looking to go off grid and looking for input

Crazy_Wolf1234

alright folks, like a lot of people I am wanting to get away from the $400 power bill. So with that in mind, I am looking for a way to do this with minimal space and maximum output. This is the issue. not enough finances for solar, looked into wind heavily and realized that the area I live in isn't very windy. what i'm looking at is this, since a wind turbine is essentially a(n) alternator. Can I use a 12v auto fan motor to drive a turbine or alternator and charge a bank of batteries that can run inverters to power my homes rooms individually say using a 3500w inverter per room for kitchen and laundry and 1500w inverters for remaining parts of the home. If this is possible, how would I hook up the system and what would I need

Thom

The best thing to do is Forget about small wind power . 

Thom

Johann

The best way to reduce equipment cost is to reduce power consumption, the same goes for your current power bill and usage.
Usually, grid power is cheaper than solar and batteries.
The other option would be grid tie, which feeds sun power into the net when the sun shines and does not include batteries, but will shut down your solar production when the net is down for safety or when the sun is not shining..

Sorry to tell you, a radiator fan motor would produce very little power compare what you want/need to use.

Photowhit

Crazy_Wolf1234 said:

alright folks, like a lot of people I am wanting to get away from the $400 power bill. So with that in mind, I am looking for a way to do this with minimal space and maximum output. This is the issue. not enough finances for solar, looked into wind heavily and realized that the area I live in isn't very windy. what i'm looking at is this, since a wind turbine is essentially a(n) alternator. Can I use a 12v auto fan motor to drive a turbine or alternator and charge a bank of batteries that can run inverters to power my homes rooms individually say using a 3500w inverter per room for kitchen and laundry and 1500w inverters for remaining parts of the home. If this is possible, how would I hook up the system and what would I need

Basically, if you're trying to do off grid to save money, don't. I don't know what you pay per Kwh, but I'm doing it about as cheaply as it can be done. Perhaps just a little cheaper now, but not much. I make sacrifices, maintaining my system is a thought every day. I have a small 900 sq ft place with average bills of @$70-80 outside of Winter electric heat and Summer AC before converting.

I now heat with wood, which is a bit of a chore. I currently only AC the back bedroom, though I could add a mini split to help with the main room. Even though I have automated some functions. Heating water with solar is a regular thought/concern.

After all this I might be as cheap as the grid if my battery lasts 15 years. Possible and I don't upgrade my inverter until the 10 year schedule, not likely as I had intended on replacing with a larger unit when I did the build.

Grid tied can be cost effective, but if you are not more concerned about environmental issues, look at reducing your use, improve insulation, put a gray water heater timer on your water heater, jacket your water heater. Have the electric company come out and do an energy audit. Take advantage of their programs to replace old appliances with new energy efficient models.

Crazy_Wolf1234

thank you folks for your thoughts. photowhit, with a place as small as yours I could offer you some ideas I was planning on doing for the wife and I when we down size from this huge home. I planned on useing a mixture of 12v wireing for lighting using interior cab lights for semi trucks. they are halogen bulbs and put out as much light as a 60w bulb. this means changing the bulb fixtures to accomodate but it can be done. the other is using inverters to power the rooms for tv, kitchen, laundry etc. as for your air conditioner situation, if you place a window unit in the attic space and hook it to a vent system going to each room from above you can easily cool your entire place. these are some of the things I planned to do for us. just a thought. have a great day.

Photowhit

Crazy_Wolf1234 said:

thank you folks for your thoughts. photowhit, with a place as small as yours I could offer you some ideas I was planning on doing for the wife and I when we down size from this huge home. I planned on useing a mixture of 12v wireing for lighting using interior cab lights for semi trucks. they are halogen bulbs and put out as much light as a 60w bulb. this means changing the bulb fixtures to accomodate but it can be done. the other is using inverters to power the rooms for tv, kitchen, laundry etc. as for your air conditioner situation, if you place a window unit in the attic space and hook it to a vent system going to each room from above you can easily cool your entire place. these are some of the things I planned to do for us. just a thought. have a great day.

Pretty much, no. It's not that easy. This is a huge place for most off grid. Even a large window air will not AC this place. and drawing over 1 KWh per hour and likely a 100% duty cycle, I would need a huge battery, not that my 1100 lb fork lift battery is tiny, but think 2x the size.

