RACA Journal February 2021 | Page 39

Projects evaporation units that dump the remainder of the generator waste heat to the back of the building .

Weight limits were another challenge . Because the new building used the existing foundation that had a much lower elevation , the weight per m ² allowance was very low - approx 250kg / m ² . When looking at plant placement , this also favoured the VFR system as you need a very small footprint to get high cooling capacity out of the system . Other solutions for this building would have either required additional platforms on the side of the building , screens for acoustics and aesthetics , or additional measures to manage water vapour released into the air based on the available placement areas for the plant type .

ENERGY EFFICIENCY ELEMENTS Renewable energy was a core design element . The building ’ s entire available roof space was covered with a solar PV panel array , this power generation system feeds directly into the building ’ s main grid intended to supply the baseload power requirement for the day time HVAC system . The solar PV serves as a first phase of the solar cooling design that is strategically planned for the developers strategic rollout to their other property portfolios .

The VRF solution is very efficient as it is and also contributes to the power consumption savings of the building . With the installed control system that comes with VRF solution , it further allows the capability to optimise the way the entire system runs such as load control and peak hour cutting , which were implemented for this building . Added to this , if load shedding occurs and the generators are running , the AC system has been set to operate in fan-only mode to ensure continual circulation of air and to minimise the load on the generators ensuring the maintenance of power for any essential services the building needs .

Installing a gas generator also opened up the perfect opportunity to make use of a typical waste by-product . Gas generators in their own right are actually highly inefficient with a large portion of heat rejection taking place . In the production of electricity , almost 70 % of what goes in to a gas generator gets released as waste heat . This offers a process to harness the heat and produce hot water from it . This solution was implemented in the building producing a saving that offered an internal rate of return exceeding 25 % of the project value . The overall gas generator system installation has saved the building up to 20 % of electricity costs compared to the city power supply costs . The benefits of greening in this way have proved phenomenal and when carbon taxes are implemented , there will be a significant further savings for the building . Choosing a gas plant or solar installation is much more feasible now than the regular power supplied by councils ( given the availability of gas in the area ). If more engineers are able to see this through actual data and installations – greening technology will be implemented much faster and in many more developments .

UNIQUE ELEMENTS As a first on the African continent , this already makes this project unique but coupled with the control technologies and co generation

Blackdot Energy

The rooftop plant and solar PV installation .

system installed while meeting the client ’ s requirements is worth noting for this project .

Tri- and co-generation power solutions are very new to the industry and there are also not a lot of companies that specialise in this field that can supply solutions based on the various needs of the client . Blackdot Energy is one of the scarce companies in South Africa who were able to provide a solution for this building .

This project went though a very long feasibility process in terms of the tri-generation system because it is new technology – there are only a handful of installations in the country currently , but catering more to the data centre environment and large university buildings . This system works extremely well when you have a constant cooling load and it was therefore a practical option as the gas generator is continually producing electricity and you then have the waste heat to use as ‘ free ’ cooling and heating . However the tri-generation solution is quite costly in terms of capital expenditure because an absorption chiller would need to be added to the overall system . The owners then decided to go with the co-generation solution , being power supply and using of the heat to create the hot water .

From an architectural point of view the entire building is fitted with double pane glazing and for those interested in what happens below ground , an interesting operating feature of the building is that the client installed car lifts throughout the basement so that they can double stack cars with a valet service , increasing the capacity , which is a feature that you don ’ t see in many projects . RACA

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