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

=== 6.4.3 Energy System Integration ===

<div id="h2-8-siblings" class="h2-siblings"></div>

Greenhouse gases are emitted across all economic activities. Therefore, cost-effective decarbonisation requires a ‘system of systems’ approach that considers the interaction between different energy sectors and systems. Flexibility technologies and advanced control of integrated energy systems (e.g., considering the interaction between electricity, heating/cooling, gas/hydrogen, transport sectors) could reduce energy infrastructure investments substantially in future low-carbon energy systems ( [[#Strbac--2015b|Strbac et al. 2015b]] ; [[#Jacobson--2019|Jacobson et al. 2019]] ).

The electricity grid will serve as a backbone of future low-carbon energy systems. Integration of large amounts of VRE generation ( [[#Hansen--2019|Hansen et al. 2019]] ), particularly wind and solar generation ( [[#Bistline--2019|Bistline and Young 2019]] ; [[#Perez--2019|Perez et al. 2019]] ), presents economic and technical challenges to electricity system management across different time scales from sub-seconds, hours, days, seasons, to multiple years. Furthermore, electrification of segments of the transport and heat sectors could disproportionately increase peak demand relative to supply ( [[#Bistline--2021|Bistline et al. 2021]] ). Increases in peak demand may require reinforcing network infrastructures and generation in the historical passive system operation paradigm ( [[#Strbac--2020|Strbac et al. 2020]] ).

These challenges to electricity system management can be addressed through system integration and a digitalised control paradigm involving advanced information and communication technologies. Real-time maintenance of supply-demand balance and sufficient flexibility technologies such as electricity storage, flexible demand, and grid forming converters (Strbac et al. 2015a; [[#López%20Prol--2021|López Prol and Schill 2021]] ) would be increasingly valuable for incorporating larger amounts of VRE generation. This flexibility will be particularly important to deal with sudden losses of supply, for example, due to a failure of a large generator or interconnector or a rapid increase in demand ( [[#Teng--2017|Teng et al. 2017]] ; [[#Chamorro--2020|Chamorro et al. 2020]] ).

The transition to a digitalised-based electricity system control paradigm would facilitate radical changes in the security of supply, moving from the traditional approach of redundancy in assets to a smart control paradigm. Advanced control and communication systems can significantly reduce the electricity system investment and operation costs ( [[#Harper--2018|Harper et al. 2018]] ; [[#Münster--2020|Münster et al. 2020]] ).

<div id="6.4.3.1" class="h3-container"></div>

<span id="importance-of-cross-sector-coupling-for-cost-effective-energy-system-decarbonisation"></span>
==== 6.4.3.1 Importance of Cross-sector Coupling for Cost-effective Energy System Decarbonisation ====

<div id="h3-11-siblings" class="h3-siblings"></div>

Integrated whole-system approaches can reduce the costs of low-carbon energy system transitions ( ''high confidence'' ). A lack of flexibility in the electricity system may limit the cost-effective integration of technologies as part of broader net-zero energy systems. At the same time, the enormous latent flexibility hidden in heating and cooling, hydrogen, transport, gas systems, and other energy systems provides opportunities to take advantage of synergies and to coordinate operations across systems (Martin et al. 2017; [[#Zhang--2018|Zhang et al. 2018]] ; [[#Martinez%20Cesena--2019|Martinez Cesena and Mancarella 2019]] ; [[#Pavičević--2020|Pavičević et al. 2020]] ; [[#Bogdanov--2021|Bogdanov et al. 2021]] ) (Figure 6.16).

<div id="_idContainer047" class="Basic-Text-Frame"></div>

[[File:555573938fc85caac59aa4d52f86200b IPCC_AR6_WGIII_Figure_6_16.png]]

'''Figure 6.16 | Interaction between different energy sectors.''' Source: extracted with permission from [[#Münster--2020|Münster et al. (2020)]] .

