Predictive energy management strategies (PEMS) for fuel cell hybrid electric vehicles (FCHEVs) have shown promise in enhancing safety and energy efficiency. To improve speed prediction accuracy and balance multiple objectives in speed and energy co-optimization, a PEMS based on driving behavior identification is proposed for FCHEVs in car-following scenarios. Firstly, a hybrid model combining support vector machine and recurrent neural network is established to identify driving behavior more accurately. Secondly, considering the strong correlation between driving behavior and speed, a long short-term memory-based model is designed for accurate speed prediction of preceding vehicle. Thirdly, based on prediction results, to achieve a tradeoff among multi-objective, multi-objective cost function with weight factors is established into the model predictive control-based PEMS. Simulation results show the proposed strategy reduces speed variation by 1.55%, equivalent fuel consumption cost by 12.16%, and power source degradation cost by 27.1% compared to baseline models.

Global climate change has raised great attention from governments and prompted a wave of application of lowcarbon heating technologies. However, solar-assisted heat pump, as an attractive technology, has challenges of unstable performance and complex structure and control strategy in practical application. Following the carbonneutral strategy, a novel low-carbon solar-assisted multi-source heat pump heating system (LSMHS) is therefore proposed to improve the application potential of SAHP, which is demonstrated in Hull Central Library by replacing the library's original gas boiler heating system (GBHS). The LSMHS integrates eight novel multithroughout-flowing solar collector arrays with an innovative two-stage heat recovery heat pump which can automatically switch different operation modes according to weather conditions. The practical operation results revealed that the LSMHS maximized the advantages of each component and achieved a high monthly average system COPsys ranging from 2.12 to 2.68 in the three-month demonstration. Eventually, the LSMHS provided a bill saving of 0.73 % with a significant carbon reduction of 63.69 % when compared to the GBHS in practice, achieving an equivalent bill saving of 6.7 pound for every tone of carbon reduction. The remarkable demonstration results showcased the application potential of the novel LSMHS and gave valuable guidance for low-carbon building heating.

Building energy modelling (BEM) is crucial for achieving energy conservation in buildings, but occupant energy-related behaviour is often oversimplified in traditional engineering simulation methods and thus causes a significant deviation between energy prediction and actual consumption. Moreover, the conventional fixed schedule-setting method is not applicable to the recently developed data-driven BEM which requires a more flexible and data-related multi-timescales schedule-setting method to boost its performance. In this paper, a data-based schedule setting method is developed by applying K-medoid clustering with Principal Component Analysis (PCA) dimensional reduction and Dynamic Time Warping (DTW) distance measurement to a comprehensive building energy historical dataset, partitioning the data into three different time scales to explore energy usage profile patterns. The Year–Month data were partitioned into two clusters; the Week–Day data were partitioned into three clusters; the Day–Hour data were partitioned into two clusters, and the schedule-setting matrix was developed based on the clustering result. We have compared the performance of the proposed data-driven schedule-setting matrix with default settings and calendar data using a single-layer neural network (NN) model. The findings show that for the data-driven predictive BEM, the clustering results-based data-driven schedule setting performs significantly better than the conventional fixed schedule setting (with a 25.7% improvement) and is more advantageous than the calendar data (with a 9.2% improvement). In conclusion, this study demonstrates that a data-related multi-timescales schedule matrix setting method based on cluster results of building energy profiles can be more suitable for data-driven BEM establishment and can improve the data-driven BEMs performance.

