Challenge

Ranked in the top 2% of universities globally, UCT houses a multicultural community of around 5,000 academic, professional, administrative and service staff, as well as some 29,000 students who come from over 100 countries.

The project is a response to South Africa’s ongoing ‘load shedding’ which is being experienced across the country. National utility, Eskom has implemented daily rounds of power cuts to protect a constrained grid, so the solar PV solution provides a viable alternative to UCT to ensure operational stability as well as financial efficiencies.

Solution

Buildings selected for the first phase of installation comprise the famed Baxter Theatre, UCT’s Graduate School of Business, the Molecular and Cell Biology building, and UCT’s Meulenhof administration facility. Their combined PV outputs will equate to around 500kWp, and the PV panels will be Tier 1 – the highest industry standard globally.

Baxter Theatre, the largest of the four buildings, will be installed with a 151kWp system. This will also be the first installation to be fully commissioned before successively moving on to the other three buildings in phase one, with the overall project scheduled for completion by the end of 2023.

The innovative solar PV design solution, designed and project managed by SMEC, will serve as a complementary power source for the campus’ existing standby diesel generator (genset) backup systems. What makes this solar project unique is that it is a grid-tied system in which battery storage is intentionally not part of the design. When load shedding occurs, the solar PV system will automatically synchronise with the gensets and run in parallel, thereby contributing towards lower diesel consumption costs. The SMEC team is using an ideal DC (power of the modules) to AC (power of the inverter) ratio of 1.2, which provides an excellent yield. For the Baxter Theatre, for example, the inverter will be 125kW to cater for the 151kWp solar PV output.

Bespoke design tailored for each building

Following an in-depth analysis of UCT’s peak and off-peak demand, the SMEC team carried out a detailed structural inspection on each of the phase one building roofs, taking into consideration individual weight-bearing calculations; existing HVAC installations, water tanks, and transformer installations; and walking space for routine maintenance.

• The Molecular and Cell Biology buildings both have a flat concrete roof enabling them to support larger 660W panels. The panels are fixed to a ballast mounting system to counter high wind conditions, with the roof also being able to withstand the weight of the mounting structure.
• The Meulenhof building will have a flush mount installation since the tiled roof has a 30^o tilt, while the Graduate School of Business will feature a standard fixed-tilt mounting system supporting 660W panels.
• The Baxter Theatre will have a flush mount installation consisting of 420W panels due to the roof’s original tilt, orientation configuration and the building’s heritage grading. The panels are smaller as the roof is corrugated sheet and its structural integrity must be considered.

The benchmark for rooftop solar PV in South Africa is to position the panels in a north-facing orientation and to set them at a 0 – 30^o tilt. However, the greater the tilt, the greater the weight and wind impacts. For the concrete roof system and the Graduate School of Business, the SMEC team managed to reduce the tilt to 10^o to achieve the best result given the wind factor.

Impact

The solar system will be connected to the City of Cape Town’s grid following its voltage frequency at the point of connection. When a power outage occurs, and the city’s grid is shut off, UCT’s generators will kick in as normal and the solar system will automatically follow the frequency of the generators via a genset controller.

From a monitoring perspective, all solar PV installations with an output greater than 100kWp require a SCADA system in terms of the City of Cape Town’s regulations. However, for systems lower than 100kWp, performance can still be monitored in real-time via the Original Equipment Manufacturer app that is supplied with the inverters which will aid SMEC in refining UCT’s evolving solar PV footprint. If at a later stage load shedding ever had to be eliminated, SMEC’s design caters for the possibility of selling or wheeling surplus power back to the city.