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Open Access Publications from the University of California

Scholarly Works (10 results)

  • Article
  • Peer Reviewed
UC Berkeley Previously Published Works (2016)
To prepare for an urban influx of 2.5 billion people by 2050, it is critical to create cities that are low-carbon, resilient, and livable. Cities not only contribute to global climate change by emitting the majority of anthropogenic greenhouse gases but also are particularly vulnerable to the effects of climate change and extreme weather. We explore options for establishing sustainable energy systems by reducing energy consumption, particularly in the buildings and transportation sectors, and providing robust, decentralized, and renewable energy sources. Through technical advancements in power density, city-integrated renewable energy will be better suited to satisfy the high-energy demands of growing urban areas. Several economic, technical, behavioral, and political challenges need to be overcome for innovation to improve urban sustainability.
    Cover page: City-integrated renewable energy for urban sustainability
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2017)
    Distributed photovoltaics (PV) have played a critical role in the deployment of solar energy, currently making up roughly half of the global PV installed capacity. However, there remains significant unused economically beneficial potential. Estimates of the total technical potential for rooftop PV systems in the United States calculate a generation comparable to approximately 40% of the 2016 total national electric-sector sales. To best take advantage of the rooftop PV potential, effective analytic tools that support deployment strategies and aggressive local, state, and national policies to reduce the soft cost of solar energy are vital. A key step is the low-cost automation of data analysis and business case presentation for structure-integrated solar energy. In this paper, the scalability and resolution of various methods to assess the urban rooftop PV potential are compared, concluding with suggestions for future work in bridging methodologies to better assist policy makers.
      Cover page: Rooftop solar photovoltaic potential in cities: how scalable are assessment approaches?
      • Article
      • Peer Reviewed
      UC Berkeley Previously Published Works (2019)
      The rooftop solar industry in the United States has experienced dramatic growth—roughly 50% per year since 2012, along with steadily falling prices. Although the opportunities this affords for clean, reliable power are transformative, the benefits might not accrue to all individuals and communities. Combining the location of existing and potential sites for rooftop photovoltaics (PV) from Google’s Project Sunroof and demographic information from the American Community Survey, the relative adoption of rooftop PV is compared across census tracts grouped by racial and ethnic majority. Black- and Hispanic-majority census tracts show on average significantly less rooftop PV installed. This disparity is often attributed to racial and ethnic differences in household income and home ownership. In this study, significant racial disparity remains even after we account for these differences. For the same median household income, black- and Hispanic-majority census tracts have installed less rooftop PV compared with no majority tracts by 69 and 30%, respectively, while white-majority census tracts have installed 21% more. When correcting for home ownership, black- and Hispanic-majority census tracts have installed less rooftop PV compared with no majority tracts by 61 and 45%, respectively, while white-majority census tracts have installed 37% more. The social dispersion effect is also considered. This Analysis reveals the racial and ethnic injustice in rooftop solar participation.
        Cover page: Disparities in rooftop photovoltaics deployment in the United States by race and ethnicity
        • Thesis
        • Peer Reviewed
        UC Berkeley Electronic Theses and Dissertations (2013)

        Distributed solar thermal combined heat and power is an area where there is potential for significant innovation to reduce the cost of solar energy. Two areas for innovation were explored: reduced thermal losses in a novel dual-chamber absorber tube and parametric study for optimal efficiency of small-scale (5-10 kW) radial inflow turbines.

        Increasing the peak temperature in solar thermal systems typically increases the cycle thermal efficiency. However, the outer wall temperature of the absorber tube also increases causing greater thermal losses to the surroundings. A novel finned dual-chamber absorber tube design was presented as a possible solution. Fins attached to the outer wall could serve as a heat sink to send heat into the inner chamber. Computation modeling was validated by a reduced-scale experiment to the accuracy of the correlations used. From these models, it has been demonstrated that the heat loss to the environment from the outer wall of the absorber tube could be reduced by 10-60%. The best performance was found when water enters the outer chamber at the highest mass flow rate tested. This impressive improvement encourages further development of the dual chamber design.

        One of the primary obstacles of scaling down solar thermal technology for distributed power generation is finding an appropriate expander design. The radial inflow turbine was considered. A parametric study of seventeen input parameters was completed. Of these parameters, the mass flow rate, r2,hr2,t (ratio of rotor exit hub radius to rotor exit tip radius) and r2,tr1a (ratio of rotor exit tip to rotor inlet radius) had the greatest influence on the thermal efficiency of the system. Decreasing the mass flow rate both increased the turbine efficiency and increased the pressure drop across the turbine both of which enhanced the thermal efficiency. The optimized value of r2,hr2,t and r2,tr1a depended on the type of fluid. Wet fluids had an optimal performance with low values of r2,tr1a but high values of r2,hr2,t. Dry fluids had an optimal thermal performance with low values of both r2,hr2,t and r2,tr1a . Of the fluids studied it appears that dry fluids with low molecular mass and high critical temperature yielded the greatest thermal efficiency. Such fluids typically have low viscosity, allowing there to be less frictional losses in the turbine leading to better thermal efficiencies. Unfortunately, these fluids also share the characteristic of being highly toxic. In order for the radial inflow turbine to scale with reasonable efficiency, a non-toxic dry fluid with low molecular mass and high critical temperature would need to be found.

