Search Results (21)

This paper proposes a novel solar-assisted inter-cooling air source heat pump (SCAS–HP) system that integrates a solar collector/evaporator into the intermediate injection branch to utilize solar energy for increasing the refrigerant flow rate at intermediate pressure. A numerical model of the system was developed and validated against the literature data, and then employed to investigate performance under varying operating conditions. Three configurations were examined—two-stage throttling (T–SCAS–HP), single-stage throttling (S–SCAS–HP), and parallel evaporators (P–SCAS–HP)—and their performance was compared with a conventional vapor injection air source heat pump (VI–ASHP) across solar radiation intensities of 10–1000 W/m², outdoor air temperatures of −20 °C to 10 °C, and outlet water temperatures of 35 °C and 55 °C. Hourly performance, economics, and CO₂ reduction were further assessed for Lhasa, Beijing, and Harbin. The results show that the COP_h improvement of SCAS–HP over VI–ASHP rises with increasing solar radiation intensity. Furthermore, the solar radiation threshold at which the COP_h of SCAS–HP begins to exceed that of VI–ASHP lies within the range of 100–200 W/m². Moreover, the COP_h increase rate of SCAS–HP rises with larger solar collector area and higher outdoor air temperature, but declines as the outlet water temperature rises. Among the three configurations, T–SCAS–HP outperformed S–SCAS–HP and P–SCAS–HP by 0.37 and 0.42 in COP_h at outlet water temperatures of 35 °C and 55 °C, respectively. In typical-day simulations, the COP_h showed a relative increase of 50.9% compared to that of the VI-ASHP system, corresponding to an absolute rise from 3.73 to 5.62 with a 130 m² collector at 35 °C outlet water temperature. The energy saving rate ranked highest in Lhasa, followed by Beijing and Harbin. The shortest payback period (5.6 years) was achieved in Harbin with a 130 m² collector area at the outlet water temperature of 55 °C. The proposed system is particularly suitable for large heating demand and long heating seasons in cold climates with abundant solar resources. Full article

The solar-assisted air source heat pump (SAHP) is a key technology of low carbon heating. However, the SAHP is still inefficient and unstable at low temperatures. Cascaded latent heat storage (CLHS) can store multi-stage thermal energy, which provides the possibility for the multiple utilization of solar energy. Hence, this paper proposed the SAHP integrated with CLHS for building heating. The high-temperature and medium-temperature latent heat storage (LHS) units are used for direct heating, and the low-temperature LHS unit preheats the air for the air source heat pump (ASHP). The thermal performance of the CLHS device is evaluated through combined numerical simulations and experimental tests. Results show that the average heat storage rate of the cascaded system is 61.1% higher than that of a conventional single-stage LHS unit. The heat storage uniformity of CLHS gradually improves with increasing inlet flow rate, but shows a trend of first increasing and then decreasing with the increase in fluid inlet temperature. Among the three tested levels, 80 °C was found to be the most uniform heat storage of the CLHS device. The performance of the system was further analyzed using TRNSYS to assess seasonal building heating performance. The overall efficiencies of the high/middle/low temperature LHS units are 93.6%, 81.6% and 94.3%, respectively. And the solar heat supply accounts for 70.8% of the total heat supply of the system. Compared with the non-preheating system where the low-temperature LHS unit is removed, the COP of the graded heating system is increased by 18.3%, and the energy consumption is reduced by 16.6%. Further parametric optimization based on the Hooke–Jeeves method reduces total system energy consumption by 20.7% and associated pollutant emissions by 20.6% compared with the pre-optimization system. The findings provide practical insights into the application of CLHS in solar-assisted heat pump systems for building heating. Full article

This study analyzes the feasibility of increasing the energy and economic efficiency of a residential heating and domestic hot water (DHW) preparation system with a solar-assisted air-to-water heat pump (AWHP), implemented in southeast Romania. The following options are evaluated from the sustainability point of view (energy, economic and CO₂ emissions): renovation of the building and modernization of the system by integrating an electric accumulator, increasing the capacity of photovoltaic panels (PV) and solar thermal collectors (STCs), and the option of replacing the AWHP with a ground-source heat pump (GSHP) with a vertical loop (GSHP-VL) and a GSHP with a horizontal loop (GSHP-HL). The energy performance of heating systems was simulated using GeoT*SOL software. The results show that by renovating a home, the energy requirement for heating decreased by about 58%; therefore, following the current financial rules applied to prosumers, the GSHP-VL system has the best energy performance (electricity consumption and solar coverage rate of this consumption), economic performance (investment recovery period and annual operating cost) and environmental performance (lowest CO₂ emissions) and that through a government program that promotes energy efficiency and the use of renewable energy sources in homes, capital costs can be reduced by (43–57)% in the case of systems with HP, PV and electric storage. This study shows that a 5 kW PV system combined with 5 kWh battery cannot cover the full heat demand of a medium-to-large house during the winter, and for full energy independence, a larger PV array paired with a higher-capacity battery is necessary. Generous government subsidies amounting to 50% can reduce the payback period for such investments from (11.26–14.68) years to (5.86–7.26) years. Full article

