opinions re: energy needs

1solarguy

I have lived off grid for 9 years now.I had hoped to install radiant heat but the the electrical load involved in running circulating pumps 24/7 is extremely hard to supply during the low sun months. I have decided to go with baseboard set up to gravity siphon.I have a Tarm multifuel boiler,but will use the oil side rarely.
What size is the wind turbine? The easiest way to dump the loads would be to run it into a separate tempering tank. The energy available from most home-sized mills won't heat a lot of water. Mostly it is just a convenient way to dump excess.Go to otherpower.com to see how others do it.
How big an array? When sizing, remember that the best investment you can make is in conservation. it is an investment that never stops giving.Make sure it perfectly aligned with a totally clear window. Have it evaluated with a solar pathfinder.
Solar dhw is a win-win. It can be totally grid-independant.The payback is fast. Ask more.

sandy v

opinions re: energy needs

We want to install radiant floor heat and domestic hot H2O in a new construction 4000 sq ft. home on the coast in Washington Cty, ME. The home is completely off-the-grid and we need some help choosing the best boiler for our home. We want a heating system that can use either oil or wood as fuel, and will be installing a solar&wind excess energy-dump switch to power a secondary electric low-voltage hot water heater. We also have a regular wood stove in the living room.
Here's the questions: What is your opinion of the most efficient/budget-minded hot water boiler for the home: combo wood/oil, or separate wood and oil boilers? Does anyone have experience tying a low-voltage water heater (powered by excess solar/wind energy) into a heating system that uses either two separate boilers or a combo-boiler? Our contractor suggested this site to help us make a decision. Thank you for your help!

Al Letellier_9

options

That's loaded question, Sandy. I'm in So. Maine and have seen all kinds of mixed systems, but sounds like you need and engineer familiar with this type of system or a heating contractor that's done it before. The problem with most oil/wood combos is the size and amount of water in the boiler. You lose a lot of efficiency that way, especially when using the oil side. There are all kinds of options, but one would have to study the whole house and it's heating needs, how you are going to live in it, and what comfort levels you are willing to pay for.
Sounds like a fun project. Choose your designer and installer very carefully.

Eric Smith

Re: Radiant & DHW for off grid

This may be too much to handle on a cost/efficiency stand point. I've discussed this same notion with my friends at Houseneeds.com in VT and they had some good ideas...

Use the following to generate a custom quote: http://www.houseneeds.com/shop/heatingproducts/radiantheating/radiantheatpackagestep1.asp

Best of luck!

Eric

Jamie Hall

have you investigated

another option? Using a diesel generator, liquid cooled, for your electricity -- including some electric heat -- and using the rejected heat from the coolant and exhaust water jackets as additional hot water heating? While I realise that this isn't as green and sexy as solar and wind and wood, the efficiencies are (or can be, done right) extremely high

Bob Gagnon plumbing and heating

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Bob Gagnon plumbing and heating

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Bob Gagnon plumbing and heating

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Bob Gagnon plumbing and heating

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Constantin

Hmmm...

Getting a home off-grid in ME is going to take quite a bit of work.

For one, you're going to have to insulate the place to the point where passive heating via the sun (when it makes a wintertime appearance) allows the home to capture a lot of that energy, while losing little to nothing the rest of the time. I'd put the insulation on the outside (EIFS), plenty of it, then make the interior shell high-mass (concrete) so that the whole house becomes a thermal battery.

One of the great challenges in this climate is that the insolation varies close to 80% over the course of the year; unlike some placs like Colorado, which has 300 days of sun a year and only 20% variability in insolation. Thus, if you want to heat with solar hot water , you will need massive storage and collection capacity. Ditto for PV systems.

Heating with electricity makes no sense, BTW, solar hot water has a lower cost and much higher efficiency. For the best systems, take a look at the Thermomax tubes out of England. Viessmann uses them in their Vitosol 300 series. I'd dump excess electrical into batteries. If battery maintenance scares you, opt for a AGM-style PV-cell like the SunXtender series from Concorde.

