Ice Thermal Storage
Thermal Storage Systems are due to take on a new prominence in the field of HVAC systems for a number of important reasons.
When applied to typical cooling situations, a portion of the cooling load, typically around 40%, is shifted to the ice storage. The daytime building cooling load is then satisfied by a combination of the liquid chilling equipment and the ice store. The ice store is then replenished overnight utilising off peak electricity.
This gives rise to a number of important benefits: –
- The installed refrigeration capacity is reduced and hence the amount of actual refrigerant *
- The size of the condensers are similarly reduced requiring less roof space
- The size of the incoming power mains is reduced also in accordance with the reduced installed refrigeration capacity
- Overall running costs will be reduced where lower night time power rates are available
- Cooling will be available in the event of chiller malfunction or maintenance
- Use of night time power generation reduces carbon emissions in the order of 10%
- Thermal Storage compliments the increasing use of renewable generating methods such as wind and wave power.
- Additonal LEED points awarded
In summary, the application of Ice Thermal Storage not only provides the opportunity to contribute to lower CO2 emissions and lower running costs for many HVAC Systems, but also provides a high degree of system resilience.
Various operating strategies can be implemented depending upon the requirements of the building and the electrical power source. Where direct on site generation is a feature, this can lead to a zero carbon cooling installation.
Ice thermal storage has been now also been successfully applied to data centres to provide resilience in the event of chiller failure or maintenance.
* HFCs which have been widely used to replace CFCs and HCFCs are assessed by the UN’s recent report HFCs: A Critical Link in Protecting Climate and the Ozone Layer, produced by the UN Environment Programme (Unep). The report suggests that the global warming potential of HFCs in 2050 could be comparable with current emissions from the global transport sector.
The United Nations has urged that HFCs, which are increasing in the atmosphere at a rate of 8% per year, could cancel the climate benefits won by the phase-out of CFCs and other ozone-depleting substances.
Design & Operation
The Calmac tanks are of a cylindrical design to ensure that the tank receives equal pressure on all surfaces thereby ensuring the integrity of the tank. They are highly insulated to minimise standby losses and maximise efficiency. They can also be close coupled to form multiple modules.
The Calmac ice storage tanks operate on an internal melt principle with close coupled counterflow tubing ensuring that ice build temperatures and hence chiller operation is also maximised for efficiency.
Ice Storage systems can be either partial or full storage systems depending on the application. The chiller/Ice tank configuration can be either chiller lead or ice lead depending upon the required strategy. LTi are able to offer a full design analysis utilising the bespoke Calmac “ICEPICK” software.
LTi also offer a fully comprehensive CPD covering the technical aspects of ice storage systems.
Ice storage systems have been successfully installed in a variety of applications, including:
- Office Buildings
- Retail Stores
- Data Centres
- Educational Establishments