Solar design for off grid tiny trailer house

tydaddy

Hello all! This is my first post, although, I've been trying to read as much as possible lately. I'm learning, however, it seems the possibilities are endless when it comes to system design, and without having any experience, I figured I'd see what suggestions you all have.

I'm in the planning stages of building a tiny trailer house, which when done will be about 300 sq ft, not including loft space. My thought is to use the roof ~300 sq ft for the panels. I'm in the process of figuring out creative mounting options, as they will be subjected to high winds when traveling, but I digress.

I've looked at my needs (read: wants), as we're not trying to live frugally, just simply disconnected and more simply, while still having the luxuries we want. Anyhow, it seems as though in the spring/fall, we'd only need about 5 kwh/day, but winter/summer while using a mini split for a few hours a day it might go up to 9ish. To be safe, and because I think (by my calculations) have the space for the panels, I'd plan on 12kwh/day.

That said, it seems that the Canadian Solar CS6X-280P provide the most bang per buck, and have relatively good reviews. With the estimation I've done, I could get by with 16-18 panels.

Anyhow, I'm just not sure which components - inverter, batteries, etc., and the most efficient design to build. Obviously, I want maximize my production, because I'd rather have more than needed than not enough.

Also, I was wondering if it would be possible to set it up as an off grid system, however, if move somewhere in the future that has a power pole, would it be possible to tie into the system without the need for upgraded components.

I realize this is a somewhat obscure post, but as I said, I'm in the design process, and looking at the logistics while at the same time, trying to learn as much as possible as I'd like to do all of the work myself. I guess I'm sort of asking you to pair me up some components that will work well with the aforementioned panels!

Thanks for any and all suggestions!

Cariboocoot

Re: Solar design for off grid tiny trailer house

Welcome to the forum.

My first suggestion would be to re-evaluate the term "frugally" in respect to power consumption. 12kW hours per day isn't in it.

If you take that figure and do a simple end-to-end calculation you get about 5800 Watts of panel. Might be a little tricky fitting that into 300 square feet of space even with monocrystaline panels.

My second suggestion is buy a Kill-A-Watt meter and start measuring what you use now so that you get a realistic idea of consumption. Pay particular attention to items that use electric for heat, as they are bad news. Some things may be replaced with more efficient equivalent.

Once you have that daily power use number whittled down (we use about 2-3 kW hours per day at the cabin) and know the maximum amount of Watts they may be used at one time and whether or not you'll need 240 VAC (both for picking inverter) the rest is easy. Relatively.

At that point you're choosing batteries, and then the solar panels & charge controller. The batteries run the inverter and supply the power. The panels recharge the batteries.

SolarPowered

Re: Solar design for off grid tiny trailer house

tydaddy wrote: »

I'm learning, however, it seems the possibilities are endless when it comes to system design, and without having any experience, I figured I'd see what suggestions you all have.

Don't believe everything you read and until you've read through the entire 2011 NEC don't try to tell any one its easy or you understand it.

We are here to help, possibilities aren't endless though look at all the failures of collapsed structures. Those are the people that thought possibilities were endless. LOL

tydaddy wrote: »

I'm in the planning stages of building a tiny trailer house, which when done will be about 300 sq ft, not including loft space. My thought is to use the roof ~300 sq ft for the panels. I'm in the process of figuring out creative mounting options, as they will be subjected to high winds when traveling, but I digress.

I've looked at my needs (read: wants), as we're not trying to live frugally, just simply disconnected and more simply, while still having the luxuries we want. Anyhow, it seems as though in the spring/fall, we'd only need about 5 kwh/day, but winter/summer while using a mini split for a few hours a day it might go up to 9ish. To be safe, and because I think (by my calculations) have the space for the panels, I'd plan on 12kwh/day.

That said, it seems that the Canadian Solar CS6X-280P provide the most bang per buck, and have relatively good reviews. With the estimation I've done, I could get by with 16-18 panels.

The canadian solar CS6X-280P is out of the question. You are just merly looking at pricing before engineering and design. Poly crystalline has its high points.... It's cheap, so cheap that its good for people tht own acres of real estate for solar farms, however we are having a discussion of 300sq/ft.

You said you are using 300sq/ft, you need higher conversion efficiency in a tighter use of real estate. You will want to look into the canadian solar CS6P-265MM, or the the solar world sunmodule 275M .
Better conversion efficiency and something tells me the panel will be installed flat at 0 ~5* tilt, which means you will want the lower light radiation levels that mono crystalline converts electricity to..

http://www.canadiansolar.com/down/en/ELPS_CS6P-MM_en.pdf
http://www.solarworld-usa.com/~/media/www/files/datasheets/sunmodule-plus/sunmodule-solar-panel-275-mono-ds.pdf

Kindest Regards

tydaddy

Re: Solar design for off grid tiny trailer house

Cariboocoot wrote: »

Welcome to the forum.

