New Guy - Need help with 1.5KW Off-Grid System Setup

pavzpavz Registered Users Posts: 1
Hi,

I am totally new to Solar systems and would like some help from anyone.

I would like to build the following system up: 1.5KW Off-Grid system that will supply 500W of electricity to 3 houses next to each other.

Each house is 30 square metres and uses the following:

5 x LED Lights (25 Watts)
1 x TV (70 Watts)
1 x Fridge (180 Litres) (140 Watts)
2 x Plug Points for charging mobile phones (50 Watts)

Total Load per house = +- 285w - 400w

Total load for 3 houses= +- 855w - 1200w

Is it possible to split the power to three houses with the above mentioned load?

Please can someone help me with the components necessary to build up a system like this if its possible.

Would really appreciate all the help.

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: New Guy - Need help with 1.5KW Off-Grid System Setup

    Welcome to the forum.

    First up we need to get some terminology straight. Off-grid systems are measured in terms of the Watt hours they can supply. So whereas the loads may add up to 285 Watts, you also need to know how long each of those loads will be on in order to calculate the total Watt hours consumed.

    An example: the refrigerator may well use 140 Watts when it is running, but it might run 1/3 of the time for the whole day or 8 hours total. 140 * 8 = 1120 Watt hours. That is a lot different from 1200 Watts.

    Second it is possible to run three houses from one inverter, but it may not be practical to do so. For one thing you have distances between houses to consider. Even though the power equipment would be at one location and the wiring between locations would be 120 or 240 VAC there are losses in wiring. That may become impractical; by the time you get to house #3 under full load you could be either using very large wire or suffering significant Voltage drop.

    Another thing is those Watt hours again. As they add up the amount of stored capacity required (battery bank size) and array for recharging becomes larger and larger. It may be impractical or undesirable to have one huge central battery bank and array. Plus there is an added bonus to having redundant systems in case one fails.

    Again, you first need to get the Watt hours 'nailed down'. The best way to do this is to measure each item in question's actual consumption with a Kill-A-Watt meter under real usage conditions. This may not be practical for a 'raw install' where nothing has been purchased and/or there's no AC source to power them. However, the closer you can come to that sort of data the more accurate the system design will be.
  • offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
    Re: New Guy - Need help with 1.5KW Off-Grid System Setup

    The first question is how many hours do you need to supply this load. We need to know the watt hours of use to even be able to start a design. The refrigerators alone would use 3.4 kwh per day. This is about what I use for my whole house each day. Its going to be a large and expensive system. If all of the items you listed are on all day your looking at over 31kwh per day.
    Ned
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Re: New Guy - Need help with 1.5KW Off-Grid System Setup
    pavz wrote: »
    Hi, I am totally new to Solar systems and would like some help from anyone.

    But you have some general electrical knowledge?
    I would like to build the following system up: 1.5KW Off-Grid system that will supply 500W of electricity to 3 houses next to each other. Each house is 30 square metres and uses the following:
    5 x LED Lights (25 Watts)
    1 x TV (70 Watts)
    1 x Fridge (180 Litres) (140 Watts)
    2 x Plug Points for charging mobile phones (50 Watts)

    So three fridges and sundry bits and peices. At a ball park this puts you into quite a bit bigger system than 1.5kWp.
    Total Load per house = +- 285w - 400w
    Total load for 3 houses= +- 855w - 1200w

    Off grid, the battery acts as a go between, thus you dont power the houses from pv direct. The simple reason for this is that pvs only produce significant power for 4 'sun hours' or so a day. Yep, only 4 hours.
    Is it possible to split the power to three houses with the above mentioned load?

    Ditto to what Coot said. However there are also advantages to centralisation as well. It will cost less for starters, 3 times bigger gear, but 3 times less is usually cheaper. Design, installation, maintenance will all be shared. Finally it potentially isnt 3 times bigger, because of the 'electrical diversity factor', eg idle periods in one house can be used by another house.

    A lot of the design decisions boil down to real life limitations and opportunitys. For instance where abouts are the good roofs, facing the right way, uncluttered with chimneys, vents etc. Is there a long cable leg somewhere? Is there a convenient shed to store the gear?....etc. See what im getting at, real world factors can make or break a design. Sure you can always throw boat loads of money at a thing, but if we were going to do that we would just pay the 30K or whatever the power co. is asking to run power out.

    If you really want to do it yourself, id say that you have a biggish learning curve ahead of you. "Just caus it isnt grid connected doesnt mean it wont kill you, or burn your house down."
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • mmagmmag Solar Expert Posts: 57 ✭✭✭✭
    Re: New Guy - Need help with 1.5KW Off-Grid System Setup

    Four hours of significant sun?
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: New Guy - Need help with 1.5KW Off-Grid System Setup

    I think the original poster is from South Africa (or there about). Using the SolarEnergyHandbook for Cape Town ZA, fixed array:
    [h=3]Cape Town
    Average Solar Insolation figures[/h] Measured in kWh/m2/day onto a solar panel set at a 56° angle (from vertical):
    (For best year-round performance)

    Jan
    Feb
    Mar
    Apr
    May
    Jun



    7.27

    7.12

    6.52

    5.54

    4.43

    4.15



    Jul
    Aug
    Sep
    Oct
    Nov
    Dec


    4.30

    4.78

    5.69

    6.49

    7.00

    7.12



    They have some pretty good sun in the region--And can get better if in the dry inland areas.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Re: New Guy - Need help with 1.5KW Off-Grid System Setup
    mmag wrote: »
    Four hours of significant sun?

    Its counter intuitive i know, but if you look at a 24 hour plot of a typical array, it looks like a bump on an otherwise flat road. (and that bump rarely coincides with your peak demand). Thats not to say that PV produces nothing outside that peak, but STC "sun hours" is an internationally recognised way to describe full sun hour equivilants. So when we say 4 sun hours it actually means something like 2.5 hours at max output, 2.5 hours at 1/3 output, and another 2.5 hours at 1/10 output.

    But its a common mistake to assume that if theres 8 hours of sun then youll get 8 hours of output. This sort of thing helps yeild a realistic design, and a happy system.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • mmagmmag Solar Expert Posts: 57 ✭✭✭✭
    Re: New Guy - Need help with 1.5KW Off-Grid System Setup

    this site shows peak sun hour in southern ca at 5.5 peak sun hour yearly average, http://solarexpert.com/solar-electric/performance-factors/
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: New Guy - Need help with 1.5KW Off-Grid System Setup

    Do not rely on maximums or averages for sun hours on a panel; always plan for the minimum, otherwise that is the time the battery doesn't get charged.

    This is why we talk about "hours of equivalent good sun".
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