Electricity and Control October 2022

ENERGY MANAGEMENT + THE INDUSTRIAL ENVIRONMENT

Options in alternative power sources As the reality of ongoing load shedding continues, South African households and businesses, in particular smaller businesses that do not have the means or space to invest in large generators in an office or warehouse environment, are looking for alternative power sources to keep the lights on. Gregor Küpper, Managing Director of SOLARWORLD Africa, says there has been a marked uptake in renewable energy solutions as energy users seek ways to see them through those load shedding hours.

Gregor Küpper, Managing Director, SOLARWORLD Africa.

“ S olar used to be a solution only for large scale busi nesses, or organisations with adequate space to house enough panels to support their electricity consumption,” Küpper says. “Thanks to innovations in this space, people working from home and small businesses now have several options available to them, to provide tem porary support when there is a power cut and, potentially, long-term relief as the preferred ongoing power source.” The SOLARWORLD Africa team has almost 40 years’ experience and a proven track record in sub-Saharan Africa. Küpper explains some of the solutions that will keep the lights on – or the kettle boiling – and machines running during load shedding, enabling homeowners and small businesses to become more self-sufficient or grid independent. There are different types of energy systems: on-grid (grid-tied), off-grid, and on-grid with backup. “Grid-tied so lar photovoltaic systems are most common in South Africa, as these are the most affordable and offer the best business case. However, grid-tied solar PV systems will generally be programmed to switch off during load shedding.” Küpper says this is primarily due to international safety standards. The different solutions available are outlined below. Grid-tied photovoltaic system A solar photovoltaic system is an electric power system de signed to supply usable solar power by means of photovol taics. The two main components are PV panels (supplying dc power) and a grid-tied PV inverter (converting dc to ac power). The grid-tied PV inverter converts the varying dc power, from the PV panels, into ac power and feeds it to the house hold/business equipment, and possibly into the grid. Importantly, a grid-tied inverter synchronises the fre quency and the output voltage to its connected grid. If solar energy supply is insufficient, a grid-tied inverter switches and starts drawing power from the grid into the home or business premises. It ensures there is a seamless power supply. “This option saves electricity in the long run, no backup required. The pure PV inverters are grid-tied, which means they require the grid to switch on and convert the direct current (PV) into alternating current, which is required to power the appliances in a home or business.”

On-grid with backup - PV and battery

This is a backup and later self-consumption optimisation (SCO) option. Self-consumption contributes to the stability of the distribution grid by avoiding voltage rise during peak PV generation periods, such as the middle of the day, and helps to reach higher shares of installed PV in the electricity mix. “A PV and battery system can be served by either a hy brid (PV and battery) inverter, or separate battery and PV inverter. The batteries act as backup power when the grid has failed – that is – during load shedding or a power out age. During a normal day, PV can provide power to a house and charge the batteries. The stored power can then be used during the night, which is what is referred to as SCO.” - Battery backup This is purely a backup solution and usually sized to make sure that the essential loads are up and running during load shedding or a power failure. Battery backup constitutes various options: a UPS (uninterruptible power supply), battery together with a charge controller, and then of course the battery and battery inverter. Of these, a bat tery with a good and reliable battery inverter is the most reliable solution. - Battery and hybrid inverter This is the same as the battery and battery inverter op tion except that it allows the user the opportunity to install PV panels at a later stage, without having to add the extra cost of a PV inverter, as it would be ‘PV-ready’. Off-grid In the current South African energy environment, the off grid option sounds very attractive. It does however require careful planning and sizing of the system. The user would require a large enough PV array to serve daily loads and charge the batteries for use at night. And in turn, a large enough battery bank to serve the loads during the evenings and possibly during daytime, when there is not enough PV energy generation. There is, otherwise, the option to add a generator or to use the grid as backup. Küpper advises that a tailored approach will see various renewable energy solutions and products being recom mended and made available. “Households and business

OCTOBER 2022 Electricity + Control

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