alpha010

Slow day at work today so I figured I could brain storm. I was looking at the Harbor Freight gh's and thought.....take (2) 10'x12' gh's for $799 each (or for that price the layout and buy my own building materials) and erect them side-by-side to make a larger 12'x20' gh. Now instead of finishing both roofs like you normally would, only finish the outside ones and add a taller peak in the middle (while still maintaining the framing for the inner roofs to help with support) so that small trees and (some) non dwarf varieties of nanners can be grown inground year-round in my area.

Thats the simple part....

What I want to do with this is make the short sidewalls removeable in sections for easy carrying and storing and make the upper half of the entire roof ventable in sections as well.

Now the fun parts.....The above would be simple engineering so no worries on those....

Next thing to tackle would be heating. I want to try to emulate my summer days (80* daytime and 55-60* nighttime) all year round. I do know, to accomplish this would make for an extreme gas or electric cost monthly and would drive me broke after first winter, so, I believe I have a remedy but need input from others who may be more knowledge-able in alternative electric sources. I was looking at btu's and heaters and kW consumption to produce the desired temps. I would like to use wind/solar hybrid and off-grid power source. While doing calculations I saw some wind/solar turbine + inverter/generator packages starting at around $800 and going as high as $8,000. But the turbine/inverter wattage and voltage numbers have me stumped...

Okay, here's what I figured out for the greenhouse:
Sq. ft. of surfaces to be heated totaled = 1,114 sq. surface ft.
BTU's needed to heat using 6mm polycarb twinwall = 58,000
Electricity per month (in kw) needed to heat = 4,300
Plus lighting and other ammenities not yet mentioned (kW) = we'll say 500 for round #'s

Now that that is established, would a 600w 12/24vdc turbine with a 1200w 12/24v inverter be hardy enough to keep this running off-grid with multiple gel-cell battery backup? Or, would I need to go as large as a 3500w 12/24/48 vdc turbine with a 6000w 12/24/48v inverter?

I also wanted to run in-ground heat cables at 65* over entire area.

Lights:
During the summer, none. From oct. thru april, I want good supplementary lighting to automatically come on at 6:30 am and turn off at 9:00 am, and also come on at 4:30 pm and go back off at 8:30 pm. Now the question for lighting. Is there a way to setup photo-voltaic eyes so that they do this for me instead of relying on a timer and also if it is a cloudy day, have the light stay on all day?

Watering:
Auto misting and drip-irrigation. Nothing too complicated.....except for the waterline from the house to the gh might freeze unless I use rain collectors or wrap it in heat cable.

I do know this souds like a huge undertaking but, I still would be interested in hearing costs vs. gain and how to properly gauge alternative electricity sources which most could benefit from considering some states offer tax kick-backs for going green and reducing or completely eliminating one more bill for your home. I chose to attempt wind for the simple fact that there is almost never a windy day at my house, It is like I live on the coast, and in the long run could pay itself off in a matter of 2 years or less even if you decide to go on-grid. Some electric companies even give you discounts if on-grid.

Shaggy

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lorax

Shaggy, how much does Propane cost in your neck of the woods? Because if it's cheap enough, you can use patio heaters.

Scuba_Dave

My original greenhouse design was much taller



Before I stumbled onto bananas I redid it & lowered it
The door on the left is 5' tall
I dug out about 1' in the ground
The roof slides open



The jaloiusie windows were all free, as were the sliding glass door panels - roof. I still have 7 more sliding glass door panels. And I have had offers for more for free

I'm planning on putting framework on my garden & make another greenhouse/cold frame. The sliding glass doors will be sideways -so the greenhouse will only be about 36" tall at the sides
As I pick up more sliding glass doors I'll build more cold frames

The sliders are tempered & insulated glass

Just an idea

alpha010

Not sure of unit cost, but to get a standard grill-sized tank refilled costs $15....not cheap if you ask me. Everyone I know that lives out in the countryside that use or did use propane are converting to electric because of cost. But, I can look into it and see the cost for a larger 100gallon or so tank and unit cost and do some calculations.

