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Solar Fan hot air extraction revisited


This topic was asked about a couple of years ago but converted into comments about someone being removed from the forum. So I would like to ask those in the know what issues I might have with any vibration of the fans before going ahead

Here is the reality of my situation and thinking.
I am in Thailand
The temperature is over 36 degrees C much of the year. (40C for several months)
Bees like to maintain 34-36 degrees in the hive
The inside of the hive gets hotter than this. In Thailand they only use single or double stacking to factor this in (or the bees die or do not produce honey)
I know bees can regulate there own temperature - but why on earth would I want half the bees cooling the hive instead of out collecting honey? It makes no sense to not assist them when it is possible (it me I know others disagree)
The hive is raised 1 meter off the ground and under a shade structure. There is nothing to do extra to shade from the sun heat, it is the ambient heat that is high. In fact I need to use the solar panel wired to charge the battery since the hive area is shaded so well.

So I want to put a themostat regulated solar powered fan system in the roof area of the hive. When the temp reaches 35 degrees in the upper box, the small fans kick in the remove the hot air from the hive. The air temp of the outside will be around 30-35C

I am content to modify what the bees do naturally. In Thailand the Thai bee keepers do not, they rely on how they have always done things. I do not mind modern methods and using new knowledge. :slight_smile: I have no particular personal philosophy that bee keeping should be natural (after all I am using flowframes)

The Fans are small and run very quietly, I do not see/feel any vibration from them, but assume some small rubber washers on the screws would take care of most of any vibration.

My two concerns are

  1. how much are bees really sensitive to vibration? I see many hives along motorways that have large trucks passing by all the time. I would think this would be much higher than what I will introduce
  2. faster airflow? This method will just speed up the natural airflow from bottom to top ventilation, the fans are too small to make any real changes that would cause a draft. So how to bees cope in small breezes within the hives?

Thanks in advance.


I would try it. I do not think vibration will be issue. If to strong you could have adjustable vent near fan to help control air speed. I would try for low air transfer and adjust as you see fit. Do you use screen bottom boards? Keep us updated on results.


Great topic for the tropic.
Good quality computer case fans are relatively cheap and easy to fit. In the roof area you are extracting hot humid air so make sure it can escape.
With regard vibration use large fans 120mm to 200mm as these can extract air at much lower fan speeds (less vibration) some down as low as 750 RPM but 1100 RPM is common at an inaudible 12-14 db .
With regards draft I don’t think that would be a problem either, as the bees will just block up the vent if they think it is too drafty.
I think you just should try it. Having spent a few years in the tropics I understand the heat which just does not go away, night, day month after month. You adapt cause you can’t beat it. Unless of course you want to live in an air-conditioned house and not go out.:sunglasses:


I will be adding a screen bottom board, but the base stand of the unit will need some holes drilled into it as it is solid, and screen mesh stapled to it. The only bottom ventilation space currently is the bee entrance and since the hive is 2 weeks old, they are reduced until the hive numbers grow.


The only thought I can suggest is to mount the fans on a bed of silicone silastic as it is more flexible than rubber washers to eliminate vibration completely. Your idea is well thought out with a logical solution. The extra airflow shouldn’t put the bees off and the extra bees foraging is logical. Give us some feedback, I think a mesh bottom board is a must in your climate.


I would also change the pre-set for the temp the fan turns on to be slightly higher. My temp probes show the bees are regulating the brood space to 35.7-36.2oC. I would set the fan to come on at 38oC with a +/- 1oC for turn off.

Also if the outside is warmer than what the brood cluster is doing you run the risk of actually raising the temperature of the hive to high rather than cooling. As all it seems you would be doing with the fans is “sucking” warm in through the entrance/base through the supers and out the top, potentially raising the temp into the low to mid 40oC. Again I’d also be concerned about the humidity change that the fans are causing too brood seems to be stable around 50-70%.

As an alternative have you thought about better insulation of the hive? Could you have a local wood worker make thicker walled hives? Could you look at importing poly/plastic hives with better insulation? Could you run a long lang? This is in addition to the screened bottom board etc.

Hope that makes sense.



