Assisted Heat Pump Research Articles

Incorporation of controllable supercooled phase change material heat storage with a solar assisted heat pump: Testing of crystallization triggering and heating demand-based modelling study

In short to long-term heat storage, the heat loss of common phase change material (PCM) systems is a big problem where heat is lost continuously to the ambient environment and is thus wasted, even when the system is not in use. Controllable supercooled PCM in the proposed system offers a solution to this problem. Latent heat is only released when the supercooled PCM is triggered to induce crystallization, so it can be stored at ambient temperature. To control the release of heat, the installation will be constructed as a group of PCM storage units, each with its own trigger, which can be activated according to the heating demand of a building perhaps over several days. The proposed versatile PCM energy storage system can play an essential role in synchronizing energy demand and supply, on a short to long-term basis (days/weeks). In this study, an electrical triggering mechanism is constructed and tested in the laboratory to control the crystallization of the PCM. The PCM temperature increased from 20 °C to 56.4°C in 20s after triggering. After validation of controllable crystallization and melting time, a solar-assisted heat pump coupled with supercooled PCM storage units was simulated considering the heating demand profile of an eco-house in Nottingham, UK. The charging time of the PCM tank was found 6.5h when 8 cm diameter PCM tubes were adapted. During discharging period, the hot water supply temperature was achieved at higher than 43 °C, considering the one-day heating profile of the building.

Numerical study on seasonal operation of solar assisted hybrid borehole heat exchange array

The combined use of solar energy and ground-source heat pump system may provide a reasonable solution to the energy crisis and low utilization efficiency of single energy. Herein, a numerical model of a solar assisted hybrid ground-source heat pump (SAHGSHP) system composed of multiple types and lengths of borehole heat exchanger (BHE) array was developed. The effectiveness of this model was validated by experimental data of a SAHGSHP system located in Tongzhou, Beijing. The verified model was used to study the performance sustainability of SAHGSHP system under different seasonal operation modes and its influence on the temperature of rock and soil. It was shown that for different types of BHEs in heat extraction periods of SAHGSHP systems, the outlet temperature decline rate decreases by an average of 2.30%, the temperature decline rate of rock and soil at the reference point under single-season operation decreases by an average of 0.78%, and the temperature increase rate of rock and soil at the reference point under double-season operation increases by an average of 0.53% compared with that of hybrid ground-source heat pump (HGSHP). The results of this study could provide a further understanding for analyzing the seasonal operation mode of SAHGSHP.

Performance Analysis of Direct Expansion Solar Assisted Heat Pump Using Typical Meteorological Year

Performance Analysis of Direct Expansion Solar Assisted Heat Pump Using Typical Meteorological Year

Low temperature heating operation performance of a domestic heating system based on indirect expansion solar assisted air source heat pump

Reducing electricity consumption is of great importance by improving the operation performance of the heating systems based on solar-assisted air source heat pumps for domestic heating. The set hot-water-supply temperature of the heating system affect both the system operation performance and the indoor thermal comfort condition. The effect of low temperature heating on the system operation performance is investigated to figure out the way to significantly save electricity. A single-family house is chosen as the reference building and the heating system is modelled and simulated under the weather conditions in the locations of London, Aughton and Aberdeen in the UK over a year. The set hot-water-supply temperatures are taken to be 40 °C, 45 °C, 50 °C and 55 °C. For the heating systems, with the decrease in set hot-water-supply temperature from 55 °C to 40 °C, the yearly seasonal performance factor increases by 16.7%, 19.1% and 15.4% in London, Aughton and Aberdeen, respectively. Consequently, the yearly total electricity consumption decreases by 19.1%, 14.9% and 13.3% in London, Aughton and Aberdeen, respectively. The results show that low temperature heating enables significant reduction in electricity consumption of such heating systems.

