Task - 12V solar setup to vent out / keep warm

smuggler.ie

Looking for possibly semi-simple semi-DYI setup that could work two/three way, even if need to be switched over manually :

1.vent polytunnel during hot-sunny days (main task)

2.other use for surplus power(perhaps LED's lights in the shed), if any... (secondary)

3.produce some warmth during frost nights/morning(heat exchange?) (main task in reverse)

Thinking of car 12V battery(s) as storage, car cooling fan 12V 80-100W, not sure re heater solution

As for solar novice - any advice welcome.

Big Lar

I have lights in a container

75w 12v panel

12v charge controller & car battery

12v LED light strip - cut to whatever length you want

Fan I don't have, you could use an old radiator fan for a car but be mindful of the wattage and some sort of thermostat - Or would you be better off with a linear motor to open and close a window/door for natural ventilation.

Forget about your heater as you have no insulation in the tunnel

smuggler.ie

https://www.boards.ie/discussion/comment/121816767#Comment_121816767

Thanks for input.

What kit you would suggest, if any? Or where would be good place to shop for components to build my own?

75w - would it better to have 100w(more) panels to ensure charge even on cloudy day or is it enough of 75.

Door/window - we currently(on sunny days) have to open both side doors of the tunnel (~800x1900, netted) and even then she say its to hot, natural vent sometimes seam just not enough if there is no wind, hence fan option. Linear motor price also might be factor, car fan can be ripped out of some old car, but thanks for suggestion, i will consider.

Come across this project - pretty much what i think i need

Yeah, need to source some sort thermostat

Heater is not to keep +25C, just to prevent frostbite (+1-3C)

Big Lar

Your gonna have to work from the fan side with the wattage of panels that you need and go backwards from there to size your panels, that why I suggested the linear motor.

This Fan here on Aliexpress is 120w, and I had calculated a few years ago that my 12v panel was a bit less than 50% efficient so your talking perhaps 250-300w of solar just to run the fan when the sun is shining, The charge controller will take a bit and then to charge a battery as well you may probably double that.

smuggler.ie

If you watched vid i linked, that guy spin the fan(12V80W) @3V and 0.7A stating it was cloudy day , he emphasize the current that matter. That was direct connection panel to fan.

Obviously amount of air moved and other factors would matter.

I dont think i would need full radiator cooling performance of the fan, no intention to create wing testing facility in the polytunnel 😊.

Any thoughts

Big Lar

https://www.boards.ie/discussion/comment/121817107#Comment_121817107

Forget the battery and the charge controller, when the sun comes out and heats up the tunnel the fan will run at the same time.

Padre_Pio

https://www.boards.ie/discussion/comment/121817349#Comment_121817349

Maybe try without the controller and see how things go.

You might need the controller to boost the voltage to 12V if the panel cant do it.

Forget about heating, even a few degrees will take a whole lot of power since the heat escapes the tunnel almost immediately. Frost fleece is the best solution there.

smuggler.ie

Thanks folks.

This project come to mind due to two/three week holiday periods where i cant take care of the garden for ventilation or frost protection - need some automation so i thought: "lets try solar".

OK, lets put heater part aside for now.

For extraction i could just run fan of the solar, fine, however still need to regulate the speed and temp - with occasional "great" sunshine it might go to fast and i would like to be able o control at what temp it start/stop.

Any suggestions for V regulator and thermostat? Sure can search online, but what specs should it be rated for...

On other hand, if all goes well, for the future "expansion", should i consider implement battery and controller - is it worth to buy a kit or picking parts as i go.

What to look out if going for kit - controller capabilities(A, W, other)

DC999

https://www.boards.ie/discussion/comment/121817917#Comment_121817917

Interesting idea. I’d suggest go cheap as chips with 1 South facing solar panel (south produces the most and when it’s the hottest when you need the ventilation) and 1 fan. Ignore all else for now and you can always add to it in time.

Is there a way to test this before you start to invest in it? As in do you have an existing large fan you could try with it to see if the moves the air in the tunnel? Run a long extension lead down and test it with a normal fan plugged in. I’ve been in one tunnel only and during hot days it was unbearably hot. But I won’t pretend to know how much air a single fan would move through a long one. You could start with that and then if you wanted, add more sophistication in time. Fans don’t use much power. But check the label on your test one to get a sense of the wattage you’ll need to move the air.

 This punter just connected the solar panel direct to the fan, with a switch in between. Cheap as chips. Can’t regulate fan speed or start / stop based on temp as you mentioned. solar powered greenhouse fan (youtube.com). Load of other examples of these on the internet. Sun is out, fan comes on – that’s it. Then switch to turn it off in winter so cold air won’t come in on a sunny cold day (solar runs based on light levels, nothing to do with temp – I didn’t know that at the start). For that you just need 1 solar panel, some fan, some switch to power off the fan, some cable.

 In terms of temperature regulation, I use these at home (but needs a 3 pin plug). If temp probe is above X, then auto turns socket off (and whatever is plugged into it like the fan). KETOTEK Digital Thermostat Plug Socket Temperature Controller 220V with Sensor Probe, Thermostatic Plug Heating Cooling for Greenhouse Freezer Refrigerator Fermentation : Amazon.co.uk: Business, Industry & Science. This model only allows 1 temp setting so if above or below X, turn plug on or off. Good news is it holds it’s setting when it’s powered off (which your plug will be each day when the solar goes offline). I’ve another model of theirs that allows 2 temp settings based on time of day but it loses it’s settings when powered off (so no good to you).

 

smuggler.ie

Is there a way to test this before you start to invest in it? As in do you have an existing large fan you could try with it to see if the moves the air in the tunnel? Run a long extension lead down and test it with a normal fan plugged in. I’ve been in one tunnel only and during hot days it was unbearably hot. But I won’t pretend to know how much air a single fan would move through a long one. You could start with that and then if you wanted, add more sophistication in time. Fans don’t use much power. But check the label on your test one to get a sense of the wattage you’ll need to move the air.

IF we take that fan can move 1000CFM that is 1700m3/h, my current poly is 6x9 semicircular , at best it can be something about 80m3 of volume, lets take 100m3 . From here, the fan with 1000CFM can completely change air in poly 17 times every hour. I do believe this more than enough, way to much, hence speed reduction needed.

Now as for sun=run, not really california/texas here. You can have bright sun out on cold day and it wont need as much ventilation as incoming air is colder. See, some vegg apparently does not like rapid temp change thus why would like to have temp control.

Ideally need some controller that would variably increase speed of fan, up to set limit, depending on temperature setting. It need to go gradually , maintaining set temp rather then jet blow from 40C to 20C

As i have no ideas about panels i need advice, dont want to buy 100W for €100 kit if there is better option for €120, dont even know what difference there could be

Cabling - what mm2 i need to go for. is 2.5mm2 enough?

DC999

https://www.boards.ie/discussion/comment/121820725#Comment_121820725

Plug I sent you does that temp regulation. Makes sense that large temp swings aren't good - I didn't know that.

If temp over X degrees, turn on plug. If below Y, turn off. Won't change fan speed but stops the temp fluctuating.