能源转型时代的能源网络(英)-牛津能源研究所.pdf

May 2022 OIES Paper: EL 48 Energy Networks in the Energy Transition Era Rahmatallah Poudineh, Senior Research Fellow, OIES i The contents of this paper are the author’s sole responsibility. They do not necessarily represent the views of the Oxford Institute for Energy Studies or any of its members. Copyright © 2022 Oxford Institute for Energy Studies (Registered Charity, No. 286084) This publication may be reproduced in part for educational or non-profit purposes without special permission from the copyright holder, provided acknowledgment of the source is made. No use of this publication may be made for resale or for any other commercial purpose whatsoever without prior permission in writing from the Oxford Institute for Energy Studies. ISBN 978-1-78467-199-0 ii Abstract As infrastructures that connect the energy source with the energy use, energy networks constitute a crucial element of national and global energy systems. They also play a key role in helping with balancing supply and demand, thus ensuring that energy is not only available in the right places but also at the right time. Energy transition will have significant impacts, though not necessarily in the same way, on existing energy networks, for example, electricity and natural gas grids, and might lead to the growth of new energy carrier systems, such as district heating and cooling and the deployment of new infrastructures to support the use of hydrogen. Understanding the implications of energy transition for energy networks, and the ways in which these infrastructures should adapt to the challenges of decarbonization, is important to achieve net-zero carbon objectives. This paper explores some of the key issues faced by electricity transmission and distribution networks; natural gas networks; and future hydrogen, heating, and cooling networks in the transition of energy systems. Also, as future decarbonized energy systems are likely to exhibit significantly more interaction between different parts of the system, this paper explores possible approaches to utilizing the synergies between energy networks and benefiting from their integrated operation to lower the costs and challenges of decarbonization. iii Contents Abstract . ii Figures . iii Tables . iii 1. Introduction . 1 2. Energy networks . 2 2.1 Electricity transmission networks 2 2.1.1 The effect of market design 5 2.1.2 Electricity distribution networks . 5 2.2 Natural gas networks 8 2.3 Hydrogen network . 11 2.4 Heating and cooling networks . 12 3. Integrated energy networks. 16 4. Summary and conclusions 19 References 22 Figures Figure 1: Natural gas in primary energy in global whole energy system scenarios that meet a 1.5°C warming target. . 9 Figure 2: Yearly heat demand in the UK across sectors (2019) . 13 Figure 3: Global energy consumption for space cooling in buildings 15 Figure 4: Share of heating/cooling demand met through district energy systems in selected countries 15 Figure 5: Three layers of an integrated approach to network planning and operation 17 Figure 6: Illustrative possible interactions between different energy networks in the UK . 18 Tables Table 1: Transformation of the electricity system and its implications 3 Table 2: An example of a transmission constraint and the range of possible solutions 4 1 The contents of this paper are the author’s sole responsibility. They do not necessarily represent the views of the Oxford Institute for Energy Studies or any of its Members. 1. Introduction Energy networks are infrastructures that connect the energy source with the energy use and thus constitute a crucial element of national and global energy systems. Over the last hundred years, the networks (especially electricity and gas) have evolved from local simple grids into complex infrastructures that transfer energy not only within national boundaries but also across borders in a reliable and efficient manner. The net-zero carbon target will result in a significant change in energy systems with significant implications for existing energy networks. It may also lead to the growth of new energy carrier systems, such as district heating and cooling, and potentially give rise to new infrastructure to support the delivery and use of hydrogen. The electricity networks, in particular, are facing significant changes as a result of the transformation currently under way in the energy system. Electricity is the fastest growing consumer energy because of the role that it is expected to play in the decarbonization of the transport, building and industrial sectors. Traditionally, electricity was generated in large centralized thermal or hydro power plants, which feed into a transmission grid that connects industrial loads and supplies smaller consumers through distribution grids (IEA, 2021). The design of transmission grids was such that power flows between power plants and main consumption centres within a specific region were easily accommodated without structural congestion. However, renewable energy resources such as onshore wind farms, utility-scale solar facilities, and offshore wind farms are often located far from load centres, while thermal generation plants are either being phased out or forced out of the market by cheap renewables. At the same time, there is a huge growth in smaller distributed energy resources (DERs) on the distribution grid. These developments will change the flow pattern within the electricity networks and may create new constraints, and thus necessitate more efficient utilization of existing grid assets, new grid investments, and in some cases even new overall grid and electricity market designs. The rise of DERs, and the decentralization paradigm in particular is upending the balance between the electricity transmission and distribution sectors. Distribution grids, which have historically been passive and addressed grid constraints through overengineering, are now becoming more active. Along with the need for new rules, this also means new roles for distribution system operators (DSOs) to facilitate efficient integration of DERs while achieving a higher level of coordination with the transmission system operator (TSO). This is to improve visibility and control over DERs and avoid potential conflict between DSOs and the TSO. Apart from electricity, natural gas is another major energy network in many countries. However, the future of the natural gas grid is uncertain, especially at the low-pressure distribution level. It partly depends on future energy service scenarios in which natural gas is primarily used, for example, for heating, and partly on the technological progress made to lower the costs of carbon capture and storage. The use of natural gas networks must change if these networks are to play a role under the net-zero carbon objective. Low-carbon alternatives such as hydrogen are a potential replacement for natural gas but a range of challenges exists. For example, as the share of natural gas declines, available volumes of hydrogen may not be sufficient to justify adjusting the existing natural gas infrastructures. Also, hydrogen can be transported not only via a repurposed gas network (or new pipeline), but also via available power and transportation networks, such as by rail, road, and on waterways. This means that, despite the efficiency of pipelines, repurposing the gas network might not always be the optimal solution. There are other energy networks emerging to