Estimating future costs of hydrogen as long-duration energy storage based on a learning rate approach

Techno-economic analysis of long-duration energy storage and flexible power generation technologies to support high-variable renewable energy grids

The Value of Inter-Regional Coordination and Transmission in Decarbonizing the US Electricity System

Evaluating and improving technologies for energy storage and backup power

The curtailment paradox in the transition to high solar power systems

The energy transition from fossil fuels to clean energy is inevitable to limit climate change. Pumped storage hydropower can compensate for the balancing of load, provides various ancillary services, and integrates variable renewable energy in the grid. However, uncertainties such as market structure, long-term natural gas prices, variable renewable energy penetration, government incentives, and regulatory policy, making it difficult to develop a viable business case for new pumped storage hydropower project. This research article considers improving financial viability of new pumped storage hydropower project by reducing upfront capital cost by utilizing existing conventional hydropower resources and reducing pumping/charging costs by finding a potential site where a water stream reaches the upper reservoir directly. The fast-track, cost-effective, and environmentally friendly approach investigates the true potential of this configuration for the case study of 200 MW Paras pumped storage hydropower with integrated 300 MW Balakot conventional hydropower. The article considers numerous scenarios for both closed-loop and open-loop pumped storage hydropower and calculates the levelized cost of energy storage for all scenarios. The conclusion is that utilizing existing conventional hydropower resources and considering water stream entering directly into the upper reservoir decreases the overall levelized cost of energy storage from 13.73 to 11.77 US$ cents/kWh (14% decrease). Results of the levelized cost of energy storage can help experts, regulators, power producers, and investors realize the importance of pumped storage hydropower as a reliable, cost-effective, and sustainable energy storage technology to integrate variable renewable energy.

As the proportion of grid-connected variable renewable energy (VRE), mainly wind and solar photovoltaic (PV), getting higher, the demand for flexibility in the power system increases intensely, posing unprecedented challenges to the economic and stable operation of the power system. In order to meet the growing flexibility needs, new technologies such as rapid grade climbing and highly flexible combined cycle gas turbine power generation will be required on the power supply side, as well as new technologies such as energy storages. In addition, the expansion of trans-regional power transmission capacity will be another important source of power system flexibility. Together, these technologies have created huge opportunities to help the power system to integrate more VRE. In this study, a practical framework study for flexibility assessment and its allocation was proposed to investigate the flexibility demand change with high penetration of VRE in the power system. By focusing on the various flexible resources available, an optimal portfolio of flexibility solutions to facilitate VRE integration is studied. The study also explores especially the potential of extend grid interconnection as a flexible resource to make the power system more economical and low carbon.

Towards robust and scalable dispatch modeling of long-duration energy storage

The role of electricity market design for energy storage in cost-efficient decarbonization

Sustainable and cost-effective hybrid energy solution for arid regions: Floating solar photovoltaic with integrated pumped storage and conventional hydropower