Wiring for 12 volt is pretty much a non starter, first I would have to create 12 volts, My system is 24 volt and should be 48 volt. Then I would have to rewire, as the installed 16 or 14 gauge would have too much voltage drop for most 12 volt applications (over 80 feet to the back.

If you had hopes of using a 12 volt inverter to run a large household, you might look into all the assorted problems this will create. Everything, from multiple string battery banks, to huge wires and po

Not sure what the "inverters" reference is referring to, but a single inverter, pretty much always makes more sense when you have ongoing loads such as a fridge and/or a freezer.

jonr

I suggest that a halogen bulb is never the right answer to saving energy.    I'd start by collecting data on exactly where your $400/mo is going (ie, break-down each device) and post it here for some energy saving ideas.

Crazy_Wolf1234

again thanks guys, that's why i'm here. I want to get off the grid completely in a small but modest home design for my wife and I. I was hoping to use power inverters like this https://www.amazon.com/Power-Bright-PW3500-12-Inverter-3500/dp/B000NHS9R6/ref=sr_1_1?ie=UTF8&qid=1472557771&sr=8-1&keywords=power+bright+pw3500-12 to power individual rooms much like breakers control certain areas of a house. instead of hooking all power directly into one pannel and going from there, I want to seperate each room as a unit and area to power making the load requirement smaller and more managable. Ideas please

Aguarancher

Without a UL listing on that inverter you will void your home owners policy for the fire that may be in your future..

BB.

A good starting point is to try for ~100 kWH per month (which may be a $20-$40 per month electric bill from the utility). That is enough for a very efficient smaller home with a near normal electric life (excluding electricity for heating and air conditioning). LED Lighting, refrigerator, well pump, washing machine, LED TV, laptop computer...

If you have need for A/C--It is possible to run that off grid these days--But you need to insulate well, site the house to avoid daytime heat--And if cold in winter, allow sun into windows.

It looks like you have electric stove in your home--While it can be done, you would be much better off using some sort of fuel (propane, etc.)--In general, electric heating (cooking, hot water, dryer, heating) is pretty expensive if done with solar. And there can be solar hot water/heating even if you get some snow on the ground (again, if you get enough sun where you are planning on building the home).

However, there are now exceptions. There are heat pump heating/cooling and heat pump water heaters that can make off grid electric life better. And a few folks have done the electric range. However--Unless you live in a very sunny region of the country, I would try to avoid electric cooking and other large electric loads. You just end up running a genset a bunch during the dark days of winter.

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

Indianapolis
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 50° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
2.87	3.46	4.18	4.57	4.80	5.24
Jul	Aug	Sep	Oct	Nov	Dec
5.40	5.15	5.21	4.42	3.05	2.56

I would suggest that less than ~4 hours of sun per day--That solar energy get expensive.

-Bill

mike95490

just make sure it's easy to replace those inverters when/if they fail, I'm sure they have a shorter life than major household players in the business

Crazy_Wolf1234

BB. said:

A good starting point is to try for ~100 kWH per month (which may be a $20-$40 per month electric bill from the utility). That is enough for a very efficient smaller home with a near normal electric life (excluding electricity for heating and air conditioning). LED Lighting, refrigerator, well pump, washing machine, LED TV, laptop computer...

If you have need for A/C--It is possible to run that off grid these days--But you need to insulate well, site the house to avoid daytime heat--And if cold in winter, allow sun into windows.

It looks like you have electric stove in your home--While it can be done, you would be much better off using some sort of fuel (propane, etc.)--In general, electric heating (cooking, hot water, dryer, heating) is pretty expensive if done with solar. And there can be solar hot water/heating even if you get some snow on the ground (again, if you get enough sun where you are planning on building the home).

However, there are now exceptions. There are heat pump heating/cooling and heat pump water heaters that can make off grid electric life better. And a few folks have done the electric range. However--Unless you live in a very sunny region of the country, I would try to avoid electric cooking and other large electric loads. You just end up running a genset a bunch during the dark days of winter.

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

Indianapolis
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 50° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
2.87	3.46	4.18	4.57	4.80	5.24
Jul	Aug	Sep	Oct	Nov	Dec
5.40	5.15	5.21	4.42	3.05	2.56

I would suggest that less than ~4 hours of sun per day--That solar energy get expensive.

