hi guys i'm new, qustion about inverters

madmilitia
madmilitia Registered Users Posts: 4
so i want to run 250 watts worth of heat lamp for 7 to 9 hours a day in my green house, i have 244 amp hours of batteries and 150 watt's of panels, whats the cheepest way to accomplish this.

also do you guys know of any 750-1000 watt inverters that DON'T have an LOB alarm, or have an alarm volume control?

Comments

  • microage97
    microage97 Registered Users Posts: 12
    Sounds to me that you will not have enough panel watts to keep that light going. Where are you located?
  • Mountain Don
    Mountain Don Solar Expert Posts: 494 ✭✭✭
    244 amp-hours of batteries... at 12 volts? Series/parallel batteries, were AH added if in parallel? Just want to be sure the battery specs were added up correctly....

    250 watts outgoing and only 150 watts incoming. I think you will end up being quite short.

    Also is the 250 watt load happening when the sun is shining or at night?

    Need more complete data on what is happening, what is wanted.


    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • madmilitia
    madmilitia Registered Users Posts: 4
    244 amp-hours of batteries... at 12 volts? Series/parallel batteries, were AH added if in parallel? Just want to be sure the battery specs were added up correctly....

    250 watts outgoing and only 150 watts incoming. I think you will end up being quite short.

    Also is the 250 watt load happening when the sun is shining or at night?

    Need more complete data on what is happening, what is wanted.


    i have 2 122 AH batteries, set in parallel yes AH were added, running at night, yes i will be sort i need to add i know this, that's why i'm asking the below questions.

    1. whats the cheepest way to accomplish this and
    2. do you guys know of any 750-1000 watt inverters that DON'T have an LOB alarm, or have an alarm volume control?


    thanks.
  • Alaska Man
    Alaska Man Solar Expert Posts: 252 ✭✭
    you are going to need 2,000 W/H to run for 8 hours. You don't have enough battery either.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    madmilitia wrote: »
    i have 2 122 AH batteries, set in parallel yes AH were added, running at night, yes i will be sort i need to add i know this, that's why i'm asking the below questions.

    1. whats the cheepest way to accomplish this and

    If you are serious, and we don't know how long you are planning to run this, daily? or where you are, this tells us how much sun you will get and how regularly it will shine. For overnight "...to run 250 watts worth of heat lamp for 7 to 9 hours a day..." that is 2 kw hours of electric A/C with inverter inefficiencies', figure 2500 watt hours of electric DC, lead acid batteries need 15-20% more electric input than they can output, so figure 3000 watts of input.


    For the battery bank to provide 2500 watt hours of electric, you need 2500watts ÷ 12volts = 208 amps, but to provide this from a 12 volt battery bank you would have to take it down no lower than 50% and at a drain of greater than 1/20th of the capacity they will drain quicker, figure a 500 amp hour battery bank minimum and that is if you have 4 hours of sun EVERYDAY! if you don't the system will fail... In the winter time (Green house) you're less likely to get this in most areas

    Since we don't know where you lie we will have 4 hours of direct sunlight a day, panels only produce about 75% of their panel rating, so 1000 watt array should produce about 3000 watt hours of electric,
    madmilitia wrote: »
    2. do you guys know of any 750-1000 watt inverters that DON'T have an LOB alarm, or have an alarm volume control?

    Only good news I have for you, is this doesn't require a true sine inverter, so a cheap one should be fine, and if that is all you're running, a cheap auto type often only has a light, and if it has an audio it should be easy to disable....

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    If you want to store heat, an insulated tank of water is typically better than batteries.

    I am available for custom hardware/firmware development

  • madmilitia
    madmilitia Registered Users Posts: 4
    jonr wrote: »
    If you want to store heat, an insulated tank of water is typically better than batteries.
    are you talking black 50 gallon barels? cause they seem to bleed heat real fast and really i have concentrated areas that need the heat. each area has a temprature on off regulator so once the soil suface hits 50 the lamp shuts off. i think at this point i'm just pulling the inverter apart and cutting the speaker. i might add a 900 watt wind turbine.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Ok... Lets go back to the basics:

    Where (roughly) is the site located... I.e., how much sun do you get per day (average). And is the heating "seasonal" (spring hatching vs winter heating). Insulation is a big help--Lack of ventilation can hurt (humidity, CO2 buildup, etc.)... A Heat Recovery Ventilator can help save energy and increase ventilation.

    https://en.wikipedia.org/wiki/Heat_recovery_ventilation

    Also, if it is just heat and the outside air temperature is not too cold (not too far below freezing), a Mini-split Heat Pump (reversible air sourced Air Conditioner/Heat Pump) can be more efficient that pure resistive heat.

