We're building a new home and it will be off-grid for electric and water catchment. Any of you off-gridders out there care to share your experiences. I'm looking for info on what you would and would not do if building a new off-grid home.
The location is rural rainy Maui at about 1500 ft elevation. Our new home will be an 880sf bamboo house. We're looking at Uni-solar building integrated solar panels, but not 100% sure if that's the route for electricity since our site is not optimal sun, not bad necessarily, but not optimal. We also have a site on the property that looks good for wind, but we're not sure of the average wind speed so are getting an anemometer to find out. Of course we will have solar hot water, and we're looking at a 25,000 gallon water catchment system. It's a very rainy location, especially in winter (we think 100+ inches per year). Our back-up generator is a 7kw propane Onan, about 15 years old but runs great. Just couldn't afford a good diesel unfortunately, but we got lucky on the Onan at only $500 delivered and installed.
Thanks for any input.
ShaunThis message has been edited. Last edited by: Shaun,
My God! An off grid home in paradise! Do you have any streams on the property?
880 square foot sounds small, by continental standards. But, often it is easier to do solar/alternative energy in a small house.
This is an excellent resource for weather info:
I don't see Maui listed.
According to the website, the number of cloudy days (in Honolulu) are pretty constant year-around which is good.
Contrast that to Eugene, Oregon where around January we start wondering if we'll ever see the sun again.
This website has a lot of excellent info about off grid houses, solar, wind, etc. Somewhat weighted towards wind power, but still a lot of good information.
So, a couple of questions that come up:
1 - What are you doing about living space heating/cooling?
2 - What are you doing about cooking?
3 - TV, Microwave, etc?
There are a number of systems to choose from. However, if you are going to be off-grid, then I would encourage doing as much with 12V or 24V as possible. I.E. Run all of your lights off of 12V. At least I would only run my inverter when it was absolutely necessary.
In that climate a large load will be electricity for refrigeration mostly to freeze and cool food, not including airconditioning. RV fridges offer some 12v options for running direct off solar charged batteries. Solar ammonia absorption cooling works too.
The reason I asked about streams is micro hydro with enough flow and head can make wind or solar completely unecessary.
We have a stream, but it only runs 4-5 months/year (Jan.-May), and we are looking into putting in a micro hydro.
(1) The only heating we will have is an old wood burning stove. Won't have an AC unit, and will use ceiling fans for any cooling needs.
(2) All cooking and refrigeration will be propane, at least to start.
(3) We did put together a comprehensive appliance worksheet that puts us at 100-120kw/month. It includes a couple of tv's that won't get much use and a microwave.
Good advice on 12V/24V.
Thanks for the reply's
I disagree from my 22 years of living with and designing and selling solar power systems. Current inverters are 95% efficient. At 12 volts you will lose more than 5% in the wiring depending on the device, and each will need its own 10x larger wires run to it, instead of using standard 120v wiring and fixtures which are far cheaper and there are many more types of lights and fixtures to choose from. Many of the 120v lights put out more light per watt as well, more than beating the 5% loss of the inverter. There are a few things (some small pumps) that are more efficient at 12 volts, but not many.
Propane Onans are great, especially if its an 1800rpm model. I have one and you can barely hear it when running.
My main advice is to look at each device you use, usually there is a more efficient model, and it usually pays to buy the most efficient one even if it costs more upfront, since you then need less solar/wind.
I don't like propane refrigs. They always put carbon monoxide in your house, which gives me a headache. Several of my neighbors with them had to completely repaint the inside of their house due to soot buildup on the walls after a few years, that can't be good for your lungs. Check out Sunfrost refrigs, they are great and will pay for themselves compared to propane costs. I have had one of them for 22 years and it still works flawlessly and only draws 40 watts compared to a typical frig which draws 300 watts. I have sold lots of them: http://www.sunfrost.com/
Just thinking of alternative energy...
Has anybody done anything with geothermal energy in Hawaii?
Oh, I see there is some... at least on an industrial scale. I'm not sure if it could also be translated into a micro scale.
Our Onan is an 1800rpm model, and you're right about how quiet they are. Thanks for the input on refrigerators, we have been set on getting a propane one, but we'll have to look at it closer to make sure we're making a well informed decision.
Thanks for all the input.
That would seem to really be the ticket, to me, if it could be worked out. Talk about any place in the world with an excess of geothermal energy! There and Yellowstone...and Iceland ...
It's not hard to build your own super-insulated refrigerator/freezer (or just buy a Sunfrost). Backwoods Solar used to sell the kits, and probably still does. I forget the brand names, but it might be worth researching. I'm guessing that Sunwizard can help, too. Extraordinarily low power consumption is possible, especially for small units. I, too, recommend against propane for refrigeration, for all the usual reasons.
Tony from West Oz might have some useful advice. In fact, they'll be travelling to Hawaii to catch a cruise ship soon, I believe. Perhaps you could arrange to visit?
