Replacement chillers for Bank of England deliver huge energy savings
Cooling energy requirements at the Bank of England have been reduced by 48% following a £6.5 million 2-year project to replace long-serving chillers and related plant. The savings amount to £150 000 a year and £3 million over the 20-year design life of the chiller plant. CO2 emissions have been reduced by 717 t, representing a 8% reduction in overall emissions. The chiller upgrade and other related building-services improvements have improved the DECC (Display Energy Certificate) by one full band.
The project involved replacing three aging centrifugal chillers and two reciprocating chillers with a combined capacity of 4.2 MW that cool the building and critical infrastructure. The new Carrier variable-speed chillers have an enhanced capacity of 5.8 MW. The energy savings will be achieved despite increased intensity of use.
The chiller replacement was accompanied by the replacement of four rooftop cooling towers for the chillers and two for the standby generators. An 11 kV/3.3 kV electrical sub-station supplying the chillers was also replaced
Motors and drives in the building’s main and secondary air-handling units were also upgraded, and the existing BMS was enhanced to provide better monitoring and analysis capability.
AECOM produced a detailed performance specification for the chiller replacement and related works, which the main contractor Interserve carried forward. The design was based on N+1 redundancy for the critical cooling load, which includes the bank’s data centre.
A key challenge was for the project to be delivered by the building continued to function as normal with full occupancy and no interruption to cooling or vital services.
The new system makes use of existing headers and chilled-water circuits where possible. Other challenges included the logistical challenge presented by the underground plantroom and sub-station. The physical structure of the 1930s building meant that access was severely restricted.
The work involved roof access using cranes, which required road closures. A unique consideration affecting delivers of plant and materials was the unannounced arrival, for security reasons, of deliveries of bullion and cash. This sometimes required items being placed in temporary store offsite until access was restored.