Energy and Life Cycle Assessment of Zinc/Water Nanofluid Based Photovoltaic Thermal System

Cooling the PV surface in a Photovoltaic Thermal system is a pivotal operational aspect to be taken into account to achieve optimized values of performance parameters in a Photovoltaic Thermal System.The experimental design used in this study facilitates the flow of varying concentrations of Zn-water nanofluid in serpentine copper tubing installed at the rear of the PV panel thereby preventing the PV surface temperature from increasing beyond the threshold value at which a decrease in electrical efficiency starts to occur.This fusion of solar thermal with PV devices leads to better electrical and thermal efficiency values resulting in decreased cell degradation over time and maximization of the lifespan of the PV module and the energy output from the PV system.Due to the superior thermal heat properties of nanofluids,their usage in such systems has become increasingly widespread.Life cycle metrics which include Energy Payback period,Energy Production Factor and life cycle conversion efficiency were evaluated for the PVT system by exhaustively chalking fundamental parameters such as embodied energy of the PVT setup and the total energy output from the PVT system.This research aims to be a major milestone in the evolutionary journey of Photovoltaic Thermal modules by guiding the engineers working on the theory,design and implementation of PVT systems towards its economic feasibility,environmental impact and energy sustainability.

Performance on Power,Hot and Cold Water Generation of a Hybrid Photovoltaic Thermal Module

This paper proposed a new function of photovoltaic thermal(PVT)module to produce nocturnal cool water not just only generating electrical power and hot water during daytime.Experimental tests were carried out under Chiang Mai tropical climate with a 200 Wp monocrystalline PVT module having dimensions of 1.601 m×0.828 m connected with two water tanks each of 60 L taken for hot and cool water storages.The module was facing south with 18o inclination.The electrical load was a 200 W halogen lamp.From experiments,by taking the module as a nocturnal radiative cooling surface,the cool water temperature in the cool storage tank could be reduced 2℃–3℃each night and the temperature could be reduced from 31.5℃to 22.1℃within 4 consecutive days.The cool water at approximately 23℃was also used to cool down the PVT module from noon when the PVT module temperature was rather high,and then the module temperature immediately dropped around 5℃and approximately 10%increase of electrical power could be achieved.A set of mathematical models was also developed to predict the PVT module temperature and the hot water temperature including the cool water temperature in the storage tanks during daytime and nighttime.The simulated results agreed well with the experimental data.

Design and performance testing of a novel building integrated photovoltaic thermal roofing panel

A novel building integrated photovoltaic thermal(BIPVT)roofing panel has been designed considering both solar energy harvesting efficiency and thermal performance.The thermal system reduces the operating temperature of the cells by means of a hydronic loop integrated into the backside of the panel,thus resulting in maintaining the efficiency of the solar panels at their feasible peak while also harvesting the generated heat for use in the building.The performance of the proposed system has been evaluated using physical experiments by conducting case studies to investigate the energy harvesting efficiency,thermal performance of the panel,and temperature differences of inlet/outlet working liquid with various liquid flow rates.The physical experiments have been simulated by coupling the finite element method(FEM)and finite volume method(FVM)for heat and mass transfer in the operation.Results show that the thermal system successfully reduced the surface temperature of the solar module from 88℃to as low as 55℃.Accordingly,the output power that has been decreased from 14.89 W to 10.69 W can be restored by 30.2%to achieve 13.92 W.On the other hand,the outlet water from this hydronic system reaches 45.4℃which can be used to partially heat domestic water use.Overall,this system provides a versatile framework for the design and optimization of the BIPVT systems.

