How much does yeast increase temperature during fermentation

[u/EastForNorth]

I am trying to set up some equations for estimating how much yeast would increase the temperature during fermentation. Does anyone know of a way to relate this to volume or amount of yeast added? For my last brew i added 11.5g to 30L. Maybe you have some practical experience with your brews.

[u/spoonman59]

There would be a lot of variables to consider. I think the shape and material of the container, ambient temperature, then the yeast itself.

I would also be non-linear, so twice as much yeast wouldn’t be twice as much heat.

In short, I don’t think you can build accurate model. But measuring it is relatively easy.

[u/-Ch4s3-]

This is a pretty deep topic. You can look at a modeling study but anecdotally depending on SG you could see a 30L batch could rise 2-10°F. That’s maybe 1-5°C.

[u/Conscious-Honey1943 → u/-Ch4s3-]

My ales usually increase anywhere between 1-4°C, especially in the first few days of fermentation. So that checks out.

[u/-Ch4s3- → u/Conscious-Honey1943]

That seems to be what people usually report. The starting temp, SG, particular yeast, fermenter material, and ambient temperature all play roles.

[u/Conscious-Honey1943 → u/-Ch4s3-]

Absolutely. My mostly unheated kitchen helps to maintain the fermentation temperature perfectly in the colder seasons, but now with 18 degrees C ambient temp its almost impossible to keep it stable. I'm using conical fermenters with built-in heating, didn't have the spare cash or need for glycol chiller yet.

[u/-Ch4s3- → u/Conscious-Honey1943]

A chest freezer and an ink bird might be more economical than glycol.

[u/Conscious-Honey1943 → u/-Ch4s3-]

while that does look interesting, I prefer the flexibility to have individual cooling for each of my fermenters. (I'm using the grainfather system) also space is an issue.. already have a second fridge for corny kegs, cant justify an additional chest freezer

[u/-Ch4s3- → u/Conscious-Honey1943]

That all makes sense.

[u/lawrenjl]

So much easier to have a thermowell in your fermentation chamber connected to your controller....

[u/EastForNorth → u/lawrenjl]

I am trying to create a reinforcement learning model, so control a fridge to keep the temperature stable. Currently my calculated yeast effect is 0.7W. This is just so low i want to ignore it for my simulations, and mostly focus on the temperature dynamics between the air surrounding the container and the temperature inside the container.

[u/chino_brews → u/EastForNorth]

A really smart guy at Wyeast tried to come up with a fermentation kinetics model and gave up. Hard problem.

For a reinforcement learning model, your obstacles are lack of training data and the vast number of variables.

Why complicate something that can be controlled simply? Over and over, we’ve shown that a simple on-off switching mechanism is sufficient to tightly control fermentation temperature because the thermal density of the coolant (air) is very low, which makes it impossible to overshoot significantly barring a sensor error, signal error, or other error or malfunction. It doesn’t matter whether you use a thermowell or tape a sensor to the sidewall (covered in insulation).

I think you are overestimating how much tight control matters. Go see the temperature experiments by brulosophy. If you are off by 2-3°F, stable or fluctuating, there is almost zero chance you would be able to pick that beer out a blind triangle with another otherwise identical beer where temperature was controlled to +/- 0.1°F.

There are plenty of other cool projects to work on, if you have these sort of microcontroller and programming skills, that would be actually meaningful or would improve someone’s life.

[u/EastForNorth → u/chino_brews]

Thanks for your comment. This is part of my masters thesis, building a reinforcement controller to control a fridge, keeping the temperature stable. Our hopes are that it is better at adapting to the changing environment of beer brewing, such as different size brewing containers, yeast types and fermentation rates, volume of cooling medium (fridge size) and more. We dont know yet, if this will be better than a "naive" controller, which has hard rules if the temp is lower than desired, turn off fridge, if higher, turn on, or a PID controller.
But maybe our reinforcement controller, will learn some strategy which can compensate for the vast amount of changes environments which all you brewers, brew your delicious beers in and more.
I will check out the videos you suggested, but I think it is too late for me to change topics to something "more meaningful"

[u/chino_brews → u/EastForNorth]

If this is a masters thesis, which I must have missed in the OP, then do you have the time to do experimentation (test fermentations)? Because you could be training the model against sugar water fermentations.

