Search Results (349)

The stretch film production is highly energy intensive. The components of the technological line are powered by electrical energy, and the heat is used to change the physical state of the raw material (granules). The raw material is poured into FCR (the first calender roller). To solidify the liquid raw material, the calendar must be cooled. The low-temperature heat, treated as waste heat, has dissipated in the atmosphere. Technological innovations were proposed: (a) the raw material comprises raw material (primary) and up to 80% recyclate (waste originating mainly from agriculture), (b) the use of low-temperature waste heat (the cooling of FCR in the process of foil stretch production). A heat recovery line based on two compressor heat pumps (HP, hydraulically coupled) was designed. The waste heat (by low-temperature HP) was transformed into high-temperature heat (by high-temperature HP) and used to prepare the raw material. The proposed technological line enables the management of difficult-to-manage post-production waste (i.e., agriculture and other economic sectors). It reduces energy consumption and raw materials from non-renewable sources (CO₂ and other greenhouse gas emissions are reducing). It implements a closed-loop economy based on renewable energy sources (according to the European Green Deal). Full article

This study analyzes the configurations and control strategies of hybrid heating systems of air-source heat pumps (ASHPs) and gas boilers for space heating in different climatic regions in China, with the aim of improving the comprehensive energy efficiency. Parallel and series hybrid modes were proposed, and simulation analysis was conducted to analyze the energy performance, energy costs, and CO₂ emissions of different hybrid systems. The results show that the supply water temperatures of ASHPs in series mode are lower than that of ASHPs in parallel mode; thus, the COP of ASHPs in series mode reached 2.73 and was higher than the COP of ASHPs in parallel mode with a value of 2.65. Then, the optimal intermediate temperatures of hybrid system in series mode were analyzed, so as to guide the system control. The results show that compared with series mode with a fixed 50% load distribution, the operational costs and CO₂ emissions were reduced by 10.0% and 10.4% in Harbin, reduced by 6.4% and 8.3% in Beijing, and reduced by 10.0% and 15.1% in Wuhan. Additionally, the optimal intermediate temperature was affected by the building load ratio, supply water temperature, ambient air temperature, and the electricity–gas price ratio. The series-hybrid ASHP and gas boiler system achieves remarkable energy and cost savings across different climatic conditions, providing a scientific basis for promoting low-carbon heating solutions. Full article

The decarbonization of residential cooling systems requires innovative solutions to overcome the mismatch between the renewable energy availability and demand. Integrating latent thermal energy storage (LTES) with heat pump/air conditioning (HP/AC) units can help balance energy use and enhance efficiency. However, the dynamic behavior of such integrated systems, particularly under low-load conditions, remains underexplored. This study investigates a 5 kW HP/AC unit coupled with an 18 kWh LTES system using a bio-based Phase Change Material (PCM) with a melting temperature of 9 °C. Two configurations were tested: charging the LTES using either a thermostatic bath or the HP/AC unit. Key parameters such as the stored energy, temperature distribution, and cooling capacity were analyzed. The results show that, under identical conditions (2 °C inlet temperature, 16 L/min flow rate), the energy stored using the HP/AC unit was only 6.3% lower than with the thermostatic bath. Nevertheless, significant cooling capacity fluctuations occurred with the HP/AC unit due to compressor modulation and anti-frost cycles. The compressor frequency varied from 75 Hz to 25 Hz, and inefficient on-off cycling appeared in the final phase, when the power demand dropped below 1 kW. These findings highlight the importance of integrated system design and control strategies. A co-optimized HP/AC–LTES setup is essential to avoid performance degradation and to fully exploit the benefits of thermal storage in residential cooling. Full article

Increasing the temperature of waste heat is crucial to enable its recovery. Vapor compression heat pumps and absorption heat transformers are the two heat upgrade technologies most commonly used for this purpose. Heat pumps have the advantage of entirely recovering the waste heat and the disadvantage of requiring electricity as input. Heat transformers need a negligible amount of electricity but reject at part of the waste heat input at low temperature. Due to these differences, the choice between the two options depends on the application. In this work, the environmental and economic performance of heat pumps and heat transformers are compared in some relevant applications. Indications about the most suitable technology are provided based on the availability of the waste heat, of the CO₂ content of the electricity and of the electricity–gas price ratio. Heat pumps perform better when the waste heat availability is limited compared to the upgraded heat requirements and has a better environmental profile when the electricity has low carbon content. Heat transformer results are often economically convenient, especially when the availability of waste heat is large. Full article