Sector coupling can significantly increase system flexibility, driven by the application of advanced technologies (Clegg and Mancarella 2016; [[#Heinen--2016|Heinen et al. 2016]] ; [[#Bogdanov--2019|Bogdanov et al. 2019]] ; [[#Solomon--2019|Solomon et al. 2019]] ; [[#Zhang--2019b|Zhang et al. 2019b]] ; [[#Zhang--2020|Zhang and Fujimori 2020]] ; [[#Zhao--2021|Zhao et al. 2021]] ). For example, district heating infrastructure can generate both heat and power. Cooling systems and electrified heating systems in buildings can provide flexibility through preheating and precooling via thermal energy storage (Z. [[#Li--2016|Li et al. 2016]] ; G. [[#Li--2017|Li et al. 2017]] ). System balancing services can be provided by electric vehicles (EVs) based on vehicle-to-grid concepts and deferred charging through smart control of EV batteries without compromising customers’ requirements for transport ( [[#Aunedi--2020|Aunedi and Strbac 2020]] ).

Hydrogen production processes (power-to-gas and vice versa) and hydrogen storage can support short-term and long-term balancing in the energy systems and enhance resilience (Stephen and Pierluigi 2016; [[#Strbac--2020|Strbac et al. 2020]] ). However, the economic benefits of flexible power-to-gas plants, energy storage, and other flexibility technological and options will depend on the locations of VRE sources, storage sites, gas, hydrogen, and electricity networks ( [[#Jentsch--2014|Jentsch et al. 2014]] ; [[#Heymann--2015|Heymann and Bessa 2015]] ; [[#Ameli--2020|Ameli et al. 2020]] ). Coordinated operation of gas and electricity systems can bring significant benefits in supplying heat demands. For example, hybrid heating can eliminate investment in electricity infrastructure reinforcement by switching to heat pumps in off-peak hours and gas boilers in peak hours ( [[#Fischer--2017|Fischer et al. 2017]] ; [[#Dengiz--2019|Dengiz et al. 2019]] ; [[#Bistline--2021|Bistline et al. 2021]] ). The heat required by direct air carbon capture and storage (DACCS) could be effectively supplied by inherent heat energy in nuclear plants, enhancing overall system efficiency ( [[#Realmonte--2019|Realmonte et al. 2019]] ).

Rather than incremental planning, strategic energy system planning can help minimise long-term mitigation costs ( ''high confidence'' ). With a whole-system perspective, integrated planning can consider both short-term operation and long-term investment decisions, covering infrastructure from local to national and international, while meeting security of supply requirements and incorporating the flexibility provided by different technologies and advanced control strategies ( [[#Zhang--2018|Zhang et al. 2018]] ; [[#O’Malley--2020|O’Malley et al. 2020]] ; [[#Strbac--2020|Strbac et al. 2020]] ). Management of conflicts and synergies between local district and national level energy system objectives, including strategic investment in local hydrogen and heat infrastructure, can drive significant whole-system cost savings ( [[#Zhang--2019b|Zhang et al. 2019b]] ; [[#Fu--2020|Fu et al. 2020]] ). For example, long-term planning of the offshore grid infrastructure to support offshore wind development, including interconnection between different countries and regions, can provide significant savings compared to a short-term incremental approach in which every offshore wind farm is individually connected to the onshore grid ( [[#E3G--2021|E3G 2021]] ).

<div id="6.4.3.2" class="h3-container"></div>

<span id="role-of-flexibility-technologies"></span>
==== 6.4.3.2 Role of Flexibility Technologies ====

<div id="h3-12-siblings" class="h3-siblings"></div>

Flexibility technologies – including energy storage, demand-side response, flexible/dispatchable generation, grid-forming converters, and transmission interconnection – as well as advanced control systems – can facilitate cost-effective and secure low-carbon energy systems ( ''high confidence'' ). Flexibility technologies have already been implemented, but they can be enhanced and deployed more widely. Due to their interdependencies and similarities, there can be both synergies and conflicts for utilising these flexibility options ( [[#Bistline--2021|Bistline et al. 2021]] ). It will therefore be important to coordinate the deployment of the potential flexibility technologies and smart control strategies. Important electricity system flexibility options include the following:

• '''Flexible/dispatchable generation.''' Advances in generation technologies, for example, gas/hydrogen plants and nuclear plants, can enable them to provide flexibility services. These technologies would start more quickly, operate at lower power output, and make faster output changes, enabling more secure and cost-effective integration of VRE generation and end-use electrification. There are already important developments in increasing nuclear plants flexibility (e.g., in France ( [[#Office%20of%20Nuclear%20Energy--2021|Office of Nuclear Energy 2021]] )) and the development of small modular reactors, which could support system balancing ( [[#FTI%20Consulting--2018|FTI Consulting 2018]] ).

'''•''' '''Grid-forming converters (inverters).''' The transition from conventional electricity generation, applying mainly synchronous machines to inverter-dominated renewable generation, creates significant operating challenges. These challenges are mainly associated with reduced synchronous inertia, system stability, and ‘black start’ capability. Grid-forming converters will be a cornerstone for the control of future electricity systems dominated by VRE generation. These converters will address critical stability challenges, including the lack of system inertia, frequency and voltage regulation, and black start services while reducing or eliminating the need to operate conventional generation ( [[#Tayyebi--2019|Tayyebi et al. 2019]] ).

'''•''' '''Interconnection.''' Electricity interconnections between different regions can facilitate more cost-effective renewable electricity deployment. Interconnection can enable large-scale sharing of energy and provide balancing services. Backup energy carriers beyond electricity, such as ammonia, can be shared through gas/ammonia/hydrogen-based interconnections, strengthening temporal coupling of multiple sectors in different regions ( [[#Bhagwat--2017|Bhagwat et al. 2017]] ; [[#Brown--2018|Brown et al. 2018]] ) ( [[#6.4.5|Section 6.4.5]] ).

'''•''' '''Demand-side response''' . Demand-side schemes – including, for example, smart appliances, EVs, and building-based thermal energy storage (Heleno et al. 2014) – can provide flexibility services across multiple time frames and systems. Through differentiation between essential and non-essential needs during emergency conditions, smart control of demands can significantly enhance system resilience ( [[#Chaffey--2016|Chaffey 2016]] ).

• '''Energy storage.''' Energy storage technologies ( [[#6.4.4|Section 6.4.4]] ) can act as both demand and generation sources. They can provide services such as system balancing, various ancillary services, and network management. Long-duration energy storage can significantly enhance the utilisation of renewable energy sources and reduce the need for firm low-carbon generation ( [[#Sepulveda--2021|Sepulveda et al. 2021]] ).

<div id="6.4.3.3" class="h3-container"></div>

<span id="role-of-digitalisation-and-advanced-control-systems"></span>
==== 6.4.3.3 Role of Digitalisation and Advanced Control Systems ====

<div id="h3-13-siblings" class="h3-siblings"></div>

A digitalised energy system can significantly reduce energy infrastructure investments while enhancing supply security and resilience ( ''high confidence'' ) ( [[#Andoni--2019|Andoni et al. 2019]] ; [[#Strbac--2020|Strbac et al. 2020]] ). Significant progress has been made in the development of technologies essential for the transition to a digitalised energy control paradigm, although the full implementation is still under development. Electrification and the increased integration of the electricity system with other systems will fundamentally transform the operational and planning paradigm of future energy infrastructure. A fully intelligent and sophisticated coordination of the multiple systems through smart control will support this paradigm shift. This shift will provide significant savings through better utilisation of existing infrastructure locally, regionally, nationally, and internationally. Supply system reliability will be enhanced through advanced control of local infrastructure (Strbac et al. 2015a). Furthermore, this paradigm shift offers the potential to increase energy efficiency through a combination of technologies that gather and analyse data and consequently optimise energy use in real-time.