One way to cut down the cost of renewable energy systems is to supplement them with a "Marathon" and similar mini-chp system. They deliver power and heat... the perfect backup solution for whenever your solar system cannot provide enough electrical power or heat for the house. I don't know if someone makes a mini-chp yet that can run on diesel, however.

As for wood stoves, the Tarm units seem to be held in very high regard. I have no experience with them. I have been very happy with my Viessmann Vitola, though you may also consider a lower-mass condensing oil boiler like Peerless Pinnacle or Monitor FCX.

The most important consideration in all this is that you can go off grid 100% but it might require a life-style change or two. Sunfrost fridges, high-efficiency lamps, turning lights off when you don't use them, etc. I hope you and your wallet a ready for all that...

Perry_3

I have considered for years

Building a house that was off the grid.

Yes, "gravity" thermal water systems would work. The only problem is that to work well they have to be designed well. My personal guess is that I doubt there are a dozen people in the US that know how to really design a gravity hot water heating system that will really work well. Some of them are active on this site. I also note that you will be shaping the house to match the heating system design layout requirments.

Designed wrong that "gravity" hot water system will not work well - and not create a comfortable home.

It is also possible to have a boiler that runs without all the modern electronics or fans. Unfortunately, that would not be a very efficient boiler by modern standards. Does it really pay to go there?

As far as payback... Hah... Unless you live somewhere where there is no electrical grid and would have to spend a minor fortune to run wires.... There is no economic payback from using all the alternative energy systems and practices necessary to operate your house "off the grid". It is a very costly luxury to do so in initial investment and maintenance. Not to mention change in life (which a lot of people would not put up with).

That does not mean that there are not other valuable reasons to have an "off the grid" house; and I have contemplated the advantages (and disadvantages) many times. Just don't claim how economical it is.

Should I get the money I will probably have at least an "off the grid" retreat (if not my primary house). I'm just a long way from long term financial stability and excess cash right now.

Perry

Brad White

Good advice thus far....

I have heard good things about the Tarm and the notion of using gravity flow has a certain appeal. This of course means large pipes and some means of thermosiphoning especially because the floor will be level... Otherwise small circulators are necessary but of course drain your precious electrons...

Wind power may have an application in your area so you are supportive of that I am sure. It is common to "dump" the excess load to a HW tank for domestic or heating needs with priority to this or to batteries. If batteries are charged, go to water.

Solar may be diminished in your area. Many people on the coast of Maine do believe that the sun exists. It is an act of faith and best not to be a "solar denier". Ayuh.



I am with Constantin on the "thermal battery" principle. A smaller load that self-sustains (passive solar of possible) is such a great place to start.

One thing I would be very cautious with is the use of electronic controls with off-grid power. I love the Viessmann Vitodens (gas fired, not an option for you) but was warned that off-grid power was detrimental even with good surge suppression. Not sure if that can be overcome in some way, but the "keep it simple" approach bears repeating.

Just some random thoughts from my random mind.

Brad

Weezbo

It is not as easy as it may seem...

there are quite a few individuals "off grid" in Alaska.

each and every one of them has their own take on just what is important and what they can and cannot live with....

there are many products some old some new, if you were being totally self sufficient i can see solar DHW ,Passive air designe and energy converters in the mix. here is one product made that garners electricity off the heat plants stove pipe. check out http://www.hi-z.com

i have to mention ,that new construction, vs conversions of existing structures ,is a Lot more economical situation. *~/:)

Ragu_5

Sandy....

You have posted a great scenario, but a tough one; please bear with me on this.

My best "Off The Grid" experience was when I lived in a log cabin in the woods, had gravity water, heated with a wood stove, cut my own wood, had an ice box for a fridge, had kerosene lamps for light and had an outhouse for the rest; that worked, and worked well.

Anything beyond that level gets tougher and more expensive to achieve; hot and cold running water, central heating, central lighting, cooking, fridges, sewer etc. It all can be done, but I truly feel that one needs to answer the basic question: "At what cost?".

