Modest Off Grid Solutions

JamesTheLess · March 21, 2007, 05:22:07 PM

I am in the Northeast. New Brunswick specifically. If I did go off grid, and used no more than 6kwh/day including battery losses, what would be the most practical way to generate the power. I see 3 different strategies, each with pros and cons, depending on how much wind might be available.

Strategy 1: Solar Power and Genset with a relatively small battery bank.
Con: less opportunities for do-it-yourself, except generator abd battery bank perhaps.
Con: solar power costs more in the North. Fuel more expensive in future.
Con: less solar power available winter, when demands are higher. (lighting, laundry)
Con: the smaller battery bank would increase battery losses.
Pro: perhaps the simplest solution.
Pro: cost of solar and fuel is partially offset by need for smaller battery bank.
Pro: backup generator has good heat recovery prospects in winter.
Pro: laundry could be done when the generator is running to reduce battery losses.

The critical issue to this strategy for only 6kwh/day is getting the size of the generator right. If the generator is too big it cannot charge the small battery bank efficiently, but it might be hard to find a smaller generator that is fuel efficient and has a reasonable life span.

Strategy 2: Small Wind Power with a relatively large battery bank.
Con: Smaller wind turbines can be less practical to get high enough above trees.
Con: It might be hard to get 25% capacity factor out of a commercial 1000w on a short tower.
Con: The low capacity factor and short tower means a larger battery bank is required.
Pro: There is usually more wind in winter, when demand for electricity is higher.
Pro: Smaller wind turbines (1000w) and towers are well suited to do-it-yourself.
Pro: A homebuilt wind turbine can be cheap, perhaps customized to site for 25% capacity factor.
Pro: The larger battery bank is costly, but would reduce battery losses for more efficiency.

The critical issue to this strategy for only 6kwh/day is whether or not you have a site with enough wind close enough to the ground for a 1 kw generator on a short tower. It is hard to justify a tower much taller than 60 feet for a small generator. It would need to be tilt-down for maintenance, and the really big storms. If it was a good site, you might be better to go to a larger turbine. See next strategy.

Strategy 3: Larger Wind Power with a more typically sized battery bank.
Con: Even a 3 kw wind turbine can be impractical to get much more than 80-100 feet above trees.
Con: Even at 100', it might still be difficult to get 25% capacity factor, unless it is custom built.
Con: With 3 kw, on windy days there would likely be more power generated than needed.
Pro: There is usually more wind in winter, when demand for electricity, and heat, is higher.
Pro: 3kw wind turbines are still well suited to do-it-yourself, though 100 foot towers might get tricky.
Pro: With 3kw and 25% capacity factor, 6kwh/day should be available, and batteries should remain well charged.
Pro: The excess power generated (12 kwh/day on average) could be used as heat and hot water.

The critical issue to this strategy is whether you have a good enough site and can built it or buy it cheap enough to justify a wind turbine larger than your electricity demand and dump the rest to hot water or space heat. This might be a particularly good strategy if you didn't have a good alternative available for hot water, such as wood fuel in winter and solar in summer, but does require a good hill or a lee shore.

That's the way I see it anyway. My first choice would be Number 3, then probably Number 1. I think wind power is generally go big or stay home, and it requires a good site. The life cycle cost of solar power is high in the North, but if your demand is small enough it is the simplest solution. Do-it-yourself projects might then focus on building and maintaining the batteries, or perhaps the super energy efficient lighting and appliances, or heat and hot water systems. Always something to do.

glenn kangiser · March 21, 2007, 05:56:04 PM

Some of this is self regulating. No solar or wind for the a while, you will run the generator for power or destroy your batteries from sulfation. Likewise a continuing discharged state of the batteries will bring on rapid sulfation. The generator is a must for battery longevity, but how much you have to run it depends on how well you do the rest of it.

My battery charging seems to be most efficient using a 3000 watt single cylinder diesel engine as far as generators go. I have 12 6v 375ah batteries in 24v series paralell so much larger than you are talking.

Wind power is about 3 times stronger 100 feet above ground - minimum 30 feet above trees than it is at ground level. I have my wind generator at 85 feet - built the tower and stood it by myself.

