Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (10 results)

  • Thesis
  • Peer Reviewed
UC Berkeley Electronic Theses and Dissertations (2015)

Global warming is one of the most significant problems facing humanity, and reducing emissions from the electricity sector is critical for mitigating global warming impacts. My work here focuses on developing computational tools to plan cost effective mitigation pathways for the electricity sector and using them collaboratively. The complexity and scale of globally transitioning electrical power grids away from fossil fuels over the coming decades will require a large-scale collaborative effort with effective coordination of many actors trained in diverse disciplines. Historically, energy-modeling efforts have tended to be siloed and fragmented between and even within research groups. In my research I have attempted to provide an alternative to that status quo by improving an open source renewable planning model, Switch, increasing its usability and accessibility to interdisciplinary researchers, and collaboratively applying it to mitigation planning.

We used the Switch model to conduct detailed research into cost effective mitigation pathways for the Western portion of North America, or the WECC power grid. We found that renewable portfolio standards were insufficient to meet climate stabilization goals, and more targeted policies were needed that specifically focused on emission reductions. We identified investment plans that could lead to dramatic decreases in emissions without significantly increasing electricity costs over the next twenty years by retiring coal and replacing it with natural gas and renewables while evolving the grid to better accommodate variable renewable energy.

We found that meeting overall 2050 targets will require concerted action on many fronts, including aggressive efficiency programs, electrification of transportation and heating, and dramatically reducing emissions from the electricity sector. Meeting 2050 emission goals without significantly increasing energy costs also will require additional technological innovation. Two promising technological pathways for long-term cost containment are developing low cost solar in conjunction with low cost storage or demand response, and developing Biomass Energy with Carbon Capture and Sequestration (BECCS) to provide emission offsets during the last stages of emission reductions. We found that the emissions offsets provided by BECCS were much more valuable than the energy, suggesting that other sequestration options such as improved land management that increases soil carbon deposition could be a particularly valuable part of an economy-wide portfolio.

We started this research in the early days of the natural gas boom caused by widespread use of hydraulic fracturing. As data emerged on potentially high methane leakage rates in the natural gas supply chain, we investigated how leakage impacts roles Natural Gas (NG) can play in a low emission power grid. We found that leakage rates significantly reduce the use of NG as a direct substitute for coal, but have a smaller impact on the use of combustion turbines for reserves and peaking capacity. Higher leakage rates increase electricity costs in optimal solutions by an average of 1.3% ±0.068 and decrease NG consumption by 18% ±0.55 for each percentage point increase in the leakage rate in the next decade.

Increased leakage can increase or decrease the use of NG to complement renewables, depending on the emissions cap context and technological alternatives. In the 2020 and 2030 timeframes under moderate emission caps, higher leakage rates prompt the installation of more renewables and prompt NG Combined Cycle Gas Turbines (CCGT) to shift from baseload operation to running as-needed to complement renewables. In the 2030 timeframe, higher leakage often prompts installation of new NG Combustion turbines with Compressed Air Energy Storage, which is used to complement variability from renewable resources within a day. Scenarios that include low-cost battery storage or low-emission baseload options of Coal CCS or Nuclear have less Compressed Air Energy Storage installed in the 2030 timeframe because these technologies provide alternate emission reduction paths. In the 2040 and 2050 timeframes with tighter emission caps, NG is already used primarily to complement renewables and higher leakage rates tend to decrease its use in any role.

Throughout this process, I made significant advancements to Switch as an analytical tool for collaborative work by interdisciplinary research teams. I initially increased the usability and lowered the learning curve while training colleagues who lacked computer science backgrounds, as well as developing execution workflows to increase reproducibility and leverage high performance workstations and computing clusters. I played a crucial role in developing detailed databases to describe the WECC electricity grid and calculating renewable energy potential at a high geographic and temporal resolution over a large area. I developed new techniques for describing policies and tracking both the renewable fraction and emission intensity of electricity. I developed techniques for simulating grid dispatch of investment portfolios on ~100x as many timepoints to better estimate reliability, costs and emissions. I used that instrumentation ability to improve sampling methods and solution quality. Interviews with current and potential users indicated a need for a completely open source software stack, streamlined workflows for data ingestions and processing, as well as a graphical front-end to complement the command line interface. These usability enhancements are the subject of ongoing and future work.

Overall, this open collaborative approach has proven quite successful. We trained four other research teams on two campuses to develop versions of this model for China, Chile and Nicaragua and to conduct a detailed systems-level analysis of Carbon Capture and Sequestration technologies. Those efforts led to recognition by the United Nations during the 2014 Climate Summit. The complete text of this dissertation is freely available online through the University of California Berkeley though other organizations may distribute this text behind a paywall. We have developed partnerships with a second academic campus, a consulting firm and Google who are all contributing to a new implementation of Switch in a completely open source software stack that supports stochastic programming and decomposition (Pyomo). We hope that the new version can serve as a open platform for evaluating and comparing research methodologies as well as supporting investment planning and policy analysis for consulting firms, government agencies, academics, utilities and NGOs.

