Building new Off Grid Home in Panama

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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Bulding new Off Grid Home in Panama
    Is there a thread about 48 VDC, or a primer that I can read to understand the differences between 48-24-12 VDC.

    Cheers

    no there isn't as it is fairly straight forward. in a nutshell higher voltages mean lower current flows for the same wattage loads and would be less losses for the same gauge wires. often higher voltage can allow smaller gauge wires to be used with smaller voltage drops or even longer distance capabilities in cases where, for example, instances of better solar locations for pvs are farther away physically. of course, higher voltage raises the bar on safety to a small degree as higher potentials are higher risks. many have ac power in the hundreds of volts and know it is to be respected. smaller dc potentials represent smaller risks excepting where sustained arcs can cause problems due to the nature of dc potentials.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Bulding new Off Grid Home in Panama

    In general, if you want to power DC appliances directly, 12 or 24 volt appliances are more available.

    However, given that inverters are not that expensive and (on average) will only cost you ~15% extra power usage (85% efficient), I suggest that it is, overall, easier to use 120/240 VAC inverters and very efficient AC appliances instead.

    You have several limiting issues with electrial power distribution. First is voltage drop... With a 12 volt system you have about 0.5 to 1.0 of voltage drop that can be allowed in a system (~11.5 volt minimum battery voltage under load, 10.5 volt typical DC cutoff for many loads). Add that it takes a huge amount of current to sustain larger 12 volt loads (i.e., 10-20x as much current vs 120-240 VAC system).

    My suggestion is to limit maximum DC current flow in a system to ~100 amps nominal maximum. If the current gets higher, you are talking about very heavy copper cables, switches, breakers, etc. This means ~1,200 watts maximum load for 12 volt bank, 2,400 watts for 24 volt system, and 48 volt for larger system.

    For example, a simple 12 volt 1,200 watt AC inverter system should be on a branch circuit of:
    • 1,200 watts * 1/10.5 battery cutoff voltage * 1/0.85 inverter eff * 1.25 NEC wiring+breaker derating = 168 amp rated branch circuit (round up to 175-200 amp or so wring+components)

    And say you want to send it 10 feet (one way trip, many voltage drop calculators use round trip length, so be careful):
    • 1,200 watts * 1/10.5 battery cutoff voltage * 1/0.85 inverter eff = 135.5 amp max current

    Using a generic voltage drop calculator for 10' one way, 0.5 volt drop maximum > 2 AWG wire minimum

    Using NEC table (very conservative), you would need around 1/O to 4/O cable (depending on insulation, conduit fill, etc.).

    Note that most good AC inverters can support ~2x rated output as surge current (motor starting loads, etc.), so surge current can easily be 2x rated current (AC inverters do not have anywhere near enough on-board storage capacitors to supply this sort of surge energy).

    Say you did the same thing at 48 volts (1,200 watts), the current will be 1/4 as much (~85 amp minimum branch circuit) and 10' of wire+2 volt drop would only need the wire to be ~8 AWG cable. And NEC table would use ~4 to 3 AWG cable (note that every 3 AWG size change is ~2x as much copper and ~2x the price per foot of cable). The difference between 4 AWG and 4/O is about 10x the cost per foot.

    Add that many DC appliances have a fairly narrow operating voltage range (for "car type" appliances, around 12-14.2 volts) vs the range required for an off grid deep cycle battery system (around 10.5 to 15-16 volt maximum), it is usually easier to use a single AC inverter than to fight all of the various DC appliance voltage ranges/limits. (15/30/60 volts is not really high enough battery high voltage limit--many people, especially in cold climates where cold batteries require higher charging voltages have to turn off their AC inverter/loads when equalizing at 15-16 volt ranges or their inverters fault).

    The above issues are complex and a simple "rule" may not address all of the local issues for a system. That is why I suggest a paper design (or a few designs) to see what works best for you.

    But for most people, they would be better off with as high of battery bank voltage (24 or 48 volts) as they can justify--12 volt system are really only for very small systems where there is not much peak power required.

