Coefficient Of Performance Research Articles

Comprehensive performance evaluation of steam generating heat pumps for industrial waste heat recovery

Steam generating heat pump (SGHP) is a key technology for industrial decarbonization. For comprehensive evaluation of the feasibility and reliability of SGHP in different industrial sector, the work develops a thorough evaluation model for assessing the performance of SGHP by considering waste heat recovery, CO2 trading value, and pollutant emission cost, in addition to the conventional evaluation criteria. This work presents a thorough comparison of the thermodynamic performance and sustainability of various types of SGHPs across different industrial sector. Additionally, the conflicting relationships between the coefficient of performance (COP) and exergy efficiency are balanced through the application of the technique for order preference by similarity to ideal solution (TOPSIS). The results show that all the indexes of SGHP connected to an open heat pump (SGHPO) with different application scenarios are higher than those of SGHP connected to a flash tank (SGHPF). At the most unfavorable operating condition of the system, the COP minimum value is 1.31 and the exergy efficiency minimum value is 20.42%. These results indicate that replacing the coal-fired boiler with SGHP is feasible and the work could provide theoretical guidance for optimal design and equipment manufacture.

Performance Predictions of Solar-Assisted Heat Pumps: Methodological Approach and Comparison Between Various Artificial Intelligence Methods

The coefficient of performance (COP) is a crucial metric for evaluating the efficiency of heat pump systems. Real-time monitoring of heat pump system performance necessitates continuously collecting and processing data from various components utilizing multiple sensors and controllers. This process is inherently complex and presents significant challenges. In recent years, artificial intelligence (AI) models have increasingly been applied in refrigeration, heat pump, and air conditioning systems due to their capability to identify and analyze complex patterns and data relationships, demonstrating higher accuracy and reduced computation time. In this study, multilayer perceptron (MLP), support vector machines (SVM), and random forest (RF) are used to develop COP prediction models for solar-assisted heat pumps. By comparing the predictive accuracy and modeling time of the three models built, the results demonstrate that the random forest model achieves the best prediction performance, with a mean absolute error (MAE) of 2.42% and a root mean squared error (RMSE) of 4.01% on the train set. On the test set, the MAE was 2.35% and the RMSE was 3.84%. The modeling time for the RF model was 6.57 s.

Thermal performance analysis of the novel medium-depth borehole heat exchanger (MDBHE) coupled photovoltaic photothermal (PV/T) heat pump domestic hot water supply system

ABSTRACT As global energy demand continues to rise and traditional energy sources increasingly fail to meet sustainability targets, conventional domestic hot water systems that rely exclusively on either geothermal or solar energy face inefficiencies and seasonal limitations. To tackle these issues, this study introduces an innovative domestic hot water supply system combining MDBHE with a PV/T heat pump and investigates its thermal performance. This system utilizes thermal energy to elevate the temperature of water extracted from the MDBHE, while supplying power through photovoltaic electricity. The results indicate that increasing the circulating water flow rate improves the heat extraction capacity of the MDBHE. However, this also leads to higher flow resistance and an increased power requirement for the circulating water pump. Additionally, at a circulating water flow rate of 32 m3/h, the system fails to extract heat from geothermal energy when the inlet temperature exceeds 34.5°C. Furthermore, with a PV/T module area of 2000 m2, solar radiation intensity of 600 W/m2, and MDBHE depth of 2000 m, the system can attain a maximum water supply temperature of 50.9°C, with solar energy contributing 63%. Moreover, the coefficient of performance (COP) of the system can reach 5.8, outperforming conventional systems.

