# Need a solar expert!!



## CrawDaddy (Aug 10, 2014)

I need some help with designing a solar energy system. I need someone who knows his or her stuff on the matter and willing to point me in the right direction. I have tried several forums but they always fall into a conversation about power consumption conservation and never address what I really want to know because they don't understand that that I want a system that can support certain amount of activity in a SHTF and has nothing to do with my current monthly average. Please help!


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## cowboyhermit (Nov 10, 2012)

There are books and companies that deal with this sort of thing. There are existing threads on this forum of example systems. Been busy myself lately so no guarantees but ask your questions and see how it goes, many here have knowledge of alternative energy systems of varying sizes.


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## CrawDaddy (Aug 10, 2014)

Alright I'll give it a shot, here is what I want to do. I want to build a portable box built on a trailer that contains a charging regulator batteries and converter. I want enough solar panels to run about 800Kwh per month to start out with but want to be able to add solar panels over time to accommodate campers probably to a maximum 2000-2500 kWh per month. 

How many solar panels and batteries for 800 kWh to start out with and big enough charge controller and converter to accommodate the expansion?

I also would like a recommendation of a company that would be best buy for your money.


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## CrawDaddy (Aug 10, 2014)

What I want to do is run some things in my house on it but we have a family camp where we have several campers as a bug out location and I would like to be able to unhook it from my house pack up the panels hook to the trailer and pull it to the camp and tie it to a box that powers the campers. I will let them buy panels that they can bring and they want have to bring anything else but the panels.


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## cowboyhermit (Nov 10, 2012)

Ok, so that is actually a pretty big system you are looking at.

First start with the energy production. 800kWh/month = 26kWh/day so, for context that is equivalent to a small inverter generator running with a good load 24/7, not a small amount of electricity by any means. 

Anyways, to generate 26 000 watts per day on average you will need to figure out the average hours of peak sun equivalent in your location. A modest estimate of 8hrs would require about 3250W of panels, this is without losses which can be minimized or not depending on many factors such as when power is consumed. I will break up my response...


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## cowboyhermit (Nov 10, 2012)

Oops, almost forgot to finish this.
I will say again, these figures don't account for losses and are very approximate, if you need exact numbers it will take more details, I also wouldn't trust myself to balance my chequebook atm so there's that too.

Battery bank sizing is an even more situation specific problem. About the minimum reasonable size of bank would be a full day of solar capacity. 26kwh @ 12V = 2166 Ah of battery storage. Simply divide that by the storage capacity per battery for a 12V, twice as much will be required if they are 6V. Somewhere around 20 typical batteries 

Now, if solar is the only power source and you need a relatively consistent amount of power, you will likely want more storage than that. It really depends on how consistent the weather is, how able one is to adjust power draw, etc;

As for sizing of other components, a system that large will require very large components and/or components running in parallel. Sizing them is relatively simple, simply determine max amperage/wattage and go from there.

Now, at the risk of repeating myself and others you have heard from, loads are certainly worth considering. I will only say this, that kind of wattage system could run 20 or so modern refrigerators, as a point of reference. 

Hope this helped in general, if you need more specifics then we will too.


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## Wellrounded (Sep 25, 2011)

That's a huge amount of power. What are you planning to run? Maybe start with a list of what you want to do and we can all talk through it. 

That's about what our farm uses when on 100% grid power, multiple freezers, pumping tonnes of water a day, dehydrators flat out, two fridges, commercial electric ovens, full workshop including welders plus more. On solar running essentials we can reduce use to about 5kWh/day max. plus an hour a day on average for the diesel generator to make life easy.

Edited to add: By essentials I mean everything we need and a lot of luxuries, we could cut this down A LOT MORE if needed in a SHTF situation.


