Navigating the complex transformation process towards a sustainable energy system requires considering multiple stakeholders and various criteria within a multifaceted decision-making process. This work lays out a conceptual framework to identify holistic transformation trajectories for the implementation of a sustainable bioeconomy in Germany under consideration of stakeholder-specific perspectives and weighted decision criteria in the context of energy planning towards a low carbon economy.
In the light of the ambitious climate goals, the energy efficiency scope is gradually shifting from an individual building to a broader range – urban block, neighborhood, district, and city. Smart cities and communities show a significant potential of reaching energy efficiency goals. This study presents the results of a newly developed demand‐supply energy flow model. The model simulates the energy demand and supply dynamics of a traditional building block in the historical center of Riga, the capital of Latvia. The authors analyzed 12 different scenarios applying four factors – energy efficiency, renewable energy technologies, waste heat recovery, and electricity storage in electric vehicles.
With the increasing availability of urban factors and building energy datasets, more studies have emerged in the urban building energy field examining the urban form–energy relationship to support energy-oriented urban planning and urban energy system management. However, two limitations exist in current studies: the oversimplified quantification of urban form and the lack of consideration of temporal energy use pattern. Recent studies focused more on urban and building factors that are theoretically relevant to building energy, but how these factors are related to energy use patterns is still far from clear. This study aims to fill this research gap by examining the relationship between urban form typology and residential building energy patterns in Seoul using clustering and the Sankey diagram. The study used the Gaussian mixture model to identify four typical urban form typologies based on energy-relevant urban factors and k-shape clustering to detect three distinct monthly primary energy use patterns of residential buildings. The urban form typologies and energy use patterns are then compared through the Sankey diagram. The comparison shows a complex correspondence. The Mid-rise Open typology achieves a general balance among the three patterns, while the Mid-rise High-density typology, Low-rise Compact typology, and High-rise Low-density typology are all dominated by a U-shaped pattern with a varying balance between the Flat pattern and W-shaped pattern. The findings of this study depict the correspondence between urban form typologies and building energy use patterns, which are highly interpretable and thus informative for energy-oriented urban planning and energy system management toward sustainable urban development.
Along with the increasing popularity of Electric Vehicles (EV) and the expansion of the charging infrastructure, energy demand from EVs is expected to grow substantially in cities. The aging population, as one of the main concerns in South Korea, should also be taken into consideration in future EV energy demand prediction, because the elderly population, defined as those over the age of 65, are found to travel less in general but are more likely to rely on private vehicles in their trips. How will energy demand and charging loads as the driver population continues to age, the number of EVs, and charging infrastructure continue to grow? The study aims to answer this question by simulating future energy demand and charging loads in Seoul under future scenarios with different population estimation, EV penetration percentages, and charging infrastructure development schemes. The study utilizes an agent-based modeling software called BEAM (Behavior, Energy, Autonomy, and Mobility) which is an extension of MATSim, an open-source transportation simulation tool, to simulate within-day travel behavior in Seoul on a typical weekday in Spring. The two main datasets used are the 2016 national household travel survey data and road network data of Seoul from the open street map. The energy demand results from scenario-based simulation for Seoul in 2030 and 2047 concludes that total energy demand will increase with charger availability and decrease in overall charging demand as population ages.
Recently, solar steam generation as an efficient way of solar harvesting shows great potential in solving the fresh-water shortage issue, due to it is zero carbon emission and high photothermal utilization. However, the drawbacks caused by salt accumulation on the evaporator surface would severely lower the efficiency and lifetime of the whole evaporation system. This research attempted to fabricate a facile and reliable evaporator by firstly introducing a plasmonic enhanced porous solar evaporator membrane via a one-step laser scribing method. The Cu nanoparticles scaled in multiple sizes would be cladded with the graphene and deposited onto the membrane surface. This novel evaporator obtains a high solar spectrum absorption of more than 98 %, which results in a high surface temperature of more than 80 ℃ under 1 sun irradiation. Meanwhile, the fabricated solar-driven membrane can achieve a high evaporation rate of 2.29 kg/m2.h, besides it exhibits a high efficiency of 1.82 kg/m2.h and long-term stability in a highly concentrated brine of 20 wt% NaCl.
The formation of gas hydrates in porous sediments composed of fine-grained media with a larger specific surface should be imaginatively faster, while why do hydrates in natural conditions tend to accumulate in coarse particles? In view of the controversy over the influence of sediment conditions on hydrate formation kinetics, in this work, a high pressure micro-differential scanning calorimeter (HP μ-DSC) with small reactor volume and high precision was specially used to systematically investigate the effects of quartz sand particle size, initial water content, and sediment medium type on the formation kinetics of CH4 hydrate in porous sediments. The results show that the CH4 hydrate formation rate, on a whole, increases with the decreased quartz sand particle size and initial water content. However, it is not completely monotonous, and the difference and degree of the influence for one factor on the hydrate formation depends on the choice of another factor. Moreover, the addition of kaolin or bentonite even with smaller particle size and larger specific surface, however, relatively hinders the formation of CH4 hydrate. By directly observing the formation process of CH4 hydrate in different porous sediments, it was found that the rapid hydrate growth in porous sediments relies greatly on the continuous diffusion and growing of hydrates towards adjacent media. In addition, some interesting phenomena for bentonite wetting and cracking have also been observed. The discoveries in this work provide a systematic and unique insight into the natural gas hydrates formation in porous sediments.
