Solar in the Shade

ToManyTrees · April 2014

Hello All, and thanks for having me here.

I have a small off grid cabin in the Cascade Mountains of Washington St., elevation 3000 Ft. My property, all Timber Land, is normally covered with snow 5…6 months of the year, 4…7ft being the norm. I power it with a Honda 2000i.

I also have a battery bank (18, 2V batts @12V 500AH, C&D Technologies, 1996 vintage, not Deep Cycle) and a 3KW MSW inverter for occasional use. Last fall I added three 100W panels & a cheap PWM CC from Renogy to try and help out my failing Batteries in winter.
(I acquired batteries in 2007, Free). I mounted the panels vertical on the east end of my generator house, facing, yup, TREES… So, in five months I pulled in 672 AH, but it all helps, I guess.

Okay a little about the place. I grew up there from the late Forty’s, Logging & Sawmill family. Man“ I am getting old & gimpy & grumpy”. The Cabin has a propane Stove, Refer. & WHeater, All lighting is changed to LED, Satellite dish, LED TV, wood stove for heat. My normal running load is 150W, about six hours a day, weekends mostly, and I run a 1100W Microwave (input from “Kill A Watt”) some days for 3…5 minutes. I have a Creek with a gravity fed system, 1800ft. of 6”dia. pipe @ 30psi. so, some Hydro is possible later.

The Plan, first, I am not an Electrician, but fairly handy with a Chainsaw & Equipment. A buddy & I started dropping trees last weekend, letting some direct sun in, about 5hrs. a day at this time of year. More trees to go this week.

Let’s look at this as a Hobby, Learning Experience. System to be 24 Volts, no line loss over 2%
Generator as primary, Solar as Back Up.

Panels, I have Eight, 100W from Renogy

Optimum Operating Voltage (Vmp): 18.9 V
Optimum Operating Current (Imp): 5.29 A
Open - Circuit Voltage (Voc): 22.5 V
Short- Circuit Current (Isc): 5,75 A
Maximum Power at STC: 100 W
Operating Module Temperature: -40°C to + 90°C
Maximum System Voltage: 715 VDC
Maximum Series Fuse Rating: 15 A

CC, looking at the Midnight KID (to be used with Hydro @ later date)

Batteries, thinking Crown 12V 185ah X4 = 370ah

Inverter, looking @ Magnum Energy MSH4024RE Pure Sine Wave Hybrid Inverter (loads limited to 2500W).

Battery Charger, maybe Iota Engineering DLS 27-40 24 Volt 40 Amp Regulated Battery Charger.

I also have a Honda 3000si, converted to auto choke. Onan 4kw, auto start. I purchased a Midnight combiner box & probably the wrong DC breakers (12amp). The Midnight mini DC disconnect 175A, and two 30A breakers for PV & CC, & GFI. Are on their way from our host NAWS. Well that’s my line of thinking, time for you all to whack me with reality. Thanks in advance.

PS: Thanks Bill for fixing my IP, problem.

Thanks all, TMT / Paul

https://www.youtube.com/watch?v=3tfmmqDecKQ

https://www.youtube.com/watch?v=hkkcNFyz2qg

BB. · April 2014

Re: Solar in the Shade

Welcome to the forum Paul!

There are several ways to design the system... Ideally, we like to start with your loads, then size the battery bank. And finally the charging sources (solar, generator, etc.).

For your system, 150 watts * 6 hours per day = ~900 Watt*Hours per day.

That, is a pretty small system. The Microwave is the wild card--Because the battery bank+inverter+wiring needs to be heavy enough to manage the ~2kWatts from the microwave. And a larger battery bank should really have a larger array for proper battery charging.

And, of course, there is the whole issue of enough sun. Either continuing to clear out some trees (which may be a good thing anyway--reduce fuel loading/fire hazard, a bit nicer to get sun at the cabin, etc.). One question--Do you have a clearing withing ~1,000 feet or so where you could mount an array so you can avoid more cutting than you otherwise need?

