Will Utilities Help Fund Thermal Storage?

The 8 million gallon tank providing thermal energy storage for McCormick Place and a nearby Digital Realty Trust data center building (seen in background).

The 8 million gallon tank providing thermal energy storage for McCormick Place and a nearby Digital Realty Trust data center building (seen in background).

A California power authority will buy thermal energy storage systems and distribute them to commercial customers, hoping the move will shift up to 50 megawatts of daily electricity usage to off-peak hours.

Although the project is targeting small to medium-sized customers, the concept  may hold promise for the data center industry, where thermal storage is lightly implemented but offers the potential for significant savings on power bills. Utilities in some states are already offering incentives to data centers that reduce energy use by virtualizing servers or upgrading to more efficient equipment.

Thermal energy storage can reduce costs by allowing companies to run air conditioning systems at night, when power rates are cheaper. During daytime hours, when demand on the grid is higher and electricity is mor expensive, these customers can tap the energy storage system, which serves as a “battery” that substitutes for the air conditioner. Thermal storage systems typically use ice or liquid coolant that can be chilled and then used in heat exchange systems.

The Southern California Public Power Authority (SCPPA), which serves the Los Angeles market, announced an agreement Wednesday with vendor Ice Energy that will place the company’s storage systems at customer sites to create a “distributed energy storage project.” Ice Energy’s rooftop units integrate with air conditioners from leading HVAC vendors, including Carrier, Data-Aire, Lennox, Trane and York.

Changing When Power is Consumed
“By using storage to change how – and more importantly when – energy is consumed by air conditioning, we can offset enough peak demand in the region to serve the equivalent of 10,000 homes,” said Bill Carnahan, Executive Director of SCPPA.

“This project includes all of the aspects we look for: managing electrical consumption, improving system efficiency, reducing greenhouse gases, and creating regional jobs for our communities,” added Jeffrey Byron, Commissioner of the California Energy Commission.

Thermal storage also offers an opportunity could also extend to data centers, which are among the largest energy users. ermal storage also offers potential savings for data centers.

Byron was a panelist at the Data Center Energy Efficiency event held in November by the Silicon Valley, where PG&E’s Mark Bramfitt urged a closer look at energy storage. “I think there’s a tremendous opportunity for data centers in thermal storage,” he said. “I think thermal energy storage offers this industry a reliability story.”

Bramfitt has since left PG&E to consult in the field, but helped implement incentvies for data center operators that reduced their power draw from PG&E by using virtualization or Energy-Star-rated servers

Here’s a look at several existing thermal storage implementations in major data centers:

  • At i/o Data Centers’ Phoenix ONE data center, the chillers cool a solution of water and 28 percent glycol. The thermal storage tank contains Cryogel ice balls, 4-inch polyethylene spheres filled with water. The balls freeze when the system is charging at night, and then cool the glycol solution during the day. The glycol solution is then pumped through a heat exchanger, which chills water in a separate loop used in the data center. The first phase of the system provides 12,000 ton hours of thermal storage. A second phase will eventually boost capacity to 24,000 ton hours.
  • Digital Realty Trust’s carrier hotel at 350 East Cermak in Chicago is supported by a thermal storage system featuring an 8.5 million gallon tank of a refrigerated brine-like liquid. The huge tank also supports the Metropolitan Pier and Exposition Authority (MPEA), including the nearby McCormick Place Exposition Center and Hyatt Regency Hotel . The Trigen facility chills the liquid to 32 degrees and pumps it to the nearby buildings, which use it in a heat exchanger system to support their on-site cooling infrastructure. For Digital Realty, that includes a water-and-glycol system and enormous air handlers that deliver chilled air to tenants

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About the Author

Rich Miller is the founder and editor at large of Data Center Knowledge, and has been reporting on the data center sector since 2000. He has tracked the growing impact of high-density computing on the power and cooling of data centers, and the resulting push for improved energy efficiency in these facilities.

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  1. TD

    If only they could figure out a way to capture all of the heat generated by the data centers and re-use it.

  2. Excellent idea and a great application for data centers. We have spoken to a lot of customers about it but it has been hard to justify the cost; having utility incentives would be an excellent step forward. Traditionally the utilities define a "base case" design and compare this definition with the efficient design that (in this case) would include thermal storage. I'm interested to see how they would define the base case for this application as well as how they would determine the incremental cost difference between the base case and the efficient design that incorporated thermal storage.

  3. Phoenix, which is located in one of the hotter places in the country, has a public utility company which created something like this. Their facility called Northwinds, freezes a water type solution during the night and distributes this throughout portions of it's downtown. I believe they can generate up to a few days of thermal storage and have several plants to allow for contingency. Dont know the quantities of storage. It's all hidden from public and you would never know its there. It's a pretty impressive operation they have.

  4. Mohsen Khadem

    TES is a great idea and most of them are using chilled water or ice banking. There are some new technology such as Phase Change Material (PCM) which can be used in different melting point and not just ice at 32F. The benefit of new PCM is that they are compact it means you don't need a huge thank and second you can save a lot of energy by just consuming the free cooling at night. Check it out at GE ecoMagination challenges site for excellent idea: http://challenge.ecomagination.com/ct/ct_a_view_idea.bix?c=12EB3117-EA0C-41EB-B657-5A60BD78BD2A&idea_id=D894033F-C388-4DB0-890A-5D44DF83FF7A

  5. Mohsen Khadem

    TD, The best solution for Heat recovery is using the Phase Change Material (PCM) with melting point one degree below the temperature of produced heat in the server room and use it for domestic water heating or use it for pre-heating of your water if it is not hot enough. You save a lot of money by reducing the delta T.