Low-carbon Energy System Research Articles

The prospect of natural gas hydrate (NGH) under the vision of Peak Carbon Dioxide Emissions in China

To achieve the goals of Peak Carbon Dioxide Emissions and Carbon Neutrality, China's energy system will continue to accelerate the transition to a clean and low-carbon one. As the cleanest fossil fuel, natural gas is regarded as an inevitable choice for China to build a clean, safe, efficient, and low-carbon energy system and fulfill the goal of “double carbon”. However, the domestic conventional natural gas supply remains rigid while the stimulation of unconventional natural gas is still limited. If we have a firm grip on the principal line of “understanding the ocean -- developing resources -- ensuring security” to realize the large-scale development of 85 trillion square meters of NGH in the South China Sea, then we could not only greatly reduce China ‘s foreign dependence on natural gas, but also guarantee the safety of China ‘s natural gas multi-path supply and safeguard the sovereignty of the South China Sea. Thus, the goal of Peak Carbon Dioxide Emissions and Carbon Neutrality can be achieved in no time.

Contemplation on China’s Energy-Development Strategies and Initiatives in the Context of Its Carbon Neutrality Goal

Abstract Climate change has become a global non-traditional security challenge.There is a long way to go for China's energy structure to go through a green and low-carbon transition.As the key to “peak carbon emissions and achieve carbon neutrality”, the energy industry should have a comprehensive understanding of the general trend of the world’s energy transition and be fully aware of China’s resource endowment which is “enriched coal, insufficient oil and gas, and abundant new energy”.It should firmly adhere to energy saving and efficiency improvement, insist on supply and demand coordination, strengthen the top-level design, implement energy saving projects, decarbonization projects, innovation projects, efficiency improvement projects, emergency response projects and support projects.Efforts should also be given to the acceleration of energy consumption structure transformation from coal-oriented (with oil, gas and new energy accounting for less than 20% respectively while coal over 50%) to new-energy-oriented ( with coal, oil and gas accounting for less than 20% respectively while new energy over 50%). Speed up the construction of a clean, lowcarbon, safe and efficient smart energy system.

Energy transition or transformation? Power and politics in the European natural gas industry’s trasformismo

This paper explores how established natural gas interests responded to climate action in the European Union. Climate policy was initially not anticipated to reduce the role of natural gas in the energy system, if anything, many presumed that it would come to play a larger role. It was widely understood to be the transition fuel, entailing that it could substitute more carbon-intensive source-fuels, such as coal, as society decarbonises. This narrative complemented natural gas industry incumbents’ other forms of power, including their control over resources, infrastructure, and involvement in the policy-making process. Drawing on these, they presumed that their future was ensured in the shift towards a low carbon energy system. As the EU enhanced climate targets, incumbents were forced to adapt the fuel’s discourse according to the changing context. Incumbents deployed their material, organisational, and discursive power to extend the status quo and accommodate pressure to enact far-reaching change – a process Gramsci refers to as trasformismo. By tracing the natural gas industry’s response to climate action, this paper shows how incumbents draw upon their fuel-specific bases of power and it explores the importance of discourses in shaping the trajectory of the energy transition.

Towards a multi-scalar and multi-horizon framework of energy injustice: A whole systems analysis of Estonian energy transition

The shift from carbon-intensive to low-carbon energy systems has profound justice implications as some regions are likely to lose as much as gain from decarbonization processes. Increasing calls have been made to adopt a ‘whole systems’ perspective on energy justice. Drawing on the Multi-level Perspective on socio-technical transitions this paper presents a new comprehensive framework of energy justice in system innovation, proposing to map injustices along three dimensions: 1) multiple spatial scales (regional, national, international); 2) different time horizons (currently experienced vs. anticipated injustices); 3) connections to transition dynamics (injustices related to the optimization of the currently dominant system, destabilization of the incumbent system or the acceleration of alternative solutions in niches). The framework is applied to analyse the ongoing energy transition in Estonia, involving interactions between the incumbent oil shale based regime and wind, solar, nuclear and bioenergy as emerging niche challengers. The content analysis of news items in Estonian media reveals an inventory of 214 distinct incidents of energy injustices across 21 different categories. We find that many experienced and anticipated injustices are deployed, often strategically, by certain actors to advocate specific energy futures and to influence current political choices. From the justice perspective our analysis thus raises a question whether it is ethical to use probable yet currently unrealized injustices related to regime destabilization and niche acceleration as a means to perpetuate injustices related to the optimization of the currently dominant regime.