Previous studies on the photovoltaic-thermoelectric (PV-TE) system have focused on its daytime performance, that is, photovoltaic (PV) and thermoelectric generators (TE) only output electricity by day. Consequently, in this paper, a PV-TE system with micro-channel heat pipe (MCHP) and phase change material (PCM) (the PV-MCHPTE system with PCM) is proposed, and the performance change of the system in 24 h is investigated, which is not involved in earlier researches. Where, PCM on one hand reduces the operating temperature so improves the PV performance in the daytime, and on the other, releases the stored heat to TE at night, which offers a prerequisite for TE to generate power in the nighttime. The mathematical model of the novel system is given out, and its allday performance is compared with the system without PCM. Theoretical investigations find that PCM improves the overall electrical performance, both in the daytime and the nighttime, with their all-day total outputs of 2.67 x 103 kJ and 2.64 x 103 kJ, respectively, under certain conditions. Additionally, the performance of the two systems under different parameters is further explored, which points out the direction for the following research and also provides valued references for the implementation of integration to PV and TE.

A concentrated photovoltaic/thermal system employing micro-channel heat pipes and thermoelectric generators is constructed. Photovoltaic cells and thermoelectric generators are used to generate power, and the heat is gained by the circulating water. The feasibility of the system is demonstrated by the experimental work which compensates for the lacked experimental content in our previous paper and validates the correctness of the established mathematical model. Additionally, using the validated model, the influence of the addition of a glass cover and the volume of the water tank is investigated by simulation discussion, and the annual prediction is conducted. The results indicate that, during the 4-h actual operation, the electrical power of thermoelectric generators first increases and then decreases with the average value of 8.33 W, effectively improving the average electrical efficiency of the system from 7.62% to 8.95%. Also, the water tank temperature is incremented from 32.89 degrees C to 45.28 degrees C. The addition of a glass cover increases the heat gain but reduces the total electrical output because of the weakened PV performance. The large-volume water tank detracts from the final temperature but is helpful to the electricity. Therefore, it needs to compromise in respect of either great electrical performance or thermal performance.

The concentric double-tube heat exchanger (CDTHE) proposed in our previous work addresses the limitations of the combined application of conventional loop thermosyphon photovoltaic/thermal (LT-PV/T) systems. Based on this, a novel non-concentric multi-tube heat exchanger (NMTHE) as the condenser of the LT-PV/T system was proposed in this paper, which improves the performance of system by reducing the flow resistance of the working fluid. Experimental platform was built to explore the performance difference between CDTHE-LT-PV/T and NMTHE-LT-PV/T system. Experimental results show that compared with the CDTHE-LT-PV/T system, the thermal efficiency, the electrical efficiency, the primary energy-saving efficiency and the exergy efficiency of NMTHE-LT-PV/T system relatively increase by 17.76%, 2.1%, 10.05% and 3.64%. Mathematical models for two systems are established and verified. Then the performance of the two systems under different solar radiation and ambient temperature is explored. Besides, the all-day performance of the two systems on typical winter days in four cities at different latitudes is predicted. The results show that the NMTHE-LT-PV/T has more prominent advantages in northern China at higher latitude. Furthermore, the influences of some structural parameters and operating setup on the performance of NMTHE-LT-PV/T system are discussed.

Traditional dual-source heat pumps are generally composed of separated flat PV evaporators and finned-tube evaporators connected in series or parallel, occupying too much extra space with low space/energy utiliza-tion. The heat pump system consisting of fins and low concentrated photovoltaic designed in this paper could obviously improve PV output and it brilliantly fixes the finned-tube structure under the concentrator. The compact structure could better exploit the three-dimensional space and energy, bring improvement of the comprehensive output and system performance. The experimental rig is built in Hefei, China with improved pipeline. The system shows a brilliant cooling effect on concentrated photovoltaics, lowering the temperature by about 50 degrees C, lifting the electrical efficiency by 4.6%. Interestingly, in the real outdoor environment, the effi-ciency of concentrated photovoltaics declines with the deteriorated irradiance (cloud cover), contrary to the traditional flat PV. On a sunny day, the average electrical efficiency, heating rate, power consumption, COPth, and COPPVT could be 14.4%, 2168 W, 592 W, 3.76, and 4.43 respectively. The impact of the mass injection and concentration ratio is also investigated mathematically. This article makes up the lacked experimental content, providing strong and reliable data support/reference for the actual design and performance prediction of the high-efficiency and low-carbon three-dimensional heat pump system.

