Introduction: Solar Powering My Home!

My home has been solar powered since June 2013 and the power system has proven its reliability. I'm a proud owner of an OFF GRID solar power system. I decided to publish this instructable to let fellow DIYers know the basics to design and install a system such as mine. Dont expect an exact copy of my system if you decide to go this route. You need to know your home layout, load demand, budget constraints and future power requirements.

During this instructable I will use basic electrical terminlogy.

Notes to remember in this instructable:

1. My country does not permit grid tie. I cannot provide technical help on grid tie questions.

2. The entire design and installation I performed myself. In your case you will either need to be competent in electrical installations or hire an experienced electrical professional to do it.

3. I have fulfilled code (NFPA 70, TTS-171 Part 1) and power utility requirements.

4. Owning a power harvesting system means you are responsible for it. You can't expect to always call someone should there be issues during operation. Take control!

5. This is technical only instructable. I shall not answer financial questions.

Now let's continue on how I implemented my off grid power system. Remember when it comes to solar, the BIGGER the BETTER!

Step 1: Calculations!

Cables:

Sizing of cables (AC and DC) is very important to have as low a voltage drop as possible. For my home I used 2% maximum voltage drop from any supply Breaker to the furthest load. You can use a more tighter requirement and its no problem; your cables will have to be sized larger. The attached chart is an example I used however remember PVC insulated cables dont carry as high an amperage as XLPE. Also there are other types of insulators and temperature ratings for them all. Consult your cables' datasheets or simply use the worst case scenario charts. Also stick with copper conductors please.

For simplicity I refer to the AC ampacity chart to indicate what wire sizes to use. Please note that DC ampacity for the same cable is higher due to the fact there is no SKIN EFFECT for DC. Take for example the wiring in cars. For the headlamps, alternator, starter etc. notice the cross sectional area difference for the equivalent amperage on an AC system. Using the AC chart for DC cable sizing means you will have a lower voltage drop which is good.

A basic guide I have used well over the years is 5amp per mmsq of copper cable. My cable runs are less than 100ft and that estimate has worked out great. For example if I needed to pass 50amp dc then I would use a 10mmsq copper conductor. For longer runs, the cable chart would be recommended.


Breakers:

Molded case breakers are typically permitted to run a maximum continuous current of 80% their nameplate rating (unless its a 100% rated Breaker). Breakers for DC are differently rated than AC Breakers. Should you wish to use an AC rated Breaker for DC service, the general rule is the maximum DC voltage is 1/5th the AC voltage rating on the Breaker. Exceeding that limit means the breaker will not properly extinguish the arc during opening operations. Always check the cutsheet for the Breakers you select to verify operation at DC. Also dont oversize your Breakers else you defeat your protection (eg. 15A breaker for a 2 amp load).


Solar Panels:

I used a rule of 4 hours usable sunlight to size my panels. The energy demand for a 24 hour period needs to be determined. You can either use the utility energy meter and average your usage during the week or use standalone meter. The power utility meter is the easiest method.

For example if you use 1000Watt-hours of energy for a 24 hour period, then the panels you need will be (1000/4 =) 250Watt of panels.

You can assume 6 hours or more of usable sunlight to carry your cost down but I prefer more power to provide for my needs.


Batteries:

The Watt-hour demand for a 24 hour period is the minimum size the battery bank should be. Battery watt hour is volts x amp-hours. A larger battery bank means better voltage regulation at the input terminals of your DC loads eg. inverters, DC lighting, DC Fans etc.

Step 2: Installing the Solar Panels.

I installed my panels on the roof of my home. There are OEM mounting kits for this or you can make your own with metal or rigid PVC. I actually did a mixture of both. I have a total of 8 panels, each rated at 225Watt.

The optimum angle for installation varies around the world. For me it's 15degree from horizontal so mounting directly on the roof worked out great for me. I have panels facing the east and west to capture the sun from dawn to dusk.