If it is a moral/ethical/religious issue, then there is no turning back; however, if it is an economic question, then I would suggest that it would be time to talk with independent power line companies re: the cost of bringing power in to your homesite; there ARE alternatives.

I am so glad that you came to this site; you will not be ill-served. Best. Jack


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hr

About all the wood boilers I have seen

and installed require power to run the fans. You might find a 12V fan motor to skip the inverter and the loss associated with it.

The more modern gasification boilers are now incorporating microprocessors to further increase efficiency with flue gas sensors and VS cobustion fans.

Even the basic outdoor wood burners will have at least a powered damper, some have both a damper and fan motor to drive.

It would be tough to run and control a wood boiler without some sort of powered air control. And gasification is the only way to go from my view. Theytake a bit of fan power to keep 'em running efficiently.

A solar buddy of mine (PV side) sells surplus gen sets from the military, used in some tanks. They sip diesel, extremely well built to military spec, and provide about 3500 watts. As long as the o.d. color doesn't bother you
Kubota powered from old M1 tanks he tells me.

hot rod




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jp_2

very do able

have electricians keep ALL lighting circuits separate from outlets.

this will separate lighting load from other higher load demand circuits. gives you more flexibility.

consider composting toilets to reduce water usage.

as others have said, passive solar highly insulated structure.

could use a propane frig, stove & on demand water heater, of course short shower and only summer baths .

work to minimize need for power as much as possible in design and life style, only flat panel TV's.

try to avoid things that convert ac to dc, phone chargers, laptop chargers, go direct dc to dc appliances when possible.

Larry Weingarten

Sandy...

... there is no quick and simple answer. I've just moved into a house similar to what you describe: gravity radiant heating, solar thermal and electric, micro co-gen, DC lighting, AC for bigger loads, foam core panels for all six sides of the shell, North facing for good thermal control... and the list goes on.

I'd be glad to discuss it if you feel that would be helpful.

Yours, Larry

jp_2

lighting costs?

seems if you compare the lighting costs of DC compared to AC compact florescents, you may find it more economical to run AC lights on separate circuits with a low cost dc/ac inverter. Real Goods has dc lights about $25.00 ea where I use AC compacts at $4.00 ea. and $35.00 for a 200watt inverter.

things to think about!

I think it would be best to wire the house for 120VAC, any conversion down the road would be all ready in place. if you were wired for DC then 10 yrs later try to tie to the grid, oopps ...........

WSI Joe

You can eliminate most all of the circulators if you mix your water with a motorized 4-way mixing valve with one circulator, then zone with low voltage normally open zone valves.

You would have one circ for the system, and one for the domestic water.

Just a thought.

JimH

4000 square feet?

The sheer size of the structure poses the biggest challenge. Going off-grid is much more feasible
when you're in the 1500-2000 SF range. Before getting
into the nuts and bolts of how to make it happen,
I'd strongly encourage you to take a good hard look
at your needs, and see if you can shrink your floorplan
a wee bit.

-JimH

Larry Weingarten

Just to be clear...

... the DC lighting IS fluorescent. There are electronic ballasts that run off of 24 VDC. The point is to prevent using the main inverter to power small loads as it draws 55 watts just to be awake. They are inefficient when operated at the bottom of their capability as well. The house has both 110 VAC and 24 VDC circuits as needed. At 24 volts, the wiring is the same 12 gauge used for AC. I used 15 amp breakers on the DC circuits to keep line loss minimal. Hopefully, over time and for this house, it will clearly make even less sense to tie into the grid.

Getting the permit took a long time. I got to thing about all these details for years ;~)

Yours, Larry

Perry_3

Hmmmm... Line losses

So what does 15 amp breakers have to do with keeping the line loss minimal... Nothing!

Line loss is a function of voltage and wire resistance. Because your wire resistance is fixed.. by the size of the wire. It is a direct function of voltage (and an inverse function at that). 24 V circuits will have a line loss over 4 times that of a 120 V circuit. AC or DC.

Now if you had installed - say 8 guage wiring to your 24 V recepticles and lighting to reduce your wire resistance... you could have dropped your line resistance and made a difference...