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## Viking (Mar 16, 2009)

cowboyhermit said:


> Oops, almost forgot to finish this.
> I will say again, these figures don't account for losses and are very approximate, if you need exact numbers it will take more details, I also wouldn't trust myself to balance my chequebook atm so there's that too.
> 
> Battery bank sizing is an even more situation specific problem. About the minimum reasonable size of bank would be a full day of solar capacity. 26kwh @ 12V = 2166 Ah of battery storage. Simply divide that by the storage capacity per battery for a 12V, twice as much will be required if they are 6V. Somewhere around 20 typical batteries
> ...


20 six volt batteries such as the golf cart batteries I have will weigh in at least 1,100 pounds. Don't discount the idea of power conservation in figuring what you really want for a solar system, I'm pretty sure that most of us here that have serious solar systems have figured this factor when designing our systems, for example, I designed my system to take care of two refrigerators, a chest freezer and minimal lighting. I do have 20 six volt batteries running series/parallel for 24 volts @ 1,025 amp hours. I have eight 195 watt solar panels for charging the batteries, total watts 1560 and that's if I get perfect sun days. So the reality is that you need to sit down and figure your total power consumption needs. There are solar web sites that have forms that you can input the wattage of all the things you want to run and they can give you a figure of watts for solar panels and amp hours needed for the battery bank. Or post them on this thread and there are people here that I'm sure can give you some solid figures. At this point our system has feed through from the grid and at this time it's only for emergency standby, for permanent off grid, such as after SHTF, our electrical lifestyle would alter drastically and if we were to run everything on solar as we do now on grid power I would have to triple the battery bank and solar panels and add two more solar charge controllers and two more inverters. The inverter we bought is stackable up to four so that can be done, however, at this point our finances make that a no go. The manual I got with the Inverter/charger we bought for our solar backup system had a page for doing those figures. Are you talking about a trailer just for a solar system? The reason I ask this is that with those kind of power requirements a large multiple axle trailer would be needed to carry the weight of all the batteries and panels as well as being long enough for the solar array.


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## Marcus (May 13, 2012)

Viking said:


> Are you talking about a trailer just for a solar system? The reason I ask this is that with those kind of power requirements a large multiple axle trailer would be needed to carry the weight of all the batteries and panels as well as being long enough for the solar array.


When I first read what the OP wanted, I thought a 16' or 20' flatbed trailer was probably going to be needed. You're probably going to need a full sized truck to pull it.

Figuring 16 200W panels (39" wide) double-stacked (I'll get to that in a moment), that raises the trailer length to 26'. If you choose to go with 345W high-end panels (41" wide), it'll take at least 12 of them. Again assuming a double stack configuration, that drops the required trailer length down to 20.5'

The other variable you need to know is peak sun hours which is a number that describes how much power you'll generate on an average day at a given location. The NREL has this data: http://www.nrel.gov/gis/solar.html

I cheated a little bit since I found a website that uses approximately the size system you're wanting. http://www.lightsonsolar.com/solar-basics-kw-and-kwh/

Depending on your location and its peak sun hours, you will have to adjust the size of your system up or down. I would also suggest a healthy 20% overcapacity so you'll have a wider range of travel possibilities.

You're also going to want to build a rack for the panels on the trailer. The rack should be adjustable so you can change the incline depending on the time of year so as to maximize your energy production. I would also figure on making a fold down top rack just to keep the trailer length reasonable and the height of your panels reasonable during travels since panels are 61-65" tall. That rack is also going to need a turntable so the panels can follow the sun to again maximize energy production. To keep from tipping over or tearing up the trailer and to distribute the weight of the rack and panels, you'll probably need outriggers at each corner along with base plates. You're also going to need at least one winch to turn the turntable and to raise the top rack using a removable pole. To give you an idea of how I see the rack, think of a glass truck with its A frame. Only one side will be hoisted up. You'll also need poles to support the top rack since any kind of pin will shear in enough wind. Wind will also have to be considered in design of the rack and will make outriggers necessary since you'll have a 10' high and 20' long sail.

I'd guesstimate you're looking at close to $10K for the trailer, rack, and outriggers assuming you can build it all yourself. Then the actual solar system itself would be on top of that. You may also find that the trailer frame will need to be strengthened to deal with the weight of the rack and panels.

