System Design / Brainstorming

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System Design / Brainstorming

Post by Wadsworth » Sun Sep 09, 2018 2:12 pm

I'm new to the board and brainstorming a new PV system. It will be built in stages, so I'm interested in ideas for optimization. I have 20 acres north of Houston TX where I recently built a 50'x60' metal storage barn. There is currently nothing else on the property but woods, no grid tie etc.. There is a possibility that my family will build a home there in the future, but if it happens at all, it is at least several years out.
I would like the system to satisfy the following:
- Immediately, power my barn with off grid ~5kw PV
- If possible, be able to use eight flooded Lead Acid Deep Cycle batteries I currently own (12v 100AH each)
- 240 / 120v capabilities (will run lights, equipment, fridge, and well water pump)
- Scalable to 15kw PV when/if we build the house
- Able to grid tie when/if house is built
- Future tie into backup generator

If we ever build the home, it will be about 400' from the barn. The grid tie location would probably be at the house, but the PV panels will be on the barn. So I have to keep this in consideration when it comes to running wires back and forth.

My goal is not necessarily to make money on this project, but to rely on solar for now, and then be able to use any equipment that I purchased in a future grid tie situation.

Thanks in advance.

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Re: System Design / Brainstorming

Post by petertearai » Mon Sep 10, 2018 7:16 pm

If you are considering grid .... then i would go grid straight away . Take grid to barn . Make that your main power position , then if you go grid tied all equipment will be set up in a one hit coherent way ,
2220 pv. fm80. 12 times 2 volt exc shoto lead carbon 450 AH 24 volts. victron battery monitor. outback fxr 2000 watt inverter

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Re: System Design / Brainstorming

Post by jbakker » Tue Sep 11, 2018 4:15 am

Bring the grid to the Barn. Unless the cost is to much to bring the grid the extra 400 feet.
All depends on how you want the wires ran to the barn? Poles or in the ground?
Or you can put the power system in the house but then you have to get the PV voltage to the house.

Definatly go with a 48 volt system. I would think about the 12 volt lead acid batteries and go with AGM or Lithium if you can afford it.

Outback Radian systems would do waht you want for the inverter side of things. You can also go with the outback PV charge controlers as well, and then OPTICS RE wourks well. I how ever like the Midnite PV charge controlers, much better unit.

There are lot smarter people then me out there who will comment as well.

Good luck in planning and choosing your system.

Let us know how it goes for you.

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Re: System Design / Brainstorming

Post by Wadsworth » Tue Sep 11, 2018 7:33 am

Yes, 48V or higher system. And I plan on running all wires underground (to the extent that it is financially feasible). The current grid utility pole is about 400 feet from where the house would go, but about 750 feet from the barn. So if I run grid tie straight to the barn, I would have to run 750' and make that the main connection, plus run a separate trench of around 400' to the house location.

As for systems, are more people now going with individual power optimizers/conditioners at each PV panel with high DC combined voltages to inverters, or is it still best to use conventional 48v type DC system? I have planned and built the barn exposure to have a nice tilted roof facing directly south with nearly no tree shading. So the PV panel exposure will be relatively uniform (beyond dust buildup etc.)..

See sketch of barn / house site plan layout:


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Re: System Design / Brainstorming

Post by gtarolli » Wed Sep 12, 2018 9:38 am

Assuming you want power in the barn after you build a house, there has to be a set of wires between the house and barn, either bringing the AC from one to the other, or the PV DC output from the barn to the house. If you put a conduit in the ground that can support either, then you can always move things. It is nice having the system near the house so you can physically check on the components, but you don't want the batteries too close. You can start with something like Radian and charge controllers and batteries in the barn, you can temp run AC to the house site thru the conduit (and CAT-5 thru another!), and then move the system perhaps to a shed or garage by the house on the side closest to the barn if you decide to hook to the grid at the house. And then pull out the AC wire and replace with DC wire, or just use the AC wire if it is electrically OK. You should check on the feasibility of running DC 400' and what size wire is needed and if you can use AC wire. If you can or can size it so that you can, then you don't have to pull the wire and replace it no matter which way you go.

My point is put in a few conduits between the buildings to allow AC or DC, and ethernet (CAT-5) to be run in either direction, and then you have maximum flexibility and can make the final decision later. If you can safely and efficiently run DC 400' then I suspect the best solution will be grid tie at the house, Radian and other components incl. batteries in a shed or closet very near the house, AC running to the barn and DC running back to the Radian.

I just thought of another issue, if you want the house to have power when the grid goes down, then it needs its own connection to the Radian. And are you going to sell to the grid? Assuming you want to do one of these you want the grid tie connection at the Radian. If the Radian is in the barn and you want battery backup at the house then you need an AC wire from the Radian to house. I recommend drawing pictures of each option you consider. I think the best will end being grid-tie as I mentioned, grid to house, Radian etc at house, DC wire the barn where the PV array is, along with AC wire for power and optionally CAT-5 if you want Internet in the barn (why not?).

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