The Impact of Energy Renovation on Continuously and Intermittently Heated Residential Buildings in Southern Europe

To achieve carbon neutrality in the EU, it is important to renovate the existing EU residential buildings for a higher building energy efficiency. This study examines the impacts of several novel renovation technologies on energy consumption, CO2 emissions and indoor climates in southern European residential buildings through building-level simulations. Three typical residential buildings in South Europe were chosen as the demo buildings to implement the novel technologies. The technologies were classified into passive, ventilation and generation packages, and then simulated independently under the intermittent and continuous heating schedules. Additionally, two final combinations of renovation technologies were also simulated to demonstrate the maximum energy and CO2 emissions reduction potential of the demo buildings. All novel retrofit technologies manifested obvious effects on the energy consumption and CO2 emissions. Nevertheless, the effects were significantly affected by the heating schedule. When the intermittent heating schedule was switched to the continuous heating schedule, the relative energy conservation and CO2 emissions reduction potential of the thermal insulation improvement measures (e.g., bio-aerogel thermal insulation) increased, while those of the generation measures (e.g., solar assisted heat pump) diminished. Renovation with the final combinations reduced the primary energy consumption by up to 66%, 74% and 65% in the continuously heated Greek, Portuguese and Spanish demo buildings, the corresponding CO2 emissions reductions of which were 65%, 75% and 74%, respectively.

Solar assisted air source heat pump systems for campus water heating in China: Economic optimization of solar fraction design

• TRNSYS software is to simulate the solar assisted air source heat pump system . • The solar fraction design values of solar water heating systems are not economically optimal in China. • Long-term economic optimization of solar fraction design values for solar assisted air source heat pump systems is performed. • An ANN-generated proxy model is to predict the most economical solar fraction design values of solar assisted air source heat pump systems. The solar assisted air source heat pump (SAASHP) system is widely used for campus water heating owing to its cost-effectiveness and cleanliness. In the current design process of the SAASHP system, the solar collector area is determined by the solar fraction ( f ). However, it is difficult to design a cost-optimal f that can comprehensively take the atmospheric factors, device model, electricity price and initial investment into consideration. To address this issue, a SAASHP system that meets the bathing hot water demand of 480 students was established by TRNSYS software, and the cost-optimal solar collector areas and f values for 12 cities across 4 different solar resource regions in China were obtained by the TRNOPT tool of TRNSYS. Moreover, the effects of SC price, electricity price, bathing hot water demand and rated COP of ASHP on cost-optimal f values were investigated by sensitivity analysis. Finally, a proxy model was generated by the artificial neural network toolbox of MATLAB to predict the cost-optimal f values for different scenarios. The results showed that compared to the economically optimized SAASHP system, the designed SAASHP system according to the national design standards for solar heating systems in China has a larger SC area value, leading to an increase in the annual life cycle cost of the system. The difference between the optimized and designed values of solar collector area and f for the SAASHP system was minor in rich resource and sub-rich resource regions but was larger in general resource and poor resource regions. The solar collector price, electricity price, bathing hot water demand and the rated COP of the SAHP were significant factors affecting the annual life cycle cost, the cost-optimal f and solar collector area of the SAASHP system. The proxy model generated by the artificial neural network toolbox of MATLAB can accurately predict the economically optimal solar collector area and f values for SAASHP systems in different cities and system factors, providing a method for the economic design of SAASHP systems in China.

Investigation on transient response of the direct expansion solar assisted ejector-compression heat pump cycle for water heater

Aiming to provide data support for the control-oriented design and practical application, the transient response characteristics of the direct expansion solar assisted ejector-compression heat pump cycle for water heater is investigated in this study. The dynamic simulation model of the presented system is built, and relevant experimental items are also conducted to verify the simulation model. The experimental and simulation results during a typical water heating process show satisfactory agreement, and the maximum forecast error of four main operation parameters is less than 6.6%. The system transient responses under the step change of the expansion valve opening degree are explored by both simulation and experimental methods, and the simulation model still appears high forecast precision. Thereinto, the maximum simulation error of the refrigerant flow rates is less than 5.2%. The system dynamic responses under the sudden changes of the ejector nozzle throat area and solar radiation intensity are further evaluated based on the verified model, and the coupling relation of the system pressure and refrigerant flow rate is further revealed. In addition, further simulation research proves that substituting R134a with R1234yf and R1234ze(E) in the present system has little impact on the system dynamic characteristics.

