Renewable Energy最新文献

Power scheduling is an NP-hard optimization problem that demands a delicate equilibrium between economic costs and environmental emissions. In response to the growing concern for climate change, global environmental policies prioritize decarbonizing the electricity sector by integrating renewable energies (REs) into power grids. While this integration brings economic and environmental benefits, the intermittency of REs amplifies the uncertainty and complexity of power scheduling. Existing optimization approaches often grapple with a limited number of units, overlook critical parameters, and disregard the intermittency of REs. To address these limitations, this article introduces a robust and scalable optimization algorithm for renewable integrated power scheduling based on reinforcement learning (RL). In this proposed methodology, the power scheduling problem is decomposed into Markov decision processes (MDPs) within a multi-agent simulation environment. The simulated MDPs are used to train a deep reinforcement learning (DRL) model for solving the optimization. The validity and effectiveness of the proposed method are validated across various test systems, encompassing single-to tri-objective problems with 10–100 generating units. The findings consistently demonstrate the superior performance of the proposed DRL algorithm compared to existing methods, such as multi-agent immune system-based evolutionary priority list (MAI-EPL), binary real-coded genetic algorithm (BRCGA), teaching learning-based optimization (TLBO), quasi-oppositional teaching learning-based algorithm (QOTLBO), hybrid genetic-imperialist competitive algorithm (HGICA), three-stage priority list (TSPL), real-coded grey wolf optimization (RCGWO), multi-objective evolutionary algorithm based on decomposition (MOEAD), and non-dominated sorting algorithms (NSGA-II and NSGA-III). Regarding the experimental results, it is important to highlight the importance of integrating RESs into larger power systems. In a 10-unit system with 2.81 % RE penetration, reductions of 3.42 %, 4.03 %, and 3.10 % were observed in costs, CO₂ emissions, and SO₂ emissions, respectively. Similarly, in a 100-unit system with a RE penetration rate of only 0.28 %, reductions of 3.75 % in cost, 4.42 % in CO₂, and 3.34 % in SO₂ were observed. These findings emphasize the effectiveness of RES integration, even at lower penetration rates, in larger-scale power systems.

This study provides an in-depth economic analysis to aid decision-making in the adoption of small-scale biogas technology in rural areas of Cameroon. It also provides evidence of the field investment characteristics of the biogas energy supply in rural areas of Cameroon. The methodology focused on assessing the economic viability of different sizes of biogas plants and the willingness of farmers to pay for the same. A sample of 180 farmers was selected for the study. Data collection was carried out from December 2020 to May 2021 using a questionnaire survey and participant observation. The results show that all small-scale biogas plants are economically viable. Benefit-cost ratios were 1.01, 1.19, 1.50, 1.02, 1.21 and 2.04 for the 4 m³, 6 m³, 8 m³, 10 m³, 20 m³, and 25 m³ biogas plants. The net present values in US dollars (USD) were 959, 1790, 2695, 2658, 6047, and 12267 for the 4 m³, 6 m³, 8 m³, 10 m³, 20 m³, and 25 m³ biogas plants, respectively. The internal rate of return was higher than the applied discount rate of 12 %. The minimum payback period of 2.24 years was recorded for the 25 m³ while the maximum of 3.37 years was recorded for the 10 m³ biogas plants, respectively. With a disproportionate increase in the cost of biogas plants by 20 % and a 20 % decrease in benefits with a discount factor, the net returns are positive, indicating that all biogas plants are economically viable. The mean willingness to pay is estimated at 13 USD or 8000 FCFA. This resulted in an average repayment period of 11.5 years. The provision of extension services, financial incentives, and regulation of the small-scale biogas market will motivate farmers to adopt the technology.

Shallow geothermal offers great potential to supply emission-free heating and cooling and has therefore a pivotal role in the transition of heating and cooling networks. This paper presents a novel heating and cooling network with possible geothermal energy sharing between decentralized borefields located at each building level. The system consolidates the benefits of both standalone and centralized energy systems to attain high-efficiency gains and ensure a secure heating and cooling supply. To study the expected system performance, a simulation model is demonstrated and applied to a real-world case study consisting of three new buildings located in Malmö, Sweden. Simulation results revealed that the established synergy through geothermal energy sharing can reduce the purchased electric energy by 23 % and increase the annual performance factors for heating and cooling by 31 and 35 %, respectively compared to the standalone system.

