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Question about solar energy


Okiepan

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Ok I am thinking about a solar energy project to run maybe a air conditioner( small window unit), a light or two maybe something else in a 400 sq ft cabin.

How many watts of power is needed and panels to power up this idea ?

also thinking about a small RV lpg refrigerator if one can be found fairly resoniable in cost .

 

 Thank you all 

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RV propane fridges.. Common brand is Dometic, not "domestic," Dometic.

 

Running an AC from solar... Can be done. Specific A/C unit with low startup amps (the motors have a strong inductive surge on startup), and plenty of panels.

 

400 square foot cabin is bigger than a 20' RV, but do recall someone making solar work on an RV about this size with panels on the RV and more panels on the tow vehicle. In Arizona.

 

If you are serious, I am willing to support this discussion over time. It may involve some algebra if you can handle that. It isn't bad math, stuff like V X R = A, V X A = W, and I^2 X R = W.

 

But a short answer... After considering budget, and comparing to need... Upgrading the RV to 2 batteries instead of one, upgrading on-site propane tanks from 2 X 20 pounds  with a couple 100 pound supplemental tanks, and getting a generator for the microwave and AC, and getting ready to evaluate the existing charger setup to add inverter (120 VAC) capability.

 

The inverter will not run the microwave or AC, it can run computers, radios, charge battery-operated tools, a lot of smaller stuff. It can also jump the tow vehicle. The generator cost less than panels, batteries and electronics for running an AC, and the tow vehicle has a fuel tank. But it can be done.

 

Running an AC is kind of the Holy Grail of appliances. If you never get to your target temperature, it never shuts off; A bigger and more efficient unit might consume less power overall because it will cycle on and off. But it needs more power (panels, batteries, and electronics) when on!

 

Need a bit more info to help you... This cabin... No power company available? Or the cost to hook in is very high? Or do you want to set up a bugout home?

 

I have electric utility to my home but the power goes out often on my mountain. The RV provides a cool room in the summer and warm room in the winter. And long-term off-grid capability, and bugout (or bugin) ability.

 

What is your cabin for? Why do you want (or need) off-grid capability? 

 

 

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Lighting is really an inconsequential load.  Sizing a solar system all depends on the wattage output of the panels, the calculated watt-hours of energy needed and the reserve power in battery storage to supply those needs, environmental factors (average sunlight, cold weather affect on batteries, how long will ac run on hot day, days with no sun).


Example

My friend in Montana had an off grid home (about 900 sq ft). Cant recall the number of panels and the size of battery configuration, but due to overcast Montana winters, solar production was pretty much non existent, so he had a supplemental propane generator that not only put out 120/240 to the home but also 12 or 24 volts to his solar battery bank. I recall him stating his total solar/genset configuration exceeded $20k. I’m pretty certain the genset was over $14k range but forget the kw output, having installed that when solar and his little windmill failed to prove reliable power his first winter there.  No AC in the home. It was NW Montana, but he had other regular appliances. Lived there full time for 9 years.

 

Id find a contactor local to your area and familiar with your environment for accurate information and details on what equipment works best. 
 

 

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I run an AC off my truck sometimes using a full sine wave 1000 watt inverter.. A 5500 BTU draws about 400 watts at max.

 

If this thing in the link will run your setup, surely you can put something together with golf cart batteries, a controller, and solar cells for less. I use different setups at hunting camps and they run things fine.  Get enough panels to run the AC during the day and maybe scale back at night on the AC, even fans if you can.

https://www.goalzero.com/shop/portable-power/goal-zero-yeti-6000x-portable-power-station/

 

The choices for fridges are endless but I opted for yeti ice chest in the shade.  I mix blue ice with regular ice and it last me right at 12 days. My dad only uses a small deep freeze that keeps frozen stuff frozen and freeze ice packs that he uses in a small yeti to keep his milk, eggs, bacon, and maybe a tube of cheap biscuits cool. The small deep freeze is a much more efficient option. He even keeps a small jar with ice cubes in it to know if it has ever defrosted for some reason. If the cubes melt and refreeze you’ll know it by looking at it.

 

I run an electric ceramic heater in my small camper because I don’t like anything gas while I’m sleeping.

 

Plenty of inverters can run microwaves but when your watt hour capacity in the battery is gone, its gone like at night or too small of capacity.

 

There are so many ways to get it done

 

At the end of the day for me, the Holy grail is a hot shower, poop, a king sized bed, box fan, and a single butane stove eye.

