You've Heard of Water Droughts. Could “Energy” Droughts Be Next?

The results, which Farnham published in his PhD thesis, weren’t a surprise. Farnham and Lall found that solar and wind potential, like rainfall, is highly variable based on the time of year and the place where wind turbines and solar panels have been sited. Across eight cities, they found that renewable energy potential rose and fell from the long-term average by as much as a third in some seasons.

“We coined the term ‘energy’ droughts since a 10-year cycle with this much variation from the long-term average would be seen as a major drought,” said Lall. “That was the beginning of the energy drought work.”

In the current study, Lall chose to zoom in on Texas, a state well-endowed with both sun and wind. Lall and Amonkar found that persistent renewable energy droughts could last as long as a year even if solar and wind generators were spread across the entire state. The conclusion, Lall said, is that renewables face a storage problem that can only realistically be solved by adding additional capacity or sources of energy.

“In a fully renewable world, we would need to develop nuclear fuel or hydrogen fuel, or carbon recycling, or add much more capacity for generating renewables, if we want to avoid burning fossil fuels,” he said.

In times of low rainfall, water managers keep fresh water flowing through the spigot by tapping municipal reservoirs or underground aquifers. Solar and wind energy systems have no equivalent backup. The batteries used to store excess solar and wind power on exceptionally bright and gusty days hold a charge for only a few hours, and at most, a few days. Hydropower plants provide a potential buffer, said Lall, but not for long enough to carry the system through an extended dry spell of intermittent sun and wind.

“We won’t solve the problem by building a larger network,” he said. “Electric grid operators have a target of 99.99% reliability while water managers strive for 90 percent reliability. You can see what a challenging game this will be for the energy industry, and just how valuable seasonal and longer forecasts could be.”  

In the next phase of research, Lall will work with Columbia Engineering professors Vijay Modi and Bolun Xu to see if they can predict both energy droughts and “floods,” when the system generates a surplus of renewables. Armed with these projections, they hope to predict the rise and fall of energy prices.

Kim Martineau is Director of Science and Technology Communications at Columbia University in the City of New York