Solar Air Source Heat Pump Research Articles

Ultra-low temperature heating system based on dual-source solar assisted heat pump using compound parabolic concentrator-capillary tube solar collector

The fifth-generation heating – ultra-low temperature heating benefits to reduce electricity consumption and achieve the net zero goal. The dual-source solar assisted heat pump based heating system has been demonstrated to be an attractive green heating technology for the domestic sector. However, the slower response speed of the low temperature heating to the variation of heating load in responding to the variations of weather conditions limits its thermal comfort performance. The enhancement in solar collector performance brings valuable improvements in response speed of the heating system. In the present work, a heating system based on solar assisted air source heat pump using a compound parabolic concentrator-capillary tube solar collector (CPC-CSC) is investigated with the set heating temperatures of 40, 45, 50, and 55 °C. This heating system works for both space heating and hot water under the weather conditions in London. The results suggest that using a concentrated solar collector improves the response speed of the heating system at low set heating temperatures. For such a heating system, the ultra-low heating temperature increases the application of renewable energy and passive heating (by 6.4%). Compared with the dual-source indirect expansion solar assisted heat pump using flat plate collector, the heating system using CPC-CSC can reduce TEWI by 4.6% with a slightly longer (1.9%) payback period. As the set heating temperature decreases from 55 to 40 °C, the seasonal and yearly system seasonal performance factors significantly increase by 17.1% and 20.5%, respectively.

A novel heating system of solar-assisted enhanced jet enthalpy air source heat pump for cold regions

Solar energy and air source heat pumps are common heat sources for clean heating, but at lower ambient temperatures, the performance of solar energy and air source heat pumps will decline significantly, which can be ameliorated by integrating the two heat sources. However, the range of solar radiation and ambient temperature variation is very wide, and the existing integration methods cannot guarantee that they are optimal over a wide range. Therefore, this paper proposes a novel integration method of solar energy and jet enthalpy air source heat pump suitable for cold regions, where solar energy is used to heat the refrigerant in the jet branch to increase the flow rate of the jet branch, which enhances the effect of jet enthalpy. Under varying outdoor temperatures and solar radiations, the performances of the new integrated system and the traditional integrated systems are compared by simulation method. The results show that within the scope of this study (outdoor temperatures ranging from −30 °C to 10 °C, and radiations from 200 to 800 W/m2), the heat output and coefficient of performance of the new system are higher than those of the existing integrated systems. At an outdoor temperature of −30 °C and a radiation of 500 W/m2, the new system increases heat output by 45.8 % and coefficient of performance by 22.5 % compared with the existing two systems. This research can promote the application of solar energy and air source heat pump heating in cold regions.

Simulation study on thermal performance of solar coupled air source heat pump system with phase change heat storage in cold regions

The development of efficient and clean heating technologies is profoundly significant for the reduction of carbon emissions in cold regions. This paper puts forth a novel solar-coupled air source heat pump system integrated with phase change heat storage technology, which is well-suited for regions with such climatic conditions. A numerical model of the components and coupled systems is established using the lumped parameter method, and an iterative method is employed for the computational solution in MATLAB software. A variety of system performance aspects are then simulated and analysed following the configuration of component structural parameters and initial operating conditions. The results of the simulations indicate that an increase in the phase change temperature interval of the phase change materials leads to a higher average heat release power. In particular, a 2 °C increase in the phase change temperature interval results in an increase in the heat release power of over 10 %. Furthermore, when the system is applied in typical cold regions, including Kunming, Hangzhou, Lhasa, and Harbin, the average coefficient of performance is 10.23, 8.87, 8.49, and 7.70, respectively. The proportion of solar energy input contributes to an increase in system efficiency across all regions. A case study of Hangzhou reveals that the incorporation of solar energy into the system results in an increase in efficiency of 70.91 %. This research provides valuable operational methods and site selection recommendations for engineering practices, laying a theoretical foundation for its widespread application in cold regions.

Experimental and simulation study on the performance of a solar assisted multi-source heat pump drying system in Zhengzhou area

