# A tree greenhouse power management question



## StillKickin (Aug 5, 2010)

I am building a 15w X 20L X 15H Ft. greenhouse, i am trying to have it almost self efficient as far as:

- a solar panel charging the 12v battery during the day.
-750 amp inverter connected to the battery
-A propane furnace keeping it at about 75F, 
-a timer to a submerged water pump in a 55 gallon drum to feed the plants
-and a thermostat to exhaust fan ( low amp).

my question is am i forgeting anything and will this work together?


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## Tex (Oct 31, 2008)

This all depends on the numbers. 

How many hours/day does the panel get sun?
How many watts is the panel rated for?
I'm assuming it's a 750W inverter.
How many watts does the pump draw and how much does it run?
How many watts does the vent fan use and how much does it run?
How big is the battery in Watt-hours? (Amp-hours times volts)

For calculations, all power can be calculated in Watt-hours, where watt-hours is Watts times hours.

A 100W solar panel getting 5 hours/day of usable Sunlight will generate 500 Watt-hours/day.

A 30W vent fan that runs for 6 hours/day will use 180Watt-hours.

Also, most inverters are about 90% efficient, so you will have to multiply your power generated by .9 to account for this.

Volts times amps = Watts

I hope my ramblings helped.


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## JeepHammer (Oct 10, 2008)

StillKickin said:


> I am building a 15w X 20L X 15H Ft. greenhouse, i am trying to have it almost self efficient as far as:
> 
> - a solar panel charging the 12v battery during the day.
> -750 amp inverter connected to the battery
> ...


OK... 
This is a evolutionary process, I learned the hard way...

Vented top! Be able to vent heat in the day time!
Heat rises, so vented roof panels are a VERY good idea.
They don't have to be fancy, but make sure they vent.

Vents at ground level for cooler air to come in when heat rises out the roof vents!
If you can't get air flow IN, then the heat won't vent!

I use a large water tank in the center of my starting/green house to store 'Thermal Mass'.
Heats up in the day time, releases heat at night to equalized temps.

I use a home made solar thermal panel,
Small pump and drill motor to power it,
And a solar panel to produce the energy for the drill.

Just about the time the sun is up enough to produce heat in the thermal (Tubes) panel, the solar cell is getting enough power to start the pump and circulate the heated water into the tank indoors.
Shuts off automatically when the sun goes down so I don't have thermal losses in the panel at night.

The tank provides circulated water/humidity in the building along with thermal mass so I can regulate temp in the building better without burning fuel.

I use CARDBOARD trays for the plants, mostly coke or beer cardboard trays when I can get them (They are getting harder to find).
They are untreated, bio degradable and don't kill beneficial organisms like earth worms.

RAISE RABBITS IN THE GREEN HOUSE!
The CO2 the rabbits put out make a HUGE difference in growth rates!
Plants MUST have CO2 to photosynthesis, and rabbits live on green house waste, make wonderful organic fertilizer, and are tasty in the fall when they aren't needed for the winter.

They eat waste plants/plant parts, produce CO2 and Fertilizer, and make your life MUCH easier!

I usually start in Feb. when most people don't start until late March or April, and the rabbits produce heat along with everything else the add to the green house.

DO NOT face the long side south if you intend to raise stuff in the summer!
It's VERY HARD to keep the temps reasonable if you have a south facing side in the summer.
My long side is facing south, and I wish I would have built with an end facing south west, it gets REALLY HOT even with all the roof and floor/door vents open!

South west facing is good for hot beds, which is what I was thinking when I did it, but if I had it to do again, I wouldn't!
If you aren't trying to raise anything real early in the season, the thermal tank won't be necessary, most green houses heat up really quickly.

I use concrete blocks and brick stacks to collect passive thermal in the day time instead of plastic or metal racking.
Metal racking always rusted VERY quickly due to humidity and fertilizers, so the bricks/blocks work for thermal mass along with not rusting/rotting.

I don't have any automatic thermostat controls, I simply prop open roof panels and open floor level panels when it's hot, and close them when it cools off.
Automatic would be nice, but if you have a green house, you know you are out there every morning and evening anyway, so it's not an issue for me since I'm not growing sensitive plants like orchids, just garden plants mostly.

Keep as much metal out of the pipes as you can, and run a rust filter on the water lines.
Everything metal will rust uncontrollably, that includes water pipes.