My first suggestion would be to re-evaluate the term "frugally" in respect to power consumption. 12kW hours per day isn't in it.
I said NOT trying to live frugally

If you take that figure and do a simple end-to-end calculation you get about 5800 Watts of panel. Might be a little tricky fitting that into 300 square feet of space even with monocrystaline panels.

There are ways to make exceptions. It won't be a simple flat roof, so that I can maximize square footage, then adjust the rows of panels according to our latitude and time of year.

My second suggestion is buy a Kill-A-Watt meter and start measuring what you use now so that you get a realistic idea of consumption. Pay particular attention to items that use electric for heat, as they are bad news. Some things may be replaced with more efficient equivalent.
What we use now is pointless, as it's about 75kwh per day ~2200 per month. Old house, terrible insulation, lots of issues. Regardless, we will be buying all new energy star appliances, pretty much best rated in each category for our build.

Once you have that daily power use number whittled down (we use about 2-3 kW
hours per day at the cabin) and know the maximum amount of Watts they may be used at one time and whether or not you'll need 240 VAC (both for picking inverter) the rest is easy. Relatively.
I've got a spreadsheet with all of that stuff listed. As I said, it will be between 5-8 kwh per day, but I want plenty of room to grow.

At that point you're choosing batteries, and then the solar panels & charge controller. The batteries run the inverter and supply the power. The panels recharge the batteries.
When dealing with finite square footage to place panels, isn't it best to figure out the max amount you can produce, then scale back usage based on production? With a built from ground tiny house, clearly many of our energy habits (bad)/needs will change based on the availability...

Thanks again for the quick reply!

tydaddy

Re: Solar design for off grid tiny trailer house

SolarPowered wrote: »

Don't believe everything you read and until you've read through the entire 2011 NEC don't try to tell any one its easy or you understand it.

We are here to help, possibilities aren't endless though look at all the failures of collapsed structures. Those are the people that thought possibilities were endless. LOL
Simply meant the possibilities were endless as far as putting components together...and it's a tad bit overwhelming trying to figure out how to design an efficient system. I did order the NEC book, and a guide to the NEC last week, so that should help...or will probably just confuse me more :-)


The canadian solar CS6X-280P is out of the question. You are just merly looking at pricing before engineering and design. Poly crystalline has its high points.... It's cheap, so cheap that its good for people tht own acres of real estate for solar farms, however we are having a discussion of 300sq/ft.

You said you are using 300sq/ft, you need higher conversion efficiency in a tighter use of real estate. You will want to look into the canadian solar CS6P-265MM, or the the solar world sunmodule 275M .
Better conversion efficiency and something tells me the panel will be installed flat at 0 ~5* tilt, which means you will want the lower light radiation levels that mono crystalline converts electricity to..They will be mounted to be adjusted at proper tilt throughout the year. When searching for reviews and "best solar panel for the buck" the canadian solar kept popping up - the only reason I considered using them. Again, I joined this forum to get guidance from you all who are much more versed than myself!

http://www.canadiansolar.com/down/en/ELPS_CS6P-MM_en.pdf
http://www.solarworld-usa.com/~/media/www/files/datasheets/sunmodule-plus/sunmodule-solar-panel-275-mono-ds.pdf

Kindest Regards

Appreciate the input!

SolarPowered

Re: Solar design for off grid tiny trailer house

If the NEC hurts your head on comprehension.
There are options, like the UGLY's handbook.

They have them at home depot, and if you don't have a home depot where you live its also on amazon.com

Here is a link to the 2014 edition.

http://www.amazon.com/Uglys-Electrical-References-2014-Edition/dp/1449690777/ref=sr_1_1?ie=UTF8&qid=1393210378&sr=8-1&keywords=ugly%27s+electrical+reference

Kindest Regards

Cariboocoot

Re: Solar design for off grid tiny trailer house

Nevertheless, 12kW hours per day is not that easy to supply from a small area. Physics will limit this one way or another.

What you use now is not pointless, as you may not realize just what usage patterns are driving the numbers up. Off-grid electric comes at a big per kW hour price, so the smaller you can make the system the better.

