Assisted Heat Pump Water Heater Research Articles

Experiment study on startup characteristics and operation performance of PV/T solar assisted heat pump water heater system driven by direct current variable frequency compressor

The use of renewable energy can alleviate climate warming and environmental pollution. PV/T (photovoltaic/thermal) system has been widely concerned and rapidly developed owing to its capability of generating electric and thermal energy simultaneously. In the article, a PV/T solar assisted heat pump water heater system driven by direct current variable frequency compressor was proposed to meet the growing needs of residents for domestic hot water. This system was tested in different working conditions in Lanzhou, and the startup characteristics and operation performance were evaluated. The results indicate that at the same ambient temperature, low speed is conducive to the continuity of the refrigerant cycle and improves the system performance. In this system, the initial water temperature of the water tank was 23.1 °C and after 2.5 h it reached 53 °C. The average power generation efficiency is 13.64%, the average thermal efficiency is 26.42%, the overall efficiency is 62.69% and the average COP (coefficient of performance) is 4.87. Compared with traditional PV (photovoltaic) modules, the average temperature reduction is 11.2 ℃. With the increase of solar radiation intensity, the electrical power of the system will increase and the electrical efficiency will decrease. The average daily electrical efficiency of PV/T system is 13.64%, which is 6.25% higher than that of uncooled PV panel. In addition, controlling a proper compressor speed is crucial for enhancing system performance. The PV/T collector can remarkably reduce the temperature of PV panel, improve power generation efficiency and comprehensive utilization efficiency of solar energy.

An Installed Hybrid Direct Expansion Solar Assisted Heat Pump Water Heater to Monitor and Modeled the Energy Factor of a University Students’ Accommodation

This paper focused on the performance monitoring and modeling of a 6.0 kW, 2000 L hybrid direct expansion solar assisted heat pump (DX-SAHP) water heater used for the production of hot water in a university students’ accommodation with 123 females. The data of total electrical energy consumed, volume of hot water consumed, ambient temperature, relative humidity, and solar irradiance were obtained from the data acquisition systems and analyzed in conjunction with the energy factor (EF) of the system. A multiple linear regression model was developed to predict the EF. The EF of the hybrid DX-SAHP water heater was determined from the summation of the coefficient of performance (COP) of the heat pump unit and the solar fraction (SF) of the solar collectors. The operations of the hybrid energy system were analyzed based on three phases (first phase from 00:00–08:00, second phase from 08:30–18:30, and third phase from 19:00–23:30) over 24 h for the entire monitoring period. The average EF of the hybrid energy system per day during the second phase of operation was 4.38, while the SF and COP were 0.697 and 3.683, respectively. The developed multiple linear regression model for the hybrid DX-SAHP water heater accurately predicted the determined EF.

Utilization of Solar Energy for Water Heating Application to Improve Building Energy Efficiency: An Experimental Study

The manuscript is written for flow escalation based on an experimental data for a Solar Assisted Heat Pump Water Heater (SAHPWH) increasing building energy efficiency. For the investigation, a Solar Assisted Heat Pump (SAHP) was conceived, manufactured, and tested in real time. The findings of the experiments shows that single glazing with average sun radiation of 600–750 W/m2, COP of approx. 6 can be obtained with identical heat gains. This study shows that when a flat plate collector of area 1.83 m (L) × 1.22 m (W) × 0.1 m (T) with a 0.5-mm-thick black copper plate absorber with clear glazing as a cover receives average radiation of 700 W/m2, then setup can supply 60 litres of water for residential use from 15 °C to 45 °C in approx. 70 min. In addition, the study finds that the collector efficiency factor F’ is likewise shown to have a direct connection with the absorber and an inverse relationship of tube spacing. The findings indicated that the technology has significant commercial potential, particularly in sectors such as with solar resources for improving building energy efficiency.

Solar Assisted Heat Pump Water Heater Using Photovoltaic-Thermal Collector Evaporator and Its Building Energy Saving Performance

Solar assisted heat pump (SAHP) water heater based on photovoltaic/thermal collector evaporator (PV/T SAHP) can effectively improve the solar energy conversion efficiency by realizing the all-round application of solar energy, PV and photothermal. The heat generated in a PV/T collector evaporator is taken away by the refrigerant and supplied to the heat pump cycle, which can increase the heat pump’s evaporation temperature as well as its performance; meantime, the solar cell’s temperature decreases and the photoelectric conversion efficiency can be enhanced. The performance of PV/T SAHP system is studied theoretically and experimentally, and tested under different conditions. Conventional SAHP and uncooled solar panels are set as the control group. Compared with uncooled solar panels, PV/T SAHP can effectively reduce the temperature of solar cells and improve the photoelectric conversion power. The average error of the numerical simulation model is about 5%, which can meet the needs of engineering application. The optimum installation angle of the collector evaporator in Shanghai is calculated, which is 27°. The annual operation of PV/T SAHP in Shanghai is simulated and predicted. Among them, the average COP is 3.71, the average collecting efficiency is 0.71, and the average comprehensive utilization efficiency of solar energy is 1.04, which can maintain good working performance throughout the year.

