Solar Power – System Diagram
Solar power systems vary widely in their power producing capabilities and complexity.
You might say that the cost of implementation is somewhat proportional to that.
However there’s a common thread among most of them: The basic building blocks of components.
1. Solar panels
2. Charge controller
3. Battery bank (if off-grid or standalone system)
4. DC to AC inverter for AC power
I’m posting this for the beginner. The basic diagram. And an example.
The basic solar power system diagram (minus the various circuit breakers, combiner boxes, cables, shunts, grounds, and other details).
First, lets face it… To implement solar energy is not cheap compared to today’s energy from the grid. Though the costs are coming down!
One could argue that from a cost savings point of view it’s not very practical.
It may take years to reach a break-even point. Why? Because a cost analysis of a solar power system compared with that of your electric utility bill will speak for itself.
Depending on the system design and usage, the break even point varies widely.
Despite the cost of a given solar power system, for many it’s a worthwhile investment.
Example: If purchasing a new property with land far from the nearest road with electric utilities, it may actually (very likely) cost less to implement a solar power system than pay to run electricity to your property.
For the preparedness minded, simply having a very basic solar power system (or bigger) provides some peace of mind (at least it did for me).
Without going into great detail, I thought that I would illustrate a very simple and basic solar power system diagram:
Here’s a simple small 300 watt solar panel system with a 600 watt DC-AC inverter, just for an example:
You could utilize (3) 100 watt panels listed below.
According to the specs of these particular panels, the combined paralleled output would be about 20 Amps @ 12 volts DC.
The referenced charge controller would be an appropriate size for this. Though they’re available in all sorts of specifications.
The charge controller would be connected to any number of 12-volt deep cycle batteries wired in parallel (the more batteries, the more energy storage).
Optionally you could add a DC to AC inverter to power 120 volt AC devices.
100 watt solar panel, 12 volts DC from Renogy
Renogy 100 Watts 12 Volts Monocrystalline Solar Panel
Connect the 3 panels (above) in parallel using these adapters:
MC4 T Branch Connectors
This MC4 splitter will enable parallel connections of the panels listed above. Their specs will combine and add up to about 20 amps. This will maximize the usage of the charge controller listed below.
20 Amp 12 volt DC Charge Controller by Renogy
Renogy 20 Amp 12V/24V DC Input MPPT Solar Charge Controller
Renogy connection diagram
You could run 12 volt DC powered devices from the basic solar power system above.
Or you could add a DC to AC inverter to power 120 volt AC powered devices, not to exceed the rated output of the chosen inverter.
For example you might choose this 600 watt inverter:
Samlex America Pure Sine Inverter, 12V, 120 Vac, 600W
SUMMARY
It’s not terribly difficult to assemble a basic solar power system. Though it really helps to have an understanding of basic electronics and electricity!
You might think that the simple example system listed above (300 watts input, 600 watts output via battery bank storage) isn’t very much power.
However if that 300 watts of solar panels were charging a battery bank for say, 6 hours? That would equate to 1,800 watt hours of energy (1.8 kWh). Note, the battery bank would need to be sized appropriately.
See how that works? That could be enough to operate some essential systems.
If you’re interested to research this further, it would be beneficial to read up on the subject. Here’s a listing of books which may help:
Continue reading: The Four Essentials of Off Grid Solar
Read more: ‘Kill A Watt Meter’ — How to Measure Power Consumption (kWh)
Solar Power and Energy Requirements – How To Calculate Your Needs
I originally posted this article back during 2011!
I’ve updated and edited it a bit, and republished for your potential interest.
I use a single 200 watt solar panel for off grid truck camping, with a sunny day and a couple of 100 amp hour batteries it gives you charging for electronics, bright LED lamps at night, and fans. Small comforts but very useful if the power is out at home. A great way to learn the basics is to go on line to RV sites.
LED lights are definitely the way to go! WAY LESS energy consumption.
Something missing from the solar diagram is the ability to use 12 volt appliances/devices without using an inverter. Plug and play. No power loss. You can go thru Kens amazon link and find 12 volt appliances or go to any truck stop and find most anything needed to make life more comfortable. Even with a small system. TV/DVD combos, lighting, fans and even cooking appliances like crock pots, skillets, water boilers, and 12 volt coolers or refrigerators.
I like this simple version
I agree.
Thanks Ken. Good article that even I can understand!
Ken,
K.I.S.S. , keep it short &simple. Thanks for the diagram and info.
I’m confused, what are those squiggly lines?
NRP,
It’s a “green power system”. Those squiggly lines are the little electrons dancing they way to the battery!