Performance analysis of a photovoltaic/thermal system with lunar regolith-based thermal storage for the lunar base

Powering a moon base,especially keeping it warm during the long lunar night,is a big challenge.This paper introduces a photovoltaic/thermal(PV/T)system incorporating regolith thermal storage to solve the challenge of power and heat provision for the lunar base simultaneously.The vacuum of space around the moon helps this system by reducing heat loss.During the moon's daytime,the system not only generates electricity but also captures heat.This stored heat in the regolith is then used at night,reducing the amount of equipment we need to send from Earth.The spectrally selective PV/T panels are designed to absorb a wide range of sunlight(0.3–2.5μm)while minimizing heat loss in the infrared range(3–30μm).Simulation results of the hybrid solar energy system indicate the average value of the overall efficiency is 45.9%,which relatively elevates 56.1%compared to the PV system.The launch mass of the proposed PV/T system is only 8.4%of a traditional photovoltaic-lithium battery system with the same amount of energy storage.And the total specific energy of the proposed system is 7.3 kWh kg^(-1),while that of the photovoltaic-lithium battery system is about 0.3 kWh kg^(-1).In summary,this study proposes an alternative combined heat and electricity supply system for the lunar base,which can greatly reduce the launch mass and free up load for other scientific research equipment.

Spectral Selectivity of CdTe Cells with Substrate Configuration for Photovoltaic/Thermal Applications

Existing photovoltaic cells with high infrared emissivity generate huge radiative heat loss in photovoltaic/thermal applications and degrade the photothermal performance.The purpose of this work is to evaluate the full spectral absorptivity of CdTe cells to find a spectrally selective photovoltaic cell for photovoltaic/thermal applications.To this end,the solar absorptivity and mid-infrared thermal emissivity of CdTe cells were tested by ellipsometry,UV-Vis-NIR spectrophotometer,and Fourier transform infrared spectrometer.The experimental results show that the AM 1.5 solar spectrum weighted absorptivity of the substrate configuration CdTe cell reaches 0.91,and the mid-infrared emissivity is only 0.29,while the superstrate configuration cell emissivity is as high as 0.9.Further research shows that substrate configuration with a transparent conductive layer on top can be flexibly grown on metal foils and has spectral selectivity with high solar absorptivity and low mid-infrared emissivity should be considered in the future for photovoltaic/thermal applications.

Performance Assessment and Improvement of Photovoltaic-Thermal System based on Energy, Exergy, Economic and Environment Analysis

A photovoltaic thermal(PV/T)system with parallel cooling channels was designed in this work to decrease the PV panel temperature and improve its photoelectric conversion efficiency.A 4E analysis method(includes energy,exergy,economic,and environmental aspects)was formulated to comprehensively evaluate the performances of the PV/T system,combining experimental and simulation studies.Firstly,the experiment was performed using water as the cooling medium.Results show that the PV/T system can reduce daily CO_(2) emissions by 1682.47-1705.98 g,and compared to the PV system,the added cooling module can increase electrical efficiency and environmental performance by 12.19%and 6.2%,respectively.When the mass flow of water rose from 0.017 kg/s to 0.023 kg/s,the electrical,thermal,and overall efficiencies were improved by 3.82%,11.36%,and 8.27%,respectively.Secondly,a numerical simulation model was constructed based on the experimental results to predict operations of the presented PV/T system using nanofluids as the cooling medium,including Ag,Al_(2)O_(3),and SiO_(2).Simulation results show that the Al_(2)O_(3)-nanofluid-based PV/T system has a higher application value,enabling an electrical efficiency of up to 15.13%.Its thermal efficiency can be enhanced by 5.43%when the volume fraction of Al_(2)O_(3);increases from 1%to 5%.

Experimental evaluation of factors affecting performance of concentrating photovoltaic/thermal system integrated with phase‐change materials(PV/T‐CPCM)

