vdc) To charge such a battery you would need something on the order of 135,000wqtts of PV! At an installed price, at $5/Watt, of $675,000!

Do your self a favor, look into some of the hard realities of off grid living, look at cutting edge conservation technologies etc. every dollar you save in conservation will likely safe $10 in PV and related costs! In addition, as Photo suggests, learn and understandthe terms, like for example the difference between amps and amp/hours would be a very helpful start! And do some real world load calc estimates and see what you would really need for power!

Icarus

Ps if you use my nameplate rating/2*4, to make 50 kwh of power a day, you re going to need somewhere in the range of 25kw of PV. That might cost $125,000 in today's installed prices.

waynefromnscanada · August 2013

Re: Hello, looking for direction

A definite need to come back down to earth and start concentrating on just three things.
1)Conservation.
2) Conservation.
And finally #3: Conservation.
And no, we are NOT being sarcastic, we're being open and honest.

YehoshuaAgapao · August 2013

Re: Hello, looking for direction

Batteries are expensive and getting more expensive. PV is cheap and getting cheaper. I'd go PV heavy, and with your long winter storms, a nice diesel generator because diesel is much more hoardable than gasoline (diesels gens need preheating in cold climates though).

Do get a solar water heating system. Much more cost effective than using PV to power electric water heaters. If you need a massive system, just get 4-6 of the largest collectors you can find (flat plate is not for cold climates - need evacuated tube) and two 120 gallon storage tanks (one will have a heat exchanger in it). In your climate, a solar space heating system will probably be worthwhile too (larger than solar water heating systems). And a really good wood stove for your 5-day storms.

Here's some pseudo-kits that might help you get a grasp on what would be needed to accommodate your energy demand. It was copy/pasted from an earlier thread. These are largely lower battery reserve (18-36 hours) that will certainly need a generator during bad weather, so if you want a high battery reserve, the battery bank really need to be upsized. It is vital that you have enough PV for your daily demand and quite a then some or your batteries will be chronically undercharged, sulfate, and die an early death. You should take 30-40% off of the KWh range to account for your stormy winters with short sun hours. As you can see, cutting down your usage can save you a lot of dough.

Using BB's formula: AH*AbsorbVolts*(1/0.77)*(1/#Hrs)=PVWatts
Formula transformed to: AH*AbsorbVolts*(1/0.77)/PVWatts=#Hrs
The 0.77 constant is from Solar panels usually delivering about 80% of STC plus 4% losses from the charge controller and wiring.
For simplicity, only using 60-cell PV panels, which tend to range fro 225W to 260 W with most being 235, 240, or 245W. 60-cell panels are the most common and are very economical.
For simplicity, only using MPPT charge controllers that are max 150 volts open-circuit (Midnite Solar and Xantrex have >150Voc charge controllers available).
For simplicity, only Group 31, GC2 Golf Cart, or L16 batteries are considered. Other common battery setups include Group 24, Group 27, Group 8D, Industrial batteries, and forklift batteries.
PV KWh/day is computed at 1000W STC = 5KWh/day - somewhat conservative, but assumes a full-sun day and no shading for at least 8 hours per day. My system in Arizona produces 6.25KWh/day per 1000W STC in a full sun day
BattKWh is for 100% DoD. Rule of thumb is to plan for 50% DOD. Different brands/kinds of batteries of different DOD peak total-KWh life. Surrette prefers 60-70% DOD. Trojan prefers 20-30% DOD.
PV KWh/day and PV charge rate ranges are 225W per panel at the minimum and 260W per panel at the maximum.
Systems with more than two PV strings require a combiner box with overcurrent protection on each string. For 60-cell panels in strings of 1, 2, or 3, Midnite Solar MPNV6 with a 15-amp breaker for each string will work good.
These designs do not favor high battery reserves (high reserve systems will have a lower PV to AH ratio and have slower charge rates) so most will require or really prefer the presence of a generator or a grid connection or both. PV panels are cheap and getting cheaper and are the longer lived components in the systems. Batteries are expensive and getting more expensive and are among the shorter lived components in the system.

12 Volt Single Charge Controller Systems

#PV     StrSize #PVStr  PV Watts    PV KWh/day  BatVolt #MPPT CC    Inverter (Min)      Batteries           #BatStr BattAH  BattKWh PV Charge Rate
1       1       1       225-260     1.125-1.300 12      1 (20A)     300W Pure Sine      1x Group 31         1       130     1.56    9.35-10.81 hrs - Nominal
2       1       2       450-520     2.250-2.600 12      1 (45A)     600W Pure Sine      2x Golf Cart GC2    1       225     2.7     8.09-9.35 hrs - Near Cost Effective Maximum
2       1       2       450-520     2.250-2.600 12      1 (45A)     600W Pure Sine      2x Group 31         2       260     3.12    9.35-10.81 hrs - Nominal
3       1 or 3  3 or 1  675-780     3.375-3.900 12      1 (60A)     1000W Pure Sine     2x L16              1       400     4.8     9.59-11.08 hrs - Nominal
3       1 or 3  3 or 1  675-780     3.375-3.900 12      1 (60A)     1000W Pure Sine     4x Golf Cart GC2    2       450     5.4     10.79-12.47 hrs - Low-Nominal
4       1 or 2  4 or 2  900-1040    4.500-5.200 12      1 (80A)     1000W Pure Sine     2x L16              1       400     4.8     8.09-9.35 hrs - Near Cost Effective Maximum
4       1 or 2  4 or 2  900-1040    4.500-5.200 12      1 (80A)     1000W Pure Sine     4x Golf Cart GC2    2       450     5.4     8.09-9.35 hrs - Near Cost Effective Maximum