Spreadsheet usage data is notoriously inaccurate because it is based on the science-fiction of manufacturer-supplied numbers. Comparing these supposed Watt hours to ones actually measured has proven to be quite interesting for many people. Sometimes it's less, sometimes it's more.

If you want to design from the maximum array size back and limit your available power to that it can be done. But you may find those limitations frustrating and find you're running a generator all too often.

If you can fit sixteen 280 Watt panels that gives you 4,480 Watts. By the same end-to-end calculation that would be 9kW hours, based on a minimum 4 hours equivalent good sun. About 4kW hours short of your expectations. You would get enough from that for about 720 Amp hours @ 48 Volts, which at 25% DOD would yield about 8.6 kW hours - in the right 'neighbourhood' of the panel harvest.

SolarPowered

Re: Solar design for off grid tiny trailer house

The never ending battle of peukerts law, and temperature issues also show losses that really limit solar off grid to roughly 60% efficiency at best. Then at best it would have to be the most absolute perfect day ever to achieve a stored and retained 12kWh.

The only way I've seen efficiency be achieved close to grid efficiency is through Li-Ion off grid systems, byt then it goes far out side the realm of reasonable costs, when comparing to the cost of grid parity.

Realistically to achieve a 12kWh stored charge plus normal usage without reducing DOD and killing the life of the battery, and fighting lower solar radiation levels in dead of winter (unless you lived close to the equator), or fighting the temperature losses during the summer 7kWh of panels is what is needed to live comfortable on a 12kWh stored battery system. You have to think just 3 days of cloud cover is going to cause havoc on the battery and its life cycle, not every day is a sunny day.

smatthew

Re: Solar design for off grid tiny trailer house

What kind of "Tiny Trailer House" are you planning on? 5th wheel, box truck, bus, etc?

BB.

Re: Solar design for off grid tiny trailer house

Just to give you some ideas--

• 1 kWH per day for lights, laptop computer, charging cell phone, small water pump to pressurize.
• 3.3 kWH per day--Add refrigerator, washing machine, and well pump. Can live an "almost normal" electric appliance life.
• 10 kWH per day--A natural gas fueled home (cooking, hot water, heating) with microwave, multiple refrigerators, freezer, normal life.

Add electric stove, heating, A/C -- And your power usage goes way up.

A 3.3 kWH per day system would look like (nominal design rules),

• 3,300 WH per day * 1/0.85 inverter eff * 1/24 volt battery bank * 2 days storage * 1/0.50 discharge = 621 AH battery bank @ 24 volts

Or around 12 "golf cart 6 volt @ 220 AH batteries (not a small bank).

And then the solar array needed to charge a 621 AH @ 24 volt battery bank:

• 621 AH * 29 volts charging * 1/0.77 panel+controller losses * 0.10 rate of charge = 2,339 Watt array nominal (based on battery bank size)

And the amount of panels to meet your minimum needs 9+ months of the year. In a sunny climate, you are looking at ~4 hours of sun per day for 9+ months a year (use generator for winter/poor weather battery recharging/support):

• 3,300 WH * 1/0.52 system efficiency * 1/4 hours of sun per day = 1,587 Watt array minimum (based on loads+amount of sun).

Add a ~80 Amp MPPT charge controller, a ~1-2 kWH True Sine Wave AC inverter. A genset plus AC battery charger (for backup).

This is "nominal" design system. Can adjust battery/array/inverter/etc. sizes a bit--But this is a good starting estimate/system.

So, that is the suggested system for just 3.3 kWH per day... You want 12 kWH per day--Make it 4x larger.

-Bill

SolarPowered

Re: Solar design for off grid tiny trailer house

O.K quick math.
OP wanted to get CS6X-280P dimension 6.41X3.23= 20.7 divide 300/20.70= 14 panels total 280X14= 3920 DC watts

or my suggestion CS6P-265MM dimension 5.38X3.23=17.37 divide 300/17.37= 17 panels total 265X17=4505 DC watts

The only way that would get better per real estate is by purchasing sunpower 435 panels which you can only get through commercial PPA agreements so thats out of the question. Then there is the spr-327

17 panels total per real estate 327X17= 5559 DC watts. Sunpower is out of the question because they void warranty if it isn't installed by an authorized contractor and they sell on average for $1.60 per watt, its like the lamborgini of solar and it still can't make enough power per real estate for what is needed.

Cariboocoot

Re: Solar design for off grid tiny trailer house

And if we take the math a little further with the two panel examples that are available we get a choice of about 8kW hours per day or 9kW hours per day. Both fall short of the 12kW hour goal.