Zhengzhou of Henan province is an important agricultural production base. To improve the performance of the combined drying system and promote the development of agricultural products in Zhengzhou area, a solar assisted multi-source heat pump (SMSHP) drying system was proposed based on a traditional solar assisted air source heat pump (SASHP) drying system. The simulation models were developed for the air source heat pump (ASHP), SASHP, and SMSHP drying system respectively. The coefficient of performance, energy consumption and specific moisture extraction rate of the drying systems under different seasons were analyzed. Moreover, to validate the simulation models, an experimental platform of the combined drying system was designed and set up, and the experimental tests were carried out on the ASHP, SASHP, and SMSHP drying system. The simulation results revealed that the SMSHP drying system had lower energy consumption, higher coefficient of performance and specific moisture extraction rate than that of the SASHP drying system. The most significant performance enhancement was observed in spring, where the SMSHP system demonstrated a 22.69 % increase in coefficient of performance, a 19.2 % increase in specific moisture extraction rate, and a 16.11 % decrease in energy consumption compared to the SASHP drying system. Comparing with the experimental data, the simulation model errors of the energy consumption, coefficient of performance, and specific moisture extraction rate of the SMSHP drying system were 3.19 %, 0.28 %, and 2.27 %, respectively. Therefore, the accuracy of the simulation results was confirmed. To better calculate the heat provided by the solar collection system, the concept of the tank heating guarantee rate was first introduced, and it was found to be more scientific than the solar energy guarantee rate. At last, The economic and environmental benefit of the drying systems were analyzed during the life cycle, and the SMSHP drying system exhibited better comprehensive performance than the SASHP drying system. This paper provides valuable insights into the comprehensive utilization of solar energy and the control logic of solar assisted air source heat pump combined drying system under different seasons.

Optimization of solar-air source heat pump hybrid heating system

Abstract In order to construct a versatile, complementary, low-carbon, clean, and efficient heating system, this study explores the potential of a solar-air source heat pump (SAHP) hybrid heating system. A simulation model is established in TRNSYS, and the particle swarm algorithm (PSO) and genetic algorithm (GA) from GENOPT and MATLAB are employed. With the aim of minimizing the annual cost, optimization is conducted on the key parameters and operational strategies of the system. Comparative analysis between the two algorithms reveals that PSO slightly outperforms in cost reduction, while GA exhibits a slight advantage in enhancing system performance. Significantly improved energy savings are achieved by appropriately reducing the rated heating capacity of the air source heat pump and increasing the volume of the water tank.

A novel heating strategy and its optimization of solar–air source heat pump heating system for rural buildings in northwest China

In the rural areas of Northwest China, the utilization of clean and renewable energy is deemed a crucial measure for reducing building energy consumption and environmental pollutant emissions. This paper focuses on constructing a simulation platform for a solar-assisted air source heat pump heating system. A rural residential building in Yongshou County, Shaanxi Province, serves as an illustrative example. A novel flexible temperature control method with a feedback controller in sub-area and period is proposed in this paper, alongside the selection of three distinct objective functions aimed at optimizing the heating system. The simulation results indicate an average temperature of 17.0 °C throughout the heating cycle, with a peak temperature of 18.7 °C. Moreover, the solar fraction is measured at 25.11%, underscoring the significance of collector area and heat storage tank volume as primary factors in system design. The results also demonstrate that across various optimization objectives, the life cycle cost optimization scheme yields greater economic benefits, while the target building unit heating cost optimization scheme boasts the shortest static payback period and lowest unit heating cost. Conversely, the solar fraction optimization scheme stands out for its superior environmental benefits. These findings offer valuable insights for the design of heating systems tailored to diverse objectives.

WITHDRAWN: A Numerical Study on Performance Optimization of Household Solar-air Source Heat Pump System in Hot Summer and Cold Winter Regions of China

Abstract: Since the authors are not responding to the editor’s requests to fulfill the editorial requirement, therefore, the article has been withdrawn from the journal Recent Patents on Mechanical Engineering. Bentham Science apologizes to the readers of the journal for any inconvenience this may have caused. The Bentham Editorial Policy on Article Withdrawal can be found at https://benthamscience.com/editorial-policies-main.php. BENTHAM SCIENCE DISCLAIMER: It is a condition of publication that manuscripts submitted to this journal have not been published and will not be simultaneously submitted or published elsewhere. Furthermore, any data, illustration, structure or table that has been published elsewhere must be reported, and copyright permission for reproduction must be obtained. Plagiarism is strictly forbidden, and by submitting the article for publication the authors agree that the publishers have the legal right to take appropriate action against the authors, if plagiarism or fabricated information is discovered. By submitting a manuscript the authors agree that the copyright of their article is transferred to the publishers if and when the article is accepted for publication.