When powered by electricity, Connected and Autonomous Vehicles (CAVs), an emerging mode of transportation, possess the capacity to reduce exhaust emissions greatly. However, accurately measuring carbon emissions in urban transportation remains a challenge, especially considering emissions from electricity generation and gasoline consumption. This paper proposes an innovative method for calculating CAVs' carbon emissions distribution, utilizing both renewable and non-renewable energy. The study employs SUMO, an agent-based simulation platform, to develop an intelligent driver model and cooperative adaptive cruise control modules, tracking vehicle movement behavior across various vehicle types, including Gasoline Vehicles (GVs), Electric Vehicles (EVs), Human-Driven Vehicles (HDVs), and CAVs. Subsequently, a lifecycle electric carbon emission model is constructed, integrating the energy consumption model of EVs with carbon emission factors of renewable and non-renewable energy. Visualization models are then developed to clarify the carbon emission distribution within the traffic network. A case study conducted in Suzhou, China validates the model, analyzing the spatiotemporal distribution of carbon emissions. Results show EVs can reduce carbon emissions by 70%–90 % compared to GVs on urban roads during rush hour, while CAVs can further reduce emissions by 35%–50 % compared to HDVs. Additionally, carbon emissions from non-renewable energy sources were found to exceed those from renewable sources.

The efficiency of air-type solar towers influences the minimal cost of electricity/heat produced by them, which limits their use despite the widespread use of many forms of concentrated sun power plants. Nonetheless, the temperature potential of this kind of concentrated plant is the highest. To improve the efficiency of an air-type solar tower, a technique for reducing convective energy losses with return air is therefore suggested. In order to increase a cavity receiver's thermal efficiency, a little-known concept called vortex creation will be discussed in this work. The article models different ways of creating an air vortex inside the cavity receiver. Using the VoCoRec design as an example, cases are shown where the vortex increases and decreases the thermal efficiency of the receiver. The concept of Air Return Ratio (ARR) is used to determine the convective losses in a solar collector. This coefficient indicates the convective losses of the receiver due to buoyancy forces and has a direct proportional dependence on the convective efficiency coefficients of the receiver. The VoCoRec receiver, which incorporates the directional vortex inside the receiver, increased the air return coefficient by 4 % (at the same air mass flow rate). The dependence of the air return coefficient on different angles of the air outlet to the absorber plane, including in the radial direction, was also investigated. Increasing the angle of inclination of the air outlet to the main absorber increases the air return coefficient in all cases, but also increases the aerodynamic drag of the receiver (pressure drop).

Converting lignocellulosic materials into renewable energy through anaerobic digestion (AD) often has low degradation efficiency and thus needs improvement. Inoculum seeds from biogas plants fed with cow manure (CM), pig manure (PM), Napier grass (NG), and goat manure (GM) were explored for high-potential lignocellulose-degrading inocula based on the biochemical methane potential. Overall, CM, PM, and GM seeds could degrade lignocellulose. However, PM inoculum exhibited the highest CH₄ production rate from cellulose powder, xylan, and Napier grass degradation by 46.32, 49.61, and 18.56 NmL/gVS_added·d, indicating the shortest lag phase but lagged behind GM and CM for alkali lignin. Microbial community analysis revealed lignocellulose-degrading microorganisms in the inocula. A high relative abundance of cellulose-degrading bacteria, such as Anaerolineaceae, Romboutsia, Bacteroidetes vadinHA17, and Clostridium sensu stricto 1, was detected. Anaerobic lignin-degrading bacteria were found in CM, PM, and GM inocula. Moreover, Bathyarchaeia from the archaeal group involved in lignocellulose degradation was found in CM and GM inocula. Keystone methanogens for methanogenesis were also detected in all inocula. PM inoculum possesses a promising inoculum seed for shortening the start-up period of the lignocellulose-degrading reactor with high AD performance and stability as it provides a short lag time and a high rate of methanogenesis.