Minerjim;
Thank you for the detailed explanation.
Thanks Ken. Here’s my beginnerly question:
Can one use the panel and battery to operate both 12v DC and 120 VAC appliances at the same time? Some sort of splitter off the battery?
Anony Mee;
Maybe I can help a little, you will also need the ‘Charger Controller’, not just the Panels and Battery, for regulating the charge to the batteries and so you don’t “over charge” them, You will also need the ‘AC Converter’ to convert 12v DC to the 110V AC.
But, yes you can pull “power” from both at the same time if you have the full setup.
PS; do not just hook Panels directly to a Battery, the panels will feed constant ‘power’ (when the sun is shining) and overcharge the batteries, The end result will be “Fried” or exploded Batteries.
NRP is correct. The only thing that would get weird in a 12 volt battery system (if you’re pulling off the DC battery AND using a AC inverter) is keeping track (measuring) the state of charge of that battery bank.
This is where it starts to get more complicated (beyond the scope of this article). But typically there’s a shunt which is used in conjunction with your other electronics – which keeps track of how much ‘juice’ is left in the batteries.
But it’s not a “show stopper” so to speak…
Thanks NRP!
Excellent illustration.
Even small systems, as described above, will provide usable energy. After that, figure out how much energy (panels/batteries) you’ll need to run what ya want. For me, it was initially a fridge. Think your typical kitchen fridge.
If that’s what your planning, a smarter way to approach it, is to check out 12 vdc or 24 vdc refrigerators and compare $$. Wish I’d have done that to start with. Any DC appliances will help to make your system WAY MORE efficient. Every time you switch from dc to ac or visa versa, there is substantial loss in the change.
Took me awhile to get it through my thick skull, power is power. DC appliances work just as well as AC. Starting from scratch, I would definitely incorporate more dc appliances. Oh well, I never was the brightest bulb on the string. Wait I mean LED string.
Plainsmedic;
You bring up a very good point, and maybe Ken can help us out here, what is the “Typical” efficient divider for converting DC to AC current?
I’m guessing one would lose 20-30% easily ?????
Outback claims 90 – 93% efficiency. For safety reasons I, personally, would use 85% to calculate my system using Outback inverters. That gives you an acceptable margin, IMHO. The inverters I am using claim 90%. I figured the power availability to be around 80% of the battery drain. Haven’t had a “brown-out” yet. I also have a ‘secondary system’. 500 Watts of PVs, 200 A/Hr of batteries, and 600 Watt inverter. If “System 1” craps out, good ol’ No.2 can pick up the load. They aren’t phase-locked, yet, but working on that.
I currently am using an Outback VFX3648. I estimate that the real world efficiency has been in the 80-90% range. Closer to mid 80’s me thinks.
There’s a calibration factor that you can fudge with while getting it accurate with remaining state of charge for your battery bank. I had to tweak it from factory settings to be more realistic with what was actually happening. I want to think it was corresponding to 84% or somewhere near that.
Incidentally, Sol-Ark claims to have the worlds most efficient inverter.
CrowBait,
I too, ended up with two separate systems. Sounds like you have a very nice system. Are you off-grid or grid-tied? I’d love to be “phase locked,” but doubt it will ever happen. 220 vac is out of reach for a simple country boy, like me. There are other options for some 220 vac
Solar powered dc deep well pumps, for example.
The more I learn, the more I realize what I DON’T know. I’ll bet you could teach me a few things.
Plainsmedic…..
PapaSmurf is correct. Your better effort, IMHO, is to search a lot. Keep track of the prices, and jump on the best deal when it pops up. There’s a lot of places that have good deals on ‘last years’ products. Since you have two systems, I would look at dedicating one to the water pump, acquire a 220VAC inverter, and manually control the water pump. Just watch the line length. Electrical lines, that is. Might even put in a 220VAC GFI, just in case.
I am not ‘off-grid’, per se. Not really ‘grid-tied’ either. Like Ken, my switchover of the mains is manual. I prefer a real disconnect to the grid. I have lockouts hanging on the wall next to the load center to prevent ‘accidental’ re-connection. I do have a few homemade automated steps in the system. Even an ‘all batteries low’, start the generator box.
Biggest drawback was I had battery problems and had to re-wire everything to 12 VDC. Half the voltage, twice the current. That really messed up the calibrations. Generator only has 12 VDC output for charging lead-acid batteries v. 24VDC. My bad. I should have seen that. Next step is to get back up to 24 VDC on PVs and associated equipment. Twice the voltage, half the current. Then, if $$$ and time allow, re-wire system to 48VDC and have 24VDC backup system. Won’t be a bad thing unless other people keep winning the lottery.
