Oregonian trying to save $50 dollars a month with a $999 system.

Xantrex C60 Charge Controller $ 175.00
Schott Poly 230, 230w 20v Solar Panel $ 590.00 (looking to add 1 more)
Samlex PST Series 1000W Pure Sine Wave Inverter, 24VDC 120VAC $335.66


$1100 + TROJAN BATTERY DEEP CYCLE AGM


lets talk about 24v vs 12v inverters?

Comments

  • russruss Solar Expert Posts: 593 ✭✭
    Re: Oregonian trying to save $50 dollars a month with a $999 system.

    Where in Oregon are you located - generality?
  • AntronXAntronX Solar Expert Posts: 462 ✭✭
    Re: Oregonian trying to save $50 dollars a month with a $999 system.

    You will save only $2-3 per month with this system, not $50.
  • BB.BB. Super Moderators, Administrators Posts: 32,015 admin
    Re: Oregonian trying to save $50 dollars a month with a $999 system.

    The OP might have high connection/billing fees...

    Anyway--What are your loads you want to run? Do you have good sun and weather (at least from ~9am-3pm)?

    For your sized system, 12 or 24 volts would be OK. If you wish to keep the costs down, 24 volts (or 48 volts) is usually a good deal as you can use smaller gauge wire because of the smaller currents in higher voltage systems.

    If you have a long wire run from the array to the charge controller, higher voltages are a good thing too... Less voltage drop / smaller wire gauge. If you have a very long wire run, you may want to look at a MPPT charge controller which can allow you to upwards of 100 VDC Vmp-array voltage (depending on brand/model of MPPT charge controller).

    A 1,000 watt inverter may be a bit small to run a full sized Energy Star type refrigerator (1,200-1,500 watts minimum recommended inverter size). But, for a cabin/part-time home, you might be better off using a propane refrigerator anyway (solar PV is most economical if the place is occupied ~9 months of the year or more).

    You might also look for inverters that have a "search" (or sleep) function. With those types of inverters, they are off most of the time and only turn on every few seconds to look for AC loads >~6 watts or so--When a load is found, then the inverter turns on full time.

    Also, for small systems, you don't want to oversize the inverter--Larger inverters have higher losses when operated at low power...

    Normally, I am a big fan of 24/48 volt battery voltage systems... But for a small system, a 300 watt 12 volt Morning Star TSW inverter is hard to beat if you do not need a lot of AC power.

    Also, what are your plans for a backup generator/charger system?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Oregonian trying to save $50 dollars a month with a $999 system.

    @ Russ portland

    @AntronX, using this calculator you seem to be right. thanks for bringing me back down to earth I got a little excited.


    $81,957.05 and im only looking to spend $1000 that will only produce 1% of my $200 a month bill



    System specifications for: Portland, OR
    Utility: Other

    4.04 kWh/sq m/day
    Avg. Monthly Usage: This is the amount of electricity you
    consume on average every month. It is
    either determined by your input or
    approximated by your electricity bill
    divided by the cost per kilowatt hour
    in your area ($0.0878/kWh). 2,278 kWh/month
    System Size: This approximation is for a system to
    produce enough electricity to offset
    50% of your yearly usage.
    It is determined by taking your avg.
    daily usage, and dividing that by your
    (solar radiance x 80%). The 80% is used
    for the inherent inefficiencies in solar
    power systems (95% inverter inefficiency,
    89% weather impact, 95% inefficiency due
    to soiling, utility, and module
    inefficiencies). 11.71 kW
    Roof Size: Approximate roof size needed to
    accomodate your solar power system
    can be deteremined by taking the
    size of the system and dividing by
    10 to get the square footage
    (10 watts/sq ft). 1,170 sq ft
    Estimated Cost: The approximate cost is an estimation
    based on a price of $7.00/watt. This is
    the average rate, including parts and
    installation, for systems above 2kW. $81,957.05
    Post Incentive Cost: The post incentive cost is an estimation
    based on the available credits/rebates for
    your area. This may include kWh
    production incentives for up to 25 years
    if applicable in your area. This provides
    an approximation of the local/state
    incentives, and should only be used as
    an approximation. $52,892.79
  • System2System2 Posts: 6,290 admin
    Re: Oregonian trying to save $50 dollars a month with a $999 system.
    Anyway--What are your loads you want to run? Do you have good sun and weather (at least from ~9am-3pm)?

    no, its oregon haha
    For your sized system, 12 or 24 volts would be OK. If you wish to keep the costs down, 24 volts (or 48 volts) is usually a good deal as you can use smaller gauge wire because of the smaller currents in higher voltage systems.

    that makes sense.
    If you have a long wire run from the array to the charge controller, higher voltages are a good thing too... Less voltage drop / smaller wire gauge. If you have a very long wire run, you may want to look at a MPPT charge controller which can allow you to upwards of 100 VDC Vmp-array voltage (depending on brand/model of MPPT charge controller).

    the system would be on a south facing roof next to the bedroom, I only want to run a PC and a TV and a xbox. sometimes all together.
    A 1,000 watt inverter may be a bit small to run a full sized Energy Star type refrigerator (1,200-1,500 watts minimum recommended inverter size). But, for a cabin/part-time home, you might be better off using a propane refrigerator anyway (solar PV is most economical if the place is occupied ~9 months of the year or more).

    my LONG term goals are off grid. I just want to get my feet wet.
    You might also look for inverters that have a "search" (or sleep) function. With those types of inverters, they are off most of the time and only turn on every few seconds to look for AC loads >~6 watts or so--When a load is found, then the inverter turns on full time.

    ohh good point! I saw some run .5amp all the time?
    Also, for small systems, you don't want to oversize the inverter--Larger inverters have higher losses when operated at low power...

