Mention Robben Island and it immediately conjures up images of Nelson Mandela’s – and other high-profile political prisoners – 18-year incarceration in a tiny cell on the island’s maximum security prison.
Situated 9 km off the coast of Cape Town in South Africa, Robben Island is now a World Heritage Site attracting nearly 2,000 tourists every day.
There are about 100 people living on the island, mainly looking after the various facilities and the general upkeep of the island. Spread over about 4.8 sq km, Robben Island is also home to a number of wildlife species, including penguins.
All these years, the island was powered by a diesel generator set, for which the fuel had to be transported from the mainland. The DG set consumed nearly 600,000 litres a year. The transportation cost added to the cost of producing electricity. There was, of course, the issue of pollution.
South Africa’s Tourism Department decided to tap renewable energy to power the island and floated a tender.
SOLA Future Energy, a Cape Town-based company, bagged the turnkey contract to install the solar photovoltaic plant on the island, for which it roped in ABB, a global leader in power and automation technologies, to provide the microgrid consisting of the solar farm, storage battery and electronic controllers.
The solar farm has a capacity of 666.4 kW and the lithium-ion battery can store up to 837 kWh of electricity, which can be used at night or on cloudy days.
ABB’s smart microgrid controller ensures that the diesel generator switches on automatically, if either the battery has run out of charge or the sun is low, thus, ensuring that there is no black-out on the island.
According to Ian Burger of SOLA Future, the island uses around 2 million kWh of electricity a year and the solar microgrid can produce about 1 million kWh annually.
The cost of the solar microgrid is about Rand 25 million. The solar microgrid ensures that Robben Island’s diesel consumption reduces by 250,000 litres a year.
This plant will run for more than 20 years and will pay back the investment in five years, according to him.
The Robben Island facility is SOLA Future’s third solar plant and battery installation. The company has also installed 19 rooftop solar plants and a couple more are under installation.
“For about nine months of the year, the island can be powered by solar and battery only, without any need for the diesel generator,” says Markus Bruegmann, Global Product Group Manager, Microgrids & Distributed Generation, ABB.
Nearly 100 museum staff live on the island, which has a lighthouse, a power-intensive desalination plant, and a busy harbour. Robben Island microgrid meets the electricity requirements of a small village.
The microgrid will tap energy from the solar PV plant, equivalent to the average power needed for about 130 homes, according to ABB. The system has ABB solar inverters that convert the variable direct current output from the solar panels into alternating current required for electric utilities.
There are three power producing aspects in the microgrid – the 666.4 kW solar farm, the battery bank that can store 837 kWh and supply 500 kV of peak power, and the diesel generator that will get automatically switched on if either the solar farm is not generating or the battery bank is depleted. According to ABB, the wireless controllers ensure that the microgrid on the island can be remotely monitored from Cape Town.
Microgrids, according to Buergmann, are a growing business, not just in the developing world, but in developed countries too.
In emerging markets, the growth comes from the need to have access to electricity and for reducing fuel cost.
In mature markets, commercial and industrial consumers that want to invest in renewables are driving the growth of microgrids. In African countries, the habitations are far-flung and it may not be viable to have the main grid covering them.
In these situations, it makes economic sense to have local generating sources of electricity and a microgrid to cover that habitation alone. This can at a later date be connected to the main grid, as and when that becomes a reality.