    And the costs to go to higher voltage systems can be an issue... Most AC inverters at 24 and 48 volts are much larger and more expensive (not many high function 48 volt inverters smaller than a few kWatts). Good quality MPPT charge controllers can support 12-48 volt (or even higher in some cases) battery banks. A 60 amp charge controller can handle a 4x larger array on a 48 volt battery bank vs a 12 volt battery bank (note, array sizing is my "cost effective" maximum array suggestion--always read manuals for details on supported arrays/battery banks):
    • 60 amps * 14.5 volts charging * 1/0.77 panel+controller deratings = 1,130 watt array on a 12 volt bank
    • 60 amps * 58.0 volts charging * 1/0.77 panel+controller deratings = 4,519 watt array on a 48 volt bank

    So, while you may pay for for a large inverter, you may pay less for a charge controller.

    Lots of trade offs to make designing your system (and, as always, knowing your loads and lots of conservation is a very good start). In other countries, it may be difficult to find very efficient AC appliances, but in the US (North America, Europe), the Energy Star rated (and equivalent) appliances do not consume much more power than their DC equivalents (for example refrigerator/freezers), and the AC versions can cost 1/4 the price and last longer (so adding a couple solar panels and upping the battery bank AH capacity a bit are easily cheaper than the DC version of the appliances).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Bulding new Off Grid Home in Panama
    Is there a thread about 48 VDC, or a primer that I can read to understand the differences between 48-24-12 VDC.

    In addition to what Niel [edit: and BB.] mentioned, there are a few other considerations. Suppose you wanted to use 225 AH golf cart batteries. Eight of them in series (48 volt) has the same energy storage as two strings of four (24 volt), but has the great advantage of being just one string.

    If you have a shorted cell in a 48 volt system you can reprogram your charge controllers to work with a 46 volt bank. You can set the low voltage cutoff on you inverter 2 volts lower. The loss of 2 volts on a 24 volt system is harder to adjust for, and on a 12 volt system it cannot be adjusted for.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama

    Thanks to all for the info. Second time replying, got logged out.

    Understand the wiring size advantage of a higher voltage system, still believe that going a bit bigger if one can is always beneficial.

    Did some digging on the internet and found a lot of your old posts. Here is what I have come to understand.

    Watts is Watts is Watts (Icarus). This is a recurring theme (wonder why). Now I'm understanding the logic behind the load analysis for larger systems.

    From a post example:

    200 AH battery in a 12 VDC system: 100 AH * 12 VDC = 1200 Watt-Hrs
    200 AH battery in a 48 VDC system: 100 AH * 48 VDC = 4800 Watt-Hrs

    Using a system efficiency of 75%, the 12 VDC system is ~900 Watt-Hrs, and the 48 VDC system is ~3600 Watt-Hrs.

    Having absorbed this information, the battery bank AH size now only relates to the amount of Watt-Hrs available, and the AH draw does not affect the operation of the system (?).

    Also read about the rule of "13", nice little conversion estimate.

    Have been gathering power data, but of late, the grid has gone down when I'm in the middle of my data gathering, frustrating, but I will persevere.

    Now feel like I'm getting a grasp on where I am going. What say you?

    Cheers
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama

    Bill

    Will start to digest your info.

    Cheers

    Ernest
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Bulding new Off Grid Home in Panama

    Efficiency of each energy conversion device is not that bad (between 80 and 95%)... However, when you have multiple conversions, the over all efficiency is terrible. For example:

    0.81 Solar Panel Marketing rating * 0.95 Controller efficiency * 0.80 Flooded Cell Battery eff * 0.85 AC Inverter Eff = 0.52 = 52% end to end system efficiency

    Terrible--Right?

    These are "typical numbers". A battery bank that is cycling deeply can be > 90% efficient. A large inverter running 24x7 with small loads 20 hours a day, can be 60% efficiency (when lightly loaded).

    If you do DC power, you save the 85% inverter losses (but have 3% losses, or more, for wiring losses).

