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In this paper different combinations of solar energy and heat pump systems are compared and investigated through transient system simulations. The focus is on a small capacity heat pump (HP) with a heating capacity rate of 5.36 kW. The building (single family house 140 m 2 ) which are considered in this paper have a space heating demand of about 45 kW h/m 2 a. Based on a conventional air source HP and a parallel solar air source HP system, serial solutions for the combination of solar-HP systems are defined and analysed. For the consideration and evaluation of different systems through transient system simulations, a semi-physical HP-model is used, which offers the possibility to use two evaporators in series. With a combined parallel solar air source HP system the system performance (SPF System = 3.65) can be increased significantly compared to a conventional air source HP system (SPF System = 2.55). Unglazed selectively coated absorbers as source for the HP offer the advantage, that the collector can be used as an air heat exchanger. If solar radiation is available, higher temperatures at the evaporator of the HP can be achieved, compared to a conventional air source HP system. By the integration of unglazed solar absorbers as source for the HP the HP performance can be increased significantly (SPF HP increases from 3.25 up to 3.55 compared to a conventional air source HP). [ABSTRACT FROM AUTHOR]

Trigeneration systems based on renewable energies are useful solutions to provide heat, cooling and electricity in buildings and industries. According to the International Energy Agency, more than 30% of the world population has a profile demand requiring heating and cooling and this percentage is above 70% in many developed countries. This paper experimentally evaluates the energy performance of a trigeneration system based on a solar PVT-assisted heat pump installed in an industrial building. The heat pump is a vapor compression air-to-water type, with a nominal capacity of 16 and 10.5 kW in heating and cooling respectively. The PVT solar field consists of unglazed PVT collectors with a total area of 13.6 m2. Results indicate that this type of system is effective to provide heat, cooling and electricity, using mainly solar energy. The PVT solar thermal fraction is significant to provide domestic hot water, but it is less representative in heating production. On the other hand, solar electrical production gets high representative contributions to feed the heat pump compressor. Different performance indicators were calculated to evaluate the system performance. Besides, a comparison with a reference system, that uses a PV instead of a PVT technology, was also evaluated. [ABSTRACT FROM AUTHOR]

The rise of clean energy such as solar energy provides a new idea to optimize the energy structure, and Photovoltaic thermal (PVT) heat pump system is one of the mainstream development at present. The wrong sensor data will have a great impact on the control and efficiency of the whole PVT heat pump system. In order to deal with this situation, Virtual in-situ calibration (VIC) based on Bayesian inference and Markov chain Monte Carlo (MCMC) is applied to PVT system. This paper presents a generic sensor fault diagnosis and calibration method for building energy systems using a PVT heat pump system as an example. Firstly, the data generated based on the mathematical model of PVT system is used to test the feasibility of VIC in this system. The results show that VIC can well reduce the systematic error and random error of the sensor. However, with the further study, it is found that in the actual system, it is impossible to establish a mathematical model which can reflect the relationship between the sensors with high accuracy. The VIC may fail or even have worse calibration results. Therefore, in order to solve the above problems, this study suggests using sparse autoencoder model instead of mathematical model. The model proved to be more accurate and to reflect the interconnectedness of the sensors, which helped the implementation of the VIC. The calibration method based on sparse autoencoder (SAE) can calibrate not only a single sensor in the PVT heat pump system, but also multiple sensors in a local area. After sparse autoencoder Virtual in-situ calibration (SAE-VIC) calibration, systematic and random errors of all sensors can be effectively reduced, and the accuracy of sensor calibration can reach more than 90 %. [ABSTRACT FROM AUTHOR]

Outdoor air is a common heat source for heat pumps, whose limits are well known. However the use of different sources requires additional investment costs. It is then interesting, starting from a given additional investment, on one side to evaluate different compositions for a set of sources and on the other to choose the most favourable source from time to time, according to the building energy demand and the thermal level of each available source. This paper presents a study conducted on the base of a heating system based on multi-source heat pumps. By means of dynamic simulations in TRNSYS, several scenarios were assessed with respect to primary energy consumption in order to define, given an additional budget for the heat pump system, whether it is a good option to invest in ground source or in solar source for the heating systems. The analysis reveals that the most energy efficient solution both for absorption and compression heat pump based systems is to adopt a multi-source system; the ground exchangers should then be sized to allow a minimum ground inlet temperature of −2 °C, and the saving in investment cost should be directed to buy solar collectors. [ABSTRACT FROM AUTHOR]

