London Bank

Bank’s chilling ‘green’ solution accounts for big cost savings

As part of a company-wide project to cut energy costs and increase environment-friendliness, a major bank targeted the gas boilers supplying 666kW of hot water to coils in the three air handling units that ventilate its six-storey central London head office and data centre. The hot water coils in the AHUs provide primary space heating for more than 2,500 staff by tempering incoming fresh air when the ambient temperature falls below 16oC.

Bank’s chilling ‘green’ solution accounts for big cost savings

In the search for alternatives, the bank called in Portsmouth-based DCI Refrigeration, which had previously installed four new chillers to cool the data centre via two separate water circuits.

The solution involved using two groups of six Daikin heat pump chillers to provide primary cooling, reducing the return flow temperature in the existing circuits from 12oC to 9.5oC. The heat pumps then enhance the rejected heat through their refrigerant circuits before transferring it to the AHUs via secondary water circuits.

“To eliminate the gas boilers, some method of heat recovery was the obvious choice. We looked at recovery of heat rejected at the chillers, but this was not an option as it was low-grade heat, and alterations necessary to harness it could have led to warranty issues."

Brady Drain, DCI Operations Director

More economical operation

Daikin Hydrocube

With the Daikin Hydrocube water-cooled heat pump chillers in place (heating capacity 54.8kW), the main chillers can now operate more economically at a part load of 503kW per pair – needing only to reduce the flow temperature from 9.5oC to 6oC – with the associated six Daikin units providing up to 222kW of cooling. Removal of the gas boilers saves about £290 per 14-hour day on gas. CO2 emissions are eliminated. Minimal heat is wasted to atmosphere. Estimated annual running costs are down from £185,000 to £137,550. The 666kW heating requirement met by the Daikin units is free heat.