Off Grid Cabin in Arizona - help me re-design the solar system

System
System Posts: 2,511 admin
in General Solar Power Topics #1
I own a small off grid cabin about 50 miles West of Flagstaff, AZ near the town of Ashfork. I'm in the design phase of a total revamp of the existing solar layout - which is currently the bare minimum. I thought it would be fun to ask the members for their input.

You can view the cabin and read about it at my blog here:

http://offgridaz.blogspot.com/

My main goal is to be able to power an air conditioner in the summer. In this area, it is gets up to 100 in the summer.

I have no heating system for the winter, and it can get down to 15 degrees in the winter. So if anyone has any solar ideas for heating, I'd like to hear about them. My fallback plan is to put in a small wood burning stove.

So let your creative minds flow and post your ideas. Thank you everyone.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #2
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    Quick comment, more detail later perhaps,

    Reduce your ac loads as much as possible. Look into geo-thermal heat pump, swamp cooling, and above all shade the building(s). If you don't get the solar gain, you don't have to loose it. Remember, ac loads are huge for pv systems. Winter heat is much easier to accomplish.

    Icarus
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  • mwilsonnm
    mwilsonnm Solar Expert Posts: 26 ✭
    #3
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    Your set-up has some similar features that I have . For heating I use "direct vent" heaters that are propane fed. They are moderate to highly efficient and do not require any electricity to operate. I am located in west-central New Mexico at 7500' elevation and experience temps as low or lower than yours in the winter months. We use the cabin 1-2 weekends a month during the cold months. Good Luck ! Mark
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  • System2
    System2 Posts: 6,290 admin
    #4
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    Mwilsonm, thanks for the reply. Do the direct vent propane heaters you mentioned put off a propane gas odor at all? Also, can you point to a website that provides more information on these units?
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  • mwilsonnm
    mwilsonnm Solar Expert Posts: 26 ✭
    #5
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    The heaters pull oxygen from outside to burn and all of the combustible byproduts are vented outside.....very safe and no propane odors/leaks if installed by a professional. I am preparing to install my third unit. Check out this site.....Empirecomfort.com
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  • System2
    System2 Posts: 6,290 admin
    #6
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    I checked it out and its just what I need...thanks for the tip.
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  • System2
    System2 Posts: 6,290 admin
    #7
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    Re the AC loads, don't let slip by what Icarus said. These loads are indeed HUGE for an affordable solar system.
    If you can give us some idea of the power draw of the AC unit, what time of day you will be running it (daylight, solar power producing time) or at night when the load is on the batteries. Seriously, if you're planning on running a standard AC unit off a solar system, either you will have to have very deep pockets, or you'll have to get used to the heat.
    Cheers
    Wayne
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #8
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    Just to compare,

    A 7800btu small window ac unit draws 6.6 amps@ 120vac, call that 800 watts. (Sears energy star rated, off the web)

    So even if said ac unit is big enough, assuming ~50% duty cycle, you would need a panel capacity of ~1200 watts with the associated battery bank JUST to run the ac, assuming perfect efficiencies. If you wish to have any buffer for cloudy days, or other loads, the capacity must get proportionally larger and ergo more expensive.

    Super insulation, proper window shading, trees,,,

    Also look into Arabian cooling towers. I remember hearing about them on some radio program. It seems they work way better than swamp coolers with very little water usage. The idea is that mist is introduced into an open air column in the center of the structure. The the air then cools and then falls in the column, creating a very significant, very much cooler draft, without the use of any outside energy source. Something everyone in the S.W should consider.

    Icarus
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  • System2
    System2 Posts: 6,290 admin
    #9
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    I like the Arabian cooler tower, icarus...I'll look it into it and report back.

    The cabin is about 500 square feet; so at least were talking about a small area.

    The example you just outlined paints a stark picture...especially for the much larger cabin I want to build in the future.
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  • System2
    System2 Posts: 6,290 admin
    #10
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    PS - I would run an AC unit from about noon to sundown.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #11
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    As has been said many times on this forum, often times more eloquently than by me, your cheapest PV $$ is, conservation, followed by conservation, and then followed up by conservation. After that, solar water heat, passive solar space heat, then PV and finally wind.

    As you move forward with your "big" cabin ideas, keep good design in mind and don't get discouraged. We just built a new off grid house, more cabin than house, but none the less the lessons learned before paid off in big dividends.

    We are in a (much) colder climate than you so heating and winter lighting are paramount. Be thinking the building out well, and using good materials, we use no electric lighting as long as the sun is up, for the natural light is good where we need it. We get lots of solar gain in the winter, but much less in the summer due to the size of the over hangs. We heat with very little wood given the climate (~2-3 cords) and we only have to run the generator once in a while in the fall when the days are short and grey.