As I've said so many times, start with the loads. Then when it works out you can't supply them, go back and do it again. In this case it would be a matter of adjusting lifestyle to fit the kW hours available. Frankly that is not impossible because even 8kW hours is quite a bit of power off-grid. Three times what we use, and we have no problem with that. Half what the in-town house uses, and it has an electric hot water heater and dryer (major power users).

Or why I say spreadsheet data is unreliable.

tydaddy

Re: Solar design for off grid tiny trailer house

smatthew wrote: »

What kind of "Tiny Trailer House" are you planning on? 5th wheel, box truck, bus, etc?

My current working design is based on a 30' gooseneck...obviously new prices are ~$7000, so the search for a used one in good shape has begun. Again, this is all in the infant stages so everything is quite dynamic.

tydaddy

Re: Solar design for off grid tiny trailer house

SolarPowered wrote: »

O.K quick math.
OP wanted to get CS6X-280P dimension 6.41X3.23= 20.7 divide 300/20.70= 14 panels total 280X14= 3920 DC watts

or my suggestion CS6P-265MM dimension 5.38X3.23=17.37 divide 300/17.37= 17 panels total 265X17=4505 DC watts

The only way that would get better per real estate is by purchasing sunpower 435 panels which you can only get through commercial PPA agreements so thats out of the question. Then there is the spr-327

17 panels total per real estate 327X17= 5559 DC watts. Sunpower is out of the question because they void warranty if it isn't installed by an authorized contractor and they sell on average for $1.60 per watt, its like the lamborgini of solar and it still can't make enough power per real estate for what is needed.

Again, by being creative with the roof design, I can get just about 400 sq ft. As I stated, this is all dynamic, and appreciate all of your input.

tydaddy

Re: Solar design for off grid tiny trailer house

BB. wrote: »

Just to give you some ideas--

• 1 kWH per day for lights, laptop computer, charging cell phone, small water pump to pressurize.
• 3.3 kWH per day--Add refrigerator, washing machine, and well pump. Can live an "almost normal" electric appliance life.
• 10 kWH per day--A natural gas fueled home (cooking, hot water, heating) with microwave, multiple refrigerators, freezer, normal life.

Add electric stove, heating, A/C -- And your power usage goes way up.

A 3.3 kWH per day system would look like (nominal design rules),

• 3,300 WH per day * 1/0.85 inverter eff * 1/24 volt battery bank * 2 days storage * 1/0.50 discharge = 621 AH battery bank @ 24 volts

Or around 12 "golf cart 6 volt @ 220 AH batteries (not a small bank).

And then the solar array needed to charge a 621 AH @ 24 volt battery bank:

• 621 AH * 29 volts charging * 1/0.77 panel+controller losses * 0.10 rate of charge = 2,339 Watt array nominal (based on battery bank size)

And the amount of panels to meet your minimum needs 9+ months of the year. In a sunny climate, you are looking at ~4 hours of sun per day for 9+ months a year (use generator for winter/poor weather battery recharging/support):

• 3,300 WH * 1/0.52 system efficiency * 1/4 hours of sun per day = 1,587 Watt array minimum (based on loads+amount of sun).

Add a ~80 Amp MPPT charge controller, a ~1-2 kWH True Sine Wave AC inverter. A genset plus AC battery charger (for backup).

This is "nominal" design system. Can adjust battery/array/inverter/etc. sizes a bit--But this is a good starting estimate/system.

So, that is the suggested system for just 3.3 kWH per day... You want 12 kWH per day--Make it 4x larger.

-Bill

Great information, and sort of similar to what I initially thought. Then I started to think "what if I wanted to add this...and this..." and the number ballooned from a minimal 5ish kwh, to 8...then I simply got nervous, so thought I should add more. Since I'm planning my system around the appliances we will need (again read: want) nothing is set in stone. Also, I want to avoid propane as much as possible... Obviously if I discover what I want to do simply isn't possible, with solar, then I'll start subtracting things that take a lot of power, and go the propane route with them (heating, cooking, hot water - although, I'm hoping a closed loop system with a 4x10 collector will work for water heating)

tydaddy

Re: Solar design for off grid tiny trailer house

Cariboocoot wrote: »

And if we take the math a little further with the two panel examples that are available we get a choice of about 8kW hours per day or 9kW hours per day. Both fall short of the 12kW hour goal.

As I've said so many times, start with the loads. Then when it works out you can't supply them, go back and do it again. In this case it would be a matter of adjusting lifestyle to fit the kW hours available. Frankly that is not impossible because even 8kW hours is quite a bit of power off-grid. Three times what we use, and we have no problem with that. Half what the in-town house uses, and it has an electric hot water heater and dryer (major power users).

