How many batteries and which panels for running fans 24/7?

[ks4]

I'm building a greenhouse (22' x 100') off the grid. My plan is to use 12V marine batteries to power 2 fans (for air circulation) and a blower (inflates 2 levels of plastic sheeting). I'd like to install solar trickle chargers to keep the batteries going. I believe the fans draw 2.5 amps each, and the blower draws 1. They'll be running 24/7 if possible.
Any advice on how many batteries I'll need (and specs), and which solar panels and inverters to purchase?

[Mike90250]

So, those 3 loads are about 75 watts, and in 24 hours, that's 1,800 watt hours. A pair of 6v, 200ah golf cart batteries contains 2,400 wh, so you are looking at 4 golf cart batteries. Minimum, just to run a single 24 hour day.

The real trick is, how many cloudy days do you want this to run for, and do you plan on using a generator to recharge them ?

If you get 3 good hours of solar charging sun a day, you need a 900w PV array to recharge the 4 batteries.

[Sunking]

If they draw 75 watts as Mike calculated you are looking at roughly a panel wattage of 800 to 1500 watts depending on your location, and a 12 volt 750 AH battery which is way more than two toy sized Marine batteries. Just based on panel wattage not likely this is going to be a 12 volt system as it is a fairly large system, it will have to be 24 volt minimum with 325 AH batteries weighing in around 500 pounds of lead. Ain't no trickle charger at 35 to 70 amps.

[ks4]

If they draw 75 watts as Mike calculated you are looking at roughly a panel wattage of 800 to 1500 watts depending on your location, and a 12 volt 750 AH battery which is way more than two toy sized Marine batteries. Just based on panel wattage not likely this is going to be a 12 volt system as it is a fairly large system, it will have to be 24 volt minimum with 325 AH batteries weighing in around 500 pounds of lead. Ain't no trickle charger at 35 to 70 amps.

Looks like the solar option may not be feasible...thanks for the info (I'm not too savvy with electrical). Maybe I should shift my focus more towards the batteries. I can have extra batteries charging (to swap out every 24 hours if necessary (will be a pain, but that's ok). Which batteries would you recommend (with specs)? For some reason I thought you just divided the battery's amp hour rating by the amp draw of the motors and you'd get total running hours. (see...I don't know much about this). I use a 12v battery to power a 4 wheeler sprayer...so that's the extent of my experience.
Sooo...maybe 2 golf cart batteries hooked up to an inverter, then I could plug in the 3 cords?? And change out the batteries every 24 hours?

[Wy_White_Wolf]

Do the fans really need to run 24 hours a day?

Most greenhouses that I've looked at only run the fans when the temperature gets to high. That would be when the sun shines the brightest. So you could get by with running fans solar direct. The cost of fans that can run solar direct would be less then buying batteries to power the ones you have.

The blower would still need to run 24/7 but that is only 12 watts so a much smaller load. It would be advisable to find a DC motor for the blower so you don't have the inverter wasting power.

WWW

[Wy_White_Wolf]

Looks like the solar option may not be feasible...thanks for the info (I'm not too savvy with electrical). Maybe I should shift my focus more towards the batteries. I can have extra batteries charging (to swap out every 24 hours if necessary (will be a pain, but that's ok). Which batteries would you recommend (with specs)? For some reason I thought you just divided the battery's amp hour rating by the amp draw of the motors and you'd get total running hours. (see...I don't know much about this). I use a 12v battery to power a 4 wheeler sprayer...so that's the extent of my experience.
Sooo...maybe 2 golf cart batteries hooked up to an inverter, then I could plug in the 3 cords?? And change out the batteries every 24 hours?

Running a generator to charge the batteries would be advisable over swapping them out. Hauling fuel is easier/safer than hauling batteries. Plants could use the extra CO2 produced by it to. Battery bank would have to be at least what mike suggested.

WWW

[Sunking]

KS4 it is the batteries that make it not economical. Just in battery cost alone over the cycle life is going to cost you 3 to 6 times more than buying it from your local power company. Battery cost is going to run you 50 to 75-cents per Kwh over it lifetime. Depending on where you live in the lower 48 electricity cost 7 to 15 cents per Kwh.

