CH-12-C063 -- Applications of Low Temperature Fluid (LTF) in Thermally Stratified Thermally Stratified Thermal Energy Energy Storage (TES) PDF

Thermally-Stratified Chilled Water (CHW) Thermal Energy Storage (TES) is a commonly used technology in large TES applications for peak load management of cooling or air-conditioning loads. However, CHW TES
requires a large unit storage volume (proportional to the TES capacity and inversely proportional to the CHW supply-to-return temperature differential); also, the minimum operating supply temperature for thermally-stratified CHW TES is approximately 39 °F (4 °C), the temperature at which water exhibits its maximum density. This paper presents the use of an aqueous fluid (water with dissolved chemicals) as an alternative storage
medium in thermally-stratified TES. Such Low Temperature Fluid (LTF) TES, compared to conventional CHW TES, can operate with a larger supply-to-return Delta T (for a smaller unit storage volume) and a colder operating supply temperature.

The LTF TES technology has been employed commercially in a wide range of TES applications since 1994, in systems with individual TES capacities ranging from very small (60 ton-hrs or 210 kW-hrs) to very large (123,000 ton-hrs or 432,500 kW-hrs), and operating with supply temperatures ranging from 30 °F (-1 °C) to 38 °F (3 °C). The paper presents:

• a discussion of the desirable characteristics of a LTF,
• a description of the LTF chemistry,
• thermo-physical properties of the LTF at various combinations of chemical concentration and
  temperature,
• examples of operating installations, including end-user types, ages, capacities, and temperatures,
• a representative example of thermal stratification operating data,
• data related to the long-term chemical stability of the LTF,
• data related to the long-term control, by the LTF, of corrosion and microbiological activity, and
• a discussion of the comparative typical advantages and limitations of LTF TES versus those of the
  traditional technologies of CHW TES and ice TES.