سناریوهای کاهش گاز گلخانه ای عمیق برای کالیفرنیا - مفاهیم استراتژیک از مدل سیستم های انرژی اقتصادی CA-تایمز

California has taken a leading role in regulating greenhouse gas (GHG) emissions, requiring that its economy-wide emissions be brought back down to the 1990 level by 2020. The state also has a long-term, aspirational goal of an 80 percent reduction below the 1990 level by 2050. While the steps needed to achieve the near-term target have already been clearly defined by California policy makers, the suite of transformational technologies and policies required to decarbonize the energy system over the long term have not yet been explored. This paper describes an effort to fill this important gap, introducing CA-TIMES, a bottom-up, technologically-rich, integrated energy–engineering–environmental–economic systems model that has been developed to guide the long-term policy planning process. CA-TIMES is useful for exploring low-carbon scenarios, and the analyses described here focus on the potential evolution of the transportation, fuel supply, and electric generation sectors over the next several decades in response to various energy and climate policies. We find that meeting California’s 80% emission reduction goal can be achieved through a combination of mitigation strategies, including managing the growth in energy service demand, increasing investments in efficiency and low-carbon energy supply technologies, and promoting demand technologies that facilitate end-use device electrification and a decrease in the direct use of hydrocarbon fuels through efficiency improvement and fuel switching. In such deep emission reduction scenarios, we estimate that energy system costs (accounting for investments on the energy supply side and in transportation demand technologies, as well as fuel and O&M costs) could be around 8–17% higher than in a reference case. Meanwhile, average abatement costs could range from $107 to $225/tCO2. These estimates are very much dependent on a range of socio-political and technological uncertainties, for instance, the availability and cost of biomass, nuclear power, carbon capture and storage, and electric and hydrogen vehicles.

In 2005 and 2006, California took several initial steps to address the threat posed by climate change. First, Governor Schwarzenegger issued Executive Order S-3-05, which declared an aspirational goal for California to reduce its greenhouse gas (GHG) emissions to 80% below the 1990 level. Then, in 2006 Assembly Bill 32 (AB32), the “Global Warming Solutions Act” became law, setting a binding target that GHG emissions be brought back down to the 1990 level by 2020. AB32 included a requirement that specific plans were to be developed as to how the state might achieve the 2020 goal. The AB32 scoping plan [1] provides a number of recommended actions to reduce emissions from a wide variety of sources and sectors and provides an important roadmap for achieving the near-term target. These policy measures include market-based mechanisms including cap-and-trade and a low-carbon fuel standard, and technology-specific standards and regulations including vehicle efficiency standards (commonly known as the Pavley standards), energy efficiency measures, a renewable portfolio standard (33% renewable electricity by 2020), truck and tire standards, etc. In contrast, the long-term 80% goal was set based on the anthropogenic emission rates needed in all industrialized countries to help stabilize atmospheric GHG concentrations at levels that would avoid dangerous climate change [2]. There exists significant uncertainty as to how these deep emission cuts would be achieved, what they would cost, and what policy measures would be needed. This paper explores the potential of various technology and policy options for reducing emissions across a number of different sectors, specifically the electricity generation, fuel supply and transportation sectors. It describes the development of an energy-economic optimization model of the California energy system (CA-TIMES) and presents scenarios for technology adoption and cost to 2050.

5.1. Key conclusions The CA-TIMES modeling framework has proven useful in assessing the suite of least-cost mitigation options that will be needed to meet California’s long-term 80% greenhouse gas emission reduction goal. The model fills an important research gap in the literature by combining a detailed technology and cost database with an energy systems optimization tool. A number of important mitigation strategies can be brought to bear to reduce energy sector emissions. Because of the inertia in energy system infrastructure and investments, however, rapid introduction and expansion of these technologies (e.g., low-carbon fuels and electricity conversion facilities; carbon capture and sequestration; advanced and highly-efficient end-use technologies, particularly in transport; and electrification of end-use appliances) needs to take place over the coming decade. Our results show that along with significant improvements in efficiency in each of the end-use sectors and travel demand reductions in the transportation sector, meeting the 80% reduction goal will likely require complete decarbonization of the electric sector. However, significant hurdles still remain for low-carbon electricity generation. For instance, the future development of renewable technologies and resources will need to address issues related to resource location, transmission and intermittency. And while nuclear power and fossil and/or biomass CCS appear to be critical options for low-carbon baseload generation, CCS has several technical issues that still need to be worked out, not to mention that both nuclear and CCS possess real and perceived issues with respect to safety and risk. The transportation sector emits over half of California’s GHG emissions at present and is the most costly and challenging sector to reduce emissions from. This study shows that rapidly improving vehicle efficiencies and slowing the growth in transport demand will be the most cost-effective mitigation strategies to reduce transportation GHG emissions. In addition, we find that decarbonizing electricity, biofuels, and hydrogen by introducing low-, zero- or negative-carbon fuel supply technologies and adopting complementary end-use technologies will also be essential to meet the deep GHG reduction goal. Moreover, given constraints on biomass resources, our analysis indicates that the optimal use of biofuels is in the heavy-duty, marine and aviation subsectors, replacing petroleum diesel, jet fuel, and residual fuel oil. In summary, a low-carbon transition in California appears to be feasible, though there are certain risks involved. In the event that one or more key energy technologies fails or is for some reason restricted in availability, achieving the 80% reduction goal by 2050 could become very difficult and expensive, if not impossible. 5.2. Future work Our research team continues to improve the representation of the California energy system within the CA-TIMES model. Planned additions for future iterations of the model include the specification of energy service demands and end-use technology options for the residential, commercial and industrial sectors; the inclusion of an elastic demand formulation so that the model can reduce demand endogenously based on higher energy prices; and a more detailed examination of timeslices and their impact on variable renewable generation in the electric sector. We also plan to endogenously represent consumer behavior within CA-TIMES transport sector by explicitly modeling mode-switching (i.e., between LDVs and transit buses/rail) and class-switching (i.e., between compact, small, mid-size, and large cars). Other policies will also be included in future model versions, including the low carbon fuel standard (LCFS). Lastly, although they account for only 11% of California’s total emissions at the present time, non-energy greenhouse gases also need to be accounted for in the modeling framework.