Optimization of solar-air source heat pump heating system with phase change heat storage

The optimization of heating system has always been of much concern, among which the annual life cycle cost (ALCC) was widely used as an optimization method, while the non-guaranteed hours were often overlooked. This study proposed the elasticity-economy (E-E) objective function as an optimizing indicator, and demonstrated it taking a solar assisted heat pump heating system with phase change material (SC-ASHP-PCM) as an example. Firstly, the single variation impact was analyzed. After optimizing the thermal performance of sub-systems, the proportion of heat supplied by solar collector (SC) and phase change material (PCM) sub-systems increased by 5.4 % and 3.4 %, respectively. Subsequently, the Hooke-Jeeves algorithm was developed to optimize multi-factors, hence minimizing the E-E objective function. The optimal solution was achieved when the non-guaranteed rate was 5 % and the penalty factor was 150 CNY/h. Compared with the baseline situation, the system energy consumption (156.8 × 103 kW‧h) was reduced by 30 %, and the E-E objective function was reduced by 24 %. Furthermore, the minimum operating cost was 18.3 CNY/m2, saving up to 46 % compared to traditional heating systems. The method is generalized to obtain the optimal energy saving potential under different non-guaranteed hours, which provides guidance for the heating systems' design and operation.

Solar-Air Source Heat Pump Water Heater for Scorching Climatic Condition: Energy, Exergy, Economic and Enviroeconomic (4E) Exploration for Sustainable Future

As solar-powered air source heat pump is an emerging water heating technique in scorching climatic conditions, it is necessary to explore their performance in terms of energy, exergy, economic, and environeconomic (4E) perspective. Henceforth, current research experimentally investigates and reports on 4E of Direct Expansion Solar-Air Source Heat Pump water heater for hot regions. A heat pump with a dual source evaporator is proposed in two working modes: solar air source mode and air source mode. The impact of ambient conditions on the thermal performance, such as power consumption, evaporator and condenser capacity, heating time, coefficient of performance, and exergy efficiency of the heat pump water heating system in both the working modes, was experimentally investigated. Results depict the coefficient of performance of the proposed heat pump system in solar air source mode and air source mode in the range of 2.37-5.05 and 2.26-4.21, respectively. On average, the system heating time in solar air source mode is 16.5% shorter than in air source mode. Based on the simulation results, compared to a conventional standard electric heating system, the payback period and lifetime carbon-dioxide mitigation savings cost of the proposed dual-source heat pump system are about 616 days and $179866, respectively.

Simulation Study of a Novel Solar Air-Source Heat Pump Heating System Based on Phase-Change Heat Storage

A traditional solar air-source heat pump heating system cannot effectively utilize solar energy, and it consumes large amounts of energy when operating during cold nights. Accordingly, a conventional heating system has been improved by phase-change heating to form a new phase-change thermal storage solar air-source heat pump heating system. Based on the TRNSYS simulation platform, a heating simulation study of the improved phase-change heating system was carried out in Xi’an City. The results show that the addition of phase-change thermal storage technology allows the heating system to make better use of solar energy, and the efficiency of the solar collector is increased by 5.9%; the presence of the phase-change material effectively reduces the rate of temperature drop inside the water tank, making the water supply temperature more stable; during the whole heating period, the improved phase-change heating system saved 484.91 kWh of operating energy, showing a very good energy-saving effect.

Study on Heating Energy Efficiency and Optimization of Solar-air Source Heat Pump

This paper studies the heating energy efficiency and optimization of a solar-air source heat pump (SASHP). Through system simulation, the energy efficiency of the SASHP is compared with other heating methods. The results show that SASHP has higher energy efficiency. We also found that in the SASHP, the air source heat pump (ASHP) is involved in heating 46% of the time. Therefore, we suggest optimizing the energy consumption of the ASHP to improve the system’s energy efficiency. In addition, lowering the supply water temperature can also reduce the system’s heating energy consumption. When the supply water temperature is lowered from 60°C to 48°C, the COP is increased from 1.98 to 2.83, which is a 31% improvement. Our research provides theoretical support for the application of SASHP and provides new ideas for achieving green and low-carbon heating.

Performance analysis of a novel solar assisted air source heat pump

Solar assisted heat pumps (SAHPs) are energy-efficient and environmentally friendly heating systems that utilize solar energy in different configurations. In this study, the potential benefits of heating the evaporator inlet air using solar energy as a new method were investigated using a developed correlation. The study focused on a 4 kW air conditioner that achieved a COP value of 4.17 for heating with an indoor temperature of 20C and an outdoor temperature of 7C. The aim was to determine how the COP value, evaporator inlet air temperature, and total power consumption changed based on the amount of solar energy transferred when the system was supported using the mentioned method. It was observed that a solar support of 5000 W increased the COP value of the SAHP from 4.17 to 4.99.

