Thermal Energy Storage: A Peak Performer

Paul Valenta | July 31, 2013
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Facilities across the globe are using thermal energy storage to air-condition spaces, from one of the tallest buildings in the world (the T&C Tower in Taiwan) to the first U.S. commercial skyscraper to achieve LEED Platinum certification (Bank of America Tower in New York).

Thermal energy storage (TES) systems store energy at night in the form of ice or water; during the day, they use that stored energy to cool the building. Because electricity is much less expensive at night for large buildings, adopters of energy storage can expect to save between 20 and 40 percent on cooling costs. Many high-rise buildings also pursue thermal energy storage as a way to lower environmental impact.

Ice Bank

Demand response participation may allow building owners to generate extra revenue, as was the case in one office high-rise in Philadelphia. The 1500 Walnut Building, a 22-story, 270,000-square-foot office building, needed to replace a failing HVAC system. Installation of an ice-based thermal energy storage system, along with two 300-ton chillers, helped the facility save up to $40,000 in energy costs per month during warmer months. The energy storage also operates as a demand response system, generating an additional $10,000 annually by responding to market-based pricing. Read more: http://highrisefacilities.com/84-year-old-high-rise-saves-200k-per-year-with-thermal-energy-storage-tanks/

A Cool Way to Save
Start with a look at your utility bill to determine whether TES might work for you. Thermal energy storage can help building owners use less energy at peak times when energy costs are at their highest.

Generating extra demand during a few peak hours to air-condition buildings isn’t cheap, so utility companies charge commercial building owners more to use energy during peak daylight hours. In fact, many utilities will actually pay a commercial building owner not use as much energy during those times instead of having to incur the cost of generating extra electricity.

A Cleaner Solution
In addition to saving money, not using energy during peak periods can also lower a building’s environmental impact. Owners who shift their cooling load to evening hours are able to take advantage of more efficient energy. reason? Not every kilowatt is created equal. For every kilowatt-hour that is shifted from on-peak usage to off-peak usage, there is a reduction in the source fuel needed to generate it. It’s more efficient to generate electricity in the cool of the night than in the heat of the day.

Nighttime electricity is also increasing its incorporation of emission-free renewable generation, such as wind. Lowering emissions lowers a building’s carbon footprint.

New Construction vs. Existing Buildings
As with most sustainability technologies, one size doesn’t fit all. So how do you know if thermal energy storage is right for your high-rise facility?

In new construction, energy storage can earn LEED credits for reducing energy costs; the installed cost of a TES system is comparable to a non-storage system.

The energy storage component can be located in a basement or on a roof, and can be inside or outside (or even partially buried), making it a great option to integrate from the onset of building design. A LEED Pilot credit for demand response participation is also available, and may allow building owners to generate extra revenue.

In existing buildings or expansion projects, if you notice increases in required HVAC maintenance, decreases in reliability, and rises in energy consumption and costs, these signs could indicate that it’s time to look for energy-efficient alternatives.

The retirement of existing chillers provides a perfect opportunity to incorporate TES. In expansion projects, the extra capacity provided by an energy storage system could supplement an existing chiller and ensure occupant comfort throughout the added and existing spaces.

Replacing a failing chiller with a new chiller and energy storage allows for a 40- to 50-percent reduction in replacement chiller size. Space may be limited in existing buildings, so options need to be carefully considered.

An ice-based energy storage system that provides about one-third of a building’s total cooling load requires just 0.25 percent of the conditioned space. Finding the extra space may be well worth the ROI provided by reducing energy use during peak periods.

A Smart Investment
Most high-rise buildings can benefit from TES. Whether it’s installed in a new or existing buildings, thermal energy storage systems can reduce cooling costs, source energy, greenhouse gas emissions, and the amount of ancillary equipment needed as part of a commercial building’s HVAC system.

Paul Valenta

Paul Valenta, LEED AP, is the vice president of sales and marketing for CALMAC, based in Fair Lawn, NJ.

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Category: Intelligence, Mechanical & Plumbing

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