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Solar power

Discussion in 'Off Grid Living' started by Barbosa, Jul 8, 2011.

  1. Barbosa

    Barbosa Monkey+

    I did a search here on "Solar Power" and got a lot of...well, nothing. And I can't seem to find websites of informational value as well. What I would like to start with is a simple 500w systen to run a few simple things. But I have questions...*sigh*

    Can panels be added onto existing panels later for more power?

    I'm having trouble with batteries. If I want a 120v system to run, say a small refrigerator, I know I have to have an inverter. But because a fridge doesn't run all the time, I haven't a clue as to:
    What type of batteries?
    How many batteries?
    Which are the best batteries?
    And I simply cannot afford $200 golf cart deep cycles. So what to do? The same questions can be asked if I wanted to run a small window a/c unit for a single bedroom at night.

    Are the Federal incentives a one time only deal and whole house or can I get an additional incentive a year later when I add another one or two panels?

    It's all somewhat mindboggling to me at this time. I need help from those that have installed small solar power systems.

    Thanks for any help.

    eta: It's been said solar is affordable. A 260w system (two 130w panels) with modules is $1200.00. I can't see that as affordable....to me at least.
  2. BTPost

    BTPost Old Fart Snow Monkey Moderator

    System Power covers a lot of issues, some of which you have outlined already.Some things to consider are:
    1. How much inverter power are you going to need in the end?
    2. What does you daily load look like?
    Battery Bank voltages can be varied, depending on what you load is like.
    Solar Array voltages can be varied depending on the Charge Controller you get to charge your system. The only thing that can NOT be changed once it is bought, is the DC Voltage input of the System Inverter. These can be purchased in 12/24/48 Vdc versions, but once you decide that spec you are stuck with that, unless you buy another Inverter. Where as Battery Bank voltage depends on Inverter Dc Input Voltage, but batteries can be rewired into banks of different Bank Voltages, as your system grows. The same is true for Solar Array Voltages. Solar Panels can be wired in various setups to supply the Charge Controller whatever DC Voltage is best for the Battery bank it is charging.

    The RULE OF THUMB for this is:
    1.2 Kw inverter or less. 12 Vdc Inverter
    1.2 - 3Kw 24Vdc Inverter
    3kw or larger 48 Vdc Inverter

    Once you decide on the Inverter DC Voltage, then you can make intelligent choices, about batteries, Charge Controllers, and Solar Arrays, and Panels.
    The thing to remember, is that everything can be changed, by just rewiring, EXCEPT the Inverter Dc Voltage. That is fixed by the unit you buy.

    Many folks start out with a 12Vdc Inverter, then find it is not big enough for their needs, or out grow it, and then have to go back an invest in a different, larger, inverter for their system. Those folks usually then use the old inverter as. Backup, should the Big Inverter fail, or sell it, to the next guy who didn't plan his system out before he spent his treasure.

    This is a technology that needs a good design before money is spent.

    STANGF150 and hank2222 like this.
  3. Barbosa

    Barbosa Monkey+

    Thanks Bruce. I have a lot of learning to do.
  4. TnAndy

    TnAndy Senior Member Founding Member

    I have no idea where you heard solar was "affordable", but it wasn't here.

    A relatively small system is going to run you 3-4k.

    I've got 20,000 in mine, and it supplies 350kw/hrs or so per month ( see my thread "real world numbers" ). Look at your electric bill and see how far 350kw/hrs per month would do you.
    LogOut and hank2222 like this.
  5. greenebelly

    greenebelly Monkey+

    Inverter or charge controller

    I have been looking into another route. I am looking at replacing the A/C motor on stuff for a D/C one. This would stop the loss from the conversion AND the D/C motors use less energy. So you would need a charge controller not an inverter. I was going to put another small panel by the big house one and just put a couple "branches" that are D/C. (eg: refrigerator, freezer, dishwasher, washing machine, etc..) Put water heater on roof system and MOST of power :oops: would be taken care of.IMO
    hank2222 likes this.
  6. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Greenbelly, you have to understand the technology, to make reliable choices. You are under some preconceived notions that are really relevant to this conversation.