Performances Study of Eco-friendly Binary Azeotropic Mixtures Used as Working Fluid in Three Refrigeration Cycles

According to the European (F-gas) regulation, all refrigerants with a global warming potential (GWP) above 150 will be out by 2030. Searching for alternative refrigerants that are environmentally friendly has become an urgent challenge for the refrigeration and air-conditioning sector. Based on their environmental advantages and good thermo-physical properties, azeotropic mixtures have recently gained special interest as substitutes for conventional refrigerants. This study aims to compare the performance of three eco-friendly azeotropic mixtures with the common refrigerant R134a in three refrigeration cycles: the basic cycle (BC), the ejector-expansion refrigeration cycle, and the ejector sub-cooled cycle. The mixtures under study are R1234ze+R600a, R1234yf+R600a, and R1234yf+R290. These mixtures have global warming potential (GWP) of 5.668, 3.8688, and 3.2865 respectively, whereas R134a has a GWP of 1430. To reach this objective a numerical program was developed using MATLAB software to evaluate the coefficient of performance (COP), and the cooling capacity of the three refrigeration cycles using the studied eco-friendly mixtures and were compared with those of the commonly used R134a refrigerant. The entrainment ratio was also compared for the two ejector cycles using these refrigerants. The simulation was realized for condensing temperatures (Tc) selected between 30 and 55°C and evaporation temperatures (Te) ranging between -10 and 10°C. The results have shown that the eco-friendly azeotropic mixture R1234yf+R290 (GWP=3.51) has the best performances compared to the two other mixtures and they are close to those of R134a. On the other hand, the ejector expansion refrigeration cycle has exhibited a high coefficient of performance compared to the basic cycle and ejector sub-cooled cycle, and a high entrainment ratio compared to the ejector sub-cooled cycle for all used refrigerants. However, the ejector sub-cooled cycle gave a better cooling capacity than the other cycles. According to the obtained results, the azeotropic mixture R1234yf+R290 apart from its excellent environmental properties yields better performances in most of cases, this confirms that it could be a suitable substitute for conventional working fluid R134a which has a great global warming potential.

Implementation of thermoelectric wall systems for sustainable indoor environment regulation in buildings through numerical and experimental performance analysis

With buildings representing a substantial portion of global energy consumption, exploring alternatives to traditional fossil fuel-based heating and cooling systems is critical. Thermoelectricity offers a promising solution by converting temperature differentials into electrical voltage or vice versa, enabling efficient indoor thermal regulation. This paper presents a comprehensive investigation into the integration of thermoelectric wall systems for sustainable building climate control through numerical simulations and experimental analyses. Numerical simulations using computational fluid dynamics (CFD) techniques were conducted to model fluid flow and heat transfer within the thermoelectric wall systems under various operating conditions. These simulations provided insights into the system’s thermal behavior, which were validated through experimental setups designed to measure temperature differentials, airflow rates, and power consumption. The results showed that power consumption is directly correlated with electrical current, ranging from 0.19 W to 77.4 W as the current increased from 0.1 A to 2 A. Additionally, the heat absorbed by the system increased significantly with electrical current, by 706–1044%, depending on the air velocity. The thermal energy released from the hot side of the thermoelectric modules also rose substantially, ranging from 9850 to 5285% with increasing electrical current, and from 275 to 51% with higher air velocities. Moreover, increasing air velocity led to a 6.78–9.37% reduction in power consumption for currents between 0.1 A and 2 A. The coefficient of performance (COP) analysis revealed that optimizing both electrical current and air velocity is essential for maximizing system efficiency. While fan power consumption reduces COP at higher air velocities, neglecting fan power consumption results in COP improvements ranging from 6.5 × 10⁻⁴ to 49.0%. These findings highlight the potential of thermoelectric wall systems to enhance indoor comfort and energy efficiency in buildings.

Performance analysis of a novel dual exhaust mixed refrigerant heat pump with large temperature lift

The substantial demand for heat energy, ranging from 70 − 100°C in industrial and commercial sectors, presents a significant challenge when utilizing traditional air source heat pumps. The conventional single-stage air source heat pumps often struggle with low system efficiency and poor operating conditions when tasked with heating with large temperature lift. To address these issues, a novel dual exhaust mixed refrigerant heat pump cycle was proposed. By incorporating an intermediate pressure compression stage in parallel, the proposed system can achieve an optimal temperature match in the recuperator, and lead to a significant enhancement in the coefficient of performance (COP). Compared to a single stage mixed refrigerant heat pump cycle, the novel system improves the COP from 5.063 to 5.756, representing an increase of 13.68 %. Concurrently, the exergy loss proportion of the recuperator decreases from 18.8 % to 13.7 %. The proposed system consistently demonstrates superior COP and exergy efficiency regardless of whether the ambient temperature is within the range of 0 °C to 20 °C or the outlet water temperatures between 80 °C to 100 °C are present. These findings provide theoretical guidance for enhancing the performance of high-temperature heat pumps with large temperature lift.