    Good luck and keep us posted. This site has a wealth of information provided gratis by a number of very smart people. (I don't include myself in that list!)

    Keep us posted,

    Icarus
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  • System2
    System2 Posts: 6,290 admin
    #12
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    I'm starting to understand now...I appreciate your direct approach. We'll never obtain the central air conditioning comfort we have become use to (I live in Phoenix...as I write this it is 112 degrees). But through good design and material selection, we can obtain adequate comfort - and still enjoy the independance of off grid living. Plus we'll be at and elevation of 5,000 feet - so the heat extremes will be much less.

    It seems that keeping warm will be easier than keeping cool.

    Thanks for good info...and thanks to those who have already posted lessons and advice on this board that I will eventually read and learn from. I'll keep you all posted. You can also check in on our progress at: http://offgridaz.blogspot.com/
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #13
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    For those of you that live in hot climes, here is some more info on wind towers.

    Way cool ideas that can be adapted to western architecture! http://www.thefarm.org/charities/i4at/lib2/aircool.htm

    I understand that in Saudi Arabia, people are building " Fake" wind towers and using modern ac, even though the wind tower technology is age old and free.

    Fo figure!

    Icarus
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #14
    Re: Off Grid Cabin in Arizona - help me re-design the solar system
    tkrichme wrote: »
    I'm starting to understand now...I appreciate your direct approach. We'll never obtain the central air conditioning comfort we have become use to (I live in Phoenix...as I write this it is 112 degrees). But through good design and material selection, we can obtain adequate comfort - and still enjoy the independance of off grid living. Plus we'll be at and elevation of 5,000 feet - so the heat extremes will be much less.

    It seems that keeping warm will be easier than keeping cool.

    Thanks for good info...and thanks to those who have already posted lessons and advice on this board that I will eventually read and learn from. I'll keep you all posted. You can also check in on our progress at: http://offgridaz.blogspot.com/

    I've always liked trying to get warm, as opposed to trying to get cool. Once your naked, you can't take any more off!

    T
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  • SolarJohn
    SolarJohn Solar Expert Posts: 202 ✭✭
    #15
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    It seems that you might be sold on the idea of propane heat, and that may indeed be the best choice for this situation, but I just wanted to suggest that you consider a pellet or corn-burning stove. I love mine. Corn is rather expensive right now, but you might be able to heat with pellets for less than the cost of propane. You'll also need a little electricity to run the auger and blower motors.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #16
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    Just a couple of observations... Misting for cooling will probably cause mineral "dust" in your home from the hard water.

    And if you think about using pellet stove--make sure you check the auger/fan/controller power requirements... I think I have read here that some of these stoves can take quite a bit of power when running (hundreds of watts). If you have plenty of solar/batteries--may not be an issue.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #17
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    SolarJohn, that is a great idea. Thanks for the suggestion. I'll do some research on this options...it's good to know you love it and that it works. I'd much rather burn pellets than propane. Where did you purchase yours?
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  • System2
    System2 Posts: 6,290 admin
    #18
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    Icarus, after a few hours of additional research into cooling towers, I came across a good article I would like to share:

    http://standeyo.com/News_Files/INFO_Files/How.To.Stay.Cool.in.Desert.html

    Cool towers are probably the best way to cool an off grid structure in the climate my property is located in.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #19
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    Good on ya!

    It just goes to show that you can achieve great efficiency if you can begin to think out of the box! There are tons of ideas out there, some tried and true, others more experimental.

    It was always frustrating designing custom homes over the years, how unreseptive clients often are to try something out of the ordinary. I tried to sell them on simple things like demand hot water, passive solar design and it is amazing how few people got it.

    Good luck,

    Tony
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #20
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    there are smaller swamp coolers that may fit the bill for you.
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  • newenergy
    newenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    #21
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    Solar patio shade right next to the house on the side that the breeze can enter through a window. Breeze enters through a large shaded area, plus solar modules are cooler than on the roof.

    Really good insulation on the ceiling. Maybe one of those cool roofs.

    For the cold, windows/thermal mass stuff might be going overboard here. Insulation is the main thing I would think.

    Just my thoughts. Where I live I'm almost never too hot or cold so I don't worry too much about these things.
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  • System2
    System2 Posts: 6,290 admin
    #22
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    Re pellet stove, they really are great stoves, however I also remember reading of rather unexpectedly large electrical requirements, but something else to think about - - - the availability of pellets. I know a very few years ago during an exceptionally cold winter, the price spiked, then in some areas, the product became unavailable at any price. AND that was before the present oil crises. There may well be no "best" for heating. Perhaps the solution, if costs permit, would be to have both pellet AND propane installations. We really are living in uncertain times regarding energy pricing and availability, to the point that I feel pushed to survivalist type thinking. In hindsight, that thinking had a big influence on my move to self sufficient solar power. Now I'm getting those same feelings about our food supply. Was on the news last evening, that out Canadian food supply, which one time was totally home grown, is now mostly supplied from the USA, with the next biggest supplier being China, and coming in at third place - - our own Canadian produced food. We've positioned ourselves in very dangerous territory with regard to our food supply.
    Wayne
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #23
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    I have always urged my clients to shy away from pellet stoves for a number of reasons. The reasons change with the price of energy but here are a couple.

