Future of Energy Storage on the Electric Grid

By Sophie Webster

Renewable energy is regarded as the solution to completely decarbonize the electrical grid, snuffing out use of fossil fuels like coal, oil, and natural gas to power our homes, schools, and businesses. Refashioning electric grids worldwide to incorporate renewables would prove both an environmental and economic boon: according to a report by the International Renewable Energy Agency (IRENA), a concerted investment in renewable energy, while initially costly, would yield a 200% return in global GDP and decrease carbon dioxide emissions by 70% by 2050 (IRENA, 2017). Moreover, these resources are abundantly available and scalable, making them propitious choices for many nations moving forward. Indeed, such an investment is necessary for G20 nations to steer the world toward the lofty yet essential goals outlined in the Paris Agreement: curbing global temperature rise.

However, the lynchpin in making renewables available and reliable when demand is high is proper energy storage integrated into the grid. Because renewable sources like wind and solar are beholden to natural cycles, subject to both some periodicity and some stochasticity, they are often not available when the highest demand is placed on the grid. This is embodied in the duck curve: solar energy peaks in availability at midday, but the highest demand is in mornings or evenings when strain on the grid spikes and the sun is not as strong (DOE, 2017). The evening ramp-up and potential for midday overgeneration create instability on the grid that storage would help to resolve. Ample storage on the grid could help to dispatch variable renewable energy when consumers most need it, not just when nature permits. Such flexibility can be engendered through several means, including balancing the load over large regions and increasing demand responsiveness. However, battery storage has become a solution of particular interest as lithium-ion (Li-ion) battery cost dropped precipitously in recent years, a triumph for which we have the automotive and consumer electronics industries to thank. Investment in battery storage also defrays the costs of capital-intensive electricity system assets (new utilities or transmission lines). This beneficial tradeoff, called ‘capacity deferral,’ is the primary source of battery storage’s value (Mallapragada, 2020).

Currently, storage is meagerly represented on the grid, mostly because it is not economical at the low penetration levels renewables have achieved thus far. Its current incarnations are pumped hydroelectric storage, compressed air energy storage, and vanadium redox flow batteries, with pumped hydro currently dominating the storage scene worldwide. This storage tactic leverages excess energy (often solar) to pump water into a high elevation reservoir, giving it the potential energy to later rush downward and spin the turbines, generating electricity (Duke Energy). However, despite being effective, pumped hydro is severely limited by long construction times and ecological concerns, never mind the topographic scarcity of landscapes that support it. Currently in lieu of storage, “peaker” plants (often natural gas-fired power) come online ad hoc to fill the need when demand soars. Battery storage could supplant this fossil-fuel dependency and help transition to a carbon-free grid.

In 2017, just over 700 MW of battery storage had been deployed in the US, mostly for regulating frequency (Mallapragada, 2020). While these numbers are a far cry from the 900 GW required to decarbonize the grid, the US and other nations are beginning to capitalize on decreased costs of utility-scale batteries (Dolsak and Prakash, 2021). California is poised to become the world leader in battery storage, with a 300-megawatt project about to make its debut and a 100-megawatt battery in progress. Other American states and nations are following in hot pursuit, with massive projects queued in South Florida, London, Lithuania, Saudi Arabia, and Chile in years to come. These developments were galvanized by ambitious sustainability goals and the plummeting costs of such batteries, which dropped 70% between 2015 and 2018. Moving forward, the US Renewable Energy Lab foresees midrange costs for Li-ion battery technology falling another 45% between 2018 and 2030. This freefall will usher in a massive uptick in battery storage on the grid, with experts predicting that global storage capacity will reach 1.2 TW in the next decade, with the US alone boasting a six-fold increase well before then (Katz, 2020). A recent report found that most fossil fuel power plants in the US will become defunct by 2035 (Grubert, 2020). This will be an impetus to propel industrial-scale storage into a reality, especially as renewables coupled with storage outcompete natural gas plants in economic viability and long-term structural integrity.

While battery storage has gained great traction in recent years, some experts caution against embracing it as a panacea for renewable integration. David Keith and Hossein Safaei’s 2015 assessment of bulk (multi-hour) energy storage found that it does not significantly ease the cost of cutting emissions. Their analysis favors, instead, lowering the capital costs of harnessing renewables and dispatchable low-carbon power. As mentioned before, gas currently flattens the peaks and valleys of intermittency because it is easily dispatchable (turned on and off swiftly). However, bulk storage will become increasingly important as we phase out natural gas and strive for zero emission solutions.

Sources:

“Confronting the Duck Curve: How to Address Over-Generation of Solar Energy.” Energy.Gov, 19 Oct. 2017, https://www.energy.gov/eere/articles/confronting-duck-curve-how-address-over-generation-solar-energy.

Dolsak, Nives, and Aseem Prakash. “Carbon-Free Electricity Requires Policies To Build And Finance Transmission And Storage.” Forbes, 21 Feb. 2021, https://www.forbes.com/sites/prakashdolsak/2021/02/21/carbon-free-electricity-requires-policies-to-build-and-finance-transmission-and-storage/?sh=22381166f048.

Grubert, Emily. “Fossil Electricity Retirement Deadlines for a Just Transition.” Science, vol. 370, no. 6521, Dec. 2020, p. 1171, doi:10.1126/science.abe0375.

IRENA. “Perspectives for the Energy Transition.” OECD/IEA, 2017, p. 204.

Katz, Cheryl. The Batteries That Could Make Fossil Fuels Obsolete. Dec. 2020, https://www.bbc.com/future/article/20201217-renewable-power-the-worlds-largest-battery.

Mallapragada, Dharik S, et al. “Long-Run System Value of Battery Energy Storage in Future Grids with Increasing Wind and Solar Generation.” Applied Energy, vol. 275, 2020, p. 115390.

“Pumped-Storage Plants - Hydro Energy.” Duke Energy, https://www.duke-energy.com/Energy-Education/How-Energy-Works/Pumped-Storage-Hydro-Plants. Accessed 19 Mar. 2021.

Safaei, Hossein, and David W. Keith. “How Much Bulk Energy Storage Is Needed to Decarbonize Electricity?” Energy & Environmental Science, vol. 8, no. 12, 2015, pp. 3409–17. DOI.org (Crossref), doi:10.1039/C5EE01452B.