Solar system configuration for newbie

zbowdawg

Greetings,

I am new to solar and new to forums, so even though I looked for answers, it's confusing and therefore I am sure I am going to ask for information that has been covered a thousand times before...  I apologize in advance.  BTW, I suck at math.

So that I don't blow up any equipment or waste money on components that wont work together, here is what I have so far:

I was given six 12 volt, 200 watt mono crystalline panels:

• Maximum Power Output:  200 Watts
  
• Max Operating Voltage (Vmpp):  21.052Volts
• Max Operating Current (Imp):  9.50Amps
• Open Circuit Voltage (Voc):  24.335Volts
• Short Circuit Current (Isc):  9.87 Amps
• Module Efficiency:  17.3%

I bought two Renology 12 volt, 200Ah, Deep Cycle AGM Batteries:

• 200Ah@10hr-rate to 10.8V @25°C

I would just like to run some household appliances during the day and at night... one or more depending on what I can build to support them.  The heavier load support and for the longest amount of time is preferred.

I think I have a basic idea of set-up configuration; panels to charge controller, charge controller to battery bank, battery bank to inverter, inverter to load (appliance).

What I don't know is:

• Whether to set up the panels in serial or parallel
• Whether to set up the batteries in serial or parallel
• What would be a good charge controller, brand and model
• What would be a good inverter, brand and model

I believe that depending on serial or parallel would determine the system voltage, but I don't know how that affects anything else.  

With everything above in mind, are there any recommendation to what direction I should try and then recommendations for a compatible charge controller and inverter would be super appreciated.  I'd like to get the best bang for my buck utilizing all the panels and both batteries without spending a fortune on the charge controller or inverter for my first set-up attempt .

If anyone has easy ways to help me understand solar systems and the mathematics that go into designing efficient systems, I would love to hear from you.

Many thanks for any/all assistance.

BB.

zbd,

Welcome to the forum.

Are you in/around Phoenix Az? (amount of sun per day/season)

Ideally, you should start with identifying the loads you want to run, and there average watts and amount of energy Watt*Hours per day each uses. Off grid solar power is never cheap--And using energy efficient appliances is very helpful (LED lighting, Laptop Computer vs power hungry desk top computer, etc.).

Getting a Kill-a-Watt type meter and measuring your daily power usage for each appliance/device will help you plan your system out:

https://www.solar-electric.com/kiacpomome.html

Experimenting with the meter and your loads, will help you understand the math underlying power usage and planning out your solar power system.

Also, batteries do not like to sit for long times uncharged--Recharging your batteries for 1 day every 1-3 months (AGMs stored in cool location) will help prevent them from dying an early death.

-Bill

Estragon

Two pieces of info needed for us to help. First, your approximate location and type of use (eg off-grid summer cabin). Second, what loads you're hoping to run and for how long. Basically, the loads should inform all configuration and equipment choices, so we need to know; a) peak wattage for everything that may run at the same time, b) the total watt-hours used each day, and c), if there are any 240v loads such as water pumps (assuming North America).

zbowdawg

Greetings Bill and thanks for responding.  

I am in one of the outlying urban communities of Phoenix, so lots of sun.

I ordered a kill-a-watt meter a few days ago and it should be delivered later today, so that's a start.

Here is what I had in mind for a beginning project...  there are only my wife and myself in our 3 br house.  My wife is disabled and requires several types of medical support equipment that runs 24/7 in our master bedroom.  My wife's equipment seem to have little draw on our power consumption but our house a/c kills us.  I purchased a 1375 watt portable a/c unit.  It does an awesome job keeping our master bedroom nice and cool and allows me to shut off the house a/c during peak power usage times defined by our utility service.  I haven't determined the portable unit's peak surge when the compressor kicks in yet.  I would like to try to power that portable a/c for 3-4 hrs per day.  That's it.  However, I would like to build a system with components that I can continue to build on as I learn more.

My batteries will be banked in my garage or in a spare bedroom if the garage is too warm.

Any other info or recommendations would help greatly appreciated.

Zbowdawg

zbowdawg

Greetings Estragon and thank you for responding.

