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Why ice-enhanced cooling is a cost-efficient solution

Energy accounts for a third to two-thirds of the operating expense for a typical commercial building, but there are ways to cut this cost significantly, as Richard James explains
Why ice-enhanced cooling is a cost-efficient solution
The financial cost of energy inefficiency is enormous, as are the opportunities for HVAC to offer significant savings. Energy is the largest operating expense for a typical commercial building, 35-65 per cent of which is spent on heating, cooling and refrigeration.

Chris Webber of The Economist Intelligence Unit has estimated £1.6 billion per year to be wasted in the UK alone. Fortunately, a wide array of systems, solutions and services is available to reduce HVAC energy consumption and costs. While some potential solutions are new, a lot of others have been around for a while.

Ice storage is an example of an existing technology that deserves a fresh look. With an evolving global energy situation and the introduction of innovative new technologies, ice-enhanced cooling serves as an energy cost saving alternative to chiller plant systems for many building owners.

Ice storage systems are particularly interesting for buildings with a high daytime-only cooling demand (e.g. office buildings, commercial centres) or peak load cooling demands (e.g. hospitals, dairy facilities).

In an ice-enhanced cooling system, a chiller is paired with an ice storage system to make ice during off-peak energy periods, usually at night. The ice is used for cooling purposes during the day.

The more ice storage capacity is designed into the HVAC system, the more capacity can be taken out of the mechanical chiller. However, there are practical and financial limits. The chiller must be able to make the total required amount of ice in the off-peak electrical hours. Furthermore, chiller and ice storage capacity must be carefully considered. A load profile analysis will ensure an optimal design.

Because they produce ice during off-peak energy periods, ice storage systems can reduce energy costs and make the required energy load more level. Even a building with a relatively constant process load can be a candidate for ice storage based on redundancy and the potential for time-of-day energy cost savings.

The second benefit is the possibility to downsize the chiller. When retrofitting a chiller plant, an existing chiller can be replaced by a lower capacity chiller and an ice storage tank. This generates a dual benefit: lower electrical consumption during on-peak periods and reduced implementation cost.

Some may claim that thermal energy storage systems, such as ice storage, aren't environmentally friendly as they might use about the same amount of power as non-storage systems. However, as shown above, ice does a better job of load levelling the available power supply and infrastructure. This load shift can create source energy savings and reduce emissions.

In addition to reducing energy bills, ice storage can also help the overall building design to raise the Building Research Establishment Environmental Assessment Method (BREEAM) percentage rating.

At the national level, ice storage allows the reduction of peak load demands of power stations as it shifts power consumption during off-peak periods and limits the operation of high carbon footprint power stations operating on coal and gas.

While ice storage has been available for a while, the combination with new technologies is making it an increasingly valuable solution to cut energy costs. For example, recent modelling software can help select the optimal ice storage capacity and the right size chiller.

What is more, the latest ice storage systems currently on the market streamline the process of creating and deploying a cooling system that is ideally suited for reducing operating costs and supporting the smart grid.

Ice storage at work in Dublin
The Convention Centre Dublin (CCD) has been recognised as the first international carbon neutral convention centre. The CCD worked with Trane to incorporate high-efficiency infrastructure systems, including thermal ice storage. The convention centre is committed to long-term sustainability in accordance with the International Organisation for Standardisation 14001 publication and is currently seeking accreditation.

The ice storage thermal unit produces ice at night to provide air conditioning for the building during the day. This shifts electricity demand from more expensive rates to off-peak, saving money and increasing the building’s sustainability, and reducing building cooling costs by an estimated 17 per cent.

Thanks to all their work towards becoming a high performance building, the CCD has been awarded the Energy Efficiency Leader Award from Trane, a leading global provider of indoor comfort systems and solutions and a brand of Ingersoll Rand. The CCD is the first convention centre in the world to receive this award.
// The author is sales manager
of Trane UK
//
18 June 2012

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