-Bill

these are good points to take into mind. as for the electric stove in the image, the wife and i were thinking of using convection plates which use less power than the average electric range. though I won't have an oven, I can use a small toaster style oven or microwave when needed for baking style meals.

as for the air conditioner well we were looking into a buried plastic tank and airflow lines going from the box to the home and back so as to use the grounds natural coolness to help cool the home. if well insulated, this should help keep the home around 70* year round. as for heat, we were thinking either a wood furnace or electric fireplaces. we were leaning more towards the wood furnace type since they are more efficient for this area and getting fuel for it is often free because of storms knocking down trees.

I like the idea of LED lighting and am a skilled craftsman. I can make lighting fixtures that can handle LED bulbs and be stylish as well. as for the clothes dryer, well that would only be needed when it rains or in the winter as the wife likes to hang the clothes out. I would like to have a wind generator hooked to a small electric motor by belt an pulley instead of solar to provide the electricity to charge the batteries but not sure if it is possible to do this. I don't know if a charge controller meant for solar could be used to charge a battery system like what i'm looking to do. any ideas would be handy bill

Crazy_Wolf1234

Aguarancher said:

Without a UL listing on that inverter you will void your home owners policy for the fire that may be in your future..

this is a good point but the inverters have a UL listing which can be used for insurance info. as for the fire in the future, these units come with failsafe fuses that blow when voltage exceedes the limits. the only way a fire could happen in the home with this system is if the wrong gauge wire is used or if there is a short in the wireing and as for this issue this can happen even if I stay on the grid so no issue there either. also since the system is going to be seperate unit from the home any fire at the source will be contained apart from the home. thanks for the concern

Crazy_Wolf1234

jonr said:

I suggest that a halogen bulb is never the right answer to saving energy.    I'd start by collecting data on exactly where your $400/mo is going (ie, break-down each device) and post it here for some energy saving ideas.

the problem isn't the appliances, the problem is the teenagers/adults that are here. my kids ( oldest 20 ) is attending colledge and living at home. that in conjunction with the 18 year old living here also stay up all night on the computers and use lights. this house never shuts down. the wife and I want to down size when they move out and want to go off grid. since we both work and would not need to be home except in the evening we figure the power consumption would be dropped drastic in the future. check out the comments above for our ideas and post any comments needed

mike95490

If you MUST use electric for cooking, look into Induction hotplates.  They use the steel pan as the heating element, and have about a 90% heat transfer to the food, as opposed to an electric range or hotplate that radiate heat all over the place, about 20% into the food.

And don't be so sure about "fail-safe" fuses. There is plenty of dead gear where the fuse is still intact.

BB.

You really need to plan for this new life... Get a Kill-a-Watt type power meter--Great for measuring plug-in loads (Watts [rate], and Watt*Hours [amount of electricity used]). If nothing else--Using this to measure an induction hot plate energy usage (Watt*Hours to cook a meal, LED energy usage, laptop, TV, etc.) will let you get used to the math and better understand your energy usage (useful at home to--for conservation).

For your electric lighting--I would suggest that you look at 120 VAC wiring instead of 12 or 24 VDC powered lights. Just use standard fixtures and the new/modern LED bulbs. They are about the same price (or less) vs 12/24 VDC versions, and much easier/safer to use. And if you send the power any distance--120 VAC is much easier (use much smaller copper wiring). For the most part, any full time off grid home with major appliances (fridge, well pump, lighting, radio/TV/laptop) will probably have a full time operating 120 VAC inverter anyway.

I am not sure what you mean by "electric fireplace"... There are some that are electric heaters that somebody says are very efficient (they are not)--Or you mean a wood stove with an electric fan to distribute hot air around the home (may or may not be efficient).

You might wish to subscribe to Home Power Magazine--Or at least read through some of their online free articles:

http://www.homepower.com/

Conservation is going to be critical to a successful off grid life style... This thread has lots of conservation (and other) suggestions:

http://forum.solar-electric.com/discussion/4426/working-thread-for-solar-beginner-post-faq/p1

And some DYI projects like a "rocket stove" may be of interest:

http://forum.solar-electric.com/discussion/23325/rocket-mass-heater-build (note forum upgrade messed up some attachments--Look for them at the bottom of post)

Anyway--Do not start buying hardware yet--Read, ask questions, and make paper drawings/plans first. Once you have penciled out a workable solution, then start looking for help/installers (when needed) and start buying hardware.

-Bill

Photowhit

First understand that you WILL NOT SAVE MONEY!