Thermal-Hydraulic Characteristics of an Earth Air Heat Exchanger: An experimental analysis

The pipe layout design has a great effect on the thermal-hydraulic characteristics of earth air heat exchanger (EAHE) systems. So, in the current study proposed four new buried pipe design configurations; low to high to low, high to low to high, spiral, and circular, in addition to the straight or uniform for comparison. These five configurations are tested and analyzed experimentally depending on the thermo-hydraulic performance for summer cooling requirements with variation of Re in the range of 18041 – 40843. The results show that changing the uniform design of the EAHE with fixed pipe length enhances both the heat transfer process and pressure loss values. At the same operating conditions, the circular design has the best performance compared to the other ones. For all pipe shapes, the cooling effect increases with the increase of air Re. The thermal- hydraulic performance of the circular design pipe is higher than that of the other pipe designs. The highest coefficient of performance (COP) average values that can be obtained at Re = 18041 is 3.05 for circular shape and enhances by 48.08 % compared to uniform shape. The effectiveness of EAHE with circular shape is improved by about 3.52 % compared to uniform shape at Re = 18041. Spiral design is optimum design based on the Nu value which reaches about 48 with enhancement 12.56% and 0.34 % compared to uniform and circular shapes respectively, at Re = 40843. The hydrothermal performance factor is highest in the case of circular shape with value about 21.9 at Re = 21257. By increasing Re, the drawbacks of the increasing in the total entropy generation are reflected negatively on the exergy efficiency. The specific cost of the circular shape at Re = 40843 is the optimum value by about 0.7 $/W. Spiral and circular shapes have a decrease of CO2 emissions less than uniform shape by percentage varied from 2.93 % to 13.84% for decrease in the Re from 21257 to 40843. It is concluded that using EAHE with four new shapes is highly efficient in increasing cooling capacity and energy consumption in buildings.

Experimental assessment of using phase change materials in vapor compression refrigeration systems for condenser pre-cooling

The primary objective of this investigation is to empirically assess a new vapor compression cycle while employing phase change material (PCM) energy storage. During off-peak periods, the PCM undergoes charging, and during on-peak hours, it is discharged to cool the refrigerant entering the condenser, thereby enhancing the condenser's overall performance. In contrast to previous studies that exclusively examined the charging or discharging processes of air conditioning (AC) units, this research delves into the entire 24-h charge and discharge cycle. The proposed system is subjected to testing under identical conditions, both without PCM (conventional mode) and with a PCM storage tank, throughout a 24-h period. The PCM storage tank, which utilizes water as its phase change medium, possesses a volume of approximately 300 L and starts at an initial temperature of 25 °C. The outcomes of the study demonstrate notable improvements when incorporating the PCM storage tank. Specifically, the daily coefficient of performance (COP) increases by approximately 7 %, rising from 2.17 to 2.33. Additionally, it leads to a reduction in both the daily available cooling load and daily compressor energy consumption, with decreases of approximately 3.7 % (from 58.4 to 56.2 kWh) and 10.3 % (from 26.9 to 24.1 kWh), respectively.

Sustainable commercially-scaled greenhouse building cooling solution: Integrating PCM storage, desiccant wheels, and absorption chillers powered by dual-source solar/biomass energy