It might be easier to find a surplus Army radar trailer and start from that.


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## CrawDaddy (Aug 10, 2014)

Actually close to what I had in mind but I never intended to have the rack mounted on the trailer but to have a rack I could easily tear down pack onto the trailer and set up somewhere else.


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## CrawDaddy (Aug 10, 2014)

I think I could just get one of these and mount hardware and battery banks in here. I wouldn't have to build the box and it would be large enough to pack panels into.


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## CrawDaddy (Aug 10, 2014)

A rack similar to this maybe


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## Marcus (May 13, 2012)

Okay, that makes a lot more sense. I was scratching my head about why it had to be trailer mounted since that seemed to be a huge unnecessary expense.

A Wells Fargo type trailer or even an equipment trailer is good. I'd look for something with some small access doors in front so the charge controllers, inverters, and batteries stay inside the trailer. The idea is to make it almost plug and play so all you have to remove are your cables, panels, and racks. One access door could be for the cables to your panels and the other could be for the plugs for the AC out. With all the batteries you'll need, you'll probably want to put them over the axle. That will mean some sort of box that you can walk on to get to the front of the trailer and yet still have access to the batteries for servicing.

You're going to want to give a lot of thought to the order you will use in loading and unloading the rack and panels. I'd put the panels in a heavily padded rack in the front of the trailer, and the vertical outside panel rack pieces in the back. As far as your outside rack, you're going to want it to be easily assembled in a hurry since daylight will literally mean lost energy. Rather than bolts and nuts, I suggest using drop in pins like is used in scaffolding. Of course, you'll want the vertical legs to be adjustable for uneven ground.


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## CrawDaddy (Aug 10, 2014)

Is there a company you can suggest to purchase panels and hardware from? Best bang for the buck deal.


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## Viking (Mar 16, 2009)

CrawDaddy said:


> Is there a company you can suggest to purchase panels and hardware from? Best bang for the buck deal.


I got my panels and solar controller from Grape Solar in Eugene, Oregon because they were just over 100 miles away and it saved over $200 in shipping. Look for solar equipment suppliers close to where you live because shipping can add hundreds of dollars. We also bought our inverter/charger in the Eugene area from Don Rowe, they handle all kinds of inverters and are far less expensive than an RV supplier, which is where we first checked out inverters. By going to these suppliers we probably saved around $1,000 in shipping and getting things at discounts. It pays to do the research on suppliers. Grape Solar supplies Costco, Home Depot and other big box stores with solar kits, but we found it best to deal directly with them. When they have the solar panels we want in stock they can be purchased in smaller numbers, if the panels are not in stock they have to be bought by the pallet, so this is something to also check out when dealing with suppliers.


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## Viking (Mar 16, 2009)

In considering carrying the solar system on a trailer I would rather have the panels on a foldup system, there is a lot of time and effort into attaching them to array frames and wiring. Part of the frame system could be used to enclose the array when in transport, just a thought.


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## mosquitomountainman (Jan 25, 2010)

Just from an expediency standpoint why not just have each camper/trailer set up their own solar power system?

Also, how do you plan on metering out power to several different locations (campers)? How do you plan on keeping some from using too much and depriving others. One of the first things a person on solar must do is adapt to using less power. It's hard to go from grid power to solar because people are used to unlimited power from the grid and it just doesn't work that way on solar.


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## CrawDaddy (Aug 10, 2014)

While those are some valid points that's kind of why I was wanting an overpowered system. ACs are a must so I was figuring everyone's AC usage would be about the same we will have one building for cooking and congregating during the day so AC only in one building during the day. And AC use during the night. The one building with the AC will have an icebox and a few deep freezers so those will be on all the time. None in the campers will be used or on. All campers will run only AC, fan, and a few lights.


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## CrawDaddy (Aug 10, 2014)

mosquitomountainman said:


> Just from an expediency standpoint why not just have each camper/trailer set up their own solar power system?


