Abstract

China proposed a target to reach maximum CO2 emissions before 2030 and attain carbon neutrality by 2060 in 2020. As a system highly relying on fossil fuel, and at the same time, with the rapid growth of renewable energy, the power system in China has to face the challenges both from carbon emission reduction and stability of electric grid. It can be predicted that the future coal fired power plants has to frequently work in partial load conditions to contribute flexibility to the grid, and moreover, to recover its carbon emission through adopting CO2 capture technology. However, the partial load operation of power generation system will undoubtedly influence the CO2 capture unit, which may lead to the variation of CO2 capture ratio (CCR). Through investigating the interaction between power generation system and CO2 capture unit under partial load conditions, the aim of this paper is to evaluate the potential of CO2 emission reduction of a variable load power plant. The model of a coal-fired power plants with post-combustion CO2 capture had been setup via EBSILON and Aspen. The performance of MEA CO2 separation unit had been simulated. By quantitatively analyzing the performance of a typical coal fired power plants in partial load operation and further combining the CO2 capture unit with the power generation system, the operating characteristics of the CO2 capture unit in partial load operation are explored. The results indicate several factors including the pressure of extracted steam for reboiler, the CO2 concentration in the flue gas and the flow rate of flue gas, will impose the possible impact on CO2 capture unit. The extraction steam temperature and pressure of the power generation unit also decrease as the power load decreases. When the load depth falls below 50%, the pressure drops to a certain level that could not meet the requirements for the operation of the CO2 capture unit, the capture unit will cease operation. The opening of the steam extraction valves remains unchanged, and the operating parameters of the capture unit are not adjusted under power load variation conditions. As the power load decreases, the mass flow of flue gas decreases from 1148.72 kg/s at 100% load to 521.63 kg/s at 30% load, while the CO2 mass fraction in the flue gas decreases from 17.8% to 13.9%. These changes will undoubtedly affect the CO2 load in solvent. The three factors together reduced the CCR for treated gas from 90% at 100% load to 50.42% at 30% load. The practical CCR for a power generation unit in a period of real operation conditions is lower than design CCR for treated gas, which is 90% at 100% load. Conclusively, the factors influencing capture ratio on the power generation side, such as flue gas and steam parameters, are important factors in CCR changing.

Abstract

CO2 splitting driven by solar energy is a clean and promising approach for addressing the issue of CO2 emission and approaching the dual-carbon target. Here, a high-efficient solar CO2 electrolysis system containing photovoltaic (PV) cell, photon-enhanced thermionic emission cell (PETE), and solid oxide electrolysis cell (SOEC) is proposed. CO2 serves as cool fluid to decrease the temperature of PV cells for the enhancement of PV efficiency, and the heated CO2 by PV cells and PETE is fed into SOEC at a high temperature to decrease the Gibbs free energy utilized in electrolysis. The combination of PV cell and PETE can enlarge the temperature range for full solar spectrum utilization. Compared to H2O splitting in SOEC, CO2 splitting can convert more thermal energy with relatively low energy level into high-energy-level chemical energy. The system can reach the energy efficiency, exergy efficiency, and solar-to-fuel efficiency of 73.5%, 48.0%, and 33.3%, respectively. This research sheds light on high-efficient solar CO2 splitting system design with full solar spectrum utilization in a wide temperature range.

Abstract

Wind power is one of the fastest-growing renewable energy sources in the world because of its many advantages. Wind power also presents fundamental challenges in some regions of the world, which are being addressed through research and development projects. This study aims to design and analyze propeller wind turbine for low-speed regions especially in those frontier, outermost and least developed regions often referred to as 3T (terdepan, terluar, tertinggal) in Indonesia. An open-source numerical software tool for aerodynamic and structural analysis of wind turbines is used to design airfoils. Four different airfoil types are selected based on literature study which produced four turbine blades: S826 (Antasena 1.1), NACA 4412 (Antasena 1.2), NACA 4415 (Antasena 1.3), and SG6043 (Antasena 1.4). Through simulations and analysis, it is found that Antasena 1.4 (SG6043) is the most suitable airfoil for low wind speed conditions (3-5 m/s). The power output predictions for various wind speed classes indicate that Antasena 1.4 has the highest potential power output, meeting and even surpassing the target values in certain months. Numerical simulation of Antasena 1.4 shows best power coefficient (Cp) 0.5747. The results demonstrate the promising applicability of Antasena 1.4 as an airfoil profile for turbines operating under low wind speed conditions.

Abstract

Using the Gompertz method and the elastic coefficient approach, we forecast vehicle ownership and GHG emissions, focusing on Shenzhen City as case study. We also factor in the learning curve associated with EV battery costs into our dynamic cost-benefit model. Scenario analysis reveals that Shenzhen’s incremental car restriction policy decreased the number of cars by 18.7% in 2017 alone. By actively promoting EVs in a net zero carbon scenario, it’s feasible that CO2 emissions might reach their peak as soon as 2020. Our cost-benefit analysis indicates that improving fuel economy policies for vehicles yields higher marginal abatement benefits. Although the initial push for EVs may result in elevated marginal abatement costs due to infrastructure investments, anticipated long-term reductions in battery costs, driven by economies of scale, could offset these costs, potentially even leading to net benefits.

