Search Results (60)

In response to the significant seasonal fluctuations in heating and cooling loads in greenhouses for high-value fruit trees in northern China, as well as issues such as heat accumulation on the ground-source side and high carbon emissions from coal-fired heating, this paper proposes a coupled energy supply system comprising a PVT system, a mine pit seasonal thermal storage unit, a ground-source heat pump and a cooling tower. Taking a 30,000 m² cherry greenhouse and an existing 15,000 m³ mine pit thermal storage reservoir in Weifang, Shandong Province, as the research objects, annual design-stage simulations with a 0.125 h time step were conducted using SketchUp-TRNBuild and TRNSYS. Discrete sensitivity analyses and engineering constraints were used to determine the PVT area and cooling tower outlet temperature. Heating demand mainly occurred from November to February, whereas cooling demand was concentrated from June to September. The selected 2452 m² PVT system supplied direct heating for 34 days, covered 23.05% of the seasonal heating demand, and achieved a storage efficiency of 69.17%. Without a cooling tower, the first-year soil temperature increased by 1.1 °C. With a 26 °C cooling tower outlet temperature, the soil thermal imbalance ratio decreased to 2.4%, and the 15-year soil temperature rise was limited to 0.28 °C. The recommended system required 1.3239 million kWh of net purchased electricity annually, reduced operating costs by approximately CNY 802,800 (USD 118,243) and operational emissions by 2027.8 tCO₂-eq per year relative to the baseline, and had a static payback period of 6.4 years. The annual operational emission reduction was linearly extrapolated over a 20-year assessment period under fixed weather, load, equipment performance, and grid emission assumptions, resulting in a scenario-based carbon reduction threshold of 40,556 tCO₂-eq. Net life cycle carbon savings would be possible if the additional emissions from construction, equipment replacement, and end-of-life treatment remained below this threshold. Full article

Wet cooling towers are widely used for low-energy thermal management and ventilation support; however, high-fidelity simulations are computationally expensive for large design studies. This work develops a physics-based static reduced-order model for a two-dimensional axisymmetric counterflow wet cooling tower derived from computational fluid dynamics (CFD) simulations coupled with a user-defined source-term formulation for heat and mass transfer in the fill region. A design of experiments based on advanced Latin hypercube sampling generated 210 configurations, of which 168 valid simulations were retained. The active inputs included tower diameter, fill height, inlet air mass flow rate, inlet air temperature, inlet humidity ratio, inlet water mass flow rate, and inlet water temperature, while the cooling range and evaporation rate were selected as target outputs. Five surrogate families were compared by cross-validation. Kriging was statistically most accurate, with $R_{CV}^2$ values of 0.9999 and 0.9998 for the cooling range and evaporation rate, respectively. Second-order quadratic polynomial models were selected as the engineering reduced order model (ROM) because they capture non-linear boundary curvatures with accuracy, achieving $R_{CV}^2\ge 0.9989$ and root mean square errors of 0.0426 K and 0.00042 kg/s while preserving an explicit, directly implementable algebraic form. Sensitivity analysis indicated that the inlet water temperature and air mass flow rate are dominant factors within the sampled domain. Full article

The residential sector accounts for a significant portion of global energy demand, which can be met through sustainable alternatives such as solar energy. This study evaluated the energy, exergy, environmental, and exergy-sustainability performance of three waste heat recovery configurations (double-loop organic Rankine cycle—DORC, Kalina cycle—KC, and organic Rankine cycle—ORC) coupled to a supercritical CO₂ Brayton cycle with intercooling and reheating, designed to meet the demand of a residential complex of 120 homes in the Colombian Caribbean region, built with four different materials, using a concentrated solar power tower as the heat source. Mass, energy, and exergy balances were performed, along with a life cycle analysis, sizing the systems to supply a cooling load of 133 kW. The results show that the three configurations meet the required demand, with energy efficiencies above 50%: sCO₂-DORC (51.7%), sCO₂-ORC (51.61%), and sCO₂-KC (51.32%), with a maximum exergy efficiency for sCO₂-DORC (24.3%). The environmental analysis indicates that the construction phase accounts for more than 95% of total emissions. Overall, the results confirm the viability of these configurations for residential applications, promoting the integration of renewable energies and supporting the regional energy transition. Full article

