Oracle’s new ‘green’ HVAC system

Oracle’s new ‘green’ HVAC system


By Bradley Komen of Graeme Page Consulting Engineers
When Oracle moved into its new state-of-the-art offices, it choose to move away from a chilled water system to a VRV that would allow them to optimise efficiency and future maintenance.

Oracle is a global cloud company, positioned as the third largest software company in the world based on revenue, and is the number one provider of business software. Oracle serves 430 000 customers in 175 countries.

Oracle has three offices in South Africa: one in Durban (Regus office), one in Cape Town, and one in Johannesburg. The new three-storey Johannesburg office is located right next door to the old one, inside the Woodmead North Office park along the N1 highway’s Buccleuch interchange. The new offices have been awarded the GreenStar 4-star rating from the Green Building Council of South Africa (GBCSA) for its design.
The project was completed in 10 months, with the first design meeting being held in January 2018. Oracle took beneficial occupation of their new offices on 1 March 2019, and officially started working out of it on 15 April 2019.

The office is a standout feature along the side of the highway, with the eye-catching red archway covering the front entrance of the building. This, coupled with the stark differences between the black and white cladding of the building, make it a sight to behold.

Client brief

Zenprop, the client, approached the team with the intent of designing a building that stands out, that is good looking both inside and out, but most importantly that it would be a green building. This brief dictated that a 4-star GreenStar building would be ideal, and would allow for the building to operate at an optimal efficiency.

System description

With this brief from the client, GPCE were able to propose a Variable Refrigerant Volume (VRV) system that could serve the entire building. The building was split into four major zones where a single VRV system would cool one zone. These major zones were the first and second floors, and then the ground floor meeting rooms and restaurant area, respectively being conditioned by their own separate VRV system. This approach was chosen in order to ensure that if the VRV system on one floor went down, all the others could still function without any issues. Oracle’s previous office building used a chilled water system, however due to constant breakdowns and complicated maintenance, a VRV system was preferable.

The VRV system was also selected due to its heat recovery ability, allowing individual air conditioning units on the same system to operate in both heating and cooling modes simultaneously. This greatly increases occupant comfort as they can more easily set their desired temperature without impacting the entire system. The heat recovery ability of the VRV system is also more energy efficient than those systems without it, which was another pro for the GreenStar requirements.

The VRV heat recovery system is an air-cooled direct expansion system with inverter heat recovery supplied by Daikin, in their VRV IV product line, which uses a three-pipe design in order to use less energy to recover heat.

The VRV outdoor units are located on the roof of the building, with the refrigerant piping running down dedicated shafts to the outdoor unit’s respective floor zone and distribution (BS) boxes, further reticulating to the individual units from there. The outdoor units use hermetically sealed inverter compressors, and R410a refrigerant.

Inside the building, ducted hideaway units were the majority of indoor units used in the offices, with a few exceptions being cassette units in certain offices. Each meeting room, demo room, and cellular office contains its own indoor unit installed in the ceiling void. The ground floor meeting and demo rooms supply conditioned air through linear slot diffusers, running the length of the lay in ceilings in the rooms. The other spaces are supplied via radial swirl diffusers. All of these supply air selections come together to present a professional and sleek office space.

The indoor units were positioned in such a way as to allow for perimeter and internal zoning of the building. This prevents over-cooling in generally cooler areas such as inner office spaces, or under-cooling in generally warmer zones near the windows. This further increases energy efficiency of the installation by allowing some systems to be able to run at a lower capacity and mitigate the losses of over-cooling areas. The ceiling void was used as the return air plenum for the units, as the cellular offices had full height partition walls installed. This prevented mixing from different temperature zones and meant the void return was a valid design option. Return air grilles installed near the units double as access to the units for maintenance, which is in line with Oracle’s desire to have ease of maintenance as a core design principle in their new offices.

The design temperature for the office building was set to 22oC, with a tolerance range of ±1.5oC from the design set temperature. Each cellular office space has its own dedicated individual controller, mounted on the wall at 1 200mm above the raised floors. The controllers allow for set point temperature control, heating and cooling mode selection and fan speed control. The cellular rooms are also controlled by motion sensors in order to decrease the energy usage when offices and meeting rooms are empty.

A building management system (BMS) has also been installed, whereby the entirety of the HVAC system can be controlled, from the supply and extract fans, through to the indoor units. The control of the AC system is made possible by the Daikin iTouch controller, which allows each connected unit to be fully controlled by temperature set points, heating or cooling mode and fan speed. The BMS system has floor plan layouts, with each indoor unit and the space that it serves numbered for easy control.

The fresh air for the building is introduced by a fan located on the roof, with ducting being reticulated down a main fresh air riser shaft and branching off on each floor. The fresh air is filtered through a large filter media bank to ensure that the best quality air is introduced. The ducting then takes the fresh air to either the cellular spaces or open plan areas, supplying fresh air to the indoor units. The fresh air for the building had to meet the Greenstar requirements of 12.5ℓ/s per person, giving a 66% improvement in fresh air over the SANS 10400 regulations. This helps to decrease the CO2 build up in the building, as well as promote a healthier and more productive office environment overall.

Oracle’s new offices have an onsite restaurant with the capacity to serve everyone in the building. This then meant that a large canopy extract system would be required. Capture jet canopies were selected to reduce the required air flow and resultant duct size. There are two canopies in the restaurant, one in the main kitchen and another in a call-order area. Make up air is interlocked to the two canopies and supplies make up air to the restaurant and kitchen areas to prevent a negative pressure situation from occurring.

The offices also use a basement for parking, however there are a few occupiable areas here, such as a gym, change rooms, and a mail office. All these areas, as well as service areas such as Telkom and UPS rooms are conditioned by Direct Expansion (DX) units. The server rooms are cooled by two DX split hideaway units, which are located outside the server rooms and supply air directly through a supply grille. The two units work together using inverter technology to cool the rooms, but if one unit fails the other can pick up the cooling capacity in its entirety.

The GreenStar requirements dictate that the noise levels for the office spaces could not exceed the maximum allowance of 34dB. To assist in this achievement, the fresh air ducting reticulation to each office was designed in such a way as to minimise cross talk between offices through the ducting. This was accomplished by moving the fresh air spigots as far away from each other as possible, and in the instances where it was not possible, sound attenuators were installed to prevent cross talk through the ducting. Additionally, the supply air ducting for the indoor units was internally lined with 25mm sonic liner to further dampen noise generation and propagation through the ducting.

Efficiency matters

The end of the project meant that Oracle’s brand new office building had an efficient and green HVAC system, capable of keeping the occupants comfortable and productive in a controlled environment, no matter the outside conditions. This green design meant that Oracle’s energy consumption has dropped from 360KVA down to 150kVA for the entire building.

Because of the efficient design, Oracle was able to connect the complete HVAC system onto their back-up generator, something which is very uncommon and is a standout feature for their offices.

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