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 > Solar Panels

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Alex and Tee

Jacksonville , FL

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Posted: 05/27/21 07:48am Link  |  Quote  |  Print  |  Notify Moderator

Our new motorhome has a 7.0 kw generator. I imagine to run all appliances A/C, refrigerator, tv's, lights, etc. it would take much less than 7.0 kw as not everything is on at the same time. We declined the solar panel option as I don't think 2 solar panels would run the A/C during a 115 degree AZ summer.

This leads to my question. We are thinking about buying a couple of acres in the Tucson area to use as a home base. We are going to build a covered, open sided car port with storage shed and concrete floor about 35' x 40'. It will be big enough to park our rig with slides out and room for patio furniture. It will likely be inaccessible to public power so we will have to install solar panels. How many kw should I plan to be able to generate? Should I just match the 7kw generator? Will also have to install a septic system so we don't have to dump tanks every few days and also install a water tank.

Thanks in advance for your insight!


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FloridaRosebud

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Posted: 05/27/21 08:03am Link  |  Quote  |  Print  |  Notify Moderator

Well then, everything changes based on your specific application. Residential solar cells come in larger panels, so it's easier to get the amount of power you'll need. So the big question actually is battery storage. There are days when the sun doesn't shine there (not too many) and obviously you will have no solar generation at night. AFA panels, 6KW should work to keep a battery bank charged and run 2 A/C units. You will need enough battery capacity to get you through the night minimum. I would seriously consider hiring an engineer who has training in this area to put a system together for you. I'm in Florida (I'm an EE with training in this area) so I'm too far away and I don't do design projects. Just a warning - it will not be cheap.

Al

way2roll

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Posted: 05/27/21 08:26am Link  |  Quote  |  Print  |  Notify Moderator

The solar panels on RV's aren't meant to drive AC appliances like your AC and microwave etc. They are meant to keep your batteries charged to run your 12V systems (lights, controls, inverter for fridge..). Solar panels are great to have because without shore power or the gen set to charge your batteries, there is no way to keep them topped off.

You may want to try and better understand your RV's electrical systems. Specifically 12V vs 120. There are a lot of things that run on a coach that are 12V only. Lights, controls, water pump etc. The 120 items like your AC and microwave require being plugged in to shore power, or in the absence of shore power - that is why you have an onboard power plant - your genset. We used to run our AC while going down the road - for example or use the microwave when stopping for lunch. These things don't run on batteries.


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dodge guy

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Posted: 05/27/21 09:32am Link  |  Quote  |  Print  |  Notify Moderator

You would need a very costly solar system with batteries and inverter to be able to run the RV as if it was plugged into 110V 50A power. For example a 400W system would allow you to run a residential fridge and some appliances when not plugged in.

You may want to do some research on RV solar power.


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fyrflie

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Posted: 05/27/21 09:35am Link  |  Quote  |  Print  |  Notify Moderator

https://www.parkedinparadise.com/solar-calculator/
This is just one of multiple places to look to answer your question.

But, rather than build a system just for the RV, why not look into building a true off-grid power system.

Alex and Tee

Jacksonville , FL

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Posted: 05/27/21 09:50am Link  |  Quote  |  Print  |  Notify Moderator

The plan is to build an off the grid system and use that as my “shore” hook up when there. What I’m trying to determine is what size that system should be. I don’t know how much power the rig would consume considering running two A/C units, fridge, lights and tv’s.

jdc1

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Posted: 05/27/21 09:51am Link  |  Quote  |  Print  |  Notify Moderator

Why not use propane for the refigerator? A 100 gallon tank will last you years. Then, the only thing you need to power up is the AC. I doubt you'll be out there in June through October, when it's 110*+.

Alex and Tee

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Posted: 05/27/21 10:05am Link  |  Quote  |  Print  |  Notify Moderator

Perhaps I will look at LP powered generators as well. A 10kw is about $3000 and consumes about 1 gal per hour at half load. A 1000 gal LP tank is about $2500.

valhalla360

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Posted: 05/27/21 10:20am Link  |  Quote  |  Print  |  Notify Moderator

Assuming 2 air/con units running flat out in Arizona heat...let's say 3kw constant demand (24/7).

That means you need a total of 72kwh generated per day.

Solar panels don't generate their rated output 24/7. A good estimate is 4 times the ratted kilowatts (1000 watts) in killowatt hours. So, you are looking at around 18kw of solar panels...call it 20kw since you will lose some power converting it to battery storage and back again.

Now you need something to store those slippery electrons or they just fly away. That means a battery bank. So if we figure around 2pm, the 20kw of solar panels is putting out less than what you are using and doesn't pick up to that level again until 10am the next morning, you need to cover 20hr of use at 3kw or storage of about 60kwh.
- Traditional lead-acid batteries, you don't want to use more than 50% of the available power, so you will need around 120kwh of batteries.
- Lithium are expensive but you can use 80% without worry, so you need about 75kwh of batteries (just shy of what a Tesla has).

So now you have a way to generate power and a way to store it...but it's stored as DC power. You need a way to convert that to AC power which means an inverter. Well if it you are pulling 3000w, just get an 3000w inverter...except no, 3000w is the continuous draw once the air/con compressors are turning. To start those compressor motors takes 3-4 times the power. If you are careful (or add a device that only allows one to start up at a time, you may see 1500w + 1500w *4 or about 7500w momentarily. You need to buy an inverter that can handle a start up load of 7500w (often it's difficult to find the continous vs startup rating on inverters).

So you are looking at a very large solar array, very large battery array and a large inverter charger...realistically, it will be cheaper to maintain and fuel your existing 7kw generator. Even if you have to replace it every 8-10yrs.


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MountainAir05

New Mexico

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Posted: 05/27/21 10:21am Link  |  Quote  |  Print  |  Notify Moderator

LP system out this way are not cheap, and the LP is running above the price of Premium fuel right now. We just had a friend switch out from LP to to total electrical due to the cost of LP for heat and hot water heater and stove. They went thru the winter and came out ahead on cost and the house was still warm. Plenty of shops in Phoenix area that do this and they are good at it.

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