Mechanical Technology July 2016

⎪ Special report ⎪

and greener power solution

Above: ABB’s Longmeadow facility now has a 750 kWp, monocrystalline rooftop PV system connected to a microgrid. Above right: A PowerStore TM battery-based grid stabilising system takes up the load immediately when the grid goes down. Right: The dc power from the panels is passed through a single PVS 800 630 kW ABB inverter to generate the ac supply. “So while microgrids can be grid con- nected, as we see at our demonstration plant here in Longmeadow, they are also 100% ‘islandable’. Here, we have grid- connected power, PV solar generation, the battery and diesel generation all interconnected via a common ring and automatically managed by the Microgrid Plus distributed control system (DCS). The unique feature of ABB’s microgrid control system is that it has a distributed network of controllers allowing for redun- dancy, expandability and maintenance to take place without interrupting genera- tion of power. “As soon as an outage is detected, the PowerStore provides the reference for off-grid generation. Then, when the grid comes back on line, the PowerStore resynchronises, which will cause the off- grid generation sources to follow. The grid can then be safely brought back into the supply mix,” he adds. Key features of microgrids The core purposes of ABB’s microgrid solutions is power security and grid resilience. Since no single generation option is able to offer this all of the time, it makes sense to combine power generation sources to make sure power is

generation itself,” he informs MechTech . A second objective is to achieve the lowest possible levelised cost of energy (LCOE) from a combination of generation sources. “Levelised cost of energy is a stream of equal payments, normalised over the expected energy production period, that would allow a project owner to recover all costs – including financing and an assumed return on investment over a predetermined financial life. This value is expressed as a tariff per kWh of generation,” he explains, adding, “gener- ally calculated for a 20-year life.” With this information, ABB’s Microgrid Plus DCS is able to optimally combine available generation sources to meet prevailing load demand at the lowest possible cost. And the third important imperative

always available. “While seamless power changeover is not always necessary, it is now a primary part of our offering and is often essential,” Duarte suggests. “Probably the largest microgrid market is in the USA, where you would think they have no need of it. Why? Because of the increasing occurrence of natural disasters, which tend to take out the grid and cripple the affected community. To minimise the impact of such events, the power needs to be restored immediately and microgrids are being installed on a redundancy basis to back up the grid in high-risk areas. Typically these are large systems of between 10 to 100 MW, but there is no capacity limit since the technology involves the management and coordination of generation, not the

Mechanical Technology — July 2016

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