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Author: Subject: Off Grid Construction: Advice Needed
JDCanuck
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[*] posted on 2-23-2020 at 12:31 PM


Hi again: My second issue is choosing an appropriate water heating system as we have exceptionally hard water supplied at about 300 ppm Calcium Carbonate equivalent. I really would like to use tankless propane heaters to reduce water wastage in warming, but understand they scale up very quickly. Not wishing to use ion exchange softeners due to water use and salt output, has anyone come up with alternative softening? I am considering using a black painted hot water supply tank to warm hot water followed by sediment filters, a small propane hot water tank to boost to 120 degrees f and blowdown taps perhaps automatically controlled at both mentioned tanks. Local hot water appliances seem to need replacing very often, at about 3 times the rate we experience up here. Any comments appreciated.

[Edited on 2-25-2020 by JDCanuck]

[Edited on 8-19-2021 by JDCanuck]
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mtgoat666
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[*] posted on 2-23-2020 at 01:19 PM


Quote: Originally posted by JDCanuck  
Hi again: My second issue is choosing an appropriate water heating system as we have exceptionally hard water supplied at about 500 gpg Calcium Carbonate equivalent.


That is really, really hard water!






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[*] posted on 2-23-2020 at 04:33 PM


Quote: Originally posted by JDCanuck  
Thanks for all the responses in here! We too are building an off grid home on the Pacific coast west of La Paz (Conquista Agraria). As we presently live in Canada, we have very little knowledge almost everything we will need to consider. Presently we are seeking info on sizing a complete solar system for this area. We will have a 2400 sq ft home, with 4 bedrooms and 3 full bathrooms and kitchen fridge, freezer and most all the appliances we use up here in Canada, including microwave and 2 burner induction stove top (110v). In addition we hope to charge at least one, perhaps 2 electric vehicles eventually. We are planning on a 5kw solar panel system to begin and anticipate 12kw eventually. The 5kw is sized for a partial build at around 1400 sq ft 2 bedrooms and 1 bathroom with 2 car garage.

With that in mind and the need for an engineered septic system, are we in the ballpark on sizing the solar system? How many AGM batteries at 48 v would we need given 351 days of solar per year? We have a small 2kw gasoline generator but could enlarge that to 4kw and have looked for Inverters with backup generator supplies.

Any input from experienced off grid owners would be greatly appreciated.
Thanks


You need one 48-volt battery. The question is: How big (amp-hours or kW-hours)? and How will it be configured? You said AGM so you could create your 48-volt battery using 24 individual 2-volt cells (batteries). Or four 12-volt batteries (which each consist of six small 2-volt cells. You need to determine your electrical needs to determine the appropriate battery size for your system.

BWOE, our 48-volt battery consists of 24 2-volt, 1200-amp/hr batteries wired in series. My goal in normal use is to limit discharge to 20% to achieve maximum life (over 3500 cycles according to the mfg.) We have a 9kW solar array to quickly recharge the batteries and run the AC in the summer. It also provides for enough output to recharge the batteries even on a cloudy day. The result is we usually only run the generator to exercise it.

But our use and needs may not match yours. I suggest you call a solar supplier who has a lot of off-grid experience and discuss your needs with them.
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JDCanuck
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[*] posted on 2-24-2020 at 01:01 PM


Thanks for that response, the main question we will face is how much load overnight, and we were planning on a 48 volt system. Batteries being the most expensive single part of our system and considering all the work being done on better storage at present, I am trying to avoid oversizing there, while at the same time avoiding running the small generator overnight.
I see you use a very well sized battery system, do you run pumps and electric fridge/freezer overnight? We wish to hold the drawdown rates overnight to less than 50% at the worst times. So far we have received very high prices on all components in La Paz, so are trying to avoid retailers there and considering importing directly.
Thanks again

[Edited on 2-24-2020 by JDCanuck]
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mjs
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[*] posted on 2-24-2020 at 03:55 PM


Quote: Originally posted by JDCanuck  
Thanks for that response, the main question we will face is how much load overnight, and we were planning on a 48 volt system. Batteries being the most expensive single part of our system and considering all the work being done on better storage at present, I am trying to avoid oversizing there, while at the same time avoiding running the small generator overnight.
I see you use a very well sized battery system, do you run pumps and electric fridge/freezer overnight? We wish to hold the drawdown rates overnight to less than 50% at the worst times. So far we have received very high prices on all components in La Paz, so are trying to avoid retailers there and considering importing directly.
Thanks again

[Edited on 2-24-2020 by JDCanuck]


We live just as we did up north. TV, lights, 2 fridge/freezer, pressure pump, etc. We had friends over for dinner last night. A lot more lights than usual (although they're all LED), in an out of fridge, etc. Battery was at 89% SOC at daybreak this morning. So I'd say the battery is oversized for our normal needs except, in summer it runs the AC overnight so we can sleep. I also have MIG and TIG inverter welders I run of my system.

