Learning and planning (or planning to plan) a system

System

***Please excuse the long winded info (I wanted to be sure you knew the whole story)

Thanks for all the fantastic information on this forum. I gathered together more info on this site than picking up this and that for a year on other places. It also helps that NAWS seems to be the cheapest retailer for some of the pieces I will be getting in the near (relative) future.

I have done some research, purchased some "starter" pieces that I have experimented with over the past year and now I think I am finally ready to be schooled by the professionals...

I built a cabin in Southern Utah for vacation and possible retirement (several years). I had the opportunity to purchase some panels a few years back, so I decided that the cabin will be Off Grid as opposed to expensive, but accessible grid power. I picked up 3 Kyocera 130 watt panels and installed 1 of them for minimal power needs on a small Off Grid, permanently mounted trailer while building the cabin. I hooked it to a PZ MPPT-500 charge controller (recently crapped the bed), 2 cheap 6 volt 110 AH batteries (12 v system), and just a cheap and inefficient Vector 800 watt inverter. This met almost all my needs for minimal living (lighting, 12 volt trailer lights, water pump, satellite internet, computer, TV/
dvd)

I am calculating that daily power consumption at the cabin will be 1200 - 1500 watts (figured closer to 1k, but I know what will happen...)

Elevation is 6600' feet with intense sun. Charts say between 4.5 - 5.5 insolation, but with my tracker I get 6+ hrs of good sun most spring and fall and more during summer. During summer my panel faces the sun for close to 10 hrs as it tracks.


It's time to set up the cabin...

PV - 3 Kyocera 130 watt panels (would like to possibly double in the future)
Charge Controller - PZ seems like crap, looking for suggestions
Batteries - I was looking into Trojan L16-RE-B (bank of 4 / 6volt) - 370 AH
Inverter - A friend suggested a Magnum 2812, but looking for suggestions

The array will be pole mounted with tracker 30' from the electrical panel of the house. I was planning on external batteries (under my deck), against the circuit panel wall.


Money is certainly an object, but I understand that you get what you pay for and I want a system that will last with proper maintenance and can be added on to instead of replacing in the future.



Thanks in advance for any suggestions.

Bill (extreme NOOB)

niel

Re: Learning and planning (or planning to plan) a system

a few points right at the start.

1> bz controllers are junk. if you actually meant pz then i don't know what you are referring to. i do agree for an mppt cc, but you may need to buy a bigger one because of point 2.

2> with 2 strings of batteries for a 12v configuration this is 370ah x 2 =740ah total. trojans like about a 10% charge rate so 740ah x .1 = 74a. i don't think you'll get that from 3 130w pvs. even cutting the bank in half it'll want 37a.

3> you seem in or a tad beyond the ball park for pvs to power needs as i figure you will generate what you'll need plus a bit more if the tracker is good (not broken down) and it stays sunny. murphy's law says it's break down and you'll have lots of clouds.:grr anyway, if you insist on that much battery then be prepared to buy far more in pv than you figured, but cutting the battery bank in half will yield 370ah x 12v = 4440wh and to not go below 50% dod means 2220wh usable. that fits your needs better at this point. the 3 pvs may give about 22a and that will be short for trojan's recommendation. roughly 5.9% and the guys like to derate pv output by 23% so 22a x .77 = 16.94a or 4.57%. you need to double your pvs for the batteries, but it may help in making up for cloudy periods too.

System2

Re: Learning and planning (or planning to plan) a system

Neil,

Yes, I did mean BZ, everything that I have heard is "junk" and mine lasted 2 years.

Thanks for the quick reply. I assumed that more battery was slightly better, but didn't figure that I needed double the PVs AND half the batteries, lol.

Everything that I hear is to use the same batteries (same size and age), so would it make sense to buy "temp" batteries that would charge better on the 3 existing PVs? Once I upgrade more panels I could then swap those out for bigger batteries that would make more sense.


Thanks again,

Bill

Cariboocoot

Re: Learning and planning (or planning to plan) a system

One thing you have going for you: 6600 feet of elevation. Your panels are likely to operate more efficiently than the "typical" 77% factor. At 3200 feet mine run 80-82% out the charge controller.

The basic design plan starts with the loads. You're looking for 1200 to 1500 Watt hours per day. That's a pretty easy figure to attain on a 12 Volt system. The other question would be what these loads are? You need to know that things with induction motors tend to have high start-up surges which must be accommodated, and you need to size the inverter for maximum Watts that will be used at one time.

Otherwise, a pair of 6 Volt "golf cart" batteries would do to begin with. At 50% DOD you'd have a bit more than 100 Amp hours, which is roughly your base 1200 Watt hours. If you can manage a bit of load shifting the panels will give you a margin over that.

Picking on my favourite Trojan T105's (others are similar) you try for 10% peak charge current. That usually brings everything in line. In this case that's 22.5 Amps @ 14.8 Volts charging, or 333 Watts. Since your panels will likely also be 80% efficient (or better) that would be a 416 Watt array. You can probably get away with three Kyocera 135 Watt panels; that's sort of the minimum for a set of golf cart batteries. Four will probably make you happier. That would be a 540 Watt array. If the tracker is good, this could support 450 Amp hours (two sets of T105's) and realize 2 kW hours a day, possibly a bit more.