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In South Africa, the Absa bank campus in central Johannesburg has proclaimed that it houses a world-class energy centre and two of the largest grey water plants in the country, which can collectively recycle up to 22 million litres of water a year.

“We collect water from the office basins and showers, it is filtered, and UV lights are used to kill bacteria. It is then pumped into holding tanks and used to flush toilets,” says Aveshen Moodley, Absa’s vice president for environmental sustainability.

“It is an energy intensive process, but in an increasingly water scarce world one that pays huge dividends.” The grey water plants, which cost around R7 million each, have already paid themselves off.

Waste heat created by the gas engines is used to heat water for washing dishes and showers, as well as heating the buildings via underfloor heating.

The Energy Centre is manned 24/7 from a control room, which has a distinct spaceship feel. According to the Bank, it is the first site in the world where gas and diesel generators are synchronised, creating enough energy to power up to 2,800 houses. Read more: Exciting potential of 3-in-1 waste-to-power technology

The inner city power generation plant can generate the maximum demand for the entire campus – 11.2MW from gas-powered engines that is 70% cleaner for the environment in comparison to the national electricity utility and 6MW of emergency backup from diesel units. It has run in the underbelly of one of the buildings since 2010 and is now paid off. There is also enough space available to double its generation capacity in future if necessary.

The set up powered 12,000 Absa employees during 2015, when the Bank made a business decision to go off the national grid, and also provides business-as-usual conditions during the current load shedding experienced by the country. This alleviated power constraints on the grid thereby allowing neighbouring businesses to still operate. Read more: Op-Ed: Solving the Eskom dilemma

A solar plant of close to 6,000 panels sits atop a north-facing roof at Towers North. The R10 million plant, a combination of ground mounted system at a 7-storey height and an IBR roof structure, was completed in 2013, and paid itself off this year using measurement and verification of savings.

“This means by the end of this year we will get free energy from the plant, offsetting up to 400kWp of electricity per year.” String inverters convert the energy into usable power.

Moodley said the plant, built when Absa was still part of Barclays, was the first in the group globally, and as such the African team helped to write the global photovoltaic strategy.

In addition, the Bank has a 1,000kWp rooftop solar installation in Pretoria, which provides 17% of that office’s electricity with a single inverter. The R25 million investment will pay itself off next year.

“We will be rolling out five solar plants to other offices and trialling battery technology, to be used when we don’t have sunlight. To this end, we are investigating net zero offices,” Moodley concluded.