Microgrids offer advantages for reliability and bringing more renewables onto the grid.
1. What are the benefits of integrating renewable energy with microgrids?
The obvious first benefit is related to cost of generation reduction. With the increasing costs of traditional fossil fuel based generation, such as diesel, and the reduction in dollar-per-watt cost for renewables such as wind, the tipping point for renewables in remote microgrids has been passed. For remote and islanded areas such as Alaska, Northern Canada and the Caribbean, which have excellent wind and solar resources, it’s a no brainer. A secondary benefit, and some would argue just as important, is the avoided environmental impact due to transport and storage of fossil fuels in these remote pristine areas.
2. Do microgrids increase the reliability of the grid?
If we are looking at the main utility grid, the short answer is yes. By having distributed generation assets throughout the network it gives utilities the ability to call upon these assets for ancillary services in times of need. This may be in the form of peak shaving during peak power demand on hot summer days or cold winter periods, or it could involve frequency regulation. A lot of utilities are currently deploying pilot projects whereby a section of the main grid has the ability to seamlessly transition from grid-connect to islanded mode. There are technical obstacles that need to be overcome but these microgrids are driving towards maintaining electrical supply to mission critical infrastructure such as hospitals, police and fire services as well as data centers.
3. How do microgrids deal with the uncertain ups and downs of wind and solar power?
In main grid applications the connection point is generally strong enough to withstand the fluctuations from wind and solar. In remote microgrids the problem is magnified due to the limited amount of inertia in the system. Historically, to mitigate against intermittency, operators would curtail the renewable asset so as to reduce the voltage and frequency excursions. ABB has developed a microgrid control system called the MGC600 and flywheel inverter system called the PowerStore that allows microgrids to run 100% renewable mode and transition back to fossil-based generation when the renewable resource goes away. The PowerStore injects and absorbs real and reactive power within 5 milliseconds to counteract the variations from the wind and solar assets. This in turn allows higher penetration and annual contribution from renewable sources, and translates to a better ROI and shorter payback period.
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