Search Results (709)

Decarbonizing the German building sector by 2045 requires a rapid transformation of the heating technology stock, in which decentralized heat pumps (HPs) compete with district heating (DH) and green-gas-based solutions. Yet, the existing literature has not sufficiently resolved which segments of the building stock are most appropriately served by which low-carbon technology. This paper addresses this gap through a bottom-up, dynamic analysis using the agent-based building stock model RENDER-Building, which combines building-specific environmental heat-source potentials with DH and gas distribution infrastructure availability across Germany. Three explorative techno-economic scenarios are evaluated, differing in their electricity network charge development, DH expansion, and gas infrastructure trajectories. The modeling results show that HPs are cost-competitive over their lifetime in most building stock segments, delivering unit heat at an average cost of 11–15 ct/kWh. Between 11 and 15 million units are projected to be heated by HPs by 2045, covering 25 to 30% of building heating demand. Settlement type and local heat-source availability are found to be the primary determinants of feasibility and adoption. The findings underline the importance of ensuring the availability of energy carriers and stable long-term policies for a cost-effective and climate-friendly transformation of heating in buildings. Full article

Anthropogenic greenhouse gas (GHG) emissions from chemical manufacturing present substantial operational, compliance, and competitive challenges under international climate accords and emerging regulatory frameworks, including the European Union Corporate Sustainability Due Diligence Directive (CSDDD), the Corporate Sustainability Reporting Directive (CSRD), and the Carbon Border Adjustment Mechanism (CBAM). This study provides an empirically grounded, multi-site decarbonization framework combining longitudinal quarterly operational datasets collected from 14 industrial coating manufacturing facilities (2024–2025) with an audited baseline manufacturing facility producing 35,640 metric tonnes annually. Lifecycle GHG accounting reveals that upstream raw material procurement and synthesis (Category 4) dominate the value-chain carbon footprint, contributing 89.48% (172,557 tCO₂e) of the total 192,834 tCO₂e baseline organizational footprint. In contrast, direct stationary combustion (Category 1) and purchased electricity (Category 2 location-based) account for only 0.89% (1711 tCO₂e) and 2.46% (4741 tCO₂e), respectively. To resolve implementation trade-offs, a Multi-Criteria Decision Analysis (MCDA) framework integrates annual carbon abatement potential, Technology Readiness Level (TRL), capital intensity, and payback dynamics to establish a prioritized Six-Tier Decarbonization Hierarchy: Tier 1 (Priority 1)—upstream bio-based resin and binder substitution, delivering an estimated baseline reduction of 25,880–60,050 tCO₂e/year (13.4–31.1% of baseline emissions); Tier 2 (Priority 2)—drop-in bio-based and circular solvent replacement, achieving 4820–9640 tCO₂e/year (2.5–5.0% baseline reduction); Tier 3 (Priority 3)—thermal process electrification via high-temperature industrial heat pumps (COP 2.5–3.1), eliminating 1027–1369 tCO₂e/year; Tier 4 (Priority 4)—contractual and on-site renewable electricity procurement via corporate Power Purchase Agreements (PPAs) and solar PV (4490–4741 tCO₂e/year; 2.3–2.5% baseline reduction); Tier 5 (Priority 5)—systemic formulation transitions to waterborne, high-solids, and powder coating architectures (15,000–35,000 tCO₂e/year); and Tier 6 (Priority 6)—stream-conditional Carbon Capture, Utilization, and Storage (CCUS), strictly restricted to concentrated combustion stacks (CO₂ ≥ 8 vol%) and excluded from dilute post-thermal oxidizer off-gases (CO₂ ≤ 1–4 vol%) where capture is economically unviable ($180–$260/tCO₂e). Full article