    If you run loads during the day when the sun is up, you can avoid the 80% efficiency battery losses.

    Keep your panels clean, you might get 5% better efficiency (near equator, you can mount panels flat, but then they don't self clean in rain. So you may have dust/leaves to clean off to keep panels at peak power. Or tilt to 5 degrees and have some self cleaning action).

    Tilting panels to follow the sun (at equator, tracking the sun is not usually as helpful compared with being closer to the poles.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama

    Bill

    The roof pitch that I am dealing with is a 3-12 pitch giving about 14 degree rise. Have been looking at the sun travel in the last few months. The sun now sets in the middle of the house instead of at the end of the house. Mentioned this to a fellow here and he said it will set further north until the summer equinox, then start back south until the winter equinox. Really neat to watch, very pronounced down here. Still get ~12 hours daylight.

    Right now, looking solely at 120 VAC wiring throughout. The LED lights are here, but with the GU-10 fitting. Have to find the adaptors. Haven't ruled out 12 VDC circuits in the future.

    We have discussed when to operate the heavy load items and we both agree early morn. We get up between 6 and 7 in the morning.

    Just finished a run on the washer. 0.18 kWh in 35 minutes. We do laundry - air dry once every three days.

    Going to head into Panama City soon to see what is available here. Buy here at a higher cost or ship equipment in, maybe a zero cost benefit, will see.

    Cheers

    Ernest
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama

    Thanks to everyone so far for sharing your expertise and valuable information. You definitely make a person dust off the cobwebs, and dig deep for information and understanding.

    Lots more to learn, back to the research.

    Cheers
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama

    Bill

    "(so adding a couple solar panels and upping the battery bank AH capacity a bit are easily cheaper than the DC version of the appliances)." Using this as a starting point, with a 48 VDC system, using deep cycle batteries that I can carry, move, etc, would have a battery bank of ~225 AH. Having larger batteries like the L16 style, would give ~390 AH. This would give:

    195*48*.75 = ~7020 Watt-Hrs (wonder what the price difference would be).

    Haven't looked at the solar panel requirement except for the solar packages at Altestore - off-grid residential 2.94kW package. Used this as a starting point, number of panels and batteries, inverter, charge controller, and such. They have a package inverter-charger Magnum MS 4400W, 48V Inverter/Charger and Midnite Solar Classic MPPT charge controller. Some place to start.

    Read somewhere on this site where the Midnite Classic can also control appliances.

    Thanks again for the info. more to follow as I digest all the information.

    Cheers

    Ernest
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama

    Here are some more pictures of the house and areas of interest.

    Picture of the house from the front. Rear walls are at height.

    Attachment not found.

    Kitchen sink area. Everything in the walls, may change in the future, but not too soon.

    Attachment not found.

    Rear of house at 1600. Notice the tree shadows are below the roof level. Gives me a warm and fuzzy that there is still full sun on the roof area.

    Attachment not found.

    Battery location. Tube extending out will be cut and run in the wall, then concreted in. The base level is at the top of the first row of brick that is seen. The length of the cable run is between 15 and 20 feet.

    Attachment not found.

    Another picture of the back at 1700. Still no shadows too high on the wall.

    Attachment not found.

    Cheers
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama

    Grounding/Bonding of Off-Grid System

    Went on line and looked for commissioning of the battery bank for an off-grid system and came across this interesting forum:

    http://forum.solar-electric.com/showthread.php?18334-Wiring-the-bank&highlight=commissioning+battery+bank

    Read through the posts and found it quite interesting. Will be doing more research into it, but thought about my experience on a boat and the requirements of Transport canada and ABYC.

    In a house the neutral and ground are joined together. Now we start adding a DC system to provide 120 VAC through an inverter. If you do not join 120 VAC and 12 VDC together on the boat, can be the same as a house. This is because 120 VAC systems will not be energized while away from the grid.