Pest control is a concern, so get yourself screens for the vents and doors.
I use vinyl screen doors with vent windows built in.
I've had aluminum corrode so badly the hinges seized up, and steel doors won't last 3 seasons.

If you have 'Hot Boxes' inside the green house, DO NOT forget to open them in the daytime! I've nuked more than one crop of germinating seeds by having the hot boxes closed in the daytime!
Wish I was smarter, I wouldn't have to do as much work!

If you have a compost pile inside the green house, make sure it's vented well.
Compost can produce toxic fumes, and it can start fires if it dries out,
So if you compost inside, make sure you vent and keep it moist.

I don't use straw in my greenhouse. I got aphids and other pests from straw/hay, so I don't use it anymore.

If you use mulch, make sure you SMOKE IT or MICROWAVE IT before you take it into the green house,
Bark Mulch is a real freeway for every type of pest you can think of including termites and wood bores.
I just use pea gravel now for drainage, and I don't have to worry about pests, and it's reusable where mulch usually isn't.

Remember to spray new or especially USED pots with a bleach/water solution before you use them again!
I found that one out the hard way! Damed Beatles everywhere from exotics!

I don't put new plants in the green house anymore, I leave them in a 'Hot Box' outside until I'm SURE they aren't carrying something stupid and hungry!

Import (Buy) Ladybugs, the actual RED ladybugs and turn them loose in the building. They make GREAT pest control!
No aphids when there are lady bugs around!

Salamanders ROCK! Just the plain old brown or black salamanders that roam around free are great to have!
It's a little unnerving the first time they fall off the water lines or electric wires on your head or into your drinking glass, but they are harmless, and they will go to the ends of the earth to eat pests!

That is 'Farm Boy' version 1.0, hope it helps some.


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## StillKickin (Aug 5, 2010)

Wow that is a ton of useful information, seriously did not expect such a response, I thank you.

As far as the electrical side, that had too many variables at this point as far as ive seen exhaust fans from 1amp to 20 amp and thermostats that use 15amp... I would definitly start with a deep cycle marine battery.... So im not sure yet as far as that goes. What am I missing tho, would it be smarter to have some things run directly off solar during the day, and just have the water and exhaust at night ( there will be a propane furnace top heat ) 


Also on a side note, how did u build ur own solar panals? that sounds cheaper then what im goin to do...

and any other tips like that are being sucked in like a sponge so keep em coming...


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## NaeKid (Oct 17, 2008)

May I ask, why do you want / need a 750watt inverter attached to the system?

You could easily run the whole building off of 12-volt DC directly from the battery. The lights could be LED based on reflectors to spread the light out evenly, the fans could be 12-volt (think RV-fan or computer fan) that will allow you to move the air as required. The water-pump again can be 12-volt based to move the water from the barrels to the plants - again - think of an RV water pump to a sprayer (that is what I use for my trailer's outside shower).

By not using AC power, you can extend your power-capability significantly by using the power "directly" from the solar panels instead of using the power out of the charged-up-batteries during the day and have the batteries providing power at night through the use of a light sensor to auto-switch between solar-use and battery-use.


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## JeepHammer (Oct 10, 2008)

StillKickin said:


> Wow that is a ton of useful information, seriously did not expect such a response, I thank you.
> 
> As far as the electrical side, that had too many variables at this point as far as ive seen exhaust fans from 1amp to 20 amp and thermostats that use 15amp... I would definitly start with a deep cycle marine battery.... So im not sure yet as far as that goes. What am I missing tho, would it be smarter to have some things run directly off solar during the day, and just have the water and exhaust at night ( there will be a propane furnace top heat )
> 
> ...


The solar thermal is what I built, nothing more than a shallow black box with tubes inside.
Reflector in the back to reflect up on the tubes painted black,
And I just used a 4x8 sheet of plywood with 2x4s around the sides, Plexiglas front to let the light in.

Tubes absorb the heat, transfer pump circulates the hot water into the green house and cold water out of the green house in a constant loop.

The drill motor runs off a Harbor Freight solar PV (Electric) panel someone gave me, It's too weak for a larger system, and the way it's made, it won't 'Gang' with other panels, so I use it as a stand alone with the drill motor.

The drill motor is an old cordless drill the battery quit in, so I hard wired it to the PV panel and it does something other than taking up space in a landfill.

