Photovoltaic Thermal Heat Pump System Research Articles

Research on designated calibration method of fault sensor in photovoltaic thermal heat pump system based on fault detection and virtual calibration

With the increasingly serious global energy problem, clean energy sources such as solar energy have become the mainstream focus of development. Among these, solar Photovoltaic thermal (PVT) heat pump systems have promising prospects. However, incorrect data transmitted by sensors can significantly impact the operation and control of the entire heat pump system, leading to reduced efficiency. Given the specific nature of PVT heat pump systems, their internal sensors are prone to errors during operation. To address these challenges, the Autoencoder Virtual in-situ calibration (AE-VIC) is applied to PVT heat pump systems. Preliminary studies have shown that this method can effectively reduce systematic and random errors in sensors. However, the current AE-VIC method faces certain issues, including unclear calibration targets and inefficient calibration of multiple sensors simultaneously, making it difficult to implement in practical systems. In order to overcome the limitations, fault detection is integrated with AE-VIC. By combining the feature extraction capability of Autoencoder with a Softmax classifier, sensors with faults can be identified before the overall calibration process, making the calibration objective of the AE-VIC more targeted. Following fault detection, inputs of the AE model are optimized using the mRMR algorithm for the identified faulty sensors. This optimization alleviates the difficulty of calibration. Through validation with actual system, the improved method effectively diagnoses and locates faulty sensors, and subsequently calibrates them. After calibration, the sensor system error can be reduced by over 95%. The improved calibration method surpasses the original AE-VIC method in terms of both time and accuracy.

Fault detection and calibration for building energy system using Bayesian inference and sparse autoencoder: A case study in photovoltaic thermal heat pump system

Fault detection and calibration for building energy system using Bayesian inference and sparse autoencoder: A case study in photovoltaic thermal heat pump system

Seasonal performance comparison analysis of the roll-bond photovoltaic thermal heat pump system in a multi-energy generation: An experimental study

Solar photovoltaic thermal heat pump systems contribute significantly to the building industry's goal of energy efficiency and “carbon neutrality” by producing multiple types of energy from the intensive use of solar energy to meet the varied and dispersed energy requirements of modern buildings. An experimental investigation of the roll-bond photovoltaic thermal heat pump system powered by a roll-bond photovoltaic thermal unit is presented in this study, together with the system's precise operating principle and the structural design of the unit. The theoretical underpinnings of experimental research are discussed, including the establishment of test platforms and error analysis, as well as the method for evaluating system performance, which includes solar power, heating, and cooling. Following that, continuous experiment monitoring under various weather conditions in Dalian is carried out throughout the year, which serves as the basis for system performance evaluation and comparison, with a focus on heating, power, and cooling. Comparison analysis results show that the heating and power generation performance in the summer season is the highest, with an average photovoltaic efficiency of 13.6% and an average heating coefficient of performance of 6.16, which is followed by the transition season and winter season, with an average photovoltaic efficiency and heating coefficient of performance of 11.9% and 6.05, 10.2% and 4.54, respectively. However, the performance of power and heating cogeneration in summer conditions fluctuates due to variations in solar radiation intensity. Furthermore, the system can run in cooling mode during the night, on overcast days, and on rainy periods to generate cooling capacity. The cooling performance is the highest during clear nighttime, followed by the overcast nighttime and overcast daytime, with an average cooling coefficient of performance of 2.99, 2.66, and 2.12, separately. Rain, as a cooling water source, significantly improves system cooling performance. The results show that the proposed roll-bond photovoltaic thermal heat pump system can generate high-efficient multi-energy under a variety of weather conditions while remaining stable over time, providing a valuable practical feasibility reference for renewable energy utilization in buildings in northern China.

Operation performance study and prediction of photovoltaic thermal heat pump system engineering in winter

An array arrangement strategy of photovoltaic thermal modules and a connection form of refrigerant pipeline were innovatively proposed by author’s research group. Subsequently, the photovoltaic thermal heat pump system engineering was designed and constructed, and then the performance study of system heating in continuous operation and stage operation in winter was carried out in January 2021. During the system operation, the average coefficient of heating performance of the system was 2.95 in daytime stage operating, 2.55 in nighttime stage operating and 2.07 in continuous operating. To conduct the application simulation of photovoltaic thermal heat pump system, first the prediction model of system heating performance based on back propagation neural network was established and verified according to the operational parameters, then 12 cities of typical climate zone in China were selected to conduct operation simulation and performance prediction to analyze the regional applicability of the system, finally the performance prediction of system heating under variable working conditions was carried out to guide the design calculation of engineering application of photovoltaic thermal heat pump system engineering. It can be concluded that the system was more suitable for engineering application in cities of cold zone and hot summer and cold winter zone than that in severe cold zone. Besides that, the integration and operation optimization of system should be carried out to reduce the average temperature of the circulating hot water tank so that the energy efficiency of hot water system can be improved by 42%.

