We are planning a new home in Vermont. One potential property would be off-grid, and powered by PV and perhaps wind as well. Regarding a backup generator; I assume all generators produce their power DC and have built in invertors to yield AC output. I would like to buy one generator to be used during construction, but then its lifetime use would be as a backup for the PV system. By its job description (run circular saw now, and charge up the battery bank tomorrow) it seems that something in the 2-3 kW range would be adequate. A smaller generator would probably be adequate to charge the bank, but would be inadequate for the high demand startup of say an air compressor and saw at the same time. Are generators available that would produce DC output for charging the battery bank, but also have an invertor for construction? Should I just by a generator with DC output and get one of my house invertors ahead of time to rig up for construction use? Would it be more cost effective to get a cheap generator for construction and buy a separate system as a backup? I would like a system that starts automatically when the battery bank gets low.
Now, please excuse the ignorance and accept my eagerness to learn. What is natural gas? I was thinking of gas water heater as backup for wood, gas range and gas for the generator…is this something that is only available via pipes in the road? Can you bottle it up in the backyard? If I use fuel oil for the backup heat and generator, what can I use for the range? It would be nice to have one fuel on site.
Thanks.
Replies
"I assume all generators produce their power DC and have built in invertors to yield AC output. "
No.
In fact even the generators (altenators) in cars have AC and then include built in rectifiers to make DC.
That has been standard practice 30-40 years. Much less wear and moving parts.
I don't know how much you think that you will use it as for solar backup. But realize that the engine needed for a construction generator would be way oversized for the other usage.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
"What is natural gas?"
natural gas is normally delivered by pipe in the road, doubt you will have it.
LP gas is available and what is what you can expect to use. there are generators available that will run with it vice gasoline/diesel.
are you going to get enough sunlight where you'll be in Vermont throughout the year?
bobl Volo, non valeo
Baloney detecter WFR
"But when you're a kibbutzer and have no responsibility to decide the facts and apply the law, you can reach any conclusion you want because it doesn't matter." SHG
Our current electrical useage averages about 500 kWh/month. This includes range, dishwasher daily and near continuous clothes washing with five children. All appliances are energy efficient, CFLs etc., though I sure we could do some things to conserve energy. The new house would probably use LP (now that I've learned something) for the range. The dishwasher may go, or perhaps see less use, and perhaps we save laundry for sunny days. It seems that a 4-5 kWh solar system would do the job; calculations for the region of vermont we are in for 4 kWh rated show a good 490 kWh per month in the summer on such a system, but dangerously low 280 kWh in December. That is why I'm wondering about wind...perhaps it would be more cost effective to downsize the PV a little bit and supplement with wind which seems like a good match. When the sun isn't shining there's generally more wind, right? Now that I'm looking at the numbers, it doesn't make sense to do two jobs with the generator, because such a low output would be needed to charge the bank. I'm just beginning to research all of this, so set me straight where I'm off and please supply any advice needful.
If I have LP for the generator and range, could this also be used efficiently for a boiler? We will primarily heat with a central wood boiler (leaning towards greenwood) and I want somthing small that can maintain house temperature when we're away and take care of summer hot water needs. Heat loss for the house is estimated at 93 kBTU/h at -30 F. I don't know whether heat will be warmboard ($$$$), buderus wall radiators ($$), both ($$$) or convential baseboard ($ and pain).
This thread is getting long, but it has been advised to keep one home in one place on the forum. There is no building code, so I don't need automatic central heat for a CO...our goal is to keep the house at 50 F when we are away for a weekend and a cold storm blows in.
Do a google on terms like - living off grid - and off grip electrical pwoer..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I did a search on "off grip pwoer" with no luck ;)
Anyway, I've done a lot of seaches, but I appreciate the experience and advise I've gotten on breaktime.
Regarding the possible heating systems noted above, radiant floor may go easier on the fuel, but what will be easier on the electrical demand? Would a constant circulation radiant loop draw mor current than a baseboard loop?
You might check your spelling on " off grid power". You should get lots of hits.Alan
You can also have a gas clothes dryer for those days when hanging your clothes up to dry are impossible. I believe they also make gas refridgerators for people who are way off the grid and need to cut down even more on power usage. Most gas appliances can be purchased for either natural gas or liquid propane.