Good points for me to consider. I am going to spend a few hours on Sunday with them (sadly they are on a farm 39km away to force me to not obsess daily over my new hobby). I will take a combination of inside and outside temps over a few hours in the brood box, super, roof, under the base board and outside. Let’s check what the difference is in reality. You could have a great point about drawing in hotter air.

Hmm did I imply distance would impede my obsessing? Haha. At the moment it is only 30-35C so as of yet not needed.

I will see in a few days and advise.


I think you have nothing to lose by trying it, however I’d stick to the solid floor. Yes, the bees do regulate the hive temp. They actually air condition the hive according to the video “City of Bees”.
With that in mind, I see a mesh floor as a hindrance, not a help. Sorry @Peter48. It would be like us running our air conditioners with a large door open. We just don’t do that for obvious reasons.

Keeping your hive in the shade will be a big help.

Poly hives would probably be a good thing in your climate.


Interesting study done here on screen bottom boards


That’s an interesting study alright, however he didn’t look into whether it was more effective in hot humid weather or not. Only honey production.

I’d like to study the difference between the two on the days when the bees are doing a lot of bearding.

I get very little bearding on hot days. I suspect it could be on account of the solid floors in conjunction with the few mm’s of extra frame spacing that I use. I evenly space 9 frames in 10 frame supers.

I believe that similar frame spacing would also help the author of this thread.


That is my observation on my long hives as well were I am using 42mm thick walls, 25mm base and 30mm coverboards with a “roof space” above. Much less bearding for similar sized colonies in traditional lang towers with only 21mm supers.


My long hive isn’t as thick as yours- though it does have more insulation in the roof than most hives. But I also havn’t seen as much bearding on it last summer as with regular hives. This despite the fact it has a very large population inside.

@CMAndrew i was also interested in additional ventilation (and in my case winter heating) for hives- using small solar panels- the one concern I had with fans was that I would be forcing in more hot air from outside and making it harder for the bees to effectively cool the hive through evaporative cooling. It will be interesting to see how your idea pans out. If the outside temp is over your threshold for the inside temp (the temp at which your fans come on)- wouldn’t you just be pushing hotter air in? And given the high humidity- could you also risk forcing more moisture into the hive?

Edit: thinking about it more- it occurred to me that’s it’s likely the humidity in the hive would generally be higher than the air outside- so introducing air from outside might help decrease inner humidity and aid the effectiveness of evaporative cooling…


My thinking was that the heat in the hive would probably be high enough that the bees would benefit from any natural air flow they could get from a mesh floor. It may also cut down the humidity in the hive.
The bees could still fan at the entrance to evaporate water to cool the hive as per City Of Bees.


Having got to the end of this post (it took several hours off researching online) I apoligise in advance for being a little geek, trying to “Science the shit” out of this. I think I am beginning to become a fussy dad to the bee’s like some of the extreme cases you see youtube where a $100 hive has $1000 of added builds to make the beekeeper feel better. Which is really a little premature since this is the first hive, 2 weeks in and still trying to establish a strong hive population. This is probably a case of over thinking before it is needed.

I did find some average monthly air temp and humidity charts. Although now (September is supposed to be 32C it is more like 35-36 during most of the day so a little hotter in reality than averages. I did purchase a temperature and humidity display with a probe for a few dollars, and will spend the day making measurements of the difference in temps and humidity inside the two boxes and outside the hive. Although I still have a few months to wait until the heat really kicks in.

Average min and max temperatures in Chiang Mai, Thailand
Average relative humidity in  Chiang Mai, Thailand

The good news is the humidity is pretty constant over the year, the bad news is it is 20-30% higher than optimal for the bees not to have to intervene. But at least the effort required to maintain the humidity is going to be relatively constant over the year.
Is this even an issue? the result present here

suggests that is just takes 1-8 bees to adjust the humidity by this amount within a few minutes.

Then this backyard study showed that between an empty hive, insulated hive and normal hive, the humidity inside the hive closely matched the outside changes, suggesting the bees did not do much to control the humidity

So then the question becomes, what is more important? Temp or Humidity? For the sake of 5 degree reduction stabilization of Temperature using the fans, is it worth introducing new air with 20-30% more humidity? (Can a more experienced person share what their experience has taught them?)

