Stellenbosch University
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Taking renewable energy into the future
Author: Afdeling Navorsingsontwikkeling, Division for Research Development
Published: 14/10/2019

​​In the light of recent #climatestrikes around the world, Prof Ntshengedzeni Sampson Mamphweli’s work as director of Centre for Renewable and Sustainable Energy Studies (CRSES) is more important than ever.

CRSES, based in the Faculty of Engineering, serves as a national hub for postgraduate studies into the development of renewable and sustainable energy. This includes bioenergy, solar photovoltaics, solar thermal, wind and hydro power options. The Centre, which also conducts anything from initial feasibility studies to highly technical investigations into new technologies, was established in 2007. A decade later, Prof Mamphweni followed in the footsteps of outgoing founding Director Prof Wikus van Niekerk, when he became dean of the SU Faculty of Engineering in mid-2017.

For his talk on 16 October 2019 as part of the Division of Research Development’s Forward with Research Impact lecture series, Mamphweni will be focusing on thermochemical and biological techniques can be used to convert biomass into energy. It takes place at 13:00 in the Old Main Building on campus.

South Africa’s renewable energy future

South Africa has committed to supplying at least 32% of its energy needs by 2030 through clean technology and renewable energy sources. This is the target set out in the Integrated Resource Plan 2018.

“Although it’s higher than the national target, I think at least 40% is possible for us,” challenges Mamphweli, who is inspired by the likes of India, a country heading towards a 90% renewable energy target.

Among his many responsibilities, he coordinates renewable energy research between South Africa and India, under the BRICS banner. This initiative will ensure more combined research projects and student exchanges between the countries.

He also drives stronger coordination of renewable energy research matters between African universities and centres, as co-director of the Centre of Excellence in Energy. This forms part of the African Research Universities Alliance.

Although he’d like to see that more of the technologies that have been developed or studied at local universities over the past decade actually be implemented, he remains a realist.

He believes the country can be pricewise competitive when it comes to producing the infrastructure needed to generate wind energy, biogas and solar thermal energy. The much cheaper photovoltaic infrastructure available via China is however a totally different story. An option would be to aim for at least the partial assembly of technology on the home front, to ensure that jobs are created locally.

Biogas expert                                                                                                                    

Mamphweli’s renewable energy expertise was shaped through his studies of biogas and syngas (synthetic) production, with waste materials such as wood waste, mealie cobs and manure as fuel. If he could have his way, there would be more biodigesters to generate biogas in back gardens in South Africa than is currently the case. Such technology would also be used in urban areas, instead of only being dotted around the countryside. He also sees room for municipal sewage works to generate their own electricity, using the methane gas that is in any case generated as part of their mandatory cleaning of wastewater, and is currently merely burnt.

A biodigester, in short, is a dome-shaped, roofed construction made from brick, plastic or steel fitted into the ground. It is filled with waste that may be animal dung or even human faeces. When water and bacteria interact with it, the material decomposes to release methane gas. An outlet pipe then takes the gas to whatever needs to be powered – be it a gas engine, a gas turbine or a stove. Gas can also be trapped in a canister or special bag for later use.

Biodigesters are widely used in China and India. While explaining the basics behind it, Mamphweli makes quick sketches on a blank piece of paper. After years of experimentation, he knows that it takes a near-perfect 50/50 match between manure and water to generate methane gas.

“About 25 kg of cow dung gives you 1 cubic meter of gas. That’s 6 kilowatt hours or six units of electricity, with which you can cook for five to six hours,” he sets out, making the technology look deceptively easy.

As a panel member of the National Biogas Platform, he however knows that there’s more to it than just trapping gas. One has among others to do gas scrubbing, which is a way of purifying and filtering the gas.

He acknowledges that some people find feeding such systems with available dung from livestock too tedious a household chore, even if it is giving them free energy. There are ways to sidestep such qualms, too, he says. The solution is to basically connect the system directly to a household’s sewage system.

“What you need is an inlet and an outlet, and a container to trap the gas in,” Mamphweli explains, still sketching away. Pre-empting the groans of the squeamish, he quickly adds: “You don’t even have to come in contact with it (the effluent).”

One of his PhD students has recently started to build a biodigester on the University’s Mariendahl experimental farm outside Stellenbosch. Manure, obtained from the pigsties on the farm, will be used to produce and capture methane gas, which will drive a 10 kW gas engine. If successful, it can be used to power outdoor lighting on the farm.

Early years

Mamphweli came to Stellenbosch via the University of Fort Hare, where he started as an Eskom Research fellow in 2005. It was in the Eastern Cape where he started to think about the nitty-gritty of biomass conversion, as part of the PhD in Physics he obtained in 2010. It was about biomass gasification. After graduating, he started research on biogas digesters. It led to hundreds of biodigesters and solar panels being installed in the rural Eastern Cape and areas bordering on Lesotho as part of his research endeavours.

He’s always had a particular affinity for physics. Today, he laughs at his younger self who tried to explain everything happening around him to his teenage friends in terms of physics. In his final matric exam he scored 100% for the subject, but was let down by the chemistry part, which he did not like during his days at high school.

This younger self dreamt of becoming a pilot, and as a second choice, a doctor. However, after matriculating from Lwenzhe Secondary school in Limpopo in 1997, the would-be bespectacled professor wasn’t even invited for an interview by the national carrier’s cadet academy. A lack of funds stopped him in his tracks after being accepted for medical studies at MEDUNSA.

“The letter (of acceptance) indicated how much I had to pay and all that. It was about R20 000 that I needed, which we did not have at home. I did not have a bursary, so I walked into the University of Venda, and applied to study there,” he remembers how it came about that he started to study 20 kilometres from home.

His choice fell on environmental science, because of his soft spot for nature.

“I told myself that one day I’d be working in the Kruger National Park,” Mamphweli remembers the challenge he put himself.

That’s one dream that did materialise. After completing his honours degree, Mamphweli found himself in the Kruger Park between 2002 and 2004, studying the impact of elephants on the trees along rivers to the southern side of Africa’s oldest nature reserve. He used the time and data collected to complete a masters degree on the subject.

“I still think my best life was in the Kruger National Park,” says this avid birder with also has a penchant for fast cars. “I go there every chance I get.”

He had the option of studying elephants for his PhD too, but was intrigued by an advert for a PhD position to study biomass gasifiers at the University of Fort Hare, as part of the Eskom Research Fellowship Black Researchers Development Program.

“I am not at all, not at all sorry about that decision,” he reiterates, saying that he believes he is making an impact on community level by the installation of biodigesters, and also on a national level.

“I love nature, but I also love the energy side of things,” says the professor, who is currently editing a book on independent power producers in Africa.