Next your bank of inverters is a silly approach to "...power individual rooms much like breakers" Breaker do the same job for pennies on the dollar.

STOP, LEARN, READ about battery bank capacity and the relative difficulties and problems running a 12 volt system, If this is UL rated, it would be UL458 for vehicles NOT homes.  Net this is a Modified Sine Wave inverter, it does not play well with motors and some electronics. If this is more than a couple feet away from the battery bank, you are looking at LARGER that 4/0 wire, think big and expensive!

Insurance companies, don't care. Even if it was fail safe (nothing is fail safe) They see an improperly wired home and the burnt toast catches drapes on fire, burns half your house down, they can and will deny a claim.

You might look at some of the homes in the Show me yours, I'll show you mine Thread;

http://forum.solar-electric.com/discussion/9922/show-me-yours-and-ill-show-you-mine#latest

Photowhit

Okay, I read were you believed this had UL rating, so I found a manual;

http://www.powerbright.com/pdf/PW3500-12_MANUAL_english_french_02.pdf

I can't say much for the company. They claim you can use #2 wire to connect up to 4 feet away. This is silly! First #2 is only rated max 130 amps and typically lower, and 3500 watts at 12 volts would be 290 amps... Actually the wire is so thin you would have large amount of voltage drop and the inverter would fail to function properly.

It does make suggestions as to where to mount it in your vehicle, but doesn't show any UL listing...

Crazy_Wolf1234

well thanks to all of you. Photowhit, although I appreciate your commentary, your negative nancy approach leaves a bitter taste in my mouth. you should try a more helpful tone instead of a condesending one. remember i'm new to this and seeking info not sarcasm. you come off as someone who has either been burned by your own experience with off grid or you work for a(n) electric conglomerate and trying to drive people away from the notion that you can live off grid. offering me an alternative to my idea is one thing but to call it outright silly is over the line. I don't know how you were raised but i was always told if I cant say anything nice then don't say it at all. there are people out there off the grid. I just need to find out what they are doing to get there and follow in their footsteps. 

Aguarancher

you can lead a horse to water, but you can't make it drink.. Photowhit was just giving you the reality of off grid life. if you have grid power available and possibly natural gas, imo that is your best path for heating, cooking and hot water. grid tied solar for your electrical needs. should add that wood heating is great as well and use you furnace blower to circulate the heat between the rooms. good luck

vtmaps

Crazy_Wolf1234 said:

Photowhit, although I appreciate your commentary, your negative nancy approach leaves a bitter taste in my mouth. you should try a more helpful tone instead of a condesending one. remember i'm new to this and seeking info not sarcasm.
<snip>
there are people out there off the grid. I just need to find out what they are doing to get there and follow in their footsteps. 

I reread Photowhit's comments... I don't see the sarcasm you see.  Are you upset by his comments about the powerbright inverter?  I would have made similar comments... 3500 watts at 12 volts is not consistent with good design principles. 

As for folks living off grid, I am one of them.... no electric heaters, electric toasters, no electric cooking, no air conditioners.  It's not that it can't be done, but it's way more expensive than grid power.   My electricity costs nearly a dollar per kwh... fortunately I only use 2 or 3 kwh per day.

--vtMaps

BB.

Just to give you an idea....

• $1 per kWH = 3,412 BTU
• 1 gallon of propane ~ 91,000 BTU
• 91,000 BTU * 1/3,412 BTU per dollar for electricity = $26.67 worth of equivalent heat in 1 gallon of propane at "typical" off grid electrical price

What does propane cost you... Right now ~$1 to $2.50 per gallon?

Granted, cooking over a gas flame is much less than 100% efficient... But even if it was 33% efficient, it would still be ~$9 per gallon for equivalent propane usage.

And remember, while solar panels may last you 20-30 years--Your electronics will last around 10+ years and your batteries may last 5-8 years (typical)--The maintenance costs are not small. And you may only get 2-3 years (or less) from inexpensive AC inverters.

Believe me--Everyone here is trying to give you their years of hard won experiences in very short and sweet posts that address your questions/suggestions. And it is easy to misunderstand humor in posts when missing body language and voice inflections. We all really have the best intent trying to help you here.

-Bill

Photowhit

Sorry if I was a little abrupt, This is a forum to learn about solar. Usually someone else would have chimed in on how bad high wattage / low voltage inverters are. When I saw you had continued on that path, it upset me.

