Simple solar gal needs bigger ideas

Fiddler · August 2012

Hello, my name is Gina and I have acquired a small cottage that has 8, 255 watt panels. VMPP 30.05, IMPP 8.376A, VOC 37.92. 4- L16 370AH, 6 volt, 4- T105 6 volt. I need to purchase a controller to make all this work and I need a plan of how to wire all these, in series , then in parallel right? Which controller would handle this much voltage? I'm assuming I need to do a 24V array and battery? These panels are roof-mounted and periodically have light shading but not too bad. I have only a short run from the array to the battery/control box of about 12 feet. currently this system is not wired or operating. This is a project that was left with the house. The only experience I have with solar was a small system 20 years ago, 12v. I have grid but it is very unreliable. My goal is to power most of the 110 circuits off grid. I need ideas how to make the most out of this and that works reliably. I'd appreciate any input.

Photowhit · August 2012

Re: Simple solar gal needs bigger ideas

I guess you understand that off grid is less effiecient than a grid tied system, and all that. If you've done your research, lets talk about wht you have...

If your batteries have just been sitting for more than 6 months, you should try to evaluate if they are still good, a quick check of voltage, then an equalizing and another check. Standard battery chargers may not be able to help. Likely a check of voltage, a manufactured date, and what they have been doing the last 6 months will help us help you evaluate them. If the previous owner had bought batteries, likely he has a charge controller around, though he might have shot him self in the foot so you could get a good deal on a cabin!

You have about 2Kw of solar panels and what looks like an appropriate battery bank. The panels are designed for an MPPT charge controller, at 24V you need a charge controller that will handle (2000/24) about 83 Amps max output, I like the Midnite classic 150, and this may work for you, You can plug in your numbers in their system sizing tool Here. You may want to go with their Classic 200 if only for simplicity if your region(VOC in winter) put 2 strings of 4 panels out of reach. I say that since if you can keep the panels down to 2 strings, they won't need to be fused. (I ran mine in central Missouri with a max low of -12F and a slightly lower VOC and while safe the cut out voltage was close to 40F degrees which the panels might not reach on some days)

If you live frugally, use gas and a seperate solar water heater, and gas for most of your cooking, can live with no or little Air conditioning, this system might well produce enough electric to run a small cabin.

Your inverter will depend on loads, if you haven't limited your loads in the past likely you have just a clue as to what draws lots of current, typically it will be things that heat and cool. Hair dryers, ovens, fridges, water heaters, space heaters, air conditioners are all minimal use or not practical on Solar. Watching leach loads, wall warts, recharging stations left plugged in, Things with remotes, all use a small or not so small amount of electric, it's been reported that a satalite reciever uses as much on or off!

You might look into a Kill-A-Watt meter to see how much wattage things are using. In a frugal solar home your fridge is likely your largest user of electric day-in and day-out. And if you consider going off grid this would be the first thing to check out!

BB. · August 2012

Re: Simple solar gal needs bigger ideas

Welcome to the forum Gina.

Boy, you have a real mix of hardware:

8x 255 watt panels. VMPP 30.05, IMPP 8.376A, VOC 37.92
4x L16 370AH, 6 volt
4x T105 6 volt

In general, it is not a good idea to mix batteries (brand/model/size/age).

Next, have the batteries been kept charged (and electrolyte checked) while unused? If left for months or longer without charging, the batteries may be sulfated and possibly no-good. If kept on chargers, they may not have had the electrolyte level checked and filled with distilled water--If the plates are exposed to air/oxygen, they will be no good.

So--get yourself a good volt meter (this Sears unit has a DC current Clamp too--very nice for working around off-grid systems--only $60).

Check the electrolyte levels in the batteries and measure the (resting) voltage. If it is below ~6.2 volts per battery, then they need charging. If 6 volts or less, they may not be OK.

Next, the solar panels you have are not really "24 volt" panels for charging a 24 volt battery bank (directly using an inexpensive PWM charge controller). To charge a 24 volt battery bank, you really need Vmp~35-39 volt panels to get the most efficiency from them.

Note that Solar PV (electrical) panels need full and direct sun. If there is any shading (even a power line, corner of a panel, etc.), it can dramatically reduce power output (easily 1/2 the power or more lost per string). Watch the seasonal position of the sun--If in winter the sun is behind a stand of trees (for example), you may want to think about taking down some trees or moving the array elsewhere on the property.

You can easily put two or three of this panels in series with a good quality MPPT type charge controller (~$500 to $600) and they will work well for you.

Our first question we always ask is how much energy (Watt*Hours or kWH) per day do you need. A Kill-a-Watt type power meter is a cheap and easy way to measure the power of your 120 VAC appliances. Run each appliance for a day (or even a week) and log the power usage.

