Solar design for off grid tiny trailer house

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  • SolarPowered
    SolarPowered Solar Expert Posts: 626 ✭✭✭
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    Re: Solar design for off grid tiny trailer house
    tydaddy wrote: »
    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!

    My last post was deleted because of my brash and dry commentary, but I will just tell you how it is.
    Your attitude tells me your not an engineer because any other engineer would calculate any inherent liability, you avoid this.
    Cheapest panels on the market VS performance. You ignore this.

    Doesn't matter if it is your home, or your vehicle, you should always respect what you have, reduce liability, and do the right thing, and properly account and be responsible for things you build before it kills some one or yourself.
  • tydaddy
    tydaddy Registered Users Posts: 22
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    Re: Solar design for off grid tiny trailer house
    My last post was deleted because of my brash and dry commentary, but I will just tell you how it is.
    Your attitude tells me your not an engineer because any other engineer would calculate any inherent liability, you avoid this.
    Cheapest panels on the market VS performance. You ignore this.
    Both false. First, I've never avoided any inherent liability, I simply think outside the box, much more than most - and have never not been able to build a design I have come up with - safely! I simply asked about a SINGLE panel, because do any internet search and they're continually getting fantastic reviews for liability and cost. Why would I not start there?

    Doesn't matter if it is your home, or your vehicle, you should always respect what you have, reduce liability, and do the right thing, and properly account and be responsible for things you build before it kills some one or yourself.
    No need to erase comments, as every one is appreciated. Trust me, I have a thick skin and whether I agree with an opinion or not, they all make me reassess various parts of the build.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,477 admin
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    Re: Solar design for off grid tiny trailer house

    This forum is run as a family friendly/technically oriented place. It is also funded by our host NAWS, and we need to be respectful that this forum also reflects on their business.

    If you disagree with a post--Talk about the content of the post. Most of us here have never met the people we are talk to here. Please be nice.

    We specifically do not host a "cafe" or political space. Many times, these types of discussion become very difficult to moderate (we moderators either look like we are clamping down or cheer-leading a person/position--We cannot win :blush:).

    For the most part, we do very little moderation here. Everyone is usually very respectful and attempt to answer questions to the best of their abilities. What more can we ask for.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Solar design for off grid tiny trailer house
    tydaddy wrote: »
    No need to erase comments, as every one is appreciated. Trust me, I have a thick skin and whether I agree with an opinion or not, they all make me reassess various parts of the build.

    Actually there was need to erase the comments; we have standards on the forum and they will be maintained.

    Anyway, how is it looking for you so far tydaddy?
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
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    Re: Solar design for off grid tiny trailer house

    I'm jumping in late and haven't read all responses, but here goes anyway:
    tydaddy wrote: »
    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.

    Solar radiation differs WILDLY between summer and winter. So you're on the right track by having different consumption figures for different times of year. Depending on where you are on the planet, 5kWh/day in winter and 12kWh/day in summer is entirely feasible from the same array. What's more is that with the addition of a generator you'll have more freedom to get the solar array size wrong and can cope better with unexpected weather.
    Broadly, to calculate the system size, I work from:
    1. daily consumption in kWh/day (remember to include the inverter standing consumption)
    2. battery size = consumption * days of autonomy / depth of discharge. E.g. 5kWh/day * 2 days / 0.5 (50% DoD) = 20kWh battery. / 24V = 833Ah or /48V = 416Ah.
    3. to size array you can assume 10% losses in the array (if using an MPPT charge controller) + 30% losses in charging/discharging the battery. So to get 5kWh from the system you need to capture 7kWh of solar energy daily (on average). Now you'll need to consult an online solar calculator that will tell you how much PV you need in winter to meet that demand.
    tydaddy wrote: »
    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.

    Broadly the system is:
    - PV panels with a Voc rating in cold weather that fit under the maximum V rating of the charge controller you choose
    - MPPT charge controller, because you want the most efficiency from your panels
    - Flooded lead acid batteries, best bang for buck, preferably in 2V cells. They will gas during charging so you need to plan for good ventilation.
    - Combined inverter/charger unit, which will play nice with a generator or other external AC source. The maximum rating must fit in with what your loads will draw instantaneously. Outback, Xantrex, Magnum are popular US brands.
    - DC breakers/fuses between parallel PV strings and between CC and batteries and between batteries and everything else.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
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    Re: Solar design for off grid tiny trailer house
    tydaddy wrote: »
    we're not trying to live frugally, just simply disconnected and more simply

    You can't have it both ways... it is much simpler to be connected to the grid. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • tydaddy
    tydaddy Registered Users Posts: 22
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    Re: Solar design for off grid tiny trailer house
    Actually there was need to erase the comments; we have standards on the forum and they will be maintained.

    Anyway, how is it looking for you so far tydaddy?

