diy solar

diy solar

Starting from scratch

Daveyclimber

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May 2, 2021
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I am building a modest cabin and a decent sized shop in northwestern Montana. The build site is completely off grid with no near future intentions of having grid access though we are located next to a state highway. I have little idea on where to start on figuring out power needs. Outside of small household appliances and shop equipment we will be starting fresh. All major appliances were left at our old home. All these usage calculators seem to have widely different power consumption rates, many appliances are used infrequently or very short term. We have been living in a travel trailer for two years so we do know how to conserve everything but we want to live mostly normal again and have most of the convenience of prior on grid life.

Our cabin will be 2 bedroom, 1 bath and about 1800 sq feet. Looking to build a 36x40 shop. I have a considerable amount of tooling and shop equipment from my prior living arrangement and use the shop to fix up and sell vehicles and medium sized equipment. I have electric welders but will most likely sell the majority of my heavy consumption equipment and buy an engine driven welder which would power things like my plasma cutter. Many of my smaller handheld power tools have been supplemented or replaced by gas or battery powered tools. I am a forestry contractor by trade and am used to doing much with little.

We will be drilling a well and also building a large bird enclosure with a tackroom and loafing shed for horses. Our lot leaves alot to be desired in the way of constant sunshine. Our property backs up to usfs land on the east side of use and we don't get an appreciable amount of direct sun until after 11am. I have two small reasonable areas for solar arrays, one appears to be best suited facing south and the other to the west. I am also expecting to have a small diesel generator to augment power production and will have to lean on it heavily during the winter months. I am going to have to do much of the building and construction myself due to the lack of available contractors in the area and inflated pricing of practically everything needed to construct a home these days.

Input and ideas would be greatly appreciated in determining power needs and ideal componants selection and placement.
 
Lack of solar exposure can be made up with a larger deployment of panels. Is the lack of exposure due to terrain or trees?
 
The place to start generally goes like this. Step into the office and pull up a chair. :)

1) Measure your daily power consumption. For most, this is in Killowatt hours, not just dc amps.

2) Find your solar-insolation hours, typically winter. These aren't just sunrise to sunset hours! Ie, weak early morning and late afternoon hours are thrown-away as part of the calculations.

3) Now you pick the appropriate battery capacity to support you for at LEAST 1 day. Preferably more. Most choose at least 2 or 3 days, but you have a genny to help you decide how many "days of autonomy" you need.

4) Solar insolation hours will determine how much solar panel you need to get those batteries charged.

In the old days, steps 3 and 4 were very inter-related due to the usual slow-charging needs of FLA or other lead-acid batteries. My recommendation here for solar especially is LiFeP04 lithium, as it can be recharged much faster than lead, and for a home living environment, much safer than other lithium types.

Doing this in the wrong order is what we call the wrong "ready, fire, aim" method. Costly.

So, although you've stated you are completely off grid, just know that solar-living - as a recurring expense lifestyle - is generally about 10 times more expensive than on-grid. It isn't just the initial investment, but the cost of replacing the batteries down the road. Hence even more important to get it right - or at least in the ballpark first.

Of course there are those that are willing to cut these battery costs by getting discards, second-life, or other freebies - but to get the most from that means you need to recognize what is truly trash (and safe or unsafe) and what is a salvageable value. The value proposition, and knowledge to make that judgement is wide in scope.

If one is learning as they go, and either under-or-over estimates their true needs, then this cost rises with either surplus capacity, or needing to start over again.

With that out of the way, will you be doing the work? Or would it be wiser to have a professional installer and solar company take care of this for you?

DIY ?
Before going online or elsewhere to find solar goodies, you need to invest in measuring equipment first so that you can accomplish step #1.

The simplest is to get a "Kill-A-Watt" meter that plugs in between your appliances and the wall. (or generator and inverter in your case)

Measure how much power you use per day with it. No, this is not lab equipment accurate, but it will get you in the ballpark, and help realize what might be possible, or what is out of the question, and needs a power-saving replacement.

Basically, how much power are you using daily? Live normally, and measure and record those values.

Once you do that you can move on down the 4 steps.

Option: You can have fun and dart-board things. See what works and what doesn't. The genny will take care of the rest if you under-estimate and have to double system capacity and start over. Most people don't want to do this, but it can be fun if you have the means.
 
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The place to start generally goes like this. Step into the office and pull up a chair. :)

1) Measure your daily power consumption. For most, this is in Killowatt hours, not just dc amps.

2) Find your solar-insolation hours, typically winter. These aren't just sunrise to sunset hours! Ie, weak early morning and late afternoon hours are thrown-away as part of the calculations.

3) Now you pick the appropriate battery capacity to support you for at LEAST 1 day. Preferably more. Most choose at least 2 or 3 days, but you have a genny to help you decide how many "days of autonomy" you need.

4) Solar insolation hours will determine how much solar panel you need to get those batteries charged.

In the old days, steps 3 and 4 were very inter-related due to the usual slow-charging needs of FLA or other lead-acid batteries. My recommendation here for solar especially is LiFeP04 lithium, as it can be recharged much faster than lead, and for a home living environment, much safer than other lithium types.

Doing this in the wrong order is what we call the wrong "ready, fire, aim" method. Costly.