Refrigerators, desktop computers, TVs/DVR/Sat Boxes, etc. all consume a lot of power... For example you might use a Microwave for 15 minutes per day (1,500 watts), and leave the desktop computer on 24 hours per day (at 200 watts). The math works out to:

1,500 Watts * 0.25 hours per day = 375 WH per day = 0.375 kWH per day
200 Watts * 24 hours per day = 4,800 WH = 4.8 kWH per day

An Energy Star rated Refrigerator may use 1-1.5 kWH per day. A small laptop computer may use 0.5 kWH per day...

So--As you can see, your power usage and conservation measures can really affect your daily power usage.

A (8x255 Watt=) 2,040 Watt solar array can supply upwards of 4,160 WH per day (4.16 kWH per day) for 9+ months of the year--That is a pretty good sized "cabin" system. But, as you can see--Just a couple appliances can easily use all of that energy and even more.

Ideally, we would like to design a system around your power needs. We can also design a system around a battery bank or solar array size--But we really don't know if that will "meet your needs" or not. Power usage is a very personal set of decisions--And what works for me (suburban home with no A/C) vs somebody off in the middle of no where will be different.

Also, can you give us a rough idea of where your cabin will be located? Amount of sun will affect the amount of power your solar array can output.

Lastly, off grid solar power is not cheap. If you have grid power, even if sort of unreliable, a backup generator may be a better solution. You can also build a battery+inverter system -- Basically an uninterruptable power supply (UPS) for your home. And add a backup genset and solar later as your finances permit.

Questions, further information, changes to my assumptions?

-Bill

Photowhit · August 2012

Re: Simple solar gal needs bigger ideas

I guess I skipped over the part about having a 2Kw array, I'd suggest a 24 volt system, so 1 string of 4 - 6V L16 batteries and using wood for heat.

Questions such as;
Where is this cabin located?
What type of loads will you have?
Will this be a weekend use or full time?
and Do you want to have a solar system, it likely would be viable to sell what you have and buy a generator for your cabin. Solar does require some attention, as would a generator but mostly when needed or stored for a long time.(I don't have one by choice and at times have to limit my use of electric)

I read right over the 105's, Check the manufacture date on both sets of batteries while your collecting information for us. Good thing we have Bill!

vtmaps · August 2012

Re: Simple solar gal needs bigger ideas

Fiddler wrote: »

These panels are roof-mounted and periodically have light shading but not too bad.

Welcome to the forum. What, exactly, do you mean by "periodic light shading"?

Fiddler wrote: »

My goal is to power most of the 110 circuits off grid.

You didn't mention anything about an inverter. You will need an inverter. Also, do you want this system to be grid-tied? If so, you need to talk to your utility and learn what are your options. The type of inverter you buy will depend on whether you are grid-tied or not.

--vtMaps

Fiddler · August 2012

Re: Simple solar gal needs bigger ideas

vtmaps wrote: »

Welcome to the forum. What, exactly, do you mean by "periodic light shading"?

You didn't mention anything about an inverter. You will need an inverter. Also, do you want this system to be grid-tied? If so, you need to talk to your utility and learn what are your options. The type of inverter you buy will depend on whether you are grid-tied or not.

--vtMaps

The cabin is in north Florida. I plan to live here full time, don't care about the money, I want to be self sufficient. I have two air ttight wood stoves for heat, vacuum tube solar hot water heater 50 gal. and a 6000 watt backup generator. I have good sun but periodic shadows from trees. Don't have the inverter or controller yet. The power is shaky here. A tree can go down and I could lose power for days and days. This happens often. The batteries are new. I also have 13 Kyocera 175 watt panels in the barn in boxes. I inherited this mess from someone who wanted to be completely off the grid. I think I can live on 2000 watts a day..Fridge, computer, a little TV, all LED lighting, less than 10 min of microwave daily, would like a small AC unit but really need lights and power first. Gina

vtmaps · August 2012

Re: Simple solar gal needs bigger ideas

Fiddler wrote: »

I plan to live here full time, don't care about the money, I want to be self sufficient.

Its good that you don't care about the money... compared to being on grid, it will be quite expensive. Have you considered grid-tie? It is usually much less expensive because you use the grid as your battery. When the grid is down, an efficient generator is, over the long term, cheaper than a battery system. Yes, I realize you already have the batteries, but don't worry -- you will get to buy new ones every 5 - 8 years if you take very good care of them, more often if you don't.

Fiddler wrote: »

I think I can live on 2000 watts a day..Fridge, computer, a little TV, all LED lighting, less than 10 min of microwave daily, would like a small AC unit but really need lights and power first.

You mean 2000 wattHours. Maybe 2000 if your fridge is efficient enough. An A/C will pull you over 2000. (btw, "AC" usually means alternating current).

