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California has ambitious goals for reducing and eliminating greenhouse gas emissions from the State’s electricity system as a cornerstone of efforts to decarbonize the State’s economy more broadly. Electricity decarbonization efforts are codified by Senate Bill (SB) 100 which seeks to have 100% of retail sales of electricity by the year 2045 provided by eligible zero-carbon resources with an interim target of 60% of retail sales of electricity provided by eligible renewable resources by the year 2030. This policy contributes to a broader goal of achieving economy-wide carbon neutrality in the State by 2045, codified by Executive Order B-55-18.Planning studies were undertaken to determine how California should proceed in terms of electricity generation and storage resource rollout to meet these goals, such as the Senate Bill 100 Joint Agency Report [1], which highlights the need for rapid renewable resource and energy storage buildout. Energy storage is typically selected as utility-scale lithium-ion batteries for short-duration storage and pumped hydropower energy storage for long-duration energy storage functions, primarily due to their relatively low cost for the former and technological maturity for the latter. Since the capacity expansion models used for such planning studies focus on minimizing cost, the recommended course from these studies focuses on lithium-ion and pumped hydropower energy storage connected as utility energy storage.In practice, however, energy storage deployment will not be dictated by a central plan. Energy storage is being deployed to serve different priorities. Behind-the-meter energy storage may be deployed by individual residential, commercial, and industrial customers to serve their specific needs, provide electricity savings, and enable higher uptake of local renewable resources. Energy storage may also be installed at wind or solar farms to enable these to act as more dispatchable resources for the electric grid and enable them to provide electricity to the grid when they would otherwise not be generating. Additionally, other energy storage technologies such as flow batteries and hydrogen energy storage are emerging as potential alternatives to lithium-ion batteries and pumped hydropower, each with its own advantages and disadvantages in terms of technical, economic, and practical (i.e. safety, recyclability, etc...) characteristics.Energy storage is a critical enabler of plans for complying with Senate Bill 100 and broader economy-wide decarbonization goals. Therefore, it is critical to understand the effect of alternative configurations for energy storage deployment on the broader electricity system’s ability to rely on zero-carbon electricity for meeting load, how well it can use available renewable electricity generation, and the system-wide cost of electricity.Therefore, the goal of this project is to provide information on the preferred configuration of energy storage technologies for supporting a decarbonized California electric grid by investigating alternative configurations for the buildout of energy storage to meet California’s electricity decarbonization goals and comparing them to the configuration suggested by Senate Bill 100 planning studies.

Energy storage systems are critical for enabling the environmental benefits associated with capturing renewable energy to displace fossil fuel-based generation, yet producing these systems also contributes to environmental impacts through their materials use and manufacturing. As energy storage capacity is scaled up to support increasingly renewable grids, the environmental benefits from their use may scale at different rates than the environmental impacts from their production. This implies the existence of capacity thresholds beyond which installing additional storage capacity may be environmentally detrimental. Identifying such thresholds are important for ensuring that energy storage capacity selection in future grids are consistent with net emissions reduction goals, but such thresholds have not been studied in the present literature. To identify such thresholds, here we combine electric grid dispatch modeling with life cycle analysis to compare how the emissions reductions from deploying three different flow battery energy storage types on a future California grid (>80% wind and solar) compare with emissions contributions from producing such batteries as total battery capacity installed on the grid increases. Depending on the type of battery and environmental impact indicator (greenhouse gas or particulate matter emissions), we find that the marginal environmental benefits of storage begin to diminish at deployed capacities of 38–76% of the mean daily renewable generation (256–512 GWh in our California scenarios) and reach zero at 105–284% of mean daily renewable generation (700–1810 GWh). Such storage capacities are conceivable, but upstream impacts of storage must be assessed in evaluating the environmental benefits of large-scale storage deployment, or they could negate the environmental benefits of regional electricity system decarbonization.

