Mechanical Technology July 2016

⎪ Special report ⎪

driving the implementation of microgrids, according to Duarte, “is to reduce the carbon footprint of electricity generation as a whole”. “The management software allows us to make decisions on a mil- lisecond basis as to how to generate the electricity needed in the cleanest way possible,” he says. Talking about advancing renewable penetration, he says that in spite of the rise in installed renewable capacity in South Africa as a result of the REIPPPP, the penetration of renewables in terms of supporting load demand remains low. “Current generation capacity is at around 43 GW and we now have some 3 000 MW of installed renewables. This translates to an installed penetration of around 6.0%,” he says, comparing this to Germany, where up to 78% of daily electricity demand could come from renewables. “But high renewable penetration in- troduces power supply volatility, which creates difficulties for system operators, who need to balance the grid via deflec- tions and stabilisation strategies. “While all renewables are associated with volatility, the battery storage and flywheels embedded in microgrids are an ideal way of managing this. Distributed microgrids, at suburb level for example, can significantly increase overall renew- able penetration, while making the whole system more stable and reliable. Even if hundreds of microgrids are intercon- nected, each one balances itself, so the grid itself is not destabilised in any way by the variations in renewable energy generation,” he assures. Modelling local load profiles Another distinguishing feature of the microgrid is that emphasis is placed on modelling the generation needs based on the load profile of the facility or area to be supplied. “There is a concerted and upfront effort to balance the generation/ supply equation. It is not just a matter of putting up a PV system, connecting it to the distribution boards and hoping it will generate as much power as possible,” Duarte argues. ABB offers upfront power consulting, which results in investment cost savings by ensuring a reliable consumer-oriented system and power quality. Operational cost savings are also achieved: by optimising network configurations and the intelligent use of modern automa- tion equipment; and maintenance cost

The 380 kWh Li-ion battery bank and PowerStore controller are all housed in three ‘plug-and- play’ containers.

quired, the load curves and the response envelopes. The microgrid analysis report includes a business case, which makes for a bankable solution that can be taken directly to a funder. “We strive to find the sweet spot with respect to capex and opex, which, ideally, combines genera- tion options for lowest LCOE, highest reli- ability and resilience and least possible environmental impact,” he adds. From a reliability perspective: “ABB has over 25 years of experience in this field and its research and development department is turning 100 this year. We have a service and remote monitor- ing capability that enables web-based monitoring to be implemented on any plant anywhere in the world,” he says pointing towards the prevailing genera- tion and load profile of the Longmeadow demonstration plant.” The online monitoring system shows PV generation at 364 kVA, with the grid draw being reduced to 650 kVA on a 1.14 MW load. “In the event of a grid outage, it will first bring in the PowerStore from batteries, and if the outage lasts longer than 15 or 20 minutes, the diesel generators will automatically kick in to meet demand load,” he explains. In the municipal context, there are numerous ways that Microgrids can play a major part, not only in the southern African region, but especially in South Africa too. Across Africa, Duarte sees modular and containerised microgrid solutions as ideal for augmenting weak grids. “For new factories being mooted in places with power limitations, and mu- nicipalities striving to supply the stable power needed for emerging economies to thrive, microgrids are an increasingly viable option,” he concludes. q

reductions through the implementation of reliability centred maintenance. At the starting point of this offering is a grid study to determine the prevailing load and connecting standards. “If the load turns out to be lower than the gen- eration capacity of the chosen solution, then the initial capex investment will never be used to its potential. Conversely, if the renewable component of a chosen system is too small, then the likely return on investment will also be low, as will emissions reductions. “As part of our grid study, we also determine how to comply with local regulations. Whether in rural Africa or here in Longmeadow, systems must all comply with power quality requirements and safety regulations,” he says. Adding to this offering is a steady state analysis – how much power is needed under normal operating condition, which governs the overall capacity (kVA) of the microgrid – and a dynamic analysis model is also needed: “The effects of step loads being introduced, the need for critical loads to retain their supply and the impact of partial supply outages all need to be taken into account,” Duarte explains. “This helps to size the battery store or flywheel capacities, for example. It also helps to identify ways of expanding the system, when the need arises.” Depending on the size of the system and the variety and number of genera- tion sources, the complexity of microgrid increases. To cater for this, visualisation and automatic control functionality has to be introduced – “and this is where ABB really excels,” believes Duarte. From the analyses performed during the consulting phase of a project, ABB is able to make specific recommendations about the generation components re-

Mechanical Technology — July 2016

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