Search Results (106)

Global building energy consumption is significantly increasing. Utilizing renewable energy sources may be an effective approach to achieving low-carbon and energy-efficient buildings. A combined system incorporating solar photovoltaic–thermal (PV/T) components with an air-source heat pump (ASHP) was studied for simultaneous heating and power generation in a real residential building. The back panel of the PV/T component featured a novel polygonal Freon circulation channel design. A prototype of the combined heating and power supply system was constructed and tested in Fuzhou City, China. The results indicate that the average coefficient of performance (COP) of the system is 4.66 when the ASHP operates independently. When the PV/T component is integrated with the ASHP, the average COP increases to 5.37. On sunny days, the daily average thermal output of 32 PV/T components reaches 24 kW, while the daily average electricity generation is 64 kW·h. On cloudy days, the average daily power generation is 15.6 kW·h; however, the residual power stored in the battery from the previous day could be utilized to ensure the energy demand in the system. Compared to conventional photovoltaic (PV) systems, the overall energy utilization efficiency improves from 5.68% to 17.76%. The hot water temperature stored in the tank can reach 46.8 °C, satisfying typical household hot water requirements. In comparison to standard PV modules, the system achieves an average cooling efficiency of 45.02%. The variation rate of the system’s thermal loss coefficient is relatively low at 5.07%. The optimal water tank capacity for the system is determined to be 450 L. This system demonstrates significant potential for providing efficient combined heat and power supply for buildings, offering considerable economic and environmental benefits, thereby serving as a reference for the future development of low-carbon and energy-saving building technologies. 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

This paper establishes an explicable integrated machine learning model for predicting the discharge water quality in a circulating cooling water system of a power plant. The performance differences between three deep learning models, a Temporal Convolutional Network (TCN), Long Short-Term Memory (LSTM), and a Convolutional Neural Network (CNN), and traditional machine learning models, namely eXtreme Gradient Boosting (XGboost) and Support Vector Machine (SVM), were evaluated and compared. The TCN model has high fitting accuracy and low error in predicting ammonia nitrogen, nitrate nitrogen, total nitrogen, chemical oxygen demand (COD), and total phosphorus in the effluent of a circulating cooling tower. Compared to other traditional machine learning models, the TCN has a larger R² (maximum 0.911) and lower Root Mean Square Error (RMSE, minimum 0.158) and Mean Absolute Error (MAE, minimum 0.118), indicating the TCN has better feature extraction and fitting performance. Although the TCN takes additional time, it is generally less than 1 s, enabling the real-time prediction of drainage water quality. The main water quality indices have the greatest causal inference relationship with those of makeup water, followed by the concentration ratio, indicating that concentrations of ammonia nitrogen, nitrate nitrogen, total nitrogen, and COD have a more decisive impact. Shapley Additive Explanations (SHAP) analysis further reveals that the concentration ratio has a weaker decisive impact on circulating cooling water drainage quality. The results of this study facilitate the optimization of industrial water resource management and offer a feasible technical pathway for water resource utilization in power plants. Full article

The subject of the current paper is cooling heat sinks using the TPMS structure. An experiment was conducted using water and a mixture of 10% vol. ethylene glycol in water, which was used to cool heat sinks in the presence of the TPMS structure. The gyroid was developed using 3D printing with three different porosities: 0.7, 0.8, and 0.9, respectively. The shell network is a single domain, and fluid is circulated at various flow rates. A comparison with the numerical model, as simulated using COMSOL software (version 6.2), showed good agreement. A uniform temperature distribution is a clear indication of uniform cooling. Then, the TPMS structure is changed from one domain to two unconnected domains, and a different flow rate is applied to each domain entry. This approach is unique in that it investigates the cooling of the heat sink with a two-domain structure, which has not been previously studied. The novelty of this paper lies in utilizing two TPMS structure domains to cool the heat sink. Thus, dual-domain TPMS heat sinks are implemented and optimized with separate inlets. Statistical testing of the model for the Nusselt number and the performance evaluation criterion is performed using Fisher’s statistical test to analyze variance (ANOVA). It was found that the cooling heat sink is more accurate with two-domain systems. The average Nusselt number polynomial is found to vary linearly with the two-inlet velocity, the porosity and the fluid Prandtl number. Similar linearity is found for the performance evaluation criterion. The optimum Nusselt number equals 77, the PEC equals 49 for a porosity of 0.85, and the Prandtl number is 36.9. Full article