This research aims to address the critical need for sustainable cooling systems in greenhouses, particularly relevant in mitigating global warming impacts and enhancing food security worldwide. The urgency becomes more pronounced in locations experiencing high ambient temperature and humidity. The study introduces an innovative cooling system integrating Phase Change Material, a desiccant wheel, and an absorption chiller, powered by solar and biomass energy. This novel system aims to efficiently regulate temperature and humidity in greenhouse environments. The performance of this system is examined in Abu Dhabi, Doha, and Riyadh during the summer months, utilizing TRNSYS software for a medium-scale greenhouse model. Additionally, a comprehensive Life Cycle Assessment is carried out to quantify the environmental impacts of the proposed system. Results indicate that in Abu Dhabi, the system yields a Coefficient of Performance (COP) of 1.108, effectively maintaining indoor climate conditions. Similarly, Doha and Riyadh exhibit COPs of 1.015 and 0.827, respectively. In terms of solar energy utilization, Abu Dhabi demonstrates a solar fraction of 40.4, corresponding to the lowest Global Warming Potential (GWP) at 0.106 kg CO2eq per 1 kW of provided cooling capacity. Conversely, Riyadh records the highest GWP at 0.149 kg CO2eq, followed by Doha at 0.118 kg CO2eq. The Energy Payback Time (EPBT) for the system in Abu Dhabi is calculated to be 3.96 years, the shortest among the examined cities. In comparison, Doha and Riyadh present longer EPBTs of 4.48 and 5.83 years, respectively. These findings suggest that the proposed system offers a viable and environmentally friendly alternative to conventional greenhouse cooling approaches.

Design and performance analysis of portable solar powered cooler for vaccine storage

AbstractThe efficacy of vaccine storage is significantly impacted by temperature fluctuations within the cooler, often exacerbated by using phase change materials in existing cooler designs for remote areas. These materials can undergo uneven melting and phase separation, leading to temperature instability and vaccine potency loss. In response to this challenge, the present study introduces a novel design of a portable, locally‐made solar‐powered cooler optimized for longer storage periods. The cooler's performance in terms of temperature distribution, airflow dynamics, and the coefficient of performance (COP) is meticulously examined through computational fluid dynamics (CFD) simulations. The simulated results were validated using experimental data from the open literature, ensuring accuracy and reliability. The findings indicate that the developed cooler achieves significant improvements over traditional models. For instance, the current model reaches a temperature of +12°C in just 84 min, compared to 208 min, as reported in the literature results. Moreover, the current model reaches a temperature of −12°C in 195 min and it has energy efficient with a COP of 4.5. Statistical analysis further confirms the reliability of the simulation results, with root mean square and mean absolute percentage errors of 6.587 and 24.2%, respectively. Additionally, a comparative study of five insulative materials highlights polyurethane (Po) as the top performer, with a heat transfer performance of 14.3%, followed by feather fiber (Fe) (18.7%), fly ash (Fl) (19.8%), fiberglass (Fi) (21.9%), and coconut fiber (Co) (25.9%). Notably, net present value (NPV) of $689.336 and $448.01 was obtained for economic analysis of the current model over the existing model, showing the feasibility of the study. Hence, the cooler's effectiveness in storing vaccines in isolated regions exceeds that of conventional models, providing a hopeful solution to tackle vital challenges in vaccine distribution and preservation.

Evaluation of the Interconnection of a Biomethane Microturbine in an Absorption Refrigeration System

This article evaluates the performance and environmental impact of a combined system of natural gas microturbine and absorption refrigeration system. The objective of the study is to evaluate the interconnection of a biomethane microturbine in an absorption refrigeration system. The study applies energy and exergy balances to each component of the system, using EES software for the simulation. The microturbine is a Capstone C600s model with a nominal power of 600 kW, and the absorption chiller is a single-stage LiBr-H2O system with a cooling capacity of 680.7 kW. The results show that the microturbine achieves a thermal efficiency of 34%, an exergetic efficiency of 86%, and a net power output of 585.4 kW. At the same time the absorption chiller has a coefficient of performance (COP) of 0.7 and 680.7 kW with generator water temperature inlet of 100 °C. On the other hand, this study identifies the most efficient points of interconnection between the two systems. The combined system reduces the CO2 equivalent emissions by 700 to 900 tons/year compared to conventional systems. The behaviour of the interconnection heat exchanger is also evaluated using Computed Fluid Dynamics. The investigation concludes that the interconnection of a natural gas microturbine and an absorption refrigeration system is a promising alternative that can optimize both technical and economic aspects of energy generation and utilization, while mitigating environmental problems.

