Ventilation...air extractors...solar powered.

[Kiwi Phil]

As you know, I am a grower.
The trial tunnel house (covered in clear plastic) I put up early this yr has grown good out-of-season stock. I have made it insect proof so i can use it in the summer too.
It is only 48m sq. and 180m cu.
It has 2 insect-screened vents up high, plus same for the double door.
Problem i am having it, it is getting just too hot.
1st week of spring, it has gone over 45 degrees C , and it is rising everyday.
We can't pick in it after about 7.30am.

The easy option is to put a single phase extractor fan on it, but I want to think this one through properly.

I need ventilation when the sun is out, so why not go solar??

I get a lot of sunshine, 10hr per day everyday in summer. Only change in winter is reduction in hrs down to maybe 8hrs.

So my thinking is....why not use solar power.
Done a lot of re-search......mass produced solar extractor fans are too small, expensive, pretty much 'toys'.

If i build one, my limited knowledge says use a 12v motor, connected to a 12v battery (deep cycle....700cca??) with a trickle charge solar pannel.

A large fan itself must be easy to buy.
Casing can't be hard to buy or construct.

But what do i use for a motor...does anyone know what-size motor turns what-sized fan, and what-size power source is needed and what-size solar panel?

Now to go a step further, I am constructing another one of these tunnel houses, 30m x 10m x 4.5m to top of roof which will grow 50,000 plants at a time, so i have to come up with some solutions to ventilation soon.

Are there any experts in the house?
I do have to do something.

Cheers
Phillip

 

[Bass Tracker TX17]

Re: Ventilation...air extractors...solar powered.

I am no expert by any stretch but i do know one thing. You need to evaluate the amp draw of the motor/fan assembly you intend to use. In order to do what you suggest your charging amps must meet or exceed the use of your fan. If you were to use the fan at night then charging a pack of batteries would not be a problem. However, you are trying to charge and run at the same time.
As far as the fan size I'm sure there is a formula for air flow for a given size area. Vent low at ground level and open to the roof.
I don't know how cost effective it would be.
Interesting idea...

how about a wind powered roof turbine ??

 

[Bigprairie1]

Re: Ventilation...air extractors...solar powered.

I'm not a grower Phil, but for what its worth this is what I've seen here locally. Around here and on some greenhouse systems the temperature is controlled (somewhat) by having the top peak group of windows/frames open on simple pneumatic struts when the temperature exceeds a certain point. I believe this system does not require ac power just heat set points. I might be able to find out a bit more about this system from my wife who runs a Garden Centre and could enlighten me a bit on this.
Regardless, it does let that 'big' heat out as it starts to climb. I know the hothouse tomato people rely on it quite a bit.
BP
Not on the lighter side: given the fact I'm here in B.C/Canada it would be interesting to see how some of the 'BC Bud growers' are doing this under the radar of the RCMP and BC Hydro...who keep a VERY close watch on hydro consumption per customer...and not for billing reasons...LOL.

 

[CN Spots]

Re: Ventilation...air extractors...solar powered.

My parents use a pneumatic strut vent system on their greenhouse. Works similar to a thermostat on a car. Oil heats up and pushes the cylinder out opening the window. Great invention.

 

[Kiwi Phil]

Re: Ventilation...air extractors...solar powered.

Thanks chaps.
That has got me thinking sideways.

BP1.
If your wife can find out who manufactured them and any info on their operation, efficiency etc, then that would be great.

Gidday Spots.
Same same for you....If I can get a name of manufacture or supplier that would be great.

Looked up google but can't locate anything appropriate.

Your suggestions have got me to thinking.

If I removed the end vents (hinged at the top),on the inside of the shed, (that lift up to open), and put them on the outside, hinged at the bottom, and opening down and 'outward', i wonder if i would get a very efficient chimney effect.
No obstructions for the air flow.!!

The new big tunnel going up has roll-up side walls with insect screen behind. That will control the air temp below 2m (6' 8") to a degree, but between there and the top of the roof at 5m (16-17') needs venting.