The very reason utilities transmit large quantities of power at 345 - 750 KiloVolts is to reduce line loss. Expensive to build - but line losses are absolutely minimized. Sad but true... Almost half of all electrical generation is lost to line losses before it gets used in your appliances. The vast majority of this loss is in the local distribution circuits. 2400V to 4800V are the worst - and what is insatalled in most large cities. New communities are often installing distribution at 20,000 - 30,000 volts now. One of the places I worked took 10 years and millions of dollars to upgrade a small city from 2400 V to 13,800 - and saw their line losses drop about a factor of 5.

Low voltage DC can never be as efficient as 120 V AC. Sorry - its just the way nature works.

Perry

Constantin

Allow me to quibble a bit...

... whenever it comes to systems, I think it's important to look at system efficiency, not just the efficiency of an individual component in that system.

I have no idea what kinds of power supplies are found in AC-powered lighting ballasts, but many electronic systems convert to a "common DC" voltage before creating the final voltages/frequencies...

So, if the common voltage for a DC light ballast is 24VDC and Larry was able to eliminate the AC-DC converting stage in all his lights, then the line losses he incurrs by running his lighting circuits at 24VDC may be more than made up.

The other factor that Larry mentions (the idle power that a inverter draws) is yet another reason to have a close look at what appliances/lights to power directly with 24VDC instead of 120VAC.

It's the same reason that gas-powered fridges are popular in off-grid homes. It's not that the evap-process is efficient (because it's not). Rather, for the owner it may be more cost effective to own and maintain such a fridge than the PV bank and batteries to drive a DC-powered fridge (or, with the addition of an beefy inverter, a regular 120VAC fridge).

I'm surprised to hear that line losses account for 50% of all electrical power generation. I thought the total transmission losses came out closer to 7%.

Perry_3

No problem

I have no problem with the concept that in certain cases you may be better off with DC direct instead of AC that is converted.

If you are going to run floresent lighting that is probably true. However, the voltage required for floresent lighting is probably different than what your computer requires - so you will have losses in that conversion.

The point I was questioning was Larry's statement that somehow installing 15 amp breakers saved line losses. He could install a 100 amp breaker, a 5 amp breaker, or whatever else and not affect the line losses of the circuit. The breaker really has no effect.

Concerning electrical generation losses.

Electricity is generated at a power plant - transmitted via very high voltage transmission lines to the major cities - and the distributed to the industries and houses by a distribution system, and then transformed to the voltage your house - or business needs.

Your number you quote of 7% for transimssion losses sounds right. The vast majority of losses is in the Distribution system. Most cities were wired with 2400 V to 4800 V Distribution systems. That is the voltage that your pole (or ground mounted) transformer works from before converting it to a US target normal 115/230 V (High of 120/240:low of 110/220). Many companies will actully bring in 230V or 460 V (nominal) 3 phase and transform it down to 115 V within their building. Large industry may bring in the 2400 - 13,800 local distribution voltage direct to their plant (you can redilly buy switchgear and large motors that are designed to run up to 13,800 volts).

No one has much focused on rewiring of local distribution systems due to how costly it is - and in many cases how much disruption it would cause. It takes time to errect new power poles, string wire, put up new service transformers, and run replacement wires to a business or a house.

In many cases there may not be a good place to even put the new poles. Turning people off for a couple of weeks to a couple of months to allow replacement of a higher voltage circuit along the same path is not the most popular concept (especially since you can often replace along the same path piecemeal at the same voltage without creating more than few short disruptions).

The Municipal utility I worked at where they did this involved some forthought on requiring utility easments along certain paths decades before they were used - and also benifited from the fact that this was a fairly modest size city (perhaps 30,000 people) and rural area that was not highly congested - even downtown.

But yeh, total overall losses is about 50%. That is why most power generation is sold in the 2 - 6 cents per KWH at the plant and you pay about 2.5 times that (2 times for losses, and 0.5 times for the construction, operation, and repair of the power distribution system).