--vtMaps

Photowhit · August 2012

Re: Simple solar gal needs bigger ideas

Now we're getting somewhere, I use to live in Tallahassee, Crawfordville, areas. I use to be a photographer for the Tallahassee Democrat. With bad electric problems I'm guessing Dead Lakes area or Ponce DeLeon area. Do you have an arteasian well? I know some in that area do, or have a well at all or county water?

Well pumps are another high demand electric, though there are some things you can do to make the load lighter. In North Florida the water table is only feet under the ground so water will rise to a few feet under the ground, you may need to go down 100 feet or more to tap into the Florida aquifer, but the natural level for the water will be only a few feet under ground so your pump won't need to work as hard.

With an extra 2Kw of array, I'd suggest a 48V system, if the VOC, VMP are close to the panels on your roof, you might be able to do it all on one Midnite classic charge controller. Does your cabin have high ceilings? Lots of insulation? If you can live in North Florida with out AC I'm impressed! Heck I can't live in Missouri with out air conditioning.

On terms, watts is a measurment at one point in time, if your talking about a 24 hour day, you need to talk about watt hour Wh. 2000 watts at one time is a lot! A cheap space heater uses 1500 watts and with inverter in effiecencies closer to 1700 watts. But 2000 watt hours, in a day, is an old fridge or even a new fridge in a 90 degree room.

When looking at computers, Towers can use more than 200 watts and gaming computers 400+, Laptops will use 30-80 watts, the 11.7" screen netbook I'm on used 20 watts or less. To figure watt hours, plug them into a Kill-A-Watt meter or estimate your hours and multiply times the hours of use. As Bill said your current array will likely provide 4000Wh (4KWh) a day and the extra panels will get you to enough energy to run a window or 'mini split' air conditioner, if you don't have other large loads. With my local knowledge I'll say it is unlikely you will be comfortable with out air conditioning, a proper old dogtrot cabin with high ceilings is simply bearable in the hot humid climate. In a 'normal' home you will have problems with the humidity and mildew. For others reading this and unfamiliar with this climate line drying clothes often doesn't work!

For a start on loads, what are your electric bills telling you on Kw hours used? If you currently have a washer dryer they will be a serious load as well. The washer is doable, but only a gas dryer is realistic on a solar or battery based system. The 2 wood stoves is giving the idea that it's a large place?

Photowhit · August 2012

Re: Simple solar gal needs bigger ideas

Please post the info for the "Kyocera 175 watt panels" this will help us determine if they will work with the panels you have up and running.

Also in Tallahassee there is a solar shop, Simpler Solar Systems, Al Simpler has many years of experience, has been in business for 30+ years, I think. He can be a good resource, I would suggest you talk with us for a while and have a good understanding before talking with him, after 30yrs of dealing with walk-ins who "wanna do sumthin' with solar" he's pretty hardened. Purchased my first 4 panels from him starting close to 20 years ago, dang I'm getting old...

Mod's Al has a web site and claims to have an on line store, but the link goes nowhere, if it did it would mostly be overpriced stuff, he's more of a designer, though he use to have batteries made for solar apps.

Photowhit · August 2012

Re: Simple solar gal needs bigger ideas

More thoughts, I'd go ahead and sell the T105's they won't work 'with' the L16's and are too small for use with a 2Kw array (particularly with the L16s available). They have some value while they are new. Please note 'new' has to do with the manufacture date, a new battery that sits for 6-8 months might well be toxic trash! Since you inherited them, a new battery drawn down to 20% capacity and left sitting for 2 weeks could be trash also!

You might invest in a true deep cycle charger or find someone (a battery shop or golf cart shop), to charge up and maintain your L16's, you'll want them healthy if you decide to buy 4 more for a 48 volt system!

BB. · August 2012

Re: Simple solar gal needs bigger ideas

Links that answer questions and/or point to good suppliers are always welcome.

-Bill

Fiddler · August 2012

Re: Simple solar gal needs bigger ideas

This house is in a remote area that utilizes an electric coop that is amateurish at best. I'm located south of Horseshoe down in the California swamp. I don't have an inverter and I'm confused about modified sine wave. Is this harmful to modern appliances or are pure sine wave inverters the way to go? I'm assuming I need to run 4 series of 2 modules in parallel to achieve 24 volts (correct?) With the MPPT controller and I did look at the Midnite Classic and it looks like it will do the job. Will this change the 24 volt battery configuration or should this remain the same as the panels are wired? i only plan to run the 2040 watt array just to learn what's going on. Are there other ways this could be configured to get more power? Also how much inverter will I need for a few small appliances and one 3/4 hp jet well pump? Should I be looking at inverters more than the wattage of the system say 3000 to 4000 or are smaller inverters more efficient? I'm getting about 5 hours of good sun and the rest with some shadows. I very much appreciate the opinions and thoughts and ideas of this Board. Gina

BB. · August 2012

Re: Simple solar gal needs bigger ideas

Here is some information on inverters:

All About Inverters
Choosing an inverter for water pumping

Basically, something like 80% of your appliances will work fine on MSW, about 10% will fail (either fail to function, or actually overheat and break), and another 10% may have shorter life over time.