 

Don’t over look a cubicle made with foam filled concrete blocks with a Honda generator inside.

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24 minutes ago, Wallaby Jack, SASS #44062 said:

I can tell you this:

 

 

 

 

 

 

  ............. solar energy comes from the sun.

and the sun dont always shine on us no matter how hard we look for that silver lining 

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I’d like to address this, you have the right equipment and you get charge even in the rain as long as its during daylight hours, sometimes the moon too.

 

The problem with the whole thing and the reason green energy is a farce is the sunlight is useless without all of the non-green produced equipment it depends on. The equipment takes massive energy and pollution to produce and it constantly has to be replaced, upgraded, and maintained. It never pays for itself.

 

The only “silver lining” is having power where power is not available.

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7 hours ago, Wallaby Jack, SASS #44062 said:

I can tell you this:

 

 

 

 

 

 

  ............. solar energy comes from the sun.

In other words, Hydrogen of one form or another.

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You have to think of solar power as two different processes.  The first is producing DC current to charge the batteries.  The second is changing the DC into AC current via an inverter to power the AC unit.  If you're looking for off grid, a combination of solar for charging batteries and a small generator for running AC devices would be the most cost effective solution.  

 

If your house is hooked up to the grid, you can set up the solar system to push the AC current back into the grid through a special meter, however, the power company will only pay you wholesale rates for the power you "sell" them.  If you live where the power rates are high, you may find solar cost effective.  I've looked into it and in my area, it won't pay for itself in my lifetime.  

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I like to call my solar panels " long range nuke power receivers "

26% tax credit was the hook for me 

my bill is 11 bucks a month  for 3 window AC units and charging  my GF batter BMW

Nuke powerd homes RULE 

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Bottom line, its no different from feeding yourself, figuring out what to do with human waste and trash refuge, cutting wood for a fireplace, or whatever else necessary to life...its an ongoing non permanent process.

 

 

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Also solar panels degrade over time at about 1% of output. Now that is not much, but over 10 years it is something to consider. More importantly than the panel degrading is dust, bird droppings etc collecting on a panel which significantly reduces efficiency so keeping panels cleaned is a major consideration.

 

I suggest you consider getting appliances designed to run on DC current.  Available for RV's and other uses. This does reduce some line loss and conversion to AC loss.

 

Storage of energy created by panels in battery form is important to consider not only storage loss, costs of batteries and then conversion loss from battery through inverter to AC if you go that route.  Considering only running DC lights and appliances will reduce costs.

 

As to how much panel production you need the math is pretty simple add up the total starting wattage of the AC and other appliances and that will tell you how much wattage you will need to be producing AFTER the solar cells produce DC and is converted to AC, or if you have DC lights and appliances the total normal use computation is simple.

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CQ and I have lived totally "off the grid" for over 25 years now. It is NOT cheap and it is NOT easy. Solar panels are the cheap part. For a very small system like you are talking about 6volt golf cart batteries are the most cost efficient storage. Trojan brand are the best. We live a pretty normal life with 15KW diesel generators at both locations (business and residence). Use 500amp hour 48volt battery banks.  6Kw pure sine wave inverters. The inverters start and stop the generators automatically as needed. Both setups are identical. about $35K each. We used lead acid based batteries for about 20 years. Horrible. Acid leaks and off gassing inevitable, refill with distilled water every month, the best ones only last about 7 years, about $12K per set.  Finally put in nickel/iron batteries at both locations. (Edison's original design). They use caustic so no acid issues, last essentially forever, but still need distilled water. But due to cost, size, and weight they are totally impractical for a small system. 

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"The inverter will not run the microwave or AC, it can run computers, radios, charge battery-operated tools, a lot of smaller stuff. It can also jump the tow vehicle. The generator cost less than panels, batteries and electronics for running an AC, and the tow vehicle has a fuel tank. But it can be done."

 

My RV has 700 watts of panels, 4-6volt AGM 200AH batteries and a 2000 watt inverter. It runs the microwave and will run the 13,000 btu AC for awhile. I don't because I also have a 5,500 watt LP generator for that.

 

Read all you can about solar systems. It usually will come down to the number and type of batteries, the inverter size and the ability to keep them charged as they are drawn down.

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Many of the RV'ers are going to lithium batteries. They can be drawn down to 10% with no damage. But, they are $850 to $1,100 each for a 100 AH battery. They don't like the cold. Below freezing they don't work well and or charge well. Many have heat where the batteries are stored. They will last 10 years.  And 1-100ah battery is like having 2-100AH lead acid batteries. 

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