Carbon Pricing and Complementary Policies—Consistency of the Policy Mix for Decarbonizing Buildings in Germany

While it is widely acknowledged that carbon pricing plays an important role in driving the transition towards a low-carbon energy system, its interaction with complementary instruments is discussed controversially. The analysis of combining carbon pricing with complementary policies has been mostly focused on the electricity sector, while the role of carbon pricing in the buildings sector has received only minor interest. In view of the newly introduced carbon pricing scheme for the buildings and transport sector in Germany, we analyze the interactions between the carbon pricing scheme with the existing policy instruments and assess the consistency of the policy mix for decarbonizing the buildings sector. Our analysis finds that the introduction of carbon pricing has a reinforcing effect on the instrument mix and adds to the consistency of the policy mix. The results highlight the importance of complementary policies in order to achieve deep decarbonization in the buildings sector. We conclude that carbon pricing, preferably implemented as a tax with a predictable and increasing price level, needs to be supplemented with a powerful mix of complementary measures.

Enabling Power System Transformation Globally: A System Operator Research Agenda for Bulk Power System Issues

The primary objective of a power system is to safely provide reliable energy services to society at an affordable cost. In many countries, this objective has been supplemented by another: meeting the energy demand with sustainable resources, which has culminated in the energy transition to low-carbon and zero-carbon energy systems. This transition, occurring rapidly around the world, is characterized by the increasing penetration of variable renewable energy (VRE), inverter-based resources (IBRs), and distributed energy resources (DERs).

Experiment strategy for evaluating advanced building energy management system

Buildings are envisioned to play an active role in future low-carbon energy systems. The complexity of building energy management systems increases as they interface more and more subsystems and domains. As an important step to achieve a higher technology readiness level, these energy management systems need to be systematically tested in real-life conditions. Currently, there are no standard testing and experiment strategies in buildings to handle the mentioned complexity. Additionally, the levels of details reported in the existing experimental studies are heterogeneous. This paper summarizes an application of a holistic testing method to a flexible fully-equipped prosumer with the goal of facilitating test preparation, execution, replication, and comparison. Several empirical suggestions are provided, and a hybrid quantification strategy with digital twins is presented.

Incorporation of wind power probabilities into long-term energy system development analysis using bottom-up models

For future low-carbon energy systems with high shares of renewable energy, temporal representation becomes the dominant factor that impacts the model outputs and analysis conclusions; therefore, relevant and complex modelling approaches are required. We present and apply specific methodology for modelling wind power plants in long-term planning models. It is based on wind power probability curves for each time slice and use of the semi-dynamic method for temporal aspect. Benefits of this approach include the representation of wind power extremes, correct address of balancing capacities and costs, partially retained chronology. We also evaluated the quantitative effect of this methodology on the results of the energy model. In determining the reasonable number of approximation steps for wind power probability curves, we found that a three-step approximation is sufficient to ensure the accuracy of model results.