Plains med ,,,
12 v. Dc frig v 120v Ac ,,,,better off to run the inverters and 120 v ac as far as power consumption ,been there ,done that ,,,tip ,get the smallest inverter that will run the frig only ,sine wave ofcorse ,
Out remote ranching we learned to live without a frig ,, I have one in the cabin ,we never use it ,haven’t opened it in at least five years ,,guess we can call it a science experiment ? Ha Ha,,
With a few exceptions a frig is not necessary to live well ,you just need to think out of the box , and get a good chest cooler ,and. change some of your habits ,,
We do have a small chest freezer (5cf) run on a inverter ,it gets some use ,handy but if we didn’t have it things would be fine , we had a 21cf but used it so little it was taken out to the shed and used to store horse gain ,,, not the best idea ,mice eat the rubber seal and get in ,,also have a upright 22cf worked fine but it to want out back ten years ago , now got me to thinking what’s in the frig????????should I take it outside to open it????or just keep wondering???
Tea and chocolate
Oldhomesteader,
Hmmmm, so even with the inherent losses involved with DC-AC conversion, you had less power consumption with AC? I don’t doubt your word, but my limited experience is different.
I agree on the right sized inverter. I initially purchased one, much larger than I needed. One of several, minor mistakes I’ve made along the way. In a shtf, I plan to focus all my solar/wind power to run my chest freezer. I can always make ice to help with food preservation in the summer. In the winter, just use nature’s fridge.
I would think, folks would learn to cook only what they will eat, and eat all they cook. As you know, chest freezer/refrigerators are far more efficient than uprights. The cold air doesn’t “fall out” every time ya open the door. They are not user friendly. In spite of the baskets and shelves, everything tends to end up on the bottom.
I’m sure a higher elevation and more northern latitude makes a huge difference. I appreciate your posts and wisdom. Please keep them comin.
PlainsMedic,,,, if you do a cost comparison on 12v dc V 120 v ac to set up ,i found the 120v ac the winner ,and the ammonia frig will suffer in hot weather ,i used one for cow meds, and had problems ,, the cost of loss of vaccines more than offset any difference in the long run ,,, i have eleven inverters all have a specific use , 220 v. 5k for well , 120/220 4k for special need , 120v 3k day for cabin ,120v 1.2 k for night lights and deep cooling freezer ,all can run off one battery bank ,all told cost me less than one of the high price inverters
All are sine wave ,got them from THE INVERTER STORE. ,, the work horse of the lot is the 12 hundred w ,it even has a transfer switch. Cost 160dollars ,you don’t have to go to the high dollar units to have a good system ,,
Over time one learns what works and what doesn’t
Not putting downs 12v dc. Just think there is some thing better ,
Tea and chocolate
Oldhomesteader,
Interesting approach, many different inverters for specific loads. Ya see, I had not considered that. It makes sense to only run as much inverter as ya need.
Question for ya; You mention sine wave inverters. Are they modified sine wave or pure sine wave. I assume you mean pure sine wave. It is my understanding, for basic applications such as running an electric motor, modified sine wave will work just fine. Pure sine wave is necessary for electronics; computers, radios, amplifiers, etc. I do know that the modified sine wave inverters are significantly cheaper.
Interesting approach with the many inverters. I’ll have to think on that a while. Thanks Oldhomesteader.
PlainsMedic,,,,,when I first started the off grid journey years ago we had to make our own inverters ,motor drive ,about 40% efficient ,with lots of tinkering,,,,things are so easy now ,,pure sine wave is the only way to go ,modified or square wave will work but the efficiency loss in some things can be very high ,motors will run hot with less power out put ,and not last as long ,electronics most often will buzz at best or die a early death,
In a past life I had a undershot water wheel ,used a chev truck alt,12v dc to a battery to a inverter 220v ac to battery charger 12 v dc to storage batteries ,to inverter 120v ac to cabin ,,all that because of loss from long run of wire 1400ft ,
Ended up with a 50percent loss but was able to have power ,in spite of long run ,
Oldhomesteader,
Thanks for your input on this. Many times the real life application of electrical theory, falls short of what is expected.
Wow, a water wheel. I’ll bet that was challenging and fun. I’d love to play with hydro-electric. They have really nice stuff for hydro now. I just am not in the right spot to try it.
I have been fortunate and found some #4 solid copper wire. As ya know, dc takes big wire to go very far. This old wire was salvaged from old oil production applications. I’d hate to pay new price for copper wire.