Mulberry (Morus spp.) leaves, fruits, branches, and root bark are rich in bioactive compounds, including 1-deoxynojirimycin (1-DNJ) and γ-aminobutyric acid (GABA), supporting their potential use in food, medicinal, and feed applications. Their high moisture content, however, makes fresh materials highly susceptible to postharvest quality deterioration, making drying essential for stabilization and high-value utilization. Drying technologies involve trade-offs among efficiency, energy consumption, sensory quality, rehydration, and bioactive-compound retention. This review provides a comprehensive overview of pretreatment and drying technologies for mulberry materials, with particular attention to differences in raw-material characteristics, processing conditions, analytical methods, and reporting bases that limit direct comparisons among studies. Current evidence suggests that low-temperature, low-oxygen, or short-duration technologies, including vacuum freeze-drying, microwave drying, and microwave-vacuum drying, may better preserve quality in certain thermosensitive products, although their benefits remain product- and process-dependent. Hot-air, solar, infrared, heat-pump, and hybrid drying remain practical options for bulk products but require optimization to balance quality, energy efficiency, and scalability. For juice and functional powders, carrier selection, powder properties, and bioaccessibility require further study. Overall, the available evidence is heterogeneous, and some conclusions rely on limited mulberry-specific data or extrapolation from related plant matrices. Future research should emphasize standardized quality evaluation, harmonized reporting, kinetic modeling, multi-objective optimization, online monitoring, energy and carbon-footprint assessment, and industrial-scale validation. Full article

The widespread deployment of low-carbon technologies in households is increasing the need to reduce peak electricity demand on distribution grids. Air-source heat pumps (ASHPs) are efficient heating units, but their performance declines at low ambient temperatures, increasing winter peak demand. In rural areas, limited grid capacity can constrain their use as a sole heating source, while biomass remains widely used for space heating and contributes to fine particulate matter (PM₁₀) emissions. Unfavourable winter conditions can further increase local pollutant concentrations. This study investigates the potential operating cost savings and PM₁₀ emission reductions when using a biomass-assisted hybrid heat pump (HHP) operating in bivalent mode, while also evaluating GHG emissions relative to a monovalent ASHP, providing a combined assessment not previously applied to biomass-assisted hybrid heat pumps. A validated simulation model was developed to determine the optimal switching temperature using hourly temperature data from 23 locations across Slovenia. The results were interpolated nationally and visualised using GIS tools. The findings indicate that annual cost savings can reach up to 10% and PM₁₀ emission reductions can reach up to 20 kg for a single-family building in colder, mountainous regions. Full article

Green hydrogen production through water electrolysis is a key pathway to the decarbonization of future energy systems. However, part of the electrical input is transformed into waste heat. In this study, alkaline, proton-exchange membrane, anion-exchange membrane, and solid oxide electrolysis systems are compared in terms of operating temperature, heat generation, heat transfer medium, and integration constraints. Reported COP values for commercial high-temperature vapour-compression heat pumps range from 2.4 to 5.8, depending on operating conditions. The heat-pump technologies reviewed include vapour-compression systems with single-stage, multistage, cascade, and transcritical configurations, together with absorption and adsorption systems, with a focus on suitable working fluids and practical limitations. The review distinguishes between direct heat recovery and heat recovery assisted by heat pumps, and it identifies two main areas of application: external supply for district heating, industrial consumers, and energy communities; and internal support for feedwater preheating, water cycle integration, and steam generation. A selection framework is proposed in which source- and sink-temperature compatibility determines thermodynamic feasibility, COP characterizes heat-pump performance, and LCoH supports techno-economic comparison. Direct heat recovery should be preferred when temperatures are compatible, while heat pumps can operate as enabling technologies when temperature upgrading is required and system-level economic and environmental performance remains advantageous. Full article

Carnot batteries are promising sustainable energy storage technologies for renewable electricity utilization and grid peak shaving. For broader applicability and flexible configurations, an electric-heater-assisted reversible heat pump–organic Rankine cycle Carnot battery was investigated under two charging modes using six working fluids. A thermo-economic model was developed, comprising segmented ε-NTU heat exchangers, a pressure-ratio off-design, and levelized cost of storage. Latin hypercube sampling, Gaussian process regression, global sensitivity analysis, NSGA-II, and entropy-weight TOPSIS were used for variable identification, Pareto optimization, and decision-making. The rated pressure ratio dominates round-trip efficiency under the electric-heater-first mode, whereas the evaporation temperature of the organic Rankine cycle dominates both objectives under the heat-pump-first mode. The heat-pump-first mode achieves higher round-trip efficiency and a lower levelized cost of storage for six working fluids. The R1234yf-electric-heater-first configuration is usually suitable for applications prioritizing high-temperature heat supply. However, considering environmental friendliness and sustainability, R1233zd(E)-heat-pump-first is recommended for the system, achieving 15.709% and 0.36562 $/kWh, respectively. Admittedly, the potential transient-response advantage was not quantified by the present steady-state model, which can be further investigated in the future. Full article

