January 20, 2022

Every Little Helps on the Path to Carbon Neutrality

Written by

Tom Ascough

Reversing cameras, left, right and centre mirrors … a glance over your shoulder can still be what makes that all essential difference. So too with building energy performance. It is probably best to just assume that your building has an energy performance blind spot. The next steps are to find it and then fix it.

This was our approach to Tesco’s National Distribution Centre when Skyline Electrical introduced Symphony Energy to the onsite building services team. This ambient and dry goods warehouse is Ireland’s largest building by volume, extending over 0.5km in length and once the third largest building in Europe. 

It was no surprise to find that operation of the building’s heating and ventilation system was already diligently tuned, given its construction took place in 2007. The building was being heated by just one of its two high-pressure direct gas fired induction Air Handling Units (AHU) – already saving 50% in fan power. The system was also set to minimum fresh air, thereby minimising the air heating load. It appeared that both gas heating and ventilation power consumption was already operating at best practice. Furthermore, the systems had few variables to work with, leaving fewer avenues to explore. The only hope was to find something more – but where?

Most clients have already cleared the low hanging fruit before they find Symphony. We almost invariably need to take a first principles engineering sweep through of the building before getting a blip on our radar for energy savings potential. It has never been a one-size-fits-all. Each building has required its own bespoke solution. 

For Tesco, we anticipated our first radar blip to be the deployment of IoT derived predictive weather control optimisation of the heating and ventilation system. A small, targeted shift within the space temperature, CO and CO2 dead-bands would allow the build-up of substantial energy reserve within the warehouse during the most favourable outdoor weather conditions in a 24-hour period, to be followed by its discharge during the least favourable conditions. This thermal flywheel effect means that only the warmest of the cold outdoor air is heated up to maintain adequate indoor environmental conditions.

The two induction AHUs were each controlled by their representative space temperature and CO2 sensors. It was not clear how evenly balanced the temperature distribution was throughout the space. Symphony installed a matrix of Modbus temperature sensors spanning low and high levels at three cross section locations. These were located at the centre and close to each end of the 77,000m2 building. It revealed only modest variations in space conditions. Nevertheless, this investment in data was then deployed to allow the induction AHUs to sometimes operate for the sole purpose of temperature destratification without the need to fire up the gas burners. It also identified opportunities for optimal AHU selection to better balance the space environmental conditions, and in so doing, minimise the amount of gas consumption and overall air handling operation.

Prior to deploying any new control algorithms, it was necessary to understand the existing system in place. A process of reverse engineering in combination with Symphony Cloud Analytics allowed the control sequences to be mapped. This helped identify what was working well and where improvements could be made. The best of both was then merged. Symphony determined and deployed a process of control that facilitated more efficient operation of the direct gas fired burners. By fine tuning in real-time, it mapped this process into sweet-point operation of the AHUs so they could effectively defeat the buoyancy of the heated air and get it from high level to ground level while minimising the operating time for the Units – all while maintaining even and steady space environmental conditions.

These and other refined methods of system control needed to be carried out in a live environment without impacting the 24/7 operation of the National Distribution Centre. While this was successfully achieved, the smart nature of the energy savings solution can now be leveraged for predictive maintenance alerts and future machine learning. .

Overall, the energy savings results far exceeded the expectations. What appeared energy-wise to be an optimum facility is now operating on further energy reduction  of over 60%. Tesco will now consider the implications of this work to accelerate further future ambitions to use a de-fossilised heat pump solution to strengthen its carbon emission reductions whilst also realising significant space savings, future maintenance, and lifecycle renewal costs at the same time. The likelihood is that this would be based on the design capacity of the induction AHUs in conjunction with energy consumption from previous years. 

Conclusion:

This Symphony data driven solution has provided a very important component for Tesco to achieve a highly cost and energy efficient path towards net zero carbon by 2050 for its National Distribution Centre. 


Outcome:

Using 2019 consumption data as baseline figure, since this real time technology was deployed in October 2020, Tesco Ireland has realised a saving of 63% on Ventilation Electricity, 64% on Gas; cumulating in a total carbon emissions reduction of 873,029kgs up to March 2021. 


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