I bought myself a thermoelectric wine cooler a while ago as a brew fridge. It has a Peltier Effect element in it which is basically a solid-state heat pump.
Reading about temperature control, I dutifully went about building a microcontroller-based temperature controller. The technique I used was a fairly standard way of controlling a fridge - when the temperature of the probe hits a certain value, turn on the fridge until the probe hits another given value and then turn the fridge off. Lather, Rinse, Repeat...
I watched the temperature of my probe oscillate between my two set-points - 0.5degC apart. This happened slowly with a fermenter of plain water, but quickly with a fermenter of fermenting beer. I wasn't happy.
Then I started reading about Peltier devices in process cooling. I learned that lots of people (including, I now understand, the people who designed my wine cooler) use Pulse Width Modulation techniques to continuously vary the effectiveness of the Peltier. This can get as complicated as you like, and then some, but basically what happens is (as I have observed) the temperature at my probe (sitting against and underneath the fermenter in a small well against the floor of the unit) has sat at 17.1degC for the last day.
Ignoring the actual value, what this tells me is that by using this device, I have a very constant temperature for my fermenting beer - at least within the accuracy of my temperature probe - and that the Peltier is removing from the cabinet the exact amount of heat generated by the fermentation and lost through the cabinet walls.
Refrigerator and FridgeMate users will see the temperature at the probe vary between the upper/lower limits built into or set in their controller as I did.
I would guess that the theoretical temperature for good yeast performance would be a stable temperature, but I wonder what sort of temperature fluctuations yeast are comfortable with in the real world?
Thermoelectric wine cooler versus Compressor-based fridge.
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SpillsMostOfIt
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Thermoelectric wine cooler versus Compressor-based fridge.
No Mash Tun. No Chill.
No confirmed fatalities.
No confirmed fatalities.
Spills,
I use a standard fridge for mine with a FridgeMate.
I have 3 thermometer probes - on the fermenter, in the fridge and outside of the fridge.
Fermentation being exothermic, I attach the FridgeMate probe to the fermenter itself.
Although I get variance in the fridge temp, what is more relevant is the fluctuating temperature of the beer. Given the volume of a batch of beer, it is extremely slow to change temperature. My beer fluctuates about 2C however the fluctuations are very slow, with the outside (ambient room) temperature being the main variable.
I would say this is highly acceptable for the yeast, in the real world it's a different story obviously but then again the yeast we use is bred for being kept at certain temperature ranges. That said all yeast has a strong desire to live and to create beer at whatever temperature. Just like me really!
I use a standard fridge for mine with a FridgeMate.
I have 3 thermometer probes - on the fermenter, in the fridge and outside of the fridge.
Fermentation being exothermic, I attach the FridgeMate probe to the fermenter itself.
Although I get variance in the fridge temp, what is more relevant is the fluctuating temperature of the beer. Given the volume of a batch of beer, it is extremely slow to change temperature. My beer fluctuates about 2C however the fluctuations are very slow, with the outside (ambient room) temperature being the main variable.
I would say this is highly acceptable for the yeast, in the real world it's a different story obviously but then again the yeast we use is bred for being kept at certain temperature ranges. That said all yeast has a strong desire to live and to create beer at whatever temperature. Just like me really!
Coopers.
Spills,
I've also wondered if a +-2C fluctuation from ideal temp is ok for the yeast, my downstairs area where I brew is double brick, and the room temp stays fairly stable. At this time of the year my brews stay at about 20C, that's without a fridge.
So, there is a lot of talk about keeping brew at constant temp, but what is the acceptable fluctuation ? As Pale said
I've also wondered if a +-2C fluctuation from ideal temp is ok for the yeast, my downstairs area where I brew is double brick, and the room temp stays fairly stable. At this time of the year my brews stay at about 20C, that's without a fridge.
So, there is a lot of talk about keeping brew at constant temp, but what is the acceptable fluctuation ? As Pale said
So is the answer: as long as it's within range of the yeast brewing range, and averages the ideal temp, is that as good as being at the constant ideal temp ?I would say this is highly acceptable for the yeast, in the real world it's a different story obviously but then again the yeast we use is bred for being kept at certain temperature ranges. That said all yeast has a strong desire to live and to create beer at whatever temperature. Just like me really!
