The Robben Island solar microgrid shows the power of solar PV and batteries
It has been almost a year and a half since the Robben Island Solar Microgrid project was awarded to SOLA Build. After a thorough process of designing, planning and implementing, the project has been launched – and is a demonstration of how solar PV, combined with batteries, can make an excellent combination. This blog post describes just why the solar microgrid is so effective, and how the rest of South Africa can follow suit.
A microgrid on a historic monument
Many people know Robben Island for its reputation as the prison that held several high-profile political prisoners such as Walter Sisulu, Ahmed Kathrada and Nelson Mandela. Over the years, the island has also been a leper colony and a host site of WW2 garrisons. The island, therefore, has a rich political history – one which draws the thousands of tourists to its shores daily.
In addition to the historical significance, Robben island is also a biodiversity hotspot, with several bird species finding refuge and breeding grounds on the rocky shore. The African penguin – an endangered bird found only on the southern coast of Africa – also calls the island home.
Energy to Robben Island has historically been supplied by diesel generators. To fulfil the energy requirements of the island, around 600 000 litres of diesel were consumed on an annual basis – at great cost to the island’s administration, and at great cost to the sensitive environment on the island.
The solar microgrid was commissioned by the National Department of Tourism in order to promote sustainable tourism at key monuments around South Africa, as part of their Tourism Incentive Programme. The microgrid, consisting of a 666.4 kW solar farm, 837 kW powerstore and multiple controllers, will move the island away from its reliance on diesel generators and toward the sustainable resource of the sun.
The World Heritage status of the island made it a very sensitive area to carry out construction, and environmental and political considerations meant that the site for the PV farm was carefully chosen. SOLA staff had to also be sent for training to handle penguins, snakes and wildlife and how to handle archaeological artifacts that might be discovered underground.
What’s so great about a solar microgrid?
A combination of tourism, desalination plant and local community means that Robben Island uses over 2 Million kWh of electricity annually. The solar microgrid consists of several elements that will produce almost 1Million kWh of electricity annually, significantly reducing costs of buying diesel, ferrying it to the island and burning it for electricity generation.
The solar microgrid uses the most abundant resource on the island – the sun – and converts this energy seamlessly into electricity, which can be used for operations. In combination, the battery system stores any excess energy produced by the sun, for use during the night or on cloudy days. If both the battery system and the sun are low, the smart microgrid controllers trigger the diesel generators to start up, ensuring that the island never experiences energy shortages or blackouts.
The combination of solar and batteries, a revolutionary step, is the key aspect of the return on investment for the island. The solar microgrid will ensure that the island reduces its fossil fuel consumption dramatically, by nearly 250 000 litres of diesel per annum. This will result in a reduction the Island’s carbon emissions by 820 tons, as well as a significant monetary saving. The system will last over 20 years.
How a smart solar microgrid works
Usually, solar systems are grid-tied – meaning that they supplement power supply and remain connected to the central electricity grid. Some also produce excess power which feeds back into the grid. A microgrid, in contrast, works independent of a centralised electricity grid, yet retains the functionality of it. This means that it contains multiple controllers that switch power sources as and when necessary, without ever interrupting the power supply.
In the Robben Island Microgrid, there are three key power production aspects. The first of these is a solar farm, consisting of 1960 mono-crystalline modules that produces 666.4 kW of power.
The second is a battery bank, consisting of 2420 lithium-ion battery cells, ready to store 837 kWh worth of electricity and supply 500 kV worth of peak power.
The third aspect is the diesel generators, which supply power to the island when the solar farm is not producing energy (for example at night), and the battery bank is depleted.
Combined, these three power production elements, coupled with a set of smart controllers, supply Robben Island power – all of the time.
Microgrid controls a smart approach to energy management
The microgrid control system is based on a distributed intelligence approach which ensures that the grid behaves smartly for seamless power production. Each of the points of power production have a logic controller that controls the power output at each of these points, whilst reporting back to the other controllers. The system monitors the current load by adding the current production of each of the power sources; each of the controllers then adds a safety factor to the current load and always makes sure it has enough power, immediately available, to supply the load and handle sudden increases in load, such as the operation of the 200 kW desalination plant. The only centralised component in the system is a data-collection system, similar to a small SCADA (Supervisory Control and Data Acquisition), which allows for set points to be altered and measured values to be recorded.
The potential of solar and batteries: a Robben Island case study
Solar PV has long been a more cost-effective energy source than the central grid in South Africa, but it’s the combination of solar with batteries that will make the technology truly disruptive, as it has the potential to make the centralised grid redundant. The Robben Island Microgrid is a great case study to explore the true value of solar PV and battery combinations, because it is already independent of the central grid. During its first two months of operation, the island produced 187 000 kWh clean electricity through solar power, resulting in 53 685 litres of diesel being saved, an equivalent of 495 tons CO2 emissions.
The above graph shows Robben Island’s energy demand (blue line), supported by the generator through the evening. Around 6.30 am, the solar system (green line) starts to produce power, and by 9.30 am, the solar system starts to supply the entire island’s energy demand. By 10am, the solar power starts to surpass the island’s demand, and charges the batteries. Once the batteries are full, the solar power curtails to meet the demand of the island. Once the power starts to go down at 6pm, the batteries are activated and start to discharge, finishing their power around 8.30 pm when the generators start up again.
This graph demonstrates that the solar farm can easily meet – and exceed – the needs of the island during hours of light, even in winter. The rate at which the battery bank charges suggests that an even bigger battery bank could be possible – and the island could rely even less on the diesel generators.
The rapidly decreasing price of battery tech
Based on the above graph, it is clear that an even bigger battery bank on Robben Island would further decrease the already substantially reduced spend on diesel and its accompanied environmental degradation. As such, how can projects start to install solar PV and batteries to meet enough demand to go off grid entirely? The future is closer than we think.
In 2016, the costs of a lithium-ion battery cell had come down 73% from 7 years prior. Even during the building of the project over 12 months, the cost of the tech went down significantly. The graph below, published by Goldman Sachs, demonstrates the cost reduction of batteries over the last next 6 years.
Conclusion: how South Africans can learn from Robben Island’s Example
Robben Island has a difficult history – one of banishment and pain – yet today it serves as a heritage site and a reminder to thousands of the triumph of the human spirit over adversity. In a similar vein, Robben Island’s energy history is one marred by reliance on fossil fuels and environmental degradation. The Robben Island solar microgrid shows an inspiring example of the way in which communities can adopt clean, efficient and more affordable energy – to the benefit of the local community and the surrounding environment.
“It’s been inspiring to work on a project like Robben Island,” said SOLA CEO, Dom Wills. “The island is in many ways a microcosm of South Africa, and we hope that its example will inspire other African communities to follow suit. Adopting clean energy is not only possible – it is now affordable. What Robben Island has taught us is that the future of efficient energy is within our reach.”
Do you know of a community who could benefit from solar microgrid technology? Contact us or use our solar calculator to find out if it is viable. The future of Africa is powered by the sun.
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