Long-duration energy storage for reliable renewable electricity: The realistic possibilities
Jacqueline A. Dowling and Nathan S. Lewis.
Portfolios all the way down...
Ken Caldeira and Jacqueline A. Dowling.
The role of concentrated solar power with thermal energy storage in least-cost highly reliable electricity systems fully powered by variable renewable energy
Kathleen M. Kennedy, Tyler H. Ruggles, Katherine Z. Rinaldi, Jacqueline A. Dowling, Lei Duan, Ken Caldeira, Nathan S. Lewis.
Opportunities for flexible electricity loads such as hydrogen production from curtailed generation
Tyler H. Ruggles, Jacqueline A. Dowling, Nathan S. Lewis, Ken Caldeira.
Wind and solar resource droughts in California highlight the benefits of long-term storage and integration with the Western Interconnect.
Katherine Z. Rinaldi, Jacqueline A. Dowling, Tyler H. Ruggles, Ken Caldeira, Nathan S. Lewis.
Chapter 5.1 of America's Zero-Carbon Action Plan 2020 report: Accelerating Deep Decarbonization in the U.S. Power Sector.
Chris Castro, Jacqueline A. Dowling, Payman Dehghanian, Emre Gençer, Daniel Kammen, Jeffrey Logan, Meagan Mauter, Brian Tarroja, Gernot Wagner
Would firm generators facilitate or deter
variable renewable energy in a carbon-free electricity system?
Mengyao Yuan, Fan Tong, Lei Duan, Jacqueline A. Dowling, Steven J. Davis, Nathan S. Lewis, and Ken Caldeira
Molecular diversity of sea spray aerosol particles: Impact of ocean biology on particle composition and hygroscopicity.
Richard E.Cochran, [...], Jacqueline A. Dowling, [...], Kimberly A. Prather, and Vicki H. Grassian
Heterogeneous chemistry of lipopolysaccharides with gas-phase nitric acid: Reactive sites and reaction pathways.
Jonathan V. Trueblood, Armando D. Estillore, Christopher Lee, Jacqueline A. Dowling, Kimberly A. Prather, and Vicki H. Grassian
Hydrogen energy storage, despite low efficiency, has the potential to reduce costs of deeply decarbonized electricity systems. Long-duration energy storage technologies may improve the affordability of reliable wind- and solar-based electricity systems. Power-to-gas-to-power (PGP) with hydrogen fuel is a long-term energy storage technology that has historically been discounted, in part because of its low round- trip efficiency. However, our results show that with currently available technology, PGP may be able to reduce costs of deeply decarbonized wind-solar-battery systems. Here, we use historical U.S. weather data and a macro-scale energy model to evaluate capacities and dispatch in least- cost, reliable electricity systems. We investigate which innovations in PGP (including hydrogen storage and energy conversion technologies) would most improve system-wide electricity costs, and which innovations are less important. We find that incremental reductions in conversion-related capital costs affect total system costs more than incremental improvements in round-trip efficiency (Figure). When electricity from natural gas is restricted to 10 - 15% of total dispatch, PGP with underground storage can play a substantial role in the system. Even when natural gas is unrestricted, there may still be a small market for PGP with hydrogen combustion turbines. Repurposing depleted natural gas reservoirs for hydrogen storage may facilitate PGP at scale in the U.S. Despite low efficiencies and theoretical increased leakage rates, PGP remains valuable to the system as long-duration energy storage. With substantial penetration of variable renewables like wind and solar, there is often the potential for electricity generation that exceeds demand, resulting in zero-cost electricity. Because efficient use of zero-cost electricity does not influence the cost of electricity produced from stored hydrogen, the system benefits of PGP are more sensitive to the cost of conversion than to the efficiency of conversion.
Reliable wind and solar electricity systems can be made more affordable by the addition of long-duration hydrogen energy storage. Carbon-free electricity can drive water electrolysis to generate green hydrogen for use on demand. Proton exchange membrane (PEM) electrolyzers are better suited than alkaline-based technologies to meet ramping needs of intermittent renewable electricity. Commercial PEM electrolyzers utilize iridium-based catalysts to drive water oxidation in acid that could become a bottleneck for the scale-up of PEM electrolyzers due to the low abundance of iridium. Iridium exhibits high activity for the oxygen evolution reaction (OER), but corrodes in acid and degrades over time. Earth abundant metal antimonates, in particular MnSbOx, have demonstrated electrocatalysis of the OER with promising activity and stability. These earth-abundant electrocatalysts can be used to supply electrons needed to drive several different cathodic fuel-forming reactions including the production of hydrogen, hydrocarbons, or ammonia. Previous analysis has indicated that a 70:30 Mn:Sb composition by metal fraction may provide the best combination of activity and stability. Long-term activity and stability has only been evaluated via a constant current stress test for other compositions of MnSbOx generated via sputter deposition. Electrochemical activity and stability have yet to be evaluated for other MnSbOx synthesis methods. The long-term activity and stability of MnSbOx catalysts synthesized via two new methods in addition to sputtering, chemical vapor deposition (CVD) and solid-state synthesis, was evaluated. Electrochemical activity of the catalysts were evaluated over a weeklong period where 10 mA cm-2 was demanded galvanostatically in 1 M H2SO4 electrolyte. Stability was assessed by quantifying corrosion products over time via inductively coupled plasma mass spectrometry (ICP-MS). We compare the long-term activity and stability of the various synthesis methods. Different synthetic methods may lend themselves to a variety of industrial uses and applications such as PEM membrane electrode assemblies (MEA). In the catalyst layer of PEM-MEAs, CVD thin films can be used to coat high-surface-area carbon supports, and catalyst powder inks can be hot-pressed into Nafion membranes.
Variability of wind and solar generation and electricity demand poses substantial challenges to the affordable supply of reliable electricity. Energy storage technologies with different discharge durations may coexist within energy systems to provide storage on different timescales. Vanadium redox flow batteries and Form Energy’s iron-air battery have been built to 10 - and 100 - hour durations, respectively. However, these technologies could be built to different durations if needed. In a stylized setting, we evaluate optimal durations given current and projected future costs. We simulate a reliable electricity system based on multiple years of historical U.S. weather and demand data. In this configuration of our macro-energy model, gaps between wind and solar generation and electricity demand may be balanced by three types of energy storage: short- duration ( < 10 hour; Li-ion batteries), long-duration ( > 100 hour; power-to-gas-to-power, PGP, with hydrogen fuel), and a theoretical redox flow battery with parameterized energy capacity costs. Results indicate that when redox flow battery energy costs are between about 3 and 50 $/kWh, optimized durations are between 10 and 100 h, acting as a mid-duration storage technology (Figure 1). If PGP and Li-ion energy storage are present, the optimized duration of Vanadium and Iron-air batteries at current costs is 1.5 and 22 hours respectively—much lower than current projects. Only two storage technologies were deployed in the vast majority of highly reliable and least- cost optimized systems. When mid-duration storage is present, it displaces short-duration storage, but not the need for long-duration storage. It is theoretically possible for an infinite number of finely tuned batteries to compete in an environment with perfect information. Nevertheless, our results suggest that for a system with demand met by wind and solar generation, there are two dominant energy storage niches: one technologically and cost- advantaged for power capacity and the other for energy capacity.