The full decarbonization of electric grids, as planned by the European Union and other Administrations for 2050, calls for energy storage (ES) systems capable of discharging at full power over periods longer than 4-5 hours, which is the typical duration of internal storage batteries such as Li-ion and Sa-X. Such long discharge periods are already in the capability of some energy storage technologies, notably pumped-hydro (PH) ES, which was introduced at the beginning of the 20th century and today accounts worldwide for 165 GW of power capacity and 1.6 TWh of energy storage, corresponding to 96% and 99% of the global storage figures, respectively. However, a major increase in ES demand is expected in the coming decades heading to 1.25 TW and 5 TWh by 2050, which cannot be covered by PH, due to geomorphological, environmental, and technical constraints. While conventional batteries (e.g. Li-ion, Na-ion) will continue to expand to face the growing demand for fast energy storage, the increasing request for Long Duration Energy Storage will rely on other technologies and Flow Batteries are emerging as strong candidates for taking over an important share.They are presently investigated and developed in over 50 different chemistries which range from low-medium to high Technological Readiness Level (TRL). The former include still technologically immature systems typically studied at laboratory level in small single cells (1–101 W) for characterizing materials, not systems. Research is focused on some chemistries based on non-critical materials, among which: Copper-Copper, Polysulfide-Bromine, Iron-Chromium, Zinc-Cerium, Organic compounds: Quinone, Viologen, TEMPO, Polymers of various nature, and Lithium-ion flow and some larger pilot systems have been made (102 kW) but related data is often classified or not accessible. The high TRL types are often already produced and marketed, even in very large sizes (10 kW–102 MW and 10 kWh–102 MWh) using chemistries such as: Vanadium-Vanadium, Zinc-Bromine, Iron-Iron, Hydrogen-Bromine. Although the all-vanadium type exhibits the best performance, it raises geopolitical issues due to the strong localization of ore reserves which make this metal a critical raw material (CRM), e.g. in the European Union. In this scenario the research on some iron-complex-based FBs is taking momentum due to wide accessibly and low cost of the metal, despite performance still call for major improvements. Techno-economic analyses and forecasts using tools such as the levelized cost of storage (LCOS) and the net present value (NPV) can provide important insight in addressing strategically the developing research. References EASE, Energy Storage - Targets 2030 and 2050, EASE Report, Reports and Studies, June 2022.Jeremy Twitchell, Kyle DeSomber, and Dhruv Bhatnagar. Defining long duration energy storage. J. Energy Storage, 60 (2023):105787.McKinsey & Company, Net-zero power – Long duration energy storage for a renewable grid, McKinsey & Company Report, November 2022.Böhmer, C. Fenske, C. Lorenz, M. Westbroek. Long-duration energy storage - Regulatory environment and business models in Germany, Spain, France, Italy, and Great Britain. Report created for SPRIND GmbH, Aurora Energy, June 2023Search.J. Guerra, J. Zhang, J. Eichman, P. Denholm, J. Kurtz, B.-M. Hodge, The value of seasonal energy storage technologies for the integration of wind and solar power, Energy Environ. Sci., 13 (7), (2020), 1909–1922. DOI: 10.1039/d0ee00771d.A. Hunter, M.M. Penev, E.P. Reznicek, J. Eichman, N. Rustagi, S.F. Baldwin, Techno-economic analysis of long-duration energy storage and flexible power generation technologies to support high-variable renewable energy grids, Joule, 5 (2021) 2077–2101. Doi: 10.1016/j.joule.2021.06.018.A. Dowling, K.Z. Rinaldi, T.H. Ruggles, S.J. Davis, M. Yuan, F. Tong, N.S. Lewis, K. Caldeira, Role of Long-Duration Energy Storage, in Variable Renewable Electricity Systems, Joule, 4 (2020), 1907–1928.Albertus, J.S. Manser, S. Litzelman, Long-Duration Electricity Storage Applications, Economics, and Technologies Joule, 4 (1), (2020), 21 - 32, DOI: 10.1016/j.joule.2019.11.009.Sanchez-Diez, E. Ventosa, M. Guarnieri, A. Trovò, C. Flox, R. Marcilla, F. Soavi, P. Mazur, E. Aranzabe, R. Ferret, “Redox flow batteries: status and perspective towards sustainable stationary energy storage”, J. Power Sources, 481, (2021) 228804. doi: 10.1016/j.jpowsour.2020.228804.Poli, C. Bonaldo, M. Moretto, M. Guarnieri. Techno-economic assessment of industrial Vanadium Flow Batteries based on experimental data, Appl. Energy, 362 (2024) 122954. DOI: 10.1016/j.apenergy.2024.122954.A. Kurilovich, A. Trovò, M. Pugach, K.J. Stevenson, M. Guarnieri, “Prospect of modeling industrial scale flow batteries – From experimental data to accurate overpotential identification,” Renew. Sustain. Energy Rev., 167 (2022) 112559. doi: 10.1016/j.rser.2022.112559.