If in a low solar area, but better wind area then wind may be the best choice. It doesn't look like NB is a strong wind area though depending on where you are at. Cloudy and foggy days do very little for charging with solar panels.

Maybe a home brewed wave actuated generator on the shore?

March 21, 2007, 06:14:58 PM

The average wind is strong here on the Fundy shore, but only once you get up to 80m or higher. This is because there is high average wind shear due to the hills and trees, and high wind shear in Southwest winds at night due to thermal stratification. The long and the short of it for small wind is that you would need to have a bald hill, or a lee shore, or both. You would still get considerably more wind in winter, which is not a bad thing. There might be a case for combining wind and solar since wind is stronger here in winter and solar in summer but again I think if it is at all worth it to do wind it is worth it to go the whole 9 yards. Good job on the 85 footer.

If you did only need 6 kwh/day on average, and an accordingly smaller battery bank, would it still be best to use a 3000w generator? Would you be able to charge them efficiently if they only hold 18kwh or so? I was wondering if it might be worth it to buy two of those Honda 1000 and replace one each year??? I think to justify the fuel cost you would need to recover heat, which gets tricky as it is air cooled. With wind power you would need a larger battery bank, but you would not need to use the generator so often. With solar power you would want to fall back on the generator more in winter, but you would not need as large a battery bank, and so a 3000w generator might be too much to charge it efficiently.

Perhaps the practical thing is to start with the right 3000w generator, and then get a battery bank large enough that you can charge it with that generator efficiently, and then whatever wind or solar is suitable from there. It seems like there might be a better way though, if you only need 6 kwh/day. Could a small system be built around one or two of those Honda1000i ? How many hours do you think you could get out of one? Could you rig up a heat exchange off the exhaust for hot water?

JamesTheLess · March 21, 2007, 06:17:40 PM

A small stream would be ideal for 6kwh/day, but that would be too easy.

Lot's of wood available here. A small 500w steam engine running 12 h/day would be attractive for combined heat and power, but for only 6 kwh/day it would be a bother, as it would not be easy to automate. and the novelty of feeding and caring for the beast would soon wear off. Also in summer you would really only need the hot water, and even that could be had from solar in summer.

How would you build a smaller system? What about two ponds for energy storage and a small waterwheel for power generation, and wind power or a gas powered pump to move the water back uphill assuming you don't have the stream to begin with? I know it's a lot of water unless you have a really big drop, even at only 6kwh/day.

I think solar for summer, and 1/2 solar 1/2 combined heat and power in winter would be attractive. That would mean you would need to average 3 kwh/day in winter from the generator. That would be perhaps 150 hours a year with a 3000w, or 450 hours a year on a 1000w. That would be too much for the 1000w I think, perhaps even two of them, unless replacing one each year was economical. As for running a 3000w machine I guess that would make sense. You would need a larger batter bank, but it and the generator would last longer even if they did cst more. Still I think I might be inclined to try one of those little Honda's out, just to see ho long they might last. They are pretty quiet I understand. If I could go with somewhat oversized wind power I think I would go with a little Honda for backup for sure, assuming it wouldn't be needed very often. Perhaps a small solar panel to go with it, because of less wind in summer.

glenn kangiser · March 21, 2007, 07:15:47 PM

Anything you have to fool with much is a bit of a pain. Steam is time consuming and dangerous especially if not constantly tended or if not time consuming, then the automation problems will likely be more than you want to fool with for a small system. Tube boilers are much safer than regular boilers if you are going to fool with them on a small basis.

A stream with good fall would totally eliminate almost all problems. I know of several places where water power was used on a small scale. Seems you should have good water resources there.

The more you fool with trying to get water etc. up and down a hill - the more chance there is for energy loss.

How about the rust power batteries - decompose junk - I haven't done it yet but got the e-book.

http://rmrc.org/rustpower.html

Small generators esp. gas tend to not last too long. Onan is probably better than Honda, but there is more power in diesel so I got a single cylinder diesel marine engine - low speed - water cooled. It is very efficient but not currently using it as the water pump needs to be resealed.

March 21, 2007, 08:10:04 PM

I would like to see someone come out with a very small and efficient and quiet diesel.
Like 1000 watts, and water cooled so you can get your hot water from it.