No, I don't believe it is as good. For instance a yeast might have a range of 16-28C but obviously letting it get above around 22 is going to be very estery.cleverpig wrote:So is the answer: as long as it's within range of the yeast brewing range, and averages the ideal temp, is that as good as being at the constant ideal temp ?
Therefore if it was 28 for 2 days then 18 for the next day then 24 for the next 3 days, the average temperature would be 24.33C but the yeast is having to adjust to the different temperatures, as well as the esters being created at the highger temperatures.
I think the less fluctuation the better but my point earlier was if the flucatuation is only 1-2C and it is kept at a good temperature i.e 16-18 for ales, then for me this is acceptable in the less than perfect science of home brewing
Coopers.
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SpillsMostOfIt
- Posts: 789
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- Location: Collingwood, Australia
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SpillsMostOfIt
- Posts: 789
- Joined: Friday Nov 24, 2006 5:07 pm
- Location: Collingwood, Australia
I can't help you with the wife bit, but I have observed a couple of things, which I will mix in with some theories and thoughts...
Less fluctuation must be better. This means that driving the temperature of your beer from one set-point to another can't be perfect. This suggests that if you're using an on/off arrangement (as you would for a compressor-based fridge controlled by a FridgeMate) that to minimise the amount of fluctuation in your beer you should monitor the air temperature surrounding the beer.
Monitoring the temperature of the air surrounding the beer is not good. You will be turning the fridge compressor on and off more often, due to the thermal mass of the air in the fridge being comparatively small, leading to more noise and shorter fridge lifespans.
Fermenting beer obeys the laws of thermodynamics, as do modern refrigerators.
If you want your beer to be at 18degC and it is at 24degC, when you set your temperature controller to 18degC, it will take time for the beer to get to that temperature, so a significant amount of the fermentation will happen at a temperature other than you want. Also, the amount of heat that needs to be drawn from the fermenter changes during the fermentation process, making things more interesting.
I reckon that an intelligent system is required that has multiple probes, watching the temperature of the beer and the inside of the fridge. I haven't worked out the algorithm yet, but the process is probably within the range of one otherwise unemployed human.
Alternatively, pitching your yeast at fermentation temperature (or close to it) as opposed to a considerably higher temperature, seems to work. This does mean you need to do all you can to ensure your yeast are otherwise happy.
I am increasingly pleased with my choice of Fermentation Cabinet. I just need to replicate the function of the PWM circuitry in it so I can get it heating as well as cooling...
Less fluctuation must be better. This means that driving the temperature of your beer from one set-point to another can't be perfect. This suggests that if you're using an on/off arrangement (as you would for a compressor-based fridge controlled by a FridgeMate) that to minimise the amount of fluctuation in your beer you should monitor the air temperature surrounding the beer.
Monitoring the temperature of the air surrounding the beer is not good. You will be turning the fridge compressor on and off more often, due to the thermal mass of the air in the fridge being comparatively small, leading to more noise and shorter fridge lifespans.
Fermenting beer obeys the laws of thermodynamics, as do modern refrigerators.
If you want your beer to be at 18degC and it is at 24degC, when you set your temperature controller to 18degC, it will take time for the beer to get to that temperature, so a significant amount of the fermentation will happen at a temperature other than you want. Also, the amount of heat that needs to be drawn from the fermenter changes during the fermentation process, making things more interesting.
I reckon that an intelligent system is required that has multiple probes, watching the temperature of the beer and the inside of the fridge. I haven't worked out the algorithm yet, but the process is probably within the range of one otherwise unemployed human.
Alternatively, pitching your yeast at fermentation temperature (or close to it) as opposed to a considerably higher temperature, seems to work. This does mean you need to do all you can to ensure your yeast are otherwise happy.
I am increasingly pleased with my choice of Fermentation Cabinet. I just need to replicate the function of the PWM circuitry in it so I can get it heating as well as cooling...
No Mash Tun. No Chill.
No confirmed fatalities.
No confirmed fatalities.
-
SpillsMostOfIt
- Posts: 789
- Joined: Friday Nov 24, 2006 5:07 pm
- Location: Collingwood, Australia