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Tesco achieves 10% energy cuts with Star’s Ethos

UK: Star Refrigeration’s Ethos performance optimisation and monitoring system has enabled Tesco to save a massive 4GWh of energy across eight of its distribution centres in just 21 months.

The savings, from results gathered from the period January 2022 to September 2023, represented an impressive average energy saving of 10% across the supermarket group’s eight sites and achieved a return on investment in under three months. 

Star’s Ethos is a stand-alone device described as an AI-enabled, data-driven performance optimisation and monitoring system which identifies efficiency problems. It harnesses the power of real-time data to analyse current plant operations and compare it with an AI-generated model of theoretical performance based on the original design expectations. The system then identifies performance gaps and provides recommendations to enable businesses to make informed decisions on how to bridge those inefficiencies.

With the confidence of a working relationship dating back more than 30 years, in 2021 Star Refrigeration and Tesco embarked on Reaching Net Zero with Cool Data – an ambitious joint energy and carbon reduction strategy for Tesco’s refrigeration plant.

Tesco first decided to trial Ethos in its Livingston, Hinckley and Doncaster distribution centres for an initial period of one year – January 2022 to December 2022. This enabled the supermarket to assess progress and gauge the suitability of expanding the deployment of Ethos across its wider estate.

To initiate the process, Star consultants established a baseline based on monthly ambient temperatures and energy consumption across each site. The cold and chill storage facilities’ energy consumption were consistently recorded and monitored on a daily basis.

Tesco and Star worked together to implement the Ethos system, with Star handling the installation of the necessary hardware at the first three trial sites to monitor daily operations. The data collected was then compared against a dynamic digital twin of the respective cooling system. 

Using machine learning algorithms and programmatic parameters, Ethos measured the difference between actual and ideal conditions to accurately identify inefficiencies, displaying the insights and recommendations derived from the analysis on an interactive online dashboard along with estimated monetary, energy and CO2 savings.

Tesco had set a target of a 4.5% reduction in energy consumption at each of the three initial sites. Ethos significantly surpassed this target.

Hinckley reported an annual energy saving of 23%. A 7% energy saving was recorded at Doncaster and 14% at Livingston. This equated to a total saving of up to 1.7GWh in energy costs and 351 tonnes of CO2e between January 2022 and December 2022.

Ethos was subsequently implemented as part of this initiative across eight of Tesco’s 11 distribution centres. The capacity of the eight distribution sites – Avonmouth, Dagenham, Daventry, Doncaster, Hinckley, Livingston, Southampton and Widnes – totalled nearly 2.4 million m3.

The results achieved were thanks to Ethos’ ability to pinpoint inefficiencies and propose suitable performance improvements, which typically required little to no further financial investment.

The integration of AI and real-time data analysis with proactive maintenance has revolutionised the way in which refrigeration energy is managed at Tesco’s temperature controlled facilities across the country and shows the significant potential for replication across similar applications and the wider refrigeration sector.

Besides energy and CO2e savings, the project also resulted in substantial cost savings for Tesco as its cost-effectiveness relied on existing infrastructure and strategic upgrades rather than large-scale capital investments, demonstrating the financial viability of sustainable practices.

Ethos also allowed for equipment performance and reliability to be consistently monitored to ensure maximum longevity. The success of the test meant that Tesco was confident in the further deployment of Ethos across eight distribution sites.

Examples of the strategic adjustments made include dynamically changing set points or turning off coolers during entire periods to manage seasonal heating loads and/or ambient temperatures for enhanced energy conservation and reduced carbon emissions as well as monitoring the condenser bleed lines to capture water usage and effluent to claim money back.

One of the most significant recommendations made by the Star team was to raise chill temperatures by 1ºC across Tesco’s estate. Historically, Tesco had maintained specific, lower temperatures in its chill areas but following recommendations from StarCare and the Star Data Analytics (SDA) team, it was determined that a slight increase in temperature would still maintain products within a safe temperature range and drive significant energy-saving benefits.

Ethos estimated that Tesco’s decision to adopt that minor change from October 2022 would lead to an impressive annual reduction in energy consumption of approximately 330,000kWh across the Tesco estate. This bold move challenged conventional practices in the retail sector and helped Tesco achieve substantial energy savings across its distribution network.