address the challenges of decarbonizing the heating and cooling sectors. Heat networks currently have little energy demand market share globally but, given their advantage over individual heating systems and also the growing urgency of decarbonizing heating in the building sector, their share is expected to increase. In the UK, for example, the energy demand 2 The contents of this paper are the author’s sole responsibility. They do not necessarily represent the views of the Oxford Institute for Energy Studies or any of its Members. for heating accounts for more than 40 per cent of all energy use and contributes to around one-third of carbon emissions. Under favourable regulatory and policy conditions, district heating could become the main method of providing heat to buildings in high-density built environments, such as city centres and campuses, as well as some rural off-gas grid communities in this country. Cooling networks are less common compared with district heating, but with the rise in demand for space cooling in the Global South these networks may also gain more importance. In the United Arab Emirates, district cooling currently provides more than one-fifth of the cooling load (IRENA, 2017b). The economies of scale and increased efficiency of providing centralized space cooling, compared with individual air-conditioning systems, can reduce their costs significantly. Similar to district heating, district cooling also requires appropriate policies and regulations to facilitate its deployment in places with high- load density. As energy systems become more complex due to decarbonization, decentralization and digitalization trends, the importance of energy networks as critical infrastructures that exploit and facilitate temporal and spatial diversity in energy production and consumption increases. It is thus necessary to understand how best to design, regulate, integrate and operate existing and emerging energy networks in order to benefit the entire energy system. Currently, energy networks, whether they be electricity, gas, heating or cooling, are commonly planned and operated independently, which results in a loss of synergies and efficiency (Hosseini, 2020). These separate infrastructures are now increasingly becoming interconnected through network coupling technologies, such as combined cycle gas turbines (CCGT); combined heat and power units (CHP); and power-to-X technologies, such as hydrogen, ammonia, heating, cooling, and heat pumps. An integrated approach to the planning and operation of these networks can lower the use of primary energy, provide flexibility to integrate variable renewable energy resources and lower the cost of achieving a net-zero target. This however entails addressing a range of operational, regulatory, and governance issues.1 The outline of this paper is as follows: Section 2 discusses issues which individual energy networks are facing during the energy transition, starting with electricity transmission and distribution grids then going on to natural gas and hydrogen grids and finishing with heating and cooling networks. Section 3 discusses the idea of an integrated energy network. Finally, Section 4 provides a summary and conclusions. 2. Energy networks Energy networks are infrastructures that transfer energy from the production source to the consumers’ premises. They constitute various forms of technologies ranging from established networks, such as electricity and natural gas, to emerging grids, such as hydrogen, heating, and cooling. In this section, we briefly review each of these networks and highlight the challenges and opportunities they face as a result of the energy transition. 2.1 Electricity transmission networks As we move towards a net-zero carbon economy, the electricity sector is experiencing a profound transformation (BEIS, 2021a). On the supply side, the rise of renewable energy resources has led to power generation becoming increasingly variable and uncertain while the penetration of DERs implies a shift of value from transmission to the distribution level due to decentralization. On the demand side, electricity demand is not only expected to rise, due to the increased electrification of activities and processes, but may also become more uncertain because of the nature of newly electrified activities 1 These include economic issues, such as coordination in the presence of fragmented institutional and market structures of different energy systems, as well technical challenges, such as preventing cascading failures, lowering vulnerability, and improving the resilience of integrated energy networks (Taylor et al., 2022). 3 The contents of this paper are the author’s sole responsibility. They do not necessarily represent the views of the Oxford Institute for Energy Studies or any of its Members. (for example, electric vehicles can potentially charge at any time and at any location on the network). In addition, network users are becoming more active as digitalization and automation lower the transaction costs of interacting with the electricity system. These all have implications for the entire electricity system, including the network infrastructure (see Table 1). Table 1: Transformation of the electricity system and its implications Transformation of the power system Generation  Variable and uncertain renewable generation  Distributed energy resources  Energy storage Electricity demand  The rise of electricity consumption (e.g. data centres, electric vehicles, heat pumps, air-conditioning)  Increase in uncertainty of demand Network users  Active network users (e.g. prosumers, energy communities) Communication and control  Digitalization and automation Implications for the power system Initial focus Present focus Planning Renewable generation Capacity growth System interaction, integration costs Network infrastructure Sufficient capacity to accommodate all users Market-based and differentiated grid access regime, competition, cost allocation, coordination with generation Operation Reliability and operational security Through energy-only market Search for new paradigm Flexibility From conventional power plants New solutions (e.g. DERs, demand response, energy storage) and new incentives and frameworks for flexible services Source: author Indeed, a different electricity network is needed compared to what we had in the past. Electricity networks require higher capacity and interconnections as well as more efficient approaches to cater for the rise in the electricity demand and the increased complexity and challenge in a system balancing supply and demand. Although decentralization implies that an increasingly higher proportion of generation facilities are located on the distribution side, significant investment in the transmission networks is still required due to the diverse geographical location of new major resources, such as onshore and offshore wind farms, as well as the increased need for interconnectivity between electricity markets. There are two important points when it comes to expanding the transmission grid. First, the design and construction of new transmission assets is a complex and costly process with a long lead time. Second, there is still uncertainty about the timing and pace of decarbonization of heating and transport as well as the extent to which electrification can outcompete alternative options in all applications of these services. This suggests that future network investments need to be rob