This paper presents energy and exergy studies on a photovoltaic-thermal solar-assisted geothermal heat pump coupled with a radiant ceiling system. The system utilizes renewable solar and geothermal energy. It has an independent fresh air unit that provides clean air to the space. The computer model of the system was developed under the TRNSYST environment and validated with experimental results from open literature. Distribution of the energy consumption and exergy loss of the system were analyzed. It was found that the heat pump unit consumes the largest amount of energy while the transmission and distribution system has the highest exergy loss. Under optimized operating conditions, i.e., both demand side circulation flow and source side circulation flow are maintained at 65% of the design flow rate (design loop water temperature difference of 7.0 °C), the average exergy efficiency of the whole system was found to be 37.56%, which achieves an accumulative exergy loss reduction of 16.5% compared with 100% design flow rate condition during cooling season. The optimal bearing load ratio of the ground source heat pump vs. photovoltaic-thermal system in the heating season was found to be 67%. Full article

This study presents a preliminary analysis of an innovative system that combines indoor air conditioning with water recovery and storage. The device integrates Peltier cells with a horizontal Earth-to-Air Heat Exchanger (EAHX), exploiting the ground stable temperature to enhance cooling and promote condensation. Warm, humid air is pre-cooled via the geothermal pipe, then split by a fan into two streams: one passes over the cold side of the Peltier cells for cooling and dehumidification, while the other flows over the hot side and heats up. The two airstreams are then mixed in a water storage tank, which also serves as a thermal mixing chamber to regulate the final air temperature. The analysis investigates the influence of soil thermal conditions on condensation within the horizontal pipe and the resulting cooling effect in indoor spaces. A hybrid simulation approach was adopted, coupling a 3D model implemented in COMSOL Multiphysics^® with a 1D analytical model. Boundary conditions and meteorological data were based on the Typical Meteorological Year (TMY) for Palermo. Two scenarios were considered. In Case A, during the hours when air conditioning is not operating (between 11 p.m. and 9 a.m.), air is circulated in the exchanger to pre-cool the ground and the air leaving the exchanger is rejected into the environment. In Case B, the no air is not circulated in the heat exchanger during non-conditioning periods. Results from the June–August period show that the EAHXs reduced the average outdoor air temperature from 27.81 °C to 25.45 °C, with relative humidity rising from 58.2% to 66.66%, while maintaining nearly constant specific humidity. The system exchanged average powers of 102 W (Case A) and 96 W (Case B), corresponding to energy removals of 225 kWh and 212 kWh, respectively. Case A, which included nighttime soil pre-cooling, showed a 6% increase in efficiency. Condensation water production values range from around 0.005 g/s with one Peltier cell to almost 0.5 g/s with seven Peltier cells. As the number of Peltier cells increases, the cooling effect becomes more pronounced, reducing the output temperature considerably. This solution is scalable and well-suited for implementation in developing countries, where it can be efficiently powered by stand-alone photovoltaic systems. Full article

This research was conducted to evaluate and compare the efficiency of the modern external type thrust bearing cooling system (TBCS) with plate-type heat exchangers (PTHEs) applied as an alternative to standard design external type TBCS with shell-and-tube heat exchangers (STHEs) in a 180 MW large hydro power plant by experimental methods. Although similar studies are available in the literature, there is no comprehensive study on the effects of different parameters on performance and other plant parameters. The main parameters examined in the study are the cooling rate, oil temperature difference, average pad temperature (APT), and generator winding temperature. The tests were carried out over the range of 144–150.1 MW unit loads, 580–1317 L/min water flow rates, and 998–1411 L/min oil circulation flow rates. The results showed that the APT can only be reduced up to 73.4 °C at 1411 L/min oil circulation flow rate by 252.6 kW cooling, the optimum oil circulation flow rate is 1195 L/min, APT can be reduced by 1.7 °C and the maximum winding temperature by 1.3 °C when external type TBCS with PTHEs is used, and structural changes must be made in the thrust bearing design to provide further decrease in pad temperature. Full article

As a critical component of nuclear power units, the direct cooling water system plays a key role in overall performance. To maintain economic efficiency, it is necessary to adjust the circulating water flow rate as conditions change. Understanding how this system responds dynamically to varying environmental factors—such as seawater temperature and tidal levels—is essential for precise control. While previous studies have explored methods such as variable frequency control, predictive maintenance, and digital twin technologies to optimize system operations, challenges remain in addressing the dynamic response of cooling systems under complex environmental and operational conditions. In this study, the AP1000 was used as the research subject and a comprehensive mathematical model of each part of the cooling water system was built, accounting for delays in processes like pipeline transport. Sensitivity analyses were then carried out to examine how linear disturbances in environmental parameters affect system performance, and how circulating water flow, condenser back pressure, and unit efficiency are interrelated. At the same time, the frequency conversion circulating water pump adaptive adjustment system is used to find the best vacuum conditions according to the change in seawater parameters. The findings offer valuable guidance for enhancing the economic operation of nuclear power plant cooling systems. Full article

