Complete novice needing a few questions answered!!!

edd_hedd_h Registered Users Posts: 8
Hi
I'm looking into a solar system for a friend of mine that does not know how to use a computer, and I need to know peoples thoughts on a few points and also what I need to buy.......

We live in Bordeaux France
it is for a mobile home.
Right now there is an electrical input into the mobile home where everything will be.
He has been using a motor but gasoline is very expensive over here.

I've calculated that my friend will use 140W of energy for 5 hours in the evening, thats all - TV Satelite and 3 low energy bulbs! water, fridge, stove etc will be on gas.
We know that in summer we could get a system to work very easily...

My question is in winter (overcast or misty sometimes) will we be able to set up a system that will work?

We want to install solar panels (wind is not an option due to the geographical situation - in a valley with trees all around, along with batteries and converter etc


My second question is what do I need to buy if it is possible to use this system - I think most batteries are around the same price as the states, and I can buy 100w chinese panels for 188 euros each.

thanks in advance for your help on this, it will save a great deal of time and effort if you could share your knowledge!

Cheers
Edward
ps any info needed can be supplied, via response to this thread.

Comments

  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: Complete novice needing a few questions answered!!!

    My question is in winter (overcast or misty sometimes) will we be able to set up a system that will work?

    My second question is what do I need to buy if it is possible to use this system - I think most batteries are around the same price as the states, and I can buy 100w chinese panels for 188 euros each.


    Yes. I don't see a reason why not. Winter is a tricky time for anything solar.
    Is this an Recreation Van RV ? Are you using a generator ?


    Watch for Chinese quality. You're getting what you pay for.
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
    WWW.GreenAnything.Net    Ad free website.
    Lots of DIY Renewable Energy Projects on ETSY : Solar Panel builds, Wind Turbine builds, Rain Barrel build,etc.  
  • hillbillyhillbilly Solar Expert Posts: 334 ✭✭
    Re: Complete novice needing a few questions answered!!!

    Just a couple of things, by no means a complete answer to all your questions:

    First off, this is assuming that there is no other available power (grid/shore). If you're looking at 140 watts for 5 hours/day that's about 700Whrs/day which would realistically be closer to 1Kwh by the time you factor in efficiency/losses. I would personally probably want to add a bit of an assumed increase in power consumption as once you have power it's funny how many more "little things" you may end up wanting to be able to operate.
    Two factors to consider will be how low you are willing to discharge the batteries (the lower you discharge them the shorter the life span will tend to be on average), compared against how much you are willing to run your generator. You can get by in the winter on just PV, but it would take a LOT of extra panels and batteries to see you through long spells of cloudy weather. The overwhelming majority of "off grid" systems utilize a generator to augment winter charging of the batteries. Even it the fuel is expensive, it will likely be far cheaper than trying to do a fully self sufficient PV powered system.
    Using a common rule of thumb of no more than a 50% discharge over a period of 3 days of little to no sun: 1kw of power consumption would require a battery bank of about 500AH (at 12V). Again, if it were me I would probably factor in a bit more than that and shoot for a bit more... but you have to play with the numbers and decide what you can afford in terms of batteries and panels and fuel.
    As for what you'll need, the basics will be:
    PV panels
    Charge controller
    Batteries
    Inverter
    Wire, breakers/fuses, disconnects.... etc.
    I would recommend looking at getting an inverter than can also work as a charger, which allows you to charge your batteries from a generator (which you already have it sounds like).
    Just to give you a bit more things to think over
  • edd_hedd_h Registered Users Posts: 8
    Re: Complete novice needing a few questions answered!!!

    Hi
    It is a 40m "large caravan style home" - not sure if it is an RV is the US

    also I was looking at a a battery that was 6v and 25a for 8 hours - would it work if i attached 2 of these batteries to say 4 or 5 solar panels of 100w??

    Also if the chinese panels work do they not work as well, or do they need more lominisity to work are they less efficient?

    thanks
    Edward
  • edd_hedd_h Registered Users Posts: 8
    Re: Complete novice needing a few questions answered!!!

    hi sorry there was an error in the initial post - i need to supply 140w for 5 hours ........... not 700w for 5 hours!!! sorry for the confusion
    cheers
    Edward
  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: Complete novice needing a few questions answered!!!

    Sounds like an American RV equivalent. If you can drive it, yes.