I believe I may have answered some in part in my response to @BB. , of what you mentioned to look for...  nothing that I am looking to power at this time will be 240v.  Just one item to start off with my build, but will add more as I learn.  Once I get the kill-a-watt I ordered, that may help determine the others you listed.

Any other info or recommendations would help greatly appreciated.

Zbowdawg

BB.

Generally, if you want to save money on your energy bill, you need to 1) conserve energy and 2) look at grid tied solar (solar panels to GT inverter to AC main breaker panel).

Off grid/battery based solar power systems will almost never save money vs utility power (off grid solar tends to run $1.00 to $2.00+ per kWH. Utility power runs around $0.10 to $0.30 per kWH).

However, local laws and utility regulations also greatly affect how much GT Solar can save you, and in many cases, can make GT Solar illegal.

Bill

zbowdawg

Thanks Bill.

I understand the part about conserving, but for the part about being grid-tied, not so much understanding there.  For example, our electric bill last summer pushed $450 month and was due to a/c usage only.  We didn't even turn on the furnace this past winter and our electric bills were in the neighborhood off $100.  During the months a/c is needed, if I were to eliminate the need to run the a/c using on-grid power for just 4 hrs, it seems I might be able to save $350 per month...  and that is just using something I throw together for a few hundred dollars to start, considering the panels were given to me.  I am not necessarily drilling down to the kWH cost per hour, but the bottom line dollars savings per month.

Zbowdawg

BB.

Insulation and mini-split AC systems can save a lot of money.

Double pane windows, summer shading of Windows and walls, attic insulation. LED TV, you're off appliances you aren't using (DVR, Sat receiver, computers). Laptop computer instead of desktop computer...

Energy Star refrigerators, LED lighting, etc. both save energy costs by issuing less power, they also have energy because they don't put that extra heat into the building which you have to pay to remove via AC.

Bill

zbowdawg

Totally understand.

All our windows were solar shielded last spring, already have double pain window throughout, all lights are LEDs.  The refrigerator is a concern as well as the hot water heater, but the water heater is turned off most of the year because tap water is hot to begin with here. 

The attic insulation is something I have to look into.  We have several computers that I built that are water cooled and generate less heat than can be felt directly next to them, so they are good to go.  My wife's medical equipment, well, there is little i can do about those. 

Basically, there are less than a handful of items within our house that have not been converted to save energy, that can be.  Refrigerator, hot water heater, insulation and some very minor weather striping issues are still being worked on.  Even our house a/c is less than 1 year old and is energy star compliant. 

Our utility company rates where we live are some of the highest I have experienced in my 40 years of adult life and we have lived in AZ, CA and WA.  So, it is with our utility company where we should begin eliminating the need for 100 percent reliance of our power requirements.

If I can move just one or two heavy load appliances, even part time, away from our utility, I will have a much better experience and savings.  To boot, I am making my system 100 percent portable, so it goes where we go, when we go.

Thanks again Bill.

Photowhit

To give you an idea of what you are looking at expense wise, for a load that is 1375 x 3 hours a day, if the AC runs continuously during the 4 hours.... I would suggest a 24 volt system to keep wire size and voltage drop down. If you seriously intend to expand the off grid system (as Bill said they are rarely cost effective compared to the grid) I would suggest going to a 48 volt system.

...with 6 panels I'd do 2 parallel strings of panels, with a potential of 1200 watts coming in(more on this later) You would have roughly 1200/24= 50 amps, an MPPT type charge controller would run about;

 $600 for a Midnite Classic (limited to @90 amps output for expansion);
https://www.solar-electric.com/mnclassic.html

 Other options would be a Morningstar MPPT 60 about the same price, and Outback FM80 which would allow up to 80 amps output and save you about $170, Be aware this requires a mate to do some of it's advanced programing, but I think can work out of the box for you. Someone will correct me if I'm wrong.

https://www.solar-electric.com/outback-power-flexmax-fm60-150-mppt-charge-controller.html

There is an option of using a cheaper PWM charge controller, but since this would require a combiner box and the panels have a somewhat higher VMP It doesn't really save you money and you would lose some charging ability.