In terms of efficiency, if you got 20% electricity and 40% hot water and perhaps another 10% in space heat that would not be so bad. At 1000w generated 6 hours/day that would be 6 kwh/day of electricity, about 50 gallons/day in hot water, and then some space heat. I was thinking some sort of soundproof box in an attached greenhouse might be a place for it, exhausted to the outside of course. Anyhow, all good in theory, but still more expensive than wind power, though perhaps cheaper than solar power in winter. As far as noise goes, not sure what might be better. 1000w for 6 hours, or 3000w for 2 hours.

Of course it would be better to not have to run such a beast so often, and then the heat recovery is not so important, though you would still need something for heat and hot water. When I look for some land again I will definitely look for a stream as my first choice, and wind as my second choice. Still, something very quiet and efficient at 1000w would be very nice. For heat and hot water I will manage my own woodlot, but with solar hot water in summer also. I would like my place to be small enough and well insulated to get by on as little as 2 cord, and another cord for hot water. Anything more than 3 cord is just too much work in my opinion, and takes all the fun out of it. Then perhaps I could grow hardwood, or fruit and nut trees, or just plain old woods, and get by on thinnings and what not for my fuel wood.

glenn kangiser · March 21, 2007, 08:23:23 PM

Wood gas is another option for running a generator off of although it has been recommended to go with a bit more elaborate system than the original one I found. A bit more cleanup of the gas is good.

http://www.gengas.nu/byggbes/contents.shtml
The Gengas Page

http://www.woodgas.com/
WOODGAS

http://www.fao.org/DOCREP/T0512E/T0512e00.htm
Wood Gas Engine Fuel U.N.

http://highforest.tripod.com/woodgas/woodgas.html
Wood Gas Producers

or stirling engine to burn wood and generate electricity

http://www.ucolick.org/~de/StirlingEngines.html
Stirling Engines

Stirling can be nearly silent.

John_C · March 21, 2007, 08:52:04 PM

What do you folks think of these

In my sailing days I was around a few Lister diesels like this one

Being very slow speed they would "love you long time". They were efficient fuel burners as sailboat engines but they weren't small or light.

It is my understanding they were designed to power unmanned offshore lighthouses. Fuel economy and they ability to run a LONG time unattended were paramount. I knew of several that ran 30,000 hours before a rebuild. The smallest is 6 HP @ 650 RPM (not a typo) and weighs 315 Kg., almost 700 Lbs. More info below. At 1HP per 115 Lbs. of motor they are sort of the antithesis of a Briggs & Stratton.

http://www.lovson.com/lister-type-slow-speed-diesel-engines.html

MountainDon · March 21, 2007, 10:38:40 PM

First, that Lister slow speed diesel would be very nice to have. I think the cost for a new one would be rather high tho. :'(

My thoughts, for what they're worth;
-Hydro power would be wonderful if you had a year round dependable stream with sufficient head. With purification it could also be your water supply. UV light systems work well.
-Wind power; sounds like you probably ruled that out where you are, unless you buy an oceanfront hillside.
-Steam; the novelty would soon turn to drudgery.
-Solar; probably the best bet as long as you sized the battery bank to cover your projected uses (times 2, because you will always find a use for more in the future) for a minimum of three cloudy days. And I'd modify that upwards if you experience more frequent/longer cloudy spells.
-Generator; Ideally you'd only run the generator...
[a] when you needed to power something your batteries/inverter won't handle
when you need to equalize the batteries for best longevity (monthly) That'll also be the minimum amount of exercise a genset should get for it's own best longevity.
[c] as necessary when the cloudy weather / windless skies, etc. run the batteries down to where it is no longer safe to draw power from them. (safe discharge, again for best battery life) is to draw them down to no more than 50% discharge, or best draw off 25%, leave 75% in the batteries.
I realize that at your latitude solar could be a problem in the winter unless you had an extensive panel array. So some combination of power sources may in order. Is the reason for off grid power the desire for indepence or the cost of bringing in a grid tie? For me it's both, although the grid tie cost $55K USD) is a primary factor.

