RACA Journal June 2016 - Page 35

Feature Continued from page 31 Common mistakes – tips Here are some tips from De Bod on how to avoid common mistakes when it comes to ice storage systems. a. Engineers must remember to always hydraulically isolate the ice storage system from the chilled water system and to use a heat exchanger for this. b. Simplify the controls but ensure robustness and reliability. Do not make the controls too complex. c. Ensure that sufficient expansion and contraction calculations are done and the necessary equipment is installed, in the correct positions. d. Ensure that a reliable accurate ice level measuring device is selected and installed. e. Ensure the tanks can be easily accessed, and that sufficient room is available to replace an ice storage tank. Never install ice storage tanks in a small, enclosed, tight room in the basement. f. Ensure chillers are correctly selected and installed. g. Ensure the necessary safeties are in place to prevent damages to tanks, chillers or the piping and controls. h. Use the correct glycol percentages. Delivering the ice storage tanks for the Novartis head office project. When is ice storage the right choice? In De Bod’s experience, ice storage systems can be considered for projects: a. Where there is insufficient power to generate the next day’s cooling demand. b. Where night-time temperatures are substantially lower than day time temperature. c. Where the electrical tariff during night time is substantially discounted from day time or peak time tariff. www.hvacronline.co.za d. e. f. Where the peak demand electrical tariff is very high. Where there is waste heat that can be used to make ice through an absorption chiller. Where the NPV calculation is favourable. When it comes to thermal ice storage, it is horses for courses as with any HVAC system – but isn’t it time we invested in a few more sustainable ‘horses’? RACA RACA Journal I June 2016 33