As South Africa continues on its journey to a greener economy, energy experts who gathered at this year’s Windaba conference, in Cape Town, predict that the country’s future energy mix is likely to include dispatchable power, in the form of hybrid systems.

This follows the Department of Mineral Resources and Energy’s launch of its technology agnostic Risk Mitigation Independent Power Producer Procurement Programme (RMIPPPP) last year, resulting in the renewable energy sector stepping in to develop hybrid energy systems, characterised by a mix of wind, solar photovoltaic (PV), battery energy storage systems and dispatchable generation.

“Reliable, affordable and dispatchable – simply put, hybrid renewable energy systems, have the potential to provide efficiency in a decarbonised energy mix,” said industry organisation South Africa Wind Energy Association (SAWEA) chairperson Mercia Grimbeek.

The ideal hybrid site comprises several factors such as wind and solar resources and their complementarity, suitable topography, grid proximity and capacity, accessibility, as well as limited environmental and permitting constraints.

Some developers, however, report over 30 criteria when undertaking a site selection, but agreed that the aforementioned remained the key drivers, SAWEA noted.

It said that, in the same way the development of new wind power projects was being hampered by limited grid capacity, so were hybrid project sites, especially in the Northern Cape.

Power utility Eskom last month indicated that this area, which was the renewable energy hub of South Africa, for both its wind and solar PV facilities, had exhausted its grid capacity.

Meanwhile, looking specifically at the role wind power plays in hybrid facilities, as a technology, it was very compatible with solar PV, SAWEA said.

This is owing to solar’s peak day-time generation and wind’s peak being predominantly later in the day or at night.

Research and historical data demonstrate that these two renewable sources of energy were naturally complementary and key to delivering cost effective hybrid energy systems, SAWEA informed.

The vast and varied terrain and renewable power sources presented opportunities to develop new renewable energy project hubs, it mentioned. It cited the Eastern Cape and Western Cape, which have sites where sufficient wind and solar PV resources overlap, as suitable hybrid energy locations.

It added that hybrid facilities could also operate as virtual facilities using the best wind resource and best solar resource locations, although not co-located, to deliver a solution through wheeling through the Eskom network.

Moreover, wind combined with solar PV saves on grid connection and development costs, SAWEA said.

With regard to land use – to meet South Africa’s present yearly electricity demand of about 250 TWh of renewable energy, only 0.3% of South Africa’s surface area would be required and dedicated to wind farms and 0.15% to the deployment of solar PV plants, it pointed out.

However, as solar PV plants can be built on wind farms, in between wind turbines, these two figures are not additive.

SAWEA further noted that the RMIPPPP power purchase agreements (PPAs) differed fundamentally from those of the Renewable Energy Independent Power Producer Procurement Programme, as they required projects to be dispatchable on demand by Eskom between 05:00 and 21:30 every day.

This means that energy generated outside of this time period cannot be bought unless it is stored in a battery to sell during these core hours. The plants also need to be on standby to deliver energy at a moment’s notice.

"The RMIPPPP was launched to respond to a specific need of the current South African power mix, that of dispatchable power, where typically peaker plants such as gas-powered plants are used.

“Dispatchable power is there to address the sporadic need for peak energy that may occur either in the case of a large breakdown in the pool of power plants feeding into the grid or in the case of peak demand in the grid when reserve capacity is low. To fulfil such a need, a dispatchable facility needs to show reliable power output at any time during agreed dispatch windows.

“As renewable energy is variable in nature, it becomes key to combine diverse energy sources and technologies and use their complementarities to form a hybrid facility," said G7 Renewable Energies MD Kilian Hagemann.

SAWEA noted that one notable project coming out of the RMIPPPP was the 128 MW Oya Energy hybrid facility, which is a co-located set-up incorporating wind turbines, solar PV arrays, batteries and a hybrid controller to provide dispatchable power to the grid as and when needed.