Conventional solar power tower (SPT) systems often suffer from significant heat transfer exergy destruction due to large temperature differences between the heat source and the working fluid during the heat exchange process. To overcome this limitation, a high–low dual-tower configuration based on segmented thermal utilization is proposed. In this arrangement, the high-temperature tower is mainly responsible for the evaporation, superheating, and reheating processes, whereas the low-temperature tower primarily handles feedwater preheating. Such a configuration improves the temperature matching characteristics during the heat exchange process. A comprehensive model integrating the heliostat field, receiver, thermal energy storage system, and power block was developed and validated against Solar Two experimental data, showing good agreement. Comparative analyses were conducted under identical solar resource and operating conditions. The results indicate that the proposed system achieves a comparable power output while reducing total heat transfer exergy destruction by approximately 24%, with a significant reduction of over 80% in the preheating section. Sensitivity analysis further reveals that optimizing the high tower outlet temperature can effectively reduce irreversibility and slightly enhance power output, although constrained by the pinch temperature difference. Dynamic simulations based on typical meteorological year data demonstrate that the system maintains stable operation and improves cycle efficiency. From an economic perspective, the proposed system reduces the levelized cost of electricity (LCOE) by about 6.6% and shortens the dynamic payback period, indicating enhanced long-term competitiveness. Overall, the high and low dual-tower system effectively improves thermodynamic and economic performance, providing a promising approach for high-efficiency concentrating solar power (CSP) development. Full article

To address the issue of performance degradation resulting from continuous thermal accumulation in the soil for conventional ground source heat pump (GSHP) systems in cooling-dominated regions, a hybrid ground source heat pump–domestic hot water system (HGSHP-DHW) is proposed, along with a corresponding mode-switching control strategy. The heat pumps for cooling, heating, and domestic hot water in the HGSHP-DHW share the same ground heat exchanger (GHE) group. To accommodate varying energy demands in different seasons, the configuration of the ground source/side loop is switched according to signals from the control strategy. The average soil temperature rise, the coefficient of performance (COP) of the heat pump units, the system performance factor (SPF), the life cycle climate performance (LCCP), and the net present value (NPV) are selected as comprehensive evaluation indicators for fifteen years of operation. A comparative analysis with traditional systems, including chiller–boiler (CB), cooling tower coupled hybrid ground source heat pump (CT-HGSHP) and GSHP, which are all equipped with an air source heat pump (ASHP) for DHW, is also conducted. By the 15th year, the average soil temperature rise in the HGSHP-DHWs is 4.94 °C, a reduction of 55.5%, effectively alleviating soil thermal accumulation. In terms of energy efficiency, the SPF is 3.79, an increase of 70.8% with 43% reduction in the accumulation of energy consumption (P_ac), achieving high-efficiency and energy-saving operation. For environmental performance, the LCCP is 2,435,587 kgCO₂, a reduction 38.8% in carbon emissions, showing a remarkable emission reduction effect. In respect of economic returns, the NPV is 644,867 CNY, which is positive and indicates favorable investment viability. Full article

Ground source heat pump (GSHP) systems, while energy-efficient, often face persistent soil thermal imbalance in heating-dominated severe cold regions, which undermines their long-term performance and sustainability. This study proposes a TRNSYS-GenOpt framework for the life-cycle cost optimization of hybrid GSHP systems integrating electric boilers and geothermal regulation towers. A transient model for a 5650 m² fire station in Changchun was developed, employing the Hooke–Jeeves algorithm to co-optimize boiler capacity, borehole depth, and geothermal regulation tower airflow under constraints on heating supply temperature and soil thermal balance. Time-of-use electricity pricing was incorporated for realistic operational economics. The optimized configuration (148 m, 864.8 kW, 290,400 m³/h) achieved a minimum 20-year life-cycle cost of CNY 1.13 million. Sensitivity analysis revealed “rigid design, flexible cost” characteristics: optimal parameters remained invariant across discount rate variations (3.5–7.5%) and equipment costs (±20%), while life-cycle cost showed the highest sensitivity to electricity pricing and discount rates. The long-term simulation confirmed compliance with all physical constraints. This methodology demonstrates that thermodynamic constraints supersede economic trade-offs in severe cold climates, providing engineers with a reliable tool for sustainable hybrid geothermal system design. Full article