The photovoltaic/thermal(PV/T)system is a promising option for countering energy shortages.To improve the performance of PV/T systems,compound parabolic concentrators(CPCs)and phase-change materials(PCMs)were jointly applied to construct a concentrating photovoltaic/thermal system integrated with phase-change materials(PV/T-CPCM).An open-air environment is used to analyze the effects of different parameters and the intermittent operation strategy on the system performance.The results indicate that the short-circuit current and open-circuit voltage are positively correlated with the solar irradiance,but the open-circuit voltage is negatively correlated with the temperature of the PV modules.When the solar irradiance is 500 W⋅m^(−2) and the temperature of the PV modules is 27.5℃,the short-circuit current and open-circuit voltage are 1.0 A and 44.5 V,respectively.Higher solar irradiance results in higher thermal power,whereas the thermal efficiency is under lower solar irradiance(136.2-167.1 W⋅m^(−2) is twice under higher solar irradiance(272.3-455.7 W⋅m^(−2))).In addition,a higher mass flow rate corresponds to a better cooling effect and greater pump energy consumption.When the mass flow rate increases from 0.01 to 0.02 kg⋅s^(-1),the temperature difference between the inlet and outlet decreases by 1.8℃,and the primary energy-saving efficiency decreases by 0.53%.The intermittent operation of a water pump can reduce the energy consumption of the system,and the combination of liquid cooling with PCMs provides better thermal regulation and energy-saving effects under various conditions.

Improving the Performance of Photovoltaic Power Plants with Determinative Module for the Cooling System

The objective of this work is to analyze and evaluate the impact of cooling systems on photovoltaic modules (for electricity generation), applied at a pilot Testing Facility. The results obtained during this step are used as input in order to determine the best model to be applied at a real-scale Photovoltaic Power Plant (PVPP). This methodology is based on the monitoring and supervision of the operating temperature of commercial photovoltaic modules (PV), both with and without cooling systems, as well as on the study of the water supply design of the cooling system applied on a micro photovoltaic power plant which is connected to the commercial network. Through the analysis of the data, we observed that photovoltaic modules with cooling systems always operate at lower temperatures than the ones without cooling systems. During the testing period, the operating temperatures of the photovoltaic modules without cooling systems were above 60oC (with a maximum temperature equaling 68.06oC), whereas the maximum temperatures registered on the sensors of the model “A” were 43.55oC and 44.75oC, and the ones registered on the sensors of the model “B” were 46.76 and 48.33oC. Therefore, we conclude that the photovoltaic module with the cooling system model “A” is the most suitable for large-scale application, since it was the only model to present temperatures lower than the nominal operating condition temperature (NOCT) of the cell (47oC ± 2oC).

Performance Evaluation of New Two Axes Tracking PV-Thermal Concentrator

The overall problem with PV （photovoltaic） systems is the high cost for the photovoltaic modules. This makes it interesting to concentrate irradiation on the PV-module, thereby reducing the PV area necessary for obtaining the same amount of output power. The tracking capability of two-axes tracking unit driving a new concentrating paraboloid for electric and heat production have been evaluated. The reflecting optics consisting of flat mirrors provides uniform illumination on the absorber which is a good indication for optimised electrical production due to series connection of solar cells. The calculated optical efficiency of the system indicates that about 80% of the incident beam radiation is transferred to the absorber. Simulations of generated electrical and thermal energy from the evaluated photovoltaic thermal （PV/T） collector show the potential of obtaining high total energy efficiency.

Toward an Optimum Design of an Amorphous Silicon Photovoltaic/Thermal System:Simulation and Experiments

Amorphous silicon photovoltaic/thermal(a-Si-PV/T)technology is promising due to the low power temperature coefficient,thin-film property,thermal annealing effect of the solar cells,and high conversion efficiency in summer.The design of a-Si-PV/T system is influenced by a number of thermodynamic,structural,and external parameters.Parametric analysis is useful for a good design of the system.A dynamic distributed parameter model is built and verified in this paper.Outdoor tests are carried out.The impacts of operating temperature,mass flow rate,cover ratio of solar cells,heat transfer area,and frame shadow ratio on its performance are theoretically and experimentally investigated.The results indicate that seven or eight copper tubes are suitable to achieve a high overall efficiency of the a-Si-PV/T system.The frame and tilt angle shall avoid a shadow ratio of more than 8.3%during operation.The difference between power outputs at operating temperatures of 35℃and55℃in the first month is about 0.21%while it drops to less than 0.1%in the twelfth month.Compared with conventional PVT systems,the a-Si-PV/T system benefits from a higher design temperature with a minor efficiency decrement.