It is a good idea to install the panels where you can access them for cleaning but for the most part they are maintenance free and have long service life (20+ years). An interesting side effect of the panels on my roof is the shade they provided actually made the house a bit cooler. Mind you I have a single level, 3 bedroom home (not big but its my home).

https://www.instructables.com/id/Maintenance-cleani...

If you have alot of shade from trees then you need to address this first or have an alternate location to harvest sunlight from dawn till dusk.

I made a penetration in my roof's sheeting and ran the power cable through it. I put strain relief and lots of silicone on the penetration. The panels are actually installed over that penetration so water ingress is not a problem.

If you wish, you can install a sun tracker for maximum harvesting. These are expensive and should not be installed on roofs. Why? Strong enough wind blows and your roof will suffer if it hasn't already from the weight of the tracker and panels. Trackers also require maintenance so these pointers you need to keep in mind.

Step 3: The Solar Charge Controller.

I originally had a morningstar MPPT 60Amp controller but it failed after a month in service. I just threw it in the garbage, angrily, warranty be damned. I have in service since mid 2013, an Outback MPPT FM80. I firmly trust this controller and will recommend it anyday. I also recommend MPPT type rather than PWM to get more energy into the battery bank.

You can have multiple charge controllers into the same battery bank. Each controller will need to have its own set of solar panels.

The outback FM80 can accept up to 150VDC so I wired 4 of my panels in series. I have a parallel connection of two of those strings and this is fed into the outback. My outback is currently maxed in this configuration. Always know the maximum open circuit voltage for your panels to know how many can be wired in series to your mppt charge controller. Never exceed the maximum input voltage to the mppt (you know what will happen!).

Using an MPPT controller means you can use smaller cables to deliver the power into the controller.

It is important to have a Breaker before the input to the outback for protection and maintenance.

Here is a free piece of timeless advice; the breaker to the battery bank needs to be turned off last and also it has the be the first one to turn on. Why? If solar power is present on the input without battery control power, your expensive charge controller will go bye bye! Trust me I know!

Step 4: The Battery Bank.

I used lithium iron phosphate (Lifepo4) to store the harvested energy. It's a 25.6v 160amp hour bank.

The details on this bank is covered in my instructable below:
https://m.instructables.com/id/Lifepo4-solar-storag...

Generally the higher the battery bank voltage the better once you can get a compatible inverter.

It's critical to have short circuit protection for each battery or battery string. A circuit breaker is a good means of doing this. Also for maintenance or upgrades, throwing a breaker off will facilitate this. Don't ever wire up a battery bank without protection!

LifePO4 has no toxic components, offers long service life (more than 2000 cycles@100% DOD according to the manufacturer), does not vent gasses, offers 4 times the power density at a third the volume compared to lead acid. Its perfect for installation in living areas. I personally overcharged a LifePO4 cell for 5 weeks and all that came out was brown electrolyte. No burning, gassing, irritating smell. I truly love this battery chemistry!


Also people, please don't use SLI batteries. These are shallow cycle and used only to start engines. You Want deep cycle batteries. Lifepo4 batteries are actually suited for both uses but it's up to you to decide what Your budget can provide. Lead acids are cheaper up front but don't have good lifespan, safety, environmental impact or discharge characteristics as Lifepo4.

Step 5: DC Wiring and Breakers.

I used flexible cables to route power to and from my battery bank. These type of cables are easily obtained from electronic stores or even car audio shops. Again the larger the cable to better however don't go so large that the wire cannot fit in a breaker or connecting lugs.

The breakers I used are DIN rail mounted type. These are quite low cost from Amazon. All my DC breakers are single pole. The negative of the DC power system is tied to a shared connection point. Only the positive is protected with the breakers.

Step 6: The Inverter.

Most household appliances and loads use AC voltage Whether it's 120v or 240v. I strongly recommend using only pure sine wave inverters to power these devices especially those with motors.