This paper introduces a multi-stage heat storage system using phase change materials with different melting points into the heat pump solar absorption refrigeration system which proposed by our earlier research work. Using meteorological data for the city of Nanjing, the performance of the novel system with a cooling capacity of 10 kW is quantitatively analyzed: (1) More than 91 m 2 of solar collection area is required for the single flat-plate collector to satisfy the daily need of cooling. (2) Four different types of collectors, including single flat-plate collector, all-glass vacuum tube collector, heat pipe evacuated tube collector, and compound parabolic vacuum tube collector are compared. The results of solar collection areas show that the difference among them is not significant. Considering the building adaptability and production cost in the application designs, single flat-plate collector is preferred. (3) The coefficient of performance for the system with multi-stage heat storage system is approximately 1.3–2.4 times to that with the corresponding single-stage heat storage system at the given conditions. (4) The coefficient of performance of the novel system increases with the melting points of the phase change materials in the heat storage system when the solar radiation intensity is high (0.8 kW/m 2 ), and behaves the opposite when the solar radiation intensity is low (0.3k W/m 2 ). [ABSTRACT FROM AUTHOR]

This paper deals with the methodology of sizing a sustainable heating–cooling system, which consists of a heat pump, thermo-solar collectors and underground water tank, as a seasonal thermal energy storage. The methodology is based on successive and coupled energy balancing of all system elements for time intervals of 1 h, during one representative calendar year. The starting assumption for the calculation contains the size of the underground storage tank, its burial depth, the size of building that is heated or cooled, and the temperature of air in the building. To make the calculation, it is necessary to know the so-called dynamic boundary conditions during a calendar year, comprising the following: hourly outdoor air temperature, hourly insolation (received solar radiation energy) and hourly temperature of the ground surface. The calculation result is the size of the thermal–solar collectors surface, which will ensure the sustainability of the system, i.e. it will ensure that after one year of operation this system is restored to the original conditions, without disturbing natural environment in which it is used. For the purpose of presenting the methodology and checking the influence of individual parameters of the system's operation, a numerical simulation was performed and required surfaces of thermo-solar collectors were determined for one of the system models. Analyses of the influence of the underground tank burial depth, tank size and the initial water temperature in the tank on the required size of thermal–solar collectors were also performed. [ABSTRACT FROM AUTHOR]

Solar-ground source heat pump system (SGSHPS) is a new type of high efficiency, energy saving and environmental protection air-conditioning technology. In this paper, experimental studies and numerical simulation on the performance of a SGSHPS operated in different heating modes were carried out. The experimental system was installed in Nanjing of China and solar collectors were coupled with ground heat exchangers (GHE) through an insulated water tank. Four operation modes including ground source heat pump (GSHP), combined operation mode, day and night alternate operation mode and solar U-tube feeding heat alternate operation mode were investigated during winter season. The heat pump performance, solar collecting performance and borehole wall temperature variations were analyzed and compared for various modes. The experimental results indicate that for the combined operation mode, the system operation efficiency during day can be improved by the assistance of solar energy, and the excess solar energy collected during day can be stored in ground by the GHE to improve the operation performance of GSHP during night. The proportions of heat source burdened by solar and geothermal energy are 43.3% and 50.2% respectively. For the alternate operation modes, the temperature resumption of ground surrounding the GHE can be well achieved due to the intermittent heat extraction of GHE or feeding solar heat into ground and thus the overall utilization efficiency of solar and geothermal energy can be improved greatly. During the whole experimental period, the average COPs are 2.37 and 2.72 for GSHP and SAHP operation mode respectively, and the corresponding parameters are 2.69, 2.65 and 2.56 for the combined operation mode, day and night alternate operation mode and solar U-tube feeding heat alternate operation mode, respectively. The average solar collecting efficiency are 43.6%, 47.3% and 38.8% for the combined operation mode, SAHP operation mode and solar U-tube feeding heat operation mode, respectively. Based on the unit modeling, a dynamic simulation program was constructed to investigate the seasonal performance of the SGSHPS operated in different heating modes, the simulation results show that the seasonal average COP are 3.67, 3.64, 3.52 and 3.48 for the combined operation, day and night alternate operation, solar U-tube feeding heat and GSHP mode, respectively. From the view of improving the overall efficiency and increasing heat source fraction of solar energy, the combined operation mode is the best. [ABSTRACT FROM AUTHOR]

Obtained as a research result of conducted project, this paper presents an innovative, energy efficient multipurpose system for a sustainable globally cost-effective building's solar energy use and developed methodology for its dynamic analysis and optimization. The initial research and development goal was to create a cost-effective technical solution for replacing fossil fuel and electricity with solar energy for water heating for different purposes (for pools, sanitary water, washing) in one SPA. After successful realization of the initial goal, the study was proceeded and as a result, the created advanced system has been enriched with AC performance. The study success was based on understanding and combined measurements and by BPS made predictions of AC loads and solar radiation dynamics as well as on the determination of the synergetic relations between all relevant quantities. Further, by the performed BPS dynamic simulations for geographically spread buildings locations, it has been shown that the final result of the conducted scientific engineering R&D work has been the created system of confirmed prestigious to the sustainability relevant performance – globally cost-effective building integrated photovoltaic powered heat pump (HP), assisted by waste water heat recovery, for solar AC, water heating and saving. [ABSTRACT FROM AUTHOR]