Dave, I did see those pics on your other project thread, looks wonderful, but alas, I have not ran into anyone or read in any of the classifieds about free doors and windows or else I would snatch them up. People in my town would rather throw something away than see if anyone else could use it.
I do plan on making a lean-to like yours on the side of the house but I have to wait to see if we decide to go through with our addition plans before I can build one. Plus, that would be something to do in addition to the main greenhouse and actually use it as passive solar heat in the winter.

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damaclese

i would think that for that much money you could put together a better more custom GH if your handy i one can set 4 4x4 post to what ever size you require then connect them on top with more 4x4 gives you a cube then you can hang recycled storm windows or doors what ever you can find from the out side of the post make a truss system on top with a main beam of 6x6 and use the same recycled storm windows thees should all be attached in a fashion that aloue them to be removed or even propped open in hot weather you will have to weather strip on the back side of the post you can set 2x4 as sash bracings behind so theirs something to seal against don't forget to brace at the bottoms between the 4x4s if you place water containers that are painted black inside they absorb tuns of heat and will radiate it back out during night time this will decrease your heating bills it dos take up some space but it works grate all pretty low cost and defiantly can be made to look vary nice if you have the know how to make it that way this is what i am doing for my GH except I'm good with cabinet building so I'm making my own removable sashes i want a certain profile i think bepa used recovered shower doors for his sun room project those are some mighty big peaces of glass that are tempered and would cost hundreds to order custom any way its just a thought all the other accoutrement would cost a bit do to their specialized nature but maybe some one els can give you some on the cheap solutions for those

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damaclese

o i forgot to add that corrugated fiber glass panels work grate for green house roofing they let light in at a some what reduced rate the will yellow in a few years but they have a product that can keep that from happening now i understand and lastly iv push comes to shuve if you can get the basic wood structure in place you can go to Home Depote and get heavy plastic and cover the hold thing in that many commercial growers use plastic if it a good quality it can last for 3 or more years if its properly attached with Mullins theirs many ways this can be done for next to nothing be sure and check to see if a permit is required for your area!

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lorax

OK, didn't know. A 50lb tank of propane here is $2.50 - I'm so out of touch with the prices up in winteryland! In that case, I'd investigate a wind turbine and a small storage battery and generate the electricity right there. Check what your city wants vis a vis permits, though; some places discourage home electrical generation. I personally got into a heap of trouble for a little windmill up in Canada.

If you're set on extending the roof of those greenhouse kits, Pauly has a great point about the corrugated plastic stuff; there are special bolts with rubber washers and hex heads that are used to attach it, and if you get the Israeli-made ones (4x8 panels) they last for decades.

alpha010

I'm lucky for the permit thing, Ohio is usually very lax on the permits, even though most things require one, it is relatively easy to get one. And, the electricity being home-spun, Like I said, Ohio is usually very lax on most things of that nature but will check into it.

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damaclese

are those the ones that have the heavy UV coating? i hear the are outstanding and much better at resisting wind damaged

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lorax

Those would be they. I did my orchidarium roof with the opaque ones, and I'm very happy I did. The regular corrugated ones get ripped to heck in the wind here.

adrift

A 600 w turbine would not be even close.

Watts are power; a rate.
BTU/hr is also a rate.

Watt-hours is a measure of energy.

If I trust your BTUs needed, 58,000 BTU/hr is about 17,000 watts

If you assume that you would need 6 hours of supplemental heat per night you would need 17,000 x 6 = 102,000 Wh or 102 kWh.

A size 8D deep cycle battery (about 175 Lbs each) has a 20 hour discharge rate of about 230 Ah. 230Ah x 12v = 2760 Wh. So you would need about 37 of these batteries to store a night's power. But, since you will actually draw the power out in 6 hours not 20, you will need quite a few more. And batteries last far longer if you use only 60% of their capacity. (cycling between 20% and 80% charge). So good practice would double these numbers.