I also agree with Sunwizard regarding 12/24 vdc vs invertor power - life and wiring is easier with 120ac lighting and outlets.
Give long and serious consideration to battery choices. My favorites are Nickle-Iron, but they're very expensive. You might have an advantage though, living closer to China where they ship from. They last effectively forever, vs really good lead/acid that last less than 10 years.
Wind power is a great idea, if you've got a reasonably good location.
off-grid barn for 10 years, and soon to add houselights to off-grid system.
We decided to go with a brand name refrigerator, one with the lowest kwh consumption we could find. We figure the far lower cost of the refrigerator plus the extra cost of the solar panels/batteries will still be less than the $3500 cost of getting a Sunfrost to Maui ($3200 for the frig plus shipping), and it has more capacity to boot. Glad we received the advice about the propane frig's, we were deffinitely set on that option.
As for lighting, I'm looking at LED's as a way to significantly save on energy. Anyone have any input in using LED's to replace standard lighting in a house? From what I've found LED's are very expensive, especially the direct replacements for 60W incandescents $60 to $100 each , but will probably pay off in the end (Geobulb, X-tremegeek.com).
I have not researched this myself, but I hear that if you already have hydro in place, and you have some elevation variation on your land, water is a very good way to store energy compared to all battery. Pump to the top of the land in the heat of the day when you have solar. Run water down hill to a lower tank in the afternoon/eve when you need power. It sounds like you will be half way there with the one large tank.
Congrats on your project. Whatever you choose for your setup, please keep a good record. The rest of us might be coming to you for input soon.
03 Dodge 2500 B100 homebrew
79 Rabbit B100 homebrew
Another thing for you to look up.
Staber Washing Machines are one of the more efficient models out there.
I must admit that capacity is somewhat small, but they certainly are worth exploring.
I assume you're planning some kind of "line-drying".
I've had a Staber for about 5 years. It has not been trouble-free, compared to our old Whirlpool top loader, and I blame the design. It does use less energy and less water, and does a good job cleaning clothes. The drum bearings already failed once (replaced under warranty, with an "improved" part, just before the warranty ran out), and the springs that hold the doors open broke, all close to the same time (classic fatigue failure), requiring taking the machine apart to replace them. It'll need it again in about 2 more years when they fatigue and break again. I've replaced the driven pulley once (warranty repair, the hub wore out - it's too small for the load in my opinion), and the motor bearings failed (they're not sealed, and got dripped on when the drum bearings failed). Luckily I'm handy with tools and can do the repairs myself (the motor bearings must be pressed out and new ones pressed in, saving nearly $400 over the motor replacement cost). I could have bought two Whirlpool or Bosch machines for the same price, but they would not fit the space we have in our 550 sq ft house.
The factory has been very responsive. I'll give them credit for good customer relations. The Staber has many fine features, but I expected 20 years of trouble-free service. As it is, I can expect a major repair every 4-5 years.
Japan and China make highly efficient, small washing machines, much cheaper than the Staber.
For most frigs thats not true, but you can calculate whether its worth it. For example the most efficient Frigidaire (18 cu. ft) you can get draws 1100watt/hrs./day. Compared to the same size sunfrost which draws 480 wh/day. The extra panels/mounts/wiring/controls/batteries for the difference costs about $2000, depending on your supplier and sun hours per day. So your "break-even" point to buy the less efficient frig is $1500. But the batteries get consumed so in the long run the difference will be even more, add about $50-100/year to eventually replace the extra batteries needed (at current battery prices, and hope they don't double again as they did 2 years ago). This is an important decision since it will probably be your biggest power consumer.
LED's are still too expensive compared to CF's to justify the extra cost except in flashlights. Also the light spectrum isn't as good. If you get the LEDs with the warm spectrum (the only kind I would use since the blue spectrum ones bug my eyes quickly) they aren't more efficient than a good CF bulb that costs a tiny fraction of the price. $100 LED bulb 7.5w=260 lumens (=25w standard), (which is dim, directional, and hard to find higher brightness) while a $5 CF 9w=500 lumens (=40w standard) and you can get any other brightness and spectrum you like.
Whatever you do, don't even consider "standard" lighting except in places you use less than 15 minutes a day.
I'm really interested in looking at water storage power, but have not been able to find any info on a small scale system. Directly behind where we are building the house we have a 50-75 foot hill, and at the top of that hill there is a good half acre of flat land, so we have an excellent site if this is in fact a feasible energy solution. Potentially could put in water catchment up top also so wouldn't need to have a solar pump. Anyone know of such a system?
We also have the stream 75 feet away/below the house that flows 4-5 months so looking to see if it's worth it to put in a micro hydro there. Conveniently the steam flows in the winter when it is cloudier.
Thanks for that, will look into it.
Johno - thanks for the first hand experience.