Study on energy efficiency and economic performance of district heating system of energy saving reconstruction with photovoltaic thermal heat pump

Actively promoting the reconstruction of clean heating is the key direction of the “Planning for clean heating in winter in northern China (2017–2021)”. The photovoltaic thermal heat pump system was introduced in this paper to improve the comprehensive energy efficiency and reduce the operation energy consumption of the heat source system, which provided a new idea for the energy saving reconstruction of clean district heating. In order to verify the feasibility of the energy saving reconstruction by photovoltaic thermal heat pump, following studies were carried out in this paper: First, the integrated energy system engineering based on photovoltaic thermal heat pump was constructed to study the heating performance of the system in winter. Subsequently, the prediction model of heating performance based on back propagation neural network was established and optimized to simulate the heating performance throughout the year. Then, the calculation model of district heating system was established and the evaluation method of system operation energy efficiency and economic performance based on “equivalent electricity consumption of heating” was introduced. Finally, a residential area of Dalian was taking as an example to study the economic performance of energy saving reconstruction of district heating system based on three conventional heat sources by photovoltaic thermal heat pump. The results showed that after the capacity expansion and energy saving reconstruction based on photovoltaic thermal heat pump were conducted, the payback period of energy saving reconstruction investment was 5 years. Besides, with the increase of the configuration ratio of photovoltaic in the system from 1 to 2, the payback period was further shortened to 3 years.

Photovoltaic thermal building skin: effect of condensing and evaporating temperature on flow rate and heat transfer

PurposeThis paper aims to present a numerical study on the natural convection, which operates either as an evaporator or condenser unit of the heat pump system to pre-cool and pre-heat the ambient fresh air.Design/methodology/approachThis study focuses on natural air cooling or heating within the air channel considering the double skin configuration. Particular focus is given to the analysis of airflow and the heat transfer processes in an air channel to cool or heat the ambient fresh air. In this study, the physical model consists of one wall, either heated uniformly or cooled uniformly, whereas the other wall is adiabatic.FindingsThe results show that the variation of both velocity and temperature is observed as the flow transition occurs at the evaporator or condenser wall. In either case, the temperature rises in the range of 6.3–8.4°C with an increase in mass flow rate from 0.07–0.08 kg/s in the photovoltaic thermal condenser part, while in the photovoltaic thermal evaporator part, the change in mass flow rate from 0.048–0.061 kg/s causes a decrease in temperature from 7.1–4.5°C.Practical implicationsThe solar-assisted photovoltaic thermal heat pump system, in building façade having an air layer application, is feasible for pre-heating and pre-cooling the ambient fresh air and also reduces the energy needed to treat the fresh air.Originality/valueThe influence of condensing and evaporating temperature under natural convection mode in double skin conformation is considered for pre-heating and pre-cooling of ambient fresh air.

The detection and correction of various faulty sensors in a photovoltaic thermal heat pump system

Accurate and reliable measurements collected from various physical sensors are of great importance to improve the energy utilization efficiency of solar energy systems. Sensor errors have various significant negative impacts on the automatic control and optimized operation. The current study used the virtual in-situ calibration (VIC) instead of traditional methods to spot possible systematic and random errors of temperature, pressure and mass flowrate sensors in a photovoltaic-thermal heat pump (PVT-HP) system. Seven working conditions were designed to check the robustness and accuracy of the proposed VIC technology. The effects of systematic and random errors on the sensor calibration process and performance estimation of a PVT-HP system were investigated. It’s shown that after calibration the systematic errors of all kinds of sensors were less than 2% and the random errors were also reduced by as much as 74%, significantly reducing the possibility of abnormal data and enhancing the reliability of sensor measurements. The VIC method is very effective to guarantee the thermal performance of PVT-HP system.

Characteristics analysis of the photovoltaic thermal heat pump system on refrigeration mode: An experimental investigation

Photovoltaic thermal heat pump technology stands for the combination of solar heat pump technology and a photovoltaic system, which has the characteristics of tri-generation (heating, cooling, and electricity) to meet the building's energy requirement. In this paper, the dual-use photovoltaic thermal heat pump system was used and investigated experimentally with an emphasis on the refrigeration mode, which with the feature of the novel roll-bond photovoltaic thermal unit working as condenser directly. Moreover, renewable energy such as solar radiation and long-wave radiation are the main energy source of this system. The experimental investigation of the system comprising; 4 roll-bond photovoltaic thermal units, 1 horsepower heat pump unit and 600 L ice storage tank was carried out. The performance evaluation method and uncertainty analysis of the system was proposed and implemented along with the examination on the refrigeration performance and operating characteristics of the system. The results indicate that the proposed photovoltaic thermal heat pump system can achieve the refrigeration for building space cooling demand in summer with high performance and long-term stable operation. This study could provide a valuable reference for the photovoltaic thermal heat pump multi-generation system design and large-scale practical application in northern China.