  • 2 supplemental ZIPs
Cover page: Open and Collaborative Climate Change Mitigation Planning for Electric Power Grids
  • Article
  • Peer Reviewed
UC Berkeley Previously Published Works (2016)
We explore the operations, balancing requirements, and costs of the Western Electricity Coordinating Council power system under a stringent greenhouse gas emission reduction target. We include sensitivities for technology costs and availability, fuel prices and emissions, and demand profile. Meeting an emissions target of 85% below 1990 levels is feasible across a range of assumptions, but the cost of achieving the goal and the technology mix are uncertain. Deployment of solar photovoltaics is the main driver of storage deployment: the diurnal periodicity of solar energy availability results in opportunities for daily arbitrage that storage technologies with several hours of duration are well suited to provide. Wind output exhibits seasonal variations and requires storage with a large energy subcomponent to avoid curtailment. The combination of low-cost solar technology and advanced battery technology can provide substantial savings through 2050, greatly mitigating the cost of climate change mitigation. Policy goals for storage deployment should be based on the function storage will play on the grid and therefore incorporate both the power rating and duration of the storage system. These goals should be set as part of overall portfolio development, as system flexibility needs will vary with the grid mix.
    Cover page: Power system balancing for deep decarbonization of the electricity sector
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2013)
    The United States Department of Energy's SunShot Initiative has set cost-reduction targets of $1/watt for central-station solar technologies. We use SWITCH, a high-resolution electricity system planning model, to study the implications of achieving these targets for technology deployment and electricity costs in western North America, focusing on scenarios limiting carbon emissions to 80% below 1990 levels by 2050. We find that achieving the SunShot target for solar photovoltaics would allow this technology to provide more than a third of electric power in the region, displacing natural gas in the medium term and reducing the need for nuclear and carbon capture and sequestration (CCS) technologies, which face technological and cost uncertainties, by 2050. We demonstrate that a diverse portfolio of technological options can help integrate high levels of solar generation successfully and cost-effectively. The deployment of GW-scale storage plays a central role in facilitating solar deployment and the availability of flexible loads could increase the solar penetration level further. In the scenarios investigated, achieving the SunShot target can substantially mitigate the cost of implementing a carbon cap, decreasing power costs by up to 14% and saving up to $20 billion ($2010) annually by 2050 relative to scenarios with Reference solar costs.
      • Article
      • Peer Reviewed
      UC Berkeley Previously Published Works (2015)
        • Article
        • Peer Reviewed
        UC Berkeley Previously Published Works (2017)
          Cover page: Biomass enables the transition to a carbon-negative power system across western North America (vol 5, pg 230, 2015)
          • Article
          • Peer Reviewed
          UC Berkeley Previously Published Works (2015)
          Sustainable biomass can play a transformative role in the transition to a decarbonized economy, with potential applications in electricity, heat, chemicals and transportation fuels. Deploying bioenergy with carbon capture and sequestration (BECCS) results in a net reduction in atmospheric carbon. BECCS may be one of the few cost-effective carbon-negative opportunities available should anthropogenic climate change be worse than anticipated or emissions reductions in other sectors prove particularly difficult. Previous work, primarily using integrated assessment models, has identified the critical role of BECCS in long-term (pre- or post-2100 time frames) climate change mitigation, but has not investigated the role of BECCS in power systems in detail, or in aggressive time frames, even though commercial-scale facilities are starting to be deployed in the transportation sector. Here, we explore the economic and deployment implications for BECCS in the electricity system of western North America under aggressive (pre-2050) time frames and carbon emissions limitations, with rich technology representation and physical constraints. We show that BECCS, combined with aggressive renewable deployment and fossil-fuel emission reductions, can enable a carbon-negative power system in western North America by 2050 with up to 145% emissions reduction from 1990 levels. In most scenarios, the offsets produced by BECCS are found to be more valuable to the power system than the electricity it provides. Advanced biomass power generation employs similar system design to advanced coal technology, enabling a transition strategy to low-carbon energy.
            Cover page: Biomass enables the transition to a carbon-negative power system across western North America
            • Article
            • Peer Reviewed
            UC Berkeley Previously Published Works (2015)