Anyway... Lets look at the battery+inverter system first. A 1,000 Watt*Hour per day, with 2 days of storage and 50% maximum discharge works out very well for lead acid battery systems as a rule of thumb (1-3 days of storage, 50% maximum discharge for longer battery life). Or:

1,000 WH * 1/0.85 inverter eff * 1/12 volt battery bank * 2 days * 1/0.50 max discharge = 392 AH at 12 volt battery bank.

Throw a 300 watt TSW MorningStar 12 volt inverter (reliable, very nice power save mode/remote on-off input)--And other than the microwave, you are good to go.

Then, look at the microwave... In general, long term discharge for a lead acid battery bank should not exceed ~C/5 (20 hour capacity of battery bank divided by 5 hour discharge rate). So a 1,500 watt microwave:

1,500 Watt * 0.85 inverter eff * 5 hour discharge rate * 1/12 volt battery bank = 735 AH @ 12 volt battery bank

That is just about the limit that I would suggest for a 12 volt battery bank. And 1,500-2,000 watts is pretty much the limit for a 12 volt AC inverter. The wiring and charging current is getting pretty large. For example the branch circuit current for a 12 volt inverter would be:

1,500 Watts * 1/0.85 inverter eff * 1/10.5 inverter cutoff * 1.25 NEC derating for wiring+breakers = 210 Amp branch circuit for a 12 volt system

Assuming you want to run the microwave from the AC inverter and not fire up the genset (to be clear, for your system, if you are running the genset a lot because of poor solar/shading/weather, having a smaller system + genset for microwave is probably an optimum design here), the system is getting large enough to run an Energy Star full size refrigerator...

So, looking at a refrigerator at ~1.2-2 kWH per day, plus your other loads (water/well pump, possible washing machine)--Call it ~3.3 kWH per day for a very energy efficient lifestyle, the battery bank would look like:

3,300 WH per day * 1/0.85 inverter eff * 1/24 volt battery bank * 2 days * 1/0.50 max discharge = 621 AH @ 24 volt battery bank

Add a 1,500-2,000 Watt inverter--And you would be good for a full off grid home.

Anyway, that is where I would start. Once we have the battery bank/loads nailed down, then it is just a matter of doing the math for the rest of the system design. Your thoughts/needs?

-Bill

Cariboocoot · April 2014

Re: Solar in the Shade

Well Paul I already am old, gimpy, and grumpy.

Point the panels South, and get handy with the chainsaw if need be. Panels don't work in darkness.

You've got a bunch of mismatched stuff. What you haven't got is a plan. Or at least not a complete one. You need a magic number to start with: how much power in Watt hours do you need/want? Without that you're guessing at equipment and spending money unwisely.

I can tell you that 800 Watts on 24 Volts is good for recharging about 256 Amp hours of battery. Not 370 Amp hours.

I can tell you you don't want to put four batteries in parallel.

I can tell you the Kid is good for 30 Amps so it would work for that theoretical 256 Amp hour bank.

I can tell you that you could get four 232 Amp hour East Penn/Deka (PS2200) 6 Volt batteries and have about 1.4 kW hours available at 25% DOD.

I can tell you that I have about the same and manage to squeeze 2.4 kW hours out of it in Summer through careful power management.

I can tell you the Magnum has a built-in charger so no additional charger is needed.

I can tell you I haven't had breakfast yet, which is irrelevant, but I'm going to now.

ToManyTrees · April 2014

Re: Solar in the Shade

Bill & Cariboocoot,

Thanks for your insight

TMT / Paul

westbranch · April 2014

Re: Solar in the Shade

Love that Second Growth, nice and tall and straight! Up here you might have to look hard for a mill that can still handle that size if you don't want just 2x4's from it... shame....

ToManyTrees · April 2014

Re: Solar in the Shade

Hi WB

Yes, I probably should market some. I did buy a Norwood bandsaw mill last year. I can mill logs 29" dia. X 21.5'. I have the Lumber thing covered, and that's a learning curve also. Now, if I can just get my old thick head around all this new power stuff...

