3 Ravens Brewery, Melbourne - heat pumps for beer production

Melbourne’s oldest independent brewery, 3 Ravens, has embarked on a clean energy transition, installing a range of technologies including a chiller heat pump and solar PV, which will allow it to ramp up production of its craft beer range without increasing its energy consumption and emissions.

3 Ravens Brewery, established in 2003 and located in Thornbury, may be Melbourne’s oldest independent brewery, but the team behind it are looking to the future with a plan to quadruple production of their much-loved beers while also optimising the energy management of their facility to minimise harm to the environment and maximise community benefits. In a market with consumers increasingly sensitive to carbon footprints and sustainability, 3 Ravens’ efforts will help control energy costs and see the emissions per serving drop dramatically, providing a source of differentiation with other producers.

In consultation with Regenerate Engineering, 3 Ravens developed a plan to modernise and expand its production facilities by up to 400% utilising best practice technologies and a holistic integration of their processes. In 2020, 3 Ravens kicked off efforts to save energy and improve internal temperature management and comfort in the facility by installing a cool roof and 74 kW of solar PV. This was followed by a building fabric upgrade of 3 Raven’s Co-Brew co-working space in 2021 which included the installation of insulation and air-tightness sealing measures.

The strategy and design to deliver high efficiency performance suited to the processes of a brewery were planned carefully in partnership between 3 Ravens and Regenerate Engineering. The planning was aided by pre-feasibility and feasibility studies managed by the Australian Alliance for Energy Productivity (A2EP) and funded by the Australian Renewable Energy Agency (ARENA) through its Advancing Renewables Program.

In May 2023 Regenerate Engineering won a National Energy Efficiency Award for the best SME Energy Management for the 3 Ravens project.

Project background

At the 3 Ravens brewery, process heat is used for the following processes:

• Hot liquor production for steeping and mashing beer ingredients

• Heating up and vigorously boiling wort

• Cleaning in place (CIP)

while process cooling is used for:

• Fermentation cooling (glycol system)

• Cold liquor production (potable system)

• Crash cooling processes (glycol) Cold conditioning (glycol)

3 Ravens has always been an electric-only brewery, but those electric processes have not been very efficient. Before the recent upgrade, a 15 kW resistive element was used to preheat filtered water (hot liquor) and then 55 kW of elements were used to further heat then boil the wort produced from that hot liquor and the mash ingredients. Two chillers were operating independently to produce chilled glycol treated water and chilled filtered water (cold liquor) to operate all process and ingredient cooling services. At the site there were several ageing electric reverse cycle R22 HVAC split systems to provide space cooling and a cold storage facility.

3 Ravens was looking for a better solution than upgrading the business-as-usual (BAU) equipment to cope with the planned larger volumes. Sticking to the existing equipment while ramping up production would see the brewery’s energy costs skyrocket in addition to a costly upgrade to the site’s electrical capacity. Plus, continuing with the BAU equipment would also create a significant liability with the HVAC equipment as the phase-out of harmful R22 refrigerants continues.

Project proposal

All energy consumption savings and business models for the energy upgrade at 3 Ravens were based on a holistic view of the upgraded operation and site compared with a business-as-usual upgrade using current technologies. 3 Ravens and Regenerate Engineering looked beyond just technological fixes to consider how the approach to the brewing process could also be adjusted to get the most out of the new equipment and maximise energy productivity for the business.

Chiller heat pump

First it was proposed to largely replace the inefficient and separate heating and cooling processes with a single cycle, flexible CO2 refrigerant chiller with advanced heat extraction, also known as a chiller heat pump.. This would effectively combine these processes with the required heating being sourced from the resultant by-product of the cooling functions. So, the waste heat from the provision of cooling would be used and upgraded to supply the heat also needed.

With the support of ARENA and A2EP, an extensive feasibility study was completed including a detailed mass/energy balance of the process, applying pinch analysis principles to the analysis and development of options. The analytical work detailed how the proposed equipment can be integrated into the current plant, including the extensive upgrades that would be required. An expansion of the initial proposal into space heating and cooling (HVAC) services for public spaces at the site was recommended due to further thermodynamic and cost efficiencies which were identified in the process.

The challenges of using heat from chillers as process heat

All breweries have chillers which have a glycol tank as storage. Every chiller, by virtue of the laws of physics, makes more heat than cold, but traditionally the heat is airborne and a nuisance rather than a resource. To this point in brewing, heating processes have rarely been integrated with cooling

Typically, heat pump systems work best operating in a constant state (optimised with variable speed systems), however, brewing is by nature a batch process. Where the heating and cooling services come from the same machine it is a challenge to ensure that the system can produce both thermal streams where they are not required at the same time. While the brewing is still a batch process, the key to success in making this work is system flexibility, redundancy, increased storage and better use of heat exchangers in the process. This can ensure that the chiller heat pump can run for quite long periods. All these aspects will be driven and managed at 3 Ravens through advanced programmable logic controller (PLC) from Fermecraft, which utilises Industry 4.0 technology to automate the brewing to maximise energy efficiency.

Using the thermal model with scenario modelling, operational range was analysed according to worst-case usage profiles of different brew recipes and schedules, including sour beers which require cooling and steeping after inoculation and then re-boiling after an initial short boil. Seasonal performance of the CO2 chiller heat pump system was accounted for, as efficiency – or coefficient of performance (COP) – varies according to ambient conditions. Further, when HVAC is added, the system needs to be robust to withstand the seasonal extremes in demand that this adds. It is worth noting that the cool roof installed at the facility is expected to increase the more efficient ‘cool weather’ CO2 season by helping the roof-mounted gas cooler run more efficiently.