Heat pumps (HPs) are energy-efficient space heating devices that are key to global carbon reduction and carbon neutrality. However, current commercial HPs have performance issues in cold climates where space heating is needed most, including low COP and high energy consumption of defrosting. Aiming to tackle these issues, a novel two-stage heat recovery heat pump (THRHP) is therefore developed to enable heat recovery from exhaust air for improving COP and preventing dramatic energy use during winter defrosting. The performance of THRHP was optimized in the laboratory by investigating its expansion valve opening and exhaust air fans situation. Finally, the experiment results showed the prototype provided a heating capacity of 32.3 kW, generating 4 m3/h hot water of 55 degrees C with COP of 2.57 at outdoor temperature of 0 degrees C, achieving 20.1% higher COP than the commercial HPs, while the efficient and quick defrosting process only consumed 0.46 kW and 4 mins under outdoor temperature on-6 degrees C. The results gave more insights into the characteristics of THRHP and obtained the optimal control strategies of THRHP for better performance, thus promoting the wide deployment of HPs and achieving the ambitious carbon-neutrality targets.

Regarding the existing research on photovoltaic (PV) and thermoelectric generator (TE) integrated systems mostly focus on their daytime behaviors, a solar system that can achieve continuous electrical supply throughout the day, namely the PV-TE system with the micro-channel heat pipe (MCHP) (the PV-MCHP-TE system), is proposed in this paper. The implementation method is to use the phase change material (PCM) which releases the heat it harvests during the day to maintain the uninterrupted electrical output of TE at night, on the basis of the system generating electricity through PV and TE by day. Considering that the system performance may change with the difference in cooling effects, three PV-MCHP-TE systems adopting different cooling methods are designed and their performance changes during a continuous working week are analyzed. The results show that the daytime average electrical efficiencies of PV in the systems using free cooling, forced air cooling, and water cooling are 9.33%, 11.85%, and 13.10%. The maximum electrical efficiencies of TE in the three systems are 0.47%, 1.48%, and 1.87%, and the nighttime average efficiencies are 0.13%, 0.15%, and 0.16%, respectively. Additionally, a comparative analysis is also performed to compare the performance of the considered systems under different PCM parameters.

As is well known, traditional solar systems can only work under conditions of solar radiation, as solar energy is the sole energy source for photovoltaic generation and heat recovery. Few studies have focused on their continuous operation throughout the day and this research gap needs to be filled. Consequently, to pursue a round-the-clock electrical power generator, in this study, a two-stage system is constructed, consisting of the first-stage photovoltaic/thermal module and the second-stage solar thermal collector with thermoelectric gen- erators in series. Thermoelectric generators ensure that the system runs normally by day, while also utilizing the heated fluid to achieve uninterrupted energy output at night. A numerical model of the system is developed to analyze the performance changes under continuous running. From the results, the second-stage module improves the daytime heat gain, effectively boosting the electrical contribution of thermoelectric generators, whether during the day or night. At the maximum input energy, photovoltaic cells generate the greatest power of 118.37 W with an average efficiency of 14.56%. The average efficiencies of thermoelectric generators in the daytime and nighttime are 0.97% and 0.53%, enhancing the total electrical output. Additionally, the comparative analysis is performed under different parameters, as well as an economic analysis.

