Following a successful pilot project Excalibur Energy have completed the modification of six chillers at two data centres.
Data centres offer a unique challenge to energy management; a constant year round heat load means that cooling represents a significant energy cost. The critical nature of the building means that a very conservative approach to design and modification is adopted.
Excalibur Energy has been providing energy efficient solutions for heating and cooling since 1980. When approached to investigate the potential to reduce the energy consumption of chillers at two data centre, their study showed that there was potential to reduce electrical consumption by nearly 40%.
Excalibur proposed the installation of Liquid Pressure Amplification (LPA) along with the chiller manufacturer’s recommendation of replacing the existing condenser fans with more efficient EC fans.
Data centre technical staff had to be persuaded that modification of their chillers would not affect the resilience of their building. A presentation demonstrated the robust design and that no single point of failure would be introduced as a result of the modifications.
Further confidence was gained by undertaking condition monitoring of each refrigeration circuit using the Climacheck analyser to ensure the chillers were in good working order prior to any works commencing.
Improved refrigeration efficiency is achieved by reducing compressor discharge pressure; this is commonly referred to as “floating head pressure”. Reducing discharge pressure affects efficiency in two ways; absorbed power is reduced while cooling capacity is increased.
LPA allows the minimum discharge pressure to be reduced well below what would normally be achievable, with improvements in efficiency of 25-35%.
If these operating parameters were maintained without the installation of LPA, a condition commonly referred to as “over condensing” would be experienced. This is where discharge pressure has been reduced to a level that liquid refrigerant starts to evaporate before it reaches the expansion valve, reducing capacity, efficiency and ultimately reliability.
LPA is located in the drain from the condenser and pumps liquid refrigerant to the expansion valve maintaining a flow of good quality liquid refrigerant at the expansion valve during low head pressure operation to overcome this problem.
Generally head pressure control is achieved by cycling condenser fans on and off, this is not accurate enough for floating head pressure operation. Inverter or EC fan control allows all condenser fans to be operated and their speed modulated to provide precise control of pressure. The correct control allows discharge pressure to be continually optimised against ambient temperature and cooling demand.
Installation of LPA requires the recovery of refrigerant and the fabrication of a manifold on the discharge side of the condenser. Bypass pipework ensures that in the event of a pump fault (generally as a result of a loss of refrigerant) the chiller will continue to operate. The fault signal generated will initiate an increase in head pressure to ensure that over condensing does not occur.
The low refrigerant fault is generated when 5-10% of refrigerant has been lost, and so provides an early warning that the chiller should be leak tested.
“Excalibur have installed Liquid Pressure Amplification and Intervers to 2 off 1300 kW data centre process chillers. The cooling system is critical to this business and Excalibur’s professional approach provided the customer with the confidence to undertake the project. Their condition monitoring also raised several maintenance issues, which we were able to resolve during the contract. Initial monitoring is demonstrating a 46% reduction in electrical consumption".
UK NRG Ltd
"I would like to take this opportunity to thank you and all others from within Excalibur involved with the development of this project, from my initial involvement through to today’s handover meeting, all of which has run extremely well, with any issues uncovered being easily resolved by the proactive nature of you and your site team, which are a credit to Excalibur. Hopefully, in the not too distant future I will have the opportunity to call upon Excalibur’s assistance and experience again on another LPA Project, though in between times I would thank you again for your support and guidance."
Norland Managed Services