Market Insights

Long-Duration Energy Storage as a Necessity for Reliable Decarbonized Grids

June 15, 2023 by Claire Turvill

Pacific Northwest National Laboratory research underscores the vital role of long-duration energy storage in achieving decarbonized grids.

Timely planning is crucial for U.S. states aiming to achieve aggressive decarbonization goals while aligning with federal decarbonization objectives to ensure a reliable energy supply. That is according to recent Pacific Northwest National Laboratory (PNNL) research.  



PNNL. Image used courtesy of Ian Roberts (Borgendorf) Wikimedia Commons


One promising solution to meet these requirements is long-duration energy storage (LDES). These extensive energy storage systems can effectively store renewable energy until it is required, presenting a vital opportunity for establishing a dependable and decarbonized power grid. However, proactive planning must be the top priority to be an effective solution.


Long-Duration Energy Storage

The scaling of extended or long-duration energy storage systems to support future grids currently lacks an exact definition. However, the growth of such systems can be projected by identifying gaps in renewable energy performance within a decarbonized grid.

The increasing presence of variable generation resources results in a discrepancy between electricity generation and consumption. The supply and demand imbalance becomes more prominent as the grid’s variable generation capacity expands. 

“Defining Long Duration Energy Storage,” the report from PNNL published by Senior Energy Analyst Jeremy Twitchell and Waterpower Advisor Kyle DeSomber, examines the current applications of energy storage and how they are evolving in response to emerging grid requirements. It evaluates how the power generation industry and academia are establishing a framework for defining long-duration storage and coordinating research endeavors to advance commercial technologies in the field. 

The authors emphasize that the challenges posed by a decarbonized grid connote be easily resolved as in the past. While energy efficiency, demand response, and overbuilding generation capacity are part of the solution, the scale of imbalances between energy supply and demand in a decarbonized grid surpasses the capabilities of these approaches.

The report analyzes the changing availability of variable energy sources like wind and solar, proposes new definitions for LDES, and illustrates potential future energy shortages using California as an example.


Decarbonization Goals

It is becoming increasingly clear that a decarbonized grid is a realistic future scenario. The Biden administration has released a federal goal of achieving a 100% clean electricity grid by 2035. Many states and territories have supported this goal with their own requirements for 100% clean or net-zero energy.

To support a decarbonized grid, energy storage systems provide grid operators with greater control and flexibility to balance supply and demand. Renewable energy is inherently volatile, with generation fluctuations based on weather conditions. 


Renewable energy

Renewable energy. Image used courtesy of Pixabay

LDES enables electricity to be stored and utilized over extended periods, allowing grid operators to adapt more effectively to evolving customer demands, climate variations, extreme weather events, and seasonal fluctuations.

LDES serves a vital role in maintaining a reliable and sustainable energy supply.


Defining Long-Duration Energy Storage

There is currently a broad range of definitions for LDES, spanning from 10 to 100 hours. To provide more clarity and specificity, the researchers propose adopting two distinct classes of LDES. 

The first class, called diurnal storage, lasts up to 20 hours and is designed to address daily cycles of surplus and deficit in energy generation. This class focuses on reconciling the imbalances that occur within 24 hours.

The second class, known as seasonal storage, tackles the challenges arising from seasonal variations in power generation. It aims to bridge the gap between periods of surplus generation and when there is insufficient generation capacity during different seasons.

By categorizing long-duration energy storage into these two classes, utility companies and grid planners can leverage historical load data to more accurately determine the required duration of "stop gap" energy storage. This approach enables more precise planning and implementation of long-duration energy storage systems to meet specific grid requirements.


Supply and Demand Imbalances

The research uses California as an example for portraying existing imbalances in supply and demand from variable generation. 

The researchers developed a model showcasing energy deficiencies using California Independent System Operator data. The example discovered a deficit of 30 gigawatts of capacity in a single day, which accounts for roughly half of California’s total daily generation. The state would require 15 Hoover Dams worth of energy generation for the same period to compensate for this shortfall. 

The study observed that energy consumption peaks during the morning hours from 5 to 8 AM and in the evening after 5 PM. During the day, solar energy generation can support meeting energy demand. However, solar energy production declines significantly from 5 to 8 PM, leading to an energy shortfall when demand is highest at 6 PM.

Having reliable access to LDES would help California manage the evening supply shortfalls.


Decarbonized Grid

Federal and state goals require about 34 percent of national electricity consumption to be from clean energy sources by 2050; this percentage will increase if more states commit to clean energy goals. 

To reach this consumption goal, clean energy generation must increase by about 50 percent by 2050. 

Successfully integrating variable generation into the grid while maintaining a reliable power supply is expected to be a substantial challenge. 

Numerous studies indicate the cost benefits of LDES for operating a fully decarbonized grid. The PNNL study emphasizes these benefits but further stresses that LDES is quickly becoming essential to ensure grid reliability moving forward. 

The industry and research communities are united in addressing this challenge, with individuals like Julia Souder leading the way. Souder serves as the CEO of the Long Duration Energy Storage Council, a global non-profit organization dedicated to expediting the decarbonization process worldwide by promoting the advancement of long-duration energy storage technologies.

The primary objective of the PNNL paper and research, according to Twitchell, was to emphasize the critical importance of LDES in a decarbonized grid. To ensure its availability when required, it is essential to send clear market signals that encourage current research and development of LDES technologies. 

Developing such technologies takes considerable time, but energy planning and procurement processes typically operate on short cycles of less than three years. Without proactive measures, by the time these processes identify the need for LDES, there may not be sufficient time for their development and deployment.