Case Study: Free-Cooling Chillers

Equipment: ARAF0644

M25 Disaster Recovery Site

Problem to Solve:

The site is a disaster recovery centre for a financial institution with main offices in London. The site was designed to cater for an 800kW cooling load served by two 443kW air cooled chillers. However, due to the nature of the site, vary rarely did the building operate with such a cooling requirement and the base load was just 80kW. This meant that the existing chillers were operating below their minimum load requirements causing maintenance and reliability issues as well as causing peaks and troughs in the chilled water setpoint as compressors cut in and out for short periods of time.

 

Solution:

Norland Managed Services worked in conjunction with Uniflair to improve the efficiency and resilience of the cooling system. This was a two part project:

 

1. Installation of a 2,500 Litre buffer tank

2. Installation of a 150kW Uniflair packaged free-cooling chiller

 

The new chiller is now the lead chiller to maximise the free-cooling potential and is more suitably sized for the base load. As the existing system has no glycol, the new Uniflair chiller was supplied with an on-board heat exchanger to allow an independent integral free-cooling circuit which is glycol-filled to prevent freezing, whilst the main hydraulic circuit remains pure water with electric trace heating for anti-freeze protection.

Prior to the works, the energy consumption of the existing setup was monitored for a period. Following the installation, the chillers were fitted with data loggers to monitor power usage. Analysis of the results show an average daily saving of 556kWh or 34%, equating to over £22,000 per year and 114 tonnes of CO2.

The next phase of the project is to introduce a chiller sequence control to stop flow through the existing main chillers when they are not required, which will provide further significant energy savings due to reduced pump power.