Photovoltaic thermal systems are capable of simultaneously generating electricity and recovering thermal energy from the rear surface of photovoltaic modules. When integrated with an air-source heat pump, the thermal energy recovered from an air-based photovoltaic thermal system can be utilized as an auxiliary heat source, thereby improving heating performance and reducing electricity consumption. In this study, a demonstration-scale performance assessment of an air-based photovoltaic thermal-assisted air-source heat pump system was conducted in a real building located in Asan, South Korea. Performance analysis was based on measured operational data collected over a one-month period in March 2024, corresponding to late-winter to early-spring conditions when heating demand was still present. During the measurement period, the average plane-of-array solar irradiance was approximately 600 W/m², with peak values reaching up to 1000 W/m². Under these conditions, the air-based photovoltaic thermal collector provided average electrical and thermal power outputs of 1.96 kW and 2.2 kW, respectively, while peak outputs reached 3.3 kW for electricity generation and 3.8 kW for thermal energy recovery. The daily thermal energy production remained relatively stable, ranging from 17.8 to 21.7 kWh. Furthermore, approximately 45–60% of the recovered thermal energy was effectively transferred to a buffer tank through an air-to-water heat exchanger, indicating stable solar heat recovery and storage performance. When the recovered thermal energy was supplied to the air-source heat pump during daytime heating operation, a preheating effect was observed, resulting in reduced electricity consumption and improved heating performance. The coefficient of performance increased from 2.24 during nighttime operation to 2.81 under solar-assisted daytime conditions, corresponding to a notable reduction in electricity consumption under solar-assisted daytime operation, compared with nighttime operation without PVT preheating. Overall, the results indicate that, under the tested late-winter to early-spring heating conditions, the integrated air-based photovoltaic thermal and air-source heat pump system can enhance heating performance and reduce electricity consumption, demonstrating its practical feasibility as a solar-assisted heating solution rather than representing generalized annual performance. Full article

This study offers a detailed environmental, energy, and economic evaluation of thermal modernisation options for an existing single-family home in southern Poland. A total of 24 variants, combining different heat sources (solid fuel, biomass, natural gas, and heat pumps) with various levels of building insulation, were analysed using energy performance certification methods. Results show that, from an energy perspective, the most advantageous scenarios are those utilising brine-to-water or air-to-water heat pumps supported by photovoltaic systems, reaching final energy demands as low as 43.5 kWh/m²year and primary energy demands of 41.1 kWh/m²year. Biomass boilers coupled with solar collectors delivered the highest renewable energy share (up to 99.2%); however, they resulted in less notable reductions in primary energy. Environmentally, all heat pump options removed local particulate emissions, with CO₂ reductions of up to 87.5% compared to the baseline; biomass systems attained 100% CO₂ reduction owing to renewable fuels. Economically, biomass boilers had the lowest unit energy production costs, while PV-assisted heat pumps faced the highest overall costs despite their superior environmental benefits. The findings highlight the trade-offs between ecological advantages, energy efficiency, and investment costs, offering a decision-making framework for the modernisation of sustainable residential heating systems. Full article

The growing demand for energy-efficient heating, ventilation, and air conditioning (HVAC) systems has increased interest in multi-source heat pumps as a sustainable solution. While extensive research has been conducted on heat pump performance prediction, there is still a lack of practical tools for early-stage system evaluation. This study addresses that gap by developing regression-based models to estimate the performance of various heat pump configurations, including air-source, ground-source, and dual-source systems. A simplified performance estimation model was created, capable of delivering results with accuracy levels comparable to TRNSYS simulation outputs, making it a valuable and accessible tool for system evaluation. The analysis was conducted across nine climatic zones in Italy, considering key environmental factors such as air temperature, ground temperature, and solar irradiance. Among the tested configurations, hybrid systems like Solar-Assisted Ground-Source Heat Pumps (SAGSHP) achieved the highest performance, with SCOP values up to 4.68 in Palermo and SEER values up to 5.33 in Milan. Regression analysis confirmed strong predictive accuracy (R² = 0.80–0.95) and statistical significance (p < 0.05), emphasizing the models’ reliability across different configurations and climatic conditions. By offering easy-to-use regression formulas, this study enables engineers and policymakers to estimate heat pump performance without relying on complex simulations. 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