Multi-Objective Optimization of a Small-Scale ORC-VCC System Using Low-GWP Refrigerants

The increasing global demand for energy-efficient cooling systems, combined with the need to reduce greenhouse gas emissions, has led to growing interest in using low-GWP (global warming potential) refrigerants. This study conducts a multi-objective optimization of a small-scale organic Rankine cycle–vapor compression cycle (ORC-VCC) system, utilizing refrigerants R1233zd, R1244yd, and R1336mzz, both individually and in combination within ORC and VCC systems. The optimization was performed for nine distinct cases, with the goals of maximizing the coefficient of performance (COP), maximizing cooling power, and minimizing the pressure ratio in the compressor to enhance efficiency, cooling capacity, and mechanical reliability. The optimization employed the Non-dominated Sorting Genetic Algorithm III (NSGA-III), a robust multi-objective optimization technique that is well-suited for exploring complex, non-linear solution spaces. This approach effectively navigated trade-offs between competing objectives and identified optimal system configurations. Using this multi-objective approach, the system achieved a COP of 0.57, a pressure ratio around 3, and a cooling capacity exceeding 33 kW under the specified boundary conditions, leading to improved mechanical reliability, system simplicity, and longevity. Additionally, the system was optimized for operation with a cooling water temperature of 25 °C, reflecting realistic conditions for contemporary cooling applications.

Optimizing a thermoelectric window frame for heating and cooling: A cross-validated simulation study

AbstractBeyond the design of the system components, the potential application of thermoelectric (TE) systems is influenced by various factors in the control process. To understand the effects of these control factors on TE system performance in buildings, computational models for a TE window frame are established. In this work, two different numerical methodologies are applied to calculate the desired operating current and temperature distributions within the airflows and on the surfaces of the Peltier cells. The simulation results obtained from these methodologies are cross-validated and compared with relevant experimental results from existing studies. The mathematical model iterates the outgoing airflow temperature at non-object sides after determining the object-side temperature under a certain heat load. Additionally, alongside the number of activated Peltier cells and airflow rate, a new factor, termed the distribution of power strength, is considered in the analysis. The results indicate that homogeneous power strength across each Peltier cell yields favorable outcomes in both heating and cooling modes. The coefficient of performance (COP) increases with the activation of more Peltier cells under a constant heat load, while begins to decline beyond a certain threshold. Moreover, the COP is enhanced with a relatively higher airflow rate by strengthening the heat transfer to relieve the temperature difference between both sides. Consequently, based on the result analysis, we propose an optimization strategy for TE systems. This strategy aims to optimize operating currents, the number of working Peltier cells, and operating airflow rates, particularly when working conditions fluctuate.

ANALYSIS OF THE PERFORMANCE OF A COOLING SYSTEM (REFRIGERATOR) OPERATING WITH A THERMOELECTRIC COOLING SYSTEM USED TO PRESERVE CROPS AND AGRICULTURAL PRODUCTS

This experiment was conducted to assemble and test a cooling system operating with a thermoelectric cooling system (TEC) used to preserve crops and agricultural products from April 14 to June 24, 2021 AD. The study included a test of adding Heat Sink to the cold side of the thermoelectric cooling plates (TEC) with two levels (without heat sink (A1) and with heat sink (A2)) inside the system. 6 cooling models (TEC) were used with 6 heat sinks distributed in the form of two groups, and each group includes three cooling model (TEC). The following characteristics were measured (internal temperature (Tin), temperature difference (∆T), relative humidity (RH), time required to cool (t), cooling capacity (Qc) and Coefficient of Performance (COP). The results reveated that the presence of Heat Sink (A2) was superior than without (A1) in the following characteristics: It gave the lowest temperature inside the system 6.55Cº by 35% over treatment (A1), and pointed the highest (∆T, RH, t, Qc and COP) by (24.19 Cº, 82.32% , 43.73W and 19.87%) respectively. All these obtained results give with a cooling time 4.6h which was higes about 14% than (A1). Where the electrical capacity used 220W.