An inverter to run a 1375 watt air conditioner, will not be cheap. It's might work on a 2000 watt inverter, but it would be a close thing. The compressor is an electrical motor and will 'like' a pure sinewave inverter. These will not be cheap in general. A new unit like a Samlex 2000 will cost $650 and is about as inexpensive an inverter as I could recommend. It's not particularly efficient peaking at 85%. It's UL rated only for vehicles but can be hard wired.

https://www.solar-electric.com/samlex-pure-sine-wave-inverter-pst-2000-24.html

On top of this some safety measures should be observed. A DC breaker box with breakers from the Array coming in (I would combine the 2 strings at the array) and a breaker from the output to the battery as well as a large DC breaker for the inverter. These Midnite DC boxes come with the large DC breaker for about $200;

https://www.solar-electric.com/midcdipocepl.html

Add some wiring and frame work to setup the panels and You would be looking at $1600-2000 guesstimate.

What would you get for that?

I think you average about 6 hours per day of usable sunlight. Your panels will normally produce about 75% of their label rating about 150 watts each or 900 watts for the array. You can charge the batteries and run off them and the system losses will be huge roughly 50% perhaps more with the poor inverter. Better would be to let the batteries charge until they hit Float and then turn on the Air conditioner. In this manner you won't try to store and use energy from the batteries, drawing only the difference your array can't provide. 

The big trick is you need to turn off the AC once you have used your rough daily allotment so the batteries can recharge while the sun is still out. In this manner you might get to use 90% of the energy taken in. 

About 3 hours... Your inverter at 85% efficient makes the AC load about 1600 watts. In 3 hours you will use 900 watts from the array and 700 watts from the battery bank. the battery bank wastes some energy in storage, so you will need roughly 3 hours to recharge the 2100 watts used.

BB.

To add to what Photowhit said... A little math. Say Phoenix AZ fixed 1,200 Watt array:
http://www.solarelectricityhandbook.com/solar-irradiance.html

Phoenix
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 57° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
4.92	5.55	6.45	6.83	6.74	6.57
Jul	Aug	Sep	Oct	Nov	Dec
6.08	5.78	6.03	5.82	5.24	4.74

And you average around 6 hours of sun per day in the summer:

• 1,200 Watts * 0.52 off grid end to end AC system eff * 6.0 hours of sun per day = 3,744 Watt*Hours per average summer day

I took a quick look, and the most expensive summer power $0.135 per kWH (guessing)...

• 3.744 kWH per day * $0.135 per kWH * 30 days per month = $15.16 per month "savings" for Off Grid (Battery based) system
  

A similar GT solar system would look like:

1,200 Watts * 0.77 off grid end to end AC system eff * 6.0 hours of sun per day = 5,544 WH per day (Grid Tied)

• 5.544 kWH per day * 0.135 per kWH * 30 days per month = $22.45 per month "savings" for Grid Tied
  

So, what is your electric rate--And is $15 to $22 per month a "big" savings for you? Note that your Off Grid system harvest is "at best"... You have to manage the power usage to use even 75% of the available harvest (using 100% of your off grid harvest is very difficult).

-Bill

zbowdawg

Thanks @Photowhit

It's nice that someone decided to help instead of throwing out all the reasons it won't work.  I appreciate that you took quite a bit of time going over the various components.  It is very much appreciated. 

I have tried on other solar forums to get answers and assistance and it seems like most folks that have the knowledge, guard it like Ft Knox and just ignore what someone might be asking.  I get the impression that folks in the solar field, just want to sell grid tied set ups without listening to what someone may be looking to do or try on their own...  most of what I have heard in forums including this one, is it's grid tied their way or it wont work.