I guess that’s why Tesla won out over Edison, in the beginning. My limited experience with dc products has been quite good. Every situation calls for a unique solution.
What type of physical connector do you use to attach all those inverters to one battery bank? That could be a wiring challenge.
84% is good!
Crow bait,
Sounds like you’ve really got it together. I’m impressed. My only point, consider the totality of what you want to accomplish. Think it thru and consider all options. For some things, water supply for example, a different approach would/could/might be better. I went with 12vdc deep well pump, low pressure and low volume, less than 2 gpm. I can use gravity to provide pressure into the house.
This little pump only requires 2 100watt panels and comes on when there is enough sun and shuts down when there isn’t. Very simple, with the option of float valves, etc. to make it even more self contained.
In the end, for my situation, the dc pump was a better way to go than 220 inverter, and lots more panels and batteries. Same thing with refrigeration, dc appliances work just as well as ac. There are drawbacks too. The really efficient dc fridge/freezer units are chest type. Not as user friendly.
I’m really impressed with your system(s). I just wish I had understood all the various options available, from the start. More than one way, to skin a cat and all that jazz.
P-medic…….
My experience with wells is somewhat limited. I assumed, and you probably know what that does, that your well was fairly deep. Apparently you are lucky enough to have water close to the surface. “Close” as in you don’t need $30K worth of stuff to get a drink. This is good.
As long as you understand how your system works and what to do and what not to do to it, you are good to go. The drawing Ken has at the top of this article is exactly how I started.
I have a travel trailer with some “12V” appliances in it. The fridge uses an ammonia refrigerant. Meaning the DC power is used to heat the ammonia to generate cooling. The power required is something in the 16 Ampere range. IMHO, not very efficient. I currently have a couple of Peltier junction devices I have been tinkering with to cool a custom made ‘cold box’. It is mostly sheet metal lined, insulated with closed cell foam, and they only draw 4 amperes each. So far, the ‘cold box’ is staying at 46 degrees using one 100 Watt PV panel. I found out that if I run the ‘cold box’ at 5 min. on 10 min. off (33% duty cycle) it does quite well, as long as you don’t open the door to many times. Next step is to find a bar-height fridge and mount the Peltier Junctions in it.
Since you have already ‘skinned the well cat’, I know who to ask questions when I get to that point.
Crowbait,
Yes, wells,pumps,submersible pumps, jet pumps, diaphragm pumps, fittings, piping,etc. One of the very few things I’m knowledgeable about. Glad to help if I can. I wish I had your knowledge and experience with solar. I’m just a diy hack. Trying to get by the cheapest and easiest way.
So ya know, my well is 245′ deep. Water level is typically around 165-175. It varies a little, more than it should actually. Mother Nature will do as she sees fit. They have made dramatic improvements with dc pumps over the recent years. Might be worth a look. I have Aquatec though there are several others with excellent reviews.
I read quite a bit about peltier units, awhile back. I’ve never actually played with any. Please update on your success or lack there of. An interesting topic, at least to me.
– Plainsmedic,
Search your computer for ‘220 inverter’. You can find a 5KW 12V/220V Pure sine wave inverter for around $450- 500. They are out there, you just have to invest some time and effort to find them.
– Papa S.
Excellent information, even I could understand. Thank you!
I do have a small (5W) solar panel connected directly to my 2 x 105 amp marine battery bank. What that does, is it allows me to overcharge the batteries a little bit, for a little while and clean/boil any sulfation off of the plates in them. The batteries will last a lot longer if you do this occasionally.
I could use a larger panel, but this small one allows me to not have to watch them like a hawk so as not to destroy a battery. Once this is complete, I will top the batteries off with Distilled Water and expect good service for at least another year. They do make plug-in chargers that will do this, even (if you spend enough money) automatically. I can do it manually, so I don’t care to spend the money. It’s an exception to the rule about needing a charge controller. This will put them at 18V for a while; you still have to keep an eye on them. When you get a boil going, just a day or two is enough. I do end up with healthier, longer lasting batteries.
– Papa S.
If you decide to go with a 12v battery bank, you can use the wide variety of equipment designed for auto/RV/boat etc.
For instance, a modern 12v car radio can provide plenty of volume in a home setup! Many LED lights available.
Be sure to fuse circuits appropriately and keep an eye on bank voltage, since this equipment will continue to operate even when the bank really should be recharged. (An AC inverter will turn itself off under those conditions)
And yes, a 12v system will require heavier wires than a 24v system or 48v system.
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