Case Study 1

When rethinking the strategy reduces energy and increases resilience

mentor Building Management, in conjunction it’s clients, actively identifies initiatives that reduce energy consumption as a fundamental part of its services to reduce carbon generation.

The air conditioning system is one of the largest consumers of electrical energy a building and therefore is a logical place to look for ways of reducing power consumption.

The mentor Building Management team identified an opportunity for improving the operating efficiencies of the cooling system at a customer site after an audit of occupancy patterns and equipment operation. A review of new technologies was undertaken and several potential solutions for reducing energy consumption were identified.

The opportunity

The purpose of the cooling system, as the name implies, is to remove heat from inside the building and discharge it outside the building. Simplified, the process steps involves the transfer of heat from air to water at each floor and from the water back to air at roof level. The final step uses cooling towers to remove the heat from the water, to achieve this the water has to be ‘lifted’ to the roof, some 10 stories from the basement, using extremely large pumps to pass the water over the cooling towers. The pumps are arranged as two sets; one for the east side of the building and one for the west. Each set comprises two pumps giving a total of four.

These pumps ran at a constant speed regardless of the cooling requirement and were oversized for the task. The opportunity to vary speed, based on the cooling demand, existed. The lower the cooling demand, the slower the pump speed required; the slower the pump speed, the less energy consumed.

The solution

By applying variable speed drive technology and pressure control, we were able to precisely match pump speed to cooling demand. By reducing the running times on the main air conditioning plant for each of the floors, we were able to further lower the pump speeds for longer periods. This provided a dramatic saving in electrical consumption.

The customer had business-critical areas of the building that require 24/7 cooling. These areas were serviced by only one of the two pump sets available. mentor were able to add a higher level of resilience by adjusting the pipe work to allow supply of these areas from either pump set.

A single electrical supply fed both pump sets, again we were able to increase resilience by changing to two independent supplies. A supply switching panel was also added, allowing either supply to support both pump sets. This allows the full cooling needs of the building to be met should any single supply fail.

The results

Since the completion of the installation, the client has seen a dramatic and sustained drop in electricity use; so much so that the savings realised with the new configuration paid for the improvements in less than one year.

Projected savings over 12 months are 221 tonnes of CO2 emissions, or put another way, 513 Mwh of electricity per year, which is equal to a financial savings of £36,500 per annum.

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