Microgrids with up to 50% intermittent generation (solar photovoltaics, wind energy, etc) don’t need energy storage systems, so long as automation systems are utilized to help with grid stability, according to new research from ABB.

The new work suggests that the old “upper limit” of 40% intermittent generation to a microgrid without energy storage systems was perhaps too cautious. The findings are the result of an analyses of various microgrid scenarios, including: low-penetration scenarios where renewable energy accounted for up to 30% of peak load; medium-penetration scenarios where it accounted for up to 50%; and high-penetration scenarios where it accounted for 100%.

“When you look at a low-penetration system, if you design and maintain it properly, you don’t need much more capex upfront,” stated ABB’s microgrid global sales manager, Pablo Astorga, while speaking earlier this month at the Microgrid Global Innovation Forum in Barcelona.

After this level is surpassed, though, automation systems become a necessity — especially in order to deal with renewables penetration of up to 50% of peak load — according to Astorga.

“As you move close to 100% (of peak load), say 75%, 80%, or 90%, you definitely need some kind of storage device, because the automation (system) can only absorb so much.”

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Even at this level of penetration, it is likely that a portion of the total load will be covered by diesel. A 100% coverage of peak load in megawatt terms equates to roughly a 70% contribution from wind in terms of megawatt-hours, or 50% from solar.

The exact point at which storage might be required will vary based upon the load profile. But “if the project is properly designed and optimized in the right way, up to 50%, you could run with just an automation system,” said Astorga. “I wouldn’t say it’s always going to be the case, but I have seen it.”

He also noted that the findings for microgrids were not applicable to considerations of renewable energy penetration levels in traditional power grids. “I do not think we can generalize for the larger grids, but I do think a higher penetration level [than now] could be accepted without chaos,” he said. “PJM could go up to 30% penetration and it would be fine.”

Choosing the right renewable energy integration strategy for microgrids is important, ABB says, because poorly integrated intermittent energy sources can result in an increased number of genset stops and starts and frequency or voltage variation.

The sweet spot with regard to levelized cost of energy is, according to Astorga, around 60% to 80% coverage from renewable sources.

Astorga noted that the falling costs of renewables and the volatility of fossil fuel prices is pushing ABB and others to integrate more and more renewable energy into microgrids.