I expressed in my original post that I live off grid, I have for 15 years now! I'm about as close to grid parity as possible and I've saved money in a myriad of ways that are not available to most without background and experience and time to bargain shop.

Here is a thread about the system I built 4 years ago, though the battery is a year and change older and the inverter has been the same one I've used for @10 years, I have yet to replace it, though that was planned.

http://forum.solar-electric.com/discussion/comment/199655#Comment_199655

If you read this, it will show a more optimistic numbers than the usual 50 cents + a Kwh for solar, (small wind tends to be worse!) ...but the cheaper costs comes with a more vigilant approach to the solar. Living off grid will require understanding and a connection to the energy that you supply, that normal grid connected people may not understand.

It's NOT simple flip the switch. In my case running the AC all day and night, would forbid me from heating water, even on sunny days, since I have an undersized inverter for my system. I can some times choose to cook on the gas grill, and leave the Air conditioning running.  It's all in an effort to live within the systems capabilities. Many feel they can make the move to off grid without some compromise.  I would rather be pointed and discouraging rather than they see a large investment that doesn't do what they hoped it would.

At 4000 watt array, my system is poorly matched with a 24volt battery, I would much rather have gone with a 48 volt system, but had already purchased and sized the battery for my previous cabin. With a potential 15-20 year life and small return if sold used I continue to use it. I'll expand the array for daytime use and charging on cloudy days.

You might be able to find solar panels slightly cheaper today, but sub 90 cents a watt is still pretty good. If you want to go with wind, we aren't a great resource, wind has it's own set of problems and is arguably more interactive. We had a very experience person here on wind so looking through our archives could be valuable. Most useful wind requires a regular wind above 12mph and towers 80+ feet tall, these also must be serviced, something to consider. With wind a generator is pretty much required, I choose to live without on solar but it can create issues.

It appears you are building from scratch, and understand the value of the earths constant temperature just a few feet down. You might consider a Berm or earth contact home. Also using SIPs and thick well insulated walls will help moderate things, and rely on less energy.

I do wish you good luck, sorry for being so blunt.

DConlyGuy

if you think photwhit being rude go post this silly post in solar panle talk forum and see what sunking will do to you. i promise you they are being very nice too you here. ill be mean for you family safety do NOT put 3500 watt inverter on a 12 volt system period!!!!!!!

Johann

DConlyGuy said:

if you think photwhit being rude go post this silly post in solar panle talk forum and see what sunking will do to you. i promise you they are being very nice too you here. ill be mean for you family safety do NOT put 3500 watt inverter on a 12 volt system period!!!!!!!

Here at Northern Arizona Wind and Sun Solar forum you may find out that you are being helped without being joked about it or without being stabbed.
This here is the real thing, not like other forums like DConlyGuy mentioned.

DConlyGuy, I have been at the other forum a few times to post and you are right, they stump on you and make you bleed and leave you laying there.

Johann

This forum here is nice gentlemen-like run and they tell you straight out if it will work or not and most at the time these folks will tell what needs to be changed to make it work. It happens that at times they may cut the info short .......but you have to remember that some members spend hours here day after day on a voluntary basis giving there most precious gift to others here ,which is their time and also giving their expertise and experience for free to everyone that comes here. 

So be thankful and be nice to them and show respect.

Crazy_Wolf1234

this is all I needed to know for now. offering needed info without being short with. if it won't work I need to know why it won't work. I don't understand the math you refer to with kwh so when you tell me about systems that I am new to, I need it dummied down. I know there is someone here thats gonna chime in telling me I need to study up on the math before I can begin with it. instead of telling me this, give me a link to where to find this info so I can understand it. I understand watts and volts as I work with small electric flow in automotive and circuit boards. larger forms of voltages such as amps and kwh are forign to me so when I see stats on a refrigerator and it tells me it uses 1200 watts of power, I see a 1500 watt inverter that runs on 12v and put one and one together and get " it should work" then one of you come along and say no it won't without saying exactly why. so, where do I go from here

vtmaps

Crazy_Wolf1234 said:

 so, where do I go from here

If you asked me what pickup truck I would recommend for you to pull your trailer, I couldn't answer.  Not enough info... I need to know the weight of the trailer.  (the trailer is a load).

Likewise, if you want advice on a power system you must tell us your load.  We need hard numbers.  We need to know how many watts you want to draw at one time, and the number of kwh you use in a day. 

