Researchers at the University of the Witwatersrand (Wits) are aiming to commercialise a plug-and-play direct current (dc) microgrid innovation, which is incrementally scalable to any number of power sources, loads and batteries.
The direct current solution has already been proved at laboratory level through a test-bed prototype, which has been operating at the respected Johannesburg higher education institution since 2014.
A preliminary patent has since been secured and Wits Enterprise, which markets and commercialises the university’s intellectual capital, is now offering the system to commercial enterprises as a partnership opportunity.
Professor Willie Cronje, who has overseen the research at the School of Electrical and Information Engineering, tells Engineering News that the 12 V system is easy and safe to install and has been designed as a flexible alternative to the “closed architecture” solar home systems currently on the market.
Its main distinguishing feature is that the owner can add both power and load incrementally using off-the-shelf components, whereas, with closed systems, the only way to add capacity is to buy an entirely separate home system.
Cronje explains that the scalable dc microgrid has been designed using principles adopted from utility grids, whereby various supply, battery and load configurations are regulated and balanced using predefined performance parameters.
An interfacing unit independently connects the load, such as a light-emitting diode (LED) lamps, the power from the solar photovoltaic (PV) panel and the battery, which can have any chemical composition, within an integrated system.
“No central controller is needed as each unit ensures self-regulation within established voltage parameters,” Cronje explains. Should the voltage dip below 10 V, owing to overloading, the whole system will trip, but will immediately restart if excess load is disconnected. Should it rise above 13 V as a result of PV overproduction, the controller on the PV panel will throttle output to maintain balance.
“This unique feature lends the system to scalability and modularity,” Cronje explains.
He adds that efforts have been made to use commonly available components so as to improve prospects of low-cost production. For instance, the connections are based on standard car cigarette lighters, which makes cellphone charging through a simple USB connection as easy as connecting a string of LED lights.
Cronje believes there is particular potential for the system in the rest of Africa, given the high levels of electrification in South Africa.
However, he says there is still domestic scope in some far-flung communities in the Eastern Cape and KwaZulu-Natal, where the prospect for grid connectivity remains low. In these areas, concessions are already being made available for companies to install solar home solutions, and Cronje believes the Wits system could offer an attractive alternative.
Nevertheless, the spread-out, distributed nature of settlements across Southern Africa, together with the low load profile of such communities, would provide the main market opportunity for the system.
“Current off-grid solutions do not accommodate multiple types of power sources and are restrictive in terms of the loads that can be connected. Therefore, we are confident there is good potential for our solution, as long as it can be commercialised at a price point that is affordable,” Cronje concludes.