Or why I say spreadsheet data is unreliable.

Understood. It's also why I can't go on my current usage - as no appliances will carry over. Our bill last month was for 2300 kwh!! I guess the difficult part is designing EVERYTHING from the ground up. Heating, cooling, cooking, comfort, entertainment. That is essentially what I meant when I stated unlimited possibilities. Again, I appreciate all of the input.

I guess I'm looking for "with your space, here is the best system configuration you can build for the money". I realize I'm asking a lot, so I apologize. I don't need the best of the best, obviously, I simply want something reliable, that will reliably produce at very minimum what we need, plus a bit extra so that we have a buffer. I realize this isn't the standard way to design a system, so I will end up building a larger system than "needed" and will pay more to do so. I'd also like the ability to connect to the grid, if we so choose.

Thanks again for being so helpful fellas!

SolarPowered

Re: Solar design for off grid tiny trailer house

So are you building a parking lot canopy, or a solar array on a roof?

I beam steal, sure you can get creative, UNIRAC, PV mount and all thiese other roof manufacturers only get you roughly 14" to 16" of cantilever, most of that is because of what is called live load or windsheer uplift.

Easy math, if you are using 300sq/ft and you build out for 400sq/ft no matter how you slice the pie thats 2.5' around the entire roof, or 5 ' on the top and bottom of that roof. I don't see according to code how any cantilever extended that far is legal for build. The most of this confusion is that its going to be mobile, how do you expect to go through tunnels? That would make it wider than a semi truck.

This is sounding more and more like imaginative design, using cheap panels that would never work, and the realism would of been is that it would of been more believable if you started talking about solar fold out concentrators rather than over hanging panels almost 5' of cantilever.

Just trying to say the realism isn't there.

Even if you did get that extra 100sq/ft by some blessed miracle and using mono crystalline you are only seeing an additional 1150 DC watts of power. Still not enough to your goal.

Cariboocoot

Re: Solar design for off grid tiny trailer house

A couple of things that should be considered: accessory array built external of the house, portable if needed (their are some RVer's who use such mobile arrays, setting them up at site) and a generator for when the solar falls flat.

That last one could be more helpful than you think, because it can power occasional large loads when needed which means you don't have to build the solar set up large enough to accommodate them. In fact most off-gridders have some variation on this theme up to and including automatic generator assist.

Otherwise if you must fit the maximum Watts in the minimum area your only choice is monocrystaline panels. They cost more per Watt, but that extra money buys a bit more power for the space they take up.

I think you're going to have to do several designs on paper and look at the trade-offs between space, complexity, power offered, and cost.

mike95490

Re: Solar design for off grid tiny trailer house

My off-grid house, rarely exceeds 8 KWh per day, unless I am baking bread or doing several loads of laundry. But air conditioning would easily double that, so we designed to avoid needing AC.

tydaddy

Re: Solar design for off grid tiny trailer house

SolarPowered wrote: »

So are you building a parking lot canopy, or a solar array on a roof?

I beam steal, sure you can get creative, UNIRAC, PV mount and all thiese other roof manufacturers only get you roughly 14" to 16" of cantilever, most of that is because of what is called live load or windsheer uplift.

Easy math, if you are using 300sq/ft and you build out for 400sq/ft no matter how you slice the pie thats 2.5' around the entire roof, or 5 ' on the top and bottom of that roof. I don't see according to code how any cantilever extended that far is legal for build. The most of this confusion is that its going to be mobile, how do you expect to go through tunnels? That would make it wider than a semi truck.

This is sounding more and more like imaginative design, using cheap panels that would never work, and the realism would of been is that it would of been more believable if you started talking about solar fold out concentrators rather than over hanging panels almost 5' of cantilever.

Just trying to say the realism isn't there.

Even if you did get that extra 100sq/ft by some blessed miracle and using mono crystalline you are only seeing an additional 1150 DC watts of power. Still not enough to your goal.

Again, playing with the numbers (I don't have my drawings in front of me), I can design a roof that has a minimal slope - a few inches over 6.5', at which point the slope becomes a the opposite, so almost 90 degrees for 6.5' down. Depending on the design, it could be anywhere from 30'-40' in length. When it comes to "code" - really - tiny trailer homes are illegal (well not mentioned in any code to date) anyhow, so this build, while it will be as "in code" with respect to high wind residential standards as possible, it will hardly be confined to what "code" allows. This would be the travel configuration. When parked, the panels could be adjusted for optimal sun angle. In theory, it would work. In practice - who knows!? For the umpteenth time, I'm not stuck on any one design, configuration, etc. Not sure why everyone else is! LOL. As stated previously, if it seems that I can only fit 12, or 14, or even 10 panels, then I will design based on that. It is after all why I appreciate all of the feedback!