You have to consider your worse case load and what compromises you are willing to make. Batteries are expensive but look around. My neighbor(s) ordered some Leoch LPS2-1350 2-volt AGM batteries for approx <$350 ea IIRC. Haven't arrived yet so I'm reserving judgement until I install them. I paid less than $500 each for my AGM batteries.

Forklift batteries are an option but most will be wet cell although there are some AGM units. Dealing with the weight of those is usually the issue but if ordered new they can be constructed with individual removable cells to make moving them easier.

Send me U2U if you want the names of some vendors. (Note: I'm not in the business or connected to any business, just have a background in electrical and mechanical construction including custom designed equipment and controls.)
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[*] posted on 2-24-2020 at 04:13 PM


Place the Batteries in an underground vault if possible, harder then to steal, they like steady temps too.




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JDCanuck
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[*] posted on 2-25-2020 at 09:48 AM


Thanks for that additional info. While we don't have underground storage we will attempt to locate our storage in as cool a spot as possible.
Jerry
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JDCanuck
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[*] posted on 7-18-2021 at 02:59 PM


Just checking back in in case anyone is still interested. System has been designed and almost completely installed now, except the backup generator. As this developed and we kept increasing the load, we went with a much larger system than originally planned. Now have the following for our fully electric home west of La Paz:

24 - 445 watt panels (10.6kw total) mounted on roof $11262,
2 - 8kw Victron inverter/chargers with associated controllers and cabling $12660
6 Pylontech 3.55 kwh lithium batteries in racks totalling 21kwh at 100% or 17.5 kwh at 80% $12288
misc. cabling, labor switching and load centers and IVA $4966

Hope others looking into solar systems can find this a bit helpful. I should point out very early this spring solar systems in general jumped rapidly due to covid supply and high demand issues and was suddenly up in price overall by about 10% within one month.
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[*] posted on 7-18-2021 at 05:32 PM


If my math is close.....you spent over 40K just for solar...wow



Mexico!! Where two can live as cheaply as one.....but it costs twice as much.....
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RFClark
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[*] posted on 7-18-2021 at 09:23 PM


JD,

We have very hard water too. We run a tankless propane water heater with a softener in front of it. We’ve had it for 6 or 7 years now. Also gas refers don't do well when it’s hot. We run a cheap Best Buy AC refer. Which is very efficient!
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[*] posted on 7-19-2021 at 08:22 AM


These newest AC refers are for sure efficient.
Any comparison on efficiency for various unit's?
Price probably would be the determining factor?
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[*] posted on 7-19-2021 at 08:51 AM


for septic check out a bio digester made by
rotoplas. widely available, and very effective.
or, just do what most in san juanico do...rely on the super sandy soils to transport to the sewage to the beach.
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JDCanuck
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[*] posted on 7-19-2021 at 10:21 AM


Quote: Originally posted by Terry28  
If my math is close.....you spent over 40K just for solar...wow


Yes Terry, seems like a lot to spend, but the alternatives were far more expensive over a 10 year period. Solar power came in at about 12% of total building costs, but petroleum based alternatives have risen far faster than we anticipated as well. Natural gas here where we are is costing us 50% more than just one year ago, and governments globally promise to keep taxing it more and more into the future. Running a power line into the property would have cost more yet, and then we would also be looking at ongoing power costs that would also be constantly rising. A reliable water supply will be the next big issue, especially in the La Paz area.
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JDCanuck
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[*] posted on 7-19-2021 at 10:29 AM


Quote: Originally posted by RFClark  
JD,

We have very hard water too. We run a tankless propane water heater with a softener in front of it. We’ve had it for 6 or 7 years now. Also gas refers don't do well when it’s hot. We run a cheap Best Buy AC refer. Which is very efficient!


Thanks RF, I decided to go with electric tank type hot water heaters to both reduce replacing fouled tankless heaters and keep everything as solar based as possible. Other owners there reported tankless heaters needing replacing within 3 years, while the electric elements are far cheaper and easier to replace when they foul up. No salt based softeners allowed as is becoming more and more common, both because of excessive water use and salt going into the septic system. We are installing a whole house TAC conditioner to attempt to reduce scaling as much as possible, so far studies show good improvements with them.
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JDCanuck
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[*] posted on 7-19-2021 at 10:35 AM


Quote: Originally posted by pacificobob  
for septic check out a bio digester made by
rotoplas. widely available, and very effective.
or, just do what most in san juanico do...rely on the super sandy soils to transport to the sewage to the beach.