What tends to "fail" are inexpensive electronic power supplies and wall plug type transformers.

What tends to work are resistance heaters, filament light bulbs, universal motors (motors with brushes like drill and cake mixers), and motors that are are "lightly loaded" such as fans and such.

Things that may or may not work--AA battery chargers, tool chargers, refrigeration compressors may run hot, CFL bulbs may or may not start/run hot, etc...

Many computers will work OK (modern desktop systems), and some that may have problems are the small "net book" type computers... It is really hard to generalize (the larger computers/electronics tend to have a function called "power factor correction" while smaller power supplies and computers may not).

If you are near stores and not too worried about a small devices failing--MSW prices are hard to beat.

If you are in the middle of no-where and/or cannot have something fail (work computer, etc.), then TSW inverters (which have the same basic wave form as utility power), are hard to beat.

And the reason we keep asking you about your loads--It is sort of the difference with a VW Bug and a small trailer vs a Mac Truck with 80 tons of freight. The both do their jobs well, but they will not do each other's jobs well.

For most people, the amount of solar panels and battery bank sizing will hinge refrigerator, A/C (or not), and well pumping for irrigation. And there can be a huge difference between a desktop computer running 24x7 vs a small laptop running 10 hours per day with "sleep" activated.

A single desktop running 24x7 can use 2x the amount of total power use of an off grid home for quite a few people here.

Grid power with some sort of backup may be quite a different solution vs trying to run a home 9+ months of the year from solar (and the help of backup genset during the winter).

For some people here, they have reduced their cabin electrical usage so much through conservation--That the local electrical co-op bills were more than using solar+genset and they were close to just going off grid.

In "cities"--The building inspectors may "red tag" a home that has no electrical power (even if they have solar).

In California, the utility does have the "right" to charge people for abandoning utility power and replacing it with solar/other power sources (basically, the utility has used the customer to borrow 40 years of revenue to pay for infrastructure in "our name"--so we have to repay the utility for leaving the grid and "stranding" their assets--Don't know if it every happened or not, but it is in the regulations and has affected many larger companies that want to do co-generation facilities).

-Bill

Photowhit · August 2012

Re: Simple solar gal needs bigger ideas

:DWow, you got me on 'Horseshoe' I couldn't even find it via Google, Always thought California swamp, was 'Tate's Hell' on the other side of the dead lakes, and it might be, but it looks from the map that your pretty close to PC. Unless your talking about Horseshoe beach and the swamp and hunt camp areas down there, I think there were some communes down that way so perhaps thats the area your talking about... enough reminising...

We are not trying to be difficult, most of us like the idea of using solar and some like the idea of being 'off grid'. But jumping in is hard at best, looks like you are realistic and you get :D2:D thumbs up for that! but much of figuring out the math is having hard figures. My Guess is your 3/4 jet pump is a good place to start, I take it this is a shallow well pump. Even knowing the brand we might not be able to give you more than an idea of the current spike to start the pump. Is it currently running off a generator? if your on the grid currently, the electric company might have loaner Kill-a-watt meters (thank my mom, really! she helped put on the 'Sustanable Living' expo in Wakulla County and got some of the Electric Companies to add loaner meters to their Energy audit programs!)

I have not had any issues with MSW and wall warts, most of the 'car adapters' are MSW and pretty much made for computers/netbooks and such. ...but I agree with the rest of what Bill said. I lived on small MSW inverter @200 watt for most of 5 years, ran a couple different laptops, a 6" TV, video tape player('00-05), fans most from wall warts.

That said, a big motor like your well pump would very much like a pure sine wave. If it's running off of a genny that's a start, if it's running off the grid, you can likely read the power label on it and 1st see if it's 110/120Volt. I've never tried to run a well pump so others will likely chime in and speak to the use and pressure settings (I take it you have a big tank that the well draws water into, and the pump maintains a pressure level in the tank?) And the possibility of swapping out the pump for something more effiecent, or less spikey(new word!)

As to the Midnite classic (and all MPPT Charge controller) they take in the power within their ability to do so and output power that you need. So long as the CC will accept it you should be fine, it might run a bit more effiecently at about 2x the output, but if you can limit the number of strings of panels to 1 or 2 you will not need a combiner box (fuses for each string) so to keep expenses down 1 or 2 strings will be cheaper and simpler.

Fiddler · August 2012

Re: Simple solar gal needs bigger ideas

Photowhit wrote: »

:DWow, you got me on 'Horseshoe' I couldn't even find it via Google, Always thought California swamp, was 'Tate's Hell' on the other side of the dead lakes, and it might be, but it looks from the map that your pretty close to PC. Unless your talking about Horseshoe beach and the swamp and hunt camp areas down there, I think there were some communes down that way so perhaps thats the area your talking about... enough reminising...

