Best time of day for limited exposure?

SaburaiSaburai Solar Expert Posts: 32 ✭✭
Hi Gang!

What's the general consensus as to when the the most effective time of day is for charging? Although I'm in S.W. Florida and the sun is strong, at my location I've got some large palm trees that figure in to the equation. If one were forced to chose a 2-3 hour period for maximum sun when would that be? i.e. 10:00-1:00 or 1:00-3:00?

Many thanks

Rich

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,018 admin
    Re: Best time of day for limited exposure?

    In general, for parts of Florida--Afternoons may not be good for off grid solar. Summer afternoon thunderstorms/clouds and higher temperatures (lower Vmp for MPPT type charge controllers) tend to limit kWH production.

    However, for GT solar with Time of Use plans, generally summer afternoons are when you get the best return on investment (for my utility, I get paid ~$0.30 per kWH for afternoon power, and buy off peak power at ~$0.10 per kWH). So even though I might get less absolute production, I still get a better rate of return on overall production.

    You can also look at your power needs.... Power that goes from your solar panels to your loads (after battery bank is charged from overnight use), saves the ~10-20% losses of going through the battery (say you have optional loads such as irrigation--Batteries are full, turn on the pump).

    -Bill

    PS: Also check/mark polarity of cabling (red tape around positive lead from array). It does not happen often, but sometimes wiring does get mixed up. Also check Voc-panel-string too (again, verifying proper series/parallel connections).
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SaburaiSaburai Solar Expert Posts: 32 ✭✭
    Re: Best time of day for limited exposure?
    BB. wrote: »
    In general, for parts of Florida--Afternoons may not be good for off grid solar. Summer afternoon thunderstorms/clouds and higher temperatures (lower Vmp for MPPT type charge controllers) tend to limit kWH production.

    However, for GT solar with Time of Use plans, generally summer afternoons are when you get the best return on investment (for my utility, I get paid ~$0.30 per kWH for afternoon power, and buy off peak power at ~$0.10 per kWH). So even though I might get less absolute production, I still get a better rate of return on overall production.

    You can also look at your power needs.... Power that goes from your solar panels to your loads (after battery bank is charged from overnight use), saves the ~10-20% losses of going through the battery (say you have optional loads such as irrigation--Batteries are full, turn on the pump).

    -Bill

    PS: Also check/mark polarity of cabling (red tape around positive lead from array). It does not happen often, but sometimes wiring doe get mixed up. Also check Voc-panel-string too (again, verifying proper series/parallel connections).

    Thanks!

    To clarify, off grid non mobile RV 2X160W 12V GrapeSolar panels, Bogart SC-2030 & TM-2030. I've got a bit of latitude as to just where I place my panels. I've got morning sun in one area and afternoon in the other. If I'm not going to be available to shuffle the array around, which would be a better place to leave it in terms of energy production?

    Many thanks

    Rich
  • BB.BB. Super Moderators, Administrators Posts: 32,018 admin
    Re: Best time of day for limited exposure?

    Use PV Watts--Here is for Tampa, fixed array, tilted to 28 from horizontal:

    South:
    "Station Identification"
    "City:","Tampa"
    "State:","Florida"
    "Lat (deg N):", 27.97
    "Long (deg W):", 82.53
    "Elev (m): ", 3
    "PV System Specifications"
    "DC Rating:"," 4.0 kW"
    "DC to AC Derate Factor:"," 0.770"
    "AC Rating:"," 3.1 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 28.0"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:"," 9.0 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 4.56, 411, 36.99
    2, 5.21, 420, 37.80
    3, 5.72, 503, 45.27
    4, 6.52, 543, 48.87
    5, 5.92, 504, 45.36
    6, 5.56, 451, 40.59
    7, 5.46, 455, 40.95
    8, 5.70, 481, 43.29
    9, 5.32, 435, 39.15
    10, 5.41, 464, 41.76
    11, 4.83, 411, 36.99
    12, 4.24, 379, 34.11
    "Year", 5.37, 5455, 490.95


    South East:
    "Station Identification"
    "City:","Tampa"
    "State:","Florida"
    "Lat (deg N):", 27.97
    "Long (deg W):", 82.53
    "Elev (m): ", 3
    "PV System Specifications"
    "DC Rating:"," 4.0 kW"
    "DC to AC Derate Factor:"," 0.770"
    "AC Rating:"," 3.1 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 28.0"
    "Array Azimuth:","135.0"