As for wind - you really have to look at your site. Wind is a funny thing and very site specific. Also check with officials where you are buying - not all places allow windmills, even where they make sense.
Windmills are OK, I need to evaluate for site specific when the site is known. We have brand new washer/dryer, so buying a new LP dryer doesn't seem to make sense. The washer wrings the clothes so well that large load can be dried in 20 minutes. That's maybe 1/2 kWh. So, even if I had to add an additional panel ($400 for 170 W) to make the current dryer work it would be more economical. That would require 3 hours of good sunshine (from that one panel) for every dryer load. That seems workable. We do way too much laundry anyway; what we need is a good excuse to get back to the way it used to be...these are good clothes, those are work/play clothes. You wear the latter until you can no longer determine the original color, then wash. You wear the former on special occasions when it's harder to find dirt and rarely wash.
Hmm, just ressurected memoried of my grandparent's place in central Indiana. If it was not clement enough to dry clothes on the line, in wihter they were hug on lines in the basement; in summer on the west-facing screened porch.
You mentioned batteries before. Definitely worth some googling "off grid" and "storage batteries" for a number of thoughts on the subject. Wind power really "wants" batteries to better create a uniform delivery of electricty. Otherwise, wind energy generated in times of low need doesn't "do" anything.
Living "off grid" can be a challenge. Challenges can be good for us. But, it can get a person to belt-and-suspenders backing up backups and the like. Little things like making sure the delivery truck can make it to your LP tank, and what happens if the truck does not make it.Occupational hazard of my occupation not being around (sorry Bubba)
Storage batteries are unquestionably part of the plan. It's just a matter of deciding how many amphours we want to have available. That's one reason my thoughts are drifting towards wind. If a four day storm blows through and the propane tank is empty, hopefully the wind turbine would be going like crazy! I guess I could also hook up a turbine to a five seater bicycle and give the kids something to do.....
I understand that adding to a battery bank down the road may affect its performance if batteries are of different age. Is this correct? I want the battery bank to be big enough from the beginning. That is a lot easier to calculate than the guesswork of sunshine and wind. Adding solar panels or a wind turbine as needed if we're having trouble keeping the bank full would make more sense to me.
understand that adding to a battery bank down the road may affect its performance if batteries are of different age. Is this correct?
That's exactly where I go ask my consulting EE . . . <g>
Of course I cannot find it now, but I remember a well-reasoned article on installing your battery bank in its own vault seperated from the house. The primary benefit was in never worrying about hydrogen gas leaks or the like. It also gave a structure which could help define a rainwater collection system, or an area used as a thermal mass "collector" (battery vault as one side of a deck between it and the house, for example).Occupational hazard of my occupation not being around (sorry Bubba)
We have brand new washer/dryer, so buying a new LP dryer doesn't seem to make sense. The washer wrings the clothes so well that large load can be dried in 20 minutes. That's maybe 1/2 kWh. So, even if I had to add an additional panel ($400 for 170 W) to make the current dryer work it would be more economical.
The heating element in a typical electric clothes dryer consumes 4000 watts. Whether the dryer runs for five minutes or an hour at a time, your inverter will have to be sized to handle this load, as well as anything else that is running at the same time. You will probably need to up-size your battery storage capacity as well. As others have suggested, a LP dryer is a far better solution.
Of course, you could run the dryer directly from a generator, but the generator would still have to be beefier than you would need for occasional back-up charging of your off-grid system.
Bob
hmmm, you're right, that's just too much juice to worry about even on sunny days. My wife loves this dryer, but I see that an equivalent gas model is offered by kenmore. Who would buy a used dryer all by itself though? Maybe we could sell the pair with the house and start fresh, but we would certainly be taking a loss on our recent purchase.
Who would buy a used dryer all by itself though?
Lots of folks do. People on more limited budgets buy laundry appliances as the old ones fail, not necessarily in pairs. Way back when we were apartment dwellers (more than 20 years ago), we switched back and forth between gas and electric dryers as apartment availability dictated, but kept the same washing machine until it died. You will lose a few dollars, but nothing compared to what it would cost to upsize your system. Besides, an off-grid system that is larger than otherwise necessary will not be as efficient.