    When we bought our first boat had lengthy discussions with a transport canada electrical inspector. Told him what I was doing and he told me that I had to ensure that the 120 VAC neutral and ground were separate and not tied together on the boat 120 VAC system and that the 120 VAC and 12 VDC grounds were to be connected on the boat. There is also bonding of the various fixtures on the boat to ground as well.

    Very skeptical at first, but it works and works well.

    Now for the off-grid house. Could one not say that it represents the same configuration as a boat? if so, then a person should isolate the neutral and ground of the 120 VAC wiring, and connect the 120 VAC ground and 12 VDC grounds together.

    You would then have all grounds tethered together, batteries, house fixtures-appliance, and panel array to an external grounding rod (grounding rod - floating in water - same thing).

    Even when you might have to hook up to the grid again, there would be no change to the system. Marinas and boats are connected this way.

    I would think this would be an elegant solution to the grounding discussion.

    Any thoughts?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Bulding new Off Grid Home in Panama

    A house is not a boat because a house has Earth ground available all around it. Use it to make the system safer: bond the neutral to ground (if you can) and the ground to Earth. That way you have only the hot potential of one wire, no need to use double breakers on 120 VAC lines so that both wires go "dead" in the event of a problem.
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama

    Have put some numbers together for load analysis. Looking at the numbers, I have to remind myself that this is the worst case if everything was operating at the same time. I have alsAttachment not found.Attachment not found.o put in loads like the washer as a daily requirement, knowing that this is not the case. The biggest draw is the fridge and it's supposed to be an energy star appliance. Have a look. I was also surprised at our electric Oral-B toothbrushes. 1.3W rating on the stand, came back as 2.5W from the Kill-a-Watt meter. More work to be done.

    First chart is house appliances:

    Attachment not found.

    This Chart is for lighting:

    Attachment not found.

    This chart is for fans:

    Attachment not found.
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama

    Redid the load analysis and have got it down to between 4.8 kWh's/day and 5.3 kWh's per day with the change to the fans from 120 VAC to 24 VDC.

    Have started looking into system configurations, and have narrowed it down to either a 48 or 24 volt system. One aspect of our system is that we will be using 24 VDC fans because of wire size and length of wire runs. To use a 48 VDC system would need a step down transformer 48 to 24, but have not been able to source one.

    The 48 VDC system is with 24 2V-660 AH AGM batteries with 16-305W panels with the appropriate inverter/charger, Midnite Solar Classic charge controller, and the respective parts and pieces. An elegant system giving ~11 kWh's/day - a bit over kill. The second option for the 48 VDC system is to use 8 L16-380 AH AGM batteries giving ~6.9 kWh's/day with 10-305W panels.

    The 24 VDC system is 12 2V-660 AH AGM batteries with 8-305W panels with the appropriate inverter/charger, Midnite Solar Classic charge controller, and the respective parts and pieces, no requirement for a step down transformer. Don't believe I can have a 24 VDC system of sufficient size without using 2V batteries unless batteries are paralleled. So far I have not read anything positive about paralleling batteries at higher voltages or size.

    I would like to put in a 48 VDC system as it is better for wire size, and no need to change panels in the future with an upgrade to 48 VDC (no telling what the technology will be like).

    A question to the forum: does anyone know of a source for a 48 to 24 VDC step down transformer?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Bulding new Off Grid Home in Panama

    You can not step down DC with a transformer. You need a DC to DC converter; a type of buck converting power supply. Most of them are for 24 to 12 Volt, but some of the forum members have come up with links to 48 Volt -downwards converters before. Or you can use an MPPT controller and second battery, but that gets expensive too.
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Bulding new Off Grid Home in Panama
    A question to the forum: does anyone know of a source for a 48 to 24 VDC step down transformer?

    All transformers are AC. You need a DC to DC converter, such as this, but with appropriate voltages. They're likely to be 90% efficient.