Another estate-wide initiative identified by Ethos involved the adjustment of seasonal setpoints for the winter and summer periods. Adjusting for a higher setpoint in winter and lower setpoint in summer ensures that the refrigeration plants are not overworking or underperforming due to seasonal temperature variations. 

“The insights that Ethos and the Star Refrigeration team have delivered have been invaluable and allowed us to make targeted changes at each of the eight distribution sites in a strategic manner, often with no additional spend required,” commented Tesco Group energy manager (Renewables & LZC) Rob Redfern.

The project received the Technological Breakthrough Innovation of the Year award at the recent Cold Chain Federation Climate Summit.

Ethos identified a number of areas for optimisation at the 266,011m3 Avonmouth facility, resulting in a 2% energy reduction of 35,500kWh. 

Ethos identified that the lorry air curtains were not working correctly and an ageing condenser that was not performing appropriately needed replacing. The compressors’ VSDs were reset and calibrated to enhance efficiency and faulty cold store cooler ammonia valve actuators were replaced. Temperature sensors were also calibrated to align with a third party monitoring system.

Several remedial actions were taken as a result of Ethos’ data examination to help the 288,864m3 Dagenham distribution centre reduce energy consumption by 16% (428,700kWh). 

These included a small capital investment to repair the site’s economiser and get it back into service; a complete overhaul of all fans; replacement of valve station actuators and seized valves.

Ethos identified a series of low-cost and quick-to-implement actions to reduce energy consumption by 10% (587,800kWh) at this 413,249m3 frozen facility. 

These included changing condenser set points on 5 July 2023 to allow the head pressure to float lower and reduce the energy used by the compressor. Air was purged from the condenser to reduce condensing pressure and adjustments to the compressor/condenser sequencing were made. In addition, the forced running of daily defrost cycles was reduced.

In Doncaster, Ethos helped the Tesco team to reduce energy usage by 13% (815,400kWh) from January 2022 to September 2023. Remedial actions in this 402,569m3 facility included a reduction in condenser subcooling and an optimisation of the cold store compressor volumetric efficiency through the identification of the most energy efficient Vi position. Condenser set points were also set to a lower value after they were previously raised to help with defrosting.

Tesco’s 205,855m3 Hinkley site achieved a 12% (602,900kWh) reduction in electrical energy consumption after the installation of Ethos. 

Measures undertaken included a project to upgrade and overhaul 50% of the glycol coolers. This included replacing valve actuators, repairing seized valves, replacing fans, and performing a deep clean of each cooler.

Other corrections included enhancements in suction pressure to positively impact the health of the evaporator; performance improvements to the glycol plate evaporators; upgrades and real-time tracking of glycol levels and temperatures of the storage vessel for the warm glycol; boiler adjustment; condenser VSDs were reset and calibrated; temperature sensors were calibrated to align with third party monitoring system sensors.

A 12% (880,600kWh) reduction in energy usage was recorded at Tesco’s 324,176m3 Livingston facility.  

Amongst actions taken from Ethos data to drive that reduction was the correction of a control issue affecting the sequencing of compressor operation. The fixed-speed machines are intended to run in lag, but they were not consistently stopping when the load decreased. 

Other measures included condenser purging, optimisation of VSD compressor controls, adjustment of the freezer cooler to its original design specification and the deployment of door control measures.

Ethos identified a low voltage issue, which was addressed with the site’s energy supplier, and found that HP liquid subcooling was ineffective. Analysis indicated that oil contamination was impeding the heat transfer. Oil was subsequently removed from the vessel to increase subcooling efficiency and improve the availability of liquid refrigerant at the cooler.

The 218,040m3 Southampton distribution centre achieved a 9% (275,500 kWh) energy reduction after a number of possible areas for correction were pinpointed by Ethos. These included an adjustment of condenser set points and an upgrading of economisers with new valve control.

Ethos proposed a host of measures to drastically cut energy usage at Tesco Widnes by 17% within just 9 months. Between January and September 2023 the 280,336m3 Widnes distribution centre cut energy use by 447,100kWh.

The suggestions and action taken included temperature setpoint adjustments for freezer, chill and produce; heating control adjustments; recalibration of control systems and a reconfiguration of the compressors VSDs.

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