It's not real efficient, but the water 'Warmer' (not heater, just warmer) is free to operate, and it works automatically at dawn and cuts off around dusk.
-----------------------------------

If you want to run lights in the greenhouse, then you are going to have to go with some low current type bulbs, LED lights in 12 volts.
They are pretty expensive.

Since you don't need lights in the daytime in a green house, days aren't an issue.

If you go with anything larger, your light time will be SEVERELY shortened since just a plain deep cycle battery or two won't provide power for very long.

Fans will be an even worse drain on the batteries, and fans take a BUNCH of current to operate.
I tried fans, but opening top panels was VERY efficient when I learned to let air in around the lower parts of the structure.

Fans have an added advantage of easily being thermostat operated,
But they are expensive to install and operate.

There are low consumption fans, but you will have to get creative.
The fans in computers are SMALL, but they are low consumption,
And they are made in much larger sizes than you see in you home computer.
Watch military surplus fans, they are often intended for 400 Hertz AC current instead of battery voltage in DC...

I find the big fans once in a while, but it was just easer to open roof panels and supply ground inlet of air, and let the draft cool things.

When it's 'Kind' of warm, you can leave the floor panels mostly closed, and get about any temp you want with a little experimentation.

Charging two deep cycle batteries over the course of a day is going to take a $500 solar (PV = Photo Voltaic) panel...
That's a LOT of cheese for only charging two batteries!

If you go manual, if the greenhouse pays for it's self, then you can add a few more panels, a charge controller, some extra batteries, ect. and have a REAL RENEWABLE SYSTEM installed!

Now, fans large enough to ventilate a green house of any size are HIGH ELECTRICAL DRAIN units.
DC (Direct Current) doesn't turn fans very well,
It takes a LOT of amperage, the current doesn't push through wires very well,
Long runs of wires steals a lot of the battery production, ect.

If you go with large fans, go with AC (Alternating Current) at standard house voltages, around 110 Volts, and that way you can run off an INVERTER,
(Inverter 'Converts' 12 volts DC from batteries into 110 volt AC for common house hold appliances and common fan motors.

With the fans sucking up pretty large amounts of current,
You don't have to have huge copper cables running to the fans like you would if you went DC,
And you can use common 110 volt switches, wiring, ect. 
Instead of heavy duty starter type solenoids for that same amount of power in DC.

For the amount of power two large fans would draw, the losses in the inverter converting from 12 V.DC to 110V.AC are minimal,
And 110 V.AC is much easier to work with in the long run,
No custom motor fans, no custom switching, no VERY LARGE cables to supply low voltage at large amperage, ect.

And if your batteries go down, you can always plug into the utility grid to power your fans.

Personally, opening the roof panels is easier and a BUNCH cheaper!

--------------------------------

If you go totally solar, you will have mid Feb. to late Nov. for a growing season, after about Oct. 28 don't expect enough daytime sun to grow much of anything without artificial light, which is EXPENSIVE,
So when the garden is done, My green house is usually done...

Length of days picks back up in mid Feb. and you can get enough light to do the job, but depending on your location, you might not get enough heat (Thermal) to warm up a green house enough in the daytime to keep frost out at night...

That's why I use the tank type thermal mass heat exchanger, to heat the greenhouse in the dark hours until the sun comes up again.
The concrete blocks and bricks help too, and you can find those cheap.

The heat exchanger is 'Thermal Mass', the larger the tank (Which I have shelving grates over for a work bench) and the larger the solar collector (thermal) the warmer the tank gets in the day time, and the longer it stays warm at night.
Having a water source handy doesn't hurt a green house either!
Soaking roots, dipping to water plants, ect.
If you collect rain water, no treating it before you can use it directly either, and it's free.

I do get a lot of dirt in the tank, so clean out is always fun  but it has to be done once in a while...

I used a metal tank for the first 3 years or so, but it rusted out.
I use a big plastic farm animal water tank now, but that would be up to you.
The guys down the road that grow flowers have a HUGE tank that is concrete and it works GREAT!

The larger the tank, and the more solar collection you have the longer it will shed heat in the green house,
And the cool tank in the daytime actually keeps the greenhouse from heating up as fast.
Since most of us have tables in the center anyway, the tank makes a good way to raise up your work, and do the heating/cooling job at the same time.