Given the widespread use of gas-fired boilers and combined heat and power (CHP) units in existing district heating (DH) systems, this study investigates the integration of medium-scale heat pumps (HPs) into such configurations. Fifteen DH system variants were analysed, differing in installed HP capacity, operational strategies, and the synchronisation of heat and electricity production with thermal demand. A dynamic simulation model incorporating real-world equipment performance was developed to assess energy efficiency, environmental impact, and economic viability under three distinct energy price scenarios. The results demonstrate that an HP sized to 17% of the total heating capacity of the DH system achieves a 54% decrease in primary energy consumption and a 68% decrease in emissions compared to the base system. Larger HP capacities enhance environmental performance and increase the share of renewable energy but also entail higher investment. An economic analysis reveals that electricity-to-gas price ratios strongly influence the cost-effectiveness of HP integration. Under favourable electricity pricing conditions, systems with HP operational priority achieve the lowest levelized cost of heating. The most economically viable configuration consists of 600 kW HP and achieves a payback period of 4.7 years. The findings highlight the potential for HPs to decarbonize DH systems while emphasising the importance of market conditions and system design in ensuring economic feasibility. Full article

District heating systems in northern China predominantly rely on coal-fired heat sources, necessitating sustainable alternatives to reduce carbon emissions. This study investigates a biomass combined heat and power (CHP) system integrated with cascaded absorption heat pump (AHP) technology to recover waste heat from semi-dry flue gas desulfurization exhaust and turbine condenser cooling water. A multi-source operational framework is developed, coordinating biomass CHP units with coal-fired boilers for peak-load regulation. The proposed system employs a two-stage heat recovery methodology: preliminary sensible heat extraction from non-saturated flue gas (elevating primary heating loop (PHL) return water from 50 °C to 55 °C), followed by serial AHPs utilizing turbine extraction steam to upgrade waste heat from circulating cooling water (further heating PHL water to 85 °C). Parametric analyses demonstrate that the cascaded AHP system reduces turbine steam extraction by 4.4 to 8.8 t/h compared to conventional steam-driven heating, enabling 3235 MWh of annual additional power generation. Environmental benefits include an annual CO₂ reduction of 1821 tonnes, calculated using regional grid emission factors. The integration of waste heat recovery and multi-source coordination achieves synergistic improvements in energy efficiency and operational flexibility, advancing low-carbon transitions in district heating systems. Full article

Multipurpose heat pumps are devices able to provide simultaneously heating and cooling requirements. These devices concurrently provide useful thermal energy at condenser and evaporator with a single electrical energy input, potentially achieving energy savings as heat-recovery and co-generative technology. Despite their potential contribution to the energy transition goals as both renewable and energy-efficient technology, their use is not yet widespread. An application example for multipurpose heat pumps is air handlers, where cooling and reheat coils are classically fed by separate thermal generators (i.e., boiler, heat pumps, and chillers). This research aims at presenting the energy potential of multipurpose heat pumps as thermal generators of air handler units, comparing their performances with a classic separate configuration. A museum in the Mediterranean climate is selected as a reference case, as indoor temperature and relative humidity must be continuously controlled by cold and hot coils. The thermal loads at building and air handler level are evaluated through TRNSYS 17 and MATLAB 2022b, through specific dynamic models developed according to manufacturer’s data. An integrated building-HVAC simulation, on the cooling season with a one-hour timestep, demonstrates the advantages of the proposed technology. Indeed, the heating load is almost entirely provided by recovering energy at the condenser, and a 22% energy saving is obtained compared to classic separate generators. Furthermore, a sensitivity analysis confirms that the multipurpose heat pump outperforms separate generation systems across different climates and related loads, with consistently better energy performance due to its adaptability to varying heating and cooling demands. Full article

The transition to low-carbon heating systems is fundamental to achieving climate neutrality, particularly within the building sector, which accounts for a significant share of global greenhouse gas emissions. Among various technologies, heat pumps have emerged as a leading solution due to their high energy efficiency and potential to significantly reduce CO₂ emissions, especially when powered by renewable electricity. This systematic review synthesizes findings from the recent literature, including peer-reviewed studies and industry reports, to evaluate the technical performance, environmental impact, and deployment potential of air source, ground source, and water source heat pumps. This review also investigates life cycle greenhouse gas emissions, the influence of geographical energy mix diversity, and the integration of heat pumps within hybrid and district heating systems. Results indicate that hybrid HP systems achieve the lowest specific GHG emissions (0.108 kgCO₂eq/kWh of heat delivered on average), followed by WSHPs (0.018 to 0.216 kgCO₂eq/kWh), GSHPs (0.050–0.211 kgCO₂eq/kWh), and ASHPs (0.083–0.216 kgCO₂eq/kWh). HP systems show a potential GHG emission reduction of up to 90%, depending on the kind of technology and energy mix. Despite higher investment costs, the lower environmental footprint of GSHPs and WSHPs makes them attractive options for decarbonizing the building sector due to better performance resulting from more stable thermal input and higher SCOP. The integration of heat pumps with thermal storage, renewable energy, and smart control technologies further enhances their efficiency and climate benefits, regardless of the challenges facing their market potential. This review concludes that heat pumps, particularly in hybrid configurations, are a cornerstone technology for sustainable building heat supply and energy transition. Full article