This study addresses the intermittent renewable energy supply and the large footprint of battery storage on an island reef in China by proposing an integrated energy system that incorporates hydrogen production, storage, and utilisation. Mathematical models for wind and photovoltaic power generation, energy storage, hydrogen production and utilisation, diesel generators, and energy management systems are established. Additionally, an integrated energy system is constructed using Simulink software to simulate and analyse its operational characteristics in various seasonal scenarios. The simulation results indicate that the surplus from wind power and photovoltaic systems, after supplying the load for over 70 % of the day, constitutes more than 40 % of the load demand. The energy storage system can maintain a maximum charging rate for more than 50 % of the day and a maximum discharge rate for less than 16.7 % of the day. The electrolysis tank produces hydrogen for more than 71 % of the day and simultaneously consumes up to 750 % of the load. The fuel cell consumes hydrogen for less than 12.5 % of the day and simultaneously provides up to 27 % of the load. Analysis revealed that the hydrogen system improves the energy utilisation, the control strategy realises stable supply and demand within the system.

Exergy transmission characteristic of the compressed CO₂ energy storage system is significant to evaluate the system performance while little attention has been paid to this analytical method in the literature. A CO₂ energy storage cycle configured with a gas holder as a low-pressure gas reservoir and a liquid tank as a high-pressure gas reservoir is studied comprehensively. The exergy transmission characteristics and the cost uncertain analysis are considered. Results demonstrated that the round trip efficiency and levelized cost of storage are 71.2 % and 0.1286 $/kWh under optimal design parameters, respectively. Keeping the charge/discharge duration ratio close to 1 has a positive effect on optimizing the economic performance of the system. With the general exergy model of the whole system configured for the charge and discharge process, the study uncovers the fluctuations in the pertinent proportional ratios and exergy transfer efficiency in relation to important parameters. Except for the turbomachinery isentropic efficiency, which impacts nearly all efficiencies, the variation of each parameter only governs the modification of the exergy transfer efficiency for a specific term or a pair of terms. Furthermore, the thermal exergy efficiency of the discharge process and intercooler has a maximum value as the cold-side temperature difference of the high-temperature cooler changes to 27 °C.

The design of thermal energy storage (TES) tank is the key part that can limit charging and discharging process. Most research findings highlight that the use of fins augments the heat transfer rate. This work experimentally investigates the use of aligned copper wools as fillers to enhance the thermal performance of a lab-scale shell-and-tube TES tank filled with phase change material (PCM). Two copper wools with different fibre thicknesses were chosen and discretely laid around the TES tank tubes in two design patterns. Accordingly, five shell-and-tube TES tank configurations were obtained, including the reference, for performance evaluation. The TES tank was loaded with n-octadecane as PCM for all the cases studied. The results showed up to a 16 % reduction in melting time with the inclusion of copper wool. The TES tank significantly increased the mean power during charging (53 %) and discharging (205 %). The addition of metal wool into the TES tank enables the PCM to release the heat at a constant temperature during the entire phase transition process. And the overall efficiency of the TES tank was found to get improved. Therefore, a copper wool integrated TES tank would be a beneficial addition to thermal energy storage systems.

Aerobic deterioration of silage material is unavoidable during the feed-out stage; therefore, in this study, the influence of the feed-out stage on the methanogenic potential of different silage fermentation types was evaluated. Lactic acid in corn straw silage was the first substance to be completely consumed by 3 days after opening and the pH increased substantially. In homolactic fermentation, yeast and mold proliferated in an aerobic environment; the organic dry matter loss rate was less than 2.0% and cumulative methane yield_orig reduction rate was only 3.9% at 1 day after opening than silage storage. However, these values increased to 18.9% and 34.9%, respectively, 3 days after opening, which were much higher than those obtained under non-homolactic fermentation. Therefore, a feed-out frequency of no more than one day is recommended in practical engineering applications. Meanwhile, promoting non-homolactic fermentation can improve the aerobic stability of raw materials and reduce energy loss.