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Reduced Inertia, Holding Back Renewables?

image credit: ID 156313508 © Roaminegg |

The ‘Little Engine That Could’ used determination to get up that steep hill.  Originally, renewables faced a similar challenge.  Doubts about reliability and capacity plagued the start of utility-scale wind and solar.  Chanting “I think I can, I think I can,” the clean energy industry has pushed onward and upward.  Gaining speed and appeal, many are turning to renewables as an energy source.  East Central Illinois is facing a major decision regarding their energy generation.  Will they pursue a new coal mine or support a comprehensive bill in the General Assembly called the Clean Energy Jobs Act (CEJA) which seeks to ramp up renewable energy development in the state?  The CEJA commits Illinois to 100% renewable energy by 2050.  Wind now makes up 7.6% of Illinois’s electricity generation.  However, nuclear supplies the bulk of electricity generated in the state, followed by coal and natural gas.  Looking forward, there are 30 wind projects currently under construction or proposed in Illinois.  Globally, the pandemic has slowed progress.  Some 40 percent of wind and solar projects scheduled for the rest of the year have been delayed, stated Logan Goldie-Scot, head of clean power research at analysis firm BloombergNEF (BNEF).  Stay at home orders have interrupted construction and stopped production of solar panels and wind turbine parts. 

Compared to coal, renewables are actually doing quite well despite the pandemic.  Renewable sources have surpassed coal in energy generation in the United States for the first time in 134 years.  Electricity generation from coal fell to its lowest level in 2019. The US Energy Information Administration (EIA) expects renewables to eclipse coal as an electricity source this year.  “We aren’t going to see a big resurgence in coal generation, the trend is pretty clear,” said Dennis Wamsted, analyst at the Institute for Energy Economics and Financial Analysis. 

Renewable sources have accounted for an increased share of power generation for several reasons. The low cost of solar and wind power means they are often dispatched to grids before other sources such as coal and nuclear power.  Future forecasting predicts, in a decade, more than half of the electricity generated in the U.S. will come from clean, renewable resources supported by energy storage.  The Solar Energy Industries Association (SEIA), American Wind Energy Association (AWEA), National Hydropower Association (NHA) and Energy Storage Association (ESA) have agreed to back this effort.  “We are pleased to join forces with our clean energy friends to substantially reduce carbon emissions by 2030, building a more resilient, efficient, sustainable, and affordable grid for generations to come,” said ESA CEO Kelly Speakes-Backman.

The idea of shifting to renewable generation carries concerns about grid inertia and energy security.  Think of a moving object, it will keep moving until another force causes it to stop. After reaching the top of a hill, a train going downhill could store enough energy to continue in motion for quite a while.  All electricity grids have a certain level of inertia at any given time.  Grid operators use inertia to control the stability of the grid, by balancing second-to-second supply and demand.  Inertia in power systems is the energy stored in large rotating generators or motors, which tend to continue rotating. This stored energy is valuable when a large power plant fails because it can temporarily make up for the power lost from the failed generator.  Renewable energy sources do not create much inertia, for example, when there is no wind, a wind turbine will stop spinning immediately.  Is reduced inertia a game-changer?  Would renewables fail to support the demand?  Not necessarily.  Paul Denholm, NREL principal energy analyst, says ”First, it's true that these resources decrease the amount of inertia available on the system. But second, these resources can reduce the amount of inertia actually needed—and thus address the first effect. In combination, this represents a real paradigm shift in how we think about providing the grid services that maintain system reliability.”  Denholm believes that with the right technology (inverter-based resources), reduced inertia does not pose a significant technical or economic barrier to the growth of wind, solar and storage in the United Sates.  Coupling renewables with energy storage has produced good results in the past.  Perhaps the next ten years will lead to a congratulatory, “I thought I could, I thought I could” for the industry.

Until then, will Illinois continue to employ both nuclear and coal power generation to guarantee reliability?  With renewables outperforming coal, how do see the future of generation shaping up?  And how far are we from reaching 100% renewables? 

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