Some 120v inverters such as the transformer-less type are more efficient but do not allow the neutral output to be connected to the neutral of your utility! The neutral output when measured to ground will always have a voltage difference. The utility neutral will be tied to ground and reads 0v between ground.

Basically when using 120v inverters with non zero voltage neutral (relative to ground) you will need to use a two pole transfer switch. One pole for live, the other for neutral. If you don't have a utility supply to your home then you obviously won't need a transfer switch.

Do not be tempted (transformer less inverters) to connect the neutral to the ground connection. The inverter will fail because of this (yes I know this first hand).

If you wish to avoid all that headache just buy the transformer type inverter and these would have a neutral output of zero volts. Read the manual for your inverter carefully!

Step 7: AC Panelboard and Transfer Switch.

The output from my 120v inverter I wired to a panelboard I built complete with an automatic transfer switch. Below is the instructable I published for that project:

https://m.instructables.com/id/DIY-Circuit-breaker-...

You can purchase a panelboard complete with transfer switch if you prefer but for my needs I preferred to build it.

The computer control of the automatic transfer switch ensures the loads in my home will have power should the battery bank voltage drop too low. Below is the instructable I published for that automation project:

https://m.instructables.com/id/Creating-a-home-automation-system/


Having proper protection will keep everyone and everything safe in the event of a fault.

Here is a good piece of information. There are two ways to tie an alternate supply to your home.
1. A breaker interlock kit. This is basically a mechanical plate that prevents the main and a sub breaker from being on at the same time. This can be defeated and allow paralleling of two non sync sources! Very dangerous and I strongly recommend not using this method even though it is low cost.
2. A transfer switch physically allows only one of two sources to send power to a load. There is no possibility of paralleling here. Very safe and robust.

Step 8: Energy Efficient Loads.

Having all my lighting as LED helped greatly. I still have my standard refrigerator and washing machine. If at some future point those fail, for sure I'm gonna get me the inverter versions of those appliances for better energy savings.

All TVs in an off grid home should be LED. Even the computers should be the low wattage type even for desktops.

Most importantly is the human mindset. Use your energy sparingly. Dont assume there will always be energy available. Be wise and economize.

Step 9: Enjoying Off Grid Living and Planning for the Future!

For the most part I live off grid although I have the ability to use utility power when I need it, especially for large intermittent loads. To make life simpler and more enjoyable, I automated my entire home to handle all solar loads.

An installation like this is a long term investment and will pay off for itself. In my country electricity is very cheap so the payoff period is extremely long however I did this project as a labor of love and not really to have financial savings.

If you are nomadic and move around then this instructable may not be for you, unless you live in an RV or boat. I recently installed a small wind turbine generator to augment my harvesting capabilities. Check it out!
https://www.instructables.com/id/Installing-a-wind-turbine-to-power-my-home/


Using green energy rules!

Comments

author
DBElectric (author)2016-12-17

Good article and advice. Do you have knowledge in PLC contactor control for string sets switching battery banking for charging, fault, online and off line?

author
rigo54 (author)2016-06-09

Great!

Hi friends. We must use the sun and wind power, instead of fossil. The fossil is causing all kind of disasters, especially ozone layer. In addition, causing high temps, health conditions, respiratory illness.

I am working in a similar project, with a variance; its hybrid, sun and wind.

I live in The Caribbean and we have a lot of water and sun.

Be kind, be good, be all you can be, but never surrender.

author
Mjtrinihobby (author)rigo542016-06-09

Caribbean rules!

author
stuckindmud (author)2016-05-30

Hey, I am doing a similar build and would like to bounce some ideas off you and your experience . Send me a mail on skgoorf@gmail.com if you're keen on helping me out .

author
stuckindmud (author)2016-05-10

Another write up - more good stuff . Did you do a write up on how you sizes and designed your system ?

author
Mjtrinihobby (author)stuckindmud2016-05-10

Yup. Check my profile.

author
stuckindmud (author)2016-05-10

Sorry inverter- not system.