Indoor swimming pools require ventilation and precise temperature and humidity control, leading to significant energy consumption. This study investigated the use of liquid desiccant technology to reduce energy consumption for heating and dehumidification of two indoor swimming pools in a UK leisure centre. Through dynamic modelling and techno-economic analysis, this research quantified heat losses in the pools, simulated the performance of liquid desiccant technology, evaluated the economic benefits and cost implications of regenerating the desiccant solution using waste heat, and assessed the feasibility of adopting the technology across the entire UK. The results showed that evaporative losses were the dominant heat loss mechanism for both pools, while the proposed liquid desiccant system effectively maintained optimal temperature and humidity conditions. Additionally, pool water can serve as a heat sink after desiccant regeneration, thereby reducing the energy demand for pool water heating. Energy consumption could be reduced by 68.9–76.7% when using a cooling tower and 77.5–88.1% when using pool water for heat rejection, with internal rates of return that can exceed 15% for the most cost-effective configurations. If the regeneration heat is sourced externally, up to £34.7/MWh could be paid for the heat required while ensuring the cost-effectiveness of the process. These findings suggest that liquid desiccant systems can reduce heating and dehumidification energy in indoor swimming pools when low-temperature heat is available for regeneration. Future research should focus on experimental validation, addressing interactions with chlorine gases, long-term system performance and real-world implementation challenges to ensure commercial deployment. Full article

Geothermal energy is recognized as one of the most reliable and environmentally sustainable energy sources. This study presents a comprehensive energy, exergy, economic, and exergoenvironmental assessment of the Mis I binary geothermal power plant (GPP) operating with a low-temperature geothermal resource. This study fills a critical gap in the literature by providing a four-dimensional (4-E) assessment—energy, exergy, economic, and exergoenvironmental—of the Mis I binary geothermal power plant (GPP). Unlike conventional studies that focus on theoretical models, this research utilizes real-time operational data to identify potential improvements at the component level by evaluating exergy-based environmental sustainability and economic performance. The energy efficiency of the n-Pentane Rankine cycle was calculated as 39.76%, indicating that a substantial portion of the geothermal heat is rejected as waste. The exergy input to the plant was determined to be 18,580.29 kW, while the net electrical power output was 8990 kW, resulting in an overall exergy efficiency of 48.38%. These results highlight the clear disparity between energy and exergy efficiencies and underline the importance of exergy-based performance evaluation for low-temperature geothermal power systems. Component-level exergy balance analyses were conducted using real operating data, revealing that the cooling towers are the dominant sources of exergy destruction, whereas the turbine units exhibit comparatively high thermodynamic effectiveness. Improvement potential analysis identified cooling towers I–II, evaporator II, and preheater I as key components requiring further optimization. Economic evaluation showed that approximately 64% of the total investment cost is associated with turbine units, with a total plant cost of about USD 6.7 million. The levelized cost of electricity was calculated as 0.0136 USD/kWh, and the payback period was approximately 1.5 years. Exergoenvironmental results indicate that the Mis I GPP achieves the highest sustainability index (1.94) among comparable plants, confirming its superior thermodynamic, economic, and environmental performance. Full article

Daily evapotranspiration (ET) estimated from an unoccupied aerial system (UAS) could help improve irrigation practices, but its spatial resolution needs to be upscaled to coarser pixel resolutions before applying surface energy balance models. The purpose of this study was to evaluate the impact of various energy balance-based aggregation schemes on generating spatially distributed latent heat flux (LE), and, in comparison, to existing occupied aircraft and satellite remote sensing platforms. In 2017, UAS multispectral and thermal imagery, along with ground truth data, were collected at various cotton growth stages. These data sources were combined to model LE using a Two-Source Energy Balance Priestley–Taylor (TSEB-PT) model. Several UAS aggregation schemes were tested, including the mode of aggregation (i.e., input image and output flux) as well as the averaging scheme (i.e., simple aggregation vs. Box–Cox). Results indicate that output flux aggregation with Box–Cox averaging produced the lowest relative upscaling pixel-scale variability in LE and the lowest absolute prediction errors (relative to eddy covariance flux tower measurements). Output flux aggregation with simple averaging was also more accurate in reproducing LE from occupied aircraft and satellite imagery. Although results are limited to a single site, UAS LE estimates were reliably aggregated to coarser pixel resolutions, which made for faster image processing for operational applications. Full article