We are not trying to be difficult, most of us like the idea of using solar and some like the idea of being 'off grid'. But jumping in is hard at best, looks like you are realistic and you get :D2:D thumbs up for that! but much of figuring out the math is having hard figures. My Guess is your 3/4 jet pump is a good place to start, I take it this is a shallow well pump. Even knowing the brand we might not be able to give you more than an idea of the current spike to start the pump. Is it currently running off a generator? if your on the grid currently, the electric company might have loaner Kill-a-watt meters (thank my mom, really! she helped put on the 'Sustanable Living' expo in Wakulla County and got some of the Electric Companies to add loaner meters to their Energy audit programs!)

I have not had any issues with MSW and wall warts, most of the 'car adapters' are MSW and pretty much made for computers/netbooks and such. ...but I agree with the rest of what Bill said. I lived on small MSW inverter @200 watt for most of 5 years, ran a couple different laptops, a 6" TV, video tape player('00-05), fans most from wall warts.

That said, a big motor like your well pump would very much like a pure sine wave. If it's running off of a genny that's a start, if it's running off the grid, you can likely read the power label on it and 1st see if it's 110/120Volt. I've never tried to run a well pump so others will likely chime in and speak to the use and pressure settings (I take it you have a big tank that the well draws water into, and the pump maintains a pressure level in the tank?) And the possibility of swapping out the pump for something more effiecent, or less spikey(new word!)

As to the Midnite classic (and all MPPT Charge controller) they take in the power within their ability to do so and output power that you need. So long as the CC will accept it you should be fine, it might run a bit more effiecently at about 2x the output, but if you can limit the number of strings of panels to 1 or 2 you will not need a combiner box (fuses for each string) so to keep expenses down 1 or 2 strings will be cheaper and simpler.

Hello there, I have a laptop connected to a 42" LCD screen that runs about 120 watts total for both. I have a new energy efficient Maytag 13 Cubic ft. Fridge, and a LG washer. All the lights are LED about 9 watts each. 10 or so are usually on. The pump is a Starite 3/4 hp 110 with a 20 gallon pressure tank. A 70 foot run from the battery box to pump. Coffeemaker in use a lot. Washer twice a week. A lot of grilling done outside. Two ceiling fans, that's about all. The computer and TV are on about four hours a day. I'm pretty conservative when it comes to power usage. I catch rainwater for irrigation and live a very simple life. When I hook up panels in a series should I use Y cables 2+2+2+2? and if I wanted to relocate the panels about 70 ft away from the batteries how much voltage would I lose?

vtmaps · August 2012

Re: Simple solar gal needs bigger ideas

Fiddler wrote: »

When I hook up panels in a series should I use Y cables 2+2+2+2? and if I wanted to relocate the panels about 70 ft away from the batteries how much voltage would I lose?

I think that what you are trying to say is that you want to put two panels in series (which makes a string) and have four of these strings in parallel. You will need a combiner box to put the strings in parallel, and each of those four strings will need a circuit breaker in the combiner box. The combiner box is weatherproof and very near the panels. You also need a ground rod and lightning arrester at the combiner box. Then you run a cable from the combiner box to your charge controller. You will want the 70 ft cable to be at least 6 gauge copper (4 gauge would be better), and it should be buried in conduit.

Look at the Midnite solar combiner boxes and lightning arresters. Midnite has a good website and you can buy them at a good price from NAWS.

btw, for your inverter and charge controller you should consider one of Midnite's prewired E-panels. It comes prewired with an inverter of your choice, charge controller, circuit breakers, bypass switch, ground fault device, lightning arresters, etc. Just screw it to the wall, connect it to your battery, generator, 70 ft controller cable, and AC distribution panel.

--vtMaps

Photowhit · August 2012

Re: Simple solar gal needs bigger ideas

When I hook up panels in a series should I use Y cables 2+2+2+2?

NO, if you want to do strings of 2, hook one to the other and then into a combiner box with 4 fuses or breakers (info on fuses per string is on the back of the panel. If you can and want to do strings of 4 panels, first check the sizing tool, most of the info will be on the back of the panel, other info will be the high and low temps in your area and how your going to hook them up. (Classic sizing tool). If you can do strings of 4 you can hook 4 up in a string (possitive to negative) then use a 'Y' to connect the 2 strings. If the batteries will be 70 feet away this will also help with voltage loss as you will be running higher voltage, higher voltage will mean less current(amperage) wire size is based on amperage and voltage drop across a distance 140 feet round trip might be OK on 10 gauge wire at 120 volts. You can check a voltage drop calculator Sorry no link right now One of the great mods will come along and post a link shortly(I hope!)