I am not going to waste any more of my time on this forum but I did want to thank you for your assistance.

petertearai

  Quote  " If anyone has easy ways to help me understand solar systems and the mathematics that go into designing efficient systems, I would love to hear from you."
You got some very good advice  . pity you did not appreciate it .

zbowdawg

One person gave me good advise pertaining to my request regarding equipment, @Photowhit.  I thanked him and I am very appreciative of his information and the time he took to put it together.  Another, BB., provided some good info on maintaining and battery storage, I thanked him but unfortunately, he proceeded to sell grid-tied systems and stopped being helpful.  That's it...  the few other comments only told me what couldn't be done and attempted to prove it and offered no advice whatsoever only that I should go grid-tied.  @petertearai, you also have provided nothing of value and have placed yourself along side the other useless information and worthless comments.  Why don't you re-read what I was requesting. look at all the comments and see there is only one that provided what I asked for and I thanked them.   Your only quote was my last sentence?  What about all the specific information that I was looking for answers or advise to?  Only one person answered those, and it wasn't you.  If you missed what I was requesting in my lengthy post and only caught the very last sentence , then you have proven the point of my last post, thank you.

mike95490

zbowdawg said:

Greetings,

I am new to solar and new to forums, so even though I looked for answers, it's confusing and therefore I am sure I am going to ask for information that has been covered a thousand times before...  I apologize in advance.  BTW, I suck at math.

So that I don't blow up any equipment or waste money on components that wont work together, here is what I have so far:

I was given six 12 volt, 200 watt mono crystalline panels:

• Maximum Power Output:  200 Watts
  
• Max Operating Voltage (Vmpp):  21.052Volts
• Max Operating Current (Imp):  9.50Amps
• Open Circuit Voltage (Voc):  24.335Volts
• Short Circuit Current (Isc):  9.87 Amps
• Module Efficiency:  17.3%

I bought two Renology 12 volt, 200Ah, Deep Cycle AGM Batteries:

• 200Ah@10hr-rate to 10.8V @25°C

I would just like to run some household appliances during the day and at night... one or more depending on what I can build to support them.  The heavier load support and for the longest amount of time is preferred.

I think I have a basic idea of set-up configuration; panels to charge controller, charge controller to battery bank, battery bank to inverter, inverter to load (appliance).

What I don't know is:

• Whether to set up the panels in serial or parallel
• Whether to set up the batteries in serial or parallel
• What would be a good charge controller, brand and model
• What would be a good inverter, brand and model

I believe that depending on serial or parallel would determine the system voltage, but I don't know how that affects anything else.  

With everything above in mind, are there any recommendation to what direction I should try and then recommendations for a compatible charge controller and inverter would be super appreciated.  I'd like to get the best bang for my buck utilizing all the panels and both batteries without spending a fortune on the charge controller or inverter for my first set-up attempt .

If anyone has easy ways to help me understand solar systems and the mathematics that go into designing efficient systems, I would love to hear from you.

Many thanks for any/all assistance.

I apologize in advance.  BTW, I suck at math.

Then this is going to be rough,  even rougher if you do not understand electricity & electrical theory.

First, you are mentioning batteries and chargers, which means you are shooting for a off grid system.   Batteries have a continual replacement cost, so any system with batteries will never be a money saver, will never break even.  Your $, I don't care, this is what you are asking for.    Might try reading this https://archive.org/details/fe_Solar_Power_Your_Home_For_Dummies

before you go too much further.   There is a newer version out in bookstores, if you like.

PV panels, well aimed, put out 80% of nameplate for about 20min at solar noon.  for 2 hr before and 2 after, you have diminishing power

To charge your 24V battery, put 3 panels in series, the other 3 in series, and then parallel the 2 series strings.

You have 1,200w of panels @ 80% nominal gives you about 950watts  - at 28V is about 35 charging amps

Batteries, just like the electric grid, are more efficient at higher voltages.  Series wire the batteries for 24V. you will have a 24V 200ah battery.   AGM batteries will not likely last past 5 years.   This bank has a capacity of 4,800 watt hours. 20-30% is usable on a daily basis for longest battery life.

Solar Charge Controller - I recommend the Morningstar MPPT 60.  It has a WWW interface that a properly configured laptop can use, so you don't need to buy a meter. Flexible, silent, programmable.

First rule of solar living - once you batteries are charged by noon, fire up the optional loads, laundry, water pump, use the power, or loose it.   Loads you run off the sun are free, if you have to deplete your batteries at night, you start to worry about battery life and blackouts.

