全球能源系统脱碳之路的新视角（英）-ssee&Oxford.pdf

A new perspective on decarbonising the global energy system ● Summary for policymakers Matthew Ives, Luca Righetti, Johanna Schiele, Kris De Meyer, Lucy Hubble-Rose, Fei Teng, Lucas Kruitwagen, Leah Tillmann-Morris, Tianpeng Wang, Rupert Way Way et al., 2019). Incorporating technology cost trends into a simple, transparent energy system model has produced new climate mitigation scenarios that starkly contrast to those currently produced for the IPCC and the International Energy Agency (IEA). It may come as a surprise that in most major climate mitigation models, such as the IPCC’s Integrated Assessment Models (IAMs), the costs of energy technologies are not handled very transparently. They assume unsubstantiated limits to cost declines and often contain out-of-date data (Jaxa-Rozen Krey et al., 2019). We use an alternative approach to explore the implications of these discrepancies and have found an exciting new decarbonisation scenario we have named the Decisive Transition in recognition of the commitment to a clean energy system that this scenario represents.4 ● Our response Our energy systems model is built on observed trends in the relationship between the rate of deployment and the cost of energy technologies such as solar, wind, batteries and hydrogen. Average global solar photovoltaic costs (Based on Way et al. 2020) Global final energy mix Decisive Transition scenario Our Decisive Transition scenario: • 2% p.a. useful energy growth (3.4% p.a. economic growth) • No expensive large-scale CCS required • Rapid phase-out of all fossil fuels • Large efficiency gains from electrification • Electricity prices are very likely to fall • Emissions are more aligned with Paris goals A novel approach to energy systems modelling – accounting transparently for the real-world, historical cost trends of renewable energy technologies – indicates that the decarbonisation of the global energy system: • Is likely to be cheaper than commonly assumed • May not require any declines in economic growth • Can be achieved without large investments in unproven and potentially expensive technologies ● The problem Existing energy system models have consistently underestimated the cost reductions and growth potential of key renewable and energy storage technologies. Average global solar photovoltaic costs (IEA World Energy Outlook 2001-2020, Nemet 2006, and IRENA 2020) Global final energy mix Sustainable Development Scenario The IEA’s Sustainable Development Scenario (IEA World Energy Outlook 2019): • 3.4% p.a. economic growth • Requires expensive large-scale carbon capture and that it will rely critically on technologies that are currently expensive, unproven, or potentially controversial – such as carbon capture and storage (CCS), second-generation biofuels, and new nuclear energy designs (e.g., small modular reactors). In this report, we present two contrasting scenarios that illustrate how properly accounting for technological cost trends can challenge common perceptions regarding the costs and benefits of a Decisive Transition to clean energy technologies. The modelling presented in this report contrasts two very different scenarios: a Stalled Transition, in which total demand for energy services continues to grow at its historical average of 2% per year, but with the ratios of the different energy technologies frozen at their current values. This scenario provides a useful ‘worst- case’ baseline and a counterfactual for estimating relative costs. The second scenario is a Decisive Transition in which current exponential growth rates in clean energy technologies continue for the next decade, then gradually relax back to the low system- wide rate. Here we see that within 25 years, fossil fuels are displaced from the energy sector, with all essential liquid fuel use replaced by “green” hydrogen-based fuels. Solar and wind provide most of the energy; transport and heat are mostly electrified; and reliable electricity is maintained using batteries and chemical-based energy storage technologies. To provide a like-for-like comparison with the Stalled Transition, useful energy also grows at 2% per year, a rate much higher than in other deep decarbonisation scenarios. Our Decisive Transition achieves almost all the reductions in greenhouse gas emissions necessary to match the most ambitious IPCC scenarios. Figure 1 presents the global warming associated with the Stalled (orange) and Decisive Transition (purple) scenarios compared to three key IPCC warming scenarios. Our Stalled Transition scenario is most closely aligned with what is regarded as the ‘worst-case’ IPCC scenario (SSP5 RCP8.5). The Decisive Transition is most comparable to the SSP1 RCP2.6 high mitigation ambition “Taking the Green Road” scenario. This is a remarkable outcome because, in contrast to the high ambition IPPC scenarios (SSP1 RCP1.9 and SSP1 RCP2.6), the Decisive Transition scenario achieves this result without reducing non- energy-based emissions; without any significant deployment of nuclear, carbon capture and storage, or energy-saving technologies; and without requiring a reduction in energy demand or economic growth. It is merely a result of extending the current high growth rates in deployment of clean energy technologies for another decade. 6      
