Editing IPCC:AR6/WGIII/Chapter-6 (section)

==== 6.6.2.6 Greater Reliance on Integrated Energy System Approaches ====

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Energy systems integration refers to connected planning and operations across energy carriers, including electricity, fuels, and thermal resources. Coordinated planning could be important in lowering system costs, increasing reliability, minimising environmental impacts, and ensuring that costs of R&amp;D and infrastructure account for not just current needs but also for those of future energy systems ( [[#6.4.3|Section 6.4.3]] ). Integration includes not only the physical energy systems themselves but also simultaneous societal objectives (e.g., sustainable development goals), innovation processes (e.g., coordinating R&amp;D to increase the likelihood of beneficial technological spillovers), and other institutional and infrastructural transformations ( [[#Sachs--2019|Sachs et al. 2019]] ). Given system variability and differences in regional resources, there are economic and technical advantages to greater coordination of investments and policies across jurisdictions, sectors, and levels of government ( [[#Schmalensee--2017|Schmalensee and Stavins 2017]] ). Coordinated planning and operations can improve system economics by sharing resources, increasing the utilisation of capital-intensive assets, enhancing the geographical diversity of resource bases, and smoothing demand. But integration could require regulatory and market frameworks to facilitate and appropriate price signals to align incentives and to coordinate investments and operations.

Carbon-neutral energy systems are likely to be more interconnected than those of today ( ''high confidence'' ). The many possible feedstocks, energy carriers, and interconversion processes imply a greater need for the integration of production, transport, storage, and consumption of different fuels ( [[#Davis--2018|Davis et al. 2018]] ). For instance, electrification is expected to play an important role in decarbonising light-duty vehicles (Chapter 10, [[#6.4.3|Section 6.4.3]] ), yet the electricity and transport sectors have few direct interactions today. Systems integration and sectoral coupling are increasingly relevant to ensure that net-zero energy systems are reliable, resilient, and affordable ( [[#EPRI--2017|EPRI 2017]] ; Martin et al. 2017; [[#Buttler--2018|Buttler and Spliethoff 2018]] ; [[#O’Malley--2020|O’Malley et al. 2020]] ). Deep decarbonisation offers new opportunities and challenges for integrating different sectors as well as supply- and demand-side options. For instance, increasing electrification will change daily and seasonal load shapes, and end-use flexibilities and constraints could impact the desirability of different supply-side technologies ( [[#Brown--2018|Brown et al. 2018]] ; [[#EPRI--2019b|EPRI 2019b]] ). The feasibility of net-zero energy system configurations could depend on demonstrating cross-sector benefits like balancing VRE sources in the electricity sector, and on offering the flexibility to produce multiple products. For instance, low-emissions synthetic fuels could help to bridge stationary and mobile applications, since fuel markets have more flexibility than instantaneously balanced electricity markets due to the comparative ease and cost of large-scale, long-term storage of chemical fuels ( [[#Davis--2018|Davis et al. 2018]] ).

There are few detailed archetypes of integrated energy systems that provide services with zero- or net-negative CO 2 emissions (such as [[#Jacobson--2019|Jacobson et al. 2019]] ), so there is considerable uncertainty about integration and interactions across parts of the system. Although alternate configurations, trade-offs, and pathways are still being identified, common elements include fuels and processes like zero- or negative-CO 2 electricity generation and transmission, hydrogen production and transport, synthetic hydrocarbon production and transport, ammonia production and transport, and carbon management, where linkages across pathways could include the use of electricity to produce hydrogen via electrolysis ( [[#Smith--2016|Smith et al. 2016]] ; [[#Moore--2017|Moore 2017]] ; [[#Davis--2018|Davis et al. 2018]] ; [[#Jenkins--2018b|Jenkins et al. 2018b]] ; [[#Shih--2018|Shih et al. 2018]] ; [[#van%20Vuuren--2018|van Vuuren et al. 2018]] ). Linked analytical frameworks are increasing being used to understand the potential role for system coupling with greater temporal resolution, spatial resolution, and heterogeneity of consumer and firm decisions (Bohringer and Rutherford 2008; [[#Bistline--2017|Bistline and de la Chesnaye 2017]] ; [[#Collins--2017|Collins et al. 2017]] ; [[#Gerboni--2017|Gerboni et al. 2017]] ; [[#Santen--2017|Santen et al. 2017]] ; [[#Pye--2021|Pye et al. 2021]] ).

Challenges associated with integrating net-zero energy systems include rapid technological change, the importance of behavioural dimensions in domains with limited experience and data, policy changes and interactions, and path dependence. Technological cost and public acceptance will influence the degree of integration. Sectoral pathways will likely be adaptive and adjust based on the resolution of uncertainties over time, and the relative competitiveness will evolve as the technological frontier evolves, which is a complex and path-dependent function of deployment, R&amp;D, and inter-industry spillovers. Supply-side options interact with demand-side measures in increasingly integrated energy systems ( [[#Sorrell--2015|Sorrell 2015]] ; [[#van%20Vuuren--2018|van Vuuren et al. 2018]] ).

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