Getting ready to buy my setup

[justenglabs]

Good day! We are off grid in Western Maine and looking to purchase panels, batteries and inverters for our off-grid home we will start to build in the fall. Looking to get the purchase completed before pricing gets to nuts. We also just purchased additional property that will be an off-grid spot for a camper.

For the house, I will be building a garage with a large roof with will be 10-15 degrees off of south. I am thinking that I will install 30 panels on that roof. I am looking at either JA Solar or Aptos 450 Watt bifacial panels. I understand we could get more bang for power with ground mounting but I would rather consolidate tractor barn and the panels into one. And our ground is nothing but a boulder field. Will two EG4 18kPV Inverters paired with these my panel cant be adequate? Are there other inverters I should be considering? What should I shoot for with respect to volume of batteries? We will be living there full time and planning on a 1500 sq ft home. Will use propane for appliances where we can. We will have a generator backup. The barn will be 100 yards from the house. How do I handle that? Inverters and batteries in the barn on in the house?

TIA

 

[robbob2112]

Specific answers to your questions - then the standard stuff

300ft - you just use a MPPT or AIO and series up your panels so they have the max allowable voltage -- This depends on the historic lowest temperature and the panels you choose. Basically you are looking for what is called an isolated MPPT if you are doing discreet parts... the ones built into the EG4 are higher voltage but not entirely isolated... technical details for HF AIO you can dig into...

For the audit -- lookup average load for things like the heat pump if you install one or other heavy loads and figure what you use now -- you can get a decent ballpark estimate.

One reason to do two AOI like the EG4 is redundancy - if one fails you still have power.

And you might want to investigate the Schneider XW Pro inverters - they are end of life and discontinued and are being sold at a steep discount currently... Until a few months ago it was a $3000 inverter and it now goes for $1200ish -- it is built like a tank and can handle double the rated loads for a period of minutes...

Also, ground mounted panels in winter are way way better if you have snow -- you can manually clear them if needed and if you do the mounts right you can tilt them to match the sun angle.... which means you get good production even in winter... On the roof you are limited to the pitch of the roof and if the snow piles up you might be days without production and running from generator to charge your battery bank.

Use the hazard tool listed below to find the wind and snow load at your location.


Standard Blurb

Don't spend any money, until you have planned out the entire system. An eraser is cheap, but returns can be costly.

Planning

1. Energy Audit - what do you have to power?
2. Size the inverter for your maximum instantaneous demand (including surges).
3. Size the battery for how long you want power, when the sun isn't shining.
4. Size the PV to cover the loads and recharge the battery, when the sun is shining for your area - most in the US use 4hrs or 5 hours a day of sun
5. Trying to use old equipment you already have usually costs more in design compromises than just selling it and doing it right.
6. READ the site - every question you have has probably already been asked - if you have special circumstance - start your own thread.

Design planning

1. Use drawio to design your system if the instructions didn't include a design you can use. https://www.drawio.com/
2. Tilt angle - your latitude is your year round tilt angle - in my case the 5/12 roof pitch is around 22 degrees so is a summer time tilt. My winter tilt is somewhere around 42 degrees - but they would act like a sail and tear my roof off if tilted that far.
3. Don't forget temperature when calculating panel voltage - my 335w panels mounted at 42degrees on the side of the house deliver 408w in winter at 36 degrees.... at 9 degrees it delivers 430w... The voltage increase is similar with an increase in current.

Installing

1. Use https://pvwatts.nrel.gov/pvwatts.php - put in your address and the rest to see how many hours a day of sun
2. Use this when you mount your panels to get the wind and snow loads - https://ascehazardtool.org/
3. Buy quality tool when you do - the cheap stuff is generally inferior and will make bad connections
4. Remember you are dealing with lethal current and voltage - use safety equipment
5. If you are unsure about anything ASK - there are many experts in different fields willing to answer your questions