Water and ice — saving dollars with cooling thermal energy storage systems

Thermal energy storage (TES) systems are not a new concept in energy-efficient and cost-efficient HVAC designs but have had renewed popularity for building owners, especially in Florida and the Southeastern United States.

A TES system uses cooling or heating equipment, such as chillers or boilers, to operate during non-peak times to store energy in various mediums until it’s used by the building load. This process results in lower demand charges and less strain on the utility provider during peak times. In the case of cooling TES systems, the energy can be stored as chilled water or ice.

With chilled water storage, primary pumps circulate chilled water from the chillers to an insulated, stratified tank. This can be an attractive option to a chilled water plant looking to retrofit to TES, given the minimal modifications required. With ice storage, primary pumps circulate 23 degree Fahrenheit water/glycol mix from the chillers through insulated, compact, sealed TES tanks that contain nonpotable water, therefore freezing the water inside and “making ice.” For both systems, the chillers are de-energized during peak hours, and the primary pumps circulate the water from the TES tank(s) to the building load.

Some of the benefits of owning and operating a TES system include:

  1. Utility-provided rebates. These rebates increase the return on investment (ROI) on a TES system. Rebates are always changing, so consult with your local utility provider before pursuing TES.
  2. Redundancy. Depending on the storage scheme, chillers can provide N+1 redundancy to the storage tanks during peak cooling times.
  3. Versatility. A common misconception is that TES doesn’t offer a decent ROI for buildings with consistent cooling loads, given that a TES needs “building downtime” to charge the tanks. However, there are several options in pumping schemes and chiller staging that can allow tank charging while cooling the building. TES can work for almost any building application.

Commissioning of TES systems is highly recommended and, in most cases, required by the utility provider as part of the rebate process. Hanson is knowledgeable in the design and commissioning of TES systems and can guide building owners and operators on what TES systems are the best fit for their specific applications.

For more information, please contact Bradley Perrott at bperrott@hanson-inc.com.

Posted on July 16, 2016