Climate change mitigation requires developing zero-carbon, highly renewable energy systems, which require technologies to capture excess renewable electricity such as energy storage. Endeavoring to capture all available excess renewable electricity, however, may require large energy storage capacities and costs. This study therefore investigates how much curtailment is cost-optimal to allow in developing fully decarbonized electricity systems, using compliance with California's Senate Bill 100 goal as a representative case study. We combine electric grid dispatch modeling with an optimization approach for selecting the composition of energy storage technologies to capture excess renewable electricity to minimize overall system costs. We found that overbuilding cheap wind and solar and allowing the curtailment of excess renewable electricity equivalent to 25–43% of the total annual electric load resulted in the lowest cumulative systemwide cost for a fully decarbonized electricity system of about $1.8 trillion, spent between 2020 and 2045. Allowing no renewable curtailment results in significant battery requirements and a cumulative systemwide cost of $5.2 trillion spent between 2020 and 2045. Therefore, allowing some curtailment reduced the cost of building a fully decarbonized electricity system by a factor of 3 when the portfolio of technologies to capture and manage excess renewable electricity is carefully chosen. • Examined cost-minimal renewable curtailment levels for a zero-carbon grid. • Assessed cost-optimal technology mixes for harnessing excess renewable electricity. • Overbuilding renewable capacity is cheaper than vastly expanding energy storage. • Long duration storage is critical to minimize costs to build a zero-carbon grid. • Power-to-gas is well suited for long duration storage alongside batteries. [ABSTRACT FROM AUTHOR]

Highlights • Zero-emissions transportation fueling is the most cost-effective use of excess renewable energy. • Energy storage provides limited emission reduction benefits on already low-carbon grids. • Renewable gas production provides limited emissions reduction but significant cost benefits. • Load flexibility is critical for maximizing the cost-effectiveness of emissions reduction options. Abstract Preventing the curtailment of excess renewable generation, caused by mismatches between variable renewable electricity generation and the electric load, is a key strategy for maximizing greenhouse gas emissions reductions by integrating renewable resources into the electric grid. Strategies to harness excess renewable generation for useful purposes exist, but it is unclear which of these end uses provides the most effective use of available excess generation to maximize greenhouse gas emissions reductions in a cost-effective manner. This study investigates and compares three end-use strategies for utilizing excess renewable generation – storage in electrical energy storage systems, production of transportation fuel or vehicle charging, or production of renewable gas – and their diverse technology pathways on the bases of their greenhouse gas emissions reduction potential and the impacts of their implementation on the cost of energy services. This is accomplished by modeling the integration of 46 different technology pathways for using excess renewable generation in a 70% renewable and an 80% renewable electric grid configuration during the year 2050 in California using the Holistic Grid Resource Integration and Deployment (HiGRID) platform, which is a temporally-resolved resource dispatch model of the electricity system. Technology and cost characteristics for batteries, hydrogen energy storage systems, vehicle fueling or charging, and renewable gas production technologies are collected from multiple sources and their effect on reducing greenhouse gas emissions and affecting the Levelized Cost of Energy (LCOE) services in the HiGRID platform are examined. It was discovered that using excess renewable generation to produce transportation fuel for hydrogen vehicles or to charge electric vehicles provided the largest total greenhouse gas emissions reductions and lowest per-ton cost of greenhouse gas reduction. Use in grid energy storage and production of renewable gas provided similar but relatively lower total greenhouse gas reductions than transportation, with the latter imposing lower per-ton costs of greenhouse gas reduction. More generally, greenhouse gas reduction potential of these end uses depended on the intensity of the fuel being displaced by renewables, while LCOE effects depended on the temporal flexibility of the technologies associated with this end use. Overall, this study provides insight into a priority order for directing the use of excess renewable generation towards end uses to achieve greenhouse gas reduction goals such as those in California in a cost-minimal manner, and investigates the sensitivities that influence the effectiveness of these end uses. [ABSTRACT FROM AUTHOR]

