The Grove Mall of Namibia is the country’s retail golden child. Not only is it the country’s first regional mall, but also the largest shopping centre in the country, spanning a massive 52 089 m² of rental area. Located in Kleine Kuppe in Windhoek (which is just 5 km from Eros Airport), the precinct boasts a hotel, medical facility, movie theatre, health and fitness centre, as well as multiple shops and restaurants, all of which consume considerable energy from the national grid.
Sustainable Power Solutions (SPS) was asked to provide a clean energy solution for Atterbury’s mall operations, which included the design, supply, installation, commissioning, and operation of a 2816 kWp grid-tied solar photovoltaic (PV) plant on the 18 000 m² roof.
Construction began late in April 2018 and was divided into four phases due to the sheer expanse of the mall. Each of the ten roofs of the mall were used for the installation of the solar PV arrays, with four feed-in points into the mall’s low-voltage distribution network. From project mobilisation and procurement, to the logistics and delivery of materials and equipment to site, the complete mechanical construction and electrical works, right up until the final commissioning and handover, the project took a just five months to complete.
As per national regulations, and a key component to a successful project sign off, a generation licence was required from the Electricity Control Board of Namibia, and approval was required from the City of Windhoek. The company submitted these applications and ensured that the required approvals were issued before construction commenced on site.
Contractors were sourced locally, ensuring that Namibian solar PV technicians benefitted from the job opportunities created by the project.
Throughout the operation, the staff compliment on site consisted of a small and efficient team of technicians and a dedicated site manager. Since the mall is already operating, it was crucial to maintain a high priority for the health and safety of not only the staff on site, but also the shoppers and retail staff who were present throughout the construction phase.
Due to the installation taking place over multiple roofs, hoisting the modules required that these be off-loaded and lifted as close to the relevant work areas as possible, thus reducing the risk of damage to the modules during transit, as well as the potential safety risks to shoppers. Furthermore, the hoisting team was required to work according to when foot traffic was at its lowest, which meant that much of the hoisting occurred in the early mornings and late evenings.
A large portion of the solar plant components and equipment were sourced from Namibian business entities, and where these could not be sourced locally, they were imported with careful consideration for short lead times and minimal cost implications to the client.
Precautions were taken with the solar module transport and handling to prevent impact and unnecessary vibrations which can result in the propagation of micro-cracks in a PV cell. These micro-cracks are not necessarily visible on the surface of the module but will be revealed under electro-luminescence testing. PV modules with micro-cracks suffer from a lower stability of the power output under ageing, as the cracked cell areas become electrically disconnected from the active cell area.
The exceptionally large rooftop PV array required a total of 8600 poly-crystalline solar modules, with nominal power outputs of between 325 and 330 Wp, from Canadian Solar. After approval from the roof sheet manufacturer, the solar modules were mounted in the plane of the roof, which has an angle of tilt of 3°, using non-penetrating roof clamps. The roof clamps were fastened to the ribs of the concealed-fix roof sheeting. Aluminium rails were fixed to the roof clamps, onto which the PV modules were mounted. The weight distribution of the PV array is approximately 15 kg/m2.
It was confirmed by a structural engineer that the existing roof structure could accommodate the additional load of the PV array. The distribution of the solar modules is such that the effect of shading is minimised, and there is walking space between the arrays, to ensure ease of access during cleaning and maintenance activities.
A total of 43 SMA STP60 string inverters where used, each with an output capacity of 60 kW AC. As the PV arrays have multiple orientations, the PV strings were allocated to the inverters according to their orientation, for optimal maximum power point tracking.
The inverters’ AC outputs were combined into AC cabinets, located alongside the inverters, for each of the four phases. The AC cabinets enable disconnection of individual inverters for maintenance purposes and include Type II surge protection.
A comprehensive operation and maintenance (O&M) plan ensures that the solar plant’s performance and availability is maintained. The inverters continuously upload plant production data, as well as status and error messages to the sophisticated monitoring platform via GSM.
The platform can be accessed by the operator and the client. A weather station was also installed, which measures horizontal irradiance, ambient temperature, and module temperature. This weather data is also uploaded to the monitoring platform to automatically assess the plant performance.
The first-year energy generation is simulated to approximately 4,9 MWh, which equates to an approximately 14 000 kWh daily. The simulation tool utilised for the modelling is PVSyst photovoltaic software. PVSyst software considers losses due to temperature, wiring losses, soiling losses, module efficiency, inverter efficiency, grid and technical availability, and the effect of shading on module and string performance.
With the exceptionally strong irradiance in Windhoek, the installed solar plant should generate considerably more energy than in any other city on the planet, resulting in substantial monetary savings.
The Grove Mall of Namibia is an exemplary case to the commercial property industry, demonstrating that with specialised design and engineering, businesses can take advantage of the financial rewards of solar energy, all the while reducing their carbon footprint.
Contact Lindy Taylor, SPS, Tel 021 851-6308, firstname.lastname@example.org
Source: EE plublishers