ACR Journal

April | May 2023 REFRIGERATION 16 Aldi’s desire to improve refrigeration sustainability was the focus of a paper from Conor Eaton-Smith of K2 Engineering (Cooling) Ltd to the IOR Annual Conference. Here, he looks at some of the more notable and significant approaches covered by the paper. Aldi’s route to improved sustainability Volume 9 No.3 2009-2011: Opportunistic (Non-elevated) Heat Recovery for all New Stores The recovery of waste heat had widespread application in Aldi during the late 2000s. Aldi shopfloors of the time were heated and ventilated using a single zone Constant Air Volume (CAV) system, utilising a ducted gas- fired air heater. Meanwhile, the refrigeration in the store was provided by a single remote system, making it relatively straight forward to install a pre-heating coil in the supply air ductwork for energy recovery. As a result, this type of application was an e ective solution with a simple bypass and no additional controls required. With this type of system Aldi reduced the annual consumption of natural gas used for store heating by 55% annually. 2009-2020: Fully Integrated Refrigeration & Heating Systems The first step to remove natural gas completely from its stores was with the installation of an integrated refrigeration and heating system in their Edgbaston store. This system consisted of a refrigeration pack and a single heat exchanger that would be used in working towards satisfying the store's heating demand as an air source heat pump unit. The heat exchanger had two separate refrigeration circuits to provide heat rejection from the condensing side of the pack system, but also from the discharge side of the pack to generate heat if required (false load). In addition, the refrigeration pack was designed so that five out of six compressors could transition between two suction pressure groups, those for the refrigeration load in the store and those used by the external air heat exchanger during air source heat pump operation. This integrated configuration allowed the system to e ciently meet two separate loads and optimise each Saturated Suction Temperature (SST) throughout the annual operational cycle. Furthermore, the plant requirement was reduced. Additional energy savings result from a dynamic condensing temperature setpoint, which is optimised depending on ambient conditions or heating demand levels. As a consequence, the refrigeration coe cient of performance (CoP) is reduced compared to a refrigeration-only system because of the increase in power consumption, but when heat recovery generation is also taken into account, the total e ciency of the combined system is higher than two individual solutions. As a result, the integrated heat recovery system reduced project Total Expenditure (TotEx), and along with the elimination of natural gas, reduced Aldi’s carbon footprint and meet local authority requirements for Low to Zero Carbon (LZC) energy generation. 2009-2017: Replacement of R404A with Lower GWP Alternatives From 2009, Aldi adopted new heating strategies for its estate and also reduced its refrigerant emissions liability. This reduction was achieved by adopting alternative HFC refrigerants, which have a lower GWP. Table 1 highlights the main di erences between the refrigerants historically used on the Aldi estate. 2016 Onwards: Transitioning to a Carbon Dioxide future In 2016, Aldi made the decision to transition to natural refrigerants, with R744 providing remote mid temperature (MT) refrigeration having trialled systems from 2011. Evaluating this approach from a sustainability standpoint, a dynamic model was produced Refrigerant R404A (- 2015) R407A (2009 -) R407F (2014 -) R744 (2017 -) GWP (AR4 Values) 3922 2107 1825 1 Nominal CoP 2.23 2.32 2.34 1.86 Heat Recovery CoP 2.46 2.51 2.51 2.64 Figure 1 Indicative Heat Recovery Sketch Table 1 Comparison between Aldi refrigeration types Conor Eaton-Smith