Investigation on the thermal performance and economy of a solar assisted air source heat pump domestic hot water system

In order to increase the utilization of renewable energy and reduce carbon dioxide emissions, a solar assisted - air source heat pump (SA-ASHP) domestic hot water supply system is proposed, designed and built, the thermal performance and economy are numerically simulated and experimentally verified, the optimal design parameters are determined based on the economic optimization analysis. The results show that the coefficient of performance (COP) of air source heat pump (ASHP) varies from 2.62 to 3.93 and the COP of SA-ASHP system varies from 2.76 to 6.26. The solar fraction varies from 8.83% to 45.51%, and varies greatly in different seasons. The simulated heat collection of solar collector, the power consumption and heating capacity of ASHP, and the total power consumption of water pump are in good agreement with the measured results. Compared with the existing SA-ASHP system, the annual cost has decreased by 1998.32USD, annual cost converted from initial investment has decreased by 629.08USD, operating cost has decreased by 1369.25USD and total power consumption has decreased by 16897.79 kWh of the optimized SA-ASHP system. The optimum ratio between the input power of ASHP and the collector area is 0.078 kW/m2. The research results play an important role in guiding the design, operation and heat source selection of domestic hot water (DHW) system in student dormitory.

Optimal control study of solar-air source heat pump coupled heating system operation

With China’s ambitious goals of carbon capping by 2030 and carbon neutrality by 2060, the multi-energy coupled clean heating technology represented by solar-air source heat pumps is developing rapidly. In order to solve the above problems, this paper analyzes the characteristics of the multi-energy coupled heating system by establishing a virtual simulation model and optimizing the system operation and control modes. Technical support is provided for efficiently utilizing multi-energy coupled heating technology in rural buildings.In this paper, the mathematical model of the system is established by analyzing the form and working principle of the solar-air source heat pump coupled heating system. Initially, three operation strategies are constructed: priority utilization of solar energy strategy (Strategy I), air source heat pump fixed temperature switching strategy (Strategy II), and air source heat pump timed switching strategy (Strategy III), laying the foundation for operation strategy optimization.The dynamic load change pattern of the building in winter was calculated using TRNSYS software, based on which equipment selection was carried out, and a simulation model of the solar-air source heat pump coupled heating system was established. The system operation strategy was optimized. A temperature difference control strategy was used for the solar collector cycle control optimization, which increased the solar collector efficiency by 12% compared to the fixed temperature control strategy. Based on typical climate data, the heating season was divided into 10 phases according to a 15-day cycle, and three operation strategies were optimized and compared for each phase with the goal of comprehensive system energy efficiency. After comparison and analysis, strategy 1 and 3 have their advantages in different stages of the heating season. The operation strategies with higher system energy efficiency in each stage were combined in the heating season, called combined operation strategy (strategy 4), and compared with other strategies in the heating season. Compared with strategy 1 and strategy 3 in the whole heating season, the system energy efficiency of strategy 4 was improved by 3%-6%. This indicates that strategy 4 has better operation effect.

Optimization of a solar-air source heat pump system in the high-cold and high-altitude area of China

Making full use of renewable energy is one of the efficient tools to reduce energy consumption and CO2 emissions in buildings. This study investigated the performance of a solar-air source heat pump system for a building in the high-cold and high-altitude area of China. A simulation model was established and verified by the measurement results. The annual cost, unit heat cost and annual average solar energy guarantee rate cost were selected as the optimization objectives. The Hooke-Jeeves algorithm was used to optimize the collector area, collector angle, water tank volume, heat pump heating capacity, and heat pump start-stop temperature difference. The energy-saving, environmental and economic benefits were also studied. The results show that the schemes obtained with different optimization objectives were significantly improved compared to the existing design scheme, and the indoor thermal comfort was maintained. Considering the performance of the system and the situation in the high-cold and high-altitude area, the optimization scheme for the annual average solar energy guarantee rate cost was more suitable for the building.

Research and application of park multi-source synergistic and complementary heating system and its coordinated control method

The integration of solar thermal collectors (STC) and air source heat pump (ASHP) heating systems has been widely used for building heating. However, these systems have the problems that the STC cannot fully utilize the solar energy at weak radiation, and the ASHP has insufficient output as well as low coefficient of performance (COP) under extreme cold conditions. In this study, a multi-source synergistic and complementary heating system (MSSCHS) with a heating mode selection model based on belief rule base and evidential reasoning (BRB-ER) method is designed. First, the MSSCHS composed of the STC and the ASHP as the main heat sources, and the water source heat pump as the auxiliary heat source, along with its three heating modes under different operating conditions were proposed. Then, a system heating mode selection model based on the BRB-ER method was establish to achieve mode switching. Finally, the MSSCHS with BRB-ER heating mode selection model was tested experimentally. The results show that compared with the conventional ASHP + STC heating system, the solar energy utilization rate of the MSSCHS had increased by 19.3 %, 16.6 % and 8.2 % respectively in three typical days, and the ASHP's COP had increased by 37.7 %- 55.6 % under extreme cold conditions. The high efficiency and stability of the MSSCHS were verified through operational tests during the heating period. Furthermore, by applying in different types of buildings, it is verified that the MSSCHS can meet different heating requirements and has a good applicability. It was demonstrated that the proposed MSSCHS has more efficient heating mode and more accurate mode selection method, which can provide a new research idea for building heating.