10 lights 'usually on' would not be considered conservative in this crowd, that's 90 amps an hour x 24 hours or over 2Kwh a day. If you've done most of your conserving, what is your monthly Kwh usage? My guess is your fridge will be 2 Kwh per day (energy effiecent use 1-1.4 in a controller room but if you don't use air conditioning it will use more! Is your solar water heater a siphon pump or are there water pumps involved there as well?

A couple loads a week laundry isn't much, if you have a front load that's a plus! The TV/Laptop 4x 120 watts or 500Watt hour isn't too bad, I think my LED/LCD uses close to 70 watts and it's 32 inch. Coffee maker might be a pretty heavy draw, might want to put a kill-a-watt meter on it, be sure to turn the warming element off after you make your coffee, use a thermos to keep the coffee warm if needed, warmers use a good bit of electric.

Ceiling fans can be hit and miss, might check the current with a clamp meter, dodging the blades will be tricky (likely be able to check at the switch...lol)

Photowhit · August 2012

Re: Simple solar gal needs bigger ideas

If you choose to go 'off grid' you will find that you know what your current uses are, right now I'm running;

Wall warts charging cell phone, N900(minicomputer playing an audio book) and mini speakers for same, total less than
<10 watts
2 - 13Watt CF lights
26 watts
wall warts for media player and TV (I just turned them on from power strip, it takes a while to load the media center from 1tb HD, it's pizza night:D without pizza

I went to town this afternoon.)
@10 watts
1 - 4watt LED bulb outside light
4 watts
fridge on thermostat
@1.5KWH a day.
1 honking big central air ("No sin greater...")
...more than I want to think about, it will be retired after this summer, when I take this place off grid.
water heater is off and the water is hot enough for my showers in the morning and Friday morning, unless I do a lot of cooking then I'll flip it back on for an hour.

I'm using about 20 KWH a day currently, we've had a heat wave and drought and I work security and needed to come home to a cool house. I ran last month on a more conservative mode and was down to 11KWH a day, turning off the central air when I left. I actually would be close to maintaining 20 KWH's a day with a 6.5 Kw array I will setup. After summer my use becomes very low.

If off grid I would likely air condition a single room through out the day and use a mini split on low to keep the large room/kitchen area from roasting. I also have a small cabin designed to be off grid and air conditioned and could stay there through out the summer if needed(it currently only has an fridge running...lol). I'm impressed you can manage Florida with out air conditioning. I managed here (central Missouri) for 5+ years but we normally cool down over night.

Time to turn off the audio book and watch a movie, while I pretend to pick up around the living room...lol

BB. · August 2012

Re: Simple solar gal needs bigger ideas

Hi Gina,

Taking a guess:

Fiddler wrote: »

Hello there, I have a
0.56 kWH per day = 0.1120 kwatts * 5 hours per day laptop connected to a 42" LCD screen that runs about 120 watts total for both.

1.0 kWH per day Maytag 13 Cubic ft. Fridge,

0.250 kWH per day LG washer (per load estimate, washing only, no water heating/steam heating).

0.90 kWH per day = 0.009 kW * 10 lights * 10 hours lights are LED about 9 watts each. 10 or so are usually on.

0.33 kWH = 1.0 kW * 1/3 hour per day The pump is a Starite 3/4 hp 110 with a 20 gallon pressure tank.

======================
3.04 kWH per day (if I did my math right) [oops--missed the x10 LED lights--fixed]

I am going to round up to 3.3 kWH per day (100 kWH per month). That will allow for some days with more usage, and support additional loads (which tend to grow over time).

Note, for the math below--I am carrying out digits to reduce round off error, and to make it easier for you to check my math (I ain't perfect

). Choosing hardware within ~10% of the below--is virtually the same for solar calculations.

Nominally, we recommend a 1-3 days "no sun" battery and 50% maximum discharge. Use 2 days here for this example (is a happy medium):

3,300 WH per day * 1/48 volt battery bank * 1/0.85 inverter eff * 2 days "no sun" * 1/0.50 max discharge = 324 AH @ 48 volts

Next, charging the battery bank. We recommend from 5% to 13% rate of charge... With 10% being a good minimum for a fast recharge/good battery life:

323 AH * 59 volt batt charge * 1/0.77 panel+controller deratings * 0.05 rate of charge = 1,241 watt array minimum
323 AH * 59 volt batt charge * 1/0.77 panel+controller deratings * 0.10 rate of charge = 2,483 watt array nominal
323 AH * 59 volt batt charge * 1/0.77 panel+controller deratings * 0.13 rate of charge = 3,227 watt array "cost effective maximum"

Next, we need to estimate the power based on how many hours of "noon time equivalent sun" per day.