The increasing frequency, intensity, and duration of heatwaves and droughts pose significant societal and environmental challenges across Europe. This study analyzes land surface temperature (LST) observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) between 2003 and 2023 to identify thermal anomalies associated with heatwaves. Additionally, this study examines the role of different land cover types in modulating heatwave impacts, employing turbulent flux observations from micrometeorological towers. The interaction between heatwaves and droughts is further explored using the Standardized Precipitation Evapotranspiration Index (SPEI) and soil moisture data, highlighting the amplifying role of water stress through land–atmosphere feedbacks. The results reveal a statistically significant upward trend in LST-derived thermal anomalies, with the 2022 heatwave identified as the most extreme event, when approximately 75% of Europe experienced strong positive anomalies. On average, 91% of heatwave episodes identified in reanalysis-based air temperature records coincided with LST-defined anomaly events, confirming LST as a robust proxy for heatwave detection. Flux tower observations show that, during heatwaves, evergreen coniferous and mixed forests predominantly enhance sensible heat fluxes (mean anomalies during midday of 74 W/m² and 62 W/m², respectively), while grasslands exhibit increased latent heat flux (89 W/m²). Notably, under extreme compound heat–drought conditions, this pattern reverses for grassed sites due to rapid soil moisture depletion. Overall, the findings underscore the combined influence of surface temperature and drought in driving extreme heat events and introduce a novel, multi-source approach that integrates satellite, reanalysis, and ground-based data to assess heatwave dynamics across scales. Full article

The industrial sector accounts for approximately 65% of global energy consumption, with projections indicating a steady annual increase of 1.2% in energy demand. In the context of growing concerns about climate change and the need for sustainable energy solutions, solar thermal energy has emerged as a promising technology for reducing reliance on fossil fuels. With its ability to provide high-efficiency heat for industrial processes at temperatures ranging from 150 °C to over 500 °C, solar thermal power generation offers significant potential for decarbonizing energy-intensive industries. This review provides a comprehensive analysis of various solar thermal technologies, including parabolic troughs, solar towers, and linear Fresnel reflectors, comparing their effectiveness across different industrial applications such as process heating, desalination, and combined heat and power (CHP) systems. For instance, parabolic trough systems have demonstrated optimal performance in high-temperature applications, achieving efficiency levels up to 80% for steam generation, while solar towers are particularly suitable for large-scale, high-temperature operations, reaching temperatures above 1000 °C. The paper also evaluates the economic feasibility of these technologies, showing that solar thermal systems can achieve a levelized cost of energy (LCOE) of USD 60–100 per MWh, making them competitive with conventional energy sources in many regions. However, challenges such as high initial investment, intermittency of solar resource, and integration into existing industrial infrastructure remain significant barriers. This review not only discusses the technical principles and economic aspects of solar thermal power generation but also outlines specific recommendations for enhancing the scalability and industrial applicability of these technologies in the near future. Full article

Cooling water, a crucial component of the central air conditioning setup, exerts a relatively minor direct impact on the thermal comfort of building indoor environments while it has a great effect on the system’s energy efficiency. Numerous studies exist on the cooling water system, particularly focusing on the process by which the cooling tower system operates, but the linkage between the chiller and the cooling tower is typically overlooked. When the connection is long and the passage environment for the pipeline is not conventional, it cannot be neglected for the optimal control for system efficiency improvement and energy consumption reductions. Throughout this research, a control strategy of the cooling water system for deep subway stations with long pipelines is presented. This cooling system was connected with outdoor cooling towers through a corridor about one hundred meters long. In this process, the cooling water temperature is influenced by the corridor’s thermal environment. For this study, an online control strategy optimizes the cooling water temperature, and a simulation platform of the air conditioning cooling water system of the deep subway station was also developed to evaluate the energy-saving potential of the control strategy of this cooling water system. Atop this platform, a simplified heat transfer model of the pipe corridor was created to determine the cooling capacity provided by the cooling water pipe in the corridor. The outcomes suggest that, as opposed to the conventional control mode, the energy-saving ratio of the optimal control strategy during a typical day may reach 4.1%, and the cooling source system’s Coefficient of Performance (COP) might see an increase of about 4.2%. The energy consumption of the water system throughout the whole cooling season may decrease by 9778 kWh, and the energy-saving rate is 4.1%. The results also demonstrate that the cooling water pipes release heat to the air in the corridor most of the time, and the released heat is larger than the absorbed heat. The maximum heat dissipation to the air in the corridor from the cooling water supply and return pipe can be up to 24.3 kW. The cooling effect of the corridor of subway stations with large depths below the ground surface cannot be ignored when optimal control is considered for the cooling water system. Full article