Your turbine would have to run at full rated power for about 30 hours to produce enough energy to run a 17,000 w heater for ONE hour. Or 180 hours to produce 1 night's electricity. If you can assume (hah!) that your wind is consistent enough to produce power 24 hours a day, 8 of those turbines should be enough. If you get wind half the day, 16 turbines should work.

Lessee. You'll need 8 to 16 turbines, and a very minimum 45 batteries. If you can find 12v heating elements you won't need the inverters. But, if you do use inverters be sure that they are in the greenhouse so that their waste heat contributes to the greenhouse. Or you'll need more turbines and batteries.

Sorry for the bad news. I'm all for green power, but there is a reason we buy petroleum and mine coal. If we could all stick a little windmill in the back yard and get by it would be grand. If it were that easy, we would have done it.

If you wanted to do this on the grid, assuming an electric cost of 10 cents / kWh, your daily cost would be $10.20. (~$300/month) If the heat had to run 24 hours a day, your daily cost would be $40.80 (~$1200/month)

Seriously, check out bulk propane.

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chong

Heating is needed 24 hours/day. You can have an average daytime heating requirement and an average nighttime heating requirement, or you can calculate a combination for an average daily heating requirement. I did some calculations based on Alf's specs, and I came up with some numbers that are not as bleak as KJ's. It's still bleak, though. This is just addressing the heating requirement and not what size of wind generator will be required.

Just double checking your numbers, Alf.

R-value of surface air outside= 0.17
R-value for 6mm twin-wall Polycarbonate= 1.79
R-value of surface air inside= 0.68
Overall R-value = 2.64

U-value= 1/R-overall = 1/ 2.64 = 0.3788 BTU/Hr./SF/°F

Assume: Overall surface area = 1114 SF
Outside Temperature = 0°F (USDA Zone 6 - mid)
Inside Temperature = 85°F

Heat loss through Polycarbonate walls
= Area x U x (Temp. Inside – Temp. Outside)
= 1114 SF x 0.3788 x (85°F – 0°F)
= 35868 BTU/Hr. ~ Say, 36,000 BTU/Hr.

36,000 BTU/Hr. = 10.55 KW (This is if the temperature throughout the WHOLE month were to be 0°F)

However, assume that the average temperature throughout the month = 12°F
Therefore, average Heat Loss/Hr.:
= [(85°F – 12°F)/ 85°F] x 36,000 BTU/Hr.
= 30,918 BTU/Hr. ~ Say, 31,000 BTU/Hr. or 9.1 KW

Hours in a month at 30 days / month = 24 x 30 = 720 hours

Based on this the average monthly consumption would be:
= 9.1 KW x 720 Hr.
= 6550 KW-Hr. /month

At a rate of $0.10/KW-Hr., you will be spending $655 per month on the average at an average outside temperature of 12°F and inside temperature of 85°F.

I would agree with KJ on using gas for heating, depending on the cost of the service gas. Because, over here in the Seattle area, Propane cost more than Natural Gas, and with the cost of Propane heating equipment, Propane may even be more expensive here than electric heating.

alpha010

Good educating KJ and Chong. Thats exactly the kind of info I was looking for! I am unfamiliar with measuring power consumption vs. power output rating, all chinese to me.

Chong, I got the generic R-value for the 6mm twin-wall poly from ACF Greenhouse online calculator. That's what I used for my BTU's and gh surface area.

KJ, what is sad is that the technology for a home windfarm or at least a single turbine that could power your whole house IS there. The fact that the power companies are consumed with greed and those that could put up a good enough fight against them ither won't or get squashed trying to do so. It's just like the car manufacturers saying that the technology for a fully electric car is not mature enough yet to even try to create, is simple a farce. Back in the very early 1900's there were more electric cars on the road than gas powered by a scale of 2-1, that is until the early twenties hit and gas and oil companies came into big play.