            The global carbon emissions budget over the next decades depends critically on the choices made by fast-growing emerging economies. Few studies exist, however, that develop country-specific energy system integration insights that can inform emerging economies in this decision-making process. High spatial- and temporal-resolution power system planning is central to evaluating decarbonization scenarios, but obtaining the required data and models can be cost prohibitive, especially for researchers in low, lower-middle income economies. Here, we use Nicaragua as a case study to highlight the importance of high-resolution open access data and modeling platforms to evaluate fuel-switching strategies and their resulting cost of power under realistic technology, policy, and cost scenarios (2014-2030). Our results suggest that Nicaragua could cost-effectively achieve a low-carbon grid (≥80%, based on non-large hydro renewable energy generation) by 2030 while also pursuing multiple development objectives. Regional cooperation (balancing) enables the highest wind and solar generation (18% and 3% by 2030, respectively), at the least cost (US$127 MWh-1). Potentially risky resources (geothermal and hydropower) raise system costs but do not significantly hinder decarbonization. Oil price sensitivity scenarios suggest renewable energy to be a more cost-effective long-term investment than fuel oil, even under the assumption of prevailing cheap oil prices. Nicaragua's options illustrate the opportunities and challenges of power system decarbonization for emerging economies, and the key role that open access data and modeling platforms can play in helping develop low-carbon transition pathways.
              Cover page: Evidence and future scenarios of a low-carbon energy transition in Central America: a case study in Nicaragua
              • Article
              • Peer Reviewed
              UC Berkeley Previously Published Works (2016)
              We present an integrated model, SWITCH-China, of the Chinese power sector with which to analyze the economic and technological implications of a medium to long-term decarbonization scenario while accounting for very-short-term renewable variability. On the basis of the model and assumptions used, we find that the announced 2030 carbon peak can be achieved with a carbon price of ∼$40/tCO2. Current trends in renewable energy price reductions alone are insufficient to replace coal; however, an 80% carbon emission reduction by 2050 is achievable in the Intergovernmental Panel on Climate Change Target Scenario with an optimal electricity mix in 2050 including nuclear (14%), wind (23%), solar (27%), hydro (6%), gas (1%), coal (3%), and carbon capture and sequestration coal energy (26%). The co-benefits of carbon-price strategy would offset 22% to 42% of the increased electricity costs if the true cost of coal and the social cost of carbon are incorporated. In such a scenario, aggressive attention to research and both technological and financial innovation mechanisms are crucial to enabling the transition at a reasonable cost, along with strong carbon policies.
                Cover page: SWITCH-China: A Systems Approach to Decarbonizing China’s Power System
                • Article
                • Peer Reviewed
                UC Berkeley Previously Published Works (2018)
                After undergoing an unprecedented energy reform, Mexico is poised to significantly grow its renewable energy share, and evolve from 80 MW installed solar photovoltaics (PV) capacity in 2015, to more than 6 GW by 2022. The impact on the overall electrical grid is therefore a crucial element to determine where the investments should be allocated -both in generation, and transmission-, to be optimally deployed. In this contribution, we model the generation, transmission and distribution assets in Mexico and optimize the investment in capacity to meet policy goals under three different plausible scenarios.
                  • Article
                  • Peer Reviewed
                  UC Berkeley Previously Published Works (2015)
                  © 2015 The Author(s) Jurisdictions throughout the world are contemplating greenhouse gas (GHG) mitigation strategies that will enable meeting long-term GHG targets. Many jurisdictions are now focusing on the 2020–2050 timeframe. We conduct an inter-model comparison of nine California statewide energy models with GHG mitigation scenarios to 2050 to better understand common insights across models, ranges of intermediate GHG targets (i.e., for 2030), necessary technology deployment rates, and future modeling needs for the state. The models are diverse in their representation of the California economy: across scenarios with deep reductions in GHGs, annual statewide GHG emissions are 8–46 % lower than 1990 levels by 2030 and 59–84 % lower by 2050 (not including the Wind-Water-Solar model); the largest cumulative reductions occur in scenarios that favor early mitigation; non-hydroelectric renewables account for 30–58 % of electricity generated for the state in 2030 and 30–89 % by 2050 (not including the Wind-Water-Solar model) ; the transportation sector is decarbonized using a mix of energy efficiency gains and alternative-fueled vehicles; and bioenergy is directed almost exclusively towards the transportation sector, accounting for a maximum of 40 % of transportation energy by 2050. Models suggest that without new policies, emissions from non-energy sectors and from high-global-warming-potential gases may alone exceed California’s 2050 GHG goal. Finally, future modeling efforts should focus on the: economic impacts and logistical feasibility of given scenarios, interactive effects between two or more climate policies, role of uncertainty in the state’s long-term energy planning, and identification of pathways that achieve the dual goals of criteria pollutant and GHG emission reduction.
                    Top