I am not sure where you are at--but using PV Watts for Tallahassee Florida with fixed array pointing south at latitude, we see:

Month    Solar Radiation
(kWh/m 2/day)
1      4.10     
2      4.86     
3      5.07     
4      6.05     
5      6.15     
6      5.73     
7      5.28     
8      5.52     
9      5.38     
10      5.32     
11      4.51     
12      3.92     
Year      5.16

Tossing the bottom three months (assume you would make up balance with generator), that would be February with ~4.86 hours of sun per day (20 year average):

3,300 Watt*Hours per day * 1/0.52 system end to end efficiency * 1/4.86 hours of sun per day = 1,306 Watt solar array

So, the "ideal array" for your place would be from ~1,306 Watt to 3,227 Watt solar array.

If this was "backup power system"--You may tend towards a 1,306 watt array (minimum amount of solar panel to meet your needs for ~9 months of the year).

If this was a full time off grid home--You may tend towards the 2,483 watt array (better for battery life, you could support more loads, if needed).

A 70 foot run from the battery box to pump.

A longer distance favors higher voltages--Probably 120 VAC minimum. A 120/240 VAC split phase inverter would be nice to run at 240 VAC.

There are other, much more efficient pumps--But if your well use is light, then it is probably not worth the money for a new in-well pump like a Grundfos (these are great pumps, AC or DC power, even run off solar panels only). And much more efficient. If you were to use a small "slow pump" (even solar panel only for daylight pumping)--It would fill a cistern and then use a small DC pump to pressurize the home.

Coffeemaker in use a lot.

Oops... Not on list. Using a propane powered "Mr. Coffee" is a possibility--And use a thermos to keep warm during the day.

Washer twice a week.

Check

A lot of grilling done outside.

Keep home cool. Check

Two ceiling fans, that's about all.

Those can use a fair amount of power, or not (watts*Hours per day)... There are some DC versions that are supposed to be very energy efficient.

The computer and TV are on about four hours a day.

I rounded up to five hours per day.

I'm pretty conservative when it comes to power usage. I catch rainwater for irrigation and live a very simple life.

3.3 kWH per day is a "good size" system for an off grid home with a "reasonably" modern lifestyle.

When I hook up panels in a series should I use Y cables 2+2+2+2? and if I wanted to relocate the panels about 70 ft away from the batteries how much voltage would I lose?

In general, don't use "Y" cables. Instead, you will probably need a "combiner box" (with internal fuses or breakers) plus a negative bus bar (more than two parallel strings require the fuses/breakers for safety).

Assuming you use a MPPT charge controller and/or 48 volt battery bank, array to charge controller/battery box should not be too much of an issue.

Note the above assumes a 48 volt battery bank... With the sizing above, you could possibly go with 24 volt too (if you need 24 VDC pumps, for example)... Need to look at things a bit closer.

But, before we go down the road of details--Want to make sure my assumptions about your power needs are correct.

Also, the shading still bothers me--If you have shading between ~9am and 3pm, you can lose a lot of power--Solar panels just do not work very well with any shading. And from 9-3 is the prime generating time (winter may be worse with lower sun angle).

-Bill

Fiddler · August 2012

Re: Simple solar gal needs bigger ideas

Wow, You guys are thorough! I'm getting the picture here but still moving ahead with this. Question: I saw an all in one controller board from Missouri Wind and Solar. Is this any good? It looks good but doesn't go into much detail about any MPPT. How I came across this I was thinking of adding a wind turbine to do night duty and they had a turbine I was looking at and saw this all in one control board. ($698) Cabin located between Horseshoe and Suwannee.

icarus · August 2012

Re: Simple solar gal needs bigger ideas

Fyi, Missouri Wind and solar does not have the greatest reputation on this forum. I am not proffering an opinon, but you might do some research.

Tony

BB. · August 2012

Re: Simple solar gal needs bigger ideas

Personally, I am not a big fan of small wind--I think it does not supply much power and demands a whole bunch of maintenance (time and money). The turbines are usually not too expensive--It is the tower and the installation that is typically the excessive costs. Also, you may have to take the turbine down every year or so (+/-).

If you are interested in wind power, here are some links (wind power supporters):

Wind Power Links
www.otherpower.com (good forum for DIY Wind Power)
Hugh Piggott - Scoraig Wind Electric site for tons of info (from mike90045)
www.greenpowertalk.org (added from "russ"--Like here but more wind/less solar)

I have some other links with wind problems--But we can leave that for another day.

My suggestion, start with solar/grid backup/generator backup first. Then once you have a stable system, look to wind (if you still want) to supply power during cloudy weather.

More or less, you need a 60' tower, 500' from any obstructions, and 30' above local obstructions. Most places, you should be seeing "flagging" trees from prevaling wind (although, I have heard that Florida does not really have prevailing winds). And, most turbines do not generate much in the way of power until 11-12 MPH, and rated power around 25-30 MPH--And many shutdown above 35-50 MPH winds.