If you have smaller tanks, there is no reason you can't have more than one if your greenhouse expands with profitability.

One thing I always grow around here that are cash cows are ferns, daylilies and Mimosa tree seedlings.
Easy to grow, sells themselves, and there is a never ending market for them.
Every open spot in the spring is covered with them since I'm planting anyway, and they grow with little or no work.

What is really selling for us is 'Lavender', we've actually planted a field in it and it sells like crazy in the local collage town!
Pays more than garden produce or even flowers, and it takes virtually no care.

If you grow trees or bushy plants, expect the cops to show up...
We tried some indoor type shrubs, and someone some were will report you for growing 'Pot' every single year!
They even showed up one year because they saw the greenhouse with stuff growing tall from the air!

Besides, green houses are TERRIBLE places to grow pot,
They take too much care and are too picky about CO2 content, fertilizer, irrigation, ect.
I tried growing a decorative that has about the same requirements as pot, and they were CONSTANT care plants. One season and I was done with them.

Just remember, fertilizer is corrosive, so anytime you can do anything in plastic, glass or concrete, do it instead of metals.
I use Pavers & Stepping stones on the floor walkways so everything drains without me having to use a squeegee and mop to clean up spills,

But watch what grows in the cracks! You just never know what's going to pop up on it's own!
I have a nice Fig tree volunteering, so if it makes it, I'm going to have a nice Ficus tree!
Don't know where it came from, I haven't EVER had a ficus in the green house, but there it is, big and bold!

I know 'Gardening' isn't the normal 'Manly Man' and 'Survivalist' type thing to do, but I enjoy it and it's productive.
So glean what you can from this, and dismiss some or all of it, it's up to you.


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## StillKickin (Aug 5, 2010)

NaeKid said:


> May I ask, why do you want / need a 750watt inverter attached to the system?
> 
> Most of the system will be running at night time, no need for lights and such and having a longer greenhouse would require easily 4-6 of those small fans, by converting it I can guarentee that the power i use through the night will not drain the battery more then the solar panels could recharge it. A battery like that dropping too low, i beleive less then 30% will not recharge correctly, and this "facility" needs to be able to run by itself for up to 5 days


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## StillKickin (Aug 5, 2010)

Exactly,Like i said i think a 750 watt inverter on one battery running off a 12v solar panel would be best bet, i did however one time see this device that has a photo eye that is under the panel that turns the panel with the sun... maxing out charging the battery. I intend to grow trees that in 2 yrs reach about 12-14 ft tall in the greenhouse, they are arid/tropical trees thats why they are growing indoors and have a natural insect repellant.

I had leaned this one tip, since i live in NJ and our winters are completely random and out of control like this past one i was told to have 55 gallon drums around the sides of the greenhouse(inside) to not only stop the cold from geting in but to use the water for the humidity and to also hold the heat at night... ever tried any of this?


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## gypsysue (Mar 27, 2010)

JeepHammer, that's the best greenhouse information I have EVER read. If you haven't written a book about it, you should.


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## JeepHammer (Oct 10, 2008)

gypsysue said:


> JeepHammer, that's the best greenhouse information I have EVER read. If you haven't written a book about it, you should.


Just killing time while I'm canning the garden produce.
Some of us old 'Dumb' farm boys just might not be so 'Dumb' after all...

The 'Problem' with the solar battery idea is...
1. You might not get the sun to recharge batteries, so your greenhouse would overheat with fans.

2. One thermostat (home wall type, with mercury bubble switch) and a start/stop limit switches on a screw jack (like used for those big old satellite, or tread mill inclines) will open your roof vents automatically, without draining the battery (or Batteries) excessively.
TWO thermostats will open/close the roof vents automatically for up to 5 days without you being there.

Tread mills are on EVERY yard sale, and the electric screw jacks wire VERY simply. I use one to make my solar panels track the sun across the sky, they are VERY reliable.

3. VENTS take NO POWER to operate. it's simply convection ventilation.
Since I'm in my green house every day in the spring, it's no issue for me to open the vents when it gets 'Warm',
But automated systems will relieve you from having to visit the green house if you don't want to.

4. Fans can be wired in as a 'Back Up' to the screw jacks/vents very easily.

5. Depending on how much wiring you want to do, you can wire in a 'Burglar' alarm system to dial you up if the vents/fans fail.
Radio shack has basic 'Do It Yourself' alarm kits cheap.
Just hook up a temp sensor to the 'Burglar' alarm and program it to call you with a pre-recorded message instead of dialing 911.