author
stuckindmud (author)2016-05-06

Hey great ible! Question - how do you tie your inverters to your house electrical panel - if you I use any of it at all?

author
Mjtrinihobby (author)stuckindmud2016-05-06

I made a separate panel with an automatic transfer switch. This panel accepts the power (120VAC) from my inverter and distributes to my home loads.

author
ZulkipliM (author)2016-04-25

Boleh saya tahu berapa kos bagi pemasangan panel solar dan peralatan untuk aircornd

author
RangasamyT (author)2016-04-21

This complete off grid solar energy harnessing step by step system explanation with all requisite accessorial lllustration is really encouraging , a wonderful idea. Thanks lot

author
Mjtrinihobby (author)RangasamyT2016-04-21

Thank you!

author
juntjoo (author)2015-12-29

Okay what "country" are you in already??

author
a_fixer_man (author)juntjoo2016-02-01

its in the dudes "username"

author
juntjoo (author)a_fixer_man2016-02-01

Trini... DAD?

author
RichardL81 (author)2015-12-16

Plus, if you wanted 15% more power, just add one more solar panel. That would only cost about $300 or so, way cheaper than a tracker. And, much better for high winds.

author
Mjtrinihobby (author)RichardL812015-12-18

I guess but my charge controller is already maxed out with the 8 panels I have. Also, I have them wired in 4 series with another 4 series in parallel (two parallel strings). It is not possible to have parallel strings with 5 and 4; that will result in immediate damage to my panels.

author
vrudec (author)2015-05-22

It might be interesting parallel to the collector and connect one windmill at least a small for yachts so that the bad weather we have electricity.

author
CristinaC6 (author)2015-08-20

That makes sense i guess i did t think about it that way in a large scale mine was for solar phone charger so the motors and the axial were small and practical.. Good reasoning tho

author
Grendal77 (author)CristinaC62015-10-01

a solar reflector is a possibility too and they are light. Also you can get 15% more if you cool your panels. I saw an article about a guy who did it over his solar water heater...

author
Mjtrinihobby (author)Grendal772015-10-20

excessing heat on PV panels will destroy them quickly. There is no reliable was to remove heat acquired during harvesting except air flow. Solar reflectors are never used on PV panels.

author
Mjtrinihobby (author)CristinaC62015-08-20

any question is a great question. Your suggestion has merit, sadly it can't apply to my home.

author
jiivaneshvar (author)2015-05-21

How long will your battery last? My solarmaster battery lasted only a little more than 2 years and the cost of replacement is more than the cost of power it generated. Some battery can last up to 10 years but the cost is too high, and I'm afraid I will be paying more than being connected to the grid.

author
terrefirma (author)jiivaneshvar2015-08-20

Perhaps it's about independence and not so much dollars.

author

Typically 2000 cycles at 100% DOD. That may translate to about 8 years with the way my software manages the house.

author
CristinaC6 (author)2015-08-20

I hope you dont mind one more suggestion/ question, i know from my electrical engineering background that solar panels have to be cleaned at least twice a month inorder not to drop efficiency, how do you go about that? Do you get up the roof and clean them/wioe the dust out ? How about snow if it snows where you are?

You can cheapily and easily make a cleaning "robot arm" kinda thing attached to the panels that are poeered by the panels to clean them .. No?

author
Mjtrinihobby (author)CristinaC62015-08-20

good questions my dear! I actually clean mine once every 3 months. They actually don't get dirty much except for the occasional bird droppings. Here is the instructable I published for cleaning them.

https://www.instructables.com/id/Maintenance-cleaning-of-photovoltaic-panels/

I live in a hot Caribbean island so I have zero snow, only heat and more heat. As far as efficiency is concerned, even with a thin film of grime on my panels, I still get the same output from them. Heat is the real thief of efficiency for photovoltaics.