The evaluation of the effectiveness and sustainability of decarbonization measures, especially but not only through electrification, is not trivial. Combustion technologies improve by small amounts year to year and as the emission factors of fuels can be considered constant across European countries; however, the emission factors of electricity generation are not uniform among countries and do not share a common trend in their evolution over time. These two aspects, the different evolution trends of electricity emission factors and the non-uniformity of these factors among countries, can lead to unexpected results: under/overestimation of carbon savings and sustainability in the long-term forecast in the massive technologic transition in both the civil and industrial sectors. This paper, using trend observations and the Myopic model, highlights possible biases in the long-term projection of CO₂ emissions savings in the industrial sector. This study focuses on a comprehensive investigation of the integration of a high-temperature heat pump into a combined cooling, heating, and power plant. A detailed assessment of the system’s energy performance is conducted through steady-state simulations under both fixed boundary conditions and annual operational scenarios, addressing building heating, cooling, and electrical requirements across varying electricity emission factors for different European countries and evolution trends until 2050, with the results compared with conventional energy production systems. Full article

The increasing integration of renewable energy sources, particularly solar and wind, has created a growing need for efficient and reliable energy storage technologies (ESTs) because of their intermittent nature. This review critically examines established and emerging ESTs, including batteries, supercapacitors, and mechanical, thermal, hydrogen, and superconducting magnetic energy storage systems, with emphasis on their technical performance, durability, response time, economic feasibility, and environmental considerations. The reviewed technologies exhibit substantial differences in their energy and power characteristics. Lithium-ion batteries, for example, provide an energy density of approximately 100–265 Wh/kg, with reported lifetimes of 2000–10,000 cycles, whereas supercapacitors offer only 5–10 Wh/kg but can withstand more than 100,000 cycles and deliver energy within seconds. Flywheel systems can achieve power densities of 1000–10,000 W/kg and operate for up to 100,000 cycles, while pumped hydro storage has a comparatively low energy density of approximately 0.5–1.5 Wh/kg but can provide service over periods exceeding 50 years. Thermal storage technologies also show considerable potential, with reported energy densities ranging from approximately 0.25 Wh/kg for sensible heat storage to 120–383 Wh/kg for thermochemical storage, depending on the materials and system configuration. Overall, the findings demonstrate that no single storage technology is optimal for all applications. Technology selection should, therefore, consider the required energy and power capacity, response time, lifetime, cost, and environmental impact, particularly when integrating variable renewable energy into modern energy systems. Full article

Liquid Air Energy Storage (LAES) is a promising large-scale storage technology for supporting the sustainable integration of intermittent renewable electricity into power grids, particularly when electricity storage is combined with waste-heat valorization, cryogenic cold recovery, and reduced exergy degradation. In this thermodynamic sense, the present study proposes a sustainability-oriented framework for the comparative and parametric exergetic analysis of LAES systems, integrating the liquefaction and discharge stages within a unified analysis. The assessment focuses on thermodynamic resource efficiency and exergy performance rather than on a complete economic, environmental, or life-cycle evaluation. The objective is to identify the components and operating parameters that most strongly influence performance and to quantify the reductions in exergy destruction and losses achieved through configuration changes and parameter variation. Three Linde–Hampson-based liquefaction configurations are compared, including arrangements with external and intermediate auxiliary pre-cooling. Improved heat-exchanger integration and temperature matching increase the structural liquefaction exergetic indicator from 7.95% in the baseline configuration to 19.28% in the two-RHX configuration. The discharge stage is assessed parametrically with respect to cryogenic pumping pressure, turbine inlet temperature, and expansion architecture. Single-stage and two-stage adiabatic expansions are compared with an ideal isothermal benchmark. The adiabatic configurations provide mechanical-work recovery together with recoverable cooling potential, whereas the isothermal case gives the highest work-recovery benchmark. Under the reference conditions, using the aggregated compressor representation adopted for the main parametric analysis, the two-stage adiabatic configuration reaches a global exergetic efficiency of 15.92% for the improved Linde–Hampson-based chain and 24.87% for the selected Claude–Heylandt reference block. Full article

