NREL Study Compares Storage, Energy Efficiency Building Stock Benefits

by Peter Maloney
APPA News
November 4, 2021

Pairing energy efficiency, rather than energy storage, with a renewable energy portfolio is more cost effective at achieving 100 percent renewable power for the nation’s building stock, according to a new study from the National Renewable Energy Laboratory.

As more states, cities, and municipalities commit to reducing their environmental impact by shifting to 100 percent renewable energy sources, the dominant challenge will be the long-duration misalignment of supply and demand, Sammy Houssainy and William Livingood, the authors of the report, Optimal Strategies for a Cost-Effective and Reliable 100% Renewable Electrical Grid, argue.

While energy storage can address that misalignment, the report, published in the Journal of Renewable and Sustainable Energy, found that alternative and readily available solutions are more cost effective and should be considered first. “Minimizing long-duration storage is a key element in trying to achieve the target cost effectively,” Houssainy said in a statement.

Using a techno-economic analysis, the authors said they identified cost-optimal, region-dependent, supply-side, and demand-side strategies that reduce, and in some regions eliminate, the otherwise “substantial capacities and associated costs of long-duration energy storage.”

The supply-side strategies investigated included optimal mixes of renewable portfolios and oversized generation capacities. Demand-side strategies considered included building load flexibility and building energy efficiency investments.

The results, the author said, “reveal that building energy efficiency measures can reduce long-duration storage requirements at minimum total investment costs.”

Their analysis showed that a combination of optimally mixed renewable resources, oversized generation capacities, and building energy efficiency investments can eliminate the need for long-duration energy storage in some U.S. regions, the authors said. “This is particularly important given that most long-duration storage technologies are either geologically constrained or still underdeveloped,” they wrote.

The study analyzed prototype building models in climate zones represented by five cities – Tampa, Fla.; El Paso, Texas; New York, Denver, and International Falls, Minn. – and found that the optimum renewable mix generally favors higher wind power allocations in colder climates and higher solar photovoltaic allocations in hotter climates.

For example, the authors said, Tampa would generate all of its electricity from solar panels, while International Falls would receive 100 percent from wind turbines in order to have the least reliance on energy storage.

The report also modeled oversizing renewable generation sources as a means of reducing energy storage needs and found that it can reduce energy storage requirements by ensuring that loads are met during times of otherwise inadequate supply.

Even though oversizing may require curtailing excess power during periods of abundant supply, the authors said oversizing “can have substantial impacts on storage capacities, and in some cases potentially eliminating the need for storage.”

“Our results reveal that cost-optimal renewable production factor ranges from 1.4 to 3.2, and optimal energy efficiency penetrations range from 52% to 68% savings, depending on the climate region,” they wrote. “Therefore, the benefits of excess generation capacities and building energy efficiency measures are outweighed by their incremental investments.”