BCSS - Forum

I am sure others will have done this but here's mine. I stripped three old desk top computers to salvage three 12 volt DC fans.. Bought a AC to 12 volt 2amp DC converter for £7. currently running them 24 hours a day. No heat from the transformer, designed to run 24/7, no problems. Three fans total less than 600 milli amps. Ideal for my small greenhouse to keep the air moving. Costs pennies a day to run.
Today using two but probably connect up the third for the morning due to the anticipated heat wave. I will be fitting individual switches when I get time.

A nice low cost solution!

I have been pondering ventilation for my new greenhouse setup - I have taken quarter lights out at one end and the side and roof vents are likely to stay open more or less full time over summer. However, I still think air circulation will be needed for the inevitable summer heatwave.
I don't have a power supply to the greenhouse, so was wondering if anyone has experience with small solar powered fans like these (or any of numerous variations on ebay & elsewhere):
https://www.onbuy.com/gb/usb-solar-powe ... p37894036/

After 25 years having my plants in a big 30 square meters greenhouse without any cooling, I don't really see the use of fans. I have four windows open almost throughout the year. They are only partly open as I use a brick to keep it open, the window is still down facing so it will not be picked up by the wind even if it is strong. And during the warmer weeks I also keep the door open (I have a screen in front of it to prevent birds from hopping in the greenhouse).

Using fans is in my view cumbersome, a waist of energy, always a risk of failure and risk of fire or blowing a fuse (you are watering in there too) and it provides you unnescessary costs of equipment and energy bills. All that waist while you could also use the safe and free wind energy.

We are growing heath loving plants during the day, and most are also cold loving plants during the night for photosynthesis. They can take the heath during the day very well (they run more risk getting damaged from light intensity). With windows open at night you also provide the fresh cold air the plants desperately need too!

Instead of working with fans, I would suggest to open some windows. If you don't have many windows, I would suggest to take out a pane or two on opposite sides of the greenhouse to let air in during the warmer weeks of the year. Most panes are easy to remove and just as easy to put back in when they need to.

I think part of your experience though might be related to the size of the greenhouse? In such a large space it takes longer for areas to heat up and cool down where, in a small greenhouse they might need extra help.

I say this as I was thinking about this yesterday when I got a phone call to say that the fire alarm sensor in my office at work had gone off as the temperature had got so hot!

It has no fans running to move the air at the weekends but the small cacti and succulents seem to do really well. I wonder if it is just the volume of air that stabilises the environment and allows air currents in the space to prevent plants getting too hot?

I also have a 5 square meter greenhouse as of this winter. It has one tiny window that can be opened. But I just keep the door open. It is a bit cooler than in my big greenhouse currently. Its 22C outside in the shade, but with a lot of sun intensity all day and a wind force of only 2 beaufort). My greenhouses both get 100% of the sunlight from dawn to dusk.

Risk of fire with the set is nil, not worth further comment.
Cost of solar panels far outweighs the very small cost of running the fans from a small AD/DC Converter of a type used for home CCTV systems. I have had one running in the house 24/7 for 9 years.
It costs pennies a day to run.
Each to their own and there are a lot of growers in the UK who use all manner of fans, they cannot all be wrong!

My experience is the opposite of Aiko's - in my greenhouse, I have 800W of fans which shift a considerable amount of air, and still do not keep the place as cool as I would like on sunny days, even with all the windows and doors wide open.

I can hardly imagine that a few computer fans consuming a total of 10W do much to affect the overall temperature - although they may prevent pockets of hot air building up close to the fans. I'm afraid the argument that "a lot of people do it therefore they can't all be wrong" is just illogical. An awful lot of people fall for scams - yet they are all wrong.

Hi Ralph. I think you have not grasped what I was saying. I was merely pointing out that Aikos wrong. Lots of folk have fans of all types and they work. He was saying they are a waste of time, you obviously don't agree with him either. Also his comment about a fire risk is simply wrong. Much bigger fire risk in the winter when the Bio Green electric fan heater is running
My system works, sorry but I know, its my greenhouse and all the flower stems are moving throughout the greenhouse with all the windows and door closed. Its only a small greenhouse and I know they would not be enough for anything bigger. You may have noticed the sheets of yellow fly catches in the photo? the movement of air from the fans moves them also.
Your reference to scams? how does that fit into my original post please.
BTW I don't suppose it matters much but I have a degree in applied physics and like to think I have some idea what I am doing accepting the aged brain is not what it once was.

Over the years most of my autovents had gradually failed and I didn't realise how poor the ventilation had become until I replaced them all last year, along with automating the louvres. There's far more air movement now though I've never used fans. Whilst there's not much danger in a 12volt fan, they still wouldn't appreciate my hose pipe watering methods. I can't see any harm in using computer fans but taking out a couple of panes of glass would probably have more effect.

Stuart

ralphrmartin wrote: ↑Sun Jun 13, 2021 10:34 pm My experience is the opposite of Aiko's - in my greenhouse, I have 800W of fans which shift a considerable amount of air, and still do not keep the place as cool as I would like on sunny days, even with all the windows and doors wide open.

Intake fans or circulation fans?