    Over the years, the per btu into the room cost of pellets and propane have been very close. With pellets you had the added problem of storage of the fuel, as well as maintenence of the stove.

    Additionally, most pellet stove (all?) require 120vac to run at all. In the event of a power outage or off grid situation they either won't run or will take pv power. Hi ef direct vent propane will run without outside power. Very high ef units such as Rinnai space heater will run +95% ef using ~120 watts to power the blowers.

    In a casual use cabin, using a good EPA rated wood stove probably would be my first choice, assuming it is placed in an efficient building. Understanding that there are air quality issues, particularly at elevation (inversion layers etc) a good stove, burning clean, dry fuel is pretty clean. Assuming that you have some ready source of wood in the mountains would help. Beware of cheap stoves however as they are both inefficient as well as dirty to burn.

    As I have said before, with proper insulation, passive solar design, thermal mass, the amount of wood you would need to burn in all likelyhood would be quite modest.

    For a whole lot of reasons, I would stay away from corn stoves! If you are an Amish farmer growing your own in a traditional life, I would make that exception. For the rest of us, the idea of "burning food" is criminal! Look at what the ethanol push has done for food prices for the poor ( and not so poor) around the world of late!

    Icarus
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  • System2
    System2 Posts: 6,290 admin
    #24
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    There are some very efficient and compact wood burning stoves on the market. In fact, many of mfgs have been around a long time and their stoves are almost works of art - in a strange kind of way. I have plenty of dead juniper and pinon to burn on the 20 acres I own. And, this is a casual use cabin. Given this, a good wood burning stove is a viable option for this design. A small one in corner would do well.
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  • System2
    System2 Posts: 6,290 admin
    #25
    Re: Off Grid Cabin in Arizona - help me re-design the solar system
    Look at what the ethanol push has done for food prices for the poor ( and not so poor) around the world of late!

    For what it's worth, I drive past thousands and thousands of acres of corn Monday through Friday to and from work. The latest crops were planted over two months ago and there still is no fuel being produced from these fields although the local farmers have consumed much fuel by plowing, fertilizing, planting and dusting them. Previously the fields have been planted with a random mixture of sorghum, rice, soy beans and corn, now it's about 75% corn. When the corn is harvested in two or three weeks there will be two ears of corn per stalk and maybe a cup of corn per ear. I don't know how much ethanol that one cup of corn will produce but it is dependent on sugar content. My guess is that after fermenting and distilling (energy consumptive) there might be one half cup of ethanol per corn stalk (two ears of corn). As you can guess I don't believe food will solve our energy production problems (drill here, drill now).

    Pull this post if you see fit as it doesn't follow the OP's topic, just comments on one of the replies to it.

    Cheers,

    Bad Apple
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #26
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    I too have used Empires off and on for years. The direct vents are fairly good units. They do suffer from some efficiency issues however, as well as some gas valve/thermocouple issues.

    If you only use this building on the weekends or so, then the efficiency issue is not so big, but if you use it year round 24/7 it adds up. I believe (help me out if I'm wrong here) that they advertise an annual fuel efficiency of ~70%. I think that it optimistic at best. If you can live with some small electrical usage I strongly reccomend Rinnai direct vent heaters. They do draw ~ 75 watts full bore, but what they do that the Empires can't do is modulate the gas valve so that it only burns what it needs. With the Empires is is basiclly on or off. The room air fan also serves as the combustion air fan so that it is both electrically efficient as well as gas efficient. A typical Rinnai will have an AFE rating of ~95%. Great units, not cheap. (No standing pilot light too!)

    The nice thing about both is that they draw all their combustion air from outside and vent all the exhaust out as well. (Rinnai does make a vent free line, but even thought they claim to be safe, I don't like the idea, especially in a small building).

    Most heaters will be more efficient the bigger they get.

    Icarus

    PS Something is hinky about this thread,,,, It may be me. I swear someone posted some info about Empire heaters in this thread and that is why I am responding. Now after I post this, I cannot find the mentioned post. Maybe I am going crazy. If this post is out in left field, MODs feel free to delete it or move it.

    Sorry for any confusion,,,,,I certainly am confused!
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  • System2
    System2 Posts: 6,290 admin
    #27
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    You are not going crazy, icarus. Post number 5 was where Empire was mentioned. Your posts are top notch and filled with good information, so keep'em coming.