Author(s): Gerke, Brian; Gallo, Giulia; Smith, Sarah; Liu, Jingjing; Alstone, Peter; Raghavan, Shuba; Schwartz, Peter; Piette, Mary Ann; Yin, Rongxin; Stensson, Sofia | Abstract: In response to the imperative of the climate crisis, California is in the midst of deployment of low-carbon energy generation and electrified heating and transportation at a rapid pace. In 2018 the grid managed by the California Independent System Operator (CAISO) was already generating 26 percent of its power from non-hydro renewable sources, with an additional ten percent hydroelectric power; and with SB 100, California statute now sets a target of 100 percent carbon free electricity by 2045. Maintaining this fast pace of decarbonization requires action across multiple domains on the grid from generators to loads. This study describes new findings on the scale of the opportunity for enabling load shifting as a form of demand response (DR) in California, as part of this renewable energy transition. We use the shorthand term Shift to refer to this potential load-shifting DR resource. The operating principles for the electric power system mean that achieving California’s renewable energy goals requires careful planning to build and operate the system in a way that maintains reliability at low cost. The most fundamental of these principles is that generation and demand need to be balanced at all times. Historically this has meant building adequate flexible and dispatchable generators that can be operated to match inflexible and uncontrolled loads. Meeting large fractions of demand with variable renewable energy (VRE) generation introduces a new paradigm, exemplified by the “duck curve” in California. In the times of year it occurs, the duck curve illustrates the net electricity demand that must be met by non-VRE generation; it has sharp peaks in morning and evening (the “tail” and “head” of the duck, respectively) and steep transitions to a deep midday trough (the duck’s “belly”) resulting from solar generation. Balancing the duck curve is a key priority for integrating increasing levels of VRE on the California grid. Shift DR is one of several renewables integration planning approaches that can work together to balance a high-VRE system. Others include “overbuilding” renewable energy with the intent to curtail during times of surplus generation, building and operating transmission lines to integrate regional systems, and building and operating energy storage to match generation with loads. Based on the 2019-2020 Integrated Resource Planning (IRP) model for California1—which did not consider Shift among its resource options—the least-cost pathway for achieving California GHG goals includes all of these other approaches. The Reference System Portfolio that is used to inform utility planning includes development of energy storage that is operated to serve about 10 GWh of consumption on the average day in 2020, 70 GWh in 2030, and 400 GWh by 2045. There is also significant curtailment of VRE in this least-cost portfolio, with 4 GWh on the average day in 2020, rising to 15 GWh by 2030 and 100 GWh by 2045. Throughout this report we compare the Shift resource to curtailment and storage as benchmarks, providing context for the results we report related to the quantity, cost, and performance of Shift. The timing of evening peak and curtailment defines times when load shifting is most valuable and would likely be used. The quantity of curtailment and use of storage to balance the system represent how much Shift could be valuable at the upper bound if Shift is inexpensive. The cost of energy storage is also a useful benchmark for the cost of Shift because it is the most comparable “competing” technology option; we therefore use the cost of storage to set a reference price level below which Shift will be most broadly cost competitive.

Mitigating Curtailment and Carbon Emissions through Load Migration between Data Centers

