Abstract

A novel combined heat and power (CHP) system based on solar photothermal methane dry reforming is proposed. Methane is reformed with carbon dioxide by a combination of light and heat to produce syngas. Compared to traditional solar thermochemical reforming, which requires a reaction temperature as high as 900 °C, photothermal reforming has been demonstrated to be performed at much lower temperatures. Solid oxide fuel cell (SOFC) and micro gas turbine (MGT) are combined for power generation, while the waste heat is used to supply domestic hot water (DHW). The energy and exergy efficiencies of the novel CHP system reach up to 86.8% and 47.3%, respectively. For the same share of solar energy, the net solar power generation efficiency of the system based on photothermal reforming is 17.8%, which is significantly higher than that of the system based on thermochemical (9.1%). Finally, the Energy Utilized Diagram (EUD) is applied to analyze the exergy destruction of the SOFC, where the main exergy destruction occurs.

Abstract

This paper designs a combined cooling, heating and power system based on the complementary conversion of solar energy and natural gas. An operation strategy based on the energy storage characteristics of the system is developed. The performance of the system under the new operation strategy is evaluated based on three indicators including the operation cost saving rate, the carbon dioxide emission reduction rate and the relative energy saving rate. The annual system performance is analyzed on typical days throughout different seasons. The results show that the developed operation strategy can achieve significant improvements in energy efficiency and economic benefits. Compared to the reference system, the designed system achieves considerable annual cost saving, CO2 emission reduction rate and relative energy saving rate of 15.12%, 31.51% and 28.52%, respectively. These promising results provide guidance for the integrated design and operational regulation of solar and fuel complementary systems.

Abstract

A sustainable city strategy is crucial to combat climate change, as buildings contribute significantly to carbon emissions and energy source depletion. Buildings account for 30% of greenhouse gas emissions, 40% of energy consumption, 25% of water, and 40% of resource use. A sustainable city strategy involves retrofitting existing buildings to make them green and energy-efficient by reducing carbon emissions and promoting a more sustainable future. However, developing countries like Sri Lanka are reluctant to adopt energy-efficient retrofitting solutions due to several factors, including a lack of awareness and misconceptions about the costs outweighing the benefits over the building’s life cycle. To dispel these misconceptions, this paper aims to establish a comprehensive analysis framework to guide stakeholders in setting an optimal technical combination of energy-efficient retrofit measures for a selected commercial building in Sri Lanka. DesignBuilder software is used to simulate energy performance by analyzing technical features such as insulation, shading, and lighting. The optimal configuration for assessing its environmental and economic impact is determined through life cycle analysis, energy performance assessment, and cost-benefit analysis, integrated with carbon taxing and future energy price scenarios. This study reveals that the optimal retrofitting of buildings could reduce total energy consumption by around 26.79%, environmental impact by around 25% and their payback period was around 17.33 years, while LED lighting has the highest impact on energy efficiency, cost-effectiveness, and environmental impact on the building, while retrofitting the building envelope also brings considerable environmental impact and around 7% energy saving. Furthermore, this study demonstrates that insulation is less efficient in Warm-Humid and Warm-Dry environments than in other area types. This framework for sustainable-comprehensive analysis provides theoretical and practical support and can serve as a reference for future studies on different scenarios.

Abstract

Under the current urgent global demand for clean energy and energy security, proton exchange membrane fuel cell (PEMFC) cogeneration systems have attracted much attention and research. The purpose of this paper is to provide a comprehensive overview of the various aspects of fuel cell cogeneration systems, including the composition of the system, the thermal management technology, the composition of the waste heat recovery system, the control strategy, and the form of integration with other energy systems. Through an in-depth analysis of the system components and operation principles, the role and potential of fuel cell cogeneration systems in the energy transition can be better understood.

Abstract

During the initial phases of the energy transition, blending hydrogen into operational natural gas pipelines proves to be an efficient method for hydrogen delivery. Nevertheless, the blending of hydrogen raises the reactivity of the gas and escalates the fire hazard. A jet fire occurs when a leakage and accidental ignition of a hydrogen/natural gas mixture within a pipeline. Flame length, as one of the key parameters to measure fire safety, is of great significance for evaluating the impact range of fire. A numerical model of horizontal jet fire of hydrogen-blended natural gas, including hydrogen content of 0%, 10%, 20%, 50% and 100%, is established to analyze the effect of hydrogen on flame length from the perspective of combustion intermediate. The research results may provide reference for the risk assessment of hydrogen-blended natural gas pipelines.