    So, to this point, conservation is a key element in the design of any off grid system. But--Say you need what you need (electrical power wise). Then the system design process would look like this:
    • 250 Watts * 9 hours = 2,250 WH per day
    Next, sizing the battery bank. For lead acid batteries, 1-3 days of energy storage is what is usually workable (for many reasons). And 50% maximum discharge for normal operation. Pick 2 days of storage as a rough "optimum" design. And for this size of battery bank, a 24 volt battery bank:
    • 2,250 WH per day* 1/24 volt battery * 1/0.85 AC inverter eff * 2 days storage * 1/0.50 max discharge = 441 AH @ 24 volt battery bank
    You could use 882 AH of 12 volt battery bank too--But the charging current is getting rather high--And the voltage drop of 12 volt wiring is difficult/costly to deal with (lots of very heavy copper cables).

    Next, charging with solar--There are two calculations here. The first is based on a 5% to 13% rate of charge (for "health of the battery bank")... 5% is OK for weekend/seasonal (summer) use, but for daily cycling, a 10%+ rate of charge is usually an easier and more reliable system (less hands on daily operation required to keep battery bank from over discharging, etc.).
    • 441 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 830 Watt minimum array
    • 441 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 1,661 Watt array nominal
    • 441 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 2,159 Watt array "cost effective" maximum
    Next is based on how many hours of sun you get... You can use something like PV Watts or the Solar Electric Handbook to estimate "hours of sun per day by month". Your hours of sun may range from 2 horus per day (deep winter, far north, marine/coastal climates) to 4 hours per day for 9+ months of the year minimum, to 5-6+ hours per day during the summer...

    If this heating system is not used in winter, and you are in a reasonably sunny region, using 4 hour per day math would look like:
    • 2,250 WH per day * 1/0.52 overall solar system efficiency * 1/4 hours of sun per day = 1,082 Watt array minimum (based on hours of sun per day).
    And there is also the question of a generator for back up power... We all gets days or sometimes even weeks to months of very poor solar conditions. The "hours of sun" calcualtors are based on long term average sun (~20 years or so of history). Your actual harvest will vary based on actual weather conditions.

    Solar power is a very expensive way to generate heat. More or less, the rough average for the cost of off grid solar power is around $1.00 to $2.00+ per kWH hour--Or roughly 10x the cost of utility power.

    For heating, frequently propane/diesel/fuel oil can be be a less costly/more reliable source of direct heat. Of course, you have to depend on fuel deliveries and variable price of fuels (location, season, world markets).

    That is a start--Your thoughts?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    If this is for something like heating soils (green house or similar), then possibly a DIY type system like this would be a possibility:

    http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/solarshed.htm

    And some other links:
    If you want a do-it-yourself kit... This one appears to be hard to beat:

    www.solarroofs.com

    Solar Guppy has many years experience with a system from them and has been pretty happy. It does require proper maintenance to keep running well and to prevent problems (like freeze damage).

    There have been a few threads here that link back to several extensive home projects--right down to installation photos, and documentation of mistakes and corrections...

    Link 1
    Link 2

    Fpllow the off-forum links. The several projects/websites highlighted are very educational.

    This is an interesting project for a solar heated shed and a control the guy now sells to support a pure DC off-grid solar heating system.

    And this one is a bit more low tech home made heating system. Also very interesting and informative.

    Between the two above links, they probably give the best detailed explanations of how to do a major home heating/domestic hot water project that I have seen.

    The second one is, by itself, probably not practical for a city home system--but both give great ideas of the scope of such projects.

    From our FAQ thread:

    http://forum.solar-electric.com/forum/solar-news-reviews-product-announcements/solar-information-links-sources-event-announcements/4426-working-thread-for-solar-beginner-post-faq?5556-Working-Thread-for-Solar-Beginner-Post-FAQ=

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • madmilitia
    madmilitia Registered Users Posts: 4
    BB. wrote: »
    Ok... Lets go back to the basics:

    Where (roughly) is the site located... I.e., how much sun do you get per day (average). And is the heating "seasonal" (spring hatching vs winter heating). Insulation is a big help--Lack of ventilation can hurt (humidity, CO2 buildup, etc.)... A Heat Recovery Ventilator can help save energy and increase ventilation.

    https://en.wikipedia.org/wiki/Heat_recovery_ventilation

    Also, if it is just heat and the outside air temperature is not too cold (not too far below freezing), a Mini-split Heat Pump (reversible air sourced Air Conditioner/Heat Pump) can be more efficient that pure resistive heat.

    So, to this point, conservation is a key element in the design of any off grid system. But--Say you need what you need (electrical power wise). Then the system design process would look like this:
    • 250 Watts * 9 hours = 2,250 WH per day
    Next, sizing the battery bank. For lead acid batteries, 1-3 days of energy storage is what is usually workable (for many reasons). And 50% maximum discharge for normal operation. Pick 2 days of storage as a rough "optimum" design. And for this size of battery bank, a 24 volt battery bank:
    • 2,250 WH per day* 1/24 volt battery * 1/0.85 AC inverter eff * 2 days storage * 1/0.50 max discharge = 441 AH @ 24 volt battery bank
    You could use 882 AH of 12 volt battery bank too--But the charging current is getting rather high--And the voltage drop of 12 volt wiring is difficult/costly to deal with (lots of very heavy copper cables).

