Abstract

Coal-fired power plants integrated with post-combustion carbon capture technology are selected as an effective way to meet the demand for electricity, and to ameliorate the environmental pollution caused by the burning of fossil fuels. However, there is energy loss in the coal-fired power plants integrated with large-scale carbon capture systems. To obtain the optimal system parameter of coal- fired power plants integrated with large-scale carbon capture systems, the inlet temperature of the stripper and the irreversibility of the system is first analyzed, followed by waste heat utilization. As renewable power generation deployment grows, fossil fuel plants, including coal-fired units with coupled carbon capture systems, are being forced to operate more flexibly. The performance of coal-fired power plants integrated with large-scale carbon capture systems under load-cycling operation conditions is analyzed. It turns out that the exergy efficiency of CPCC under 30%THA is the lowest, only 2.9%. The structures should be restructured under low load ratio.

Abstract

To obtain a better understanding of the characteristics of large-scale seasonal borehole thermal energy storage (BTES), a demonstration project was developed in Chifeng, China. In the project, combined heat sources of industrial waste heat and solar energy were adopted for 500000 m3 borehole thermal energy storage. In this study, the long-term thermal and economic performance of the demonstration project was analyzed based on the operation data of the demonstration project. First, actual system energy and economic performance of the demonstration project were analyzed. After that, a system simulation model was established and calibrated with the long-term system measured data from the demonstration project. The system simulation model was integrated into the LCCA model for assessing system long-term economic performance with different system design parameters and operation strategies. Then a multi-object optimization based on Non-dominated Sorting Genetic Algorithm II (NSGA-II) was conducted for finding the optimal design configuration and system performance.
The results of this study showed that, the annualized cost of borehole thermal energy storage of the studied system around 4-6 US$/GJ, and it could be further reduced to 2.7 $/GJ in China by reducing the borehole drilling cost and returning water temperature of the district heating network. Which emphasized that borehole thermal energy storage has a good application prospect in future urban distributed energy systems.

Abstract

Conventional ice-skating rinks require an intensive refrigeration load and continuous use of chiller which results in a substantial energy consumption. Therefore, novel, and sustainable alternatives are required to make more energy efficient ice-skating rinks. In this study, we propose a novel first-of-a-kind PCM (Phase Change Material) based ice skating rink and report the development of computational tool based on CFD (Computational Fluid Dynamics) to study various design aspects of such innovative system. The overall results show the significance of this model in providing a powerful tool to select suitable PCM, test operating parameters such as inlet temperature and flow rate, as well as predict the ice rink performance under different scenarios.

Abstract

The wastewater sector represents a significant contributor to greenhouse gas (GHG) emissions, and the issue of GHG emissions from wastewater infrastructures in the Qinghai-Tibet Plateau (QTP) has been overlooked. This study constructed a unified accounting framework based on the emission factors approach to quantify GHG emissions from wastewater infrastructures on the QTP, and identified the influencing factors of GHG emissions changes through Logarithmic Mean Divisia Index (LMDI). Within our accounting framework, we took into account the temperature coefficient to accurately represent the low water temperatures prevalent on the QTP. Furthermore, we revised the emission factor for electricity consumption by considering the local energy structure based on the development of clean energy. Spatial and temporal differences were analyzed using the GHG emissions accounting results spanning from 2014 to 2018. The results show that total GHG emissions from QTP’s wastewater infrastructures increased from 0.25 Mt CO2e to 0.43 Mt CO2e between 2014 and 2018, with the cities along the edge in the east exhibiting noticeably higher GHG emissions. The development of clean energy on the QTP has led to a reduction in the electricity emission factor, thereby slowing down the growth of GHG emissions by 18.7%. The increase in sludge yield and electricity intensity of WWTPs contributed 10.3% and 9.6% to the overall growth of GHG emissions, and reducing these two influencing factors can effectively decelerate the upward trajectory of GHG emissions in the wastewater sector.