• An experiment of SGHP system and the detail description of combi-storage are presented. • Five daily operation modes are identified using the contributions of the energy inputs. • The dynamic thermal behaviors of the combi-storage are investigated and analyzed. Experimental investigations on thermal behavior of a combined solar and ground source heat pump (SGHP) system for a single-family house are presented. The SGHP system was installed at the Lyngby campus of Technical University of Denmark. Detailed experiments were carried out on the system in 2019 under real weather conditions covering domestic hot water (DHW) consumption and space heating (SH) demand. Depending on the contributions of the energy inputs to the combi-storage, five typical daily operation modes are classified. The focus of the investigations is on the dynamic thermal behaviors of the heat storage under different operating conditions. When the combi-storage was primarily heated by solar energy, the inlet stratifier in the storage performed well, ensuring thermal stratification and a good utilization of solar energy. Water temperature in the storage reached up to about 68℃ at the end of the solar heating process. When the combi-storage was primarily heated by the ground heat, the water temperature near the outlet for SH was kept at a temperature range from 26℃ to 31℃ in the heating process to ensure the outlet temperature level of SH, and the water temperature near the outlet for DHW was in the temperature range 47℃∼51℃ in DHW volume. When there was no heat input to the combi-storage, the pre-stored heat can meet the daily heating demand, and the number of days on this mode was up to 9.4% of the total experimental days. The paper gives valuable inputs for researchers and engineers who plan to integrate the combi-storage in a renewable heating system with solar collectors and ground source heat pumps. [ABSTRACT FROM AUTHOR]

Abstract: A new system of solar air-conditioning, which adds the heat pump into the original solar air-conditioning, is proposed in order to improve the solar energy application grade. The new type of solar air-conditioning system is analyzed and compared with the original system. Calculations show that: (1) when the sun radiation intensity is high (0.8kW/m2), the cooling capacity of the new system is 1.7 times the original system under the given conditions of this paper. When the sun radiation intensity is low (0.2kW/m2), the cooling capacity of the new system is decreased by 70% compared to high radiation intensity conditions, and the original system could not provide refrigeration. (2) In a certain solar radiation intensity, new type solar air-conditioning system reduces the requirement of a high efficiency solar collection system (SCS). At a certain collector efficiency, it can operate stably by adjusting the water mass flow rate of SCS under different solar radiation intensities. (3) For the heat pump system (HPS) of the new type solar system, under the same rage of evaporation temperature and condensation temperature, R600a HPS has higher COP and less power consumption than R134a HPS under obtaining same cooling capacity condition. [Copyright &y& Elsevier]

Abstract: This paper proposed a new solar assisted air source heat pump system with flexible operational modes to improve the performance of the heating system. A mathematical model was established on the solar assisted air source heat pump system for building heating with a heating capacity of 10kW, and an air source heat pump unit was developed to validate the model. The effect of the solar collector area on the performance of the system running in Nanjing was studied. The results showed that the COP of the heat pump unit was enhanced with the increase of the solar radiation density during the typical sunny day in the heating season. In addition, the COP also increased in proportion to the solar collector area. Compared with the case when the solar collector area was 0m2, the COP increase of the heat pump and the energy-saving rate were 11.22% and 24% respectively when the solar collector area was 40m2. Meanwhile, the solar equivalent generation power efficiency could reach 11.8%. [Copyright &y& Elsevier]

Abstract: This paper introduces a solar-assisted ground-coupled heat pump (SAGCHP) system with heat storage for space heating and domestic hot water (DHW) supply. The simulation results of the system''s detailed operating performance are presented. The optimization of the system design is carried out by the TRNSYS and a numerical simulation is performed for continuous operation of 20 years under the meteorological conditions of Beijing. Different control strategies are considered and the operational characteristics of each working mode are studied. The simulating results show that the long term yearly average space heating efficiency is improved by 26.3% compared to a traditional ground coupled heat pump (GCHP) system because the solar thermal collecting system is used to elevate the thermal energy in the soil and to provide direct space heating with heat storage. At the same time, the underground heat load imbalance problem for a heating load dominated GCHP is solved by soil recharging during non-heating periods, while extra solar energy is utilized to supply DHW. The flexibility and high efficiency of the SAGCHP system could offer an alternative for space heating and DHW supply by heat pump technology and solar energy in cold winters of northern China. [Copyright &y& Elsevier]