Different configurations of a 100% renewable electricity system are possible, but not all are equally desirable in terms of the scale of material resources required to sustain them. This study compares different approaches for developing a 100% renewable electricity system on the basis of the material mass investment required to sustain their physical components. Electric grid modeling accounting for operational constraints is used to determine the scale of energy technology capacities required to achieve a 100% renewable electricity system using California as a representative example and translating those requirements to material mass requirements. Using a wind/solar/storage approach requires exponentially growing capacities of energy storage to meet operational needs and requires significant material mass investments. Material resource efficiency of the system is shown to be improved by maximizing the use of regional non-variable renewables to the extent possible within local capacity constraints. Alternatively, overbuilding the wind and solar capacity in excess of that needed to meet annual demand is also shown to improve material resource efficiency of the system. Overall, different approaches for meeting a 100% renewable electricity penetration are not equally desirable when material resource usage is considered. This should be taken into account in future energy system planning studies. [ABSTRACT FROM AUTHOR]

Increased usage of renewable energy resources is key for energy system evolution to address environmental concerns. Capturing variable renewable power requires the use of energy storage to shift generation and load demand. The integration of plug-in electric vehicles, however, impacts the load demand profile and therefore the capacity of energy storage required to meet renewable utilization targets. This study examines how the intelligence of plug-in electric vehicle (PEV) integration impacts the required capacity of energy storage systems to meet renewable utilization targets for a large-scale energy system, using California as an example for meeting a 50% and 80% renewable portfolio standard (RPS) in 2030 and 2050. For an 80% RPS in 2050, immediate charging of PEVs requires the installation of an aggregate energy storage system with a power capacity of 60% of the installed renewable capacity and an energy capacity of 2.3% of annual renewable generation. With smart charging of PEVs, required power capacity drops to 16% and required energy capacity drops to 0.6%, and with vehicle-to-grid (V2G) charging, non-vehicle energy storage systems are no longer required. Overall, this study highlights the importance of intelligent PEV charging for minimizing the scale of infrastructure required to meet renewable utilization targets. [ABSTRACT FROM AUTHOR]

A study has been performed to understand the quantitative impact of key differences between vehicle-to-grid and stationary energy storage systems on renewable utilization, greenhouse gas emissions, and balancing fleet operation, using California as the example. To simulate the combined electricity and light-duty transportation system, a detailed electric grid dispatch model (including stationary energy storage systems) was combined with an electric vehicle charging dispatch model that incorporates conventional smart and vehicle-to-grid capabilities. By subjecting smaller amounts of renewable energy to round-trip efficiency losses and thereby increasing the efficiency of renewable utilization, it was found that vehicle-to-grid energy storage can achieve higher renewable utilization levels and reduced greenhouse gas emissions compared to stationary energy storage systems. Vehicle-to-grid energy storage, however, is not as capable of balancing the power plant fleet compared to stationary energy storage systems due to the constraints of consumer travel patterns. The potential benefits of vehicle-to-grid are strongly dependent on the availability of charging infrastructure at both home and workplaces, with potential benefits being compromised with residential charging availability only. Overall, vehicle-to-grid energy storage can provide benefits over stationary energy storage depending on the system attribute selected for improvement, a finding amenable to managing through policy. [ABSTRACT FROM AUTHOR]