    Thanks! I understand, I just wasn't offended by the reply. Again, I'm new to this, so all comments do offer some perspective. As for the design, I've been busy so haven't made much progress in the last few days, and this will be a long process - 6+ months. I'm a planner, and actually over planner. Most things I design are completely over engineered, and that takes time as there are a lot of "what if's" and I try to incorporate every scenario possible - helpful but also extremely tedious (I'm learning) with solar system design.

    I've been trying to do more research on solar panels, and I'm curious as to where the evidence is that mono are THAT much better than poly for my wants. It seems - from EVERYTHING I've read, that in real world use, for my design, there will be differences, but not enough to offset the costs - ie very very minute differences/advantages/disadvantages.

    Also, online reviews, ratings, longevity, build quality, etc, Canadian solar still seems like a great product for the money? Again, not looking simply at prices, but worth of product for the money I'm looking to spend.

    I've also started looking at off the shelf systems, however, I know that they are designed for the seller to make the most money possible. I would post a link as an example of a system I've found that peaks my interest, but am not sure of the rules of the forum in that regard.

    Thanks!

    Tyler
  • tydaddy
    tydaddy Registered Users Posts: 22
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    Re: Solar design for off grid tiny trailer house
    stephendv wrote: »
    I'm jumping in late and haven't read all responses, but here goes anyway:



    Solar radiation differs WILDLY between summer and winter. So you're on the right track by having different consumption figures for different times of year. Depending on where you are on the planet, 5kWh/day in winter and 12kWh/day in summer is entirely feasible from the same array. What's more is that with the addition of a generator you'll have more freedom to get the solar array size wrong and can cope better with unexpected weather.
    Broadly, to calculate the system size, I work from:
    1. daily consumption in kWh/day (remember to include the inverter standing consumption)
    2. battery size = consumption * days of autonomy / depth of discharge. E.g. 5kWh/day * 2 days / 0.5 (50% DoD) = 20kWh battery. / 24V = 833Ah or /48V = 416Ah.
    3. to size array you can assume 10% losses in the array (if using an MPPT charge controller) + 30% losses in charging/discharging the battery. So to get 5kWh from the system you need to capture 7kWh of solar energy daily (on average). Now you'll need to consult an online solar calculator that will tell you how much PV you need in winter to meet that demand.



    Broadly the system is:
    - PV panels with a Voc rating in cold weather that fit under the maximum V rating of the charge controller you choose
    - MPPT charge controller, because you want the most efficiency from your panels
    - Flooded lead acid batteries, best bang for buck, preferably in 2V cells. They will gas during charging so you need to plan for good ventilation.
    - Combined inverter/charger unit, which will play nice with a generator or other external AC source. The maximum rating must fit in with what your loads will draw instantaneously. Outback, Xantrex, Magnum are popular US brands.
    - DC breakers/fuses between parallel PV strings and between CC and batteries and between batteries and everything else.


    Great advice, and it makes me happy that pretty much everything you have stated lines up with my current thought process.
  • tydaddy
    tydaddy Registered Users Posts: 22
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    Re: Solar design for off grid tiny trailer house
    vtmaps wrote: »
    You can't have it both ways... it is much simpler to be connected to the grid. --vtMaps

    Assuming there are grid connections at the location in which you live. But you're then still dependent upon the "man".
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
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    Re: Solar design for off grid tiny trailer house
    tydaddy wrote: »
    Assuming there are grid connections at the location in which you live. But you're then still dependent upon the "man".

    I'm off-grid and I am very dependent on the battery "man" and the gasoline pump "man" (for my generator). And when my generator or electronics fails i will be dependent even more on the "man".

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • tydaddy
    tydaddy Registered Users Posts: 22
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    Re: Solar design for off grid tiny trailer house
    vtmaps wrote: »
    I'm off-grid and I am very dependent on the battery "man" and the gasoline pump "man" (for my generator). And when my generator or electronics fails i will be dependent even more on the "man".

    --vtMaps


    Lol. Yes, but extremely less dependent than those relying solely on the grid.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Solar design for off grid tiny trailer house

    Monocrystaline panels are 2-4% more efficient than polycrystaline, with the best ones running about 20% efficient. When you need to squeeze every last Watt out of the space available it becomes worth it. When you've got huge amounts of roof real estate (mine measures over 800 square feet on the main South-facing facet) it is not such a concern.

    I think I missed the answer to whether this would be an actual mobile install or a 'transportable' install. There are ways of setting up movable ground mount arrays to increase your available PV if needed.
  • tydaddy
    tydaddy Registered Users Posts: 22
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    Re: Solar design for off grid tiny trailer house
    Monocrystaline panels are 2-4% more efficient than polycrystaline, with the best ones running about 20% efficient. When you need to squeeze every last Watt out of the space available it becomes worth it. When you've got huge amounts of roof real estate (mine measures over 800 square feet on the main South-facing facet) it is not such a concern.