    Next, charging with solar--There are two calculations here. The first is based on a 5% to 13% rate of charge (for "health of the battery bank")... 5% is OK for weekend/seasonal (summer) use, but for daily cycling, a 10%+ rate of charge is usually an easier and more reliable system (less hands on daily operation required to keep battery bank from over discharging, etc.).
    • 441 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 830 Watt minimum array
    • 441 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 1,661 Watt array nominal
    • 441 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 2,159 Watt array "cost effective" maximum
    Next is based on how many hours of sun you get... You can use something like PV Watts or the Solar Electric Handbook to estimate "hours of sun per day by month". Your hours of sun may range from 2 horus per day (deep winter, far north, marine/coastal climates) to 4 hours per day for 9+ months of the year minimum, to 5-6+ hours per day during the summer...

    If this heating system is not used in winter, and you are in a reasonably sunny region, using 4 hour per day math would look like:
    • 2,250 WH per day * 1/0.52 overall solar system efficiency * 1/4 hours of sun per day = 1,082 Watt array minimum (based on hours of sun per day).
    And there is also the question of a generator for back up power... We all gets days or sometimes even weeks to months of very poor solar conditions. The "hours of sun" calcualtors are based on long term average sun (~20 years or so of history). Your actual harvest will vary based on actual weather conditions.

    Solar power is a very expensive way to generate heat. More or less, the rough average for the cost of off grid solar power is around $1.00 to $2.00+ per kWH hour--Or roughly 10x the cost of utility power.

    For heating, frequently propane/diesel/fuel oil can be be a less costly/more reliable source of direct heat. Of course, you have to depend on fuel deliveries and variable price of fuels (location, season, world markets).

    That is a start--Your thoughts?

    -Bill


    my thoughts are that's alot of information. yeah sorry about that location thing i'm in colorado springs so winter time i get about 4 sun hours a day, i mean the actual amount of energy i charge in is differant cause i start out with what i have right now at about 1amp at 8 am then by noon i'm up to about 9 amps. (roughly). and it's a greenhouse so if the system fails one night it's ok, i know solar is going to be the expensive way to go. but i like playing around with it.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Using PV Watts for Colorado Springs:

    http://rredc.nrel.gov/solar/calculators/pvwatts/version1/US/Colorado/Colorado_Springs.html

    Fixed array tilted to 39+15=54 degrees for winter collection (you may want vertical if snow is a problem):


    Month
    Solar Radiation
    (kWh/m2/day)


    1
    5.19


    2
    5.54


    3
    5.82


    4
    5.63


    5
    5.23


    6
    5.27


    7
    5.18


    8
    5.66


    9
    6.09


    10
    6.16


    11
    5.51


    12
    4.84


    Year
    5.51


    You can get some very decent Winter Sun.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • hemmjo
    hemmjo Solar Expert Posts: 90 ✭✭
    I used to do installation and maintenance of commercial greenhouses. One system I installed was a soil warming seed germination bed. It was a system of tubes running on top of a 2" layer of foam. Think radiant floor heating. The growing medium was on top of the tubes, warm water was pumped through the tubes to warm the soil. Controlled by a thermostat and small pump. This water was heated by a boiler,and was pumped into the bed through a mixing valve at about 70 degrees. Solar can heat water much easier than it can make electric. It is also much better to heat plants from below than above.

    This was back in the late 70's. It would be so much easier, now with the development of all the radiant floor heating systems, and the lost cost of PEX tubing and small pumps. Use your solar electric for circulation and control.

    Good Luck,

    John
    Two systems in the Dominican Republic  http://villagemountainmission.org/
    installed Feb 2014 at 19.796189° -70.893594°, Classic 150 + WBJR, KISAE SW1210, MN Battery Monitor, IOTA DLS 55/IQ4,  4- Solar World 275w, 4-6v x 225ah Trace Batteries
    installed Feb 2015 at 19.795733° -70.893372°, same components  as above
    Honda PowerMate PC0497000, 7000/8750w generator - powers the well and chargers maybe once a week






  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    hemmjo wrote: »
    Solar can heat water much easier than it can make electric. It is also much better to heat plants from below than above.

    While this is true, often this doesn't work well for green houses, since the solar often isn't available when needed, cold front typically move in with clouds...

    The Walipina(?) or pit greenhouse can be effective for some plants, often can maintain 50 degrees or so, wood heat is carbon neutral...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • 69fasty
    69fasty Registered Users Posts: 1
    Hi. I don't know much about heat lamps or anything else but would it be possible to make a 12 volt version of one using car headlight globes. Save on inverter losses and you wouldn't have to pull yours apart