The annual retirement of U.S. coal-fired electricity generation units (CF-EGU) is at an all-time high and is expected to continue. This loss of reliable baseload generation, combined with predicted growth of variable renewable energy (VRE) generation, is expected to stress grid reliability as the number of load-following resources drops below the experienced load variability. Many regions are already experiencing challenges, and fossil retirement-related warnings by the North American Electric Reliability Corp. are becoming more dire. All CF-EGU retirements pose significant challenges to asset owners, local workforces, and their communities. Repurposing a retiring CF-EGU as a long-duration energy storage plant can address these challenges and offer a suite of additional benefits to asset owners, the grid, and society. This project performed a techno-economic evaluation and assessment of repurposing a Duke Energy fossil-fueled asset (in particular, a coal plant) into an energy storage system by integrating the retiring asset with a Malta long duration Pumped Heat Energy Storage (PHES) system. The project validated the technoeconomic benefits of repurposing retiring coal plants into long-duration energy storage using Malta’s PHES. Key findings for this project are summarized below: Technical Retiring coal plants (and other steam turbine fossil generation) can be repurposed to enable the clean energy transition using Malta’s technology. For older retiring coal plants, repurposing the site and electrical interconnection for a standalone PHES plant is the most economically favorable option. For newer coal plants where there is also a local peaking capacity need, repowering the steam cycle into a hybrid integration with PHES is attractive. A process was developed to assist fossil generation owners in choosing the best path for each plant’s circumstances. Economic Communities facing economic challenges caused by the retirement of fossil generation would benefit from repurposing the plant as long-duration energy storage using Malta’s PHES. On a $/MW basis, repowering retiring coal units into Malta PHES plants can maintain the same number and types of jobs and economic activity. For a 70% carbon reduction scenario, a 10-hour Malta PHES plant is more economic for the asset owner than similar-power 4-hour batteries. This project showed that repurposing a retiring coal unit into thermal energy storage, by integrating it with a Malta PHES system, makes techno-economic sense. At least two integration options are available, with the optimal solution depending on the coal plant and its location. Repurposing retiring coal plant into energy storage results in economic benefits for the plant owner and local communities.

Purpose of ReviewSignificant and mainly unpredicted advances in variable renewable energy technologies are resulting in structural shifts in energy systems globally causing an energy revolution. This review focuses on the implications for developing countries including the water-energy nexus.Recent FindingsDeveloping countries typically feature promising endowments in renewable resources, rapidly growing demand, and a relative lack of legacy generation systems. With the costs of wind and solar dipping below their non-renewable competitors, developing countries are potentially positioned for rapid uptake of variable renewable energy systems. The South African case provides an example of strong renewable energy endowments, illustrates the benefits of detailed energy analysis for exploitation of these endowments, and shows that this combination can lead to high variable renewable energy penetration in the least cost energy mix. The energy-water nexus is highly likely to be strongly influenced by this energy revolution. For example, hydropower has the capability to play an important role in load balancing; however, it is not clear that the necessary transmission infrastructure, institutions, and international cooperation will emerge of this potential role of hydro and adjudicate across competing demands for water. Decisions in the traditional water and energy sectors are still often taken in isolation.SummaryOverall, the technological advances provide a valuable opportunity for enhancing growth and development prospects in developing countries while meeting environmental objectives at global and local scales. The implications for the energy-water nexus are frequently unclear, as planning decisions around energy and water investments are traditionally taken without using an integrated approach. Accelerated research efforts and fresh thinking to integrate modeling and planning around the supply of water and energy are key to realizing the potentials inherent in the ongoing energy revolution.

With the increasing expansion of renewables, energy storage plays a more significant role in balancing the contradiction between energy supply and demand over both short and long time scales. However, the current energy storage planning scheme ignores the coordination of different energy storage over different time scales in the planning. This paper forces the unified energy storage planning scheme considering a multi-time scale at the city level. The battery energy storage, pumped hydro storage and hydrogen energy storage are considered to meet the power balance on the daily scale, monthly scale and annual scale. To minimize the total cost of energy storage, the capacity and outputs of energy storage are determined. With unified storage models, mixed-integer programming is applied to integrate the multiple time scale storage operation in the planning. The proposed planning scheme considers the trade-off between the flexibility and the cost of different types of energy storage. The results show that pumped hydro storage can undertake a large amount of power contradiction. The battery energy storage and the hydrogen energy storage meet the short-term and long-term energy imbalance respectively.