24 Volt Single Charge Controller Systems

#PV     StrSize #PVStr  PV Watts    PV KWh/day  BatVolt #MPPT CC    Inverter (Min)      Batteries           #BatStr BattAH  BattKWh PV Charge Rate
2       2       1       450-520     2.250-2.600 24      1 (20A)     600W Pure Sine      2x Group 31         1       130     3.12    9.35-10.81 hrs - Nominal
3       3       1       675-780     3.375-3.900 24      1 (30A)     1000W Pure Sine     4x Golf Cart GC2    1       225     5.4     10.79-12.47 hrs - Low-Nominal
3       3       1       675-780     3.375-3.900 24      1 (30A)     1000W Pure Sine     4x Group 31         2       260     6.24    12.46-14.41 hrs - Low
4       2       2       900-1040    4.500-5.200 24      1 (45A)     1000W Pure Sine     4x Golf Cart GC2    1       225     5.4     8.09-9.35 hrs - Near Cost Effective Maximum
6       2 or 3  3 or 2  1350-1560   6.750-7.800 24      1 (60A)     Outback FX/VFX      4x L16              1       400     9.6     9.59-11.08 hrs - Nominal
6       2 or 3  3 or 2  1350-1560   6.750-7.800 24      1 (60A)     Outback FX/VFX      8x Golf Cart GC2    2       450     10.8    10.79-12.47 hrs - Low-Nominal
8       2       4       1800-2080   9.00-10.400 24      1 (80A)     Outback FX/VFX      4x L16              1       400     9.6     7.19-8.31 hrs - At Cost Effective Maximum
8       2       4       1800-2080   9.00-10.400 24      1 (80A)     Outback FX/VFX      8x Golf Cart GC2    2       450     10.8    8.09-9.35 hrs - Near Cost Effective Maximum

48 Volt Single Charge Controller Systems

#PV     StrSize #PVStr  PV Watts    PV KWh/day  BatVolt #MPPT CC    Inverter (Min)      Batteries           #BatStr BattAH  BattKWh PV Charge Rate
3       3       1       675-780     3.375-3.900 48      1 (15A)     1000W Pure Sine     4x Group 31         1       130     6.24    12.46-14.41 hrs - Low
6       3       2       1350-1560   3.375-3.900 48      1 (30A)     Outback FX/VFX      8x Golf Cart GC2    1       225     10.8    10.79-12.47 hrs - Low-Nominal
6       3       2       1350-1560   6.750-7.800 48      1 (30A)     Outback FX/VFX      8x Group 31         2       260     12.48   12.46-14.41 hrs - Low
9       3       3       2025-2340   10.125-11.7 48      1 (45A)     Outback FX/VFX      8x Golf Cart GC2    1       225     10.8    7.19-8.31 hrs - At Cost Effective Maximum
9       3       3       2025-2340   10.125-11.7 48      1 (45A)     Outback FX/VFX      8x Group 31         2       260     12.48   8.31-9.60 hrs - Near Cost Effective Maximum
12      3       4       2700-3120   13.50-15.60 48      1 (60A)     Outback FX/VFX      8x L16              1       400     19.2    9.59-11.08 hrs - Nominal
12      3       4       2700-3120   13.50-15.60 48      1 (60A)     Outback FX/VFX      16x Golf Cart GC2   2       450     21.6    10.79-12.47 hrs - Low-Nominal
15      3       5       3375-3900   16.875-19.5 48      1 (80A)     Outback VFX         8x L16              1       400     19.2    7.67-8.87 hrs - At Cost Effective Maximum
15      3       5       3375-3900   16.875-19.5 48      1 (80A)     Outback VFX         16x Golf Cart GC2   2       450     21.6    8.63-9.97 hrs - Near Cost Effective Maximum

Large 48V multiple charge controller systems - These larger systems will be more likely to be grid-tied bi-modal systems (battery backup or mini-grid).

#PV     StrSize #PVStr  PV Watts    PV KWh/day  BatVolt #MPPT CC    Inverter (Min)      Batteries           #BatStr BattAH  BattKWh PV Charge Rate
24      3       8       5400-6240   27.00-31.20 48      2 (60A)     Outback Radian      16x L16             2       800     38.4    9.59-11.08 hrs - Nominal
                                                                    or Xantrex XW6048
30      3       10      6750-7800   33.75-39.00 48      2 (80A)     Outback Radian      16x L16             2       800     38.4    7.67-8.87 hrs - At Cost Effective Maximum
48      3       16      10800-12480 54.00-62.40 48      4 (60A)     2x Outback Radian   24x 2V L16          1       1200    57.6    7.19-8.31 hrs - At Cost Effective Maximum
                                                                    or 2x Xantrex XW6048
60      3       20      13500-15600 67.50-78.00 48      4 (80A)     2x Outback Radian   24x 2V L16          1       1200    57.6    5.75-6.64 hrs - Grid-Tie Aggressive
96      3       32      21600-24960 108.0-124.8 48      8 (60A)     3x Outback Radian   48x 2V L16          2       2400    115.2   7.19-8.31 hrs - At Cost Effective Maximum
                                                                    or 4x Xantrex XW6048
120     3       40      27000-31200 135.0-156.0 48      8 (80A)     4x Outback Radian   48x 2V L16          2       2400    115.2   5.75-6.64 hrs - Grid-Tie Aggressive

Hello, looking for direction

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