Energy transition is a challenge for remote northern communities mainly relying on diesel for electricity generation and space heating. Solar-assisted ground-coupled heat pump (SAGCHP) systems represent an alternative that was investigated in this study for the Kuujjuaq Forum, a multi-activity facility in Nunavik, Canada. The energy requirements of community buildings facing a subarctic climate are poorly known. Based on energy bills, technical documents, and site visits, this study provided an opportunity to better document the energy consumption of such building, especially considering the recent solar photovoltaic (PV) system installed on part of the roof. A comprehensive model was developed to analyze the building’s heating demand and simulate the performance of a ground-source heat pump (GSHP) coupled with PV panels. The air preheating load, accounting for 268,200 kWh and 47% of the total heating demand, was identified as an interesting and realistic load that could be met by SAGCHP. The GSHP system would require a total length of at least 8000 m, with boreholes at depths between 170 and 200 m to meet this demand. Additional PV panels covering the entire roof could supply 30% of the heat pump’s annual energy demand on average, with seasonal variations from 22% in winter to 53% in spring. Economic and environmental analysis suggest potential annual savings of CAD 164,960 and 176.7 tCO₂eq emissions reduction, including benefits from exporting solar energy surplus to the local grid. This study provides valuable insights on non-residential building energy consumption in subarctic conditions and demonstrates the technical viability of SAGCHP systems for large-scale applications in remote communities. Full article

In this study, a novel solar-assisted heat pump (SAHP) system with hybrid thermal energy storage is proposed. The system can address the problems of large space requirements and the unstable heating of solar heating systems and tackle the energy-efficient degradation of air source heat pumps (ASHPs) in winter. This study utilized TRNSYS18 software to establish a dynamic simulation model of the system, including the system’s model construction and the control scheme’s design. This performance study focused on analyzing the effects of the collector area and thermal energy storage (TES). The results show that with the increase in the collector area, the collector and power generation efficiencies decrease, and the system performance coefficient improves; the rise in the volume of TES leads to the collector and power generation efficiencies first increasing, and then they tend to stabilize, and the performance coefficient shows a trend of firstly increasing, and then decreasing. In terms of parameter optimization, a target optimization scheme and an evaluation model are constructed. The results indicate that the heating demand for a 116-square-meter building in the Tianjin area is met. The equivalent annual cost (EAC) of the system cost is the lowest, which is CNY 3963, when the collector area of the system is 31 square meters, the heat storage tank (HST) volume is 0.4 cubic meters and the phase-change energy storage (PCES) volume is 0.2 cubic meters. The payback period of the system is 10.59 years, which was compared to that of the ASHP. The further comparison of the economic feasibility of the system in the Lhasa, Shenyang, and Tianjin regions shows that the Lhasa region has the lowest EAC and payback period of CNY 1579 and 8.53 years, respectively, while the payback periods of Tianjin and Shenyang are 10.59 and 10.3 years, with EACs of CNY 3963 and CNY 5096, respectively. Full article

Heat pumps in buildings allow for the limiting of CO₂ emissions by exploiting directly the renewable energy available in the external environment (aerothermal, hydrothermal and geothermal sources). Moreover, other renewable technologies such as active solar systems can be integrated easily into use with them. This combination not only increases the share of primary energy provided by renewable sources for heating/cooling but also improves the heat pump performance indices. Nevertheless, in cold climates, air–water heat pumps should be equally penalized due to the unfavorable outdoor air temperature. Conversely, a water–water heat pump, connected with a solar tank and thermal solar collectors, overcomes this issue. Indeed, the higher temperature attainable in the cold source allows for reaching greater COPs, and when the solar tank temperature level is enough, emitters can be directly supplied, avoiding the absorption of electric energy. In this paper, this plant configuration, in which a further tank after the heat pump was considered to manage the produced thermal energy, is investigated. Proper control strategies have been developed to increase the renewable share. Regarding a reference residential building located in Milan, for which the water–water heat pump was sized properly, a parametric study, carried out in TRNSYS by varying solar tank volume and collecting surface, has allowed for the identification of the optimal system configuration. A renewable share, ranging between 54% and 61% as a function of the collecting surface and the storage volume, was detected, as was an average seasonal coefficient of performance (SCOP) over 4. Regarding two common heating plant configurations using an assisted PV air-to-water heat pump and a gas boiler, the optimal solution allows for the limiting of CO₂ emissions by 33% and 53%, respectively. Full article