Renewable energy and biological conservation in a changing world

Without a shift to renewable energy sources, climate change will have adverse effects on many terrestrial and aquatic species. On the other hand, replacing fossil fuels with renewable energy will have different effects on wildlife, some negative. To protect biota, while navigating the complexities surrounding the transition to renewable energy, will require sharing knowledge between energy experts and wildlife experts, as well as policy makers and resource managers. This special issue is intended to advance the conversation. Interactions between renewable energy facilities and fauna are complex. Each source of renewable energy has its own conservation concerns, and each presents its own set of opportunities for mitigation; Other concerns and mitigations are shared. In this overview, we review climate risks to biota, clarify the complementarities among renewables for the conservation community, and summarize research on energy effects on biota for the energy community. The papers invited for this special issue address fossil (coal, oil, natural gas) and renewable energy (terrestrial biomass energy, hydropower, marine-hydrokinetic energy, wind energy, solar energy) and affected fauna. We hope that the results of these studies, and others like them, set us on a path toward low-carbon energy systems that provide society with energy while protecting future biodiversity.

Assessing Uncertainties of Life-Cycle CO2 Emissions Using Hydrogen Energy for Power Generation

Hydrogen and its energy carriers, such as liquid hydrogen (LH2), methylcyclohexane (MCH), and ammonia (NH3), are essential components of low-carbon energy systems. To utilize hydrogen energy, the complete environmental merits of its supply chain should be evaluated. To understand the expected environmental benefit under the uncertainty of hydrogen technology development, we conducted life-cycle inventory analysis and calculated CO2 emissions and their uncertainties attributed to the entire supply chain of hydrogen and NH3 power generation (co-firing and mono-firing) in Japan. Hydrogen was assumed to be produced from overseas renewable energy sources with LH2/MCH as the carrier, and NH3 from natural gas or renewable energy sources. The Japanese life-cycle inventory database was used to calculate emissions. Monte Carlo simulations were performed to evaluate emission uncertainty and mitigation factors using hydrogen energy. For LH2, CO2 emission uncertainty during hydrogen liquefaction can be reduced by using low-carbon fuel. For MCH, CO2 emissions were not significantly affected by power consumption of overseas processes; however, it can be reduced by implementing low-carbon fuel and waste-heat utilization during MCH dehydrogenation. Low-carbon NH3 production processes significantly affected power generation, whereas carbon capture and storage during NH3 production showed the greatest reduction in CO2 emission. In conclusion, reducing CO2 emissions during the production of hydrogen and NH3 is key to realize low-carbon hydrogen energy systems.

Transition towards solar Photovoltaic Self-Consumption policies with Batteries: From the perspective of distribution networks

The transition towards low-carbon energy systems requires increasing the contribution of residential Photovoltaic (PV) in the energy consumption needs (i.e., PV self-consumption). For this purpose, the adoption of PV self-consumption policies as alternatives to the current net-metering policy may support harnessing batteries to improve PV self-consumption. However, the technical impacts of PV policies on distribution networks have to be adequately assessed and mitigated. To do so, a two-stage planning framework is proposed. The first stage is an optimization approach that determines the best sizes of PV and batteries based on the adopted PV policy. The second stage assesses the impacts of the resulting sizes on distribution networks using Monte-Carlo simulations to cope with uncertainties in demand and generation. The framework is applied on real medium and low voltage distribution networks from the south of Jordan. For the net-metering, the results show that the uptake of residential PV penetration above 40% will result in voltage issues. It is also found that the adoption of batteries for the benefits of customers (i.e., reduce electricity bills) will not mitigate the PV impacts for PV penetration above 60%. Further, the results demonstrate the important role of distribution network operators to manage the uptake of batteries for the benefits of customers and distribution networks. Network operators can support customers to adopt larger sizes of batteries to achieve the desired PV self-consumption in return of controlling the batteries to solve network issues. This facilitates the uptake of 100% PV penetration and improves PV self-consumption to 50%.