The ideal solution would be to build a tunnel-house with 2 full-length vents running full length of the roof ridge.
The cost is far too high for me.
When the plastic needs replacing, it is a big cost too.
The returns just aren't there in the short term.

Thanks.
Cheers
Phillip

 

[CN Spots]

Re: Ventilation...air extractors...solar powered.

Phil, can you get to this site from Oz?

http://www.virtualseeds.com/greenhouses1.html

It's home-use stuff, not commercial but it kinda shows what we're talking about.

spots

 

[Bigprairie1]

Re: Ventilation...air extractors...solar powered.

Phil
My wife said she'll look into it to see if she get some more specific information. I'll give you an update when she does.
This particular component is also known as a 'gas shock' not substantially different than what you find holding up the hatchback of a car.
Another very good place to search for this type of component would be in the 'Thomas (net) Directory' which is an excellent industrial/company index. Under that directory there are probably between 100-200 companies listed that manufacture gas shocks, etc. I would look into searching there including key search words 'agriculture' or perhaps something along those lines.
Anyways, thats the feedback for the moment.
BP

 

[Kiwi Phil]

Re: Ventilation...air extractors...solar powered.

Thank you all.
I never imagined the "window vent opener", you put up in that site Spots, to look like a human elbow joint.

That changes things again.

Spoke with a friend who is an electrical engineer.
1. He thinks solar is out.

2.Doing some homework for me...wonders if a 3 phase motor built for 240v and run on a single phase with small variable speed drive and temp sensors might be efficient eg higher the temp, faster motor runs.

3.Also wonders if roof vents (like a chimney) with the "window vent opener" to work it may not be sufficient.

The guy that is making the plastic cover is coming tomorrow, so I am going to ask about having top vents (plastic welded in) and using the "window vent opener" installed to open it on the inside (down ward) might work.

BP1.
If your wife does get any info, then I would be really keen to hear it...every little bit helps.

Thanks again
Cheer
Phillip

 

[Kiwi Phil]

Re: Ventilation...air extractors...solar powered.

This is the basic frame.
Needs a lot of work on it yet.
Cheers
Phillip

 

[beerfilter]

Re: Ventilation...air extractors...solar powered.

Years ago , I worked for a couple of farmers as the full time hand .
They built a greenhouse to raise their tobacco seedlings for transplant , then decided to expand into commercial production for resale .

They now have 4 houses , twice the size of yours , although yours is not exactly a small grow house , by any means .

Yes , there are readily available 110v ventilation fans out there .
Try these folks : http://www.carolinagreenhouses.com/page/page/1560559.htm

The 16" units should do nicely in your application , 1 at each end .

Also , you may wish to consider adjustable side curtains , for cross ventilation .
They are fairly simple to construct , and , can save you a good bit on electricity versus just the fans alone .

Solar is very expensive , as an initial investment .
You would need quite a few panels and a large storage bank , and , a BIG inverter to run those type of fans .

HTH

 

[Kiwi Phil]

Re: Ventilation...air extractors...solar powered.

Thanks beerfilter.
Just spoke with the manufacturer of the cover.
I am definitely going with side curtains, handle roll-up, full mesh screen fixed behind the plastic.
Putting in 2 large Vents above the doors, once again fixed mesh behind, plus a 2m x2m sliding door each end (meshed again).
I planned to do something along these lines, but I buggxr'd around thinking about that, and after your post, picked up the phone and did it.

Your right re the solar.....problem with the 'made-up' ones, they only guarantee them for xx hours, and I will chew them up quickly.

I am also trying to get some American companies to talk to me about those 'elbow type' hydrolic vent openers, but they don't seem to take my enquiries seriously....I am seeking their detailed spec sheet, and if they meet my needs, I will buy....and pay the freight. They are a great idea.

My thinking at the moment is, do the above, and see what happens, and if I need more ventilation, I will put in electric extractors.

Thanks for the reply and advice. Really good.

Cheers
Phillip