Alternative vehicles must appropriately interface with the electric grid and renewable generation to contribute to decarbonization. This study investigates the impact of infrastructure configurations and management strategies on the vehicle–grid interface and vehicle greenhouse gas reduction potential with regard to California's Executive Order S-21-09 goal. Considered are battery electric vehicles, gasoline-fueled plug-in hybrid electric vehicles, hydrogen-fueled fuel cell vehicles, and plug-in hybrid fuel cell vehicles. Temporally resolved models of the electric grid, electric vehicle charging, hydrogen infrastructure, and vehicle powertrain simulations are integrated. For plug-in vehicles, consumer travel patterns can limit the greenhouse gas reductions without smart charging or energy storage. For fuel cell vehicles, the fuel production mix must be optimized for minimal greenhouse gas emissions. The plug-in hybrid fuel cell vehicle has the largest potential for emissions reduction due to smaller battery and fuel cells keeping efficiencies higher and meeting 86% of miles on electric travel keeping the hydrogen demand low. Energy storage is required to meet Executive Order S-21-09 goals in all cases. Meeting the goal requires renewable capacities of 205 GW for plug-in hybrid fuel cell vehicles and battery electric vehicle 100s, 255 GW for battery electric vehicle 200s, and 325 GW for fuel cell vehicles. [ABSTRACT FROM AUTHOR]

SUMMARY Quantifying the severity of the intermittencies in solar irradiation is important for (i) understanding the potential impacts of high solar power penetration levels on the electric grid and (ii) evaluating the need for technologies that may be necessary to complement solar power in order to balance the electric grid. This study uses a spectral method to distinguish between cloud-induced and diurnal cycle-induced transients and to quantify the severity of intermittencies occurring over a range of timescales. The method is used to quantify variability between specific sites as well as to evaluate the sensitivity of solar power variability to spatial diversification of the solar farm portfolio. Results indicate that increasing the spatial diversity of the solar farm portfolio reduces the magnitude of the fluctuations in power output as a fraction of the total system capacity. This behavior is associated with two forces: (i) a reduction in the influence of fluctuations occurring at an individual site on the total profile and (ii) should the sites in question be sufficiently spaced apart, the fluctuations in solar irradiation that each site exhibits are uncorrelated and do not generally add up in tandem at short timescales. These effects reduce the degree of uncertainty and variability associated with solar farm output and demonstrate a reduction in the maximum magnitude of solar power fluctuations for a given solar penetration level. The rate of increase of the maximum solar power deviation from the 1-h average associated with increases in desired solar penetration level decreases in an inverse exponential manner with the number of sufficiently spaced sites composing the solar farm portfolio. These results imply that a lower amount of regulation or energy storage capacity is needed to regulate solar intermittency if solar installations and the accommodating transmission infrastructure are designed and operated appropriately. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Batteries are important for promoting renewable energy, but, like most engineered products, they contain multiple hazardous materials. The purpose of this study is to evaluate industrial-scale batteries using GreenScreen® for Safer Chemicals, an established chemical hazard assessment (CHA) framework, and to develop a systematic, transparent methodology to quantify the CHA results, harmonize them, and aggregate them into single-value hazard scores, which can facilitate quantitative comparison and a robust evaluation of data gaps, inconsistencies, and uncertainty through the implementation of carefully selected scenarios and stochastic multicriteria acceptability analysis (SMAA). Using multiple authoritative toxicity data sources, six battery products are evaluated: three lithium-ion batteries (lithium iron phosphate, lithium nickel cobalt manganese hydroxide, and lithium manganese oxide), and three redox flow batteries (vanadium redox, zinc-bromine, and all-iron). The CHA results indicate that many materials in these batteries, including reagents and intermediates, inherently exhibit high hazard; therefore, safer materials should be identified and considered in future designs. The scenario analysis and SMAA, combined, provide a quantitative evaluation framework to support the decision-making needed to compare alternative technologies. Thus, this study highlights specific strategies to reduce the use of hazardous materials in complex engineered products before they are widely used in this rapidly-expanding industry sector. [Display omitted] • Chemical hazard assessment of substances used in six lithium ion and flow batteries. • Materials of high concern and specific hazard endpoints identified for each battery. • Data inconsistencies, data gaps and uncertainty evaluated for each material assessed. • Data aggregation approach developed for both material and product based assessments. • Multi-criteria decision analysis applied to identify safer battery alternatives. [ABSTRACT FROM AUTHOR]