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| Fig. 1: Low-Emission Hybrid Lithium-Ion Battery Storage (Source: Wikimedia Commons) |
The majority of human-induced carbon dioxide emissions come from fossil fuels, which service approximately 80% of global primary energy demand. [1] Climate change necessitates a transition to a low-carbon energy resources, which has accelerated the use of renewable energy sources such as wind and solar. As wind and solar are intermittent energy sources, the mismatch between spotty production and demand load is an increasingly difficult issue to resolve. Flexibility such as variable generation, demand-side management, and grid expansion can support the reduction of unbalanced production and demand. [1]
Lithium-ion batteries ("li-ion") have thus far enabled the enhancement of portable information and communication technologies. Indeed, li-ion batteries have powered the widespread use of laptop and tablet computers and cellular telephones over the last three decades. Among several prevailing battery technologies, li-ion batteries demonstrate high energy efficiency, long cycle life, and high energy density. Efforts to mitigate the frequent, costly, and catastrophic impacts of climate change can greatly benefit from the uptake of batteries as energy storage systems (see Fig. 1). For a stable energy supply with high shares of intermittent renewable energy sources, large-scale energy storage for short and long durations is an increasingly feasible option. [1] Lithium-ion batteries particularly offer the potential to 1) transform electricity grids, 2) accelerate the deployment of intermittent renewable solar and wind generation, 3) improve time-shifting of energy generation and demand, and 4) facilitate a transition from central to distributed energy services. [2]
A pathway for using lithium in room-temperature rechargeable batteries was established in the early 1970s, upon the discovery that electrochemical intercalation of guest molecules into layered hosts could also be used to store and release energy in battery electrodes. [2] Li-ion batteries have been commercially introduced by Sony since the early 1990s and have been developed as one of the most important battery technologies dominating the market. [3] Li-ion batteries are by far the best-performing rechargeable battery technology in terms of energy density developed to date, and its energy density continues to be improved at a rate of 5-10% annually. [2] There has been a growing trend towards next-generation lithium-ion batteries with high charge capacities/power densities developed for electric vehicles (EVs), hybrid electric vehicles (HEVs), aerospace applications, and autonomous electric devices. [4]
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| Fig. 2: Renewable Electricity Energy Sources (Source: Wikimedia Commons) |
In light of climate change-related risks and the rise of renewable energy, energy storage is especially important and attractive, especially grid-scale electrical energy storage (see Fig. 2). Adoption of intermittent energy generation sources (e.g., solar and wind) often leads to producing more energy than can be used at one time, which is referred to as over-generation. This leads operators to curtail PV generation, reducing both its economic and environmental benefits. The instantaneous demand for electrical energy and unpredictable daily and seasonal variations of demand pose serious challenges to grid networks during energy generation, transmission, and distribution. [3] An energy storage system can balance the load and power of a grid network by charging and discharging to provide regulated power to the grid with a fast response time. [3] The energy storage system can also help establish a sustainable and low-carbon electric pattern that is achieved using intermittent renewable energy. [3] Electric batteries exhibit considerable potential for application to grid-level electrical energy storage because of their attractive features, such as flexible installation, modularization, rapid response, and short construction cycles. [3] Li-ion batteries have an energy density of up to 200 Wh/kg and 3000 cycles at deep discharge of 80%. [3]
Li-ion batteries have the potential to increase the efficiency, lifespan, and reliability of alternative systems such as off grid photovoltaic and wind power that currently almost exclusively use lead-acid. [5] To have better market updates in grid-scale energy storage applications, the relatively high cost of li-ion batteries for vehicles is one of the main parameters to adjust in order to make the technology more competitive despite its incomparable advantages over lead acid, NiCd, and NiMH batteries. [5] Through the development of parallel sectors such as the automobile industry, decreasing usage cost will boost the application of li-ion batteries to grid- scale energy storage. [5]
Research projects that mid-range costs for lithium-ion batteries will fall an additional 45 percent between 2018 and 2030, after already having dropped 70 percent between 2015 and 2018. [6] Price reductions to date have largely been enabled by advances in power capacity and duration of energy discharge. Many of the price reductions are spillovers from the auto industry's race to build smaller, cheaper, and more powerful lithium-ion batteries for electric cars. In the U.S., energy storage costs have also been helped by the federal investment tax credit, which translates to a heightened cost of operating gas plants as more solar energy enters the grid. [7] Batteries are beginning to reach a size of around 200 megawatts that enables renewables to replace small- to medium-sized natural gas generators. [7] Research further suggests that li-ion batteries may allow for 23% CO2 emissions reductions. With low-cost storage, energy storage systems can direct energy into the grid and absorb fluctuations caused by a mismatch in supply and demand throughout the day. Research finds that energy storage capacity costs below a roughly $20/kWh target would allow a wind-solar mix to provide cost-competitive base load electricity in resource-abundant locations. [8] Presently, the average cost of a li-ion battery pack is about $137 per kilowatt hour. [9] Although li- ion batteries outperform other battery alternatives on the basis of performance, further decreasing the cost of li-ion batteries and exploring novel battery technologies remain key constraints and challenges for the future of grid- scale electricity storage.
© Danny Valdez. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] M. Schimpe et al., "Energy Efficiency Evaluation of a Stationary Lithium-Ion Battery Container Storage System via Electro-Thermal Modeling and Detailed Component Analysis," Appl. Energy 210, 211 (2018).
[2] G. Crabtree, E. Kócs, and L. Trahey, "The Energy-Storage Frontier: Lithium-Ion Batteries and Beyond," MRS Bull. 40, 1067 (2015).
[3] T. Chen et al., "Applications of Lithium-Ion Batteries in Grid-Scale Energy Storage Systems," Trans. Tianjin Univ. 26, 208 (2020).
[4] T. Kim et al., "Lithium-Ion Batteries: Outlook on Present, Future, and Hybridized Technologies," J. Mater. Chem. A, 7, 2942 (2019).
[5] B. Diouf, and R. Pode, "Potential of Lithium-Ion Batteries in Renewable Energy," Renew. Energy 76, 375 (2015).
[6] W. Cole and A. W. Frazier, "Cost Projections for Utility-Scale Battery Storage," U.S. Renewable Energy Laboratory, NREL/TP-6A20-73222, June 2019.
[7] C. Katz, "The Batteries That Could Make Fossil Fuels Obsolete," BBC, 17 Dec 20.
[8] M. S. Ziegler et al., "Storage Requirements and Costs of Shaping Renewable Energy Toward Grid Decarbonization," Joule 3, 2134 (2019).
[9] J. Frith, "EV Battery Prices Risk Reversing Downward Trend as Metals Surge," Bloomberg, 14 Sep 21.