Experimental performance analysis of a CO2 direct-expansion solar assisted heat pump water heater

Abstract In the past decades, combined solar energy with heat pump systems has been one of the very widespread ways to improve the efficiency of conventional heat pumps. In that way, this paper presents an experimental analysis of the influence of environmental conditions in a small size DX-SAHP operating with CO2 as refrigeration fluid to heat water. The variation of the water inlet temperature, the solar radiation flux and the relative humidity are analyzed and 88 different experimental results are presented. To support the analysis, a thermographic camera was also used. The results show that the gas cooler outlet pressure and temperature are strongly influenced by the water inlet temperature. As the water inlet temperature increases, the gas cooler outlet pressure and temperature increase, and consequently the COP decreases. The COP decreases in 45.8% for the variation of the water inlet temperature to 15–35 oC. The variation of the solar radiation of 876.9–30.17 W.m-2 presents a reduction of performance in about 30%. For the same conditions for the water heat exchange, the pressure ratio of the cycle decreases with an augment on the solar radiation flux. In addition, the COP is higher in 6% for a change in the mean relative humidity of 31.6–55.8 %.

Environmental benefits and economic feasibility of a photovoltaic assisted heat pump water heater

This work presents a techno-economic study which evaluates the environmental benefits and the economic feasibility of a photovoltaic assisted compact heat pump water heater. The system heats water for domestic consumption in a 190 litres tank. The heat pump is simultaneously powered by the grid and PV panels, although the system was designed to prioritize the PV energy supply. The system does not use batteries and does not feed electricity to the grid.Based on experimental measurements during one year, the study analyses the efficiency of the system for a 4 family members domestic hot water (DHW) consumption. The experimental data shows that the system is friendly to the grid, showing low peak loads and not feeding to the grid.A techno-economic analysis which considers the lifetime cost of the system as well as its environmental benefits has been carried out. The techno-economic analysis shows the benefits of this system when it is compared to: a DHW heat pump without PV, an electrical heater, a boiler and a boiler + solar thermal collectors. The total annualized cost of the system, for a period of 25 years and an electricity price of 0.2 €/kWh, has been quantified at 337 €/year. Furthermore, the system has been found to reduce the non-renewable primary energy consumption by 79% and the CO2 emissions by 82% in comparison with a boiler.Finally, experimental correlations of the system performance are proposed, so that the results of this work can be extended to other locations with similar climates.

Thermodynamic analysis of a direct expansion solar assisted heat pump water heater

In this paper, the thermodynamic performance of a direct expansion solar assisted heat pump (DX-SAHP), which is used to heat domestic water from 20˚C to 45˚C, is theoretically investigated. The system includes a 3m2 single-cover flat plate solar collector, 0.150m3 water tank and 70m tube immersed in the water tank as a condenser. The effect of various parameters such as radiation on the collector surface, compressor speed and the ambient temperature on the coefficient of performance (COP) are calculated. Results show that obtained COP is considerably more than that of a conventional heat pump water heater when radiation on the collector is high. Also, increasing collector area and reducing compressor speed enhance COP. The same occurs when the ambient temperature increases. For instance, at an ambient temperature of 15˚C and 450 w/m2 irradiation on collector surface, the calculated COP was 6.37.

Modeling and validation of refrigerant-based PVT-assisted heat pump water heating (PVTA–HPWH) system

This paper presents a novel model for a refrigerant-based photovoltaic/thermal assisted heat pump water heater (PVTA–HPWH) system, in which PVT evaporator simultaneously provides solar electricity and thermal energy to assist HPWH system. The thermodynamics model for a refrigerant-based PVT device features the direct interaction of PV and thermal energy with environment and HPWH system. Considering the interactive effect of surrounding conditions on PV characteristics, the proposed model can well simulate the reciprocal energy exchange of PVTA–HPWH system with better precision. The model accuracy is validated through experimental measurement with a test rig of integrated PVTA–HPWH system under real climate conditions. The dynamic behaviors of the PVTA–HPWH system are studied by theoretical and experimental analysis. The results reveal good agreements between model simulation and experiment measurement with sufficient confidence.

Thermal Performance Analysis and Optimization of Solar Assisted Heat Pump Water Heater

The main objective of this paper is to analyze the thermal performance of direct expansion solar assisted heat pump DX-SAHP(A) by numerical simulation in MATLAB and comparing it with the thermal performance of DX-SAHP(B) which has an optimized collector area and mass flow rate. Optimization is performed for high exergy efficiency using Particle Swarm Optimization (PSO) and Artificial Bee Colony (ABC) optimization technique. The flat plate collector of solar water heater is used as the evaporator with refrigerant (R22).With the optimized value of mass flow rate as 0.055 kg/sec, width as 0.03 m and diameter of riser tubes as 0.021 m the performance of the optimized system has a maximum COP of 6.85 which is greater than the COP of DX-SAHP(A) and the final water temperature of is obtained 100 minutes earlier in the optimized system i.e. DX-SAHP(B) with compressor work less than the system A