Also I am assuming the hotter air will rise and be in the super, which as a flowframe is all plastic and I do not know if the humidity and temp there is as important as in the brood box. Can someone enlighten me on this as well? Obviously the regulation is important for the brood, how important is it for the honey super?

The more I look into this for my situation, I am beginning to thing a simple slatted bottom or an open bottom with screen mesh might be all that I need. However being the geek I am I am learning towards starting a second hive and compare a fan vs no fan option

OMG I know I over think this… These damn bees get more attention and consideration than my girlfriend at the moment. That is not a good thing haha


I was just like you when I started- eager to ‘science the shit’ out of everything- and recreate the wheel!

I just had a read of that humidity article- it’s very interesting. One big difference between the study and your conditions is likely the amount of external humidity. If you could test and see that the humidity in the hive was always higher than air coming in- then perhaps fans might help to keep the hive drier. I have read that bees can handle cold much better then they handle damp. However- it could also be that the fans will work against the fine system the bees already have in place. I think you should also consider the possibility that fans can blow a lot of fine dust into the hive…

If you are going to ‘science the shit’ out of it- you’ll be needing two hives- for a start- and at a minimum! Then you’ll be needing the probes and the sensors. Then a bigger study with more hives. And so on. Maybe in a decade you’ll have some firm data!

When I was thinking about fans for ventilating and solar powered heating for hives in winter- I decided that heating in cold climates was more likely to be an easy win for the bees- whilst the question of forced ventilation was more tricky. for the time being i’ve given up on the idea of fans- but would still like to make a small solar powered heater for use in winter and on cold nights. Soemthing very Mc Guyver- 12 volt solar- with basic parts- that just collects warmth in the day (es electricity) and releases it into the night directly below the brood- basically a creature comfort for the bees.


@CMAndrew With looking at your read outs for temperature and humidity what you have is not a lot different than I have on some days here in sub tropical Queensland Australia. Till now I was thinking you were in a more extreme climate.
The science already tells us that any air flow decreases both humidity and temperature, unless you are re-entering the earths atmosphere at super-sonic speed.
Your temperatures are well within the boundaries that bees are successfully kept at without artificial aids to the hives. Likewise I think places were bees already live wild and happy in your humidity like PNG, the Amazon Basin and other equatorial locations would have a higher humidity.
On your figures I would go for a mesh bottom board and spend more time with your girlfriend in mind and let your bees adjust to their climate.


Thanks @Peter48 I was thinking along the same lines after I found the figures (although the real temperature is higher, these averages account for the average daily temp and this area includes mountains with higher elevations, not so much the range in the exact area I am located… 35-40C would be the common, occasionally a 42C but for the sake of one or two days each year it is probably not worth it.

The wild bees are the Asian bee which is smaller and produces less honey. But the Apis mellifera which I have have been here for 40 years, so I assume adapted.

Although if airflow does decrease both temp and humidity do you happen to know how much? I did a quick google search but are not familiar enough to work out the charts and graphs. I might set it up and then take some measurements, I can always turn it off if not needed or does not work. I think a 2nd hive is in order as a control :slight_smile: I mean who wants to just have one hive? this is so much fun


am sure I have the graph somewhere among my paper work, it was used in engine carburation when I was racing extremely high performance racing engines, but it could take months to come across it. Air pressure, temperature and humidity was very critical.
You can be sure they have adapted to your location climate after that time.
Certainly, a second hive would be needed to have a base control to compare with, but you will also note that everyone advises of the benefit of a second hive, you will certainly find that as you get more involved, which inevitably we all seem to do. I promised the wife that I would have 4 hives, well it was then 6 and is now out to 10 at my apiary and 2 I look after elsewhere.


Just do it. If you don’t you will always be wondering.

Then think of the rewards…“CM Andrew an eminent authority on raising bees in the tropics will be speaking tonight at…” Your girlfriend could write the book.
Seriously though, you have it in your power to sort this out . We know very little raising bees in the tropics.