To promote renewable energy utilization and enhance the environmental friendliness of refrigerants, this study presents a novel experimental investigation on a transcritical CO₂ double-evaporator heat pump water heater integrating both air and water sources, designed for high-temperature hot water production. A key innovation of this work lies in the integration of an ejector into the dual-source system, aiming to improve system performance and energy efficiency. This study systematically compares the conventional circulation mode and the proposed ejector-assisted circulation mode in terms of system performance, exergy efficiency, and the economic payback period. Experimental results reveal that the ejector-assisted mode not only achieves a higher water outlet temperature and reduces compressor power consumption but also improves the system’s exergy efficiency by 6.6% under the condition of the maximum outlet water temperature. Although the addition of the ejector increases initial manufacturing and maintenance costs, the payback periods of the two modes remain nearly the same. These findings confirm the feasibility and advantage of incorporating an ejector into a transcritical CO₂ compression/ejection heat pump system with integrated air and water sources, offering a promising solution for efficient and environmentally friendly high-temperature water heating applications. Full article

With the intensification of the global energy crisis, the application of air-source transcritical CO₂ heat pumps has attracted increasing attention, especially in cold regions. Existing research mainly focuses on the evaluation of steady-state performance while paying less attention to the dynamic characteristics of the system during the actual operation process. In order to deeply study the dynamic performance of the air-source transcritical CO₂ heat pump system under the winter climate conditions in the Yan‘an area, this study established a system simulation model with multiple parameter inputs and systematically analyzed the influences of ambient temperature, discharge pressure, and inlet and outlet water temperatures on the heating capacity and COP. The research starts from both dynamic and steady-state perspectives, revealing the variation law of system performance with environmental temperature and conducting a quantitative analysis. As the ambient temperature rose from −11 °C to 2 °C, the COP of the system increased by approximately 15% and exhibited significant dynamic response characteristics, indicating that the increase in ambient temperature significantly improved system efficiency. At different ambient temperatures, the optimal discharge pressure increased with the rise in temperature. At the highest ambient temperature (2 °C), the optimal discharge pressure was 11.7 MPa. Compared with the optimal discharge pressure of 11.0 MPa at −11 °C, the performance improved by nearly 13.3%. Through the dynamic simulation method, theoretical support is provided for the optimization of energy-saving control strategies in cold regions, and thoughts are offered regarding the application of transcritical CO₂ systems under similar climatic conditions. Full article

To investigate the operational characteristics of the supercritical carbon dioxide (S-CO₂) Brayton cycle and enhance its applicability in practical operating conditions for micro-scale reactors, an experimental platform for a recuperative S-CO₂ Brayton cycle is constructed and investigated. Several controllable operational parameters, including compressor pump frequency, expansion valve opening, and electric heating power, each intrinsically linked to the thermal characteristics of its corresponding equipment, as well as the cooling water flow rate, are systematically adjusted and analyzed. Experimental results demonstrate that the cooling water flow rate has a significantly greater impact on the temperature and pressure of the cycle system compared to other operational parameters. Based on these findings, steady-state experiments are conducted within a pressure range of 8 MPa to 15 MPa and a temperature range of 70 °C to 150 °C. It is observed that the heat exchange capacity of the recuperator decreases as the cooling water flow rate is reduced, suggesting that sufficient cooling efficiency is required to maximize the recuperative function. Under the condition of a maximum system temperature of 150 °C, the isentropic efficiency of the expansion valve decreases with an increase in the inlet pressure of the valve. However, the overall thermal efficiency of the cycle system requires further calculation and assessment following the optimization of the experimental platform. The result of validation of experimental results is less than 20%. The findings presented in this study offer essential data that encompass the potential operational conditions of the CO₂ Brayton cycle section applicable to small-scale reactors, thereby providing a valuable reference for the design and operation of practical cycle systems. Full article