Hybrid solar–thermal energy harvesting systems are an important advancement in renewable energy technology, enabling simultaneous production of electrical power and useful thermal energy within a single compact platform. However, their performance is often limited by poor heat transfer and inefficient mass transport of working fluids, leading to photovoltaic thermal degradation and significant exergy losses. This study aims to optimize heat and mass transport processes in a hybrid solar–thermal mechanical system to enhance energy recovery and ensure long-term operational reliability. A three-dimensional numerical model based on the finite volume method (FVM) was developed using the governing equations of continuity, momentum, and energy conservation. A Multi-Objective Genetic Algorithm (MOGA) was employed to determine optimal microchannel geometries by analyzing variable cross-section effects on flow behavior and thermal boundary layer disruption. At the Reynolds number of 2000, the optimized configuration increases the average Nusselt number by 43.5% compared to a smooth channel. Consequently, the photovoltaic operating temperature decreases by 12.6 °C, improving electrical efficiency by 9.3%. The system achieves a maximum thermal efficiency and net energy gain of 76.8%, while maintaining an acceptable 16.3% increase in pumping power. The results confirm that optimizing mass transport is essential for effective thermal regulation and improved energy conversion performance, providing a strong foundation for high-efficiency solar collector design. Full article

Under high-Mach-number flight conditions, the combustion chambers of hypersonic vehicles encounter extreme thermal environments marked by unilateral heating, high-heat-flux density, and supercritical pressure. Traditional hydrocarbon fuel cooling often suffers from insufficient heat sinks, high-temperature cracking and coking blockages, making it difficult to meet long-endurance thermal protection requirements. Liquid metal, due to its extremely high thermal conductivity, wide liquid phase temperature range, low Prandtl number and electromagnetic pump driving capability, has become a key technology for breaking through the bottleneck of high-heat-flux thermal protection. Apart from the magnitude of heat flux, the heat-transfer time scale (such as the characteristic thermal response time of the wall and the fluid) is also crucial. During hypersonic flight, transient thermal loads can change within milliseconds, requiring rapid thermal response. Liquid metals, due to their high thermal diffusivity, have a shorter thermal diffusion time compared to hydrocarbon fuels. This review employs a systematic literature review of approaches using gallium-indium-tin alloy, GaInSn, focusing on three core directions: the flow and heat-transfer characteristics of liquid metals, the optimization of cooling micro-channels, and the application of thermal protection systems. It summarizes the research progress at home and abroad, compares and analyzes the performance differences and applicable scenarios of typical liquid-metal working fluids, and summarizes the advantages and disadvantages of existing models, structural designs, and system schemes. The research shows that liquid metals can significantly alleviate thermal stratification and eliminate coking, and deep, narrow, tree-shaped, and biomimetic micro-channels can effectively enhance heat transfer. The liquid-metal-fuel dual-channel waste heat recovery and thermoelectric power generation system has demonstrated engineering application potential. Currently, the field still faces key challenges, such as unclear heat-transfer mechanisms under extreme conditions, the lack of general heat-transfer correlation formulas, insufficient compatibility with high-temperature materials, poor miniaturization and vibration resistance of electromagnetic pumps, and low system integration. In the future, efforts should be focused on developing multi-field coupled heat-transfer models under extreme thermal environments using engineered micro-channel structures, corrosion-resistant materials, and lightweight electromagnetic pumps, promoting the research and development of integrated thermal protection, heating and power generation systems, and providing support for the development of advanced thermal management systems for hypersonic aircraft and aviation engines. Full article

Heat pumps are core equipment for efficient low-grade thermal energy utilization and low-carbon transformation of the energy structure, offering significant energy-saving potential in building heating and industrial waste heat recovery. This paper reviews the research progress and technical challenges of compression, absorption, and adsorption heat pumps as well as nanofluid-enhanced heat transfer technology and elastocaloric heat pump systems. Air source heat pumps can delay frosting through variable frequency, heat storage, and waste heat recovery. However, accurate prediction models for performance degradation under extreme cold conditions are lacking. Although ground source and water source heat pumps exhibit significant energy efficiency advantages, ground source systems may suffer from performance degradation due to underground thermal imbalance. The application of water source systems is strictly constrained by water resource conditions. Driven by low-grade waste heat, absorption heat pumps employing traditional working pairs suffer from crystallization, corrosion, or high rectification energy consumption. The COP of a single-effect cycle under 80~100 °C waste heat is only 1.2~1.9, while hybrid cycles can reach approximately 3.2 at 120~150 °C. Although adsorption heat pumps achieve significantly improved performance under continuous heat recovery cycles, the full-scale power density of novel adsorbents such as metal–organic frameworks is inferior to the power density of traditional silica gel. Moreover, under off-design conditions, the performance drops by 23~48% compared to theoretical values. Nanofluids can enhance heat transfer, but the long-term effects of particle agglomeration at high temperatures on pump power consumption and system compatibility remain to be systematically evaluated. Elastocaloric heat pump systems can achieve refrigerant-free cooling, but current prototypes still cannot compete with traditional vapor compression systems in long-cycle fatigue reliability and power density. Current heat pump technologies generally face challenges such as insufficient adaptability to extreme conditions, bottlenecks in working fluids and materials, and a lack of long-term validation. Future research must construct a multi-source coupling optimization system, address common problems in working fluids and materials, promote long-term validation and kilowatt-level prototype demonstrations, and drive the large-scale deployment and engineering application of heat pump technology toward high efficiency, intelligence, and high reliability. Full article