    1. Who ever told you DC Motors were more efficient, and use less energy, than Ac motors, needs a refresher course in Physics. Work is Work, and it takes the same amount of energy to produce the same work, no matter how that energy is transformed into the work.
    2. Modern Switch Mode Sine-wave Inverters are in the 90% efficient Range, and the conversion losses are usually less than the I2R losses, due to the higher current, at the lower DC Voltages involved.
    3, DC Motors are ALWAYS more expensive than AC Motors, for two reasons. Quantity of Scale, and amount of Copper required for the same HP Rating.

    Both TnAndy, and I have been living in the Off-Grid World for decades. We both have Designed and Operated these systems for Decades. You can read our stuff and decide for yourself, if we are full of BS, but we live this every day, and we have as efficient of systems as can be done, in our specific worlds. ..... YMMV...
    hank2222 likes this.
  7. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    GB, both BTPost and Nadja are totally off grid, and TNAndy is grid connected, but self sufficient (and he's selling to the grid.) Pay attention to these guys, they will not steer you into mistakes.

    DC motors are not more efficient than AC, especially under part load. Either way, you need to account for starting draw, not just running amps. An expensive, but very efficient option is soft start controllers for the motors. Not practical for things like reefers, but maybe for fans that run a lot.

    You can also use variable speed controllers on AC machines that will save money in some cases, as well as reduce the number of starts. Take the cork out of your wallet for those, the initial costs are not for the faint of heart; but over time, they will pay you back.
    hank2222 and BTPost like this.
  8. Barbosa

    Barbosa Monkey+

    But guys...I'm not looking to go self sufficient now. I'm just looking for a cheap and reliable system for my retreat to run a refrigerator (or an ice maker) and some LED lighting. Maybe some electric power tools as well. I'm fairly certain a 1500w system would do this, but at $2.00+ per watt, I can't afford it at this time. But what stymies me is how do you figure how many batteries you need to maintain it during the night?

    I'll check out your thread, Andy. And if you guys have pertinent info you can link me to, I'd appreciate it.

    Is there a book out called Solar Power for Dummies?
  9. STANGF150

    STANGF150 Knowledge Seeker

    Barbosa trust me when I say these guys know more about Solar/Off-Grid Power than the companies that make the products to do it. An once Hank222 chimes in you'll have enough combined knowledge here in this thread to blow your mind. God knows they've blown mine on the subject on many an occasion. However I do know enough to tell you the bad bad news. When it comes to Solar the words "cheap" and "reliable" do not belong in the same sentence.
    hank2222 likes this.
  10. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    OK, time for me to chime in and by the way, good morning. 12v wiring is very expensive (to do it right) as it takes a very large version to carry the 12v elec any distance at all. Fed. tax credits are a one time use , but per year. My understanding on this is that if you buy say 5,000.00 in solar this year, you can use it one time only on your tax forms. However, also been told that it expires in August of this year. You can check on that yourself, and be much wiser for it. Also some states like mine have a tax credit system in place.

    Running your refer etc will cost you dearly in solar. I know this to be fact as I live totally off grid, and have for over 16 years now. I get by on about 2,000 watts , incoming, with a boost now and then from my wind gennie and gas gennies. Now that the 'soons are rolling in, my solar is struggling to keep up with everything, and will now have to supplement incoming power with one of my stand-by gas gennies.

    But, since I will be running a gennie this morning for about an hour, I will have s.o.s. for breakfast . MMMMMMMMMM The toaster like all elec. heating units , uses an un-godly amount of power.

