Paving the way for a more sustainable city

The City of Cape Town has become the first municipality in South Africa to own a floating power plant.

In its efforts to pave the way towards a more sustainable city, the City of Cape Town has installed a floating solar photovoltaic (PV) system at the Kraaifontein Wastewater Treatment Works.

The City hopes the project will help to determine evaporation savings and energy generation performance of floating solar farms. With the project, the City aims to achieve total renewable energy generation of 300 MW through both City-owned and private power generation.

The floating solar farm is part of a research study involving private company Floating Solar, the Water Research Commission and the University of Cape Town. Data will be collected from sensors over a 12-month period to potentially inform the design of larger utilityscale floating solar PV projects over the next few years through competitive bid processes.

The farm includes a floating solar panel array as well as a ground-mounted solar panel system to determine evaporation savings and relative energy generation performance of floating solar PV technology.

The systems

The floating system consists of:

• a 3.51 kWp floating solar PV system: nine 390 W peak (Wp) PV panels mounted on a floating solar island, with panels installed at a 12-degree tilt

• two identical tanks (20 m in diameter) including a water supply system: one reservoir is covered by a floating solar PV system and the other is uncovered as a control

• one reservoir is covered using the Hydrelio Air technology with a four-per-row configuration

• water levels in each reservoir are monitored with a float switch – when the water level drops below a predetermined point, a pump will be turned on and water fed back into the reservoir

• a three-phase inverter.

The ground-mounted system consists of:

• two land-based solar PV systems each with an installed capacity of 3.51 kWp: comprising nine 390 Wp solar PV panels at the same tilt as the floating solar PV system (12 degrees) and nine 390 Wp solar PV panels installed at the optimal South African tilt of 32 degrees

• all instrumentation and equipment required for the experiment (ambient temperature and humidity sensor, pluviometry, solar irradiance sensor, data logger, wind speed and direction sensor)

• instruments installed on the solar PV panels (energy generation monitoring system and temperature sensor).

Future-fit city

Phindile Maxiti, MMC: Energy and Climate Change, City of Cape Town, says the City has a target to achieve 300 MW of renewable energy generation by 2030, with 50 MW of this comprising City-owned solar PV plants.

“The City has been fighting to move away from the sole reliance on Eskom and to diversify the energy mix for cleaner and more affordable and secure power for all,” she says.

“In addition, given that vacant land in the city is very expensive and rooftop solar PV systems are relatively small, Cape Town aims to explore floating solar PV systems for larger-scale solar PV installations, as part of its pioneering work to diversify the energy mix, to lead by example and to take climate action leadership.”

The project will not only look at the amount of energy that can be generated by floating panels, but will also investigate how much can be generated compared with the ground mounted panels. The other important pillar of the research will be to determine what impact the floats have on water evaporation.

Floating Solar

According to Floating Solar spokesperson Peter Varndell, floating solar has rapidly become the third pillar of the solar PV industry globally.

“In following this trend, we have identified significant potential within South Africa for this promising technology, which has the dual benefit of producing power while reducing evaporation and preserving land for other commercial use,” he states.

“From the outset, we have identified more than 60 high-potential projects – with a combined capacity of more than 450 MW – which will be well suited to benefit from floating solar development.”

Varndell adds that South Africa’s approximately 1 000 water treatment works are a key target market. These are well suited for floating solar due to the significant demand for on-site power requiring a sustainable energy source, limited available land and water evaporation savings, as well as providing the opportunity to export additional power to the grid.

“We are extremely pleased that Cape Town is enabling this pilot project to investigate this potential,” he concludes.