How many watts does the microwave (or fridge, or hair dryer, or whatever) draw, and how many minutes a day is it running?  You must answer that question for everything that draws power.

Crazy_Wolf1234 said:

when I see stats on a refrigerator and it tells me it uses 1200 watts of power, I see a 1500 watt inverter that runs on 12v and put one and one together and get " it should work" then one of you come along and say no it won't without saying exactly why.

There's several issues here.  First, and easy to explain, is that 1500 watts is too much for a 12 volt system...  there will be too many Amps flowing through the wires, batteries and equipment.   Volts times Amps is watts... as the voltage goes down, for the same power the amps must go up.   

The second issue is about what wattage ratings mean.  Inverters have a rating for power they can produce continuously, and may also have surge ratings.

Third issue is about what happens when an AC load is not a resistive load.  That means the volts and amps are not in phase. 
If you multiply volts times amps (while accounting for the phase) you get a number called "VA" which is larger than the number of watts that the load draws.  

--vtMaps

solar_dave

Crazy_Wolf1234 said:

this is all I needed to know for now. offering needed info without being short with. if it won't work I need to know why it won't work. I don't understand the math you refer to with kwh so when you tell me about systems that I am new to, I need it dummied down. I know there is someone here thats gonna chime in telling me I need to study up on the math before I can begin with it. instead of telling me this, give me a link to where to find this info so I can understand it. I understand watts and volts as I work with small electric flow in automotive and circuit boards. larger forms of voltages such as amps and kwh are forign to me so when I see stats on a refrigerator and it tells me it uses 1200 watts of power, I see a 1500 watt inverter that runs on 12v and put one and one together and get " it should work" then one of you come along and say no it won't without saying exactly why. so, where do I go from here

The first thing to do is make a list of your desired loads.  This includes how long you intend to run the devices, like I have a computer that draws 50 watts, and I run it for 8 hours a day (0.400 kWh or 400 watt-hours).  The other type of load is attached all the time with a duty cycle, like a refrigerator that cycles 20 minutes an hour and draws 1000 watts which works out to 333 watt hours X 24 hours (1000 watts x 0.333 hours X 24 hours).  From the total for your loads you can then determine what size battery required. It also points to the voltage of the battery system because once you loads reach a certain point it becomes more difficult to manage the amps required to fulfill the load.  For instance a 5000 was max load at 12 volts = 416 amps but at 24 volts it is only 208 amps and at 48 volts it is only 104 amps.  (Volts X amps = watts)   The lower amps allows smaller wire gauges. Watt-hours is how long the load runs at a given amp draw.  (watts X hours)  so 5000 watts was load for an hour is 5000 watt-hours or 5kWh.  BTW this is where a kill-o-watt meter becomes invaluable.

SO once that is done you can then start to choose some hardware.  Batteries used daily like a 10% rate of charge.  Once you know the battery configuration you can then talk charge controllers and solar (or wind) to maintain your battery.  The inverter sizing generally comes for the peak load required (you add up everything that might be on at the same time and take into account the start up surges for motors and the like). Generally most here like pure sine wave controllers as they have a better power factor (another load item) and less idle usage.. You will find many cheap Modified Sine inverters also have a pretty large idle load.

Then there are all the caveats, Sizing the battery to be autonomous for X number of days, i.e what do I do if there is no sun after those X days (generally this means a generator),  what size generator, what charge controller do I get for generator battery charging, and on and on .....

Now you can quickly see why off-grid power is pretty expensive.

Photowhit

I've provided a couple links that might help, Reading about other peoples systems with the show-me-yours... thread may help you get a feel for how systems work, and my current system link.

If someone was planning on taking their current home "off grid" we usually ask them to give use their Kwh's used in a month off their electric bill. When Bill was suggesting a small energy efficient home using 100 kwh (representing a $20-40) it would give you an idea of the limits.

If you hope to go with wind, you will need battery storage for calm parts of the day or days. A generator will usually be part of the equation. Current Lead Acid batteries, don't typically like to be drawn down more than 50% of capacity.

So the math starts out with what your load would be for a normal day, say 4 kwh's this is pretty small and would be no or minimal air-conditioning. So for how many days do you want autonomy  ( drawing from the battery as your only source of power before you have more wind or start your generator) say 2 days. You would need a battery bank that could store 4 kwh's of energy for each of 2 days, 4kwh's x 2 days = 8 Kwhs and you don't want to draw the battery down more than 50% so double it again for 16 kwh's of storage, This would be about a 48volt 340 amp battery.