    However, if you have 24V DC loads and use AGM batteries (so that your system will not experience higher equalization voltages bad for the loads), I would go with 24V system instead.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Bulding new Off Grid Home in Panama
    A question to the forum: does anyone know of a source for a 48 to 24 VDC

    A company called 'Solar Converters' makes them:
    http://www.solarconverters.com/index.php/products/84-dc-dc-step-down-controllers-ppt/163-ppt-48-10-rxx

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Surfpath
    Surfpath Solar Expert Posts: 463 ✭✭✭
    Re: Bulding new Off Grid Home in Panama
    Redid the load analysis and have got it down to between 4.8 kWh's/day and 5.3 kWh's per day

    Just a couple of wee observations reegarding your appliances power usage spreadsheet:
    Coffee Maker 0.450 kwh/d
    [again, as we chatted earlier, there other non electrical ways to make good coffee. But perhaps this is one of those 'must-have' items. We all have them]

    Toaster 0.188 kwh/d
    [ok - but there are gas ovens with great toasters]

    DVD 0.036
    [laptop?]

    iPad Player 0.225 kwh/d
    [charge this in the car?]

    (Electric) Tooth Brush 0.120 kwh/d
    [use an old fashioned toothbrush?]

    Bdrm Clock 0.144 kwh/d
    [battery operated clock]

    Fridge 3.119 kwh/d
    [it seems like you measured the wattage of the fridge and multiplied it by 24 hrs, ie 130watts x 24 = 3.119. Using a killawat meter you'd usually measure fridge power consumption over a few days. You'll be glad to hear that your fridge will draw way less kwh/d because it does not cycle all the time. For example, my fridge operates at 120watts but it uses about 1.3kwh/d. That's an average of 54 watts continuously.

    Washer 0.180
    [we use quite a lot of power on the washer, but run it during the weekend, when it's sunny]

    T-Zone Exerciser 0.010
    [? - not much power used here, OK]

    Rice Cooker 0.240
    [like the coffee maker - you can use the old fashioned 10 minute way on the gas stove]

    TV 0.178
    [pretty reasonable]

    Total Power Consumption 4.711
    Overall, I think you could probably easily lower your estimated house appliance consumption on paper, and in reality, to about 1.5-2.0 kwh/d. With an energy * fridge perhaps significantly lower. There are lots of folks on this forum who seem to do fine on 700-1200 watt hrs/day. Also, as I am learning, power load managagement is important (ie. if you get to run loads during the day you dont have to rely on a large battery bank to get you through the night).
    Hopefully some of this is good news for you. -SP
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Bulding new Off Grid Home in Panama

    "Fridge 3.119 kwh/d
    [it seems like you measured the wattage of the fridge and multiplied it by 24 hrs, ie 130watts x 24 = 3.119. Using a killawat meter you'd usually measure fridge power consumption over a few days. You'll be glad to hear that your fridge will draw way less kwh/d because it does not cycle all the time. For example, my fridge operates at 120watts but it uses about 1.3kwh/d. That's an average of 54 watts continuously."

    if this is the case this is in error as a refrigerator does not run 24/7. they cycle and if you want an accurate kwh reading then use the cumulative kwh portion of the meter. start it at a certain time and stop it the next day at the same time noting the total kwh the meter reads. if your refrigerator cycles at 50% then the kwh will be 1/2 of what you calculated. this can also vary if usage varies, ie, going in and out of the refrigerator more than usual.
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama

    Used the Kill-A-Watt to get readings from the fridge.

    With the ice maker on (I know extravagant - bought the fridge before we started this project - new 3 months ago) the readings were:

    3.65 kWhrs in 28.9 hrs
    6.89 kWhrs in 52.31 hrs
    8.5 kWhrs in 68.58 hrs

    Doing the math equates to ~3.1 kWh's/day.

    With the ice maker off the readings are:

    1.98 kWhrs in 19.2 hrs
    3.99 kWhrs in 38.57 hrs
    6.61 kWhrs in 63.01 hrs

    The math for this is ~2.4 kWh's/day. Everything counts.

    Also looked at the 120 VAC fans load. I shaved a significant amount of load by going to 24 VDC ceiling fans. Fan usage is estimated and down here it's all about humidity.

