How the Massive Growth in Solar Power Is Affecting Power Grids

The Solar Energy Industries Association (SEIA) reported in March that the U.S. solar industry installed 32.4 GWdc of capacity in 2023, a remarkable 51% increase compared to 2022. It was the industry’s biggest year by far, exceeding 30 GWdc of capacity for the first time. Overall, photovoltaic (PV) solar accounted for 53% of all new U.S. electricity-generating capacity additions in 2023, making up more than half of new generating capacity for the first time. The utility, commercial and industrial, and residential sectors all set annual installation records, while the community solar sector was within 5 MWdc of an annual record.

Yet, this is not just a U.S. story, solar capacity is growing exponentially around the world. In its Renewables 2023 report, the International Energy Agency (IEA) said 2023 saw a step change in renewable capacity additions, driven by China’s solar PV market. It said global annual renewable capacity additions increased by almost 50% to nearly 510 GW last year—the fastest growth rate in the past two decades. 2023 was the 22nd year in a row that renewable capacity additions set a new record, according to the IEA.

While the increases in renewable capacity in Europe, the U.S., and Brazil hit all-time highs, China’s acceleration was extraordinary. In 2023, China commissioned as much solar PV as the entire world did in 2022. Solar PV accounted for three-quarters of renewable capacity additions worldwide.

Utility-scale projects are what really drive the industry. In the U.S., utility-scale installations spiked to 22.5 GWdc of capacity, according to SEIA, a 77% increase over 2022. The temporary moratorium on anticircumvention tariffs applicable to certain imports from four Southeast Asian countries brought some relief to the solar supply chain, helping projects move forward last year. The moratorium ends in June 2024, however, so we’ll see how that affects projects in the second half of this year.

The Texas Grid Evolves

Texas was the leading state for solar installations in 2023. Since 2021, more than 15 GW of new solar capacity has been added in Texas. Furthermore, SEIA predicts Texas will lead the nation with nearly 100 GW of new solar capacity additions from 2024 to 2034, outpacing the next closest state by a two-to-one margin.

According to the Electric Reliability Council of Texas (ERCOT), the grid operator for about 90% of the load in Texas, solar generation supplied 32.4 TWh to its grid in 2023—7.29% of the annual total. In the first quarter of 2024, the percentage increased to 8.16%, which is notable because the winter season is not typically a prime period for solar production. It’s also notable in that solar was not far behind nuclear (9.92%) or coal (12.10%) in ERCOT’s first quarter energy mix. Natural gas–fired generation (40.42%) and wind (29.41%) were the clear leaders in Texas, however.

While solar only accounts for 13.2% of Texas’ installed capacity, according to ERCOT’s December 2023 Capacity, Demand, and Reserves (CDR) report for Summer 2024, it can have a significant impact on the grid during peak times. An April 2024 ERCOT fact sheet shows the solar generation record of 18,881 MW was set on March 28 this year. The solar penetration record was also set that day at 42.98%. While those numbers are astounding, it seems likely that the generation record will be eclipsed sometime this summer, and on a regular basis in the not-to-distant future.

The Duck Curve Waddles into Texas

The increase in solar generation in Texas is starting to create a duck curve in the ERCOT grid, similar to what has long been observed in the California Independent System Operator’s (CAISO’s) grid. For a little background, the duck curve was first brought to light in 2013 when CAISO published a chart that showed the difference in electricity demand and the amount of available solar energy throughout the day. The curve was a snapshot of a 24-hour period in California during springtime, which is when the effect is most extreme because it’s sunny but temperatures remain cool, so demand for electricity is low because people don’t need to use much electricity for air conditioning or heating. CAISO showed how the pattern created by the midday dip in the net load curve, followed by a steep rise in the evening when solar generation drops off, looks like the outline of a duck, hence the name.

Since 2013, California’s duck curve has only gotten deeper as more and more solar power has been added to the CAISO grid. In fact, on some days, the net demand curve is going negative in California.

The situation in Texas is nowhere near as extreme as that seen in California. However, the increase in solar generation is beginning to have a noticeable effect. The U.S. Energy Information Administration (EIA) published an article on April 9 comparing ERCOT’s average hourly electricity generation in winter 2022–2023 to winter 2023–2024. The solar-caused dip was distinctively larger this past winter. Furthermore, it’s been observed that the duck curve is increasingly occurring in other parts of the world in places where the share of solar generation is growing compared to generation from conventional sources.

Every power grid is different and operators will end up dealing with increases in solar capacity in their own unique ways. In ERCOT’s case, it has much more dispatchable gas-fired generation to play with than CAISO does and its significant wind resources tend to complement solar rather than amplifying the problem, so it may have an easier time managing the situation, at least for the time being.

Aaron Larson is POWER’s executive editor.

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