You can ask me any questions here or you can private message me. You are a fellow electrical engineer? Nice.

author
CristinaC6 (author)2015-08-19

Have you ever considered a dual axis for your pv system for more efficiency? Ive made that project before for school and you get about 15+ extra efficiency to the whole system

author
Peterb11115 (author)2015-08-10

Bravo. Thanks for sharing.

author
Mjtrinihobby (author)Peterb111152015-08-10

Thanks!

author
leonearl50 (author)2015-07-26

Ty. Great Instructable. Directions are clear and show your hands on experience. I am looking forward to following your lead.

author
Takue (author)leonearl502015-07-28

Pretty much agree with you @leonearl50

author
Mjtrinihobby (author)leonearl502015-07-27

Thank you kindly.

author
ClaudiuI (author)2015-06-26

Good.instructions. I didn't find anywhere, is there a way to switch from the solar system to electric operators without going through 0 power?

author
Mjtrinihobby (author)ClaudiuI2015-06-26

The automatic transfer switch in my diy panelboard does that for me. Bumpless transfer of power. No different to a desktop ups. My house power system was originally a huge ups which I added a solar charge controller plus my own custom home automation system.

author
rramos1 (author)2015-06-07

This is very informative and very useful in my country. Thank you very much to the author. More power to you Sir.

author
Mjtrinihobby (author)rramos12015-06-07

Hey thanks!

author
voningraham (author)2015-06-01

thank you ,very good info...

author
Mjtrinihobby (author)voningraham2015-06-01

Thanks!

author
mist42nz (author)2015-05-22

The batteries act as a load and current/voltage sink. PV panels are constant current, so will lift the voltage (to the maximum panel rating) to try and keep the current flowing at the preferred rate (or technically the voltage drops off like capacitor discharging, as the current flow increases, until it stabilizes)..
Without the batteries to act as ballast the Morningstar won't pass on the incoming current, and the PV panels will just try harder to shove it through, until they force a short circuit/overload in the unit.
PV panels are the opposite to batteries. you can short your PV panels and the voltage will drop away to near nothing to keep the current at the right level.
Batteries try to keep the voltage at the right level and will shovel through more and more current to try and keep the P.D. up, a short in batteries will create several thousands of amps ( I accidentally vapourised the metal end of my battery connectors when I knocked one with my knee)

author
Mjtrinihobby (author)mist42nz2015-05-23

Hey you wrote the world of non sense. You don't even have a single instructable published which mean you just talk. Keep your madness to another forum. The community here at instructables is only about real world facts.

author
deba168 (author)2015-05-22

Nice Instructable.
Your design is very neat :)
Its really helpful for all.

author
Mjtrinihobby (author)deba1682015-05-23

Thanks for the appreciation.

author
gatecrafter2 (author)2015-05-21

good to have this simple steps.

author
roger.trant (author)2015-05-19

I have been wanting solar power for a long time! Someone give me a $ number I will be needing! I want someone to come an install a solar power with grid tie in! I have a house that is 1400 square ft!

author
kdkerps (author)roger.trant2015-05-20

I pay 110 a month in lease of 35 250 W panels. down was 500. took almost a year. I'm still tied to the grid as I use a lot of juice. all in all, I'm saving $300+ a month in electrical bills. but be careful, they will try to undersize your inverters or clip your power.

author
tp.pa.12 (author)2015-05-20

Here is the best way to wire your battery bank in parallel for equal charging & discharging rates.

Best Way To Run Parallel.jpg
author
daemoncan (author)2015-05-20

Great Instructable.

I thought I was the only one who learned from his mistakes :) It's a great way to acquire knowledge (but can be expensive). I experienced both the charge controller "POP" when connecting the batteries after the panels, as well as the inverter "CRACKLE" after trying to power the AC input of a small trailer (neutral-to-ground bonding). MOSFET's have the most awesome smell when you release the "magic smoke".

author
Mjtrinihobby (author)daemoncan2015-05-20

HAHAH! good one but experience like that is the sometimes the best teacher.

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