Techno-economic approach for optimum solar assisted ground source heat pump integration in buildings

Two-step approach for optimum solar assisted ground source heat pump integration in buildings is proposed. At the first step energy targeting based on dynamic pinch analysis allows to target the energy and optimum equipment size according to buildings’ dynamic demands, and as a result, several energy efficient daily design candidates are extracted. At the second step of the proposed approach, a final design working for the whole year is selected among all the candidates by computing the total annual cost (TAC). A special algorithm is proposed to compute the yearly average energy and capital cost penalty for complementary hot/cold utilities in order to adapt the daily designs to the overall year design. As an objective function, TAC is defined for a 20-year lifetime design. Moreover, the TAC of several daily optimum designs (DOD) based on different scenarios are investigated for a multifamily test building. In the context of Canadian market, it is illustrated that the choice of the overall year integration design depends mainly on the electricity cost. For example, with Quebec electricity cost (i.e., 0.073 CAD/kWh), the DOD of September is optimal for the whole year, where there is no need for vertical ground heat exchangers. However, if Canadian average electricity cost (i.e., 0.147 CAD/kWh) is considered, the DOD of March is optimal for the whole year, with a vertical ground heat exchanger depth of 200 m. The DOD of September and March can reduce building’s annual electricity consumption by 55.9% and 79.2%, respectively.

Mathematical Model of Radio Frequency Assisted Heat Pump Drying of Ganoderma Lucidum (Ganoderma Boninense)

This study proposed a mathematical model which was used to predict the temperature and moisture content of Ganoderma lucidum (Ganoderma boninense) during the radio frequency (RF) assisted heat pump (HP) drying process. The simultaneous heat and mass transfer equations were established based on the physical and flat plate models for drying Ganoderma lucidum and the specific assumptions for the proposed problem. The finite difference method was used to solve the proposed heat transfer and moisture transfer problem, in which, pdepe function was adjusted and complemented with Matlab software. The temperature and moisture content of the material in the drying process was predicted. The effect of the output RF power on the temperature and moisture content of the material was evaluated. The drying process's input parameters were drying air temperature of 40oC, air velocity of 1.2 m/s, and an output RF power of 1.95 kW, 0.65 and 0 kW. The results showed that when the output RF power increases, the heating rate increases, and the drying time is shortened significantly. The drying material temperature reaches the drying air temperature in 20 minutes, 30 minutes, and 220 minutes and the drying time is 465, 555, and 700 minutes, corresponding to output RF power of 1.95 kW, 0.65 and 0 kW. The predicted temperature and moisture content of the material were compared with experimental drying data, and a considerably good agreement was found.

Optimisation strategies for solar assisted heat pumps coupled to traditional thermal fields

The advantages of the solar assisted heat pumps are well-known but their diffusion on the market is still very limited. One of the main causes is associated to their complexity and almost always working under transient regime which can lead to frequent blocks especially when a low level of control and automatization is present. From the point of view of conceptual design, solar assisted heat pumps tend to be more subjected to blocks due to their serial asset. The present work illustrates the case study of the solar assisted heat pump pilot plant at Palacus, Genoa, equipped with a heat pump bypass which can directly connect the solar thermal field to either the domestic hot water or the space heating systems when the temperature in the circuit exceeds a fixed set point. This configuration allows therefore the use of the solar field either independently from the heat pump or interfaced with it, according to the external conditions. A numerical model within TRNSYS environment has been developed basing on the information collected on the pilot plant by the data acquisition system. A simulation of the working of the pilot plant along a typical year has been performed, evaluating its increased performance and optimisation thanks to the bypass.

Solar assisted heat pump modelling

In this study, the Solar Energy Assisted Heat Pump (SAHP) system is modeled by creating different processes with the help of various models created in the JAVA program. The SAHP model was created in order to obtain hot water by utilizing solar energy. The inlet water temperature in the system was taken as 10 °C in December and 20.5 °C in June and the SAHP model was analyzed by numerical method. In the evaporator model, considering the coordinates of the city of Izmir, various graphs were created by calculating the different spectral solar energy values falling on 1 m2 evaporator plate on certain days of 2019. In the graphics, the highest energy density on 1 m2 evaporator plate for İzmir province was 852.095 W/m2 on 21 June at 12:00, and the lowest energy density was 455.143 W/m2 on 21 December at 12:00. In the SAHP system, the evaporator plate area was determined as 2.40 m2 and the compressor power was 0.56kW, and a condenser model was created. The required condenser surface areas were found by calculating the thermal energies given by the condenser for different dates in the system. In the modeling of the heat pump, the Coefficient of Performance (COP) of the SAHP system for R134a and R404A was obtained by taking the date of June 21, 12:00, when the spectral energy is most intense, as a reference.