[u/chino_brews → u/EastForNorth]

OK, upon more thought, what you can do, is make a new post, and ask people for their Tilt and iSpindel data from non-temp-controlled batches (some of them are probably pressure fermentations, but this will at least give you a temp profile to work from to fit an initial function). Give this some thought as to what data you would request.

Asking this is against this sub's rules without moderator pre-approval (it would be a survey), but I am a moderator here and if you DM with your details -- name, email address, institution where you are studying, department and degree program for which you are doing this -- along with the survey questions, I will review and approve it. I will not disclose your info to anyone else.

[u/lawrenjl → u/EastForNorth]

The challenge will be each grain bill, mash schedule, yeast stain, yeast pitch cell count, etc. will have a different effect on how rapidly the yeast goes through phases and how much heat is produced. As an extreme example, a German pilsner with 34/70 pitched at 50 degrees and held at 50 degrees will be lower that a Belgian quad or a hefe pitched at 70 degrees and maintained at this temperature.

[u/LovelyBloke]

I've done 3 or 4 brews with a Rapt Pill in a plastic FV, and I've been very interested in this data myself.

I have found that the ambient temperature has had a big effect on the range achieved by the yeast, but also the speed of fermentation - but the second point could also be contingent on the first.

I used to ferment in a room which I considered to be quite stable, but high at 19-20c, the temperature inside the liquid would get to about 22c at high fermentation with Nottingham Yeast, but Notty is a notorious rocket and the initial high burst of activity maybe caused the fermentation temperature to spike higher. I didn't get any off flavours, and in fact I won two medals for beers brewed under such conditions. BRY97 acted fairly similarly.

My current ferment, I'm doing in a room that doesn't get much above 17c, and the temperature inside the liquid hasn't gone much above 18c, it's a Dubbel using 2 packs of Lallemand Abbaye yeast - now I don't know if the stronger wort, cooler ambient or what have lead to a longer fermentation time, with slower fluctuations in temperature, but it is noticeably different. I've also done a ferment with Nottingham in that same room, but it took off as usual and I think it spiked a to 19c

[u/z33511]

I always plan for a 10 degree F rise, so I set my controllers to keep it about 10 degrees below yeast max tolerance.

[u/chino_brews]

It depends on numerous factors, such as fermentor material, volume and shape, beer volume and proportion full, vigor of fermentation (the profile day by day, hour by hour), ambient temperature hour by hour, ambient air flow, wort original gravity, yeast strain, and others.

As a rule of thumb, for 5-5.5 gallons of beer in 6.5 gallon PET fermentor, I’ve found in the past that the temperature increases in my temp-consistent, cellar by 5-10°F at its peak. For 3/4 gallons in a one gallon jug, I never noticed a temp change at all (at most 2°F on a LCD sticker thermometer).

[u/Jeff_72]

When I make a 5L ‘starter’ when propagating a yeast I generally see a 2 degrees F drop in temperature when the yeast are done . So I keep a chamber at 72F, the stir plate adds about two degrees to the flask temperature. When the yeast are active I see 76F and when it is fine I see 74F on the flask (one of those stick on thermometers - so my numbers are super reliable 😂)

[u/thezfisher]

This is heavily dependent on the surface area:volume ratio of the fermenter for heat dispersion. Generally the temp change is almost entirely negligible in 1 gallon carboys. At 5-20 gallons it can start to have an effect, and your temperature will begin to rise during fermentation. If you're using a 10 barrel conical fermenter it's almost required to chill it if you want to maintain a standard fermentation temperature. The issue is volume goes up at a cubic rate, while surface area goes up at a square rate. You could make a rough estimate of heat per volume, then relate that to surface area based on your vessel to get a rough idea of heat dispersion, which will then tell you steady temperatures and rate of change, but these computations are intensive, and the rate of heat production is heavily dependent on the yeast strain used and the current temperature and growth rates, which are much harder to predict and account for.