Cross-sector storage and modeling needed for deep decarbonization

Noah Kittner is an assistant professor in energy in the Department of Environmental Sciences and Engineering, Gillings School of Global Public Health and in the Environment, Ecology, and Energy Program at the University of North Carolina at Chapel Hill. His research examines the role of energy storage in the transition to low-carbon energy systems and deep decarbonization. Sergio Castellanos is an assistant professor in the Department of Civil, Architectural and Environmental Engineering at the University of Texas at Austin, where he leads the Rapid, Equitable & Sustainable Energy Transitions (RESET) Lab focusing on equitable pathways for decarbonized energy systems. Patricia Hidalgo-Gonzalez is an assistant professor in the Jacobs School of Engineering and an affiliate member in the Center for Energy Research at the University of California, San Diego. She is the director of the Renewable Energy and Advanced Mathematics Laboratory. She is one of the academic co-leads of the IEEE Power & Energy Society Task Force "Data-Driven Controls for Distributed Systems." Her research focuses on high penetration of renewable energy using optimization, control theory, and machine learning with safety guarantees. Daniel M Kammen is the James and Katherine Lau Distinguished Chair in Sustainability, and Chair of the Energy and Resources Group, Professor in the Goldman School of Public Policy, and Professor of Nuclear Engineering at the University of California, Berkeley. He has served as Chief Technical Specialist for Renewable Energy and Energy Efficiency at the World Bank, and Science Envoy in the US Department of State. His work is focused on the science and policy of decarbonization at scales from homes to villages to large utility-scale systems. He has been a Coordinating Lead Author for the IPCC since 1999. Sarah Kurtz is a Professor at the University of California Merced. She spent more than 30 years at the National Renewable Energy Laboratory studying multi-junction III-V solar cells, reliability of photovoltaic modules and systems, and other solar-related projects. She is now leading a study of the value of long-duration storage, funded by the California Energy Commission.

Quantification of the carbon intensity of electricity produced and used in Europe

The EU has a comprehensive legislation to facilitate the energy transition towards a low carbon energy system and achieve the EU’s Paris Agreement commitments for reducing greenhouse gas emissions. The European Green Deal is an integral part of the EU strategy for a sustainable and climate neutral economy by 2050. The decarbonisation of the power generation is essential to achieve the goal of decarbonising the energy and transport sectors. This paper presents a study conducted to quantify the carbon emissions associated to the production of electricity produced and used in European countries, based on a comprehensive methodology developed for this purpose. A spreadsheet model has been developed that considers the various sources for electricity generation, the type of plants, conversion efficiencies, upstream emissions and emissions from power plant construction, as well as the electricity trade. The results show the greenhouse gas emissions from the production and use of electricity in all European countries, revealing significant variations between countries. The carbon intensity of electricity shows a clear reduction trend since 1990, for most of the European countries. In the European Union, carbon intensity of electricity used at low voltage degreased from 641 gCO2eq/kWh in 1990 to 334 gCO2eq/kWh in 2019, and this trend is expected to continue in the coming years.

A short- and long-term prognostic associating with remaining useful life estimation for proton exchange membrane fuel cell

Proton exchange membrane fuel cell (PEMFC), as a promising power source, provides a feasible solution for clean and low-carbon energy systems. The durability problem restricts PEMFC application in some scenarios, which can be improved by the prognostic technology indirectly. This paper aims to develop a data-based method to implement the short-term and long-term prognostic simultaneously, and the developed long-term prognostic can be performed without future operation information. First, the short-term prognostics of five multi-step ahead forecasting strategies are proposed and compared based on a long short-term memory (LSTM) network. Results show that the multi-step input and multi-step output (MIMO) with LSTM strategy has a better performance in the short-term prognostics under the test conditions of the stationary and dynamic current. Then, the hyper-parameters of the prediction model are determined by an evolutionary algorithm. Furthermore, in the long-term prognostics regime, the variable-step long-term method is proposed and rectified by the short-term prognostics. Finally, the developed remaining useful life (RUL) prediction is compared with a model-based extended Kalman filter. The average root mean square error results for the short-term prognostics of two conditions are 0.00532 and 0.00538, respectively. The RUL estimations of two PEMFCs named FC1 and FC2 are given with 95% and 90% confidence intervals, respectively. Consequently, the proposed method can achieve acceptable accuracies in the short-term prognostic, the long-term prognostic, and the RUL prediction.