    Now, although not practical for me when I started very small years ago, I would recomend that you start with 24v. system, including the inverter. The best bang for the buck right now is the outback series and I would go with their inverter, charge controler and "mate". Although more pricy they the dime store or truck stop inverters etc, they will last you many years and give very good service. Solar panels, go with panels made in either Japan, or Germany. Best bang for the buck as I know it right now, would be the German made "Shucko" panels in 265 watt, 24 volt version. About 585.00 per panel. 25 year warr. and they really deliver the power. Batteries, I would not consider anything less the Trojen series. Although you could go with the wall mart version of golf cart batteries, which may last you a few years or so.

    Get more specific and you will find out much more info here. Good Luck on your venture. Nadja
    hank2222 likes this.
  11. TnAndy

    TnAndy Senior Member Founding Member

    I recently put almost that exact system in an off grid cabin retreat for a buddy.

    See this thread:


    And I don't know what to tell you on price, other than 2 bucks/watt won't even come close.....more like 5, if you do your own labor, and 8 if you don't.

    As to the number of batteries, there is no short answer. It depends on how much you intend to use ( you will need to know pretty much the exact wattage of the appliances AND the length of time you want to run them between sunshines....not exactly an easy figure to come up with, huh ? )......and also how many days of "autonomy"....which is rainy, crappy, non-solar days...you want to shoot for. Most designs figure 3 to 5 days, then if the sun doesn't shine, you go to generator power to recharge the batteries.

    There IS a heck of a learning curve on solar. It does begin with asking questions, but learn ALL YOU POSSIBLY can before you purchase the first pc of equipment.....and become more realistic on the cost, because right now, you are WAY under what it will cost to power yourself.

    People have no clue how cheap grid power is until they try to be their own grid !
  12. hank2222

    hank2222 Monkey++

    Remember the money you spend now on the better high end parts now from a good dealer is going to be alot better than having to keep spending the money to replace crappy part's that fail at the wrong time..

    Yes in the end it does come down to the cost of a good well known name brand item compared to the cost of a china mart items when building your system for the place ..So spend the money on the good parts and they will last you alot longer than the socalled china mart part's

    Also go to your local library and check out book's on solar and wind then read them and then reread them intill your tired of readying them .

    Then sit down and figure out the basis of you power need's go through it and then throw half of it out because in the end you not going to need them or it can be replace by something else in the area

    Like a propane or Lg gas appliance in that area instead of electrical appliance or Use wood to heat or cook with inside the place or if you do pick a electric appliance in that area pick one that is highest rated energy appliance you can find

    So that means you going to need to update some of the thing's like the tv or dvd player or something that you can not live without in the house ..

    Then when your ready to spend the money get with someone who been in business for a long while and then talk them and have them go over everything then spend the money on the part's that they have told you to get or the system that they put togerther in the end for you to use at you place ..

    Then when they are putting it all togerther get in there and work with them to grain a basic knowage of how the wireing is done to the areas and how they did this with the battery bank or why they did this with that part .It your system learn it from the ground up the reason and the why's they are doing something's when building it and putting into the unit's

    Nadja & Bruce & my personal unit & other people system that they have on this board are design in diff areas to do diff thing's out of there system that they have .So my power need's are diff than you power need's so remember that when we talk about the person need's ..

    So remember when designing the system one size does not fit all in that area's of design and use of a off grid system.
    Nadja likes this.
  13. hank2222

    hank2222 Monkey++

    TnAndy brings up a good point on how many day's you want to have of battie's power stored for use before going to a generator or solar or wind to charge the bank ..Remember some areas of the country will get more solar day's than other ..

    Nadja and i are both in Az and we get some good socalled solar day's number but Bruce there in Alaska get some really crappy solar days in the winter ..So alot of is the basic knowage of how many days of stowage do you need ..

    Like TnAndy bought up it the basic days -x-how much do you need -x-the size of the bank before you need to have the battery bank recharged .

    This also bring's up the next point .For those days the sun is not shineing and the wind is not blowing what are you going to do for a basic chargeing system outside the normal solar and wind charging system ..