SolarPowered

Re: Solar design for off grid tiny trailer house

tydaddy wrote: »

tiny trailer homes are illegal (well not mentioned in any code to date) anyhow, so this build, while it will be as "in code" with respect to high wind residential standards as possible, it will hardly be confined to what "code" allows. This would be the travel configuration. When parked, the panels could be adjusted for optimal sun angle. In theory, it would work. In practice - who knows!? For the umpteenth time, I'm not stuck on any one design, configuration, etc. Not sure why everyone else is! LOL. As stated previously, if it seems that I can only fit 12, or 14, or even 10 panels, then I will design based on that. It is after all why I appreciate all of the feedback!

I would just design around 17 mono-crystalline panels. I'm not going to recommend anything that can't fit structurally sound within the confines of the existing dimensional space.

As far as travel with a bus of any sort you also have to realize that the vehicle dimension has to remain under 14' in height for clearance, and the wide load can't exceed 7.5' wide, if its 30' long without a 5th wheel axle that dimension is smaller its 7' for wide turns.

Typical parking spaces and highway lane widths are 9' any wider or taller than that you can get a mobile violation for not meeting those constraints. You have to pull a permit for wide or tall load vehicles and your high way patrol has to assign you a path f travel from point A to point B.

Talking about seasonal tracking means no matter what, you are elevating the system to fit the mechanical racking components, then the issue with width, now its more of exceeding the weight of the actuators unless you buy a $2000 worm drive that has enough torque to move an array that large. I can also tell you for fact if you haven't looked at the spec sheet yet those poly crystallines you were looking at are 30% heavier than the mono crystalline, so its going to burn up any actuator you do invest in, if you stay with a poly design.

Your design and theory is getting expensive and unreasonable.

tydaddy

Re: Solar design for off grid tiny trailer house

SolarPowered wrote: »

I would just design around 17 mono-crystalline panels. I'm not going to recommend anything that can't fit structurally sound within the confines of the existing dimensional space.

Understood.

As far as travel with a bus of any sort you also have to realize that the vehicle dimension has to remain under 14' in height for clearance, and the wide load can't exceed 7.5' wide, if its 30' long without a 5th wheel axle that dimension is smaller its 7' for wide turns.

Typical parking spaces and highway lane widths are 9' any wider or taller than that you can get a mobile violation for not meeting those constraints. You have to pull a permit for wide or tall load vehicles and your high way patrol has to assign you a path f travel from point A to point B.
Max trailer height cannot exceed 13.5', and width cannot exceed 8.5' without needing a permit.

Talking about seasonal tracking means no matter what, you are elevating the system to fit the mechanical racking components, then the issue with width, now its more of exceeding the weight of the actuators unless you buy a $2000 worm drive that has enough torque to move an array that large.
If the array is built - say 2 strings of 8 panels each, with a custom mount, and manual (not mechanical) adjustment, really the only limit is the strength of the materials used to support such a load. 8 panels x 60# each, with mounting hardware, wouldn't be more than 600#, elevating one side, would be simple with 2 people.

Your design and theory is getting expensive and unreasonable.
Possibly, but then again, feedback is good, as it will allow me to push the design limits, and fine tune my design.

Good thoughts! Thanks!

tydaddy

Re: Solar design for off grid tiny trailer house

mike95490 wrote: »

My off-grid house, rarely exceeds 8 KWh per day, unless I am baking bread or doing several loads of laundry. But air conditioning would easily double that, so we designed to avoid needing AC.

I've factored supplemental heating/cooling in winter/summer with a minisplit. Without such load, it seems as though (again, in theory) we'd only use about 5kwh/day on average. With a few hours of mini split use per day, we'd be at 8ish. One of the many things I need to take into consideration - also why we're looking for land in areas which don't get too hot or cold on average. Designing a system which incorporates a haiku fan or two is much easier than trying to incorporate heating/cooling for temperature "extremes".

SolarPowered

Re: Solar design for off grid tiny trailer house

tydaddy wrote: »

If the array is built - say 2 strings of 8 panels each, with a custom mount, and manual (not mechanical) adjustment, really the only limit is the strength of the materials used to support such a load. 8 panels x 60# each, with mounting hardware, wouldn't be more than 600#, elevating one side, would be simple with 2 people.

it doesn't work that way. Your still not accounting for live load, and wind sheer factors. All of that has to be calculated by an engineer.