Abstract

Liquid air energy storage is a promising large-scale energy storage technology with high energy density for increasingly weather-dependent power grids, with no geographical constraints. The round-trip efficiency of a standalone liquid air energy storage system is predicted to be between 40 % and 67 %. An attractive way to increase the economic viability of the liquid air energy storage system is to couple the system with additional heat sources. Incorporating concentrated solar power has recently been proposed to increase the temperature at the inlet of the air turbines, and thus boosting the discharging power output and round-trip efficiency. This paper aims to find the optimal system design based on concentrated solar power temperature, considering both energy storage and power production metrics. The analyzed liquid air energy storage system is based on the Linde cycle, two tank thermal oil system for compression heat storage, and a two tank, two stage cold recovery system using methanol and liquid propane. A heliostat system with two-tank direct molten salt thermal energy storage is used as an additional heat source. A supercritical organic Rankine cycle system is used for excess heat recovery with R32 as working fluid. Novel ways of integrating the organic Rankine cycle system for multiple-source excess heat utilization were analyzed. Effects of charging and discharging pressures, number of air compressors and turbines and solar heat transfer fluid temperatures on the optimal organic Rankine cycle design and round-trip exergy ratio were studied. The results suggest that a maximum round-trip exergy ratio of 62.2 % can be achieved. The paper provides a basis for further optimization of design and operation of the solar aided liquid air energy storage systems, especially in off-design conditions for low sun availability.

Abstract

This article presents a two-dimensional axis-symmetric computational fluid dynamics (CFD) simulation of a three-stage travelling wave thermoacoustic engine using Ansys Fluent. The model incorporates porous media submodels to represent heat exchangers and regenerators, operating at a heating temperature of 600 K and an ambient temperature of 293 K, with helium as the working fluid stabilised around 3 MPa mean pressure. In comparison to traditional network models, CFD yields accurate results in solving the flow field and captures higher-order details in the fluid domain.

Abstract

The orientation of solar collector arrays significantly influences the efficiency and performance of solar thermal systems. However, in some instances, practical limitations may prevent the optimal orientation of these collector arrays. This research investigates the performance of a field of High Vacuum Flat Collectors (HVFPCs) under suboptimal conditions. Our test facility features 25 arrays located on both sides of a building’s roof. Each array forms a 6° angle with the horizontal plane. Of these, four panels are on the east-facing surface, and three are on the west-facing surface. All collectors within the arrays have a tilt angle of 15° and an azimuth angle of 0°. We began performance assessments using a single pyranometer placed between the two roof sides to gauge solar irradiation. Later, we used two pyranometers one on each roof side. Both had identical tilt and azimuth as the collectors, ensuring independent irradiation measurements. When comparing these measurements to numerical results from a dynamic simulation, we discovered that a comprehensive plant performance evaluation must account for the varied orientations of collectors in the arrays. These results underscore the need to consider collector orientation’s impact on performance, even if ideal orientations are unattainable due to installation challenges. Understanding how non ideal collector array orientation affects system efficiency leads to improved flow rate regulation techniques, optimizing performance and energy use.

Abstract

Hydrogen has gained significant attention as a possibly important energy vector in the pursuit of climate change mitigation objectives. Global demand for renewable hydrogen is anticipated to increase across many decarbonization scenarios. To meet this demand, many countries have unveiled strategies aimed at bolstering domestic low-carbon hydrogen production or facilitating imports. Within this context, international trade has emerged as a means of importing hydrogen from regions with low-cost production capabilities. However, investment decisions in the development of international hydrogen markets are moving slowly due to large uncertainties regarding the magnitude of future demand and willingness to pay for hydrogen in key end- use applications.
In this study, we develop a novel modelling framework capable of simulating global hydrogen market equilibrium and international trade scenarios in the long-term future. Our methodology includes the development of supply and demand curves, as well as a global hydrogen trade model that takes into account various supply chain options. Using this framework, we are able to derive quantitative insights into equilibrium supply and demand, pricing dynamics, trade flows, costs, and many more. We apply this framework to investigate the optimal development of hydrogen markets in 2050 under a 1.5°C climate change mitigations scenario. Our findings indicate that new hydrogen sectors could see a global demand surge to 195.2 Mt, with international trade constituting a quarter of this demand.