The Challenges of Achieving 100% Renewable Energy

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Wind farm

Discussion has been growing lately regarding the pursuit of 100% renewable energy. Achieving that goal already is starting to occur, albeit for only short periods. Portugal reportedly went four consecutive days running on entirely renewable energy. And during a few hours on May 8 in Germany, solar, wind, hydro, and biomass plants reportedly generated approximately 95% of the 63 GW of electricity customers were consuming.

Although these examples illustrate progress, we’re also starting to see the impact of generation drawn almost entirely from renewables. When Germany hit its renewables high, it actually had to pay its commercial customers to consume electricity. And in Hawaii, the only state so far with a mandate to achieve 100% renewable energy, talk has shifted to curtailment as too much wind and solar has prompted renewable facilities to turn down their generation to balance the load.

While utilities can, to some extent, predict customer loads, they can’t control them. Moreover, peak renewable energy generation doesn’t necessarily occur at the same time as peak loads. Often, wind generation peaks during the nighttime hours, when customer loads are low. Solar generation peaks during the middle of the day, when many residential customers are at work, and then it declines as the sun lowers and as customers are returning home turning on their TVs and air conditioners.

Balancing customer loads with ever-increasing amounts of renewable energy has been a well-known challenge for utilities. The growing penetration of residential PV is further complicating matters. On Maui, wind farm developer First Wind did not expect the level of curtailment faced by its project. In part, the level of curtailment was caused by individual customers installing PV systems on their residences to such a degree that they shifted the balance between the utility’s traditional generation and renewable generation on the island.

So even as utilities and renewable energy developers may like to plan how much renewable generation is built and where it is placed, the continuing price drop in solar installations is resulting in individual customers becoming a factor in this calculation. And because residential PV generation generally can’t be curtailed, the impact of these installations will begin to affect large utility-scale renewable generation, which can be curtailed.

Although renewable energy curtailment on an isolated island grid may not be applicable to the rest of the U.S. power grid today, the continued penetration of utility-scale wind and solar plants, combined with the steady drop in price of residential PV systems, may make this a factor in many parts of the world in just a few years. If we are to encourage the continued growth of renewable energy installations at the utility, community, and residential levels, we must push for technologies such as battery energy storage to act as a buffer between our electricity use and the variability of renewable generation.

I’d be interested in learning your thoughts on these issues. Do you agree?


Erik Svanholm

Publication Date

June 1, 2016