Bob:We have an engineered septic system with air pump to double process (both aerobic and anaerobic) the septic and expect to reuse the effluent from it for irrigation purposes reducing our water consumption as much as possible. This system is required by local codes.
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[*] posted on 7-19-2021 at 11:19 AM


Quote: Originally posted by JDCanuck  
Quote: Originally posted by Terry28  
If my math is close.....you spent over 40K just for solar...wow


Yes Terry, seems like a lot to spend, but the alternatives were far more expensive over a 10 year period. Solar power came in at about 12% of total building costs, but petroleum based alternatives have risen far faster than we anticipated as well. Natural gas here where we are is costing us 50% more than just one year ago, and governments globally promise to keep taxing it more and more into the future. Running a power line into the property would have cost more yet, and then we would also be looking at ongoing power costs that would also be constantly rising. A reliable water supply will be the next big issue, especially in the La Paz area.


Yep, 40 grand seems about right for a solar system designed to run a modern house with modern appliances. We spent nearly that in 2005 on our off grid system. There have been additions over the years and a full battery replacement after 12 years. At that time the new tech was too expensive so we spent about 10 k on lead acid batteries which are still going strong four years later. Still, I have battery envy for some of my neighbors that have recently gone with LI batteries. My understanding is that they charge faster and can be drawn down much further than mine.

We are on the east cape so it gets a bit hotter than over on the west side. We use AC in late spring and summer, but mostly just in our bedroom. The new mini splits are so efficient that we can run our bedroom unit 24/7. Nothing like having to pull up a little blankie on your afternoon nap! We call the bedroom ICE STATION ZEBRA.

All lights have been converted to LED and other energy saving measures like the smart pool pump have been game changers. Getting better all the time.

Propane is used for cooking and water heating as well as backup generator. Instant on water heaters lasted about 6 months until we got so frustrated with them than we changed out to old fashioned tanks and never looked back.

There is no heat in the house. Never needed it. Tri-D panel construction insulates pretty well. The pila under the garage holds 6,000+ gallons, two truckloads of water. When I get just over half way down I call for a load. Never ran out.

There is some great info on this thread. I think the main takeaway for some might be that it is going to cost more than you expect. But hey, in the long run you will be the one living the dream.




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[*] posted on 7-19-2021 at 12:28 PM


Quote: Originally posted by lencho  
Quote: Originally posted by JDCanuck  

Bob:We have an engineered septic system with air pump to double process (both aerobic and anaerobic) the septic and expect to reuse the effluent from it for irrigation purposes reducing our water consumption as much as possible. This system is required by local codes.
In Mexico? :o
What entity has such codes?


if SJ has such codes regarding septic treatment, a quick trip to the beach will make it clear that those codes are not enforced.
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JDCanuck
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[*] posted on 7-19-2021 at 01:10 PM
Solar System Costs


Thanks El Jefe for that extra info. We have kept our battery sizing at the minimum as we expect this is the one area that will continue to improve costwise. As we have no LP gas except for the backup generator and alternate cooking if needed, I am pretty sure we have sized correctly. Lithium batteries did become the better choice a while back, as lead acids continued to rise in price while Lithium continued to fall and become more reliable as well. Tech advances seem to be focused mainly on this area. Recent shortages of panel constituents has driven panel pricing up, hopefully temporarily.
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JDCanuck
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[*] posted on 7-19-2021 at 01:18 PM


El Jefe: I am impressed with the life you got out of your lead acid batteries, you must have done well with the maintenance. As i calculate now, we are paying 1.5 to 2 times the price of equivalent usable storage size deep cycle lead acid or AGM, so we will be hoping to get the full rated 6000 cycles out of them to justify the extra cost. I am really hoping the environmentally superior Aquion saltwater batteries or something similar is available before we need to buy any more.
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[*] posted on 7-19-2021 at 01:40 PM


Our original batteries were 12, 4 volt Rolls top of the line 300 pounders. They cost over a grand each. The problem with running a 48 volt system like this is that if you end up needing more energy storage you have to get 48 volts more. One of my neighbors had 24 of those suckers! You can't just add another couple of batteries because it throws off the voltage.

According to my limited understanding, if you buy say, three 48 volt LI batteries and you find that you need more power you can add a forth battery no problem (except to the hit to your check book). But my neighbor just bought a single battery about the size of a back yard barbeque that is rated 48 volts for the whole thing. I don't know if he could add a smaller 48 volt battery to boost it if needed???

When we replaced I switched out to 8, 6 volt Rolls monsters and saved some money by having a bit shallower well so to speak. Hasn't been a problem.



[Edited on 7-19-2021 by El Jefe]




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