Inverter.  If you suck at math, this won't be fun at all.    Small inverters have low tare losses. Larger inverters have larger tare losses.

Sizing/Predicting  your loads is tough, better if you can use a existing electric bill, live frugally for a month, see what you consume. If you select a large inverter to power the steam iron and microwave at night, and still expect ice in the fridge, you will need a much larger system than if you want to power a couple LED lights, laptop and a phone charger.   YOU have to come up with the load estimate, and get it right, nobody else can, they are just guessing.  Adding a fridge to the mix, you need at least a 1,000w inverter to be able to reliably manage the starting surge.

And then there is the backup generator and charger.  A couple cloudy days, and the batteries are depleted, and begin to sulfate. So it's either sit in the dark, and then buy new batteries , or spend $ for generator and charger.

Now at this point, I stop and ask questions of you.

 1) Is this off-grid

  2) do you have grid power at the site

 3) batteries add tremendously to the system cost

4) going off grid will be a major life style adjustment.

5) where does water come from, well, pond,   what do you need to pump with?

6) this is a pretty small, basic system, not a entirely comfortable one, should be able to run an efficient fridge on it.

BB.

Just to be clear--You asked for the best bang for your buck. And I simply listed the amount of energy you can harvest for both Off Grid and On Grid systems in terms of Watt*Hours and cost vs grid costs.

I was not "selling" GT... I was just using math to show the amount of harvest per month in basic terms for both types of systems (both in energy and in money for the power bill).

You appear to want to save money on your power bill of $450 per month... And an Off Grid system in the middle of summer (6 hours of sun) with 1,200 Watts of solar panel will save around 3,700 WH per day or around (3.7 kWH per day * 30 days=) ~111 kWH per month.

How many kWH per month is your present utility bill, and will ~111 kWH per month (in summer, roughly best case) save you much money?

Off grid systems are expensive both to install and maintain (batteries typically last ~5-7 years, inverters+charge controllers last ~10+ years), and the reality is that if you want to save money, the energy harvest from an Off Grid system is (very roughly) 4x-10x the cost of a Grid Tied system (~$1.00-$2.00 per kWH and possibly down to $0.50 per kWH if you really shop around and take care of your batteries vs $0.15 to $0.20 per kWH for GT).

If the numbers for an Off Grid system are OK with you--No problem finishing the design with picking the equipment is not a problem. I try to do the design process in two steps--One is the basic math to size the system and estimate its performance. The second is to select the equipment to support that design.

You actually never said that the performance of the off grid system would meet your needs or not... I was just waiting for that feed back from you.

-Bill

MrM1

And Bill,  he actually never said

1. Are you trying to save money?  (Bill suggested it  but the OP never really said this)
2. Are you trying to be energy independent?
- meaning you are not concerned about saving money,  you just want power regardless of the grid
3. Do you need a constant stable supply of power regardless of grid stability for the medical equipment and to cool one room
4. Are you just trying to be green.  (there really is nothing really green about off grid with battery.  It is a "feel good" illusion)

Being off grid with batteries when grid power is available will not accomplish #1.  These folks here  where simply pointing out, if #1 is your goal there are better ways to accomplish this than going off grid with battery for your primary loads.

I can tell you, after doing partial off grid for 7 months,  my system (see my sig) "saved" me about $20-30 a month in power off my power bill.  My system will never pay for itself.  I knew going in that saving money was not my goal.  I was doing the system as a hobby and for energy independence (not have to run a generator all the time during outages especially after a hurricane).  The loads I run from my off grid system are, Fridge, all LED lights in the home, Fans, TVs, Modem/WiFi router, well pump and have a diversion load set up to heat water in my water heater tank.  I can also run the washing machine at the flip of a switch if there is enough sun light (I would not run the washer off the battery)

I asked in this thread if the system I have could possibly also power a small hi seer low BTU mini-split.   My system in it's present config running the current loads would not do it for long each day,  and I would probably have to give up hot water heating.  I do not think the battery bank would power a single mini split with my other loads (less water heater) very long at night from battery.  But the system I build (see link in sig) would be a starter for someone trying to do what I have done.  My daily Watt Hours for the loads described above (less water heater diversion) are between 3000-3800 watt hours per day.  No AC cooling/heating in that.