Abstract

Rooftop photovoltaics (RPVs) play a crucial role in reducing urban carbon emissions and aiding the shift toward net-zero energy systems. However, the complexities of urban settings introduce significant variability in RPV costs across different locations and times. This study focuses on the Pingshan District in Shenzhen, a representative example of cities in southern China. The study analyzes geometric characteristics and community types from various urban areas to perform K-means++ clustering. These typical community types are then used to comprehensively assess RPV deployment in terms of energy, environment, and economics. The study provides practical strategies for integrating RPVs, offering insights that contribute to sustainable urban energy transitions.

Abstract

The rapid adoption of shared electric micro-mobility solutions, such as e-scooters and e-mopeds, has addressed the need for low-carbon transportation and efficient last-mile travel. However, challenges persist due to insufficient parking and charging infrastructure. This study introduces an innovative shared electric micro-mobility hub prototype, incorporating PV panels to provide energy and shared power bank stations for battery storage. Through a comprehensive case study, the economic and environmental benefits of different micro-mobility configurations and energy management strategies are evaluated. The results demonstrate that the micro-mobility with appropriately configured PV and shared power bank station can reduce carbon emissions by 99% and achieve a net income within one year. This research not only advances sustainable urban transportation but also provides a model for integrating various shared services, contributing to a more environmentally friendly and versatile urban lifestyle.

Abstract

The booming electric vehicle (EV) charging facilities play a vital role in connecting road transport networks to the urban power grid, as they have internal smart converters with four-quadrant power regulation capability. These converters can provide reactive power to regulate the voltages of urban distribution power grids. Considering the high scarcity of urban spatial resources, there are many restrictions on configuring additional capacitors or other voltage regulating devices. It is of significance to accurately assess the volt/var support capability from the charging facilities on urban grid voltage regulation. This paper constructs a road traffic network model and EV behavior characteristic models for private cars, cabs, and urban service vehicles, respectively. Then, a method for spatial and temporal charging load prediction as well as reactive power flexibility assessment is proposed considering dynamic traffic flow. The assessment results are adopted as boundaries for chargers participating the volt/var regulation of urban power distribution system. The voltage qualification rate indicators are investigated to verify the effectiveness of the proposed regulation method. The results of this paper are helpful for understanding the coupled urban electrified road transportation and power system facilities from a new perspective of volt/var regulation.

Abstract

Due to their environmentally friendly and energy-saving characteristics, regional distributed energy systems (RDES) have become one of the important ways to enhance renewable energy consumption and promote low-carbon society in recent years. The bottleneck of using peak load of user nodes in the division of energy supply scope at energy stations without full considering the load timing characteristics is addressed in this paper. Furthermore, this paper proposes a collaborative optimization method that considers load timing characteristics. Firstly. the coupling characteristics between energy stations and pipeline network are analyzed. Then a collaborative optimization design model for energy stations and pipeline networks is constructed based on K-means and graph theory algorithms. Subsequently, considering the load timing characteristics to analyze their impact on REDS. The research results indicate that considering the load timing of user nodes can reduce the cooling load demand of energy stations by 19.05% and the total pipeline cost by 8% compared to using peak loads. This paper provides theoretical and technical guidance significance for decision-makers of regional distributed energy systems.

Abstract

The CO2 methanation (that is, Sabatier reaction), has been considered as a promising way to recycle and utilize CO2. However, the industrial Sabatier process is energy intensive and traditionally powered by fossil fuels. Harvesting solar energy for the conversion of CO2 into solar fuels offers a sustainable and green solution to alleviating energy and environmental issues. In this work, solar-driven CO2 methanation over nickel-based catalysts was investigated under concentrated solar irradiation. A CO2 conversion rate of approximately 87%, with 100% selectivity towards CH4 and a reaction rate of 380 mmol/gNi/h were achieved under concentrated UV-visible-IR irradiation at 350 °C on 15 wt% Ni/Al2O3. The temperature required to achieve maximum CO2 conversion for the nickel-based catalysts were 25 °C lower in the solar-driven process compared to conventional thermocatalytic process. Meanwhile, the apparent activation energy of the solar-driven reaction is 25% lower than that of the thermocatalytic reaction. Moreover, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments were performed to gain an in-depth insight into the enhancement mechanisms of light in the solar-driven process. This study emphasizes the merits of utilizing concentrated solar energy for driving chemical reactions, revealing the promotion of the reaction by light and offering new insights into the reaction mechanism of solar-driven CO2 methanation over Ni-based catalysts.

Abstract

The smart PV window, integrated of solar cells and electrochromic coating, is of great significance in the pursuit of building decarbonization, as it combines power generation and radiation modulation capabilities. This study aims to unraveling the untapped potential of smart PV windows in the realm of enhancing building energy conservation and flexibility in hot climates. To achieve this objective, a co-simulation approach utilizing EnergyPlus and Radiance software is employed, along with the implementation of the EMS module to control the coloring states of the smart PV window. The findings reveal that, compared to the Low-E window, the smart PV window with solar radiation control improves the proportion of the useful daylight illuminance by 61.8%, yields a significant reduction in peak load by 72.3%, a decrease in monthly net energy consumption by 53.9%, and an enhancement in energy flexibility by 51.8% in Hong Kong (22.32°N, 114.17°E).