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The 2022 Critical Review (CR) by Heath et al. ([25]) used a comprehensive compilation of literature to assess how photovoltaic modules (PVs) and lithium ion batteries (LIBs) align with the principles and processes of a circular economy (CE). EPRI has been actively supporting the electric power industry's implementation of CE principles through research programs related to environmental issues across the life cycles of wind turbines, solar photovoltaics, and energy storage (EPRI [11]). EPRI worked with the Anthesis Group to develop an electric power industry-specific CE framework (EPRI [13]). While forward-thinking suppliers are helping push the industry in the right direction, an end user's sustainability objectives are necessary to accelerate the process (EPRI [16]; Powicki, Li, and Libby [34]). [Extracted from the article]

A parametric study of a solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system design is conducted with the intention of determining the thermodynamically based design space constrained by modern material and operating limits. The analysis is performed using a thermodynamic model of a generalized SOFC-GT system where the sizing of all components, except the fuel cell, is allowed to vary. Effects of parameters such as pressure ratio, fuel utilization, oxygen utilization, and current density are examined. Operational limits are discussed in terms of maximum combustor exit temperature, maximum heat exchanger effectiveness, limiting current density, maximum hydrogen utilization, and fuel cell temperature rise. It was found that the maximum hydrogen utilization and combustor exit temperature were the most significant constraints on the system design space. The design space includes the use of cathode flow recycling and air preheating via a recuperator (heat exchanger). The effect on system efficiency of exhaust gas recirculation using an ejector versus using a blower is discussed, while both are compared with the base case of using a heat exchanger only. It was found that use of an ejector for exhaust gas recirculation caused the highest efficiency loss, and the base case was found to exhibit the highest overall system efficiency. The use of a cathode recycle blower allowed the largest downsizing of the heat exchanger, although avoiding cathode recycling altogether achieved the highest efficiency. Efficiencies in the range of 50-75% were found for variations in pressure ratio, fuel utilization, oxygen utilization, and current density. The best performing systems that fell within all design constraints were those that used a heat exchanger only to preheat air, moderate pressure ratios, low oxygen utilizations, and high fuel utilizations. [DOI: 10.1115/1.4000263]

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]

A study was conducted to compare the technical potential and effectiveness of different water supply options for securing water availability in a large-scale, interconnected water supply system under historical and climate-change augmented inflow and demand conditions. Part 2 of the study focused on determining the greenhouse gas and renewable energy utilization impacts of different pathways to stabilize major surface reservoir levels. Using a detailed electric grid model and taking into account impacts on the operation of the water supply infrastructure, the greenhouse gas emissions and effect on overall grid renewable penetration level was calculated for each water supply option portfolio that successfully secured water availability from Part 1. The effects on the energy signature of water supply infrastructure were found to be just as important as that of the fundamental processes for each option. Under historical (baseline) conditions, many option portfolios were capable of securing surface reservoir levels with a net neutral or negative effect on emissions and a benefit for renewable energy utilization. Under climate change augmented conditions, however, careful selection of the water supply option portfolio was required to prevent imposing major emissions increases for the system. Overall, this analysis provided quantitative insight into the tradeoffs associated with choosing different pathways for securing California's water supply. [ABSTRACT FROM AUTHOR]

The technical potential and effectiveness of different water supply options for securing water availability in a large-scale, interconnected water supply system under historical and climate-change augmented inflow and demand conditions were compared. Part 1 of the study focused on determining the scale of the options required to secure water availability and compared the effectiveness of different options. A spatially and temporally resolved model of California's major surface reservoirs was developed, and its sensitivity to urban water conservation, desalination, and water reuse was examined. Potential capacities of the different options were determined. Under historical (baseline) hydrology conditions, many individual options were found to be capable of securing water availability alone. Under climate change augment conditions, a portfolio approach was necessary. The water savings from many individual options other than desalination were insufficient in the latter, however, relying on seawater desalination alone requires extreme capacity installations which have energy, brine disposal, management, and cost implications. The importance of identifying and utilizing points of leverage in the system for choosing where to deploy different options is also demonstrated. [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]

• Modeled climate change impacts on hydropower in Upper Yangtze River Basin in China. • Assessed simultaneous climate change effects on electricity supply and demand. • Translated climate supply–demand gap to greenhouse gas emissions implications. • Climate change exacerbates supply–demand gap seasonally and inter-annually. • Low-carbon resources are critical for reduce emissions from the supply–demand gap. Hydropower importantly provides flexible low-carbon electricity, however, climate change will affect the hydropower system through altering hydrologic regimes while also affecting electricity demands for heating and cooling that hydropower resources serve. This study assesses the effect of climate change on hydropower and electricity demand in the Upper Yangtze River Basin (UYRB) in China on the regional net electric load and greenhouse gas (GHG) emissions. This is accomplished by using climate projections from five global climate models (GCMs) to simultaneously force (1) a physically-based hydrological model and a statistically-based hydropower model to estimate the future generating capacity of 21 large hydropower plants in the UYRB and (2) an empirical electricity demand model accounting for socioeconomic and climatic factors. Under climate change, the projected hydropower generation in the UYRB tends to increase in the 21st century but is far less than the increase in electricity demand, increasing the gap between demand and supply. Future increases in overall electricity demand are driven by GDP growth, but climate change will alter the distribution of the seasonal electricity demand. Climate warming decreases electricity demand for heating in winter and increases electricity demand for cooling in summer, but ultimately increases demand. Meanwhile, there is an increasing mismatch between electricity demand and hydropower supply associated with inter- and intra-annual variations, owing to the temporal climate change and increase in compound climate extremes (droughts and heatwaves). Finally, meeting the gap between supply and demand due to climate change is estimated to contribute 79.0–184.6 and 50.6–316.2 MMT CO 2e /yr of additional GHG emissions by the mid and end of 21st century, respectively. [ABSTRACT FROM AUTHOR]