Energy scarcity and subsequent global fuel market shocks have become a significant concern for the United States. Process heating in industry accounts for over half of all industrial energy usage and is almost entirely (>95%) supplied by natural gas, coal, and byproduct fuels. Many existing alternatives, technologies, and strategies can reduce dependency on this fossil fuel usage to promote energy security and competitiveness. It is expected that adoption of alternatives is limited by capital investment. A working group exploratory exercise was performed to evaluate the current barriers to alternative process heat technology adoption for the manufacturing sector. Although the working group’s findings emphasize electro-technologies due to their emergence as the central topic of discussion, we have contextualized these results by providing a fair and consistent comparison against several alternative thermal technology options. The most reported issue was the lack of financial incentives, with the second key issue for engineers and manufacturing sector decision-makers being the lack of awareness or understanding of available alternatives. This paper aims to provide an analysis of the levelized cost of heating for a variety of alternatives as part of addressing concerns from the emergent patterns reported in the exploratory exercise, as well as provide guidance on barriers to further adoption. Levelized cost of heating analysis considered the capital investment, operations and maintenance, lifespan, and fuel stream costs of various systems delivering heat to the product or process as a generalized cost per megawatt-hour delivered. The analysis indicates that biomass burners, industrial open-loop heat pumps, and central-receiver heliostat fields are at cost parity under average 2024 United States natural gas and electricity prices against well-optimized natural gas burners, though further cost reductions are necessary for consistent adoption. Full article

Hydrogen (H₂) has emerged as a promising sustainable energy vector due to its scalability, high energy density, and its ability to enable sector coupling across electricity, heating, transportation, and industry. There remains a huge technical challenge to overcome. The economic implications of low round-trip efficiency, high capital costs, the limited lifespan of fuel cells and electrolyzers, and infrastructure constraints on H₂’s relative competitiveness have not been comprehensively studied. In a comparative assessment against other storage options such as batteries, pumped hydro, and compressed air energy storage (CAES), we highlight the potential of H₂ as a grid-scale storage solution. The novelty of this paper is that it compares H₂ as a competing option with other storage technologies and highlights its unique suitability for seasonal and grid-scale applications where others fall short. The paper also discusses the technological opportunities for AI and other digital technologies in the H₂ grid. Unlike general reviews, this work emphasizes the engineering performance of H₂’s production cost and economic viability, electrolyzer technology maturity, infrastructure readiness, safety and lifecycle considerations, and provides critical synthesis and implications. With this, the paper extends beyond the theoretical capacity for H₂ and gives an engineering-focused analysis that informs the drive toward sustainable and resilient power grids. Full article

Decarbonising domestic heating stands as one of the primary climate challenges, positioning net-zero building technologies as the vital technical response. Wastewater source heat pumps (WWSHPs) serve as a thermally stable solution for household heating. Scaling this system up to an urban network level requires balancing maximum heat extraction against the risks of biological damage to downstream treatment systems from excessive temperature drops. To resolve it, this study couples a quasi-steady-state model, driven by dynamic, 30 min time-series inputs, with a Genetic Algorithm (GA) to optimise a 41-pipe sewer network in Belgium. Significant results demonstrate that the GA configuration enhanced potential heat recovery by 51.7% relative to unoptimised baselines, elevating yields from 29 MW to 44 MW. Furthermore, this research identified a mass compensation effect in winter that effectively counterbalanced seasonal drops in wastewater temperature, resulting in nearly identical winter and summer average heat recovery capacities (17.409 MW vs. 17.492 MW, a variance under 0.5%). From these findings, it can be concluded that while network-scale thermal potential is exceptionally robust year-round, a profound seasonal mismatch exists between available supply and localised consumer heating requirements, which drop to a minimum of 712 kW in July but exceed 51 MW in winter. Full article