Scaling is one of the common problems in circulating cooling water systems, which can significantly affect the cooling efficiency of equipment in severe cases. At present, the problem of scaling is usually controlled by adding water treatment agents. However, taking the external cooling system of the synchronous condenser in an ultra-high-voltage converter station as an example, due to the lack of scientific understanding of scale inhibitors, there is often a problem of excessive dosing, resulting in unsatisfactory scale inhibition effects and difficulties in wastewater treatment and discharge. In addition, the extensive use of phosphorus-containing agents has led to the enrichment of phosphorus elements in water bodies. Therefore, the optimal amount of AS-582 scale inhibitor used in the converter station with the best scale inhibition effect was determined through static calcium carbonate deposition experiments, with the scale inhibition rate of 91.4% at 90 mg/L. And the scale inhibition mechanism was explored, where the lattice distortion mechanism and threshold effect play important roles. The AS-582 scale inhibitor was mixed with two green scale inhibitors, PASP and PESA, to obtain a phosphorus reduction formula that combined excellent scale inhibition performance and low phosphorus content. When using the optimal composite scale inhibitor of n(AS-582):n(PASP):n(PESA) = 4:1:1, the scale inhibition rate is 91.8% and the phosphorus content is reduced by one-third. The effectiveness of the formula was tested using dynamic circulating water experimental equipment under practical application conditions, proving its practical value. Full article

As an important part of industrial production, the optimization of circulating water systems is of great significance for improving energy efficiency and reducing operating costs. However, traditional optimization methods lack real-time and dynamic adjustment capabilities and often cannot fully cope with the complex and changeable industrial environment and energy demands. Advances in computer technology can enable people to use machine learning models to process information and data and ultimately help simplify simulation and optimization. In this paper, the circulating water system of a Fluid Catalytic Cracking (FCC) unit is optimized and evaluated based on process simulation and machine learning, adopting 284 sets of industrial operating data. The cooler network of the system is modified from a parallel structure to a series mode, and the effect is clarified using the ASPEN HYSYS software V12. Meanwhile, the fan power of the cooling tower is predicted by employing an optimized Gradient Boosting Regression (GBR) model, and the influence of the parallel-to-series transformation on the fan power is discussed. It is shown that the computer modeling results are in coincidence with the industrial data. Converting the parallel design to a series arrangement of the cooler network can significantly decrease the water consumption, with a reduction of 11%. The fan power of the cooling tower is also reduced by 8% after the optimization. Considering the changes in both water consumption and fan power, the saved total economic cost is 8.65%, and the decreased gas emission is 2142.06 kg/h. By building the optimization prediction system, the real-time sequencing and monitoring of equipment parameters are realized, which saves costs and improves process safety. Full article

Hydrogen production from renewable energy sources is a crucial pathway to achieving the carbon peak target and realizing the vision of carbon neutrality. The hydrogen production from offshore superconducting wind power (HPOSWP) integrated systems, as an innovative technology in the renewable energy hydrogen production field, holds significant market potential and promising development prospects. This integrated technology, based on research into high-temperature superconducting generator (HTSG) characteristics and electrolytic water hydrogen production (EWHP) technology, converts offshore wind energy (OWE) into hydrogen energy locally through electrolysis, with hydrogen storage being shipped and controlled liquid hydrogen (LH₂) circulation ensuring a stable low-temperature environment for the HTSGs’ refrigeration system. However, due to the significant instability and intermittency of offshore wind power (OWP), this HPOSWP system can greatly affect the dynamic adaptability of the EWHP system, resulting in impure hydrogen production and compromising the safety of the LH₂ cooling system, and reduce the fitness of the integrated system for wind electricity–hydrogen heat multi-field coupling. This paper provides a comprehensive overview of the fundamental structure and characteristics of this integrated technology and further identifies the key challenges in its application, including the dynamic adaptability of electrolytic water hydrogen production technology, as well as the need for large-capacity, long-duration storage solutions. Additionally, this paper explores the future technological direction of this integrated system, highlighting the need to overcome the limitations of electrical energy adaptation within the system, improve product purity, and achieve large-scale applications. Full article