One last thought on batteries; when it comes to sizing the pack it's best to err on having too large a pack, rather than too small. After the first year it's not advisable to add new batteries to an existing setup. And, I'm just curious, what's your choice for batteries bolied down to... type?

March 21, 2007, 11:26:37 PM

Question: What is your primary source of living space heat going to be?

The small Hondas have the advantage that they can be paralled to double your wattage. They are very quiet; that's in their favor. I have no idea what their MTBF rate is. A pair of them could be nice for the redundancy I suppose. But their gasoline costs will only get worse.

If you rely on a generator to frequently boost your batteries sooner or later you will over =-discharge the batteries too often, and make trouble. Been there, done that.

Whatever system or combination you choose I'd try to make it operate with as little intervention from you.

glenn kangiser · March 21, 2007, 11:42:32 PM

QuoteWhat do you folks think of these

In my sailing days I was around a few Lister diesels like this one

Being very slow speed they would "love you long time". They were efficient fuel burners as sailboat engines but they weren't small or light.

It is my understanding they were designed to power unmanned offshore lighthouses. Fuel economy and they ability to run a LONG time unattended were paramount. I knew of several that ran 30,000 hours before a rebuild. The smallest is 6 HP @ 650 RPM (not a typo) and weighs 315 Kg., almost 700 Lbs. More info below. At 1HP per 115 Lbs. of motor they are sort of the antithesis of a Briggs & Stratton.

http://www.lovson.com/lister-type-slow-speed-diesel-engines.html

That is a super little engine and fortunately it is being copied and fairly well - in India I believe at a fairly decent price. A friend has one and is happy with it. I have read quite a few good things about them. I have an old pump with one - maybe I ought to drag it up here and see what I can do with it. Next site says some of the India copies can be a bit rough but the one my friend has is nice.

http://www.kk.org/cooltools/archives/001011.php

http://www.listeroid.com/index.html

http://www.utterpower.com/listeroi.htm

glenn kangiser · March 21, 2007, 11:48:49 PM

Also, Harbor Freight has belt drive generators to go with these engines.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=45416 Performance would be reduced with less than 20 HP.

ListerD · March 24, 2007, 09:50:20 PM

Interesting thread! I've often wondered about using a Lister as a long term generator...

glenn-k · March 24, 2007, 09:56:20 PM

I thought maybe it had something to do with your screen name. Like in Lister Diesel.

I have a friend who set up a complete unit, and the old engine enthusiasts really love them. One of the links above mentioned 8000 watts at a bit over .3 gallons per hour.

glenn-k · March 24, 2007, 10:42:08 PM

I haven't run one on a generator but it worked fine on the pump I had. Very fuel efficient. I left it outside for several years so don't know what kind of shape it's in now. It's 75 miles from here.

All the stories I have heard about them have been good. I saw the one at my friends place but he didn't start it as I recall. The Harbor Freight belt drive generator is a nice looking unit but I haven't used it. They stock it in the bigger stores.

The low 650 rpm running speed can be geared up to generator speed with proper ratio pulleys (or sheaves if you prefer), and helps it to last a long time.

ListerD · March 25, 2007, 10:28:29 PM

ListerD comes from a Brit SciFi Comedy called Red Dwarf. The main character is Dave Lister, in one episode he said "It's me! Lister D" it just kind of stuck.

My only question looking at the gen head you posted the link to is that it's rated for an RPM much higher than the Lister's turn.

How would you upping the RPM's?

I would think given the flywheel weight and size that trying to turn an even larger wheel on the gen head would put too much drag on the Lister(oid). No?

glenn-k · March 25, 2007, 11:10:36 PM

It was pretty common on the old slow engines to use a large drive pulley to run higher speed equipment. In this case it would take around a 17 inch pulley on the engine and a 3 Inch one on the generator to come up to the required speed or about 5.55 to one ratio.

Seems these engines were listed with Timken type bearings so they should handle it. I didn't check horsepower so don't know if the guy quoted above had a 1 or two cylinder.

There are also 540 rpm pto generators that could be used running about a 9 to 10 ratio but the price of the generator goes up to about $800.

http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200308467_200308467

Modest Off Grid Solutions

John_C

ListerD

glenn-k

John_C

glenn-k

ListerD

glenn-k