By AOS Consuting Engineers
Orange Botswana appointed the professional team of AOS-GBK to build a new data centre and offices at the Innovation Hub Technology Park in Botswana.
The data centre will be used to host existing and future telecoms and IT equipment. The request for proposal (RFP) initially required an office space for 30 employees and a 600m² white space with auxiliary service and functions.
Bidders were to provide two proposals:
- Single storey with provision for an additional floor in the future
- Double storey
Subsequent to submissions of the RFP, the proposal transformed into a single storey building with an office space for 25 employees and a 200m² white space with auxiliary service and functions.
Initially, only 119.98m² of the white space with a meet-me room of 42.14m² would be fitted out with the following:
- Access flooring
- Suspended ceiling
- Mechanical and electrical services to ensure a functional data centre for the telecom and IT equipment. The site has to make provision for a 45m high four-legged lattice tower. The construction thereof did not form part of the scope of work
- A required area of 10m x 10m to be allowed for
The client brief was to design and document the facility with a specified office space and white space with auxiliary services and functions to ensure a functional operation.
The electrical engineering concept design provided an outline of the electrical and electronic service deliverables for the facility. The purpose of this outline was to identify all aspects of the electrical/electronic installation policy as it affects the equipment, organisation and operation of the data centre. The data centre would include white space for 90 racks, as well as a small office component, service and plant areas within the facility.
Various concepts for the provision of uninterruptible power supply, backup power generation were discussed, the merits of these options considered and a recommendation made. The final design options were based on the various design workshops and agreement with Orange.
The project definition, scope, concepts, design and deliverables for the mechanical engineering services and in particular, the HVAC services are as follows:
Project Drivers – Orange Botswana are market leaders in the provision of data and communication services and as such continually strive to improve their level of service delivery. The reliability and security of the data and telecommunications services provided by Orange are key performance indicators and key market differentiators influencing client decisions.
The HVAC system complies with the following principles:
- Providing an ASHRAE CLASS A1 environment for the IT equipment & services
- Energy efficiency
- The lowest possible capital and operational costs
- Providing a reliable and trouble-free installation
Tier Certification of the design and facility was included in the scope of services by Orange. The project achieved the Tier III design certification in March 2020 according to the Uptime Institute and the facility certification commenced late in 2020.
Challenges, opportunities and successes
As the first major infrastructure project in the 20-year history of Orange Botswana, the selection of the right professional team to partner with Orange was a long and drawn out process. The first site inspection for the team was conducted on 1st November 2017 and the appointment of the AOS-GBK was confirmed on 6th June 2018.
Orange Botswana made it clear at the outset of the project the following constraints:
The project was completed within the budget, time and exceeded the quality standards.
Other challenges of this project included an innovative design, the work meeting and out-performing current statutory requirements, sustainability through and maximising energy efficiency.
Preference also needed be given to locally available materials that conform to performance specifications to materials procured outside the borders of Botswana.
Addressing water scarcity and security
The units selected for this project were all air-cooled units and not dependant on a water supply. Additionally, the Mitsubishi PFD units, specifically designed for computer rooms, laboratories and any environment where strict control of humidity and temperature is a must, employ inverter driven compressors and not digital scroll compressors as per the norm.
This enables this Mitsubishi system to actively control the refrigerant in such a way that the refrigerant evaporating temperature can be controlled around saturation to reduce the effects of dehumidification. This means that a minimal (if any) humidification is required which saves additional water and at the same time reduce the maintenance and associated costs to humidifier circuits.
Energy efficiency and addressing net zero
The system uses high efficiency inverter compressors and DC fan motors. The power consumption is monitored internally with on-board electronics including current transformers (CTs) to ensure stable and efficient power consumption.
In addition to this, the system is equipped with a heat interchange circuit (HIC) which provides additional sub-cooling, improving the capacity of refrigerant delivered to the expansion device. The effect of this is witnessed in a reduction on refrigerant volume generated by the compressor saving additional electrical energy. All of these mentioned points makes it easier for a building to achieve a net zero energy use rating.
Resilience to the environment and system
It is notable that the outdoor unit has a guaranteed ambient operating range of between -20°C and +52°C to allow the system to function in harsh conditions. The system is also equipped with an electrical noise filter circuit protecting the electronic circuits in the system.