Lets say you are in the dead of winter, lets "assume" your tilt is 55*. Now you need supports on your mobile vehicle. Either A its going to tear and rip off right through the sheet metal, or B it will make your mobile tip over. I've seen RV's tip over under much less constraints.

Not to mention dead load, can the roof of the mobile handle it, are youo reinforcing, etc. It just gets more and more expensive, and becomes more and more impractical.

Cariboocoot

Re: Solar design for off grid tiny trailer house

I may have missed the explanation but ...
Why will this be built on a trailer?
I have seen some of these tiny house on trailer designs and frankly they're impractical. If you want mobile, you by an RV. If you want stick-frame constructed home, you build it on a foundation.
I have seen the promos for these too: "no building permits required" for example. Don't you believe it. It has to follow all the vehicle regs if it's mobile and all the housing regs if it's stationary. The moment you park it in a permanent location the inspectors will be around.

So, are you going traveling in this or are you buying some land and settling down? I'd hate to see you get a lot of $$$ invested and then find out some officious bureaucrat has a problem with the concept.

Iceni John

Re: Solar design for off grid tiny trailer house

As some other folk here have alluded to, maybe a Tiny Home isn't the best for what you need? A 40' bus, either a school bus or a Grayhound-type bus, may be a better option. I have a 40' pusher Crown that I'm converting for off-grid full-timing - it has 220 gallons of fresh water capacity (that's a LOT!) and appropriately large waste tanks, but it also has 2,040W of solar panels on the roof. I'm using eight 255W Sharp panels, and there's still space up there for some water heating panels and the central walkway between the roof hatches. I have space for eight batteries, either golfcart or L-16 depending on my needs. Inside I'll have 300 sq.ft. of living space (nice big bedroom, two big closets, separate shower and loo, kitchen, big living room, plus all the underfloor storage space. This will be comfortable living for one or two people off the grid for up to a month at a time - the off-grid time is primarily limited by water capacity.

You're still at the concept stage yet, so you could also consider other options - 40' shipping container, 53' reefer trailer, hi-cube low-floor trailer, ??? Just an idea.

John

BB.

Re: Solar design for off grid tiny trailer house

And--Just to be clear--We respect that energy usage is a complex set of personal choices. We are trying to figure out how to get you what you need and not that you have decided to use ABC amount of power.

With solar power, it is generally a much better investment of time and money towards conservation first--Then size the solar power system to support those loads/needs.

Also, do not forget the battery bank. For a full time off grid home, we recommend a battery bank sized to 4x your daily loads.

You can reduce that to 2x your daily load (or even less), but then that means more generator use and less battery life (the reality of batteries--Even if you have a 2x larger battery bank that lasts ~2x longer, it still costs about the same to replace a 1/2 sized battery bank 2x as often).

If you have a lot of power needs for your trailer (for example, say you do video and need an editing bay/satellite up links, etc.), you may be looking at Lithium batteries (a whole 'nother thread). Light weight, smaller size, some very nice electrical characteristics--As long as you respect the limits too. However--Not cheap and not a lot of long term experience yet with newer chemistries.

Or even simply running a properly sized/fuel efficient genset during the work day.

-Bill

tydaddy

Re: Solar design for off grid tiny trailer house

SolarPowered wrote: »

it doesn't work that way. Your still not accounting for live load, and wind sheer factors. All of that has to be calculated by an engineer.

Lets say you are in the dead of winter, lets "assume" your tilt is 55*. Now you need supports on your mobile vehicle. Either A its going to tear and rip off right through the sheet metal, or B it will make your mobile tip over. I've seen RV's tip over under much less constraints.

Not to mention dead load, can the roof of the mobile handle it, are youo reinforcing, etc. It just gets more and more expensive, and becomes more and more impractical.

Wow. I ask a simple question about solar system design, and I get advice on my house design that has nothing to do with my actual house design! I appreciate the concern guys, but 1. how do you know I'm not an engineer? and 2. I'm pretty sure if I'm building a HOUSE from the ground (trailer - lol) up, spending tens of thousands of dollars, I'd have thought about the loads involved in said design! Again, I do appreciate all of your concern - but back to the initial topic! Thanks!

tydaddy

Re: Solar design for off grid tiny trailer house

Cariboocoot wrote: »

I may have missed the explanation but ...
Why will this be built on a trailer?
I have seen some of these tiny house on trailer designs and frankly they're impractical. If you want mobile, you by an RV. If you want stick-frame constructed home, you build it on a foundation.
I have seen the promos for these too: "no building permits required" for example. Don't you believe it. It has to follow all the vehicle regs if it's mobile and all the housing regs if it's stationary. The moment you park it in a permanent location the inspectors will be around.