Performance analysis of solar-assisted ground source heat pump in severe cold regions

ABSTRACT Long-term operation of a ground source heat pump (GSHP) in severe cold regions leads to a gradual decrease in subsurface soil temperature, affecting system performance. This paper proposes a solar assisted ground source heat pump (SAGSHP) system consisting of solar photovoltaic thermal (PV/T) and GSHP. Through TRNSYS software, the system was analyzed for 10 years of dynamic simulation in a severe cold region. The results are listed below: (1) The SAGSHP system is capable of effectively lessening the maximal temperature of photovoltaic (PV) modules in Changchun, Shenyang, and Harbin, China, by 21.73%, 13.67%, and 19.10%, respectively. The power generation efficiency of PV modules in these three locations can be maintained at about 22% year-round. (2) After ten years of operation, the coefficients of performance (COP) of the heat pumps have increased by 5.70%, 6.80%, and 5.01%, respectively, relative to the first year, showing good stability. (3) The soil temperatures at all three locations were stabilized during the ten years of operation. This study provides a theoretical basis for devising and installing SAGSHP in severe cold regions.

Heat transfer of mid-deep ground source heat pump for crude oil gathering and transportation

Wax precipitation in crude oil gathering and transportation (COG&T) causes substantial decrease in oil flowability and thus blockages of pipelines, presenting high safety risks and dramatic economic loss. Conventional oil/gas blending and low-temperature transport are inefficient and energy-intensive. Geothermal energy released from abandoned oil wells may be used as renewable heat source, but remains unexplored. This study focused on feasibility of utilizing geothermal energy from abandoned oil wells by mid-deep ground source heat pump (MD-GSHP), so as to alleviate wax precipitation for short-distance COG&T. Numerical models of ground heat exchanger (GHE) were established by using finite difference method (FDM) based on validation of engineered examples. The results demonstrated that, to enhance geothermal extraction, it was essential to increase fluid flow rate, lower inlet temperature, use materials with high thermal resistance, and optimize the pipe dimensions. Additionally, the impacts of operational parameters of GHE and COG&T subsystems on MD-GSHP system performances were also analyzed. Increasing inlet temperature by 8 °C resulted in 39.5 % reduction in system load and 89.4 % increase in coefficient of performance (COP). This study provides a proof-in-concept demonstration for extracting geothermal energy from abandoned wells by MD-GSHP to mitigate wax precipitation in COG&T project.

Performance study of solar air collector-air source heat pump system inside the greenhouse

During the process of heating greenhouses, the phenomenon of inadequate heating installations is widespread. To address this issue, this paper proposed a solar air collector-air source heat pump (SAC-ASHP) system for greenhouses, combining solar technology with heat pump (HP) technology to provide sufficient heat during continuous cloudy days and winter. The heating capacities of the system on sunny, cloudy, and overcast days were 100.2 kWh, 112.3 kWh, and 157.8 kWh, respectively. The corresponding power was 30.1 kWh, 36.1 kWh, and 53.6 kWh. The coefficient of performance (COP) of the single air source heat pump (ASHP) for these days was 3.4, 3.2, and 3.0, respectively, while the COP of the solar heat pump (SHP) was 4.0, 3.5, and 3.1. Additionally, greenhouse employed heat and moisture recovery for humid air, aiming to provide a suitable environment for plant growth around the clock while conserving energy. The heat collection in the heat and moisture recovery combined HP mode was 66.7 % higher than in the heat exchanger (HE)-fan mode. This experimental study investigated the operational performance of the system in dynamic environments, revealing the stability of the system for greenhouse heating in cold regions, and providing new research ideas for greenhouse heating.

Experimental comparison of cycle modifications and ejector control methods using variable geometry and CO2 pump in a multi-evaporator transcritical CO2 refrigeration system