Well this is just idea and mostly I want to see if it's even feasible. The reason for not equipping each camper individually is because I want add the system to my house to assist my grid power. I use quite a bit of power and not really willing to sacrifice anything while I don't have to. I can't get to big for this. Whatever I start with will be used. I want it portable as possible because in a SHTF my whole family will go to our camp and I want to be able to supply that power to the camp. Having it upgradable just gives everyone the chance to just buy panels my thinking is since I'm already going to be purchasing the hardware it would be cheaper to buy them oversized and if I wanted I could add panels later vs having to buy more hardware. I could be wrong about that. That's why I'm here.


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## Marcus (May 13, 2012)

How secure is your campsite? I ask since it might be better to build a rack there instead of packing everything into a trailer.
Once you move to your campsite, do you intend to stay there for quite a while or will you move around a lot? That impacts how portable the whole system must be. You're also going to want to weatherproof the cabling and probably create extra cable sets. If you planning on only moving once to the camp and perhaps once back, I would make an extra cable set plus some replacements and leave the ones at your home in place in case you ever return.

Rather than investing a lot of capacity in powering AC units, I suggest building capacity for freezers to make ice. You can always make those 5 gallon AC units that run off of ice and a small fan. Advantages of doing it this way is those ice has many other uses including barter, and those 5 gallon AC units are easy to make.

I would also look at making most of your rack for your campsite out of wood and store it at the building(?) that's already there.

To get better advice, tell us a bit more about your campsite and how close the cabins(?) RVs(?) are to each other.

One of the issues you may have is long runs of wire *require* very expensive cabling. The amperage (service) will determine how heavy of cable you will need. You may be better off investing in extra batteries and a cart/wagon or three to haul them around. Lowe's sells 2-2-2-4 cable (130A/600V capacity) for $7.45/ft so 5 RVs 100' from the AC source is $3700 just for power distribution cabling. That cabling will need to be protected which generally means burying it in PVC. The size of the cable will determine the size of the PVC pipe.


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## mosquitomountainman (Jan 25, 2010)

Just another point to consider: if you are not tracking the sun (your panels are stationary) figure a maximum solar panel output of five hours per day. That means you must create enough power from your panels in five hours to completely recharge your battery bank and power everything you are using during the day at the same time ... with five hours of charging time.

Also you need to figure in cloudy days and have battery reserves to last at least three days of no sun. After those three days of discharging your battery bank can you completey recharge it with one full (five hour) day of sun?

If your battery back-up is not large enough to power you for three days then you'll be cutting battery life drastically because batteries have only a limited number of times that they can be drawn down completely then recharged. The deeper the draw-down, the more harm to your battery life. Thus the three day reserve is a minumum amount for longer battery life.

Remembr too that for every 100 amps used from a battery it will take 125 amps to restore it to it's previous state of charge.

On mobile unit, weight must also be considered ... batteries are heavy.


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## Caribou (Aug 18, 2012)

Using your U-Haul trailer idea as a starting point, how about mounting the panels to the side of the trailer and hinged at the top. Additional panels can be mounted on top and hinged so as to collect from the same side as the other panels. Still more panels can hinge off the front and rear. If more panels are required these can be stored in the trailer for moving. Batteries and controls can be mounted inside. This would give you a system that is quickly moved and will gain some power in transit.


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## CrawDaddy (Aug 10, 2014)

Well my only concern with hanging panels on the side is they could get damaged now if I could build a henge rack system and mount a row of panels on a solid frame then slide that whole row into the rack I think that may work nicely.


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## Cotton (Oct 12, 2013)

mosquitomountainman said:


> Just another point to consider:


So I thought I'd consider one... I ordered a hard copy of your book tonight...  (since Grimm gave it a good recommendation). I played around with solar 12 years ago... was looking for updated information. (heavy background in electronics/electricity, missile systems/catscans/mri's). I stepped off the technology train 15 years ago... I hope your book can bring me up to date!


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