In my area, heat oil, propane, gas, and electricity are all about the same cost. I have not checked bulk propane costs yet though, but would assume atm, that pro and heat oil are about the same cost on bulk level.

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damaclese

chong vary competent calc there i commend you could i throw in this what about a multi energy mix if one adds the barrels of water and also adds a supplemental pool type of soler heater the kind you put on the roof just as a guess I'm saying there would be a substantial reduction of heating cost and if you wanted to go one step further by adding a underground heat sink which could be placed directly under the Green house even better all leave that up to you all to work out the details if that would even help but i know from reading that theirs many ways to heat a GH without resorting to electric here in Vegas that would be prohibitively exspesiv painting floors black using sodium filled tanks or bladders also vary affective at reducing night time heating cost using a radiator hooked up to the water tank in your house can also help i think this all depends on how warm you want it Bananas as we all know will do just fine at much lower temps then 85 if say it could be kept at 65 they would still make it threw the winter in good shape and at 65 most orchids will survive just fine

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chong

Absolutely, Pauly, a solar heating system is the best and cheapest system, particularly in areas with a high solar index like NV and AZ. Even in the wintertime, the solar energy available remains high. Unfortunately in Seattle, it couldn't be worse. We have the lowest solar index in the country. The winters are pretty dark. I have said this before - that when it rains here, it gets pretty gloomy. What makes it worse is that when it rains, it rains slowly, but prolonged.

I would think that in OH, the solar index should be reasonably high, even in the Winter. Solar heating should prove to be economical in that state.

The water storage tanks should be placed at the south side of the greenhouse where they themselves collect the heat.

It really isn't practical to keep the greenhouse at 85°F in the Winter. In the Philippines, the temperature can go down to 75°F to 80°F in the Winter months, sometimes, as much as 10°F lower than that, even. (I can tell you, though. When the temperature is in the low 70s, people wear sweaters/jackets there.) So, if you want to just overwinter your bananas, keeping the temperature to 60°F to 65°F will allow them to continue growing, although a bit slower. But then if your plant is about to bloom, or in bloom, it will allow the fruit to continue to develop.

alpha010

Chong, you would be surprised about our solar index! From Sandusky (40+ miles west of Cleveland) all the way to Pittsburgh gets alot of lake effect weather, so in 2007, it was recorded that we only had 80 days total for the year of sunshine. 2008 was a little better with roughly 110-120 days, most of those are during the summer. Our winters are usually drab and ho-hum usually overcast.

I understand about keeping the winter temp down to 65 but I'm thinking of extremes since the way I do things is "Go big or go home". Although the wife tends to dropkick me back into reality often enough not to go too big.

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damaclese

id just like to point out that even on a cloudy day if theirs a cover of snow on the ground theres tuns of reflected light more then enough to capture with soler particularly with the water barrels i know living in NV makes me some what optimistic about soler but come on guys it free heat for the taking you may not think its warming the place up but trust me its doing more then you think even on a cloudy over cast day often cloud cover will hold temp's much high then would be the case on a clear day theirs a nice article on the desert growers web site about how frost really works most people are woefully ignorant about heat and how its transfer and were it accumulates air circulation helps transfer heat and throw friction adds some on its own if your are accumulating it I'm sure Seattle is a bust but I'm fairly familiar with the types of weather in the Mid west as I'm from there theirs vary little of any lake affect snows after jan1 thats mostly before the water temps drop and you still have high levels of evaporation most of the mid west gets thees grate clear cold days in Jan the Sun agents the snow is intense one has to ware sun glasses see my point? but if you don't want to do it then i understand its some how easer just to stick a gas heater in and forget it but based on what i know about whats coming down the pike for energy policy in this country id convert now whial you have the time rather then later when you have to all at ones i heard on the news yesterday that we have less then 10 years to get off the oil and i fore one don't want to have to be looking for a bargain when 450,000,000 Americans suddenly have to go soler can you imagine the price of collectors on that day WOOO boggles the mined

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