So, are you going traveling in this or are you buying some land and settling down? I'd hate to see you get a lot of $$$ invested and then find out some officious bureaucrat has a problem with the concept.

Well, what you're saying is true and not true at the same time. I've pretty much all there is to read on this topic. There are more rural places that won't be bothered by inspectors - moreso if you're not connected to any utilities. There are always loopholes, if one is smart enough to find them. Trust me, the scenarios are abundant - again, I emphatically appreciate your concerns, as I share them in some respects.

This will be a mostly permanent structure, that if we decide we wanted to move, we simply sell our land, pick up, and buy new land and move. I can go into all of the reasons, but really those reasons aren't important for this discussion. And no, I'm not one of those "preppers". I simply want a simpler life, sick of paying for things I don't need - large house, lots of gadgets, wasteful spending, etc, etc, etc.

Again, your concern is appreciated. I simply thought that rather than buying a "kit" that some website sells, it'd be cheaper, and much better quality to design one specifically for my needs. I figured this would be the place to get recommendations on specific components for said "energy need" rather than an analysis of my needs and decisions. lol.

tydaddy

Re: Solar design for off grid tiny trailer house

Iceni John wrote: »

As some other folk here have alluded to, maybe a Tiny Home isn't the best for what you need? A 40' bus, either a school bus or a Grayhound-type bus, may be a better option. I have a 40' pusher Crown that I'm converting for off-grid full-timing - it has 220 gallons of fresh water capacity (that's a LOT!) and appropriately large waste tanks, but it also has 2,040W of solar panels on the roof. I'm using eight 255W Sharp panels, and there's still space up there for some water heating panels and the central walkway between the roof hatches. I have space for eight batteries, either golfcart or L-16 depending on my needs. Inside I'll have 300 sq.ft. of living space (nice big bedroom, two big closets, separate shower and loo, kitchen, big living room, plus all the underfloor storage space. This will be comfortable living for one or two people off the grid for up to a month at a time - the off-grid time is primarily limited by water capacity.

You're still at the concept stage yet, so you could also consider other options - 40' shipping container, 53' reefer trailer, hi-cube low-floor trailer, ??? Just an idea.

John

Ahhh John. There's still hope in here yet. Yes. I've considered all options. This is the plan we decided on. My working design has all of the amenities you mentioned. Composting toilet, grey water garden bed, etc. The property will have a well, which will also be converted to solar. I'm still in the process of designing the system, filtering system, tanks, etc. If my design goes as planned, there will be the ability to collect and purify rainwater as well. I've got it loosely laid out, but still need to figure out specific components. We don't need a lot of space - in fact our dogs will need the majority of the space :-) Hence the large lots we've been considering! Most people buy land, build a big $250k house that they don't need...waste thousands of dollars on utilities to run their huge house...and for what?! We're going to buy land, build our little house to suit our needs, and life a normal life. When it comes time to move, we simply find new land in a new area that suits us, hook up to the Ram 3500 - load the smart car, and off we go.

tydaddy

Re: Solar design for off grid tiny trailer house

BB. wrote: »

And--Just to be clear--We respect that energy usage is a complex set of personal choices. We are trying to figure out how to get you what you need and not that you have decided to use ABC amount of power.

With solar power, it is generally a much better investment of time and money towards conservation first--Then size the solar power system to support those loads/needs.

Also, do not forget the battery bank. For a full time off grid home, we recommend a battery bank sized to 4x your daily loads.

You can reduce that to 2x your daily load (or even less), but then that means more generator use and less battery life (the reality of batteries--Even if you have a 2x larger battery bank that lasts ~2x longer, it still costs about the same to replace a 1/2 sized battery bank 2x as often).

If you have a lot of power needs for your trailer (for example, say you do video and need an editing bay/satellite up links, etc.), you may be looking at Lithium batteries (a whole 'nother thread). Light weight, smaller size, some very nice electrical characteristics--As long as you respect the limits too. However--Not cheap and not a lot of long term experience yet with newer chemistries.

Or even simply running a properly sized/fuel efficient genset during the work day.

-Bill

Thanks Bill. I've been reading a lot of your responses in other threads, and it seems like you're always so helpful in answering the questions many of us have. Thanks!