This paper discusses the development of an Integrated Building Energy Model (IBEM) in MATLAB (R2024b) for a university campus building. In the general context of the development of integrated energy district models to guide the evolution and planning of smart energy grids for increased efficiency, resilience, and sustainability, this work describes in detail the development and use of an IBEM for a university campus building featuring a heat pump-based heating/cooling system and PV generation. The IBEM seamlessly integrates thermal and electrical aspects into a complete physical description of the energy performance of a smart building, thus distinguishing itself from co-simulation approaches in which different specialized tools are applied to the two aspects and connected at the level of data exchange. Also, the model, thanks to its physical, white-box nature, can be instanced repeatedly within the comprehensive electrical micro-grid model in which it belongs, with a straightforward change of case-specific parameter settings. The model incorporates a heat pump-based heating/cooling system and photovoltaic generation. The model’s components, including load modeling, heating/cooling system simulation, and heat pump implementation are described in detail. Simulation results illustrate the building’s detailed power consumption and thermal behavior throughout a sample year. Since the building model (along with the whole campus micro-grid model) is implemented in the MATLAB Simulink environment, it is fully portable and exploitable within a large, world-wide user community, including researchers, utility companies, and educational institutions. This aspect is particularly relevant considering that most studies in the literature employ co-simulation environments involving multiple simulation software, which increases the framework’s complexity and presents challenges in models’ synchronization and validation. Full article

The electrification of industrial processes offers sustainable opportunities for reducing carbon footprints and enhancing energy efficiency in the chemical industry. This paper presents the technical and environmental evaluation (life cycle assessment) of a proposed process for methanol production from the conversion of a conventional process to produce gray hydrogen by SMR technology at a plant located in the Magdalena Medio region of Colombia. The new process incorporates the concept of industrial electrification including a heat pump (HP) system with the use of propane as a working fluid for the distillation and separation system of the water–methanol mixture. The process includes the use of photovoltaic energy (PV) as a thermal supply mechanism for the methanol production process and carbon capture utilization (CCU). The proposed process is compared with a reference methanol production process that uses a dry and wet conversion mechanism. The results obtained using the HYSYS V12.1 simulation software allow identifying a 5% improvement in the performance for methanol production and a reduction in energy consumption of between 30 and 53%, which provides important perspectives on the overall energy efficiency of the process with a significant contribution to the decarbonization (−62%) of the methanol synthesis and production process. Full article

The paper presents the design and development of a universal simulation model named SustainSIM, intended for optimizing the carbon footprint in mechanical engineering production. The objective of this model is to enable enterprises to accurately quantify, monitor, and simulate CO₂ emissions generated during various manufacturing processes, thereby identifying and evaluating effective reduction strategies. The paper thoroughly examines methodologies for data collection and processing, determination of emission factors, and categorization of emissions (Scope 1 and Scope 2), utilizing standards such as the GHG Protocol and associated databases. Through a digital simulation environment created in Unity Engine, the model interactively visualizes the impacts of implementing green technologies—such as solar panels, electric vehicles, and heat pumps—on reducing the overall carbon footprint. The practical applicability of the model was validated using a mechanical engineering company as a case study, where simulations confirmed the model’s potential in supporting sustainable decision-making and production process optimization. The findings suggest that the implementation of such a tool can significantly contribute to environmentally responsible management and the reduction of industrial emissions. In comparison to existing methods such as SimaPro/OpenLCA (detailed LCA) and the Corporate Calculator (GHG Protocol), SustainSIM achieves the same accuracy in calculating Scopes 1/2, while reducing the analysis time to less than 15% and decreasing the requirements for expertise. Unlike simulation packages like Energy Plus, users can modify parameters without scripting, and they can see the immediate impact in CO₂e. Full article

The high-temperature heat pump is a favorable technology for aiding the decarbonization of the industrial sector through its electrification. It can produce useful heat up to the range of 100 °C to 200 °C; however, additional steps are needed to develop reliable and highly efficient systems. The objective of this investigation is the systematic analysis of different operating cases of high-temperature heat pumps for industrial process heat production, from 100 °C up to 180 °C, exploiting waste heat from 50 °C to 100 °C. Moreover, the case of the ambient-source heat pump is studied for different process heat temperatures using an hourly-based analysis of the Greek climate conditions. The final results are evaluated based on energy, economic and environmental criteria to estimate the feasibility of industrial high-temperature heat pumps from a holistic perspective. The results indicate system sustainability for process heat temperatures up to 160 °C and for the scenarios with higher waste heat input temperatures. For the ambient-source high-temperature heat pump, the economically viable scenario was found only for the case of heat production at 100 °C due to the significant efficiency reduction at higher temperatures. Specifically, the COP was found to be up to 1.924 for the ambient-source heat pump and up to 3.285 for the waste heat source heat pump for a waste heat source at 75 °C. The levelized cost of heating was found to be in the range of 0.0562 to 0.0977 EUR/kWh for the ambient-source heat pump and in the range of 0.0377 to 0.0869 EUR/kWh for the waste heat source heat pump. Lastly, both waste heat- and ambient-source-driven heat pumps lead to CO₂ emission reductions compared to the scenario based on a conventional natural gas boiler. Full article