RACA Journal June 2016 - Page 53

Projects A full life-cycle options-analysis was not carried out as the abovementioned process has produced an acceptable economical solution to the HVAC requirements of the building and user client. Cooling system description The chiller plant comprises 2-off air-cooled chilled water generators (refrigerant R410A), generating either ice water (at approximately -5.0⁰C) to charge the ice tanks during night-time or providing chilled water to the plate heat exchange at 6⁰C. The heat exchanger transfers the cooling to the building airconditioning system at 8.0⁰C. The chillers were selected as follows: a. Sized to charge the ice tanks during night-time during warm season. b. Both chillers are on duty, always running in parallel to get the benefit of optimal coefficient of performance (COP). c. The same chillers can also generate chilled water during daytime to top up any cooling requirements over and above what the ice tanks deliver. According to the proposed control strategy, the HVAC plant is controlled with emphasis on: a. Reduced annual kWe hours. b. Best plant COP. c. Shift load from peak to off peak periods. d. Three operating programme modes (adjustable). One of the air handling units. Heating system description The heating plant comprises a 1-off heat pump (refrigerant R410A), generating hot water to the building air-conditioning heating system. The heating plant was selected as follows: a. Duty only heat pump chiller was selected based on the peak heating load calculated. b. Whenever the cooling chillers are operational, heat can be recovered by the de-superheaters on the chillers, and hot water tanks charged. c. Two hot water tanks are provided to store hot water that is recovered from the cooling chillers. RACA About LEED Novartis scored 60 points, qualifying it for a Gold LEED rating. Leadership in Energy and Environmental Design (LEED) is one of the most popular green building certification programmes used worldwide. Developed by the non-profit US Green Building Council (USGBC), it includes a set of rating systems for the design, construction, operation, and maintenance of green buildings, homes, and neighbourhoods that aims to help building owners and operators be environmentally responsible and use resources efficiently. About the author Pieter de Bod (Pr. Eng.) is an accredited Green Star Professional and works as the technical director of WSP Group Africa, and is a member of the American Society of Heating, Refrigeration and Airconditioning Engineers (ASHRAE). List of professionals continued on page 52 www.hvacronline.co.za RACA Journal I June 2016 51