Eradication of Energy Storage Tanks Reduces Operation & Maintenance costs & Saves Energy

City Centre Mall, Nashik is a commercial mall facility located in the center of Nashik city. This mall facility is owned, managed & operated by the Sarda Group one of the leading business groups from Nashik. This five stories mall spread across 8 lakhs sq.ft of the area has many well-known brand stores, cinema & banquet halls, a gaming zone, and a food court which is a place of attraction for Nashik people. To accomplish the air conditioning requirements of all these areas it was designed & installed with a chiller plant of 1300 TR capacity having a primary constant secondary variable pumping system and thermal energy storage. The facility had several operational challenges such as complaints of hot and cold pockets, high energy consumption, etc.

During the chiller plant audit it was observed that the plant was operating at a very poor efficiency and had many design issues. Chillers were not maintained properly hence; performing on poor efficiency of The primary pump head was not sufficient resulting in negative pressure in the chilled water line. The capacity of condenser pumps was not sufficient to suffice the requirement. Due to insufficient suction-static condenser pump was experiencing negative static pressure. Also, the condenser inlet was undersized resulting in high-velocity pressure and improper distribution of water flow among heat exchangers. The AHUs were designed & installed with a 3-way control valve and secondary pumps were variable confusing the system to perform, uneven flow distribution no control over specific area temperature, and loss of pumping power. The most awful observation while analysing the logged data was the increase in power consumption due to thermal energy storage tanks (STL). The system which was designed to save energy was contributing the most to high electricity consumption as the chillers were operated at minus temperatures to store the energy required day time operation. Also, it had a separate pumping system to circulate water through the chillers, PHEs, and tanks resulting in increased operation and maintenance costs.

These discoveries showed an energy saving potential of 38% i.e., 1950 kWhr/day for 10 hours of plant operation, and the solutions proposed were as follows;

1. Chiller Maintenance:
   1. Descaling of chiller evaporator and condenser.
   2. Changing condenser inlet pipe size from 4” dia to 6” dia.
   3. Chilled water balancing and condenser water balancing.
   4. Replacement of cooling tower fills.
2. Eradicate thermal storage tanks, PHE, and pumps that are used for water flow circulation through chillers, PHEs, and tanks.
3. Replacing 3-way control valves of AHUs with 2-way control valves. Water balancing of AHUs.
4. Fine tuning of the system by using existing field sensors and control systems to improve part load efficiency and solve low ΔT syndrome.