Requirements to enable the system to function

The chiller heat pump can operate in two modes: transcritical (TC) or subcritical (SC). In TC mode it can simultaneously produce the three thermal streams, and in SC mode it can do cold and medium.

If there is no demand for medium heat in either TC or SC modes, the heat automatically diverts to a gas cooler. The gas cooler and/or the medium heat service is required to cool the CO2 again to enable the cycle to run. It’s important to note that if either of the heating energy services are required then the cooling cannot be turned off, as the equipment is essentially a chiller, albeit with advanced heat recovery systems. Thus, having adequate storage, especially cold storage is critically important as otherwise the unit can turn off when more heating is needed.

• Two intermittent thermal energy streams with storage – cold (-5 °C) and hot (90 °C)

• A third on-demand stream – medium (50 °C)

• Space in storage tanks for hot and cold thermal streams, or just cold when in SC.

Technologies installed for the energy upgrade:

45 kW variable duty Enex CO2 chiller with advanced heat extraction

• Heat pump can switch from SC mode to TC mode

• External Enex adiabatic gas cooler to complete CO2 cycle

• Additional heat exchanger to intercept and use mid-temp thermal stream for HVAC purposes, if required.

Thermal battery and distribution systems

• The standard-sized glycol tank has 29kWh of latent energy storage (phase change materials [PCM]) added to increase storage size. It should be noted that alternatively a larger tank could have been specified. However, the PCM was added to the existing tank as a bit of an experiment to see if the thermal storage of the existing tank could be increased instead of just replacing it.

• Additional heat exchange coil in the cold liquor tank to facilitate further latent energy storage via ice building alongside glycol jacket

• An in-line heating heat exchanger to heat wort en-route to the kettle

• A new stratified hot liquor tank – additional to old hot liquor tank which is now a batch tank

• Careful re-design of pipelines and tanks so that they can stratify correctly and the addition of multiple temperature sensors to monitor state of charge of hot and cold thermal batteries.

Hydraulic thermal distribution systems and air handling

• Fully re-designed balanced header glycol circuit, supplying cooling and fan coils for hop freezer and cool room

• Mid-temperature thermal loop and tempered cold glycol to supply fan coils in public spaces

• Full HVAC in occupied spaces which controls heating and ventilation levels with CO2 and temperature sensing sized by use of analytical energy modelling of spaces post building fabric upgrade.
  

Applications and reduction of resistive heating duty

Although all of the hot liquor and cleaning in place (and part of the wort heating process) are carried out with the renewable heat technology (heating from 65° C to ~85° C) the residual wort heating process and following vigorous boil need to be carried out by the elements. Overall, more than 50% of the process heating is carried out by the chiller heat pump using renewable heat energy, with the rest carried out by the heating elements, significantly reducing the energy consumption and required input energy for a brew cycle.

Managing the transition from harmful refrigerants

The upgrade at 3 Ravens involves the removal and decommissioning of a significant amount of refrigerants with high global warming potential (GWP) gas from largely ageing equipment. As well as the two chillers, the removal of 35kW of R22 HVAC equipment adds to the environmental performance at 3 Ravens by retiring a significant amount of high GWP refrigerant nearing end of life. The emissions noted in the table below would only damage the environment if released, although it is likely that this could occur over time to some or all of the equipment , which is all close to end-of-life. As an example of this, the now removed Chiller 1 previously leaked all its R22 refrigerant and was re-gassed with R438a, which was recommended as an environmentally friendly R22 replacement, even though it still has a GWP of 2265 (more than 100 years) which is worse than R22’s 1760. The upgraded plant’s refrigerant is CO2, so the liability from potential refrigerant leakage can be removed.

Project costs for energy upgrade

• Capital cost (excluding GST) - $220,000

• Net energy cost savings (annually) - $33,800

• Net reduction in energy consumption for affected processes (brewing, cold storage, HVAC) - 525 GJ/year (76%)

• Simple payback period - 6.5 years

*Note: these costs do not include the solar PV, cool roof and building fabric upgrades.

Key project statistics and current state of play

As of June 2023, the new system has been commissioned. It will be closely monitored and as 3 Ravens adjusts to the new system, tweaks and adjustments will be made. It is anticipated that the impact of the system will be a huge improvement in energy productivity for 3 Ravens, with estimates included below.

Non-energy benefits

The energy upgrade influenced various non-energy benefits, including increased comfort and improved ventilation within the facility. It also resulted in a reduced liability for the release of climate-damaging refrigerants, enhanced brewing automation, increased brewing throughput, and positively impacted marketing and brand strategy.

Scalability and replicability for other breweries

There are more than 600 independent brewers around Australia and all are facing pressure from the rapidly rising cost of the energy they need for production. The process in this pilot project is scalable and replicable although modelling will need to be adjusted each time. Rolled out across the brewing industry, the energy and emission savings could be substantial.

By using the same process as the pilot project, the overhead cost of manufacturing a special build chiller heat pump is amortised to reduce the cost per kilowatt of the installation. It is unlikely that many medium or large brewers will have an all-electric brewery like 3 Ravens. Given this, Regenerate Engineering would recommend a two-stage process to produce low pressure steam for further projects, especially as the scale increases.

Project client: 3 Ravens

Energy consultant: Regenerate Engineering

Technology partner: Minus40