    The caravan runs D/C current ? If so, then it should be easy to set up. You may need more batteries in parallel. What voltage does the Caravan run ?
    If it's a 12v system then stick with those voltage batteries. You may have to upgrade the existing battery to a deep-cycle and increase the CCA's (Cold Cranking Amps) by 20-30%.
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
    WWW.GreenAnything.Net    Ad free website.
    Lots of DIY Renewable Energy Projects on ETSY : Solar Panel builds, Wind Turbine builds, Rain Barrel build,etc.  
  • edd_hedd_h Registered Users Posts: 8
    Re: Complete novice needing a few questions answered!!!

    Hi
    No in fact it runs off 230v, it is movable but needs a convoi /permission to move it!

    I know we need to get a transformer, but do we need a lot of batteries too?
    I was planning on using 2 golf cart batteries, like hillbilly was saying.

    cheers
    Edward
  • hillbillyhillbilly Solar Expert Posts: 334 ✭✭
    Re: Complete novice needing a few questions answered!!!

    Sorry for the typo reading 1400 watts for 5hours/ day= 700wh. It should read 140 watts for 5 hours = 700 watt hours. The 700 watt hours is the total amount of power you are describing. As for the batteries, do you know what the 20 hour rating on them is, that's the more standard method of comparing deep cycle batteries. I doubt that a couple of batteries rated at 25ah (at the 8 hour rate, if I understand your post) would be nearly sufficient for your needs. You could do with say maybe 150 ah (at 12V), if you planned to run the generator any day that there was not sufficient sun. With a battery bank this size you would be drawing it down to less than 50% of capacity daily, and thus it would need to be recharged each and every day, and with a deep discharge cycle like this they would not last nearly as long on average. A bigger battery bank would allow a bit more flexibility, being able to wait a couple of cloudy days before running the generator, smaller discharges tend to prolong battery lifespan too.
  • BB.BB. Super Moderators, Administrators Posts: 29,736 admin
    Re: Complete novice needing a few questions answered!!!

    Just to be really clear:

    Watts is a Rate (like liters per hour).

    Watt*Hours is an amount (like liters)

    140 Watts is that a 140 watt load that runs for 5 hours?

    If so, then the total energy used per day:

    Energy/Work = 140 Watts * 5 Hours per day = 700 Watt*Hours per day

    If your 140 watts is really Watt*Hours, then you are telling us your average load is:

    Power= 140 Watt*Hours / 5 Hours = 28 Watts

    Either amount is possible---But for most people 28 watts for 5 hours is a very small amount of useful power (laptop computer or portable DVD Player+1 CFL lamp would be about it)...

    The difference in what you are asking will result in a system that is 5x bigger (or smaller) depending on you answer.

    One other question... What size/model/number of genset is being used...

    Many times people are using a 3-5kW genset to power 140 watt loads... That is very fuel inefficient as the genset could power upto 2-3kW worth of loads on the same amount of fuel per evening.

    Looking for an Inverter/Generator (like the Honda euX000i line) for a 1,000 or 2,000 peak watt generator could use 1/4 the amount of fuel of the bigger gensets. An eu2000i would run up to 400 watts at ~0.28 Liters per hour...

    How does that compare with his current fuel usage per night?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • edd_hedd_h Registered Users Posts: 8
    Re: Complete novice needing a few questions answered!!!

    Hi AGAIN!!

    SO on a cloudy day does anyone know what a 100w solar panel will capture?
    I would need around 700wh each day, so would need to charge my batteries at 100w per hour for 8 hours a day (allowing a little more for loss /contingency), how many 100w panels does everyone think I'd need, to use uniquely solar panels?
    thanks
    Edward
  • edd_hedd_h Registered Users Posts: 8
    Re: Complete novice needing a few questions answered!!!

    to reply to BB

    he is using way more fuel than what you were describing at the moment.
    With a hugely "stupidly large" gen!!!

    Thanks everyone for all the help I'm begining to get my head around all this/ how to economise everything!

    Cheers
    Edward
  • hillbillyhillbilly Solar Expert Posts: 334 ✭✭
    Re: Complete novice needing a few questions answered!!!

    To answer your questions:

    in cloudy weather a 100 watt panel may produce next to nothing, depends a LOT on the day.

    that 700WH is more how much you need at the power outlet, with losses and battery charging you're looking at needing a fair bit more than that. 1KWh is just a very rough estimate, but probably a good minimum for design discussion purposes. To get the actual numbers you'd need to sit down with all the specs from all the equipment, your solar insolation data, which batteries you chose to go with, and how they will be stored even.