TMT / Paul

niel · April 2014

Re: Solar in the Shade

as was said the charging of the batteries from solar only can be a problem, but you can feed most of your power from pv to power the loads during the sunny times. you have 800w of pv and that might translate to about 400w useable, but over 3-5 hours of full sun hours depending on the time of year and weather this can be about 1.2kwh to 2kwh and can cover your loads well.

you do need to get better batteries as used can be iffy. think expansion as putting in any kind of hydro power will translate to quite a bit more power available as wayne can attest. most systems do expand to one degree or another from expanding the loads which everybody tends to eventually do. you have good potential for a viable setup.

PNjunction · April 2014

Re: Solar in the Shade

For batteries in the Pacific Northwest, or anywhere you may have limited solar insolation, I would suggest AGM batteries. They have about twice or more the CAR or Charge Acceptance Rate, which basically means that more energy goes into charging than does heat. This is due to lower internal resistance than a flooded type.

The secondary benefit is that most will accept up to twice or more the standard charge current than a flooded, making charging that much faster which is needed when solar insolation hours are low.

High quality TRUE deep cycle agm's are available from a number of suppliers.

ToManyTrees · July 2014

Re: Solar in the Shade

Hi All

Well I am still working on this, with a few set-backs. I went on an Old Man Road Trip for two weeks. The following weekend my buddy & I dropped 20 more trees & burned all the debris. Then things went south. After working all day we tapped the leftover Buffalo Trace, (KY. Whiskey) from road trip. My buddy (73) decides to take off on his Quad Runner, and rolls it… Called in the ambulance, hauled him seven miles to an open area, then Life Flight to Portland Oregon. He is on the mend, Broken Nose, Cheek bone, Collar bone, 9 broken ribs... Solar & Booze don’t mix, or, were just old fools. (Fools)

The generator house expansion should be complete in two more weekends. I cut all the lumber from felled trees. I will build a wooden panel rack for the roof that can be tilted for winter snow. Five segments holding four panels each.
The equipment list has changed a bit, I now have. (spending $$$$ unwisely).

The system will be 24V.

20, X 100 watt panels, two in series, ten strings

Optimum Operating Voltage (Vmp): 18.9 V
Optimum Operating Current (Imp): 5.29 A
Open - Circuit Voltage (Voc): 22.5 V
Short- Circuit Current (Isc): 5,75 A
Maximum Power at STC: 100 W
Operating Module Temperature: -40°C to + 90°C
Maximum System Voltage: 715 VDC
Maximum Series Fuse Rating: 15 A

1, MNS Classic 150 & WBJ

Combiners, breakers, Etc. I need to get wire next. Battery jumpers & inverter wire will all be 4/0. Everything else will be the largest I can get in the terminals, 2 & 4. I will start out using my old C&D batteries, I still have 12 fair ones. I will buy new batteries later, L16’s 435AH. Inverters, a pair of Outback GFX 1424’s, maybe just one, we will see how it works with the gen. support.

Anyway, just an up-date, later TMT/Paul

TucsonAZ · July 2014

Re: Solar in the Shade

If you're going to go with that much solar, I would strongly suggest going to grid tie (24v) panels, do what you're doing with the Renogy panels but with 48v into a 24v battery bank. It will save you a ton of money and be all around battery/easier for you to manage.

One thing they may have missed up above is that the solar is the backup so you have some room it sounds like. It may come down to some trial and error on your end but you're asking the right questions.

I will be up in your area in a few weeks, if you need any help with anything let me know. I was planning to look for, at, around some land in the Medford area with thoughts of a potential summer dwelling, we'll see though.

Also, you forgot an "o" in your user name, I'm a homophone nut job, with your consent I will pay a mod $2 to add that "o" so that I feel balance in the universe has been restored.

PS Renogy will sell you the 100w panels for $115 each including shipping, I know this for fact.

PPS I will be sending positive energy your friends way, sorry that happened, it really sucks.