Study on the performance of an ultra-low energy building in the Qinghai-Tibet Plateau of China

The ultra-low energy building is an effective solution to reduce building energy consumption and CO2 emission in high-cold and high-altitude areas of China. A new ultra-low energy building in the Qinghai-Tibet Plateau was built, and a solar-air source heat pump system was designed to cover the heating needs in winter. The performance of the ultra-low energy building was studied by measurement and simulation methods. The measured results show that the average room temperature is above 18 °C without heating, and the indoor temperature can meet the requirements of 20 °C with the heating system. The indoor VOC concentration can be maintained at a low level. The building's air tightness can meet the requirements of the ultra-low energy building. The heating system ran well, and the average COP was 2.6. The simulation results show that the natural room temperature is between 20 and 23 °C more than 90% of the time under heating conditions. The average COP of the heat pump is 3.6, and the solar energy guarantee rate is 44.8% throughout the heating season. The heating system can save 2490.5 kg of standard coal and 6724.3 kg of CO2 emission per year.

The Application of a Solar–Air-Source Heat Pump Dual-Supply Heating System in a High-Cold Area in China

Solar energy is the most available renewable resource and has great potential for various applications. Solar heat pumps are limited when operating alone due to weather and the unstable and intermittent nature of solar energy. The idea of combining a solar collector with an air-source heat pump (ASHP) is proposed to solve the problems. Taking solar energy and air energy as the heat source of the system can improve the heat collection efficiency and heating performance coefficient of the dual-supply heating system in realizing the efficient and stable operation of the whole unit. This study investigated the application of a solar–air-source heat pump (S/AS-HP) dual-supply heating system for a residential building in Lhasa and compared the winter work performance and economic benefits of three different heating forms: solar–air-source heat pump, air-source heat pump, and solar–electric auxiliary heating systems. A simulation model was established and analyzed using the measurement data. The results show that during the heating period, the temperature of the primary side water supply is stable at about 60 °C, and the total operating hours of the solar collector period accounted for 26.9% of the total hours, of which 23.16% were independent operating hours. The average COPsys of the solar–air-source heat pump is 4.21, which greatly improves work performance compared with other systems, and the annual cost is the lowest among the three forms for the same service life at 41,824.6 CNY, saving 9.6% and 35.1% per year compared with the air-source heat pump system and the solar–electric auxiliary heating system. Considering conditions in alpine regions, S/AS-HP systems are the optimal heating solution for single buildings.

Performance of solar-air source heat pump heating system aided by district heat supply network research

Abstract To improve the usage rate of district heat supply network and solve the frost problem in solar-air heat pumps, this study used TRNSYS to construct a new solar-air source heat pump heating composite system that uses waste heat from the district heat supply network. The impact of the waste heat recovery device on the heating performance of the new composite system was analysed, and the economic and environmental performance of the composite system was compared with other heating systems. During a typical day, the average coefficient of performance of air source heat pumps (COP) of the composite system increased by 13% and the power consumption of the system decreased by 35.9%. Throughout the heating season, the power consumption of the composite system was 13.59% higher than that of traditional systems, and system coefficient of performance (SCOP) was 15.89% lower than traditional systems. Based on economic analysis, the relative operating costs of the composite system, coal-fired boiler, gas-fired boiler, oil-fired boiler and combined heat and power (CHP) are 1, 1.19, 2.33, 5.56 and 0.85, respectively. The operating cost of the composite heat source system is only 17.43% higher than that of CHP and lower than the other three heating systems. Quantitative evaluations of the environmental friendliness of these systems were conducted using the fuzzy analysis mathematical method. The evaluation results were 9.62, 5.89, 15.05, 9.10 and 6.79, respectively. It was found that the composite system is second only to the gas-fired boiler in terms of environmental friendliness and is 38.9% higher than the coal-fired boiler and 29.5% higher than the CHP.

Modeling and Optimization of Solar Collector Design for the Improvement of Solar-Air Source Heat Pump Building Heating System

Modeling and Optimization of Solar Collector Design for the Improvement of Solar-Air Source Heat Pump Building Heating System