The Sunfrost we were looking at (RF 19) consumes 770watt/hrs./day, so our savings is even greater. The one we bought uses 1070/watt/hrs./day and is just over 20 cubic feet. We paid $725 for it. In the long run we may have not made the correct decision, but we are going to be well over budget so we need to make some shorter term decisions that will help us keep our overall costs down.
Amazing how much they cost. We'll probably go with CF's, and deffinitely won't be using any incandescents.
Conventional frigs fake their cu. ft. numbers in typical US style. A 20 of most conventional brands is close to the 16 cu.ft. Sunfrost in capacity. Consumer reports says that some that claim 25 are actually 16:
Refrigerator capacity claims sometimes don’t add up
You got a good price on yours, so you can afford to eventually replace the extra batteries needed several times.
Here are pictures of our house. They were taken at the factory in Vietnam, where the house is constructed, and then taken down and shipped to Maui. It's supposed to be here just after xmas.
Nice tropical house -
Thiis links to a discussion about making up LED's for lighting. Led's are available pretty cheap in bulk or/and as lighting kits on Ebay, they ship from China but the ones I have ordered came directly through the post office in a few days with no stop at customs.
5 watt LED's are sold as replacement lighting kits for RV's to replace the normal 18 watt 12 volt incandescent automotive bulbs used in there lighting fixtures, a web search for "RV LED lighting" should find a lot of info. The LED's can be wired to operate from any voltage from around 3 volts up to as many volts as you want to use, no more power is used for the higher voltage, the led's are simply wired in series up to that voltage rating.
Fridge options - I assume your new fridge is a horizontal chest type, they don't dump out all there cold air every time the door is opened. You could even buy a cheap used chest type freezer and change the thermostat to one from any old frig so you can set it to frig temps, some freezer thermostats will turn down to frig temps but most don't, changing the thermostat is fairly simple, especially if it does not have to be pretty.
Another option might be to have a custom highly insulated wooden chest type ice box made up. Buy a used chest type freezer and add extra insulation, fill 2-liter soda bottles with water and use the frozen bottles to keep the ice box cold. Power the freezer from your generator every few days for as long as it takes to freeze a chest full of ice, running the generator at around 3/4 load continuously will take less fuel than cranking it every day to cool a normal frig, run the freezer at the same time you are charging your battery bank.
I am currently living in a 30 ft travel trailer on 5 rural acres in southern Arizona, it is a 50 mile round trip to the closest large grocery store. The tiny RV absorption frig is not big enough to hold all the food needed to keep the round trips to a minimum so I do the "ice from freezer into big Coleman cooler" technique, I do have mains power for the freezer so not exactly the same as your situation but close. 4 frozen 2-liter soda bottles keep the big cooler cold for at least 24 hours even in 100 deg f temps, in the current low 80's temps 2 bottles work fine and I can even go for 2 days without renewing the ice if the temp only gets into the high 70's, in a really really well insulated top opening cooler chest (6-8 inches of foam) each charge of ice would last a LOT longer. I keep the freezer about half full of frozen soda bottles so when I put the melted water bottles back in to freeze most of the energy required to do that comes from the already frozen bottles in the freezer rather than from the frig mechanism, it just keeps everything down below freezing.
A local ranch here made a temporary walk-in freezer out of 6 inch thick styrofoam panels and an old window air conditioner to use during butchering. Styrofoam - great stuff.
Batteries for your battery bank - Something to look into, I recently picked up two FREE very large steel cased battery assemblies from old electric fork lifts, each assembly is 24 volts at 1100 amp hours (26KW of power storage EACH), the assembly is made up of 12 two volt lead acid cells that weigh a couple hundred pounds each and each steel assembly is a bit bigger than a washing machine, I charged these using an engine powered DC welder and all the cells are good, they are several years old but will likely still work fine for many more years if cared for correctly. This kind of deal is pretty common in industrial areas, especially now as small businesses are being forced out of business. The fellow I got these from had bought two complete fork lifts, the batteries, and 2 huge battery chargers for $600.00, he wanted the hydraulics and wanted the batteries out of his way, still trying to get rid of the chargers, to heavy to ship so they don't get bids on ebay, not even 1 dollar. check your local industrial auction sales.
Another option I have considered that eliminates the battery bank and power converter all together is to use a much cheaper smaller existing gasoline generator to directly power a conventional, or custom well insulated frig or freezer, or any other normal electric appliance, in real time. Instead of the thermostat in the frig controlling the refrigeration compressor directly it would control the starting and shut down of the generator, a relatively simple custom electronic control unit with a few seconds of delay would need to be built that would allow the generators engine time to come up to speed before the appliance was connected to the generator, easy enough to do, the generator would run til the thermostat clicked it off, it would not run again until it was again called for. The generator could be located about any reasonable distance from the appliance and connected to it with a heavy drop cord. With a bit more of an electronic control this one small generator could power several appliances in turn, once one appliance signaled that it no longer needed power the output of the generator would be shifted to the next appliance requesting power.This message has been edited. Last edited by: Tim c cook,
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