Updating Cool Thermal Energy Storage Techniques
From eSociety, July 2019
Cool thermal storage has changed significantly since 1993. From the application of cool thermal storage to emergency cooling to using new storage approaches, cool thermal storage techniques have continued to develop without an update to the first edition of the ASHRAE Design Guide for Cool Thermal Storage, which was published 26 years ago.
“The landscape in the electric industry has gotten even more complex with deregulation and prevalence of intermittent renewable energy sources of wind and solar, yet ways to avoid adding generation and distribution capacity are as important as ever,” said Jason Glazer, P.E., Member ASHRAE, BEMP.
The updated ASHRAE Design Guide for Cool Thermal Storage includes new sections on mission-critical and emergency cooling, utility tariffs and building energy modeling estimates to help design engineers create energy-efficient and energy-saving thermal storage solutions.
The Guide focuses on ice and chilled-water systems and is a comprehensive, first-level reference that discusses thermal energy storage fundamentals, compares thermal energy storage technologies and describes an applications-focused procedure for designing cool thermal energy storage systems.
The author of the Guide, Glazer, who is chair of the energy cost budget subcommittee for Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, discusses the update and its significance.
1. What is the significance of this topic?
Cool thermal energy storage is a powerful approach to reducing the peak demand of a building on the electric utility grid. The Design Guide for Cool Thermal Storage provides a detailed description of how these systems work and how the economics of using them can be evaluated. Cooling demand contributes to a sizable portion of the summer electricity demand in many areas of the world.
Unlike other building electric uses, cooling incurs a peak demand for only a few days or weeks each year. Electric utilities have recognized the ability of cool thermal energy storage to favorably shape electric loads as part of a portfolio of demand-response options. Some utilities offer incentive programs and special rate structures that encourage cool thermal energy storage usage.
2. Why is it important to explore this topic now?
The landscape in the electric industry has gotten even more complex with deregulation and prevalence of intermittent renewable energy sources of wind and solar, yet ways to avoid adding generation and distribution capacity are as important as ever. Due to this, utilities offer a variety of financial incentives, including demand-response programs to reduce building electrical demand, and cool thermal energy storage is a great approach to take advantage of the incentives. In addition, special applications, such as providing emergency cooling for mission-critical facilities, are growing in importance.
3. Why was this design guide updated now?
The first edition of the Design Guide for Cool Thermal Storage has been an important reference for engineers in learning about cool thermal storage and working on cool thermal storage projects since it was published in 1993. Unfortunately, the value of the Design Guide had decreased with time since it has not been revised in so long. A generation of engineers did not have an up-to-date version of the information and guidance embodied in the Design Guide for Cool Thermal Storage.
Those 26 years since the first edition was published have been ones with a great change in the industry, especially with the application of cool thermal storage to emergency cooling, the use of new storage approaches, the impacts of new standards and guidelines, and greater involvement of electric utilities with thermal storage systems.
4. What lessons, facts and/or guidance can an engineer working in the field take away from this topic?
The Design Guide for Cool Thermal Storage includes a variety of information to help owners and engineers learn about and evaluate cool thermal storage options. The Guide compares different thermal storage technologies, including chilled water and ice storage options, as well as several special applications of cool thermal energy storage technologies.
The Guide also describes the various phases of the design process that involve cool thermal energy storage, including initial steps such as the development of an owner’s project requirements, the design procedure for cool thermal energy storage, construction, verification and testing of storage systems and building operation.
5. How can this research further the industry's knowledge on this topic?
Lots of information was collected from a variety of sources and included in the Guide, which is accessible to anyone considering including cool thermal energy storage in their building design.
6. Were there any surprises or unforeseen challenges for you when preparing this research?
Some of the technology for cool thermal energy storage has changed a lot since the first version of the design guide was published, while other aspects have changed very little. Sorting out what to focus on was probably the biggest challenge.
7. Why were new topics and sections included in this edition, and how can the technical information in those sections help engineers in the field?
The revised guide includes new sections on:
- Mission-critical and emergency cooling applicable to vital, technologically complex situations
- Electric utilities and demand response programs to promote greater energy efficiency
- Building energy modeling estimates to aid in design
- Relevant national and international codes and standards
- Utility tariffs, energy cost analysis and system design
Early in the process, we solicited input from experts in the cool thermal energy storage field including from members of ASHRAE Technical Committee 6.9, Thermal Storage. Their input helped guide the project to focus on the major updates that appear in the second edition of the design guide. These new sections summarize information from many different sources and how they impact the selection, design and operation of cool thermal energy storage.