    I have to say, the responses in this thread have been fantastic. Thank you all. It's great to know there is a tight group of folks out there that identifies with what I'm trying to accomplish.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #28
    Re: Off Grid Cabin in Arizona - help me re-design the solar system

    I guess the thread got long in a hurry!

    T
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  • SolarJohn
    SolarJohn Solar Expert Posts: 202 ✭✭
    #29
    Re: Off Grid Cabin in Arizona - help me re-design the solar system
    tkrichme wrote: »
    SolarJohn, that is a great idea. Thanks for the suggestion. I'll do some research on this options...it's good to know you love it and that it works. I'd much rather burn pellets than propane. Where did you purchase yours?

    I strongly disagree with those who think burning corn is criminal. Corn is a renewable resource, and unlike wood, it only takes one year to replenish the supply. I'm not crazy about the idea of using corn for ethanol production though. That's the reason for the huge surge in corn prices. A corn burning stove is a much more efficient use of corn than converting it to fuel. I also disagree with those who believe we should drill for more oil. We should be thinking about conserving what little fossil fuel remains for future generations. Burning less oil is also better for the environment. Pellets are made from wood byproducts, which may otherwise be wasted. Since corn and pellets are both carbon-neutral, neither is bad for the environment. I could go on, but I'll stop here.

    Since your electrity is limited, you'll need to make sure that the stove you choose has low electricity requirements. Some are better than others. There is some work involved with corn or pellet stoves. You'll need to do some hauling and storing. You'll have to be more careful with corn storage, as rodents are attracted to it. Corn and pellet stoves are much safer than wood-burning stoves. You can buy stoves that will burn both corn and pellets, or a mixture of both. For more information, try this website: www.iburncorn.com

    There is a considerable amount of misinformation within this thread. You should do some research and make sure that the information you get is accurate. To answer your question; I bought my corn-burning stove from a local fireplace shop in Alton Illinois. If I had it to do over again I'd buy a stove that can burn both pellets and corn. The price of corn has trippled since I bought my stove.

    john
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #30
    Re: Off Grid Cabin in Arizona - help me re-design the solar system
    SolarJohn wrote: »
    I strongly disagree with those who think burning corn is criminal. Corn is a renewable resource, and unlike wood, it only takes one year to replenish the supply. I'm not crazy about the idea of using corn for ethanol production though. That's the reason for the huge surge in corn prices. A corn burning stove is a much more efficient use of corn than converting it to fuel. I also disagree with those who believe we should drill for more oil. We should be thinking about conserving what little fossil fuel remains for future generations. Burning less oil is also better for the environment. Pellets are made from wood byproducts, which may otherwise be wasted. Since corn and pellets are both carbon-neutral, neither is bad for the environment. I could go on, but I'll stop here.

    Since your electrity is limited, you'll need to make sure that the stove you choose has low electricity requirements. Some are better than others. There is some work involved with corn or pellet stoves. You'll need to do some hauling and storing. You'll have to be more careful with corn storage, as rodents are attracted to it. Corn and pellet stoves are much safer than wood-burning stoves. You can buy stoves that will burn both corn and pellets, or a mixture of both. For more information, try this website: www.iburncorn.com

    There is a considerable amount of misinformation within this thread. You should do some research and make sure that the information you get is accurate. To answer your question; I bought my corn-burning stove from a local fireplace shop in Alton Illinois. If I had it to do over again I'd buy a stove that can burn both pellets and corn. The price of corn has trippled since I bought my stove.

    john

    John,

    No offense intended. I probably should have chosen my words a bit more carefully. You make good points about corn, and I too agree that ethanol is a suckers bet. I also agree that fossil fuels should generally be used as a last resort.

    In my opinion, pellet stoves are best for those in areas where there is no waste wood available. The great beauty of pellets is that they use a huge proportion of the available bio-mass. Corn stoves (as I understand them) only use the kernels and cobs, leaving much biomass wasted. Also growing corn is a very energy intensive, fertilizer intensive, as well as pesticide and herbicide intensive. I do make the exception for those that live in corn country, especially those that grow their own.

    Wood is not the panacea for the world either. I only endorse wood to those that have ready access to fibre that would otherwise go to waste. (Understanding that you can never use 100%, nature needs t be regenerated).

    As for misinformation on these posts. I hope that you will call me out if ever I say something that you think is misinformation. I strive to make clear when I am opining as opposed to stating fact.

    Sorry if I offended anyone,

    Tony
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  • System2
    System2 Posts: 6,290 admin
    #31
    Re: Off Grid Cabin in Arizona - help me re-design the solar system
    SolarJohn wrote: »
    I strongly disagree with those who think burning corn is criminal.
    john

    I think it best I walk away and say nothing, other than I will agree to disagree.
    Cheers
    Wayne
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