Anyone enters my shop, power/well house or my home, my cell phone gets a call... (I don't dial 911 except for fires, which is also programmable and will call the fire department directly with pre-recorded message.)

6. Most of the spring and much of late fall the temps in the green house won't get excessive even if the vents don't open.
Summer is when you REALLY have to worry about it, and the vents stand open most all late spring, all summer, and most of early/mid fall anyway.

The early spring or late winter, you simply DO NOT open the vents at all,
Late spring all through the summer, and early fall the vents stand open since there is no danger of frost/freeze,
And again in late fall you will need to keep the heat in, so vents come into play only about 20% of the time you are normally operating a green house.

7. Winter there is no point in trying to heat a green house unless you are growing exotics that don't 'Hibernate' for the winter.
Not growing tropical orchids? Then put the green house to bed for the winter in late fall and be done with it until early spring.

8. I often Pot/Plant seeds in late fall, Put them in the compost pile or dug out below ground level and keep them cold without freezing them,
And in the spring they 'Volunteer' to sprout as soon as there is long enough days for them to do their thing.

The plants know EXACTLY when to sprout, so there isn't any reason to worry about them over the winter.
Most seeds can freeze without problems, so the Compost/subsurface storage isn't necessary in most cases.

Nothing like seeing the lettuce and other seeds start growing in the 'Hot Box' telling you EXACTLY when it's time to start the other plants!
It's always nice to see the first 'Green' of the season about that time too!

9. The trick is to grow things for your climate zones,
If you are in zone 3, don't try to grow things from zone 5!
Doesn't matter how much you try, you simply won't get the length of sun to make them grow correctly,
And since they aren't going to survive the next winter no matter where you plant them (or your customers plant them) it doesn't matter anyway.

Indoor plants should be transfered INDOORS in the winter, not in a marginal 'Green House'.
Heating a green house is HATEFULLY EXPENSIVE up here in Indiana, so I don't even try...

I keep it "WARM" enough to keep the frost off, and let nature do the rest.

10.What plants are you planning to grow that won't need water for a week at a time in drainage greenhouse pots?
Trees take a TON of water, especially when seedlings and when in green house pots!
It's a constant fight to keep the moisture correct with things like Japanese Maples and other ornamentals when they are seedlings, and it's even worse when they are in drainage pots!

Trust me, I've MURDERED A MILLION of them down through the years! 
Under water, over water (Which is difficult with a greenhouse drainage pot!)
And with most trees/shrubs, if you "Wet Plate" Them, you will tear the hell out of the root ball trying to get them out of the wet plate when you transfer them...

I even tried irrigation hydroponics at one point, and the roots ran wild, and were a MESS to try and transplant alive!

Anyway, just some ideas from the 'Farm Boy' that might help... Or not...


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## JeepHammer (Oct 10, 2008)

Almost forgot!

If you want to 'Start Early' in the spring without risk of freezing,
Build your starter 'Hot boxes' over a compost pile.
No 'Heat Tape' or 'Heat Light' required to keep them warm, every compost pile generates a LOT of heat, and if you have your compost bins boxed on three sides anyway, you just flip and water the compost when you put the hot boxes on top, use an insulation board to close up the open side of the bin, and you are off to the races without powered heating.

It's amazing what a turn and a little water will do for a compost pile in late winter/early spring!
They REALLY generate heat in a hurry.

The rising heat from the compost pile will keep an insulated hot box from freezing from below, and you can start MUCH earlier without paying for 'heat' to keep the box from freezing.
We often have lettuce and radishes in March!

No point in planting earlier than about Feb. 28th or so, you simply aren't getting enough sun even if you are facing south with the hot box,
But if you start somewhere around the 15th to the 28th, you can have fresh lettuce and radishes by the end of march!

I'm STILL trying to find a reliable way to vent excess heat out of a hot box automatically, without external power.
Right now, I'm using the thermal windows out of an old screen door and I simply open the window when I want to cool things down.
The screen keeps the bugs out, but you have to watch the thermometer on warm days or the box will get WAY too hot...

Storm windows from old houses, the kind with aluminum frames, work pretty well, but I prefer the vinyl type, they don't rust, corrode, and they usually have thermal panes in them...


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