[ks4]

KS4 it is the batteries that make it not economical. Just in battery cost alone over the cycle life is going to cost you 3 to 6 times more than buying it from your local power company. Battery cost is going to run you 50 to 75-cents per Kwh over it lifetime. Depending on where you live in the lower 48 electricity cost 7 to 15 cents per Kwh.

Many thanks Mike, SunKing and White Wolf...you guys are great! FYI, I'm in Boise where we get pretty good sun Feb-May (when I'd need it). It would be cost-prohibitive to run power (need to go about 100 yards). Do you think this would work:
2 Trojan T-105 golf cart batteries
40 amp charge controller
4 Kyocera model 120 panels
Only run circulation fans 12 hours/day (the blower has to run 24/7)
This was suggested from another source.
I do have a generator if necessary to recharge batteries. I haven't found a DC blower motor though. The one that I have in mind is:

http://www.growerssupply.com/farm/supplies/prod1;;pgqh1095_110094.html

What do you think??

[ks4]

Many thanks Mike, SunKing and White Wolf...you guys are great! FYI, I'm in Boise where we get pretty good sun Feb-May (when I'd need it). It would be cost-prohibitive to run power (need to go about 100 yards). Do you think this would work:
2 Trojan T-105 golf cart batteries
40 amp charge controller
4 Kyocera model 120 panels
Only run circulation fans 12 hours/day (the blower has to run 24/7)
This was suggested from another source.
I do have a generator if necessary to recharge batteries. I haven't found a DC blower motor though. The one that I have in mind is:

http://www.growerssupply.com/farm/supplies/prod1;;pgqh1095_110094.html

What do you think??

My budget (if possible) is under $1k. Could you put together a shopping list that would make this work?

[Mike90250]

.... It would be cost-prohibitive to run power (need to go about 100 yards). ....

I think you need a Ditch Witch trencher to dig you a trench, lay some 1" conduit into it and pull 300' of wire.
Couple hundred for the rental, $200 for the conduit, and some 8 ga aluminum cable, and you should be fine and no worries.

Solar is not always the right answer.

[ks4]

I think you need a Ditch Witch trencher to dig you a trench, lay some 1" conduit into it and pull 300' of wire.
Couple hundred for the rental, $200 for the conduit, and some 8 ga aluminum cable, and you should be fine and no worries.

Solar is not always the right answer.

Interesting Mike...I need to look into that. Is a licensed electrician necessary?

[russ]

Interesting Mike...I need to look into that. Is a licensed electrician necessary?

Depends on state and local rules.

[SunEagle]

My budget (if possible) is under $1k. Could you put together a shopping list that would make this work?

Along with that shopping list of panels, CC and batteries you will need an inverter, wires, fusing, mounting brackets, and other hardware. I believe you will easily exceed that $1k budget.

Unfortunately if you spend less than that $1k you will end up with a system that will not meet your daily watt hour needs.

Solar battery systems are not cheap and will cost much more that finding a way to get Utility power to your loads even it they are 1000 ft away.

I just did a quick calculation and 480 panel wattage and those two Trojan batteries will not provide you enough watt hours even if you are running the fans only 12hours and the blower 24hr per day. The correct sized system will probably cost over $2k.

[ks4]

Along with that shopping list of panels, CC and batteries you will need an inverter, wires, fusing, mounting brackets, and other hardware. I believe you will easily exceed that $1k budget.

Unfortunately if you spend less than that $1k you will end up with a system that will not meet your daily watt hour needs.

Solar battery systems are not cheap and will cost much more that finding a way to get Utility power to your loads even it they are 1000 ft away.

I just did a quick calculation and 480 panel wattage and those two Trojan batteries will not provide you enough watt hours even if you are running the fans only 12hours and the blower 24hr per day. The correct sized system will probably cost over $2k.

Thanks again all. I'm going to look into extending power. If it's not possible, what would you recommend if I ditched the 2 circulating fans and just needed to power the little blower? Maybe a pair of golf cart batteries and what size panel?