A large amount of energy can accumulate and be stored during underground coal fires. As thermal energy cannot be easily removed using the traditional technologies of fire prevention and extinguishment, there is a potential benefit to collecting and utilizing thermal energy from coal fires and converting it to electrical energy. Thus, this work proposes a thermoelectric generator as a solution to convert thermal energy from coal fires to electrical energy. To improve the thermal energy conversion efficiency, an experimental test system was established using a thermosyphon, an electric heating module, a cooling circulation module, a thermoelectric module, and a data acquisition module. Under the condition of ensuring the same input heat and cooling boundary conditions, the influence of three factors, namely the cooling method, the connection method, and the coverage rate of thermoelectric devices, on the performance of the coal fire waste heat conversion system was studied. The results show that, compared with air cooling, water cooling provides a greater temperature difference for the thermoelectric module, and the maximum temperature difference can reach 65.90 °C. Series connection between thermoelectric devices will generate a higher open-circuit voltage and output voltage. The maximum horizontal open-circuit voltage value can reach 3.34 V, and the maximum output voltage is 2.61 V. Compared with the coverage rates of thermoelectric devices of 15.0% and 30.0%, the output power under the coverage rate of 22.5% is the largest at 0.35 W, and its thermoelectric conversion efficiency is also the largest at 0.35%. The optimal combination of thermoelectric modules obtained from the research results can provide ideas for the application of in situ coal fire prevention and control. Full article

Variable refrigerant flow (VRF) systems are common air-conditioning systems used in regions with moderate climates that have cooling and heating demands. Unlike typical air-source VRF systems, ground-source VRF systems require heat-source water circulation, and reducing the pumping power remains a significant problem. Herein, the intermittent pump control for circulating heat source water was achieved by installing a buffer water tank between the ground heat exchangers and VRF units. An intermittent control methodology was developed based on the indices of water transport efficiency and incorporated into a system simulation model with 72 boreholes, a cooling capacity of 252 kW, and a buffer water tank of 30 m³. Results indicated that intermittent control was achieved at heat load ratios lower than 40% as expected. This intermittent control allowed more efficient water transport with 38% lower pumping power than conventional inverter controls. Although the proposed system equipped more pumps and heat exchangers than conventional systems, it exhibited higher energy efficiencies for most measurement days than the conventional air-conditioning systems. The annual energy consumption was thus reduced by 34% and 8% compared to air-source VRF systems and conventional ground-source VRF systems, respectively. Full article

The external cooling water system of a 300 Mvar dual internal water cooling synchronous condenser at a certain ultra-high voltage converter station continued to exhibit significant scaling and corrosion, even with regular addition of scale and corrosion inhibitors. To solve this problem, the external cooling water of the synchronous condenser was sampled and tested periodically, with the main test items including conductivity, pH value, turbidity, hardness, alkalinity, and other water quality parameters directly related to corrosion and scaling. The trends of these parameters over time were also analyzed. The results showed that as the operation time increased, the cooling water became concentrated during multiple circulation cycles, and the various dissolved or suspended substances underwent a certain degree of enrichment. However, the addition of scale and corrosion inhibitors did not dynamically adjust according to the changes in water quality, and there was always an excessive dosage. Thus, using the external cooling water as the experimental sample, static scale inhibition tests and rotating coupon corrosion tests were conducted to evaluate the scale and corrosion inhibition performance of the commercial AS-582 scale and corrosion inhibitor used at this ultra-high voltage converter station under different conditions. Considering the more obvious corrosive tendency of this water sample, the focus was on testing its corrosion inhibition performance. When the dosage was 600 ppm, the scale inhibition effect was optimal, with an inhibition rate of 92.15%. The corrosion inhibition effect of this scale and the corrosion inhibitor were significantly related to water temperature. At 25 °C, when the dosage was 500 ppm, the corrosion inhibition effect was optimal, with an inhibition rate of 86.79%. However, when the temperature increased to 40 °C, the corrosion inhibition effect under each dosage was significantly worse, unable to meet the requirements, and the use of other corrosion inhibitors in combination was necessary. This work will provide a reference for the scientific use of scale and corrosion inhibitors. Full article

The study introduces an innovative three-stage nested power generation system that enables the cascading utilization of LNG cold energy. It makes the most of wasted energy by using ship jacket cooling water (JCW) and exhaust gas (EG) as heat sources, a trans-critical carbon dioxide cycle as internal circulation, and utilizing the pressure exergy of LNG. We choose two azeotrope mixing fluids that match the requirements and create four cases for the outer and middle cycle working fluids in the three-stage nested system. To discover the ideal system performance from the perspectives of exergy (E), economy (E), and environment (E), four cases were subjected to multi-objective optimization using the multi-objective particle swarm optimization technique (MOPSO). Finally, the optimal solution was found by applying the TOPSIS decision-making method. Through comparative analysis, the optimal system is selected among the four optimization results. R170 (22.66%) and R1150 (77.34%) are used as the outer circulating working medium, while R170 (90.86%) and R1270 (9.14%) are utilized as the inter-cycle working fluid. The net output work is 575.75 kW, the optimal exergy efficiency is 46.09%, the optimal electricity production cost is $0.04009 per kWh, the carbon dioxide emissions can be reduced by 36,910 tons, and the payback period is 2.548 years. After optimization, a more energy-efficient and environmentally friendly power generation system is obtained. Full article