(dg -dg) 4  4 0 3  3 0  0    0 0  0 000 0 0 040 0 0 080 00 d • Figure 1: Comparisons of Temperature Anomalies from the estimated global emissions of two PTEC scenarios Stalled and Decisive Transition and three IPCC scenarios SSP5- RCP8.5 baseline, SSP1-RCP1.9 and SSP1-RCP2.6 The Decisive Transition is significantly cheaper than the Stalled Transition. The modelling show-cased in this report suggests that a clean energy system could be trillions of dollars less expensive to engineer than continuing with the current system based on fossil fuels (Way et al., 2020). This is even without factoring in pollution and associated morbidity and mortality (Vohra et al., 2021), or the multitude of additional physical climate costs likely to result from higher levels of global warming (Arnell et al., 2019). In the short- and medium-term, situations may arise where renewables cannot cheaply meet the energy demands of certain regions. In these situations, arguments might be made for investment in interim fossil-fuel-based solutions, such as natural gas. However, it should be kept in mind that such investments may not contribute to the final transition and can instead lead to carbon lock-in and create additional transition risk. Foreign aid should be aligned to enable developing states to instead “leapfrog” to electrification and new clean electricity generation, load balancing, and storage technologies.7 Unlike most other ambitious scenarios, the Decisive Transition scenario does not rely on underdeveloped technologies, such as carbon capture and storage (CCS) and Bioenergy with CCS (BECCS). This raises questions about whether we should continue channelling investment towards technologies like CCS and nuclear fusion for energy provision. Neither may mix particularly well with renewables and will detract investment away from driving down costs in renewables and storage technologies. It is still vital that we counter institutional and social barriers to a Decisive Transition, that financial stability is maintained, that gender and social equality is maintained or improved, and that job losses in the fossil fuel industries are addressed. The IEA has shown the potential for renewables to provide far more jobs than other energy-related investments (IEA, 2020), but these jobs may not be created in the areas where coal mines are being closed. Industrial strategies will therefore need to be developed to counter such transition risks. Efforts to maintain or improve gender and social equality should be prioritised now to avoid perpetuating existing gender inequalities (Pearl-Martinez & Stephens, 2016). Social equity concerns also go well beyond the implications for coal miners and include communities tied to coal-fired power stations and communities linked to oil extraction and refinement (Carley & Konisky, 2020). Countries with high reliance on coal-fired energy will also require international support in establishing grid balancing, storage, and efficient power markets to enable higher renewable penetration. Transition risks are real and likely, given how rapidly technological trends are moving, but it must be remembered that, unlike physical climate risks, stranded assets are only a one-off cost. If we do not end climate change, the more frequent and damaging extreme hurricanes, floods, droughts, and wildfires are likely to cause far greater economic costs that will be constant, long-term, and potentially permanent. Our estimates show the costs of climate damages up to the end of the century from a Stalled Transition are at least ten times greater than any transition risk associated with the Decisive Transition. In summary, the Decisive Transition scenario indicates that the decarbonisation of the global energy system: • Is likely to be cheaper than commonly assumed. • May not require any declines in economic growth. • Can be achieved without large investments in unproven and potentially expensive technologies. • Has the potential to save hundreds of trillions of dollars in physical climate damages. This new perspective also suggests that renewable technologies like solar and wind can provide a steady and secure energy supply, rebutting common beliefs regarding the intermittency problems with renewables. There is a belief that the large-scale deployment of renewables in the global energy system will lead to energy supply failures and high grid integration costs in the future. Our model challenges these perceptions by coupling solar and wind deployment with the deployment of sufficient short-term storage (e.g., batteries) and long-term storage (e.g., hydrogen and ammonia) technologies to ensure high levels of energy security.