Abstract: This paper presents the experimental study of a solar-assisted ground-coupled heat pump system (SAGCHPS) with solar seasonal thermal storage installed in a detached house in Harbin. The solar seasonal thermal storage was conducted throughout the non-heating seasons. In summer, the soil was used as the heat sink to cool the building directly. In winter, the solar energy was used as a priority, and the building was heated by a ground-coupled heat pump (GCHP) and solar collectors alternately. The results show that the system can meet the heating–cooling energy needs of the building. In the heating mode, the heat directly supplied by solar collectors accounted for 49.7% of the total heating output, and the average coefficient of performance (COP) of the heat pump and the system were 4.29 and 6.55, respectively. In the cooling mode, the COP of the system reached 21.35, as the heat pump was not necessary to be started. After a year of operation, the heat extracted from the soil by the heat pump accounted for 75.5% of the heat stored by solar seasonal thermal storage. The excess heat raised the soil temperature to a higher level, which was favorable for increasing the COP of the heat pump. [ABSTRACT FROM AUTHOR]

• Multicriteria comparison of technical solutions for residential heat production. • Energy, exergy, economic, exergoeconomic and environmental indicators. • Sensitivity study on solar matching, LCOE and exergy destruction cost. • Extended qualitative discussion including more technical and operational criteria. • Some grid-driven solutions are competitive (efficient, de-carbonized French grid). The French energy market is highly reliant on nuclear power. Several factors pressure for a phase-out of this technology, but finding an environmentally and economically competitive substitute is not easy. Renewable sources are a candidate, and a full deployment in the residential sector could significantly reduce nuclear-based electricity production in France. In this paper, we assess multicriteria competitiveness of renewable energies for residential heat production in a French dwelling. A total of 9 solutions combining the following systems are compared: boilers (electric, biomass or gas-fired), heat pumps (air-source or ground-source) and solar panels (solar thermal or photovoltaic). Global performance is analyzed for each solution through energy, exergy, economic, exergoeconomic and environmental (5E) multi-criteria analysis considering energy efficiency, exergy efficiency, Levelized Cost Of Energy, exergy destruction cost and CO 2 mitigation. Sensitivity of selected indicators is analyzed with respect to the heat load, the investment cost and the fuel cost. The ground-source heat pump and the biomass boiler are found to be the most competitive solutions. It is also found that temporal mismatch between production and consumption is the major drawback of solar-driven solutions, especially for solar thermal collectors. One of the innovations of this study is comparing various residential heat production systems through various performance criteria. The other innovation is applying the study in the French context, which has a very high share of non-carbon electricity. Results from this study can be generalized to other OECD countries in future conditions, i.e. when their shares of non-carbon electricity become very high. [ABSTRACT FROM AUTHOR]

This paper presents experimental investigations on a combined solar and ground source heat pump (SGHP) system for a single-family house. The SGHP system was installed at the Lyngby campus of Technical University of Denmark with horizontal ground heat exchanger (HGHE). Detailed experiments were carried out on the system in 2019 under real weather conditions and the heating demand for domestic hot water (DHW) and space heating (SH). The focuses of the investigation are energy flow analysis and performance assessment on the SGHP system. The results showed that the yearly system seasonal performance factor of the SGHP system (SPF SHP) was 2.8, and the maximum monthly SPF SHP was up to 5.7 in April with the highest solar radiation. Directly utilized solar energy for the combi-storage was 500 kWh lower than the annual solar heat for charging the ground, and it accounted for 36.6% of annual heat input of the combi-storage, the rest of the heat was supplied by the heat pump system that consumed 84% of total electricity energy. Different from the large fluctuations of monthly solar fraction due to solar radiation, the monthly renewable heat fraction was within the range from 57% to 83%, and the yearly value was 65%. [ABSTRACT FROM AUTHOR]

A solar air-source heat pump system with phase change energy storage is investigated in this paper. By employing phase change storage in this system, it overcomes the frosting problem in the evaporator and improves the COP of heat pump under the extreme weather condition. The system is constructed and the experiment is carried out in Shijiazhuang. The testing results reveal that the average COP of the heat pump is around 4.92 in the clear days, 1.79 in extreme weather conditions, and 2.12 in the rainy or snow days, which is much higher than the traditional heating mode. Through economic analysis, it is found that the operating cost of the whole heating season is around 22.5% of the oil-fired boiler, 55.4% of the gas boiler, 27.1% of the electric boiler, and 65.6% of the air source heat pump. With the help of phase change storage, solar energy and air source can be utilized to the maximum extent to achieve the purpose of energy-saving and emission reduction in the extremely cold area. [ABSTRACT FROM AUTHOR]