Cariboocoot · July 2014

Re: Solar in the Shade

TucsonAZ wrote: »

Also, you forgot an "o" in your user name, I'm a homophone nut job, with your consent I will pay a mod $2 to add that "o" so that I feel balance in the universe has been restored.

Forgot an 'O'? Not necessarily. Think about it.

I agree that buying twenty 100 Watt panels to put on an MPPT controller is a waste of money as the larger (200+ Watt) GT style can be had for about half the money. Same Watts, less dollars.

BB. · July 2014

Re: Solar in the Shade

And our best to your friend... That is a tough accident to recover from at any age--He sounds like a tough old 'coot.

-Bill

ToManyTrees · July 2014

Re: Solar in the Shade

TAZ, CC & Bill

Well the panels are sitting here in a pile. I looked at GT locally, but felt that I could not manage their size & weight. I have a metal Femur in my left leg, so I stumble around with a cane most of the time….

BB. wrote: »

And our best to your friend... That is a tough accident to recover from at any age--He sounds like a tough old 'coot.

-Bill

Thanks Bill, My buddy is also named "Bill". It takes four of us old guys to equal one youngster now, LOL.

TMT / PAul

TucsonAZ · July 2014

Re: Solar in the Shade

Cariboocoot wrote: »

Forgot an 'O'? Not necessarily. Think about it.

I'd like to extend a thank you "to many trees" for my lack of full solar output.

I'm not getting full output from my solar panels because of "too many trees".

Yeah okay fine, you win (:

TucsonAZ · July 2014

Re: Solar in the Shade

ToManyTrees wrote: »

TAZ, CC & Bill

Well the panels are sitting here in a pile. I looked at GT locally, but felt that I could not manage their size & weight. I have a metal Femur in my left leg, so I stumble around with a cane most of the time….
TMT / PAul

That makes perfect sense! Even more so on a gusty day.

ToManyTrees · October 2014

Re: Solar in the Shade

Hello All
First off, I would like to say thanks to everyone that invests so much of their time & knowledge here, Thank you all !!! My little system has been up & running for two weeks now, and I am extremely happy with its performance. The only things left to do, cut down more trees, AGS wiring, (Solar Converters GS-1AC), cut more trees, new batteries next year, and cut trees…. I am currently using my old C&D batteries (1996 vintage) and they are doing a surprisingly well.

TMT/Paul

Ks Solar · October 2014

Re: Solar in the Shade

I hope your buddy is healing up ok.. I am a transplant from Wa. Use to run around above Wilkeson. Love it that place. Go every chance I get.
Your system looks good. Looks like you did a lot of reading and it shows. I can attest to the 200 w panels being big unless you have 2 strong / agile boys to do it for you.. I am only 53 but my balance / confidence on a ladder has really taken a hit the last few years. Too many back surgeries / nerve damage. Now I like my bucket truck much better

Your framing skills show also. That's a damn nice "shed".

westbranch · October 2014

Re: Solar in the Shade

TMT which model batteries are you using...?

PS, if you add a system description to your signature line, we would not have to bug you as much... tks

BB. · October 2014

Re: Solar in the Shade

Do you have good ventilation around your inverter/charge controllers? It is hard to tell--There may be cabinet doors over the electronics???

An old engineering rule of thumb--For every 10C (18F) increase in operating temperature, there is a 1/2 reduction in life of the appliance/device/component. You have around 5% of the energy from the solar array as waste heat from the Charge controller and ~15% of the energy going through your AC inverter being loss as heat.

On a bright day with lots of loads, you could have a couple hundred Watts of "heating" in your cabinet/shed (batteries will also heat a bit from charging/use--Keep an eye on them to make sure they do not get too hot--Install thermometer on the bank/in the box).

-Bill

ToManyTrees · October 2014

Re: Solar in the Shade

Ks Solar wrote: »

I hope your buddy is healing up ok.. I am a transplant from Wa. Use to run around above Wilkeson. Love it that place. Go every chance I get.
Your system looks good. Looks like you did a lot of reading and it shows. I can attest to the 200 w panels being big unless you have 2 strong / agile boys to do it for you.. I am only 53 but my balance / confidence on a ladder has really taken a hit the last few years. Too many back surgeries / nerve damage. Now I like my bucket truck much better
Your framing skills show also. That's a damn nice "shed".