The transition to advanced data-driven control of energy system operations ( [[#Cremer--2019|Cremer et al. 2019]] ; [[#Sun--2019a|Sun et al. 2019a]] ) will require advanced information and communication technologies and infrastructure, including the internet, wireless networks, computers, software, middleware, smart sensors, internet of things components, and dedicated technological developments ( [[#Hossein%20Motlagh--2020|Hossein Motlagh et al. 2020]] ). The transition will raise standardisation and cyber-security issues, given that digitalisation can become a single point of failure for the complete system ( [[#Ustun--2019|Ustun and Hussain 2019]] ; [[#Unsal--2021|Unsal et al. 2021]] ). Implementing peer-to-peer energy trading based on blockchain is expected to be one of the key elements of next-generation electricity systems ( [[#Qiu--2021|Qiu et al. 2021]] ). This trading will enable consumers to drive system operation and future design, increasing overall system efficiency and security of supply while reducing emissions without sacrificing users’ privacy ( [[#Andoni--2019|Andoni et al. 2019]] ; [[#Ahl--2020|Ahl et al. 2020]] ). When deployed with smart contracts, this concept will be suitable for energy systems involving many participants, where a prerequisite is digitalisation (e.g., smart meters, end-use demand control systems) (Juhar and Khaled 2018; [[#Teufel--2019|Teufel et al. 2019]] ).

<div id="6.4.3.4" class="h3-container"></div>

<span id="system-benefits-of-flexibility-technologies-and-advanced-control-systems"></span>
==== 6.4.3.4 System Benefits of Flexibility Technologies and Advanced Control Systems ====

<div id="h3-14-siblings" class="h3-siblings"></div>

New sources of flexibility and advanced control systems provide a significant opportunity to reduce low-carbon energy system costs by enhancing operating efficiency and reducing energy infrastructure and low-carbon generation investments, while continuing to meet security requirements ( ''high confidence'' ). In the USA, for example, one study found that flexibility in buildings alone could reduce US CO 2 emissions by 80 Mt yr –1 and save USD18 billion yr –1 in electricity system costs by 2030 ( [[#Satchwell--2021|Satchwell et al. 2021]] ). Key means for creating savings are associated with the following:

• '''Efficient energy system operation.''' Flexibility technologies such as storage, demand-side response, interconnection, and cross-system control will enable more efficient, real-time demand and supply balancing. This balancing has historically been provided by conventional fossil-fuel generation ( [[#Nuytten--2013|Nuytten et al. 2013]] ).

'''•''' '''Savings in investment in low-carbon/renewable generation capacity.''' System flexibility sources can absorb or export surplus electricity, thus reducing or avoiding energy curtailment and reducing the need for firm low-carbon capacity such as nuclear and fossil-fuel plants with CCS ( [[#Newbery--2013|Newbery et al. 2013]] ; [[#Solomon--2019|Solomon et al. 2019]] ). For example, one study found that flexibility technologies and advanced control systems could reduce the need for nuclear power by 14 GW and offshore wind by 20 GW in the UK’s low-carbon transition ( [[#Strbac--2015b|Strbac et al. 2015b]] ).

'''•''' '''Reduced need for backup capacity.''' System flexibility can reduce energy demand peaks, reducing the required generation capacity to maintain the security of supply, producing significant savings in generation investments ( [[#Strbac--2020|Strbac et al. 2020]] ).

• '''Deferral or avoidance of electricity network reinforcement/addition.''' Flexibility technologies supported by advanced control systems can provide significant savings in investment in electricity network reinforcement that might emerge from increased demand, for example, driven by electrification of transport and heat sectors. Historical network planning and operation standards are being revised considering alternative flexibility technologies, which would further support cost-effective integration of decarbonised transport and heat sectors ( [[#Strbac--2020|Strbac et al. 2020]] ).

<div id="6.4.4" class="h2-container"></div>

<span id="energy-storage-for-low-carbon-grids"></span>