Abstract

Compared with the compressed air energy storage system, energy storage system with CO2 as working fluid has the advantages of high energy storage density and compactness. In this paper, a novel isobaric compressed CO2 energy storage system with a flexible gas holder is proposed. The thermodynamic modeling of the compressed CO2 energy storage system is established and the impact of some key parameters on system performance is studied. The results show that round-trip efficiency gradually increases from 67.86% to 77.00% as the compressor isentropic efficiency rises from 75% to 95%. As the relative pressure loss rate of the heat exchanger increases from 0.25% to 4.5%, the system round-trip efficiency experiences a decline from 73.12% to 71.49%.

Abstract

Under suitable temperature and pressure conditions, CO2 can combine with water to form solid CO2 hydrates. Hydrate-based CO2 sequestration in subsea sediments is an alternative option to mitigate global warming. In this work, we developed novel simulation codes and simulated CO2 sequestration processes in subsea sediments based on site W19 in the Shenhu area. The results show that CO2 hydrate massively forms after the end of injection and gradually expands into low-permeability cap that can stably exists for 100 years. The hydrate cap greatly restricts upward migration of liquid CO2, forcing it to gradually transform into dissolved phase and hydrate phase, which makes hydrate-based CO2 sequestration feasible. Permeability, salinity, thermal conductivity of the formation and CO2 injection rate all have significant impacts on the sequestration performance, which provides guidance for site selection and optimization of injection scheme.

Abstract

This work introduces a regional energy model, emphasizing the importance of localized approaches to sustainability. It highlights the significance of energy system models in guiding the energy transitions policies, underscoring the influence of open science on advancing modelling techniques. The open-source energy models can play an important role in developing regional frameworks, which offer more precise insights into the characteristics and challenges of specific areas. The paper introduces TEMOA-Piedmont, the first energy system model of the Piedmont region in Italy, developed within the TEMOA optimization tool. The model aims to bridge national and regional energy policies by providing a detailed analysis of the region’s energy structure. The presented results focus on the transport sector, highly impacting the urban environments within the Piedmont region (e.g., the city of Turin) and object of the energy policies due to its criticality for the region. Developed based on totally publicly available data, TEMOA-Piedmont offers a valuable tool for policymakers and stakeholders to step towards a sustainable energy future tailored to the Piedmont region’s needs.

Abstract

Along with the rapid evolution of intelligent transportation systems (ITS) and network technology, vehicles have access to richer traffic data, paving the way for more efficient driving controls now. A novel hierarchical eco-driving strategy which is tailored specifically for hybrid electric truck navigating complex multi-intersection scenarios is proposed. Initially, a simulation scene is designed to simulate realistic truck-following scenarios. Subsequently, an upper-layer truck-following strategy is devised utilizing the safe off-line deep deterministic policy gradient(SDDPG) algorithm. This strategy is fully use of insights from leading vehicles and traffic signal data. Specifically, logical judgement module considering safety constraints are integrated into training processing to minimize collision risks. In addition, safe reward function is set to direct the agent to learn the safer action. Moving to the lower layer, an energy management strategy is proposed using deep reinforcement learning (DRL) techniques. A unique reward shaping function is introduced to guide the learning process effectively. Ultimately, the proposed methodology demonstrates a remarkable fuel-saving rate of 97.46% compared to dynamic programming (DP) approach by simulation.

Abstract

Ensuring energy security is one of the main objectives of energy policies of many countries worldwide. In this regard, this paper proposes a metric to evaluate energy security under medium-to-long term energy scenarios generated by the TEMOA-Italy model. Such a metric consists of an energy security index covering several dimensions of energy security. Among them, the inclusion of the supply risk of critical raw materials represents a novelty, compared to the existing literature. Moreover, critical raw materials are crucial for the decarbonization of urban energy systems, for instance through smart cities and vehicles to grid strategies. The analysis here shows how the penetration of low-carbon technologies can provide significant benefits to energy security, while their dependence on critical raw materials could represent a bottleneck for the evolution of the energy system. Accordingly, the metric presented in this paper can provide relevant policy insights on the effects of the transition from fossil fuels to low carbon sources on energy security.