    I think I missed the answer to whether this would be an actual mobile install or a 'transportable' install. There are ways of setting up movable ground mount arrays to increase your available PV if needed.

    Yea, that's what I've read. I think for the price difference, 2-4% is hardly worth. Say I've got a 25 panel array, at 4%, I'd simply need to add a 26th to make up for the loss. Again IN THEORY. Much smaller investment.

    Yea, I responded somewhere in the thread. This will be a semi permanent install. The idea being that we would want everything set up and functioning prior to the "move". So the easiest solution was to build the house self sufficient, so that we wouldn't need to take a significant amount of time installing posts, building frames, etc. once on our land. I've come up with a couple of solutions using a ground install, however, that means more money in wiring, more planning, etc. Again, I'm sure 5kwh would be enough, but then we start thinking about supplemental heat/cooling weighing the costs/benefits.

    A question that hasn't been answered - that I can't find online - probably because the lack of my knowledge or simple terminology, but are there inverters that are primiarily off grid, however, if the option to connect to the grid arises, they can do so without modification to the system? Almost a plug and play? I mean really I can't envision a scenario that this would apply except that we realize that the amount of solar power we end up producing simply isn't meeting our needs, and rather than expanding the system, the cost is cheaper to simply "connect" to the grid. Similarly, if such a design does exist, can it then be capable of selling back to the electric provider? This scenario seems more likely, in that I'd imagine we'd be producing more than we need most of the year. The issue being that as soon as one would connect to the grid, inspectors would likely be involved.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Solar design for off grid tiny trailer house
    tydaddy wrote: »
    A question that hasn't been answered - that I can't find online - probably because the lack of my knowledge or simple terminology, but are there inverters that are primiarily off grid, however, if the option to connect to the grid arises, they can do so without modification to the system? Almost a plug and play? I mean really I can't envision a scenario that this would apply except that we realize that the amount of solar power we end up producing simply isn't meeting our needs, and rather than expanding the system, the cost is cheaper to simply "connect" to the grid. Similarly, if such a design does exist, can it then be capable of selling back to the electric provider? This scenario seems more likely, in that I'd imagine we'd be producing more than we need most of the year. The issue being that as soon as one would connect to the grid, inspectors would likely be involved.


    Any off-grid inverter-charger has an AC IN that can be connected to generator or grid power. If you use one of the hybrid types (Xantrex XW, Outback Radian or GVFX) you can also interact with the grid, selling surplus power to the utility (with the correct agreements and permits in place).
  • tydaddy
    tydaddy Registered Users Posts: 22
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    Re: Solar design for off grid tiny trailer house
    Any off-grid inverter-charger has an AC IN that can be connected to generator or grid power. If you use one of the hybrid types (Xantrex XW, Outback Radian or GVFX) you can also interact with the grid, selling surplus power to the utility (with the correct agreements and permits in place).

    So something like this with proper panels and battery bank, generator, auto gen start, etc would essentially be "all" I'd need...
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Solar design for off grid tiny trailer house
    tydaddy wrote: »
    So something like this with proper panels and battery bank, generator, auto gen start, etc would essentially be "all" I'd need...

    That's the Radian. Once in place the only change needed to get it to sell to the grid is connecting up the wires and programming the function.
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
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    Re: Solar design for off grid tiny trailer house
    tydaddy wrote: »
    So something like this with proper panels and battery bank, generator, auto gen start, etc would essentially be "all" I'd need...

    Just to be clear, not all inverter/chargers will let you feed surplus power back into the grid. For example, Outback have a VFX series of inverter/chargers that can take power from the grid, but can't feed power back, then they have a special "G" series that will let you feed power back to the grid (the Radian also is a grid feeding variety).
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
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    Re: Solar design for off grid tiny trailer house
    stephendv wrote: »
    Just to be clear, not all inverter/chargers will let you feed surplus power back into the grid. For example, Outback have a VFX series of inverter/chargers that can take power from the grid, but can't feed power back, then they have a special "G" series that will let you feed power back to the grid (the Radian also is a grid feeding variety).

    There is one more aspect to consider... the generator. The inverters that sell back to the grid have much tighter tolerances on the quality of the generator AC than the other type. Many folks have found that if they want to use a grid-feeding inverter with a generator, they need an inverter-generator. Of course, you also make sure you don't have the grid-feeding inverter set to feed excess power (from solar) to the generator.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • tydaddy
    tydaddy Registered Users Posts: 22
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    Re: Solar design for off grid tiny trailer house

    Thanks guys. Lots of good info to get my plan a little more focused. I'm sure I'll have more questions soon, but this allows me to do a bit more planning and configuring.