    "Energy Specifications"
    "Cost of Electricity:"," 9.0 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 4.10, 367, 33.03
    2, 4.77, 384, 34.56
    3, 5.46, 480, 43.20
    4, 6.40, 529, 47.61
    5, 5.94, 503, 45.27
    6, 5.83, 473, 42.57
    7, 5.75, 479, 43.11
    8, 5.78, 484, 43.56
    9, 5.28, 429, 38.61
    10, 5.04, 430, 38.70
    11, 4.35, 367, 33.03
    12, 3.77, 335, 30.15
    "Year", 5.21, 5260, 473.40

    South West
    "Station Identification"
    "City:","Tampa"
    "State:","Florida"
    "Lat (deg N):", 27.97
    "Long (deg W):", 82.53
    "Elev (m): ", 3
    "PV System Specifications"
    "DC Rating:"," 4.0 kW"
    "DC to AC Derate Factor:"," 0.770"
    "AC Rating:"," 3.1 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 28.0"
    "Array Azimuth:","225.0"

    "Energy Specifications"
    "Cost of Electricity:"," 9.0 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 4.15, 371, 33.39
    2, 4.85, 388, 34.92
    3, 5.44, 475, 42.75
    4, 6.40, 528, 47.52
    5, 6.01, 509, 45.81
    6, 5.47, 440, 39.60
    7, 5.26, 434, 39.06
    8, 5.48, 458, 41.22
    9, 4.97, 403, 36.27
    10, 5.04, 430, 38.70
    11, 4.44, 373, 33.57
    12, 3.85, 340, 30.60
    "Year", 5.11, 5148, 463.32

    If it is shading (all south facing roof), you can put the yearly data into a spread sheet and blank out the AM or PM or by time of day.

    I think that somebody here has a link to a program where you can put in shading--Perhaps it will calculate solar energy there.

    In the end, solar panels need full sun... Any shading kills their output. Sun for only 1/2 the day, then you collect 1/2 the energy.

    Perhaps, if you need more energy, you will need two arrays--One for AM power, and a second for PM power. Lead Acid battery banks need as many hours of sun per day as they can get... If you cut 1/2 the time by shading--Lead Acid deep cycle batteries are going to be very unhappy... You will need a genset or other power source to get them fully charged in one day.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SaburaiSaburai Solar Expert Posts: 32 ✭✭
    Re: Best time of day for limited exposure?

    Understood. Thanks for the link. I do have inverter generator and a three stage charger. I could split my two panel array but in the end that would be the same as having half sun on both panels and more panels are not in the budget right now...
  • 2manytoyz2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Best time of day for limited exposure?

    If the palms are on your property, consider removing them, and planting shorter palms (or other small trees/bushes). Make your property work for you!

    I'm in central FL. The days vary so much throughout the year, can't say any particular time is better than another. If it storms late in the evening, it can still be overcast in the morning, clearing in the afternoon. And during the Summer, afternoons are more prone to storms, but might be clear in the morning.

    I've already had to use my grid tied Iota 75A charger a couple of times in the past two weeks, even though there are no storms. Just been very cloudy... and today it's blue skies again.

    I've removed about 15 trees on my property, and replanted several in different locations. Some blocked my South facing roof, others were too close to the house, which poses a threat to the house during storms.
  • SaburaiSaburai Solar Expert Posts: 32 ✭✭
    Re: Best time of day for limited exposure?
    2manytoyz wrote: »
    If the palms are on your property, consider removing them, and planting shorter palms (or other small trees/bushes). Make your property work for you!

    I'm in central FL. The days vary so much throughout the year, can't say any particular time is better than another. If it storms late in the evening, it can still be overcast in the morning, clearing in the afternoon. And during the Summer, afternoons are more prone to storms, but might be clear in the morning.

    I've already had to use my grid tied Iota 75A charger a couple of times in the past two weeks, even though there are no storms. Just been very cloudy... and today it's blue skies again.

    I've removed about 15 trees on my property, and replanted several in different locations. Some blocked my South facing roof, others were too close to the house, which poses a threat to the house during storms.

    Hi Robert!

    I've spent a bit of time reading your blog, you have some cool stuff!

    We don't own the property, we are "squatting" on a spot in a friend's grove and as such, can't do anything other than some minor trimming. Although I've lived year round in the area for more than 20 years, presently, we are only here for about five months in the winter, so the thunder storms (that I love) are not a problem. My little array is moveable, with about 30ft. of cable on it. I'm able to place it anywhere in the swing of the arc off of the south facing tongue of the RV.

    Many thanks

    Rich
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