This study presents a detailed performance analysis of a novel concentrated system which consists of a photovoltaic/thermal (PV/T) module with phase change material (PCM) and a solar thermal (ST) collector with thermoelectric generators (TEG) connected in series. While considerable electrical energy is acquisitive, enhanced high-temperature thermal energy is also achieved. In this system, the PV/T module generates both photoelectric power generation and low-temperature thermal energy, and the secondary heated water and the secondary thermoelectric output are obtained through the ST module and TEG on ST. Theoretical investigations find that, the system of the PV/T module and the ST module in series (PV/TST) performs well in terms of thermal performance and comprehensive performance. During the all-day operation, compared with the PV/T-PV/T system, the final temperature of the water tank in the PV/T-ST system is about 5 degrees C higher. Also, the electrical efficiency and the thermal efficiency are 10.65% and 65.22% respectively at 12:30 when using the 1.1-m2 Fresnel lens. Where, TEG converts some thermal energy into electrical energy, increasing the amount of high-grade energy of the system by about 321.53 kJ in the daytime. Additionally, the discussion from different perspectives on the impact of different parameters is also carried out.

Conventional building energy models (BEM) for heating and cooling energy-consumption prediction without calibration are not accurate, and the commonly used manual calibration method requires the high expertise of modelers. Bayesian calibration (BC) is a novel method with great potential in BEM, and there are many successful applications for unknown-parameters calibrating and retrofitting analysis. However, there is still a lack of study on prediction model calibration. There are two main challenges in developing a calibrated prediction model: (1) poor generalization ability; (2) lack of data availability. To tackle these challenges and create an energy prediction model for office buildings in Guangdong, China, this paper characterizes and validates the BC method to calibrate a quasi-dynamic BEM with a comprehensive database including geometry information for various office buildings. Then, a case study analyzes the effectiveness and performance of the calibrated prediction model. The results show that BC effectively and accurately calibrates quasi-dynamic BEM for prediction purposes. The calibrated model accuracy (monthly CV(RMSE) of 0.59% and hourly CV(RMSE) of 19.35%) meets the requirement of ASHRAE Guideline 14. With the calibrated prediction model, this paper provides a new way to improve the data quality and integrity of existing building energy databases and will further benefit usability.

Thermoelectric generators are proposed to be applied to the heat pumps to further improve the electrical output of the system. Some mathematical analyses have been carried out, but the related experimental exploration is lacked. In this paper, a photovoltaic heat pump with two condensers: a micro-channel heat pipe/thermoelectric generator (MCHP/TEG) condenser and a submerged coil condenser, was built and tested under different weather conditions. Results show that the water temperature rises with running time, leading to the decrease in heat capacity and coefficient of performance (COPth: only consider the heat; COPPVT: consider both electricity and heat). On 29th May, the average photovoltaic output, condensing heat, COPth, and COPPVT are 358 W, 3373 W, 3.96, and 5.08, which are improved to 485 W, 3705 W, 4.32, and 5.80 by the better irradiation condition on 30th May, but the average electrical efficiency is decreased from 16.63% to 15.65%. The TEG output is also higher under better irradiance. However, due to the poor performance of the commercial TEG, the TEG output in the experiment is low. With better parameters or a larger photovoltaic evaporating area, the TEG output and system performance could be enhanced. This article is also a supplement and improvement to several previously published articles in terms of experiments and verification. (c) 2021 Elsevier Ltd. All rights reserved.

The concentrated hybrid power/thermal system is proposed and discussed in this paper. This system, which includes the concentrator, the solar thermal collector, and thermoelectric generators, not only provides the heated fluid but also can generate electrical power by thermoelectric generators, thus, two energy conversions are realized: heat recovery and thermoelectric power generation. Theoretical investigations found that the variation trends of heat gain and electrical power of the system have a good correlation with solar radiation. During the all-day operation, the thermal and electrical performance of the concentrated hybrid power/thermal system using linear Fresnel lens is better than that of the compound parabolic concentrating power/thermal system with the all-day overall efficiency of the former of 75.59%, 5.12% higher than the latter. Also, the electrical power thermoelectric generators generate in the two systems with the maximum of 0.60 W and 0.54 W under the conditions of 4 concentration ratio and 15 celcius initial water temperature, respectively. Additionally, the performance of the system from both viewpoints of energy and exergy analysis is investigated under conditions of different parameters of thermoelectric generators, concentration ratios, and fluid properties. The valuable conclusions provide a new thought for the application of TEG in solar systems.