This review examines the integration of ground source heat pump (GSHP) systems with energy piles as a sustainable approach to improving energy efficiency in smart cities. Energy piles, which combine structural support with geothermal heat exchange, offer significant advantages over conventional air source heat pumps (ASHPs) by using stable ground temperatures for more efficient heating and cooling. System efficiency can be improved by integrating hybrid systems, cooling towers, and solar thermal systems. While the initial investment for GSHP systems is higher, their integration with energy piles significantly reduces electricity consumption and operating costs, providing a compelling solution for regions with high energy demand and escalating energy prices. Government financial incentives, including subsidies, loans, and tax rebates, can reduce payback periods to less than 10 years, encouraging the adoption of energy piles and GSHP systems. The paper analyzes heat transfer mechanisms in energy piles, particularly the role of groundwater circulation in improving heat dissipation and overall system performance. It also discusses optimized design considerations, performance metrics, and economics, highlighting the critical role of site-specific conditions from thorough site surveys and strategic planning of adaptive management to adjust system operations based on real-time demand in optimizing the benefits of geothermal energy systems. This review serves as a comprehensive guide for engineers and researchers in the effective application of energy piles within urban infrastructure, thereby supporting sustainable urban development and mitigating the urban heat island effect. Full article

Accurate assessment of net primary production (NPP) can truly reflect the carbon budget balance of the forest ecosystem. In this study, the boreal ecosystem productivity simulation (BEPS) model was used to simulate the NPP of Saihanba mechanized forest farm in 2020, and the influencing factors of NPP were analyzed. The meteorological, forest cover, leaf area index (LAI) and other data required for the model, as well as the data for verifying, were from field surveys or downloaded from different sources. The results showed that: (1) Within the scale of the flux tower, the diurnal variation of NPP reached a maximum in June. The monthly average peak value of latent heat flux was in June, and the sensible heat flux was in March. The temperature of the understory canopy was mostly higher than that of the overstory canopy and air temperature. (2) At the regional scale, the total NPP in the study area in 2020 was 4.25 × 10¹¹ g C a⁻¹, with an average of 564.71 g C m⁻² a⁻¹. The annual average NPP of silver birch (Betula platyphylla) was the largest, and the total NPP of northern Chinese larch (Larix principis-ruprechtii) was the largest. (3) NPP was highly sensitive to LAI. Topographic factors had effects on NPP. The average value of NPP was relatively high in the shady slope and the gentle slope. Full article

Prescribed burning is a cost-effective method for reducing hazardous fuels in pine- and oak-dominated forests, but smoke emissions contribute to atmospheric pollutant loads, and the potential exists for exceeding federal air quality standards designed to protect human health. Fire behavior during prescribed burns influences above-canopy sensible heat flux and turbulent kinetic energy (TKE) in buoyant plumes, affecting the lofting and dispersion of smoke. A more comprehensive understanding of how enhanced energy fluxes and turbulence are related during the passage of flame fronts could improve efforts to mitigate the impacts of smoke emissions. Pre- and post-fire fuel loading measurements taken during 48 operational prescribed burns were used to estimate the combustion completeness factors (CC) and emissions of fine particulates (PM_2.5), carbon dioxide (CO₂), and carbon monoxide (CO) in pine- and oak-dominated stands in the Pinelands National Reserve of southern New Jersey. During 11 of the prescribed burns, sensible heat flux and turbulence statistics were measured by tower networks above the forest canopy. Fire behavior when fire fronts passed the towers ranged from low-intensity backing fires to high-intensity head fires with some crown torching. Consumption of forest-floor and understory vegetation was a near-linear function of pre-burn loading, and combustion of fine litter on the forest floor was the predominant source of emissions, even during head fires with some crowning activity. Tower measurements indicated that above-canopy sensible heat flux and TKE calculated at 1 min intervals during the passage of fire fronts were strongly influenced by fire behavior. Low-intensity backing fires, regardless of forest type, had weaker enhancement of above-canopy air temperature, vertical and horizontal wind velocities, sensible heat fluxes, and TKE compared to higher-intensity head and flanking fires. Sensible heat flux and TKE in buoyant plumes were unrelated during low-intensity burns but more tightly coupled during higher-intensity burns. The weak coupling during low-intensity backing fires resulted in reduced rates of smoke transport and dispersion, and likely in more prolonged periods of elevated surface concentrations. This research facilitates more accurate estimates of PM_2.5, CO, and CO₂ emissions from prescribed burns in the Pinelands, and it provides a better understanding of the relationships among fire behavior, sensible heat fluxes and turbulence, and smoke dispersion in pine- and oak-dominated forests. Full article