This means that no additional third-party protecting devices is required. The electrical noise filter circuit protects against over voltage and under voltage conditions and is equipped with an auto phase correction facility. The system is also programmed for a quick auto power recovery to ensure quick start-up operation after a power failure.
The heat exchanger of the outdoor unit is treated for corrosion protection as a standard feature to offer additional resilience.
Passive design inclusion and the design impact
In the Orange Data centre project, various passive design options were investigated to ensure that there is no abnormal heat transfer and also provide reduction in the heat load required for cooling the data centre space.
The various strategies adopted to achieve the passive design are as follows:
- Cavity wall with insulation between the outside perimeter wall and internal wall
- The location and positioning of the data centre away from the perimeter wall that will allow less heat transmission and also for safety purposes
- The use of double glazing energy efficient glass around the perimeter wall
- The use of a Lossnay unit for pre-treating and cooling of the fresh air intake system prior to introducing into the space
- The insulation of the roof slab and in addition the use of light coloured paint over the roof slab for the reduction of the heat island effect
- The above measures added to the reduction of the heat load and also allowed for the energy efficient operations of the system.
Thermal comfort and indoor air quality
The addition of Mitsubishi’s Energy Recovery Ventilators (ERV) to the main design, assists with introducing filtered fresh air through a heat recovery process where no refrigerant is used ensuring clean air while supporting the efficiency of the main system all year round.
Global warming and refrigerant resilience
Global warming or CO₂ emissions should always be considered holistically. This means that the impact to the environment should be considered through the entire life cycle, from the manufacturing to the recycling. These elements were too considered for this project and also played a role in product selection.
In the changing world of technology, innovation becomes the key driver in providing autonomous service. The BMS system for the Orange Botswana project provides for effective monitoring and rapid response to all the services. The BMS graphics allows for ease of support.
The Orange Data Centre building is the first purposed built data centre within the Botswana Innovation Hub precinct in Gaborone, Botswana. Based on this, the building architecture catered for high level maintenance-free finishes that enhances the corporate colour of the end user.
The downblow unit forms an integral part of the HVAC innovative system for the data centre. The operations of the downblow unit is premixed on the effective connection between the indoor and outdoor condensers provided by Mitsubishi. As the first generation VRF system, it comes complete with monitoring and controls.
The project became a landmark project in Botswana due to the adherence to the project time lines and budget as issued by the client. The site handover was conducted by the deputy president of Botswana.
The air-conditioning system is provided with a VRF air-cooled condensers in both plantrooms A & B. These condensers use the ozone-friendly refrigerant system that enhances their operations. Using the VRF technology, these condensers provides reduction in the energy use for the HVAC system which in turn allows for the decarbonisation.
The refrigerant pipes are neatly installed from the outdoor condenser to the indoor units in an easily accessible trench and below the access flooring. All piping is completely labelled to ensure ease of maintenance and accessibility. The piping is also insulated to prevent any accident in future.
In the design of the roof, allowance was made for possible extension to a second floor. However, to prevent the heat island effect and ensure the reduction in AC heat load, the provision was made for insulation and lightcoloured paint used on the roof. This system provides a passive design for the HVAC system.
The site was planned, designed and constructed in such a way as to provide a redundant electrical and mechanical systems for the data centre facility. This was done to allow distinction between Plant A and B.
Due to the ambient condition in Gaborone and to fulfil the statutory requirements for fresh air, a Mitsubishi Lossnay unit was introduced. This unit precools any fresh air intake and ensure that we derived maximum efficiency in the recirculated system too. With this system, the fresh air was pre-treated.
As the first purpose-built data centre by Orange in Botswana, the project had become a reference point for success within the Orange Group globally. The team had thus established a framework for development.
CESA AON Engineering Excellence Awards
This project was featured in the 2020 CESA AON engineering excellence awards under a new category ‘Engineering Technology and Innovation’, that has been added to the annual event to recognise Mechanical & Electrical (M & E) innovation in projects.
This project was named and commended as the first award recipient.
Should you wish to submit your project for possible award nomination or recognition in this category, you can contact Consulting Engineers South Africa (CESA) for the project criteria or initiator of the category, ASHRAE South Africa Chapter.