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  • Urgently need help deciding on system components

    Hi everyone,

    Now that we are settled in our temporary camp on land we bought to build a straw bale-house we have been getting ridiculous quotes from utilities for provisional/temporary supplies of water and telecoms. Telecoms are all but sorted but we need electrical power and running the gennie is both noisy and expensive.

    Basically we have already lost a whole year after a car accident left me unable to do anything for a long time and recovery has been slow. Now that we are finally here and recovered a little I need to get things moving but the robbery that passes for 'public' utility here in France is something I am determined to give 'the finger' to.

    I already have 20 x 1.2v 250ah Ni Fe batteries that were originally purchased 5 years ago and never commissioned, I bought them after researching the technology and wanted to make them a part of our off grid solar setup. Now, my head isn't 100% yet, my body is getting there, I am able to do manual work albeit quite slowly but am determined to try and make this work. What I am struggling with is the plthora of equipment choices. Our hanger `(open fronted outbuilding) will eventually house the solar array, we will have 14 meters (45') of roof space which can hold the panels facing 11 degrees east of south, we have an average of 5.25 hrs of sun with an average cloudy spell of 3 days in every 8. I need suggestions for the panels, size and number, remember the NiFe batteries need a highish charge rate from time to time and generally don't suffer too much with overcharging. We will need a charge controller/inverter to supply charge to the battery bank and AC to our appliances. The charge gear and battery bank will be housed underneath the solar array, the AC and any direct DC usage will be in the house which is 30 meters (100') away and will feed into a regular consumer unit. There will be other power uses for exterior lighting which is further away but very little power required and may decide to feed directly from a small pv panel and 12v battery, total power required around 50w, all LED and one small IP camera. Our daily average requirements will be quite low too, around 14 kWh, with ample opportunity to use higher power appliances on sunnier days. A fridge freezer will be the only constant high power draw.

    My gut tells me a 3960w array, 12 x 330w panels, maybe Sun Eddison? But which charge controller/Inverter should I be looking at? There are lots of examples of installations online but of course everyone has an idea for something a little different. I would really like to here what your ideas are, the principal element of my concern is having enough juice to keep the 24v NiFe battery bank fully charged and in good health. Where to start?

    Your input would be gratefully received.

    Thank you in advance, Paul

  • #2
    because NiFe needs different charging than lead acid, you need to look for models of MPPT charge controllers (expensive) that you can adjust the setpoints.
    The inverter is going to be a problem, more than half the power in NiFe is below the common cut-off voltage for many inverters, and you need one that can be set to 20V, wihch would destroy a lead acid bank, but fine for NiFe.
    What brands of gear can you obtain ?
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

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    • #3
      Originally posted by paul29690 View Post
      ...
      I already have 20 x 1.2v 250ah Ni Fe batteries that were originally purchased 5 years ago and never commissioned, ... we have an average of 5.25 hrs of sun with an average cloudy spell of 3 days in every 8.
      your battery bank can hold 6kWh of energy which with 3 days autonomy seems you definitely need would let you use up to 2kWh / day max. This is not much at all. Normally these projects start from load calculations to come up with estimate of amount of energy required: (total sum of power consumed x number of hrs per day running) x number of days without sun.

      Then you can determine your battery bank size and then- your panels. I'd also ditch 12V wiring if possible- it causes requirement for thick wires very quickly & 12V equipment which is expensive. Please don't buy anything until you could clearly see your project to the end, these things are expensive to 'expand'.

      Comment


      • #4
        paul29690

        Will the sun actually shine on the Solar Panels from sunrise to sunset - ie no trees?

        You state, 5 Hours Solar Equiv ...
        15.8 KWH PV Production per sunny day (avg) = 3,960 Watts x 5 Hours x 80% efficiency

        So, on a perfectly sunny day, from sunrise to sunset, you will have just enough PV Production.
        But on every cloudy day = not enough
        But on every rainy day = not enough

        During the day - you need enough PV energy to run your Daytime Loads and recharge your Battery Bank.
        During the night - your Battery Bank will support your Night Time Loads.
        During cloudy days - run an Inverter style generator to recharge the battery bank during the day and then off at night.

        You did not specify your Day Time Loads or Night Time Loads.
        You need to urgently quantify ( in KWHr ) your Day Time Loads and Night Time Loads.

        Comment


        • #5
          Thanks you Mike90250, max2k and NEOH,

          Please excuse my earlier omissions. Currently I need very little power and the battery bank I have now (20 x 1.2v 250ah Changhong NiFe) should suffice, under ideal conditions 1-2kW per day will be ample, often we won;t use that much. I know I will need to add additional batteries, the Ni Fe's are now available with much higher ah ratings and are becoming cheaper as time goes on. I was looking to add a further 24v 1000ah string in around 2 years time when I will be ready to connect our new home, a small 2 person straw bale house with minimal power usage, around 8 kW per day, my workshop with intermittent usage of around 3kW per day and a small guest house with sporadic usage and minimal current draw, mainly lighting and the capability to recharge mobile devices. I am sure we can shave a kW or two form the overall figure so maximum 9kWh per day maximum. So what do I need in terms of keeping 2 x 24v or 1 x 48v battery backup, Presumably there are controllers/inverters that I could buy to suit both situations and avoid upgrading in 2 years time other than the additional batteries? If I install the 12 x 330w panels then the lower preliminary usage of 1-2kW per day should work? I should say that we are able to cut our cloth accordingly, if we have dwindling backup then we will need to curb usage, additionally summers here are hot but the type of house we are building will not require cooling or much heating so no additional power usage in the summer or winter other than additional lighting as normal.

          The panels have completely clear line of site throughout the day, we are able to control any trees that prevent that as we own all the land except for the north boundary which is the closest but of little relevance. They will be mounted 3.5m (11') above ground level and will be oriented more for the winter sun, around 42 degrees. Initially the temporary setup will be ground based, I can add panels and batteries when this transitions to the final roof mount. Daytime loads would be 75% or more with only refrigeration being 24/7, the freezer could be run through a timer so that it only runs during sunlight hours. Our last one lost only 5% overnight and was good for 54 hours before food was deemed thawed! So there are many ways to organise educed power needs. The electric water heater will consume little because it will be fed with preheated water from a 12000l heat sink which will provide underfloor heating in the bathroom and domestic hot water. Likewise spare capacity can be dumped into the heat sink along with solar heated water and an 11kW back boiler on the wood burner.

          Mike, I note you have a Listeroid, I am a great fan of the original Listers, I would be interested to know how you find your Indian copy, would be happy to take the plunge on one if hey are anywhere near as reliable as the originals. They were very popular in Africa where I lived for many years, some running 80 years or more non stop except for oil changes, they always fascinated me, would run on pretty much anything. How much do you produce with your and what are the approx running costs?

          Hope this helps, Paul

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