In this paper, a solar-assisted enhanced vapor injection air-source heat pump (SC-EVIHP) system was built to investigate its heating performance in cold regions. A typical-weather day in Harbin was selected for the experiment, and the heating characteristics of the SC-EVIHP system were explored under variable working conditions. The experimental results showed that the system was greatly affected by solar radiation intensity. On typical-weather days in winter, the maximum values for the heating capacity and COP of the system appeared at the time of maximum radiation intensity. Compared with conventional enhanced vapor injection air-source heat pump systems (EVI-ASHPs), the heating capacity and COP were increased by 24.9% and 12.5% at most, respectively. The COP of the system increased by at most 11.1% under conditions where the outdoor temperature was −12 °C and the outlet hot air temperature of the solar air collector was 40 °C. The SC-EVIHP system works well in a low-temperature environment and can be widely applied in cold regions. Full article

Membrane desalination (MD) is preferred over other desalination techniques since it requires a lower temperature gradient. Its performance can be further enhanced by preheating the intake of saline water. In this context, a novel solar-assisted air gap membrane desalination (AGMD) system was hypothesized. The motivation was derived from the fact that the use of solar energy to provide power and a pre-heating source for the intake of saline water can offer a sustainable alternative that can further enhance the acceptance of MD systems. Since solar panels suffer from a loss of efficiency as they heat up during operation, a solar-assisted air gap membrane desalination (AGMD) system can help to improve the overall system performance by (1) providing the necessary pumping power to operate the system and (2) improving solar panel performance by exchanging heat using water that is (3) used to pre-heat the saline water necessary for increased performance of the AGMD system. To verify the hypothesis, a solar-assisted AGMD system for freshwater production was theoretically designed, fabricated locally, and then tested experimentally. The effect of the process operating parameters and the ambient conditions on the overall performance of the proposed solar-assisted AGMD desalination unit is presented in detail, both theoretically and experimentally. The results indicated a direct correlation between the permeate flux, saline hot feed temperature, and hot feed flow rate. In addition, an inverse relationship between the cold feed temperature, cold feed flow rate, and the air gap thickness of the module was also observed and reported, thus, validating the hypothesis that a solar-assisted air gap membrane desalination (AGMD) system can help to boost performance. Full article

The solar-assisted electric boiler water heating systems adopted in student apartments at universities have some shortcomings, such as unsuitable system designs, unstable water supply temperature, and excessive power consumption. As discussed in this paper, the hot water supply system was reformed, and two apartments with the same building area, same solar collector area, and similar water consumption were selected to be used in comparative experiments. The auxiliary heat source for one of the apartments was changed from an electric boiler to three air source heat pumps, and a constant temperature water tank was added to form a double-tank water supply system. In addition, the operation strategy was adjusted. The other apartment was not modified. The energy consumption, solar fraction, water supply quality and economy of the two systems were analyzed and compared. The results showed that the transformation plan is reasonable and feasible. The solar fraction of the reformed system was significantly improved. The water supply temperature of the original system ranged from 35 °C to 60 °C, but it was shown to stabilize between 40 °C and 50 °C after the transformation. The average power saving rate of the reformed system reached 72.70%, and this economic benefit is highly significant. Additionally, the TRNSYS simulation software was used to model and optimize the control of the system. Full article

A heat pump is an energy-effective technique to provide heating for buildings using available heat sources from the environment. Solar irradiation and ambient air are the most accessible heat sources among different heat sources; however, they are unstable for a day or several days. A large volume of the heat storage tank is usually required to provide a stable heating supply. As the most commonly used media for heat storage, water has a limitation on the heat storage temperature, i.e., above 0 °C, limiting its density of energy storage. This paper presents an experiment that evaluated the performance of a developed ice source heat pump used for assisting a solar heating system. The ice source heat pump can extract both sensible heat and the latent heat of water freezing, which doubles the density of energy storage and increase the heating output by 50%. The experiment results showed that the solar heating system tested could supply hot water at the highest temperature of 60 °C (with intense sun irradiation) and the lowest temperature of 40 °C (without sun irradiation). The min COP of the ice source heat pump was three, measured when the heat pump extracted heat from the ice water. This technology could be used for domestic heating with 50% reduced heat storage volume. Full article

In this paper, a simulations model of a seasonal thermal energy storage (TES) reactor integrated into a house heating system is presented. The water vapour chemisorbing reactor contains a composite material composed of silica gel and hydrated magnesium carbonate (nesquehonite, MgCO₃·3H₂O) that can be produced by a carbon capture and storage by mineralisation process. The performance of the TES to supply winter heat instead of electrical resistance heat is analysed. Dividing the reactor into a few units (connected in series) for better heat output and storage capacity as developed by the authors is compared to one unit or parallel unit solutions. The heating system components are an exhaust air heat pump, solar collectors and a heat recovery ventilation unit (HRV). The TES is used as heat source during colder periods, which implies improved efficiency and coefficient of performance (COP). Around 70% of electrical resistance heat, assisting an exhaust air heat pump during cold periods, can be substituted with heat from the TES according to the simulation model. Connecting three units in series will increase the usable storage capacity possibilities with by a 49% higher heat output. Full article