Perry

Larry Weingarten

Perry

The 15 amp breakers simply act as a limit. They in themselves could not make things more efficient, as you say. However, as I push more current through the wire it heats more. The code is concerned with wires overheating enough to start fires. I'm concerned with not wasting power, turning it into heat. By limiting the possible current draw, the wires must keep their cool ;~) And as Constantin points out, the system must be looked as a whole, both for now and later. I tried to find the balance between efficient, simple, cost and usage. It would be silly to build a house nobody else could ever comfortably live in.

Yours, Larry

sandy v

energy needs

thank you for the info; we had hoped to use the tarm multifuel boiler, but the price is cost-prohibitive right now. We may try to add-on a tarm wood boiler in the future. What has your exerience been with the tarm multi-fuel? Is it true that it only has to fire once very 24 hours to do the job?
The wind turbine we have right now is around 450W, but we are in the process of hiring a solar electrician to design and install our permanent hybrid power; solarPV/wind/diesel gen set.
We are hoping to install a large heat storage tank from the boiler, and run a low-voltage elec. hot water heater from the excess wind/solar dump switch to supplement hot H2O. Total solar DHW right now is not in our budget; the collector system is out of our price range, but we want to leave that option open for the future.
Did you run straight 120VAC wiring or DC in the house, or a combination?
One last question, what are you using for appliances? We have a temporary propane stove and fridge, a 24VDC tv/vcr, and flourescent lights wired at 120VAC.

1solarguy

Good questions

My experience with the tarm is limited. It is red, it sits in my cellar, collects dust, and screams to be hooked up.I bought it years ago slightly used,and realized that it was not going to be anywhere near a conventional hookup.The storage tank you are alluding to is a very important part of an optimized wood-boiler system.Wood boilers are by nature problematic.Its a long story,but don't consider a wood boiler without a storage tank.Everyone has good things to say about the Tarm,and wood gasification boilers in general.(except the guy who sold me his.It was 4 or 5x too big)

A 450 watt wind turbine is not going to add any appreciable amount of heat to your hot water.The heating elements in a tank are just a convenient way to dump excess electrons after the batts. are charged. You cannot simply turn off a wind turbine like you can a pv panel.If you do you will let the smoke out. A 2000 watt turbine will heat some water,though.

Don't make the mistake of getting a large genset for backup power.Unless you are also planning to run a compressor,welder,etc.Remember that in backup mode the gen. powers a batt. charger(built into your inverter),and to fully charge your batteries the load tapers to almost nothing.Generators don't like to run with no load for long periods of time.Not to mention the noise and money.

Not sure what you mean by total solar dhw.If you mean hot tap water totally heated by the sun, you're right.I live in central NH, and know that in the winter the sun is too low and the days are too short to rely fully on it. When the Tarm is firing I'll have more dhw than I can use.I have a solar dhw system that keeps me in hot water 8 mos. of the year. Scrounge the panels like I did.

My house is wired conventionally, as should yours.In addition, I wired a few 12v outlets so when I am forced to conserve more I can run a few dc lights and workstations. Flexibility is the key.

I use a Danby lpg fridge,Sears front loader clothes washer,lpg stove(needs no power),microwave,toaster,a coffee machine that gets used every morning(can't see the battery guage that early),cfl lighting(120vac)laptop computer,radio instead of tv habit,(yes,I have a stinkin' tv),solar dhw,with wood backup,etc.

Conservation is the mantra.As an investment, it never stops giving.It's manifestation has made possible off-grid houses with reasonable comfort.AS concept, it will guide social evolution, willingly or not.I believe the naysayers have not embraced this concept when they try to imagine living off-grid.After almost 10 years off-grid,I know I have come out ahead of the money curve.

I'm not sure where you are on the Maine coast,But George Bush Sr. has quite a solar setup in Kennebunkport.Not sure he embraced conservation.

Keep posting questions here. It's good for the wallies to understand how deep conservation goes,it is in all our futures.Some of these guys are running with it.Very good.

jp_2

coffee pot

a stove top operated coffee maker is a good choice.

an on-demand LP water heater might be the way to go.