So, although you've stated you are completely off grid, just know that solar-living - as a recurring expense lifestyle - is generally about 10 times more expensive than on-grid. It isn't just the initial investment, but the cost of replacing the batteries down the road. Hence even more important to get it right - or at least in the ballpark first.

Of course there are those that are willing to cut these battery costs by getting discards, second-life, or other freebies - but to get the most from that means you need to recognize what is truly trash (and safe or unsafe) and what is a salvageable value. The value proposition, and knowledge to make that judgement is wide in scope.

If one is learning as they go, and either under-or-over estimates their true needs, then this cost rises with either surplus capacity, or needing to start over again.

With that out of the way, will you be doing the work? Or would it be wiser to have a professional installer and solar company take care of this for you?

DIY ?
Before going online or elsewhere to find solar goodies, you need to invest in measuring equipment first so that you can accomplish step #1.

The simplest is to get a "Kill-A-Watt" meter that plugs in between your appliances and the wall. (or generator and inverter in your case)

Measure how much power you use per day with it. No, this is not lab equipment accurate, but it will get you in the ballpark, and help realize what might be possible, or what is out of the question, and needs a power-saving replacement.

Basically, how much power are you using daily? Live normally, and measure and record those values.

Once you do that you can move on down the 4 steps.

Option: You can have fun and dart-board things. See what works and what doesn't. The genny will take care of the rest if you under-estimate and have to double system capacity and start over. Most people don't want to do this, but it can be fun if you have the means.
Oh, I know what I'm getting into. LOL, this wasn't my first option, trust me. Be that as it may, it is a decision my wife and I are going to live with and hopefully enjoy. My main issue is figuring out my power consumption when I currently have nothing to measure. I live in a travel trailer and have done so for more than 2 years. I'm over it:censored:, not enough space and I'm tired of being separated from my belongings. I live in this thing when I'm out in the boonies working for the BLM so its time to have a home again when I'm not working.

So not living on grid or even remembering how to, what is going to be the best way to determine power consumption without making assumptions. Generally speaking when it comes to something critical I'm a buy once cry once type of person. I fully expect $40-50k between solar, generator, inverter, batteries and such. I like deals and saving money but I really don't see much of that happening in this instance.

I have room and decent sun exposure available for 2 6 panel pole mount arrays, maybe 3 but the 3rd wouldn't be in the best sunshine even if I cut down a couple of trees. Most of the offending trees are on usfs land and some on county land and of course the trees I own that limit sunlight are the largest and nicest trees so they won't be going anywhere. Also thinking split phase is the best option for us, 240v well pump and that would also allow a 240v receptacle in the shop for a limited use item. I would likely sell most of my 240v power tools to fund an engine driven welder which would power 240v items i cant do without.

So again, how would I attempt to measure power consumption without making assumptions. All the power consumption calculators I've seen vary widely and seem more like guessing which just makes it all the more confusing. I've done a couple in the past but again its nothing more than a guesstimate solar insolation in my location is about 2.5hrs in the winter if I remember correctly . Fairly dismal. I'm on the fence regarding battery composition. I am a forestry contractor as I can be away from home for 1-3 months. Initially I wanted to go with FLA but am now curious of the ramifications regarding my absence and what battery composition would be best in that regard.
 
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Bigger bang for the buck with LiFePO4. But I went that route because I could get a ton of Ah for a lot less weight. For a house, weight isn't a concern. No maintenance with LiFePO4 and the expected life is up to a decade if you treat them half decent.

With regard to your power consumption estimate, the best you can do is use the ratings provided by the manufacturers. Some motors have huge startup draws that have to be taken into account.
 
I make no secret here that I'm a fan of Sunny Island.
Look for DC Solar trailers (eBay, Craigslist) which have two of them, as a possible starting point. Some come with a diesel generator.
Consider 3 inverters for 3-phase.

Big motors are hard to start with inverters. VFD with a 3-phase motor should be very soft-start.
You can get well pumps from Grundfos which work that way.
 
Yeah I seen one of those trailers at a recent auction in Portland. It had a kubota generator. I inadvertently removed it from my watch list so I'm not sure what it went for. Too bad the generator was a 3600rpm generator. Interesting concept. Where are the Sunny Islands made. They may be good but dang what a lame name. Sounds so chinese., never considered them admittedly because of the lameness of brand name.
 
Sunny Island and Sunny Boy are from SMA of Germany. But assembled in USA or Canada, for the US models.
I think they're the best inverters ever made, but software may be a bit behind the times (which is fine with me.)
They make a robust on/off grid system with good surge to start motors.
They have very good management of lead-acid batteries (like the forklift ones on those trailers.)
If used with lithium, those need a compatible BMS which will request charge current. Surge is limited to what he battery can deliver.

You would only run the generator on rare occasions, at full load while recharging batteries then shut if off.

The trailer could be a starter system with its 2500W of DC coupled PV.
Add on with up to 24kW of AC coupled Sunny Boys, using < 600 Voc strings of PV.
(or if you add a 3rd Sunny Island for 3-phase, up to 36kW)
I prefer the older transformer-type Sunny Boys instead of transformerless.

There are two state of charge settings you can use to connect/shed loads, also generator auto-start.

 
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