Basically, you only get power when it is miserable to be outside from the winds. It is true that good 12' wind turbine may generate 400-600 kWH per month in a good area with steady winds--12-15 mph wind 24 hours a day * 30 days per month (it averages out--higher wind velocity for shorter periods, etc.). But, for off grid use, you are usually limited to storing about 2-3 days of power in your local battery bank--So excess wind power (and solar) is lost.

If you have lightning in your area--A whole new kettle of fish (60' tower and lightning strikes).

-Bill

Photowhit · August 2012

Re: Simple solar gal needs bigger ideas

Florida (Tampa to Tallahassee) is very bad for lightning, and while no regular wind, you should have a sea breeze much of the year with winds just after dawn and sunset as the land or sea cool and the wind goes with the rising and lowering pools of air. I'm not a huge fan of wind, but it might be viable.

Look like you have close to 4Kw of solar array, paid for and ready to be hooked up. That is a pretty sizable system. You might well be just fine. Even in Missouri, Missouri Wind and Solar doesn't have a great rep.

I think at 4 Kw I'd be looking at a 48 volt system, this will be a choice made for a lifetime(or at least expensive to change) While your Charge Controller (CC) will adapted easily to a different voltage, inverters and batteries don't. Inverters are voltage specific and it's not good to mix old and new batteries (some of that reasoning about getting the batteries on a charging/maintenance cycle) if the L16 are truely new adding 4 more now might not be a bad idea. If your conserving as much as you feel is practical, your electric bill will give you, and us, a good idea for your KWh usage. your big expenses will be a Cc and an inverter.

The 24 vs 48V is important, I had built a cabin and figured to be there for the forseeable future and bought a 24 Volt fork lift battery (often the best bang for the buck) with in the next couple months I found someone selling a 2000 model mobile home on 2.2 acres for silly cheap price ($12K), now I wish I had gone 48 volt... The battery may last 20+ years so I'm stuck undersized. I'll go back to golf cart batteries at the cabin.

Fiddler · August 2012

Re: Simple solar gal needs bigger ideas

Thanks for the heads up on Missouri Wind. I was exploring all options for a control panel with as much work completely done. I need a plug and play control system. The all in one control board they had offered looked old school but not terribly efficient. I don't have any photons to waste. So I'm looking over my choices not wanting to buy anything twice while I'm getting this project together. Question: on the combiner box what exactly has to be in the combiner box and its proper location? Also do I need a separate DC disconnect? I'm trying to get a shopping list together of the components it will take making sure I get the right stuff. Gina

Photowhit · August 2012

Re: Simple solar gal needs bigger ideas

You may not need a combiner box if you'll run your numbers through the Midnite classic sizing tool...(dang I've heard that before) if you decide your going to put up the additional panels, you'll need one, so... a combiner box normally goes close to the panels so you only need to run a single set of wires back to the Charge Controller. Seriously if you do consider "...relocate the panels about 70 ft away from the batteries..." You will want to run higher voltage from the panels to the CC, in warm Florida weather you might well be able to run 2 strings of 4 panels, even if you have to go with a classic 200, rather than a classic 150. The Sizing Tool will tell you where the cut offs are for each.

If you want to make life, and by life I mean wiring, easier, I think you can order and E-panel, a Midnite Classic charge controller and an Outback, or Magnum inverter from Northern Arizona Wind and Sun and have it all prewired! Prewired system link. You might also consider some lightning protection for the box (CC and inverter)

While I was on site at NAWS I saw that they had a link to a Home Power article on choosing an inverter for water pumping, though the article is for an off grid system...

I like to have both a DC disconnect (between the battery and inverter) and an Array disconnect (between the combiner box and the CC) I think the E-panel is setup that way, or can be it has a a spot for an Array disconnect (not sure this is required by code but makes life easier if you ever need to service panels.

vtmaps · August 2012

Re: Simple solar gal needs bigger ideas

Fiddler wrote: »

Question: on the combiner box what exactly has to be in the combiner box and its proper location?

Didn't this get answered in post #16 and #17? The configuration of the panels and the combiner box will depend on your battery voltage. If you go with a 24 volt system (which was your original preference) you should go with 4 strings of 2 panels in series with a Classic 150 controller. If you go with a 48 volt system you will need 2 strings of 4 panels and a Classic 200. If you do go with 48 volts, an even better solution would be to acquire 1 more panel and go 3 strings of 3 panels with a Classic 150. The classic 150 has higher current (and wattage) capacity than the classic 200 and either classic will run cooler and more efficiently with a 3 string of 3 panels configuration than a 2 string of 4 panels configuration.

Fiddler wrote: »

Also do I need a separate DC disconnect?

The E-panel has all the breakers and disconnects you could want. Do you mean a disconnect on the combiner box? It is nice to have an external disconnect on the combiner box, but if you don't have an external disconnect you can just open the box and flip the breakers for each string of panels.

--vtMaps

Simple solar gal needs bigger ideas

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