Bob
Something to consider when looking for a generator that will be for a PV back up as well needed for charge equalizing your system is one that is s true sine wave . many generator are not. true sine waze allows you to charge your battery bank mor efficantly. The new honda EB generator are very good and quite!!! I live off the grid across the lake form you in NY.
Howdy,
I've lived off-grid for 30+ years. Now have a cabinet shop that is 90 percent solar.
Your stated electric consumption is very large. Any appliance that produceds primarily heat, needs to be converted to propane. A typical system runs off the battery bank until the generator starts, at which time the inverter automatically transfers loads to it and the inverter becomes a large battery charger, maybe 100 amps. It will require a LARGER generator than a construction generator as it will need good PEAK voltage, to produce adequate charging amps. My shop is set up with 240V, 7200W continuous on two stacked inverters, plus a separate 1500 W inverter for lighting. Generator is a 2-71 Detroit Diesel 15kw and when charging batteries, if I start a 3 - 5 HP motor, even this generator will momentarily (1 second or so) drop voltage enough for the inverter to stop charging momentarily, but come right back up. A small portable generato generator,6kw or so, doesn't have a chance in the setup you are describing.
Backwoods Solar has an excellent print catalog that has a great primer on off grid solar.
Lots of good advice here. I suggest you visit someone with an off the grid set up and pick their brains. There is an off the grid house near us in Whitefield Maine. The thing that struck me when we looked at it was how careful the owners are about using power. Nothing that used power in standby mode was ever left plugged in. Obviously, no electric stove, dryer, water heaters, etc. but they didn't use electric clocks or instant-on TV. Every thing that went into the house was carefully evaluated for power consumption.
After they had been in the house for a few years, we had the famous ice storm. Their neighbors had no electricity for 10-12 days, but these folks didn't miss a beat.
They only used their backup generator to test it and were extremely happy with their system. As I recall, it used two arrays in the yard, each about 5x7 feet and they manually tilted the arrays once in a while to orient them as the midday sun got higher or lower in the sky with seasonal changes. Systems are available to electrically move the arrays both vertically and east to west during the day.
They used a bank of large batteries in the basement for storage.
The system was expensive, but they were about a half mile from the nearest power pole, so the additional cost of solar wasn't too bad, given the cost of installing all those poles.
tuolumne,
I think you are approaching this in the wrong fashion.
If your goal is to live off the grid that implies a certain resistance to spending money on things like fuel.. Commendable, but requires a certain thought process.
What you really want is a system approach rather than a machine approach.
Here's how I would do it. Diesel engines, simple diesel engines will burn many things, among them is cooking oil. Coking oil is free, or I should say used cooking oil is free. Every resturant with a fryer has used oil to dispose of.. Every resturant, bar and fast food place pays to get rid of their old cooking oil.
The Chineese make some basic simple diesel engines that burn cooking oil perfectly. So do the Japaneese, and India but the Japaneese ones tend to be pricy and not imported while the ones from India are too basic and prone to unreliability..
Than it's really simple to get a big alternator and have the diesel drive the alternator. Run from the alternator to a big battery, (I recommend an electric forklift battery (used, buy it for scrap value, I'll tell you how to restore it so it should last at least another decade if you're interested)
The big battery does several things, it provides energy storage for several days so on bright sunny days when you don't use much electricity you can really store up a lot of energy, on days when the sun is reluctant to show up for work or calls in sick you can run without using the generator..
When you do use your generator you can fully charge the battery while you're working..
from the battery you get a large invertor, big enough to start your heaviest load..
It's real simple wiring, red to positive black to negative kind of wring so maintinace should be a breeze..
Free electricity! With standby power..
You might want to check out http://www.homepower.com/
It is a magazine oriented toward small scale/home brewed solar, wind, and water power systems. Over the years they have reviewed a number of solar electric components and battery maintenance information. Not all of their articles are particularly polished, some of them are pretty "backwoodsy", but you would probably find quite a bit of useful information in some of their past articles.
Real Goods has written a couple of books on aspects of home energy. They also sell a fairly complete line of solar and other home energy items. Their stuff has always seemed very pricey to me, however.
There are a number of other vendors out there and most of them seem to have some good information on their site (as well as a solicitation to buy from them, of course...)