    Here is the table on fans:

    fans qty volts watts OT Watt Hrs

    LR/DR 2 120 VAC 0.06 12 1.440
    MBDRM 1 120 VAC 0.06 2 0.120
    Master Bath Rm 1 120 VAC 0.06 1 0.060
    Master Bath - Exhaust 1 120 VAC 0.05 1 0.050
    Guest Bdrm 1 120 VAC 0.06 2 0.120
    Guest Bath Rm 1 120 VAC 0.06 1 0.060
    Guest Bath - Exhaust 1 120 VAC 0.05 1 0.050

    Total 1.900

    LR/DR 2 12 VDC 0.015 24 0.720
    MBDRM 1 12 VDC 0.015 12 0.180
    Master Bath Rm 1 12 VDC 0.015 1 0.015
    Master Bath - Exhaust 1 12 VDC 0.015 1 0.015
    Guest Bdrm 1 12 VDC 0.015 2 0.030
    Guest Bath Rm 1 12 VDC 0.015 1 0.015
    Guest Bath - Exhaust 1 12 VDC 0.015 1 0.015

    Total 0.990

    Difference 0.910

    Assumptions Guest bedroom is used sparingly
    Master bedroom fan may be utilized more
    When guests show up need to use more power

    Agree with all the suggestions, there are ways to conserve and we have been discussing them. My load analysis also took into account worst case scenario from what I could estimate. We do not use the washer every day, but it is included, we use it every 3 to 4 days and have 2 small loads and use mother nature to do the drying. The rice cooker has not been used for 5 days now and the Mrs has said she can go back to the old fashioned way. Have a Samsung Smart TV that will not turn on, DVD not being used, don't miss it that much, and keeps the TV turned off. The Oral-B tooth brushes do a better job on the old choppers - hard to give up and I don't think the Mrs will. The iPad player is just for music, needs to be plugged in to work, no battery. The iPad uses it as an external speaker system. We are looking for gas stove tops that have a griddle for toast and such.

    The Mrs researched the T-Zone Vibration Medical Technology Machine as an option for keeping the old muscles exercised considering the lack of amenities that we were used to up north. Have a browse, here's a link: http://www.linktogoodhealth.ca

    Starting to research AC options. Hot down here as well as humid.

    Thanks for all the suggestions. Have one or two more iterations to look at, a slightly larger 2VDC battery - 915 AH instead of 660 AH. This may need a couple extra panels, and possibly another combiner and charge controller. Looking at cost benefit, cycling as well. Gives ~2 kWhrs/day more battery power, to me this means less draw down on the batteries per day, and possibly increase longevity.

    Cheers

    Ernest
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Bulding new Off Grid Home in Panama
    the math equates to ~3.1 kWh's/day.

    That's on the high side. Perhaps because your ambient temperature is too high.

    It is possible that getting a more efficient fridge may be cheaper than running this one.
  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Bulding new Off Grid Home in Panama
    NorthGuy wrote: »
    That's on the high side. Perhaps because your ambient temperature is too high.

    It is possible that getting a more efficient fridge may be cheaper than running this one.

    I agree that a more energy efficient fridge could say you plenty of power usage. The ~ 18 cu ft fridge I am using uses about 0.55 kwh per day, although ambient temperature is usually between 15 and 20 C. It is a model similar to this one here: http://www.kenmore.com/shc/s/p_10154_12604_04668802000P
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Bulding new Off Grid Home in Panama

    Re the Oral B: is it possible to use it for 3 - 4 days and then plug it in to recharge.

    In essence it is probably on float all day except for a short bulk/Absorb cycle, thinking in FLA speak.. may be some savings there too.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama

    We're looking at 25 to 33 degree C, rather warm here. We have discussed our options of selling this one and seeing what is on the market. I agree, there has to be more efficient out there. One issue we have here is that this is Panama, lots of things sold, not too much in the way of service. A person's choice is also limited if you live outside Panama City.

