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Old 08-23-2017, 04:48 PM   #1
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Solar System Size

Looks like I will be living off grind for while. So I was wondering what kind of system I would need to keep my bus going. I am trying to learn but it's a lot of info to soak in!

I have a 110V fridge and chest freezer that claim to use 43KWH a month (together) or 1.4KWH a day so that's what 1400 watts a day? Past that I will be using two laptop computers a 32" LED TV I have (10) 110V LED lights with maybe three or four on at a given time microwave for maybe 15-20 mins a day (ya I don't cook) and toast coffee pot. I have AC's but that will be wired straight to the gen set.

So my plan was 6 130AH for a total of 780ah lead acid battery and maybe an 800W solar kit with a 4000w pure sign wave inverter. My question is will that be enough power to keep me going overnight and recharge in the morning and power everything? I will be in southern new mexico so the sun will be strong.
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Old 08-23-2017, 04:58 PM   #2
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Living off grind can be a real grid sometimes. And, the solar system is really, really big.

Sorry; I had to. Welcome!
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Old 08-23-2017, 05:10 PM   #3
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The electrical terms for measuring storage and utilization can get confusing. You've got them confused.

Watt Hours is ultimately the unit of measurement that you should be working towards. A watt is a unit of work and that unit of work over a period of time (hour) is how you measure capacity or drain.

In my bus, I have 400W of solar panels. In a perfect world, I'm getting 400 watts for 12 hours a day. You can call that 4.8 kilowatt hours.

Your batteries will be rated in Amp Hours. This might make sense for them because the voltage changes based on several factors, unfortunately you still need to work it to watt hours to have numbers that you can translate back and forth. My freezer at full steam consumes about 100 watts, but I only run it about half an hour a day, so we'd say it uses about 50 watt hours.

Ultimately I recommend you use a Kill-A-Watt meter to measure actual power draw on the things you want to plug in: http://amzn.to/2wpnMhe

Maybe more importantly, anything that you can run from DC, you should run from DC. THat means laptop chargers, mobile device chargers, etc. You lose at least 15% of your power when using an inverter to drive something.

Remember that Volts * Amps = Watts, which also means that Watts / Volts = Amps and Watts / Amps = Volts and etc. Get all your power figures into directly comparable values and it's basic math.. Power in vs Power out.
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Old 08-23-2017, 05:16 PM   #4
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You will want to size your solar to meet your needs with some "headroom" on the shortest days of the year.

Look at a "solar insulation map" to determine the number of hours of usable sunlight during the Winter. https://www.wholesalesolar.com/solar...n-hours-us-map

Then determine what your total daily load is and divide load/hours then account for system losses and you will get a MINIMUM system size. To assist with load calculation take a look at: https://www.solar-electric.com/solar/calc/

If you want to be able to have power over the course of a few cloudy days then you will need to add battery capacity and additional solar capacity to accomodate.

I would recommend that you start reading here: https://handybobsolar.wordpress.com/

Then take a look at: Northern Arizona Wind & Sun Solar Forum
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Old 08-24-2017, 12:36 PM   #5
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Check out Home Depot. I got my unit there.
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Old 08-25-2017, 06:55 AM   #6
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Originally Posted by brokedown View Post
The electrical terms for measuring storage and utilization can get confusing. You've got them confused.
Excellent post brokedown!!

bigskypc50, an 'energy budget' is the common term for what you are doing. I've posted mine a couple of times but remember that it is different for every person, coach, location, etc... These may give you some ideas:
Dutch Star Energy Audit - JdFinley.com
Energy Audit - Watt For? - JdFinley.com

Solar is AMAZING and I love it! However; there is a bit of a curve to learning to make it work for you.
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Old 08-25-2017, 11:10 AM   #7
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You first calculate what your needs are, then how much battery capacity is needed for two or three days if the sun is not cooperating, then how many amps are needed to fully recharge them every day at between 5 and 13% charge rate. Or just carpet your whole darn roof with panels - the more the better! I have 2kW of tiltable panels, two 60-amp charge controllers and eventually eight golfcart batteries, and my goal is to be completely self-sufficient for electricity from the sun, or at least for the next 5 billion years or so.

As I have mentioned previously here, the good folk at the NAWS forum know more about such matters than us busnuts will ever need to know, so heed their advice. It's well worth your time to read through some of the threads there.

John
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Old 08-25-2017, 11:31 AM   #8
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That's a crazy amount of solar. We have extra with 400 watts.

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Old 08-25-2017, 11:41 AM   #9
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Quote:
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That's a crazy amount of solar. We have extra with 400 watts.
I don't think there is such a thing as "too much solar" (as in 'crazy amount') when you depend on it for all of your electricity.

I've been living that way for better than three years. Of course, I have a power hungry coach - I understand that.

Something more to consider... With flat mounted panels, I've found that 80% of rated panel output during the summer months can be expected. However; only about 55%-60% during the winter months (in the southwest). Toss in shading due to mountains and clouds (during the winter months) and there is sometimes a limited amount of time to harness as much power as possible. If every day had a sun straight up in the sky and it stayed there for ten hours, things would be different. So, for those of us living on solar full-time, please understand that 2kw is typically not what is required to survive every great summer day - it is what is required to survive every not-so-great winter day.

Obviously, tilting panels would help the above numbers...
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Old 08-26-2017, 03:18 AM   #10
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Check out Home Depot. I got my unit there.
Which one did you get at HD? I'd love to check that out. And what are you running on it? Solar is the way to go!!

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