Energy saving for brewery glycol chillers

Thermal storage means brewery or cidery tank refrigeration systems don’t need to run all the time.

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The process of creating cider and beer uses too much energy. One reason is refrigeration - a typical brewery or cidery will run a glycol chiller for 2-3 weeks continuously per batch of beer or cider. The chiller keeps the cider or beer cold during fermentation and storage. Refrigeration uses on average 35% of a brewery's electricity.

By installing a low-cost, wifi controlled switch we have been able to reduce our test cidery's total electricity use by 10%. With the switch and relay we can turn off our chiller for 5 - 8 hours per day (via a schedule or manual control). The thermal mass of the beer or cider in the fermenting tanks means the temperature does not change quickly.

The ongoing purpose of this project is to develop this and other control strategies and operator controls that support energy saving during fermentation refrigeration, and to make the technical details available under an open source license for other craft breweries and cideries to implement.

Vishnu, Trevor and I are working to reduce refrigeration energy use in breweries and cideries. Trevor owns Goat Rock Cider, our test location.

Above, two out of five fermentation tanks and a glycol chiller on the right, behind the gas cylinder.

Many breweries/cideries have a system design where an air-water chiller cools a propylene glycol and water mixture and continuously circulates it in a loop. Each tank has a temperature controller that opens a valve to allow that cold glycol to flow through a metal jacket on the tank, as needed, to lower that tank’s temperature for fermentation (~60sF/15-20C) or storage (~35-45F/2-7C). The cold glycol has a 28F/-2C setpoint.

Above, we have added a simple IoT switch and DPST relay to control the chiller in parallel with its existing DPST on/off switch. They allow the chiller to be scheduled to turn off during times of peak electricity demand.  This also means that the chiller wastes less pumping energy.

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  • 1 × Chiller control - Sonoff MINI R2 wifi switch $14
  • 1 × Chiller control relay - Phoenix Contact RELAY GEN PURPOSE DPDT 8A 230V 2903347 $17 Power Supplies / Uninterruptible Power Supplies (UPS)
  • 1 × extraAC open source energy and temperature monitor $200 (Optional)
  • 1 × Glycol Chiller

  • Chiller with the wifi switch

    Tim Bishop04/28/2022 at 20:21 0 comments

    Below we can see the chiller control turning off the chiller during the late morning and afternoon of the 2nd day 11:00 - 16:30, with only a small rise in tank temperature (Tanks 2 and 3) during that period. The tanks do not change temperature very fast - this is energy storage in action, and what allows us to turn off the chiller for this time. (Tank 1 is empty and is not being chilled)

    Controlling the chiller via the wifi switch has allowed us to save 30% of our chiller electricity use, which is 5-10% of our total electricity use.

    We added tank temperature monitor / controllers so we could monitor the tank temperatures from off-site, to verify that our tanks did not change temperature too much when the chiller is turned off. We used the Sonoff TH16 ($27).

    Tracking tank temperatures has helped us get some numbers about the rate of tank temperature change at the cidery. Our 1500 gallon tanks can be cooled at a rate of 1.5F/hour. They self heat, during fermentation, at a rate of 0.25 - 0.5F/hour in our ambient temperatures.

    By watching the tank temperatures, we can turn the chiller off when we want to, and then back on when the tanks start getting too warm. This is a manual process but we are learning how long the chiller can be left off without materially affecting the ferment process.

    Sometimes the wifi temperature controllers get stuck reporting the same (incorrect) temperature. For example the purple Tank 2 temperature reported below at day 1 hour 17:30 - 23:30 is shown as a flat line when we know the temperature was actually going down following the trend. This may be a problem with the eWeLink cloud, our HA installation, or a poor wifi signal.

    As we develop this system it needs to degrade gracefully in the absence of local wifi, or the internet, or the dependence on the third-party cloud.

  • Chiller monitoring before adding wifi switch

    Tim Bishop04/28/2022 at 20:05 0 comments

    We monitored our chiller power and temperature with the open source monitor extraAC, based on the excellent IotaWatt. We attached the monitor to our glycol chiller, a labeled G&D Chiller. 3 Ton / 10 kW. Data is forwarded to the open source for offsite viewing. 

    When the tank temperature needs to be lowered during cold crashing, a lot of cooling power is needed from the chiller.  However when the tank temperature is stable, only a moderate amount of chilling power is needed to keep the temperature stable. For moderate cooling power, the compressor cycles on and off, and the circulating pump still runs. This wastes pumping energy, and energy keeping the glycol loop cool.

    Before adding the chiller control, below we can see the tanks cooling at full chiller power as of 6:00am until 13:30, then the chiller runs on partial power, PWM-ing the compressor, for the rest of the chart.  By adding an IoT switch, we can largely eliminate this second PWM part of the chart, simply by running the chiller less often by scheduling it with the IoT switch.

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