With out established load, as vtMaps has pointed out, the numbers are difficult. Once you have a battery size you can figure the charging parameters, a 340 amp hour battery will want to be charged in a range of 10-13%(maybe 15%) or 34-45 amps. So you can then look at the normal wind and calculate the wattage it will need to generate to charge the battery on a normal day, you will have to look at the output curves! a 500 watt wind generator might produce 500 watts in 22mph winds while you normally only have 12 mph winds. In 12 mph winds it might only produce 60 watts. The wind speed will also vary with the height above disturbances.

Wind also produces energy, while you can just "turn off" a solar panel, you will need a diversion load for wind generators. Often a heater in a large body of water, many will also have an air heater inside for winter months. This allows the charge controller to send the energy somewhere when your batteries are full.

Hope this info is in a reasonable form, I really do try to be helpful...

BB.

It is not that it won't work--But, over all, when you take battery bank size, wiring costs, diameter of wiring, fusing/breakering, and such into account--It can become quite difficult to make a cost effective, safe, and reliable system.

Just to take the example of your opening post... A 3,500 Watt and 1,500 Watt inverter running on a 12 volt battery bank. Assuming you want to use rated power (5,000 Watts total, and each inverter is rated for ~2x rated output for starting surge--motors/well pumps/etc.) on a 12 volt battery bank... Using our standard rules of thumbs for designing a system with flooded cell lead acid batteries--More or less, the minimum recommended battery bank that will supply rated loads over the life of the system--Recommend 400 Amp*Hours per 1,000 Watts of solar array / AC inverters on a 12 volt bank (and 200 AH per 1 kWatt on a 24 volt bank; 100 AH per 1 kW on a 48 volt battery bank) (note: our design rules have ranges--I am just picking the middle values for a full time off grid system--We can discuss details where you wish):

• 5kWatt of AC inverter * 400 AH per 1kW (on 12 volt battery bank) = ~2,000 AH @ 12 volt battery bank minimum

So--that is either a set of 2x 6 volt @ 200 AH "golf cart" batteries--10x strings in parallel ($100 per battery * 20 batteries = ~$2,000)... Or something like:

• Crown Industrial Battery - 12 Volts, 1875 Amp-hours ($4,800 at 1,500 lbs)
• Crown Renewable Power Battery - 2 Volts, 2050 Amp-hours ($1,050 @ 259 lbs each * 6 in series)
• or other options

Personally, I do not like lots of parallel strings of batteries (2-3 maximum is my basic recommendation)--You are looking at lots of wiring/fuses/breakers and 60 cells to check water levels on.

To charge such a battery bank--~10% rate of charge * 2,000 AH = 200 Amps of solar--The typical solar charge controller is ~60-80 amps--So you are looking at 3-4 charge controllers (at ~$600 each). If you ran a 48 volt battery bank, you would only need 1x charge controller (50 amps @ 48 volts)--Still the same size array, just fewer solar charge controllers:

• 200 Amps charging * 14.5 volts * 1/0.77 panel+controller deratings = 3,766 Watt "nominal" array

Next--The wiring. Say you want to run 4 feet of wiring from battery bank to battery bus bars (connect inverters/solar chargers/DC chargers/DC loads here). Assume 11.5 minimum battery voltage (somewhat discharged, under load), 1.0 maximum voltage drop (or 0.5 volts at rated load vs 2x surge load), and 10.5 AC inverter cutoff voltage:

• 5,000 Watts * 1/10.5 volts cutoff * 1/0.85 inverter eff = 560 Amps maximum load (or 1,120 Amps at maximum surge)
• 560 Amps * 1.25 NEC derating for wiring/breakers/fuses = 700 Amps rated max continuous for wiring/breakers/branch circuit

So--Looking at NEC and Marine wiring tables:
https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

You are looking at ~2,000 kcm copper wiring, or approximately 1.6" diameter wire:
http://www.ihiconnectors.com/AWG wire sizes.htm

Or for Marine, ~2x 4/0 cables in parallel (paralleling of power cables is not a great solution):
http://www.boatus.com/boattech/articles/choosing-cables-and-terminals.asp

And then there is voltage drop--4 feet, 560 Amps, and 0.5 volt drop maximum:
http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.3224&voltage=12&phase=dc&noofconductor=1&distance=4&distanceunit=feet&amperes=560&x=44&y=9

1/0 AWG copper wire:
Voltage drop: 0.44
Voltage drop percentage: 3.67%
Voltage at the end: 11.56

So you need 1/0 minimum just to send the current 4 feet (and this does not allow for any AC inverter DC input wiring losses, fuse/breaker drop, etc...).

