Extra Edition / Technical

Thermal Energy Storage: Looking Back 15 Years

October 28, 2005
/ Print / Reprints /
ShareMore
/ Text Size+
801 Tower during construction.
In 1990, construction began on a 24-story, 430,000-square-foot office building known as the 801 Tower in downtown Los Angeles. As means of shifting peak loads and qualifying for incentives and off-peak rates offered by the Los Angeles Department of Water and Power (LADWP), the building was designed to include 8,300 ton hours of thermal energy storage (TES). The system is actually capable of approximately 11,000 ton hours of capacity, which in hindsight, was a stroke of engineering prudence that has paid off with ever-changing electricity prices and energy markets.

Flack and Kurtz of San Francisco, a design engineering firm that provides mechanical, electrical, plumbing, and other services, and the Los Angeles Department of Water and Power (LADWP) may not have anticipated all the changes in energy markets during the past decade. Looking back today, however, this system has proven to be a prime example of engineering foresight. Flack and Kurtz, the building owner, and electric utility recognized the need for flexibility to deal with the uncertainties in electrical supplies that have been exacerbated by efforts toward deregulation and by rising fuel costs. Leadership shown by LADWP with incentives and off-peak rates was part of an overall business plan that has shielded customers in that service territory from many of the problems faced today by ratepayers elsewhere in the state and the rest of the country. Concern about the reliability of energy supplies and the need for design foresight have become the norm in California and the nation.

After incentive payments from LADWP, the system cost approximately $640,000 more than a non-storage air conditioning system. With the reported capability to shift approximately 2,000 kW of electrical demand to off-peak periods, the additional costs can be translated to approximately $320 per kW of peak electrical demand reduction. The net installed cost was approximately $58 per ton hour of actual thermal storage capacity. The cost per shifted kW was a bargain compared to the cost of new generation capacity. Today, that same bargain is even more compelling as costs and environmental impacts associated with new power plants have become more painful and politicized.

Inside the storage tank before filling with Ice Balls.
The 801 Tower system includes a 180,000-gallon concrete tank with a polyethylene liner and approximately 750,000 spherical ice containers (Cryogel Ice BallsTM) as well as two Trane 700-ton, three-stage centrifugal chillers. The tank is located three levels below the street and adjacent to the underground parking garage. The roof of the concrete tank is formed by a ramp that connects two garage levels. As in most civic centers, parking is a premium in downtown L.A. This tank configuration and ice storage technology were chosen because the tank could be installed in a manner that would not displace parking spaces in the garage.

Flexibility of the system allows for compliance with changes in utility rate structures. This is apparent when looking back at the original specifications as compared to operational demands now being placed on the system which exceed design intent.

The original design intent was to shift the cooling load for a period of 8 hours. However, today the system is actually shifting load for 10 hours per day. According to Brett Hurff, chief engineer for 801 Tower, "Our current agreement with LADWP requires us to keep the chillers shut off completely from 10 a.m. to 8 p.m. The system has enough capacity to carry the extended hours of operation, even without charging fully every night."

Ice Balls in storage tank below upper tank grating. The clarity of the original heat transfer fluid and lack of corrosion after years of operation are important indicators of the long-term viability of TES applications.
The concrete tank was fitted with a 1/8-inch-thick polyethylene liner to prevent leaks due to normal thermal expansion and contraction. The liner allows for 1.5 inches of rigid insulation between the liner and the tank wall. This unique solution to insulating an underground tank offers double-wall leak security as well as a vapor barrier.

Today, designers and utilities across the country have seen the effects of deregulation in California. They have the benefit of studies by the California Energy Commission which show thermal storage as an energy conservation tool as well as an environmentally friendly and economically attractive alternative to new generation capacity. Today's designers also have the benefit of years of proven success with TES systems and equipment. Designing in flexibility to deal with future uncertainties in electrical supplies and prices is not only prudent HVAC engineering practice, it is also essential energy policy.

Victor J. Ott, P.E, is president of Cryogel, San Diego. Cryogel has supplied more than 20 million Ice Balls for domestic and international projects over the past 15 years. For more information, call 858-457-1837 or visit www.cryogel.com.

Publication date: 10/31/2005

Did you enjoy this article? Click here to subscribe to The NEWS Magazine

You must login or register in order to post a comment.

Multimedia

Videos

Image Galleries

2014 MCAA Annual Convention

Scenes from the 2014 MCAA Annual Convention in Scottsdale, Ariz.

Podcasts

NEWSmakers: Julian Scadden

Training is an ongoing process. Julian will discuss how you can generate maximum return on time and energy invested training by following a three part process. Listen to this podcast to get expert tips on training, tracking and follow up. 

More Podcasts

THE MAGAZINE

ACHRNEWS

NEWS 04-14-14 cover

2014 April 14

Check out the weekly edition of The NEWS today!

Table Of Contents Subscribe

SERVICE CALLS POLL

Which statement on service calls best applies to your business?
View Results Poll Archive

HVACR INDUSTRY STORE

plumbing-hvac.gif
2014 National Plumbing & HVAC Estimator

Every plumbing and HVAC estimator can use the cost estimates in this practical manual!

More Products

Clear Seas Research

 

Clear Seas ResearchWith access to over one million professionals and more than 60 industry-specific publications, Clear Seas Research offers relevant insights from those who know your industry best. Let us customize a market research solution that exceeds your marketing goals.

DON'T MISS A THING

Magazine image
 
Register today for complete access to ACHRNews.com. Get full access to the latest features, Extra Edition, and more.

STAY CONNECTED

facebook icontwitter iconyoutube iconLinkedIn i con