          Cover page: Design and Analysis of Small-Scale Solar Thermal Combined Heat and Power Systems
          • Article
          • Peer Reviewed
          LBL Publications (2024)
          This paper defines a policy-relevant nationwide composite index to identify communities disproportionately impacted by environmental, energy, and climate injustices in the United States. We review existing vulnerability indicators and indices to assess the tradeoffs of different design parameters, including variable selection, geographic unit, dimensionality reduction, weighting, and aggregation methods. From this methodological review, we create the first nationwide, census tract-level index of cumulative burden that includes energy-relevant indicators alongside climate, social, environmental, and economic indicators, and is flexible to the inclusion of additional data sources. We provide a summary of the sources of inputs used to develop a definition for “disadvantaged communities” that can be used to prioritize energy investments. We discuss use-cases for this index including the implementation of the Justice40 Initiative, which calls for 40 % of certain federal clean energy benefits to flow to disadvantaged communities in the United States. We use our results to examine historic allocations of federal energy investments and show that communities that we identify as disadvantaged received about 37 % fewer funds per capita than non-disadvantaged communities.
            Creative Commons 'BY' version 4.0 license
            • Article
            • Peer Reviewed
            UC Berkeley Previously Published Works (2017)
            The technically recoverable global wave energy resource is estimated to be between 2 PWh/year and 5.5 PWh/year, approximately 12% and 32% of global electricity consumption. Despite wave energy's vast global potential, there has been relatively little commercial deployment to date. There is large variation in both the current estimated and future expected electricity generation costs associated with wave technologies. This paper quantifies a forecasted levelized cost of electricity (LCOE) for wave energy by performing a two-stage Monte Carlo simulation, considering both the variability in current LCOE estimates and uncertainty in the one-factor learning rate. We compare the forecasted LCOE to wave energy targets of the European Union and U.S. Department of Energy and show the criticality of support mechanisms to achieve learning rates that lead to economic competitiveness in the utility-scale markets.
              Cover page: Two-Stage Monte Carlo Simulation to Forecast Levelized Cost of Electricity for Wave Energy
              • Article
              • Peer Reviewed
              UC Berkeley Previously Published Works (2018)
              Renewable energy is often presented as a partisan issue. However, solar incentives have made rooftop PV attractive to many consumers, regardless of political affiliation. This paper quantifies the role of political affiliation in rooftop PV adoption for the Democratic-leaning state of New York and Republican-leaning state of Texas. High resolution rooftop PV installation data from Google Project Sunroof is combined with election data from the Harvard Election Data Archive. We applied a bootstrapped LOWESS model to fit local linear relationships between rooftop PV adoption and both voting behavior and household income. In doing so, we find that Republican-majority communities are installing rooftop PV at equal or greater rates than Democraticmajority communities. While Republican politicians may be less likely than Democrats to support renewable energy, this partisan division is not found at the voter level.
                • Article
                • Peer Reviewed
                UC Berkeley Previously Published Works (2018)
                There have been numerous emerging next generation solar cell technologies with the potential to disrupt the solar industry. Perovskites in particular have taken the spotlight recently with unprecedented efficiency improvements. To quantify the rate of innovation in next generation solar technologies, we used learning curves to model improvements in efficiency relative to three parameters: Time since first publication, cumulative publications, and cumulative patents. The learning rates found for perovskite solar cells are compared to those of dye-sensitized, and quantum dot solar cells. In doing so, this analysis aims to elicit a better understanding of the drivers of innovation for emerging solar technologies and identify technologies demonstrating extraordinary technological progress.
                  • Article
                  • Peer Reviewed
                  UC Berkeley Previously Published Works (2024)
                  As the world races to decarbonize power systems to mitigate climate change, the body of research analyzing paths to zero emissions electricity grids has substantially grown. Although studies typically include commercially available technologies, few of them consider offshore wind and wave energy as contenders in future zero-emissions grids. Here, we model with high geographic resolution both offshore wind and wave energy as independent technologies with the possibility of collocation in a power system capacity expansion model of the Western Interconnection with zero emissions by 2050. In this work, we identify cost targets for offshore wind and wave energy to become cost effective, calculate a 17% reduction in total installed capacity by 2050 when offshore wind and wave energy are fully deployed, and show how curtailment, generation, and transmission change as offshore wind and wave energy deployment increase.
                    Cover page: Offshore wind and wave energy can reduce total installed capacity required in zero-emissions grids
                    • Article
                    • Peer Reviewed
                    UC San Diego Previously Published Works (2021)
                    The electric power grid is a critical societal resource connecting multiple infrastructural domains such as agriculture, transportation, and manufacturing. The electrical grid as an infrastructure is shaped by human activity and public policy in terms of demand and supply requirements. Further, the grid is subject to changes and stresses due to diverse factors including solar weather, climate, hydrology, and ecology. The emerging interconnected and complex network dependencies make such interactions increasingly dynamic, posing novel risks, and presenting new challenges to manage the coupled human-natural system. This paper provides a survey of models and methods that seek to explore the significant interconnected impact of the electric power grid and interdependent domains. We also provide relevant critical risk indicators (CRIs) across diverse domains that may be used to assess risks to electric grid reliability, including climate, ecology, hydrology, finance, space weather, and agriculture. We discuss the convergence of indicators from individual domains to explore possible systemic risk, i.e., holistic risk arising from cross-domain interconnections. Further, we propose a compositional approach to risk assessment that incorporates diverse domain expertise and information, data science, and computer science to identify domain-specific CRIs and their union in systemic risk indicators. Our study provides an important first step towards data-driven analysis and predictive modeling of risks in interconnected human-natural systems.
                      Cover page: Critical Risk Indicators (CRIs) for the electric power grid: a survey and discussion of interconnected effects.
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