PROJECT 25
Warming up student accommodation
By
Tanya Olckers
Two gas generators get installed in student accommodation in Braamfontein at the forefront of heat harvesting .
Growth Point Student Accommodation Holdings needed a solution to their heating needs . An epic seven week noseto-the-grindstone effort was made by Ingplan Consulting Engineers , SA Heat Pump Engineers , IEE Solutions , Dreycor Plumbing and EnerGas to get the system up , running and working satisfactorily .
This system was completely built from the ground up . Two gas generators will be installed to cater for the building daily energy use . The gas generators simultaneously generate electricity and use the heat from the engine jacket water and exhaust to heat water . The power output can be controlled between 50 and 100 % of nominal rating which will proportionally affect the amount of heat output to be used for hot water heating .
The maximum thermal energy generated by each unit is approximately 240kW . According to the case study provided the generators will run on average only on 56 % and provide approximately 5,700kW heat energy per day . The generator heat source will provide a constant flow of 10.6m ³/ hr ( each ) water at a constant supply temperature of 90 ° C . The system water will circulate to a low pressure domestic hot water tank , which will be controlled at approximately 55 ° C to 65 ° C . The hot water storage tanks are installed to be used as a battery for hot water generation to the building . Domestic cold water will flow through a coil system installed as part of the hot water storage tank , exit at minimum 55 ° C to cater for the hot water demand . Hot water will be circulated continuously to ensure immediate hot water at each supply point .
For summer , it would require approximately 3,840kW / h heat recovery to heat 60kL to water from 18 ° C to 60 ° C per Wilo booster pumps and hot water return pumps . day . For winter , it would require 5,640kW / h heat recovery to heat 60kL water from 10 ° C to 60 ° C per day . It is envisaged that 100 % hot water heating will be catered for by the gas generators .
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30 000 litre heat accumulator .
Energy recovery from gas turbine generators fed on Egoli Gas to generate the 60 000L of hot water storage while generating all the electrical requirements of the building . That is the primary heat source . The secondary source is a gas heater bank , and the final third source if all else fails is a pair of air to water heat pumps . The whole plant room is run from a Program Logic Controller ( PLC ), which is a custom computer . It has colour touch screen interfaces for the whole plant system and all parameters and controls are monitored live via an online portal . So , authorised personnel can log in from anywhere in the world with an internet connection and see what all the statuses are and if they choose , they can send commands and change settings or start and stop certain equipment .
The client , Growthpoint , wanted to maximise energy efficiency from the gas energy source . While using gas to generate the power for the building , they did not want to lose the heat generated from the
February 2025 Volume 30 I Number 12 www . plumbingafrica . co . za