The investigation on the impact of various factors of thermoelectric generator (TEG) & structure on the performance of TEG & system was carried out in this paper, which is essential to improve the system performance, optimize the system design, and match better TEG parameter. Results represent that a larger figure of merit Z (or Z (T) over bar) may still lead to a reduction in system performance. When Z = 0.0016, the TEG conversion efficiency is 2.96% which is higher than 1.31% in the system with Z = 0.0028 under 800 W/m(2) because the output is influenced by not only Z (orZ (T) over bar) but also Delta T/T-h. The COPPVT and exergy efficiency of the system with Z = 0.0016 could be 7.35 and 29.18% which are lower than 7.52 and 29.77% in the system with Z = 0.0012. The exact influence of each parameter of Z is also explored. The TEG efficiency decreases from 2.05% to 0.83% with the rise of lambda while the PV efficiency increases from 26.48% to 27.55%, but the COPPVT is changeless at 7.54. However, on the total performance, s and sigma have more significant effects than l. Running for 822 min with real environmental conditions, the average electrical efficiency and COPPVT could reach 28.10% and 6.84. (C) 2021 Elsevier Ltd. All rights reserved.

To improve space/energy utilization and meet various households' needs, a high efficient and multifunction concentrated solar-air heat pump system(MC-SA-HP) is proposed in this paper. The concentrator is used to lift the energy density and unit generation of photovoltaic panel, and its three-dimensional feature could realize the layered utilization of space by placing the air source evaporator in the spare part below. By different operating strategies, the system could provide heating, electricity, and cooling. Through testing, MC-SA-HP obtained mean electrical generation and efficiency of 146W and 14.6%, condensing heat of 2114W, COPth and COPPVT of 3.7 and 4.4. Compared with the system using flat-panel photovoltaic, it could improve the electrical generation by 71.8%, heating capacity by 5.9%, total output by 12.6%, overall efficiency of 9.5%, COPPVT by 7.3%, and exergy efficiency of 36.1%. In the cooling mode during experiment, the water temperature drops from 14.6 to 2.6 C, generating 1.51 x 10(7) J cooling capacity, and an average COPc of 2.3. The multifunction feature increases the attractiveness and feasibility of this novel system. After calculation, the high-efficient and compact MC-SA-HP system shows great effect on cost and emission reduction, which could help to better cope with climate change and achieve the goal of carbon peak and carbon neutrality.

The utilization potentiality of PV/T which laminates PV onto glass cover to improve reliability (G-PV/T) was proved previously, but how to optimize the structure is not comprehensive. This study focuses on its optimization and energy trade-off among two critical structural parameters (i.e., packing factor, air gap thickness). Firstly, mathematical models for G-PV/T are established and validated by the experimental data. Specifically, a special G-PV/T without air gap is also considered, and where its' difference in optical models and heat transfer models are stated. Secondly, the past studies of PV/T used to investigate parametric optimization by discussing only one parameter at a time, but this study points out that the optimization methods for these structural parameters are interrelated, and their coupling relationship is influenced by outside conditions. So a matrix of the two parameters is used to predict the daily performance of G-PV/T and the results are presented in three-dimensional two-independent-variables plots, evaluated by the first and second laws of thermodynamics. Suggestions are given for structural optimization depending on application requirements and energy trade-off. Thirdly, performance under three important outside conditions is predicted to discuss how the system performance is influenced and how the coupling relationship of the two critical parameters moves.