Energy, exergy, economic and environmental assessment of the triangular solar collector assisted heat pump

The solar air collector assisted air source heat pump is demonstrated to be an efficient clean heating technology, while the research on its working modes, and the corresponding energy, exergy, economic, environmental (4E) analysis is insufficient. In this study, a novel triangular solar air collector assisted air source heat pump (TSAHP) for building heating is proposed, and three working modes including preheating, series and parallel modes are illustrated. The energy model is established and used to determine the optimal working mode, and solved by Python environment. Four scenarios including TSAHP with three areas of triangular solar air collector (TSAC) and conventional air source heat pump (ASHP) are compared based on the optimal working mode. Thermodynamic performance of the four scenarios under different working conditions is analyzed, and result indicate that the TSAHP with 3 m2 TSAC can reduce the power consumption and exergy destruction of ASHP components by 321.9 kWh and 784.6 MJ respectively during the whole heating period. Economic evaluation shows that TSAHP has the shortest payback period with moderate TSAC area, and has economic advantages at low nominal interest rate and high electric power cost with large TSAC area. In addition, based on the whole life cycle, 1 m2 of TSAC can reduce CO2 emission by more than 4500 kg.

Energy targeting approach for optimum solar assisted ground source heat pump integration in buildings

Application of solar assisted ground source heat pumps (SAGSHP) in buildings have been increased in recent years. However, a systematic approach for integrating the optimum SAGSHP system in buildings in order to meet the space heating/cooling and the domestic hot water loads is still missing. A novel dynamic targeting approach is proposed. It can predict and guarantee the maximum possible direct and indirect heat recovery in a given building by introducing an interconnected network of heat exchangers (including ground heat exchanger) + energy storage (both electric and thermal energies) + heat pump (HP) + solar photovoltaic (PV) panels based on the real-time hot and cold composite curves (CCs). The main novelty of this approach consists in the fact that the dynamic building's loads and the time variation of renewable and waste sources of energies are included into the targeting procedure. The approach is applied to a multifamily test building, where the solar irradiance and building's heating and cooling demands are taken into account. In addition to the maximum heat recovery, the proposed approach computes the minimum area of the solar photovoltaic panels, the minimum volume of TES, and the minimum capacity of the electric energy storage for each representative day.

Research on the operation strategies of the solar assisted heat pump with triangular solar air collector

The solar-assisted heat pump (SAHP) is considered to be one of the efficient and promising clean heating technologies, while the research on its operation strategy is insufficient. In this study, a novel triangular solar air collector assisted air source heat pump (TSAHP) for rural residence heating is presented. Three working modes of the TSAHP including preheating, series and parallel modes were investigated, and corresponding mathematical models were established and verified. The effects of solar irradiance, outdoor temperature, indoor temperature, south wall covered area of the TSAC and the heating load on the performances of the three working modes were analyzed. The distribution diagram of the optimal working mode was designed, and the equations that define the boundaries between operating modes were fitted. Finally, the performances of the TSAHP under typical meteorological parameters were compared and analyzed based on the modified boundary equations. Results indicate that the TSAHP can sufficiently utilize solar energy. With the increase of solar irradiance, the optimal working mode is shifted from the preheating to series and parallel. Compared with the traditional air source heat pump system, the COP of the TSAHP under the optimal working modes could be increased by 64.4%.

Experimental and analytical analysis of the impact of different base plate materials and design parameters on the performance of the photovoltaic/thermal system

Solar energy is one of the most important and prospective renewable energy sources. Solar photovoltaic/thermal systems (PV/T), which could provide both heat and electricity at the same time, are becoming increasingly popular in households and commercial buildings. The PV/T system design parameters and base plate material selection are significant for achieving long-term dependability, longevity, and performance. The present work examines the effects of various base plate materials and design parameters on the performance of a PV/T assisted heat pump system, utilizing a validated mathematical model. Three different base plate materials, namely, aluminum (Al), copper (Cu), and Tedlar-Polyester-Tedlar (TPT), with a single-crystalline silicon photovoltaic module, were employed in the PV/T system design. According to the experimental results, the PV/T system with TPT base plate has a low photovoltaic module average temperature and a high average electrical efficiency which are 35 °C and 14.8%, respectively. The PV/T system with Cu base plate has the most optimal average thermal efficiency and coefficient of performance (COP) which are 48% and 3.93, respectively. In addition, the impact of the PV packing factor and the pitch of the heat pipe on the performance of PV/T system was examined and analyzed. For all types of base plate, the COP of the system decreases with the increase of PV packing factor and pitch of the heat pipe of the PV/T module.