And then there is sizing your off grid system to run 5,000 Watts of AC inverters on a 2,000 AH @ 12 volt battery bank... Since I do not know your total energy usage per day (Watts is rate--Like pumping 10 gallons per minute of water, Watts*Hours is an amount--Like total gallons pumped). So, assuming you have a 3,766 Watt array (balanced to battery bank size) and use the battery bank for 2 days of "no sun" and 50% maximum discharge (for longer battery life):

• 2,000 AH * 12 volts * 1/2 days of storage * 0.50 maximum discharge * 0.85 AC inverter eff = 5,100 WH per day
• 5,100 WH per day = 5.1 kWH per day = 153 kWH per month (still a medium sized off grid system--enough power for an off grid home run efficiently and using propane/other fuels for cooking/heating/hot water)

And a 3,766 Watt array will produce (on average):

• 3,766 Watt array * 0.52 average off grid system eff * 3.46 hours of sun (February break even month for Indianpolis, see earlier post) = 6,776 WH per day (Feb Average) = 6.8 kWH per day

There are the numbers--The average US home uses ~600 to 1,000 kWH per month, and if you have heavy A/C usage and/or electric hot water, electric heat, you can be as high as 2,000 to 3,000 kWH per month.

A very efficient off grid home with lots of conservation and using propane/wood/etc for heating, solar thermal/propane hot water, etc. -- 100 kWH per month is a good aiming point (smaller off grid system for LED lights, fridge, clothes washer, TV, computer, well pump).

Amps can be used for system design--And works well where all of the voltages (loads, charging, etc.) are the same--I.e., an RV, car, boat where everything is 12 VDC--You can use Amps everywhere in the design.

However, when you you are working with mixed voltages (i.e., 12 volt battery banks, 120 VAC output AC inverter, etc.)--Then I like to stay with Watts--It is a "complete" unit for describing your system loads/charging... And Watts is:

• Watts = Volts * Amps

So--Say you have a 1,000 Watt induction hot plate... At 120 VAC (typical north American line voltage:

• 1,000 Watts / 120 VAC = 8.33 amps (a standard 120 VAC @ 14 AWG extension cord will work fine for this)
  

However, if you want a 1,000 Watts at 12 VDC:

• 1,000 Wats / 12 VDC = 83.3 Amps (and now you are looking at a 4 or 2 AWG, or heavier, extension cord)

And Watt*Hours / Amp*Hours -- This is an amount of energy--How big of battery bank (i.e., gas tank) do you need to store the electricity... We use Amp*Hours and Watt*Hours... Hours of usage at that "rate" (amps or watts).

If you want a 12 volt battery to power a 1,000 Watt load for 1 hour of cooking, and want to have 2 days of storage and 50% maximum discharge:

• 83.3 Amps (at 12 volts) * 1 hour * 2 days storage * 1/0.50 max discharge = 333.2 Amp*Hour @ 12 volt battery bank
• 1,000 Watts * 1/12 volt battery * 1 hour * 2 days storage * 1/0.50 max discharge = 333.2 Amp*Hour @ 12 volt battery bank

The above assumes a 1,000 watt load @ 12 vdc... Since the induction hot plate is probably 120 VAC, then we have assume it is around 85% efficient, and the battery bank would need to be 1/0.85 = 1.176x larger:

• 333.2 AH @ 12 volt battery * 1/0.85 = 392 AH @ 12 volt battery supplying a 1 kW induction cooker for 1 hour over 2 days of no sun, maximum of 50% discharge
  

I am sorry for all of the math--But we really do need to boil down your loads into numbers so we can help design a "workable" and reliable off grid power system that will meet your needs.

I suggest you get a little Kill-a-Watt (or similar) meter and start measuring some of your loads... Your TV, computer, induction cooker usage, etc... And figure out how much energy (Watt*Hours) your devices use in one day. It is really an education.

-Bill