Off-grid solar for new development (Campground+Two Yurts), thanks for any help!

cdnorth

New Member
I think the panel array will be the issue. I doubt someone wants a 10kw panel array next to their campsite, but I definitely agree with the autonomy idea.
Thankfully we have some space between the main facility and our septic leach fields that would work well for solar. Close enough where people can see them if they are interested but not so close that they are right next to their site.
 

cdnorth

New Member
Maybe two MPP 6548 for the main building. That will give you 13kw of power to run everything (120v single phase) which should be plenty I think. Run this off the biggest battery array you can manage and the biggest solar array you can manage. Each unit has 2 solar charge controllers, so I would max them out (4kw each) and point each array in a slightly different direction (South East, South, South West assuming northern hemisphere). That way you start getting power early and keep getting it all day long. 16kw array should net you at least 50kw a day I would think. Supplement with a small (very quiet) generator (2-3000w). The generator can run all day, so it doesn't have to get it done all at once.

Then I would run a single 6548 for each yurt with a single 5kwh battery pack. That will run a mini split AC and all of your other needs and the 5kw should give you an hour buffer at constant use. You would hook the AC in side to the main building, so you really only need to run a single 10awg line from the main compound to the yurt. That would give you 20-30a of charging (24/7) from the main building.

Repeat the above for Yurt 2

If you can add more solar to the main building, just add PCM-60x's for each 3kw or so of array you can add. Batteries just keep adding as you can afford them. I like the EG4 batteries for simplicity, but at $1500 a pop they are expensive compare to DIY cells.
I actually really like this idea, I'll have to get a cost for running smaller wire to each site but I can't imagine that would be anything too great. So if I'm understanding correctly, you are saying to run the MPP 6548 without direct solar correct and just have it continously trickle charge the batteries essentially with a 20-30a circuit? I think the main reason I like one central facility is so we can minimize the number of different solar arrays, have only one backup generator, etc. so that could work.

Our design sun hours are apparently 6.4 so even accounting for efficiencies, we get quite high production. Northern Arizona has relatively few cloudy days, lots of sun and the fact that we will really only be running the central facility for 6 months from spring to fall should make that even higher production.

One question I had about the EG4 batteries as that's what I was leaning towards. The listed recommended amp draw is 30A (1440 Watts) and 100A maximum. Should I be concerned about drawing more than 30A and what are the downsides to doing so? Technically one MPP 6548 could draw more than 100A so would it be better to have two of them for each yurt? How many of these batteries would you recommend for the main facility given the loads outlined and assuming we are okay with running the generator on cloudy days?

Thanks again for all the help on this!
 

iamrich

Solar Addict
I actually really like this idea, I'll have to get a cost for running smaller wire to each site but I can't imagine that would be anything too great. So, if I'm understanding correctly, you are saying to run the MPP 6548 without direct solar correct and just have it continuously trickle charge the batteries essentially with a 20-30a circuit? I think the main reason I like one central facility is so we can minimize the number of different solar arrays, have only one backup generator, etc. so that could work.
Yes, basically you have a stand-alone system being fed from the main facility. 10a at 120v is 1200w, so 29kwh each day of charging. You set the MPP to limit the AC charging to 10a which is nothing for 10-12awg wire even over long distance. You could also hook up a couple of panels to the controllers if you can find a way to mount them that does not kill the aesthetics of the yurts/ camp ground.
Our design sun hours are apparently 6.4 so even accounting for efficiencies, we get quite high production. Northern Arizona has relatively few cloudy days, lots of sun and the fact that we will really only be running the central facility for 6 months from spring to fall should make that even higher production.
You will likely be producing more power than you can use during the day, so battery storage will be "sky's the limit". I would definitely set up the arrays so they are facing at least three different directions and angle them for best summer production if you are going to moth ball the facility for winter. You want the panels to start producing the second the sun is up and not stop until it is down. Since you are in Arizona, I would pay a visit to Santan Solar and see what they have. I like the 250w snail trail panels. They have gone up in price, but assuming you can haul them, $50 a piece is hard to beat. Run them 4S4P (4000w) x2 for each MPP 6548 and that would give you 16kwx6=96kwh. Heck even if you got half that you are looking at 50kwh production each day. If you need more, just add another MPP 6548 and two more arrays.
One question I had about the EG4 batteries as that's what I was leaning towards. The listed recommended amp draw is 30A (1440 Watts) and 100A maximum. Should I be concerned about drawing more than 30A and what are the downsides to doing so? Technically one MPP 6548 could draw more than 100A so would it be better to have two of them for each yurt? How many of these batteries would you recommend for the main facility given the loads outlined and assuming we are okay with running the generator on cloudy days?
Maybe the best course of action would be to just leave yourself room for more than one battery. They are stackable, especially if you put them in the cute little enclosures they sell. Keep in mind you can also pull 1200w from the main facility through the AC in, so that would give you closer to 3kwh of power to play with and you can definitely pull more than 30a from those batteries, they just don't want you to do it continuously.

For the main building I would just go as many as you can afford. I would say at least six to start.

The nice thing about this is you can add as you go, so you don't have to get it all at once. Even if you just get one MPP 6548 for the main building to start, it will power your campsite off a couple of batteries and two arrays. $1600 for the MPP6548, $1600 for the panels (32x$50), $3000 for two batteries, $500 for the wiring/racking/etc. and you are in business.
 

cdnorth

New Member
Yes, basically you have a stand-alone system being fed from the main facility. 10a at 120v is 1200w, so 29kwh each day of charging. You set the MPP to limit the AC charging to 10a which is nothing for 10-12awg wire even over long distance. You could also hook up a couple of panels to the controllers if you can find a way to mount them that does not kill the aesthetics of the yurts/ camp ground.

You will likely be producing more power than you can use during the day, so battery storage will be "sky's the limit". I would definitely set up the arrays so they are facing at least three different directions and angle them for best summer production if you are going to moth ball the facility for winter. You want the panels to start producing the second the sun is up and not stop until it is down. Since you are in Arizona, I would pay a visit to Santan Solar and see what they have. I like the 250w snail trail panels. They have gone up in price, but assuming you can haul them, $50 a piece is hard to beat. Run them 4S4P (4000w) x2 for each MPP 6548 and that would give you 16kwx6=96kwh. Heck even if you got half that you are looking at 50kwh production each day. If you need more, just add another MPP 6548 and two more arrays.

Maybe the best course of action would be to just leave yourself room for more than one battery. They are stackable, especially if you put them in the cute little enclosures they sell. Keep in mind you can also pull 1200w from the main facility through the AC in, so that would give you closer to 3kwh of power to play with and you can definitely pull more than 30a from those batteries, they just don't want you to do it continuously.

For the main building I would just go as many as you can afford. I would say at least six to start.

The nice thing about this is you can add as you go, so you don't have to get it all at once. Even if you just get one MPP 6548 for the main building to start, it will power your campsite off a couple of batteries and two arrays. $1600 for the MPP6548, $1600 for the panels (32x$50), $3000 for two batteries, $500 for the wiring/racking/etc. and you are in business.

Thanks for all the help, I thought it might be helpful to include our current site plan for the project to give a better idea of where everything is located on the property and give a little more context!
 

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