To reduce the direct global warming impact of refrigerants in HVAC&R applications, low-global warming potential (GWP) refrigerants, including natural refrigerants, have been extensively investigated as alternatives to hydrofluorocarbon (HFC) refrigerants. Among the natural refrigerants, Carbon Dioxide (CO2) offers several advantages, such as excellent transport and thermo-physical properties, being neither toxic nor flammable, and having a low price and high availability around the world. However, the high critical pressure and low critical temperature of CO2 often lead to transcritical operation, resulting in lower efficiency due to the additional compressor power necessary to achieve transcritical operation relative to subcritical HFC cycles. Therefore, a number of cycle modifications are used to enhance the coefficient of performance (COP) of transcritical CO2 cycles to meet or surpass those of HFC cycles. This paper provides a systematic experimental investigation of four such cycle architectures by employing the same multi-stage, two-evaporator CO2 refrigeration cycle test stand, 3 of these configurations in transcritical and 1 in subcritical conditions. The four cycles architectures included intercooling, open economization, an internal heat exchanger and two different ejector control approaches. Specifically, a variable-diameter motive nozzle and a variable-speed liquid CO2 pump located directly upstream of the ejector motive nozzle inlet were analyzed. Based on the experimental data, the maximum COP improvements are 4.64 % and 9.47 % when the ejector and the internal heat exchanger are used, respectively. The CO2 pump, once successfully stabilized, can control the ejector, increase its efficiency by up to 15 % and increase the cooling capacity to a maximum of 6.2 %. Nevertheless, a reduction in COP is measured when the pump is in use; however, unlike the other three different configurations, it was only analyzed under subcritical conditions.

Thermodynamic and economic analysis of a novel solid oxide fuel cell, two level thermoelectric generator and double effect parallel absorption chiller integrated system

This study presents a comprehensive thermodynamic and economic analysis of a novel hybrid energy system integrating a Solid Oxide Fuel Cell (SOFC) with a Two-Level Thermoelectric Generator (TTEG) and a Double-Effect Parallel Absorption Chiller (DEPAC) for enhanced waste heat recovery. The primary objective is to maximize energy utilization and overall efficiency by leveraging the synergetic effects of these components. Unlike previous studies, this research uniquely evaluates the effectiveness of the integrated system and examines the impact of different Absorption Chiller configurations and the number of TTEG elements, filling a critical gap in the literature. The proposed system achieves a net electrical efficiency of 42.88 %, an energy efficiency of 44.61 %, and an exergy efficiency of 57.16 % under optimal conditions. This marks a significant improvement compared to standalone SOFC systems, with the TTEG effectively harnessing waste heat and contributing an additional 0.680 kW/m2 to the overall power output. The integration of the DEPAC system further enhances performance by providing cooling with a Coefficient of Performance (COP) of 1.351. The economic analysis reveals a positive Net Present Value (NPV) of $1,993,136, a Dynamic Payback Period (DPP) of 6.7 years, and a Levelized Cost of Electricity (LCOE) of $59/MWh, underscoring the system's financial viability. These findings demonstrate that the hybrid system offers a sustainable and efficient solution for power generation and waste heat recovery, aligning with the broader goals of advancing renewable energy technologies and setting a new benchmark in hybrid energy system design and optimization.

An evaluation and innovative coupling of seawater heat pumps in district heating networks

Seawater heat pumps present promising solutions for the decarbonization of the heating sector by utilising seawater as a renewable heat source. This study explores their integration into district heating networks in cold climate regions, focusing on case studies in Estonia, and Norway. A main challenge lies in the freezing threat of seawater during winter, prompting investigations into innovative solutions. This research evaluates two proposed strategies: coupling seawater heat pumps with an additional heat source and locating them far off the shore where water temperatures are more stable. The study employs a multifaceted approach, considering technical, economic, and environmental factors. The research assesses and models seawater heat pumps in two case studies, exploring 10 MW heat supply scenarios. Performance indicators include Coefficient of Performance (COP), Electricity consumption, CO2 emissions, and Levelized Cost of Heat (LCOH). Results highlight the feasibility and advantages of coupling free heat sources with seawater heat pumps in district heating networks. In the Norwegian case, coupling waste heat and seawater heat pumps significantly reduces electricity consumption, CO2 emissions, and LCOH by 88 %, 65 %, and 76 %, respectively. In Tallinn, where seawater freezing is a concern, installing far-off the shore seawater heat pumps maintain year-round operation with a seasonal COP of 3.5 and a 34 % reduction in CO2 emissions compared to electric boiler coupling. Economic assessments suggest the feasibility of integrating far-off the shore seawater heat pumps in low-power price scenarios.