For South African municipalities, microgrids present a strong business case in terms of power security and sustained supply, especially for critical infrastructure during downtime on the national grid.By Shireen Sayed The latest update to the South African government’s Integrated Resource Plan (IRP) places increased emphasis on the greater integration of renewable energy generation. In addition, the IRP gives municipalities permission to consider alternative ways to generate electricity through decentralised alternatives that take pressure off the national grid. It’s no secret that Eskom’s ageing power stations, and a growing maintenance backlog, has made loadshedding a regular feature for the foreseeable future. Aside from the economic fallout, scheduled and unscheduled power cuts have a devastating impact on municipal service delivery, especially in terms of water purification and wastewater management. The shortfall in electrical infrastructure investment also fails to close the gap on regional community electrification projects. Within this context, clean energy-powered microgrids help to bridge the divide while lowering dependence on fossil fuels. These microgrids can typically range in output from as low as 10 kW to over 100 MW. They are diverse in nature and size, depending on the load, location, and resources. However, with few exceptions, their power source is derived from renewable energy. Options include solar photovoltaic (PV) systems, wind turbines, hydropower, and biomass, or some hybrid of these that incorporate diesel or gas generation as a backup when the sun sets, or the wind drops. Before rushing in, though, municipalities need to do their homework to ensure the microgrid systems selected meet the requirements and deliver according to expectations. Battery storage Energy storage, which includes battery storage, plays a critical function in terms of making microgrid energy supply predictable and readily available on demand. Furthermore, it improves microgrid stability by acting as a buffer against renewable intermittency and mitigates load uncertainties. Therefore, choosing the best fit-for-purpose battery storage system (BSS) is crucial since this represents one of the highest cost items within the overall microgrid set-up (between 20 to 30% of the overall capital cost over its lifespan). In today’s market, battery options include Redox Flow, Lead-acid, Li-ion, Nickel-Cadmium, and Nickel Metal Hydride. Due to their simplicity, Li-ion and Lead-acid batteries are popular for the rural microgrid market. Either way, BSS optimisation and application requires a comprehensive understanding of how batteries behave under various operating conditions. These include exposure to temperature variations, as well as charging-discharging. Typically, a microgrid comprises several battery storage units, with each unit having a varying degree of output capacity depending on factors such as initial State of Charge (SOC), efficiency, aging (i.e., number of cycles), and temperature conditions. Ideally, the BSS should function as a well-synchronised system. Battery management system To be able to manage any differences between the various batteries, and to ensure stability, a Battery Management System (BMS) is required to monitor and control vital functions of the BSS in real-time. The BMS relays information such as temperatures, voltages, currents, maintenance scheduling, battery performance optimisation, failure prediction and/or prevention, as well as battery data collection/analysis. The function of battery optimisation must be considered as part of the overall microgrid design right from the onset to achieve maximum results from the storage system, as well as from the overall ability of the microgrid to respond adequately to the energy demand. For microgrid applications, there are some quick wins in terms of achieving optimisation of the BSS. These include:
- on the ground optimising incorporating the correct positioning of batteries, adequate ventilation, or insulation of the battery storage facility
- fully trained resources to carry out repairs and maintenance
- the quality and technology of the energy storage systems must be carefully selected and designed.
Benefits for municipalitiesIn addition to a degree of autonomy, towns and cities have a greenfield opportunity to map out their current and future microgrid footprint in line with their energy requirements. Any additional power that is not used can be pushed into the transmission grid and offset as savings to the municipality. Revenue streams can also be guaranteed by installing prepaid smart metering to ensure payback on the initial investment and longer-term profit generation. In addition, investor confidence is restored when there’s an assurance of sustained power to support current and future industrial and commercial expansion within the municipal zone. Case studies from Africa and the world As statistics from IRENA and allied bodies show, the traction for microgrids and renewable energy in general is rapidly gaining ground in both the developed and developing world. On the African continent, a prime example is Tanzania. According to various literature, just under 40% of the population of Tanzania had access to electricity in 2017. With a concerted effort from the Tanzanian government, this deficit is steadily narrowing. Today Tanzania is recognised as a regional leader in micro-grid deployment with over 100 microgrid systems serving businesses and local communities. These microgrids are either government-owned or owned by private developers selling electricity back into the national grid through power purchase agreements or sold directly to end consumers. While Tanzania has been successful in the deployment of microgrids, there have been challenges, one of which has been funding. Power for residents: Netherlands The first microgrid installation in the Netherlands was at a holiday park in Bronsbergen, approximately 100 km west of Amsterdam. A microgrid was built to provide 208 homes with 315 kW of solar-generated power, with an energy storage capacity of 700 kWh. The microgrid is connected to the national grid via a 10 kV line. Clean energy for wastewater treatment: California A proposed microgrid project is underway for the wastewater facilities in McKinleyville Community Services District (MCSD) in California incorporating the existing diesel generators with solar PV and battery storage. The MCSD serves an estimated 16 900 residents and provides key services such as clean water reticulation, wastewater processing, maintenance of parks, etc. The outcome of the project is a wastewater treatment facility that has a target of net zero emissions. In addition, the microgrid will provide the facility with energy resilience. Conclusions In all three of the above case studies, there’s a similar solution-specific role for microgrids across South Africa, and for our municipalities, working in conjunction with independent power producers to speed up their implementation. Power supply has a direct impact on service delivery. And the lack of power for water reticulation or wastewater treatment can have catastrophic implications. Here microgrids give municipalities greater control to improve energy efficiencies and security, as well as flexible options in terms of modularity and scalability. As with any infrastructure investment, the starting point is a comprehensive needs analysis, which includes researching optimum BSS and BSM technologies, existing and future distribution networks, and operations and maintenance costs. Studying and learning from international microgrid experience within the municipal space is equally important. Funding mechanisms are available to support the deployment of microgrids in Africa. However, the financial modelling must make a sound business case for lenders and investors. A positive step in this direction is the South African government’s decision to increase the non-licensed threshold to 100 MW for independent power producers. This opens the door for more microgrid opportunities. In municipal deployment, the main aim is to produce clean electricity at the lowest cost through optimisation. In this respect, microgrids can serve as a catalyst for much-needed economic recovery and growth. Ultimately, microgrids should form part of all municipal strategic development plans now and into the future.