    I don't know what your solar insolation is like off the top of my head, but a typical average is more like 5 hours of "peak sun" which is good way to measure how much a given panel might produce. So in theory your power needs *could* be met with as few as two 100 watt panels depending on how much "peak sun hours" you get there. Then there's the battery charging issues which are another factor all together, but very roughly you'll want something like 1-2 watts of PV per amp hour of battery capacity (assuming 12V, double that for 24V). This can be flexible to a point, as long as you're willing to consider the generator an integral part of your charging regiment.
  • BB.BB. Super Moderators, Administrators Posts: 29,736 admin
    Re: Complete novice needing a few questions answered!!!

    Edward, you can use the PV Watts Website to estimate a solar system's output over the year (remember, these are average numbers over, typically, several decades--so an specific month/year can have more or less than listed--sometimes by +20/-50% (such as a clear summer or bad winter).

    For Bordeaux, France. Assume 1kWatt=1,000 watts of panels (sorry, that is the smallest the program accepts). 0.52 derating (off grid and battery power--yes, works out to only 52% efficient from solar panel rating to 230 VAC at the wall outlet). Fixed panels mounted pointing at latitude (at sun over the equator--you can adjust several times a year if you want with movable mounts, etc.).

    "Station Identification"
    "City:","Bordeaux"
    "State:","FRA"
    "Lat (deg N):", 44.83
    "Long (deg W):", 0.70
    "Elev (m): ", 61
    "Weather Data:","IWEC"

    "PV System Specifications"
    "DC Rating:"," 1.0 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.5 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 44.8"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:"," 0.1 euro/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value (euro)"
    1, 2.15, 32, 0.04
    2, 2.71, 36, 0.04
    3, 3.97, 60, 0.07
    4, 4.64, 66, 0.07
    5, 4.69, 68, 0.08
    6, 5.03, 69, 0.08
    7, 5.31, 74, 0.08
    8, 5.02, 70, 0.08
    9, 5.22, 73, 0.08
    10, 3.37, 49, 0.06
    11, 2.55, 36, 0.04
    12, 1.83, 26, 0.03
    "Year", 3.88, 661, 0.75

    Ok, you can see that December is the worst month at an average of 26kWhrs per month...
    • 26kWHrs per month / 30 days per month = 0.867 kWhrs per day = 867 WH per day for December
    For summer months you will get 2x or more power because of longer days and better weather.

    You can see that even a two axis tracker (the best you could do):
    "Station Identification"
    "City:","Bordeaux"
    "State:","FRA"
    "Lat (deg N):", 44.83
    "Long (deg W):", 0.70
    "Elev (m): ", 61
    "Weather Data:","IWEC"

    "PV System Specifications"
    "DC Rating:"," 1.0 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.5 kW"
    "Array Type: 2-Axis Tracking"
    "Array Tilt:","N/A"
    "Array Azimuth:","N/A"

    "Energy Specifications"
    "Cost of Electricity:"," 0.1 euro/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value (euro)"
    1, 2.41, 36, 0.04
    2, 2.94, 40, 0.05
    3, 4.59, 71, 0.08
    4, 5.67, 83, 0.09
    5, 5.82, 87, 0.10
    6, 6.88, 98, 0.11
    7, 6.99, 101, 0.11
    8, 6.35, 91, 0.10
    9, 6.21, 88, 0.10
    10, 3.81, 57, 0.06
    11, 2.91, 42, 0.05
    12, 2.02, 30, 0.03
    "Year", 4.72, 824, 0.93

    The December value only increase from 26-30 kWhrs per month--not that much. Production in other months is greatly improved.

    Regarding battery sizing... Generally we use 3 days of "no sun" storage and a maximum of 50% discharge (longer life). Assume 85% efficient AC inverter and 700 watts of load on a 12 volt battery bank:
    • Battery AH Rating = 700 Watt*Hours * 1/0.85 * 1/12 volt battery * 3 days * 1/0.50 discharge =~412 Amp Hours...
    You could justify up to a 823 Amp*Hour battery (at 12 volts)... Outside the range of 412-823 AH (roughly) is not usually recommended for a solar system unless you have specific needs.

    It is possible to use a smaller battery--but then he would probably need to start the genset whenever there was a cloudy day or two so as to prevent falling below 50%.

    You ask how much power does a cloudy day cost? Light clouds, perhaps 50% loss of power. Heavy dark clouds/stormy weather, 90-99% loss of generation.

    Solar panels convert the energy of the sun to voltage*current=power. The current is basically proportional to the amount of solar radiation hitting the panel. Little sunlight energy, little current.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
Sign In or Register to comment.