Impact of power-to-gas on the cost and design of the future low-carbon urban energy system

Power-to-gas technology has been proposed as one component for future energy systems facing decarbonization targets. This paper presents a power-to-gas focused open optimization model for studying cost efficient design and operation of future urban energy system. The model is able to distinguish the benefits of different configurations of power-to-gas by modelling several energy vectors, including electricity, heating, and cooling alongside with different plant components. The usefulness of the built multi-vector model is illustrated by a case study where the benefits of power-to-gas are studied in the context of a medium-sized Nordic city. The results show that the city is able to reach carbon neutrality with the help of power-to-gas. Power-to-gas provides cost savings by reducing the need of heat storages and transmission capacity. The savings are greatest when the emission reduction goal is high and transmission capacity expansion is expensive. Direct air capture appears as the superior carbon dioxide source when compared to post combustion capture from flue gases due to costs and annual availability. The case study shows no economic benefit for distributed power-to-gas.

In pursuit of diverse energy futures: The political economy of electricity in Senegal

In recent years, Senegal has proactively pursued the expansion of renewable energy generation, particularly from solar and wind. In addition to starting exploration of offshore liquefied natural gas, the expansion in renewable energy is posited as a way to help the country move toward low(er) carbon development, reduce dependence on volatile oil markets, and improve reliable (and especially rural) access to electricity. To achieve these objectives, the electricity sector has continuously undergone structural reforms to improve its financial viability and to achieve objectives around universal access to electricity, particularly by increasing private sector participation in electricity generation. Through the lens of “electricity capital,” this paper examines the implications of reforms in the electricity sector for processes of accumulation, in a context of efforts to improve environmentally sustainable development. It asks how capital in the electricity sector is constituted and operates in the Senegalese context, who has power in shaping how it operates, and how this has influenced the potential for achieving a fair and equitable transition to a low(er) carbon energy system. This paper draws on recent work in political ecology on energy transitions and emerging literature on the political economy of electricity, as well as on analysis of policy and technical documents and semi-structured interviews carried out with those involved in the energy sector between 2018 and 2020. Findings suggest that even though the Senegalese government has set clear objectives for the electricity sector that are based on principles of equity, environmental sustainability, and justice, the current power relations and financing arrangements taken on by the state and other actors active in the sector has, paradoxically, led to an approach that risks undermining these very principles.

Effects of depressurizing rate on methane hydrate dissociation within large-scale experimental simulator

Methane hydrate is the world’s largest hydrocarbon reservoir, and can be performed as an important “bridging” fuel to help the transformation of current energy situation to low-carbon energy system. High efficient scenarios of hydrate dissociation at the in situ environment is the primary prerequisite for successfully harvesting natural gas from hydrate reservoir. This work investigates the influences of depressurizing rate on methane hydrate dissociation within a large-scale hydrate simulator. Experimental cases with different depressurizing rates to dissociate water-saturated hydrate sample, which is the typical marine hydrate type, have been carried out in this study. Results indicate that gas production rate decreases with the improvement of the depressurizing rate, and increasing depressurizing rate is feasible for hydrate reformation during this period, suggesting that the depressurizing rate should not be too fast before the inner pressure decreases to equilibrium pressure corresponding to the in situ temperature. When the pressure decreases below the equilibrium pressure, the gas production rate, recovery, and heat transfer rate decline with the rising of depressurizing rate, whereas the lowest depressurizing rate cannot gain the highest gas production rate and recovery as well, demonstrating the optimal depressurizing rate existed in the depressurization stage. Mechanism analysis showed that the optimal depressurizing rate can be obtained when the fluid velocity victories in accordance with the heat transfer vector in the hydrate reservoir.