    That means a fuel driven system so pick a unit that meet's your needs in the end and can be used as it need .
  14. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    Another quick note on batteries. IF, you buy say 4 now, and try and add say 4 more next year, your oldest batteries will pretty much determine the longevity of all 8. In other words, this is where you really need to plan where you want to end up with your solar system. The older batteries will only drag the new batteries down to their level. You can add solar as you need it or can afford it, but doing batteries that way will only mean more batteries every couple of years as the need arrives and the ones that will not keep up with the newer ones, would need to be upgraded also. Try and buy them all at once if at all possible. Stay away from the rv batteries etc.
    hank2222 likes this.
  15. Barbosa

    Barbosa Monkey+

    Really good advice and thanks to you all. I reckon I'll read up on it before throwing out more questions. But at least I now know who to come to!
  16. irayone

    irayone Monkey+

    My van is solar powered....I have an 85 watt pannel with 2 AGM deep cell batterys at 56 amp/hr.
    a 1000 watt inverter. Which runs an Engle refergerator which burns at 3.0 amps per hour. I turn off the reffer at night. The refer runs by thermostat IE 85 degrees outside....turns on every half hour for 30 min and will freeze if I set the thermostat.
    Therefore... at 3 amps per hour at 30 min for 12 hours.... 18 amps per day...durring the day I can store aprox 35 amps per day. So at the end of the day my batteries are full. I also run lights and radio. I can charge and run any other equipment at 1000 watts or less. This system was only 600.00 It is also removeable so I can take it any where. Cost co sells a set up for 150.00 with 55 watt pannel, inverter, chager without batteries...
  17. hank2222

    hank2222 Monkey++

    Go to PVWatt's Google it and it will give you a basic idea about the solar wattage for your area that you in ..
  18. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    When I first moved up here, I knew nothing about solar, like you spent a lot of time with the learning curve. This is the kind of advice we will try and give you. We are not selling products, only advising , through years of do's and don'ts where to go and not to go. The "prof" salesmen type people are generally paid on commision and will try and sell you anything to make a buck. They will also tell you anything for the same reason. Kinda like car salesmen.

    There is no such thing as solar dummy, only solar un-informed. Please reserch everything you read here yourself BEFORE you lay down your hard earned money. Knowledge is key and also the way to save many many dollars. TNAndy is probably the best for actual hook-up info, and Bruce is great for people haveing to cope with the great Alaskan Wilderness with its days of very little sunshine. I live in N. Az up in the White Mtns and have fairly long solar days.
    Kingfish and hank2222 like this.
  19. hank2222

    hank2222 Monkey++

    belive me when we are telling you it a learning curve and i been doing it since 1982 time frame and i'm still in a long learning curve ..

    Nadja bring up a good point about the batties you are going to destory a few in the learning of how and what work's in solar so get ready for that one ..

    Everyone here has a diff learning curve on the subect of solar and some of it comes with basic knowage of how i screw up part on some of the thing's we are telling you about when it comes to off grid and solar liveing ..
  20. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Well, so far everybody has been giving "Sound Advice" I do not have much more to add, at this point. I would point out, that I have a blog here on the Monkey, http://www.survivalmonkey.com/forum/blogs/btpost/alaska-wilderness-building-231/ that goes thru many of the requirements for designing, and building, in my country. It is written for the Alaska Wilderness, but the principals discussed, are sound for just about anywhere. It gives many of the alternative approaches, to specific issues, in Off-Grid, and even Grid-Connected Energy Systems for a place. It is about a 15-20 minute read, and can help one frame the right questions to ask, and be answered, on specific issues, for your intended use. All of us, here on the Monkey, are mostly here to help folks, by providing Real World information, from our collective experiences, freely, for the betterment of our Monkey Friends. As Nadja pointed out, we aren't selling anything, we are just imparting our collective Institutional Knowledge. So read, learn, and make Informed Decisions, before you let loose of any Hard Earned money, and when you are done, you can bring your gained knowledge back, for then Next Monkey Brother, or Sister, that needs to find these same answers, to the Age Old question, you had at the beginning of this thread. .... YMMV...
    hank2222 likes this.
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