It is well known that H2 molecule can more easily migrate between hydrate cages and realize multiple molecule occupation due to its small molecular diameter. In this work, several splitting DSC endothermic peaks for CO2/H2 hydrate decomposition in constant pressure and 29.5% CO2 + 70.5% H2 gas composition were unexpectedly found through a high pressure micro-differential scanning calorimeter (HP μ-DSC). These DSC decomposition peaks have the typical characteristics with several different hydrates coexisting. The dissociation temperatures corresponding to these peaks showed obvious regularity that the temperatures for those first peaks and last peaks are almost close to the equilibrium decomposition temperature of the CO2/H2 hydrate with the similar gas phase component and pure CO2 hydrate respectively. We speculate that the occurrence of this peculiar phenomenon may be mainly due to the different occupation of H2 molecules in CO2/H2 hydrate cages. This led to the metastable change of hydrate equilibrium conditions, and therefore resulted into the delayed decomposition. Raman spectra confirmed the various occupation of H2 molecules in CO2/H2 hydrate cages under this experimental conditions. The finding in this study may provide some new insights into the deeper understanding of the physical/chemical properties behind clathrate hydrates in the future.
Clean and efficient biofuels sourced from lignocellulosic biomass can play a significant role in achieving carbon neutrality. Enzymatic hydrolysis is regarded as the key step in this process. In this study, inspired by the termite gut, a two-stage microreactor loaded with enzymes was proposed for the efficient conversion of wheat straw to produce sugar. The two-stage microreactor is composed of the sections loaded with xylanase and cellulase mixture orderly. After being reacted in the microreactor loaded with xylanase for 24 h, 17.1% of xylan was removed, thus producing xylose while increasing the accessibility of cellulose. Compared with wheat straw without catalysis by xylanase, the initial adsorption rate of methylene blue on wheat straw pretreated by xylanase for 24 h was increased by 13.7%, and the maximum adsorption capacity was increased by 8.1%. Furthermore, after being catalyzed in the first stage by xylanase for 6-24 h, the glucose production in the second stage within 6 h was increased by 23.9-89.7%. In the two-stage microreactor, the conversion of cellulose reached 13.7% in 24 h at a low enzyme input of 7 FPU g-1 biomass. The xylan conversion reached 47.1% in 36 h. Considering enzyme reusability and enhancement of cellulose conversion, the two-stage microreactor can be used for the hydrolysis of lignocellulosic biomass.
Mass transport properties of the oxidation and gasification agents O2, CO2, and H2O are highly relevant for the modeling of the conversion process of biomasses. Therefore, this study presents experimental investigations on the adsorption kinetics of O2 on a biomass char using a modified gravimetric sorption device. Based on this comprehensive set of adsorption kinetic data, a first parameterization of the pore-structure dependent kinetic adsorption (PSK) model for O2 adsorption is presented. This model intends to account for mass transport during biomass conversion in a more meaningful way as it is considered in conventional conversion models. With this parameterization, the model is capable of describing accurately the adsorption kinetics of O2 as a function of time, temperature, and pressure.
Thermal comfort is the prime purpose of Heating, Ventilation, and Air Conditioning (HVAC) systems in the indoor environment. Ideally, providing the best thermal comfort with the minimum energy consumption of HVAC systems is most desired. Cold air systems are proven to put forward energy savings with relatively low supply air temperatures ranging between 4 ℃ and 10 ℃, compared to conventional systems, which supply air at around 16℃. However, cold air systems are rarely applied due to cold draft formation and thermal comfort concerns. Thermal comfort is established by the interactions of convective and radiative heat transfers within the zone. These conditions of the thermal environment are incorporated with the occupants’ characteristics of metabolic rate associated with their activities as well as clothing (thermal insulation) into the well-established Predicted Mean Vote (PMV) index. Cold air systems were narrowly studied in terms of averaged Air Diffusion Performance Index (APDI), leading to a false representation of the system compatibility to provide thermal comfort. This paper develops a User Defined Function (UDF) combined with a Computational Fluid Dynamics (CFD) model to accurately represent thermal comfort conditions of cold air systems. The model is tested for the two-dimensional indoor zone. A scenario of variable indoor conditions is considered to identify the PMV index on the cell-sized scale in the order of 9 mm x 9 mm of the airflow in the office space. The PMV index is considered for a k–ε turbulence model for indoor airflow. In order to test the validity of the two-dimensional model estimations, PMV indices for cells are compared with the results from Center for the Built Environment (CBE) thermal comfort tool against ASHRAE-55 standard. The CFD model developed has shown the effectiveness of cold air systems for the occupied zone layer with applications of PMV based reduced-order control systems.