The Heating Coefficient Experimental Analysis of Solar Water-Assisted Low Temperature Air Source Heat Pump System

In winter,Many families use air source heat pump because of the low evaporation temperature of the system, resulting in lower heating efficiency of system. To solve this problem, the low temperature solar assisted hot water was added to the project which is on the basis of air source heat pump, and the system has been tested. After analysis of the collection efficiency of solar collectors at low temperatures and comparative analysis of the temperature cycle, pressure, energy consumption of the low-temperature solar-assisted systems and air source heat pump system, the optimal collector temperature and law of heat pump refrigerant cycle changes of the system were obtained. Theoretically, comparative analysis of low temperature air source heat pumps and solar hot water secondary air source heat pump compression ratio and COP. It gives the key parameters affecting the compression ratio and COP, pointing out ways to improve the heat pump COP. Finally, a key measure to improve the thermal performance of the unit system is proposed, to provide a reference for future practical applications and research. Foreword Air source heat pump in ambient air contains rich low grade solar potential as a source of heat, it has inexhaustible characteristics [1] . The main reason for restricting the use of air source heat pump in northern area of our country is when the outdoor air temperature is low in winter, the outdoor coil frost severe heating efficiency air source heat pump is greatly reduced. Martinez suggested experimental study on the application of solar radiant floor heating systems , solar water temperature is 50-60°C, low efficiency, especially when overcast snow lower system efficiency [2] .In view of the outdoor coil frosting problem, direct expansion solar assisted heat pump water heater system using the proposed by Li Yuwu, from a certain extent alleviated the problem of heat in winter for coil winter fros, improving the heating coefficient and improved the operating characteristics of the unit. However, this system requires the direct absorption of heat in air tube, and the specific heat of air is small, difficult to heat storage, illumination by solar radiation impact, unstable system operation [3]. Based on the above issues, for the low-level office building , the new rural residential , this study presents low temperature solar auxiliary air source heat pump system , the device uses low-temperature solar hot water heat pump system as low , both full use of solar energy , but also eliminates the original system frost problems and improve the efficiency of solar collectors and heat set to improve the evaporation temperature of the evaporator , thereby increasing the compression ratio of the heat pump unit .

Performance study on solar assisted heat pump water heater using CO2 in a transcritical cycle

This study reports the numerical analyses of a CO2 transcritical cycle on solar assisted heat pump water heating system in which evacuated tube U-pipe solar collector is utilized as an evaporator. This simulation model can predict operating characteristics for moderate meteorological conditions of North Dakota. The main purpose of this work is to simulate the overall performance of the heat pump cycle by varying compressor speed. From the analysis the coefficient of performance (COP) value is predicted from 1.5 – 2.8 with three different average solar insolation. The results showed that the performance of the system significantly influenced by the compressor speed and solar irradiation. This study also calculated the instantaneous collector efficiency and found in the range of 50 – 55%.

Experimental performance analysis on a direct-expansion solar-assisted heat pump water heater

A direct expansion solar assisted heat pump water heater (DX-SAHPWH) experimental set-up is introduced and analyzed. This DX-SAHPWH system mainly consists of 4.20 m 2 direct expansion type collector/evaporator, R-22 rotary-type hermetic compressor with rated input power 0.75 kW, 150 L water tank with immersed 60 m serpentine copper coil and external balance type thermostatic expansion valve. The experimental research under typical spring climate in Shanghai showed that the COP of the DX-SAHPWH system can reach 6.61 when the average temperature of 150 L water is heated from 13.4 °C to 50.5 °C in 94 min with average ambient temperature 20.6 °C and average solar radiation intensity 955 W/m 2. And the COP of the DX-SAHPWH system is 3.11 even if at a rainy night with average ambient temperature 17.1 °C. The seasonal average value of the COP and the collector efficiency was measured as 5.25 and 1.08, respectively. Through exergy analysis for each component of the DX-SAHPWH system, it can be calculated that the highest exergy loss occurs in the compressor, followed by collector/evaporator, condenser and expansion valve, respectively. Further more, some methods are suggested to improve the thermal performance of each component and the whole DX-SAHPWH system.

Performance analysis of a solar-assisted heat pump water heater

A modeling and system simulation of an integral-type solar assisted heat pump water heater (ISAHP) was carried out in the present study. The modeling and simulation assumes a quasi-steady process for all the components in the ISAHP except the storage tank. The simulation results for instantaneous performance agreed very well with experiment. The simulation technique was used to analyze the daily performance of an ISAHP for 1 year. It is shown that the daily total COP (COP o) is around 1.7 to 2.5 year around for the ISAHP, depending on seasons and weather conditions. COP o is higher than 2.0 for most of the time in a year and the daily operating time varies from 4 to 8 h. The online adjustment requirement of the expansion valve was also investigated using the present simulation technique. The analysis shows that the expansion device does not need to be controlled online. Using the 1-year simulation results, a universal daily performance correlation of the ISAHP was derived and shown experimentally to be applicable to another design of ISAHP.