Dislike the electrical performance, the heat collection capacity is always disappointing in the photovoltaic evaporators. It is always handled by adding additional finned-tube evaporators, which will increase space occupation and pipeline complexity. In this paper, a novel direct-expansion heat pump based on linear Fresnel photovoltaic/fin evaporator is designed. By integrating concentrating photovoltaic and fins into one composite photovoltaic-air evaporator, the above shortcomings can be solved and the solar & air energy can be fully utilized to maximize the output of the evaporator with a limited area. Compared with the direct-expansion heat pump with compound parabolic concentrator/fin evaporator, this system owns a higher concentration ratio, smaller photovoltaic area (making it possible to be equipped with GaAs cells), and larger firmed-tube structure to enhance the heat capacity under the same receiving area. Dynamic models are established in MATLAB and comparative analysis is carried out under different wind speeds, irradiance, and ambient temperature. The influence of running time and the system performance with 40 degrees C water temperature (in actual application) are also discussed. The average electrical efficiency, COPPVT, and exergy efficiency of the heat pump system based on linear Fresnel photovoltaic/fin evaporator could be 28.21%, 3.55, and 27.07% under 900 W/m(2), which are all higher than 16.02%, 3.15, and 20.09% in the system with compound parabolic concentrator/fin evaporator. Therefore, the newly designed system could enhance the performance of the hybrid system.

The condensers of loop thermosyphon PV/T systems (LT-PV/T) are usually integrated inside water tanks, which may bring some challenges during combination use. This research innovatively proposed a concentric copper tube heat exchanger as the condenser, which is combined with a copper tube evaporator beneath the absorber. The gaseous working fluid flows in the inner tube and the cooling water flows in the outer tube. Since ordinary water pipes are used for water circulating between the outer tube and water tank, this LT-PV/T collector can be used individually or combined with other collectors flexibly. To access its' performance, researches have been conducted: (1) Designing and fabricating the system prototypes; (2) Investigating system performance with different volume-filling ratios (26.5%, 34.8%, 43.2%); (3) Investigating the influences of working fluid (water, ethanol and R134A). (4) Evaluating the systems’ performance with energy efficiency, exergy efficiency, and semi-empirical system efficiency models; (5) Conducting two case studies in South China (an individual collector & a 4 parallelly/serially-combined LT-PV/T collectors system). The system is first-of-its-kind and has obvious advantages in reliability, flexibility, space-saving and large-scale applications. The typical primary energy-saving efficiency of the LT-PV/T with R134a of 40% filling ratio can reach 78.0%, higher than the published LT-PV/T systems.

The main problem of concentrated photovoltaics is the high temperature caused by high radiance, which deteriorates the electrical efficiency and service life of photovoltaic cells. Most concentrated photovoltaics are assembled into the photovoltaic/thermal systems and cooled by water. However, if concentrating photovoltaics is combined with an evaporator in a direct-expansion solar-assisted heat pump, the photovoltaic damages (reduced life span and conversion efficiency of photovoltaic cells) caused by the high temperature in concentrators will be much better alleviated. But at present, there is little research on the combination of concentrating photovoltaic and direct-expansion solar-assisted heat pump. To enrich the relevant content and explore the optimal concentrating method combined with heat pumps, three hybrid heat pumps with different concentrating evaporators are proposed and investigated. Results indicate that in the photovoltaic heat pump system based on Fresnel concentrator, photovoltaic heat pump system based on compound parabolic concentrator, and the photovoltaic heat pump system based on 3-D crossed compound parabolic concentrator, the electrical efficiency could achieve 30.31%, 15.37%, and 11.66% under 300 W/m(2). The coefficient of performance (considering both electricity and heat) could reach 7.65, 5.67, and 5.45 under 800 W/m(2), meanwhile, the 29.87%, 16.25%, and 13.66% exergy efficiency can be obtained under the same irradiation. Therefore, the photovoltaic heat pump system based on Fresnel concentrator has the best capacity, followed by the system based on compound parabolic concentrator and 3-D crossed compound parabolic concentrator. Besides, in the FPV-SAHP system, two concentration ratios are designed and discussed. And the effect of ambient temperature, water temperature, as well as solar irradiance on the systems is also explored. (C) 2021 Elsevier B.V. All rights reserved.