Passively regulating fermentation temperature
Passively regulating fermentation temperature
Last time I brewed at home, I had my fermentation bucket in my flat, where the heating pretty much took care about all thermal regulation I needed back then. As I now have kids, I don't feel comfortable doing that anymore for various reasons.
I have freed up some space in my garage now for brewing & fermenting, but I have no heating there. I'm OK though to go with the seasons, brewing beer styles where the yeast's preferred temperature roughly matches the weather. But now, my mind is occupied with the question of how to keep the temperature as constant as possible for fermentation: While a weather forecast of e.g. 15°C doesn't sound too bad for lager beers, it may easily get as cold as 5° at night, giving the yeast probably a rather bad time. As I also don't want to spend a fortune on a temperature regulated fermenter, I'd like to even out those mins & maxes passively.
My thoughts so far circle around insulation (obviously) and thermal mass. Insulating the bucket itself seems like a nobrainer. But I think it also might work to build some cheap wooden enclosure, insulate that with Styrofoam, make everything somewhat airtight and add water bottles, rocks & bricks to fill up as much space as possible. That will of course do little should the weather change drastically, but so far, I think I'd stay way below max and above min temperature in there at all times. This way, I believe I could get a decent fermentation when the average outside temperature of night & day is right for a couple of days.
Is anybody here doing something like that or has experiences worth sharing otherwise?
P.S.: Addressing the elephant in the room: For now, fermenting under pressure is no road I want to go down. Buying a new fermenter, kegs, valves, fittings, hoses, CO2 bottles and either a counter pressure bottling system or even switching to drafting entirely is just too much right now.
The insulated box idea is how I used to do it when I was still brewing. In fact you don't even want it to be airtight because the fermentation both generates heat and offgasses CO2, both of which you will want to allow to escape to the outside.
Depending on your batch size you might only need a few bottles of water, maybe about 20% of your batch volume, to help stabilize temps inside the chamber.
Working your brew schedule to the prevailing temperature is a fun challenge, too. I enjoyed my winter lagers as much as my summer wheats. It felt like i was keeping old traditions alive.
I didn’t mean airtight as in diver equipment, but you’re right in pointing this out because I didn’t say so. Of course there has to be a way for CO2 to escape, or I‘d be fermenting under pressure by accident.
My batch size is 20 Liters, maybe 25, I don‘t think I can do 30. What was yours? My gut tells me this is not enough thermal mass to sustain an even temperature when highs and lows spread out more than 10 °C or so.
From my last batch, I kept a few bottles for up to a year and it didn’t turn bad, so brewing with the seasons doesn’t even necessarily mean drinking with the seasons only. But yes, I like the thought as well that this is the way it has been done for centuries. Buying food in the same fashion isn’t something I always do, but it feels weird to me having fresh strawberries available all year long and I tend to avoid those.
I also did 20L batches when I was brewing. My setup was in my basement which while not actively temperature controlled did tend to maintain a fairly consistent temperature throughout the day and night. That baseline would trend close to 13C in the winter and may as warm as 21C in the summer. You may not need a lot of thermal stabilization depending on how responsive the temperature in your brew house is to the outside air.
The other thing to consider is that the temperature control is most critical during primary fermentation when the yeast are most active. As long as the temperature is maintained to their tolerance, and the whole vessel is neither rapidly heated or cooled then whatever off flavors they produce in primary fermentation they will tend to clean io during secondary, where you can even be more sloppy with your temperature. Even beers brewed with ale yeast benefit from a long secondary rest, and can produce some very clean profiles without strict temperature control.
In the end, it all depends on the kind of beer you want to produce. If you're looking for consistency batch to batch, then you'll definitely was t to control for as many variables as you can including temperature, water chemistry, strike and crash temps, your grains age, grind and whatnot. On the other hand if you're OK with some variability between batches of the same recipe and you take good notes on the process you can start to account for what factors contributed to different elements in the profile. (E.g., low ABV because it was too cold, or popcorn & bubblegum notes from too warm or too short a secondary)
For my own batches I tended not to control for temperatures during primary very much, other than to make sure I kept it within the acceptable range for the yeast I was using. I also tended to get busy and either not get around to bottling/kegging very quickly (or just forget) and so my beers tended to have that longer secondary fermentation I mentioned. (To be clear, it all just sat in the fermenter on the yeast cake for a week or three before I'd rack it off and either bottle or keg it. Didn't move it to a second fermentation vessel or anything.)
Time heals many of the woes of the home brewer. Another week rarely hurts. Just don't let it autolyze.
Anyway, I was always very happy with what I made, and I was tended to stick close to the reference styles. I usually received some great feedback from friends and family on my stuff. The guys at the beer club were less kind because, well, I'm in the US and if your beer doesn't have an oil slick and taste like dish soap because of the pounds of hops they like to use in every batch then they kinda dump on you for it.
If you want no electronics in the mix at all, insulation is about your only option. Since fermentation is an exothermic process, you'll also want to make sure you can keep it from getting too hot. Your beer will taste a lot worse from the yeast getting too hot than it will from the yeast being too cool.
You can buy inexpensive temperature controllers, and if you can do simple wiring, it's not too hard to add a power outlet (and an enclosure). From there a fountain pump some tubing, a cooler full of water and either a heat source or a cold source can serve as a simple way to regulate your fermentor's temperature.
The heat source could be something like an aquarium heater or a sous vide heater and will sit in the cooler (always on, not run to the temperature controller). You'll tape the temperature controller's sensor against the outer wall of your fermentor (with some insulation taped over it. A paper towel folded a few times works fine), put the fountain pump in the bucket of water with the fermentor, and run the tubing into the cooler. The output of the tubing should be run back into the bucket.
When the fermentor gets too cool, the temperature controller will kick the fountain pump on which will take the water from the bucket and run it through the hot water in the cooler and back into the bucket. This will slowly raise the temperature inside the fermentor - and slow is what you want with yeast.
You can replace the heater with ice or frozen water bottles if you need it to cool your beer in the warmer months. I did this for a while before moving to using a chest freezer and reptile terrarium hear mats regulated by the same temperature controllers.
For me personally, this is less an issue of electronics (which I‘m sort of fond with), but rather of actively spending energy for a prolonged period of time, be it electric or fossile. Not only are energy prices way above US levels where I live, it also feels wasteful from an ecological standpoint. Especially so since there ways around it seem to exist. For that, I‘m willing to work with seasons and weather conditions.
Good hint though that yeast typically is more tolerant towards cold than towards heat. I didn’t consider this, but leaving a good amount of headroom on the upper end of the spectrum sounds like a good idea. That said: It‘s been pretty rare that the climate in northern Germany made cooling an issue outside of food conservation. But that may change in the future.
Belgian yeast likes to get a bit hot, by the way (and the beer tastes best when fermented on the warmer side of the yeast's preferred range). That might be a decent choice for a test batch once you get an insulated space setup.
I can respect working with no power. I did that for a while too. Everything I mentioned is pretty power efficient though.
i use aquarium heaters but never cared about the energy consumption. my experience is that since fermentation is exothermic they rarely kick in. especially with larger fermenters it's usually more important to prevent it from getting too hot. so maybe running larger batches might be something for you.