My buddy Bill is doing great, but it was a long summer of healing. He dropped four more trees last weekend. Looks like this will be a SOP as the sun angle drops. Bucket Truck, nice. I had a chance to buy a nice one for 15 cents a pound, passed on it, 34ft. reach. Another friend bought it and sold it for 14K... Stupid me...

https://www.youtube.com/watch?v=jfbjP7UdCmg&list=UU8BlSOHk9bZjiqmdJrfOa5Q

TMT / Paul

ToManyTrees · October 2014

Re: Solar in the Shade

westbranch wrote: »

TMT which model batteries are you using...?

PS, if you add a system description to your signature line, we would not have to bug you as much... tks

Westbranch, The batteries came from a aluminum smelter substation. They are float service for switch gear & emergency lighting. C&D Technologies KCR9, we had two set of 60, I grabbed 20 to play with.

Signature Line, I see it does not show in early posts. I don't what else is pertinent, please advise. Thank You

TMT / Paul

edit, http://www.cdtechno.com/pdf/lit/12_316_0512.pdf

.

ToManyTrees · October 2014

Re: Solar in the Shade

BB. wrote: »

Do you have good ventilation around your inverter/charge controllers? It is hard to tell--There may be cabinet doors over the electronics???

An old engineering rule of thumb--For every 10C (18F) increase in operating temperature, there is a 1/2 reduction in life of the appliance/device/component. You have around 5% of the energy from the solar array as waste heat from the Charge controller and ~15% of the energy going through your AC inverter being loss as heat.

On a bright day with lots of loads, you could have a couple hundred Watts of "heating" in your cabinet/shed (batteries will also heat a bit from charging/use--Keep an eye on them to make sure they do not get too hot--Install thermometer on the bank/in the box).

-Bill

Bill, The add-on is 6' x7' with a 6' 6" ceiling. I cut full dimension Cedar 1" x 12" for the siding (board & batten) then 2" of R13.1 foam, then installed a 3/4" plywood liner, total R factor of 15+. I see that the pictures are confusing. #2 is taken when installing the hinges #3 is after installing equipment, sorry... I know heat will be a problem in summer. I am tinkering with trying sort of a cold water exchanger, as I have an unlimited supply of 55deg. water. If I cant make that work, then a mini AC unit i guess. So, besides the the battery temp monitors on the CC & OB, add another air temperature sensor just for the batt box ? Both building are set-up to pull cool filtered air from underneath the addition.

Thanks TMT / Paul

BB. · October 2014

Re: Solar in the Shade

If the Charge Controller / Inverter battery temp sensors are easy to read--You don't need another one.

Just want to make sure you have good ventilation (especially in hot weather). Sometimes inverters+charge controllers are installed in virtual closets (on purpose, or by accident to keep kids away from gear)--They need good ventilation to keep cool (or at least not hot). It is easy to have heat build up under shelves/ceilings/etc. too.

Temperature cycling is also hard on components too (cold/hot/cold/hot).

You may not need active cooling--A fan to move air from "dead spaces" may be good enough to keep temperatures reasonable.

-Bill

ToManyTrees · October 2014

Re: Solar in the Shade

BB. wrote: »

If the Charge Controller / Inverter battery temp sensors are easy to read--You don't need another one.

Just want to make sure you have good ventilation (especially in hot weather). Sometimes inverters+charge controllers are installed in virtual closets (on purpose, or by accident to keep kids away from gear)--They need good ventilation to keep cool (or at least not hot). It is easy to have heat build up under shelves/ceilings/etc. too.

Temperature cycling is also hard on components too (cold/hot/cold/hot).

You may not need active cooling--A fan to move air from "dead spaces" may be good enough to keep temperatures reasonable.

-Bill

Thanks Bill, I will install another, Room temp. & Box temp.

Paul

Solar in the Shade

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