Ask The Brewmasters

Hello Forum,

I'm trying to get a handle on direct utility costs of producing a barrel of beer. One area I'm struggling with is the cost of operating the glycol chiller. Calculating the energy required to cold crash a tank seems straight forward, the energy required to maintain temperature during active fermentation or post cold crashing a little more convoluted but I've seen some estimates out there. The part I really struggle with is estimating how efficiently the chiller operates and how much energy it consumes during this process.

I found some estimates on another forum as follows:

Active fermentation is ((BBL * 4200 BTU) / HOURS-OF-FERMENTATION) = BTU/HOUR
Pulldown is ((BBL * 271 * (start temp - finish temp)) / HOURS-OF-COOLING = BTU/HOUR

So if those formulas are correct or close enough for a decent estimate, how do I figure out the energy consumption in kWh at the chiller?

Thanks,

Corey

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Corey Zschoche
Head Brewer
Callsign Brewing
North Kansas City, MO
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Always a tricky one. You're trying to attempt a mass energy balance and I commend you for it. 

You're off to a good start, as for the chiller, you're going to want to look at the name and see what it takes in COP (coefficient of performance). This will also (hopefully) have a whole chart giving you the amount of power consumed by the chiller to effect a given amount of cooling. Where it gets tricky is the temperature on the condenser (hot side) of the chiller has a lot to do with its efficiency. The lower the difference between the hot side and medium that's absorbing the heat (the air most likely) the worse it gets. Keep this especially in mind if you'll be operating in a hot area of the globe and make sure you de-rate your chiller accordingly (oversize the chiller to make up for poor environmental performance). 

Not doing this kind of mass balance work is why that vast vast majority of chillers are undersized and summer is filled with instagram photos of brewers hosing down condenser coils... 

If you're looking for a more in-depth series of calculations let me know. 

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David Kyrejko
The Engine Room
Brooklyn NY
------------------------------

The first equation can't be right. The heat released by fermentation comes from the reaction of sugar, so the heat to be removed comes to  

change in sugar conc x amount of wort

The cooling rate would take the form:

kW of cooling = degrees Plato decrease per hour x Kg of wort x 500 kJ/kg extract / 3600 s/hr /100 (to convert deg P to a decimal fraction). 

Thermodynamics of fermentation are discussed in Williams LA. 1982. Am. J. Enol. Vitic. 33(3): 149-153.

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Roger Barth
Author (with M Farber) of Mastering Brewing Science ISBN 9781119456056
Retired
West Chester PA
------------------------------

Original Message:
Sent: 10-19-2023 18:06
From: David Kyrejko
Subject: Utility Costs

Always a tricky one. You're trying to attempt a mass energy balance and I commend you for it. 

You're off to a good start, as for the chiller, you're going to want to look at the name and see what it takes in COP (coefficient of performance). This will also (hopefully) have a whole chart giving you the amount of power consumed by the chiller to effect a given amount of cooling. Where it gets tricky is the temperature on the condenser (hot side) of the chiller has a lot to do with its efficiency. The lower the difference between the hot side and medium that's absorbing the heat (the air most likely) the worse it gets. Keep this especially in mind if you'll be operating in a hot area of the globe and make sure you de-rate your chiller accordingly (oversize the chiller to make up for poor environmental performance). 

Not doing this kind of mass balance work is why that vast vast majority of chillers are undersized and summer is filled with instagram photos of brewers hosing down condenser coils... 

If you're looking for a more in-depth series of calculations let me know. 

------------------------------
David Kyrejko
The Engine Room
Brooklyn NY
------------------------------

The first equation can't be right. The heat released by fermentation comes from the reaction of sugar, so the heat to be removed comes to  

change in sugar conc x amount of wort

The cooling rate would take the form:

kW of cooling = degrees Plato decrease per hour x Kg of wort x 560 kJ/kg extract / 3600 s/hr /100 (to convert deg P to a decimal fraction). 

Coolong requirements are briefly discussed in Farber M, Barth R. 2019. Mastering Brewing Science: Quality and Production..p 286.(citation below).

Thermodynamics of fermentation are discussed in Williams LA. 1982. Am. J. Enol. Vitic. 33(3): 149-153.

------------------------------
Roger Barth
Author (with M Farber) of Mastering Brewing Science ISBN 9781119456056
Retired
West Chester PA
------------------------------

Original Message:
Sent: 10-19-2023 18:06
From: David Kyrejko
Subject: Utility Costs

Always a tricky one. You're trying to attempt a mass energy balance and I commend you for it. 

You're off to a good start, as for the chiller, you're going to want to look at the name and see what it takes in COP (coefficient of performance). This will also (hopefully) have a whole chart giving you the amount of power consumed by the chiller to effect a given amount of cooling. Where it gets tricky is the temperature on the condenser (hot side) of the chiller has a lot to do with its efficiency. The lower the difference between the hot side and medium that's absorbing the heat (the air most likely) the worse it gets. Keep this especially in mind if you'll be operating in a hot area of the globe and make sure you de-rate your chiller accordingly (oversize the chiller to make up for poor environmental performance). 

Not doing this kind of mass balance work is why that vast vast majority of chillers are undersized and summer is filled with instagram photos of brewers hosing down condenser coils... 

If you're looking for a more in-depth series of calculations let me know. 

------------------------------
David Kyrejko
The Engine Room
Brooklyn NY
------------------------------

If you really just want to know how much it costs to run your chiller, just get one of these...

Amazon.com: Universal Electric kWh Meter - Omnimeter I v.3 : Electronics

They make several different flavors so make sure to get the correct one for your chiller.

- Reuben

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Reuben Mergen
President
Vortechs Automation Inc
Huntingdon Valley PA
(215) 322-6788
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