Experimental investigation on the tri-generation performance of roll-bond photovoltaic thermal heat pump system during summer

Photovoltaic thermal heat pump system has gained much popularity in the recent research field, which generally refers to the integration of photovoltaic and solar assisted heat pump to meet the various building energy demand. In this paper, dual-use roll-bond photovoltaic thermal heat pump system employing new roll-bond photovoltaic thermal unit has been proposed and investigated experimentally. The system operation principles and the design method of the main components are introduced in more details. A mathematical model of each component of the system is developed according to distributed and lumped parameter models. The tri-generation performance evaluation method of the unit and system is also proposed. The experimental investigation on the tri-generation performance of the system is carried out simultaneously, in terms of the heating, cooling and power supply capacity. Through analysis, it is evident that the proposed system has the potential to provide space cooling, hot water, and electricity for buildings with high efficiency and long-term stable working condition. Furthermore, the detailed performance parameters analysis has been carried out. The results demonstrate that the roll-bond photovoltaic thermal heat pump system is practically feasible and has a large potential for building energy conservation.

Hybrid PhotoVoltaic–Thermal heat pump systems: energy and economic performance evaluations in different climates

PhotoVoltaic/Thermal cogeneration (PV/T) aims to utilize the same area both for producing electricity and heat. An electric compression heat pump can be coupled to the PV/T panels to contribute to the space heating demand partially using the self-produced electricity. Some Italian climates and economic incentives scenarios are considered with Trnsys simulations to evaluate the energy and economic viability of PV/T-heat pump hybrid technology. Primary energy saving results to be between 35% and 65%, and discounted payback of the investment can be around 10 years in mild climates and southern resorts.

Advancements in Hybrid Photovoltaic-thermal Systems: Performance Evaluations and Applications

Due to European Directives the electric and thermal energy needs of new and retrofitted buildings have to be satisfied by increasing percentages of renewable energy. Solar energy and heat pumps are the most promising technologies mainly in residential buildings as they have reached great maturity. PhotoVoltaic / Thermal cogeneration (PV/T) aims to utilize the same area both for producing electricity and heat. As solar cells are sensitive to temperature (their efficiency lowers when temperature increases), heat is beneficially collected. This paper provides a description of the applications of the photovoltaic–thermal systems, such as building integrated PV/T, concentrating PV/T systems and photovoltaic–thermal heat pump systems.

Performance evaluations and applications of photovoltaic–thermal collectors and systems

Abstract As a kind of renewable energy, solar energy is paid more and more attention all over the world. Solar energy utilization system can be classified into two categories: thermal systems which convert solar energy to thermal energy, and photovoltaic systems which convert solar energy to electrical energy. Normally, both types of the collectors are used separately. In solar thermal system, the solar thermal energy can be used for heating working fluid via a heat collector. The conventional electrical energy is used to circulate working liquid through the collector. The use of conventional electrical energy can be avoided if combination of both types of thermal collector and photovoltaic collector is hybrid in one unit named photovoltaic–thermal collector (PV/T). In order to fully develop the applications of the photovoltaic–thermal collectors and systems, more researches on performances and characteristics of the photovoltaic–thermal collectors and systems have been carried out. This paper presents the performance evaluations and applications of the photovoltaic–thermal collectors and systems. The performances of the photovoltaic–thermal air collectors and photovoltaic–thermal water collectors are analyzed and discussed. The applications of the photovoltaic–thermal systems, such as building integrated photovoltaic–thermal systems, concentrating photovoltaic–thermal systems and photovoltaic–thermal heat pump systems are presented. Several factors affecting the performances and characteristics of the photovoltaic–thermal systems are also summarized.

Investigation of a Hybrid Photovoltaic Thermal Heat Pump System

The decrease of photovoltaic (PV) cell temperature by 10 °C is expected to improve the PV electrical efficiency by 0.6-0.7% based on the reference efficiency of 15%. Different cooling liquids like air and water have been introduced to pass across the PVs to reduce the cell temperature, and thus increase the electrical efficiency. In this paper, the refrigerant R134a was used as the cooling liquid and a PV/thermal (PV/T) collector was coupled with a heat pump system acting as the evaporator, which was expected to achieve a better cooling effect and energy performance due to its low boiling temperature. A hybrid PV/T collector, made of 6 glass vacuum tube – PV module – aluminum sheet – cooper tube sandwiches connected in series, worked as the evaporator of the heat pump system. Numerical steady models were established for each component of the heat pump system and part of the PV/T collector/evaporator for predicting their energy performance under the weather data of January 14th at Tibet, China. The results showed that the maximum COP could reach up to 7.6. The daily average thermal efficiency and electrical efficiency were 0.764 and 0.104, respectively.