If you say your goal is #2 and/or a combo of #2  and #3 then cost of system, and saving are of no real value to you.  And no one except you can put a price on the value of #2 and #3 for you.  if 2 and 3 are your goal,  the value is really priceless. 

If you would like to know what I have invested in the self installed system in my sig,  send me a Private message.  I self installed the system. 

Regardless of your motivation,  you must realize,  an off grid system will cost you a good bit more than a grid-tied system.  And it will take a very good commitment to the system to keep it running and healthy for years to come.  You have to check the battery electrolyte regularly to keep the water at the proper levels in the batteries (unless you have AGMs). 

Good luck with your endeavor 

BB.

zbowdawg said:

Thanks Bill.

I understand the part about conserving, but for the part about being grid-tied, not so much understanding there.  For example, our electric bill last summer pushed $450 month and was due to a/c usage only.  We didn't even turn on the furnace this past winter and our electric bills were in the neighborhood off $100.  During the months a/c is needed, if I were to eliminate the need to run the a/c using on-grid power for just 4 hrs, it seems I might be able to save $350 per month...  and that is just using something I throw together for a few hundred dollars to start, considering the panels were given to me.  I am not necessarily drilling down to the kWH cost per hour, but the bottom line dollars savings per month.

Zbowdawg

MrM1

Thanks Bill for clarifying.  I was not knocking you or anyone else. Sorry if I came off that way. I missed piecing together the savings part.  Thanks for pointing that out.    The OP does seem to have a few different goals for different reasons.  No system thrown together for a few hundred buck is going to accomplish these goals.  And no system designed to accomplish the power needs off grid is going to save money. 

BB.

It can be difficult to understand what in another's mind when just typing on a forum. I try to take what people say at face value and give them the best answer(s) I can.

And I have been known to skip/miss posts too and have the wrong answer(s)...

Such is life.

And have fun!

-Bill

Photowhit

FWIW - the part that I saw and focused on was the;

zbowdawg said:

...My wife is disabled and requires several types of medical support equipment that runs 24/7 in our master bedroom.  My wife's equipment seem to have little draw on our power consumption but our house a/c kills us...
Zbowdawg

I saw this as perhaps wanting the system as a backup and seeing if some other use could be gained.

Not all reasons for doing a battery based system make financial sense. It would amaze people that my system makes sense even with power lines goin by the house.  ...but you would need to know the complete history of how I ended up here.

MrM1 said:

4. Are you just trying to be green.  (there really is nothing really green about off grid with battery.  It is a "feel good" illusion)

I've actually had my mind changed on this. 

I use to say that the only reason I could claim to be green in an off grid system is that It forced me to conserve energy and use a minimal amount. ...it does do that.

...but I've had someone post numbers on the recycling of batteries and it's really, pretty well done. and doesn't pollute nearly as bad as I thought it did. The numbers were from the New recycling plant I believe in South Carolina and again, I believe by Johnson Control. 

Unless your grid power comes from renewable resources (hydro, wind) I'd say they were close to even.

MrM1

@Photowhit you were focused and seeing the part that jumped out at me.  I kinda got zoomed in on that part to the exclusion of any other. 

And interesting info about off grid  solar.

I had thought:

- the production of panels not so good

- Lead bad

but it would be good if you are more correct.

Photowhit

MrM1 said:

And interesting info about off grid  solar.

I had thought:

- the production of panels not so good

- Lead bad

but it would be good if you are more correct.

You might consider there is pollution in all generated power, as to the energy  expelled on panels, my Evergreen's have a replacement of energy used to produce in about 8 months when grid tied, a bit under 2 years in off grid. Less since I'm a heavy user of opportunity loads.

Lead if not reintroduced into the environment has zero additional impact, LA batteries are nearly 100% recycled now including the cases. Perhaps as high a rate as anything in our industrial system.

Perhaps I am "...more correct"!