    Another issue we have right now is we are renting a house that has no attic insulation, and no roof vents. It gets boiling in the early afternoon. Our new house will have roof vents and attic insulation. Builder did not want to do this but we convinced him he should. He's from Ontario and should know that these two items are critical for keeping heat out of a house, can't do much about the block construction.

    Another issue down here is that the local population likes to relieve you of your belongings. The builder did not put decorative grates on the windows and doors, and as such, you have to close everything up so as to minimize a possible loss, but this comes with the house heating up - catch 22.

    Enough of the rant, will be investigating our possibilities. It is a nice fridge though.

    Cheers

    Ernest
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama
    westbranch wrote: »
    Re the Oral B: is it possible to use it for 3 - 4 days and then plug it in to recharge.

    In essence it is probably on float all day except fro a short bulk/Absorb cycle, thinking in FLA speak.. may be some savings there too.

    We want this project to work and are open to all aspects of conservation.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Bulding new Off Grid Home in Panama
    Another issue we have right now is we are renting a house that has no attic insulation, and no roof vents. It gets boiling in the early afternoon. Our new house will have roof vents and attic insulation.

    Putting solar panels on a roof is a great way to cool the attic. The panels are going to get hot anywhere you put them, but they might as well be used to shade the roof. Be sure to leave 6 inches of space between the panels and the roof for air circulation (which keeps the panels cooler than they would be without the air circulation).

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Bulding new Off Grid Home in Panama

    A good refrigerator is something that is hard to part with, depending on what it is, it'll be a good decision. I had a late 90's GE profile 25 cf that had custom Cherry door fronts, it was the crown jewel of a kitchen re-model. I could not think of getting rid of it, until I ran the numbers on what it used in power everyday. The one I have now is a little smaller, 21 cf, but uses 1/3 as much power.
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama
    vtmaps wrote: »
    Putting solar panels on a roof is a great way to cool the attic. The panels are going to get hot anywhere you put them, but they might as well be used to shade the roof. Be sure to leave 6 inches of space between the panels and the roof for air circulation (which keeps the panels cooler than they would be without the air circulation).

    --vtMaps

    Wa going to leave about 2 inches, good suggestion. Had not thought about the shade aspect of the panels. Will have at least 8 on the roof.

    Cheers
  • Panamretiree
    Panamretiree Solar Expert Posts: 278 ✭✭
    Re: Bulding new Off Grid Home in Panama

    Been doing some more research so that I fully understand the system as a whole. I have seen it mentioned that a way to keep the batteries equalized (not through the charging process) is to rotate the batteries within the string. Haven't found it since but it has merit, I think. Did find a web site that talked about interconnecting multiple batteries to form one large bank at:

    http://www.smartgauge.co.uk/batt_con.html

    Interesting article but haven't quite understood the logistics yet.

    Also reading about having a battery bank that will last for say 5 days or so (reserve power so to speak) when it is cloudy or during the rainy season down here. Trying to wrap my ear around this as well.

    For a simple pump-kicker this is tough stuff.

    Had our first downpour with the drum symphony today, rather spectacular.

    Cheers

    Ernest
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Bulding new Off Grid Home in Panama
    Been doing some more research so that I fully understand the system as a whole. I have seen it mentioned that a way to keep the batteries equalized (not through the charging process) is to rotate the batteries within the string. Haven't found it since but it has merit, I think. Did find a web site that talked about interconnecting multiple batteries to form one large bank at:

    http://www.smartgauge.co.uk/batt_con.html

    Interesting article but haven't quite understood the logistics yet.

    This process will only work to a limited extent in a series string if the reason the batteries are getting out of step in terms of SOC is that some positions get the batteries hotter than others, changing the charging efficiency.
    If batteries are in parallel rather than in series, rotation makes more sense AND equalization becomes much more difficult than for a single series string. If the imbalance between batteries is great enough and you have parallel strings, you should consider equalizing them one string at a time initially. This will allow you to check that there are not underlying problems with any of the batteries in that string, and it will let you equalize with a smaller charger.

    The smartgauge article refers ONLY to parallel battery systems, with no series connections at all.
    SMA SB 3000, old BP panels.