Abstract

The high cost of commercial catalysts has hampered the commercialization and cost-effective production of renewable diesel in recent times. This research investigates the effect of silica (SiO2) reinforcement on bio-based thermal power plant fly ash (BBTPPFS) for hydrogenation. The BBTPPFS and the SIO2 were pulverized, calcinated, and subjected to various characterization processes. The value of micropore volume, surface area, and external surface area of sample due to the reinforcement by SiO2. These results show that the addition of SiO2 to BBTPPFS improved the potential of the BBTPPFS as a heterogeneous catalyst for hydrogenation.

Abstract

Internal heat exchangers (IHX) are commonly used to improve the energy performance of vapour compression refrigeration cycles. However, the magnitude of the improvement depends on the refrigerant and operational conditions. This paper experimentally investigates the influence of a high IHX on vapour compression systems. The new low global warming potential refrigerant R516A is assessed as a drop-in replacement to R134a at different medium temperature refrigeration conditions. In the case of a 40% effectiveness IHX, R516A shows the highest cooling capacity (4.8% to 9.1%), and COP (4.9% to 11.6%) increases compared to the situation without this element. It can be concluded that the IHX always benefits the energy performance of the refrigeration system at acceptable compressor discharge temperatures.

Abstract

Energy communities (ECs) are one of the key strategies of the European Union’s plan to increase adoption of renewable energy sources (RES). A better understanding of factors that facilitate the existence of energy cooperatives (ECoops), the most common organizational form of ECs, might contribute improving strategies to foster larger adoption of ECs. We perform an exploratory spatial data analysis to assess if RES availability and quality, quantified using four decades of ERA5 data, co-occur with the presence of ECoops across Europe. Results show a slight predominance of ECoops where wind resources are high and opposite results for solar resources. At the continental level, the spatial relation between ECoops and the proposed indicators is rather random but local clusters develop where RES’ availability is high.

Abstract

Emission-free hydrogen is a crucial contributor to the decarbonization of the energy supply. To establish a H2 economy, a H2 infrastructure is needed and requires investment and energy policy decisions today. The aim of the paper is to inform these decisions by comparing and contrasting the construction of new H2 pipelines with the repurposing of natural gas pipelines for future H2 ad-mixture.1) feasibility and (2) 1.5°C alignment are proposed as evaluation criteria for effective climate mitigation. The results show that building new H2 pipelines for renewable H2 is feasible and 1.5°C-aligned. Gas pipeline investments for future retrofitting are not recommended due to energy transition risks such as fossil-lock in and asset stranding.

Abstract

We propose a framework to unravel the hurdles and opportunities for the renewable energy transition in con-temporary crises to examine the interconnections be-tween energy transition, climate risks, and geopolitical issues. The study focuses on Germany and emphasizes that neglecting climate-related risks leads to financial in-stability and hampers the energy transition. If Paris-aligned energy and financial policies are not in place, fur-ther cascade (negative) effects on energy transitions may occur. Uncertainty and instability caused by geopolitical crises intensify negative feedback loops. Climate mitiga-tion is thus critical because climate concerns affect finan-cial stability and the orderly path of energy transitions.

Abstract

Building electrification and decarbonization are a focus of municipalities around the world as part of their long-term sustainability initiatives. In order to meet ambitious climate goals, buildings will need to minimize energy use through energy efficiency and be grid-interactive through demand flexibility (DF). While mechanisms to understand the relative energy efficiency of buildings are well established, the literature currently lacks mechanisms to score the performance of grid-interactivity and demand flexibility in urban buildings. This is substantial as the carbon intensity of electricity can vary substantially for different parts of the day as renewable energy penetration rises. In response to this, we conduct policy landscape analysis for integrating DF disclosure in energy performance standards and develop a roadmap for enabling DF driven building decarbonization. We focus on New York City as a case study given its current policy push for rapid building decarbonization and conduct an extensive literature review on measuring DF of buildings. Specifically, we aim to: (1) identify the limitations of current policy, (2) determine barriers to adopting DF disclosure, (3) ascertain potential policy recommendations and the potential impact such policies could have on New York City’s building decarbonization goals. Overall, this work aims to demonstrate the decarbonization potential of DF disclosure and in turn catalyze the adoption of similar policy roadmaps for cities around the world.

Abstract

In this paper, a simulation is carried out on a precooled liquid desiccant system working with aqueous Lithium Chloride (LiCl). The effects of different ambient air humidity on the outlet air humidities of absorber and desorber, crystallization of LiCl, cooling capacity, and COP of the system are analyzed. Besides, the system is compared to experimental results of an internally cooled liquid desiccant system using a new ionic liquid which is referred to as IL9. The conditions for both, the experiment as well as for the simulation are the same in terms of heat and mass transfer area, air inlet parameters, heat exchanger effectiveness, and hot and cooling water temperature. Some conclusions are summarized, for instance, the system using LiCl should be driven by the hot water of no more than 80℃ to avoid the crystallization risk, and the internally cooled system using IL9 shows a higher dehumidification performance than the pre-cooled system using LiCl especially at increased inlet air humidities.

Abstract

In order to improve the temperature uniformity and reduce the maximum temperature of the surface with Gaussian heat flux, a radiator with jet impinging on the structured surface was proposed in this paper. The effects of Reynolds number and structured surface geometry were observed. The heat transfer performance for three structured surfaces were compared with smooth wall configuration under the same conditions. As the Reynolds number increases, Nu appears with multiple local peaks in the radial direction, which is attributed to the increase of turbulent kinetic energy and the change of flow field. Among three structured surfaces, the rectangular rib has the best performance both in heat transfer and temperature uniformity, followed by the cubic rib, both of which have strong disturbance to the flow field. Due to larger thermal resistance of heat conduction, the convex structure exhibits worst heat transfer performance.

Abstract

This paper conducts a numerical study on the characteristics of mean flow field of a combustor with triple swirlers with focus on the effect of turbulence models on the central recirculation zone (CRZ). By comparing numerical results with high-speed photography experiment, it is found that k-ε RNG model can better predict the flow field characteristics than k-ε realizable and k- ω SST model. the CRZ length and expansion angle obtained by k-ε RNG model are consistent with experiments, and k-ε Realizable model are relatively close to it, while k-ω SST model is quite different from the two others. The results predicted by k-ω SST have much higher backflow strength and pressure gradient. The study is of great significance to reasonably choice turbulent mode to predict swirling flow in a combustor.

Abstract

In this paper, the temperature mathematical model and compressor model are established to study the effect of different charge/discharge rates on air conditioning energy consumption. The results show that as the charge/discharge multiplier increases, the air conditioning starts earlier and runs longer, and the energy consumption of the air conditioning system also increases. This method considers different charge/discharge rates of batteries and combines with the energy consumption analysis of air conditioning systems, which is of great value for improving the safety and efficient utilization of energy storage systems.