How much solar to install?

wind? man do we get wind here... 30 mph n more... has actually caused damage to people homes around here...

not sure solar would be safe... and wind power could also be at risk...

 

I have a wind mill but dollar for dollar it is no match for the solar panels. We don't get much wind in the summer but it will pick up a few watts in the winter, sometimes it will run all night if it is a windy night which is handy but I think I would need a few more to do much good.

 

If batteries are full and freezer cold then use it to heat water if nothing else... 4000 watt heater element at 240 volts will only be 1000 watts at 120volts. 1/2 voltage means 1/2 current equals 1/4 power dissipated! Couldn't hurt.... 1000 watts over time can heat a lot of shower water.

 

Oh and the nice thing is heater elements don't care if it is DC or AC, sine wave or modified sine wave. Inexpensive inverter would work just fine.

 

By real ONCE @sourdough145

Be smart , not like me .
Pure real stuff is the way to go , 50 years in this

 

I have a mini split heat pump that kicks on when the batteries are fully charged along with a heat pump water heater. I put 2000w 480v elements in the water heater because if the water is really cold it will run one of the elements and the heat pump. The 480v elements only draw about 500w at 240.

 

+1.
You can get a really good inverter for $1400 and it will last a lifetime.

 

I run Outback , they are field serviceable, parts from WA state , shipped right to you around the world , same as the best charge controller is Midnight Classic , right across the tracks from Outback power in Arlington WA , sunny boy and Schneider are just down the street , were all in 6 blocks where all this real stuff is made. Testing a few new items to be released (not today , grey as night) I like the diagnosing of the Outback VFX series , even if your not going to tie to the grid , selling later or joining a link in between is easy .. Do NOT get yourself into jam for a few bucks .Use real tools to splice and the proper crimps and splicing , Use wire that has no sections or joints , just one length , I have found so many bad connections ,, .
JFI

Sloth

 

Some great replies. First thing you should do is buy a "Kill-a-watt" watt meter. They are about $12 on sale, or $15 regularly. (More in fancier stores). You can use that to plug into each item you expect to use in your cabin. That can give you the total wattage of your appliances. One of the biggest shortfalls of many designs is that people forget about start up requirements of electric motors...an air conditioner can draw a lot more wattage on start up. An undersized inverter can lead to problems.

Next, you need to apply some thought to useage. Are you planning on having the capacity to run everything at once, or are you OK with taking some things off line for having a smaller solar capacity? Are you going to build in a little excess capacity for growth? How about storage? How long would you want your battery power to last when the sun isn't shining?

Once you've got those items in hand, you'll know your "watt/hour" capacity needed and can plan your solar array and battery storage needs.

One way to ease into this is to build yourself a small solar generator on a cart. You can make yourself a portable generator with a 100w panel, 2000w inverter, and a couple of deep cycle batteries to play around with...run a radio, a saw, a coffee maker. Play around with that set up and gain some experience before you make the (expensive) jump to a larger system.

 

ON that above post , were in a 12Vdc system and 100w panel is just enough for battery trickle maintenance.
Im saying 300W 72 cell high voltage 45Vdc VOC panel and use a pwm Brat CC and then you'll get a 12 Vdc harvest that can support a draw.
100W 60cell panel is 18Vdc that is just enough for keeping a battery charged.

Sloth

 

I hope you were saying to use a MPPT charge controller on the high voltage panel. Use of a PWM controller on a high voltage panel will work but will only give you current rating of the panel not the full power. PWM works best if panel voltsge is only a few volts over battery voltage. MPPT will convert the extra volage,and current to a usable level... PWM say 45 volts at 10 amps will charge a 14.0 vdc battery at 14.0vX10amp=140watts. MPPT takes the full 45vdc and 10amps or 450 watts and converts it to 14v for around 32 amps of charge current (full wattage of panel). So the advantage of true MPPT over PWM in this case would be 310watts or 22 amps of charge current. It would take two more panels to make up the charge current difference using PWM. MPPT in this case would be worth the price difference... Agree that 100 watt panel to charge a pair of deep cycle is a bit weak. Not too bad if only one battery and if you aren't in a hurry... as always YMMV

 

Read the specs and be wowed !!
Page 11 for max PV
What a brat is
Now if you think a e-bay 12 buck MTTP can handle a 72 cell panel , what you wrote ^^^ up there is the true nitty-gritty .they list MTTP but are PWM and cheap..
Next would be a real MTTP unit to play !!
You gave a cheap system , but don't buy crap stuff. Brats on sale are 80 bucks or less, Kids are 3-400 and are wanted more.
The brat put out 3 times the watts/amps from a high voltage panel than 10 Asian controllers , but compared against the Kid , on ONE HV panel , dame close 2-5% less , depends on day ..

I run brat ,kid,classic ,plus many more makes. Northan test ground ..
I have had asian fires with my e-bay MTTP controllers , thats why they are in metal boxes ..
Id GUESS Asian MTTP is limited to 45VOC on a 24Vdc and 30VOC on a 12Vdc systems , that is max VOC..
say 3-5 fires or burn outs , and crap output ..,,,Nice lights tho !!!

Sloth

LINKs supplied in blue Read them

 

I have a somewhat well to do "neighbor" (about 6 or 7 miles away) who just had a 9.9 kW array installed.
It looked like a really first class job. The racks and panels cover a concrete pad and provide for a shaded area large enough to park a full-size pickup under.

To quote @Cruisin Sloth "Now if you think a e-bay 12 buck MTTP can handle a 72 cell panel , what you wrote ^^^ up there is the true nitty-gritty .they list MTTP but are PWM and cheap.."

Cheap charge controllers scare me, not so much that they may turn into a solar flare, but they scare me because I'm afraid they'll turn a very expensive battery bank into a few hundred pounds of scrap lead.

If you're working with a single used 12 volt RV battery or some such, it might be worth the chance. But other than that.....

 

I made my own charge controller out of a 1950s voltage regulator a relay and diodes and fuses on each line.
Fuses are your friend no matter what you are doing electrically.
Diodes control the direction of the flow of DC power so that at night the panels do not draw off the batteries. Usually, there are diodes on each solar panel.
I have picked up used ones that a diode had failed, and simply replaced them and good to go.
Amature radio teaches one to put fuses on both the positive and negative leads, good practice.
A battery system done right is golden.
Always build for more than you expect and larger gauge wire than it normally requires and give plenty of room to work and an apparatus to help to lift.
Allow for newer different batteries in the future.
Every single component of my system has a 3 position 20 amp switch; up to test, center to take offline, and down =on line.
Being some of my panels are vintage I like to keep track on how they are performing, so far only one has been replaced 50+ years is good life out of an ARCO solar panel. Except for sheet metal, you can't get that out of roofing.
I don't worry about trying to harvest every last milliwatt out of my stuff, even if an antique is contributing .5 amps, it is a contribution none the less. And the only reason the older ones fail is the resin they used in those days tends to yellow and block the sunlight.