The open source electricity Model Base for Europe - An engagement framework for open and transparent European energy modelling

The transition to a low carbon energy system as laid out in the Paris Agreement and the European Green Deal presents challenges that involve society at all levels from planners to consumers. A key challenge is the communication across these levels. Tools to foster engagement and discussion between the different actors are open-source models with a low threshold for uptake. This paper presents the Open-Source electricity Model Base for Europe an electricity sector engagement model covering all member states of the EU, Norway, Switzerland and the United Kingdom. Built in OSeMOSYS and available on GitHub, the model provides a starting point into energy systems modelling and can be further developed in a collaborative manner. It enables non-experts to develop an understanding of energy systems models and energy planning. Thereby, it can serve as an engagement tool to carry the debate on the future of the European power system beyond the academy, which might contribute to finding societal consensus on how to decarbonise our energy system. The model allows dynamic power sector expansion analysis of the European power system till 2050. It can be used for scenario analysis and is expandable to other sectors to analyse the benefits of sector coupling.

Analyzing the spatio-temporal variation of the CO2 emissions from district heating systems with “Coal-to-Gas” transition: Evidence from GTWR model and satellite data in China

Understanding the spatio-temporal heterogeneous effects of socioeconomic and meteorological factors on CO2 emissions from combinations of different district heating systems with “Coal-to-Gas” transition can contribute to the development of future low-carbon energy systems that are efficient and effective. This work downscales city-level CO2 emissions to a 3 × 3 km2 gridded level in northern China during 2012 to 2018. By employing the Geographically and Temporally Weighted Regression (GTWR) model, nighttime light (NTL) data are adopted as a proxy of the level of urbanization, and the Temperature-Humidity-Wind (THW) Index is used as a proxy of meteorological factors in the downscaling model. The results show that, for more than 85% of the cities, urbanization significantly enhances the CO2 emissions of district heating systems, while the THW Index shows negative impacts on CO2 emissions. Significant spatial and temporal heterogeneity exists. The grids with the highest CO2 emissions from coal-fired boilers (grids with annual variation >0.59 Gg CO2/year) are mainly located in nonurban areas of the two megacities Beijing and Tianjin and also in the capital cities of each province. Urbanization has larger effects on the CO2 emissions of natural gas-fired boilers than of coal-fired boilers and combined heat and power (CHP). The average growth rate of CO2 emissions of gas-fired boilers in the urban areas of the study regions was approximately 4.7 times that of nonurban areas. The spatio-temporal heterogeneous impacts of urbanization on CO2 emissions should therefore be considered in future discussions of clean heating policies and climate response strategies.

Integrated electricity and gas system modelling with hydrogen injections and gas composition tracking

Despite the direct physical coupling between them, electricity and gas networks were traditionally modelled and operated independently. However, the heavy reliance on gas-fired generators to balance intermittent generation from renewable energy sources (RES), and the promising role of green hydrogen in decarbonising the natural gas system, have prompted a paradigm shift towards integrated electricity and gas system (IEGS) modelling. While many previous studies investigated the role of hydrogen in future low-carbon energy systems, a detailed assessment of hydrogen system integration into the electricity and gas transmission networks is still not addressed. Therefore, this paper presents a novel IEGS model with green hydrogen injections and gas composition tracking. The electricity system is modelled as a unit commitment model, formulated as a mixed-integer linear programming problem, and the gas system is modelled as a steady-state optimal gas flow (OGF). The developed model is demonstrated on two sets of case studies. The first case study validates the proposed OGF methodology on a small meshed gas test network, whereas the second case study demonstrates the applicability of the overall IEGS model with green hydrogen injection on the large-scale, real-world electricity and gas transmission networks of the state of Victoria (Australia). Results show that the proposed methodology can accurately capture the variations in gas flow direction while maintaining the hydrogen molar fraction within limits under hydrogen injections from multiple locations. Moreover, the amount of injected hydrogen not only depends on the level of RES curtailment, but also on local gas network constraints and local demand.