    I was planning on expanding with more batteries and 3 panels.
    Normally, I am a big fan of 24/48 volt battery voltage systems... But for a small system, a 300 watt 12 volt Morning Star TSW inverter is hard to beat if you do not need a lot of AC power.

    Im gonna need some.
    Also, what are your plans for a backup generator/charger system?

    none, only want to power the electronics in my room.. rest of house will still have regular power. Honda i2000 ;)
  • BB.BB. Super Moderators, Administrators Posts: 32,015 admin
    Re: Oregonian trying to save $50 dollars a month with a $999 system.

    Yea--0.5 amp minimum draw at 12 volts (0.5a*12v=6 watts) is probably the minimum power draw of a useful sized 120 VAC inverter. "Large" inverters can draw upwards of 30-60 watts at "idle".

    The Search Mode can really cut power requirements... Otherwise, you have to get in the habit of only turning the inverter on when running an A/C load.

    It is kind of difficult to "expand" an off-grid system a bit of panel+battery at a time... Controllers/wiring/fuses/etc. are all sized to the existing need (when building a "cost effective" system). Mixing old and new batteries (and different brands/models/types of batteries) can cause issues too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Oregonian trying to save $50 dollars a month with a $999 system.

    are you looking to back up your power with the batteries for if your power is consistent then skip the batteries and shoot for a straight grid tie system. that would be cheaper and more efficient to do, but it will still be big money to invest to bring your bill down.
  • BB.BB. Super Moderators, Administrators Posts: 32,015 admin
    Re: Oregonian trying to save $50 dollars a month with a $999 system.

    You are looking to learn from your off-grid system... So, planning is where you want to start.

    First, you want to measure the loads you expect to support. For AC loads, a Kill-a-Watt meter is very hard to beat (also very good for conservation use throughout your home).

    Next, for off-grid solar, conservation (and money spent on conservation) is a better investment than "throwing" more solar PV/Batteries at the problem. Picking low power devices (Energy Star rated, laptop instead of desktop, turn off unneeded power like laser printer on standby, CFL/possibly LED lighting, etc.).

    Then you size the batteries and solar panels to support your planned loads.

    It sounds like you are on the coastal side of Oregon and can have real issues with sunlight... Basically, solar PV power needs sun and no shade. Not enough clear skies and shade free sun makes the solar system (array costs) very expensive and it can give you poor performance. There is no substitute for full sun on your solar PV panels.

    For an off-grid system, using PV Watts for Portland. A 1,000 Watt (1 kW) fixed array, 0.52 derating (off grid system), for Portland OR:
    "Station Identification"
    "City:","Portland"
    "State:","Oregon"
    "Lat (deg N):", 45.60
    "Long (deg W):", 122.60
    "Elev (m): ", 12
    "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:"," 45.6"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:"," 7.2 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 2.07, 31, 2.23
    2, 2.59, 34, 2.45
    3, 3.89, 57, 4.10
    4, 4.35, 62, 4.46
    5, 5.29, 77, 5.54
    6, 5.29, 73, 5.26
    7, 6.01, 85, 6.12
    8, 5.55, 78, 5.62
    9, 5.00, 69, 4.97
    10, 3.79, 55, 3.96
    11, 2.00, 27, 1.94
    12, 1.46, 20, 1.44
    "Year", 3.95, 667, 48.02

    That will give you around 20 to 85 kWH per month of useful power (these are 20 year average weather conditions)... Or:
    • 20 kWH per day / 30 days = 0.667 kWH per day or 667 Watt*Hours per day (December)
    • 85 kWH per day / 30 days = 2.833 kWH/day or 2,833 WH per day (July)
    So, if you have a 200 watt set of loads (1,000 watts of panels, Portland, off-grid system):
    • 667 WH / 200 Watts = 3.3 hours of run time (December)
    • 2,833 WH / 200 Watts = 14.2 hours of run time (July)
    Anyway--You are only looking at 205 watts of panels to start, so multiply the above by "0.205":
    • 3.3 hours * 0.205 = 0.68 hours (for 205 watts of panels in December)
    • 14.2 hours * 0.205 = 2.9 hours (for 205 watts of panels in July)
    So--you can see, even a 200 watt load (on a 300 watt inverter) with just one or three panels is already a pretty significant load for such a small system.

    For a "beginning system"--take a look at this thread:

    Emergency Power

    Basically a very long thread that starts from the beginning with a few vague requirements through design and assembly for a "portable" solar RE off-grid power box.

    Also, we have a thread with a bunch of information/links to various solar projects and other sources that should be an interesting starting point for somebody interested in all things solar.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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