Exploratory research on the field application of solar assisted air source heat pump system for rural buildings in Xinjiang

ABSTRACT A time-controlled solar assisted air source heat pump (SAHP) system was proposed in accordance with the climate characteristics of Xinjiang. Combined with an actual project of rural office building in Xinjiang, the time-controlled SAHP system test study was carried out . Test results showed that, on a typical day in the slightly cold period (SCP), the heat collection efficiency of the solar collectors was 68.12%, the solar energy utilization rate was 84.22%, and the indoor temperature increased by 5.2°C. On a typical day in the bitter cold period (BCP), the time-controlled SAHP system could provide more than 70% of the heating consumption. Furthermore, the feasibility of the time-controlled SAHP system was evaluated based on the data of the SAHP system and the traditional coal-fired boiler system in the same period. In comfort, the indoor temperature maintained at 14–20.2°C, and the average temperature was 18°C. In economy, the coal consumption of the time-controlled SAHP system was 18.34 kg/m2 during the heating period, which was 25.0% of that of the traditional heating method. In environmental protection, the time-controlled SAHP system could reduce CO2 emissions by 149.10 kg/m2, NOx emissions by 4.47 kg/m2, and SO2 emissions by 2.24 kg/m2 during the heating period.

Simulation analysis on operation performance of a hybrid heat pump system integrating photovoltaic/thermal and air source

• The evaporator model considering dynamic mass flow distribution is established. • The γ for switching between the solar-air mode and the solar mode is about 0.75. • The system performance is less affected by a single environmental factor. • The COP can reach 4.76 and the electric efficiency is 13.5% at 10 °C and 400 W/m 2 . To solve the instability of conventional single source heat pump and further improve energy efficiency, this paper presented a hybrid solar/air dual source assisted heat pump (S-A-AHP) water heater. Based on the system, a quasi-steady-state mathematical model was constructed to study the mode switching criterion and operation performance. The simulation results showed that it is more suitable to use the mass flow ratio of refrigerating medium (i.e., the ratio of the photovoltaic/thermal collector/evaporator to the whole system) as the criterion of system mode switching than directly using environmental factors, and the critical ratio for switching between the solar-air mode and the solar mode is about 0.75. In addition, compared with the conventional solar assisted heat pump (SAHP) and air source heat pump (ASHP), under the low environmental benefit conditions of ambient temperature of 0℃ and solar radiation intensity of 100 W/m 2 , the average COP of S-A-AHP is 29.7% and 19.9% higher than that of SAHP and ASHP, respectively. And the S-A-AHP system's heating time is only 36.7% of the SAHP and 83.7% of the ASHP. And the impact of collector area on system performance was also discussed.

Performance analysis of a solar thermal system coupled with a ground source heat pump in Nordic conditions

The main objective of this work is to investigate the energy and exergy performance of a solar assisted ground source heat pump for a school building designed according to Norwegian passive house standard. The system is designed in such a way that the solar collector prioritizes to provide heat to the hot water tank and whenever there is excess heat from the solar collector it can be used to charge the ground borehole. A detailed thermodynamic analysis of the system has been carried out in Engineering Equation Solver (EES). Isobutane (R600a), propane (R290), ammonia (R717) and solstice (R1234ze(E)) have been investigated as working fluid for the heat pump. The result revealed that the solar collector and the different working media have affected both the COP and the exergy of the system. Moreover, the mass flow rate of the brine and the length of the borehole affect the performance of the system.

Gas Cooler Moving Boundary Model of a Co2 Direct Expansion Solar Assisted Heat Pump for Sanitary Water Heating

Gas Cooler Moving Boundary Model of a Co2 Direct Expansion Solar Assisted Heat Pump for Sanitary Water Heating

Economic Operation Optimization of Solar Assisted Heat Pump Drying System Considering Heat Storage Characteristics of Drying Chamber

Economic Operation Optimization of Solar Assisted Heat Pump Drying System Considering Heat Storage Characteristics of Drying Chamber