Theoretical analyses of the performance of a concentrating photovoltaic/thermal solar system with a mathematical and physical model, entropy generation minimization and entransy theory

In this paper, the performance of a concentrating photovoltaic/thermal solar system is numerically analyzed with a mathematical and physical model. The variations of the electrical efficiency and the thermal efficiency with the operation parameters are calculated. It is found that the electrical efficiency increases at first and then decreases with increasing concentration ratio of the sunlight, while the thermal efficiency acts in an opposite manner. When the velocity of the cooling water increases, the electrical efficiency increases. Considering the solar system, the surface of the sun, the atmosphere and the environment, we can get a coupled energy system, which is analyzed with the entropy generation minimization and the entransy theory. This is the first time that the entransy theory is used to analyze photovoltaic/thermal solar system. When the concentration ratio is fixed, it is found that both the minimum entropy generation rate and the maximum entransy loss rate lead to the maximum electrical output power,while both the minimum entropy generation numbers and the maximum entransy loss coefficient lead to the maximum electrical efficiency. When the concentrated sunlight is not fixed, it is shown that neither smaller entropy generation rate nor larger entransy loss rate corresponds to larger electrical output power. Smaller entropy generation numbers do not result in larger electrical efficiency, either. However, larger entransy loss coefficient still corresponds to larger electrical efficiency.

A review of concentrated photovoltaic-thermal(CPVT) hybrid solar systems with waste heat recovery(WHR)

In conventional photovoltaic(PV) systems, a large portion of solar energy is dissipated as waste heat since the generating efficiency is usually less than 30%. As the dissipated heat can be recovered for various applications, the wasted heat recovery concentrator PV/thermal(WHR CPVT) hybrid systems have been developed. They can provide both electricity and usable heat by combining thermal systems with concentrator PV(CPV) module, which dramatically improves the overall conversion efficiency of solar energy.This paper systematically and comprehensively reviews the research and development of WHR CPVT systems. WHR CPVT systems with innovative design configurations, different theoretical evaluation models and experimental test processes for several implementations are presented in an integrated manner. We aim to provide a global point of view on the research trends, market potential, technical obstacles, and the future work which is required in the development of WHR CPVT technology. Possibly, it will offer a generic guide to the investigators who are interested in the study of WHR CPVT systems.

Optical analysis of a hybrid solar concentrating Photovoltaic /Thermal (CPV/T) system with beam splitting technique

A novel hybrid solar concentrating Photovoltaic/Thermal (CPV/T) system with beam splitting technique is presented. In this system, a beam splitter is used to separate the concentrated solar radiation into two parts: one for the PV power generation and the other for thermal utility. The solar concentrator is a flat Fresnel-type concentrator with glass mirror reflectors. It can concentrate solar radiation onto solar cells with high uniformity, which is beneficial to improving the efficiency of solar cells. The thermal receiver is separated to the solar cells, and therefore, the thermal fluid can be heated to a relatively high temperature and does not affect the performance of solar cells. A dimensionless model was developed for the performance analysis of the concentrating system. The effects of the main parameters on the performance of the concentrator were analyzed. The beam splitter with coating materials Nb2O3 /SiO2 was designed by using the needle optimization technique, which can reflect about 71% of the undesired radiation for silicon cell(1.1m < 3m) to the thermal receiver for thermal utility. The performance of this CPV/T system was also theoretically analyzed.

Numerical study of PV/T-SAHP system

In order to utilize solar energy effectively and to achieve a higher electrical efficiency by limiting the operating temperature of the photovoltaic （PV） panel, a novel photovoltaic/thermal solar-assisted heat pump （PV/T-SAHP） system was proposed and constructed. The hybrid solar system generates electricity and thermal energy simultaneously. A distributed parameters model of the PWT-SAHP system was developed and applied to analyze the system dynamic performance in terms of PV action, photothermal action and Rankine cycle processes. The simulation results indicated that the coefficient of performance （COP） of the proposed PV/T-SAHP can be much better than that of the conventional heat pump. Both PV-efficiency and photothermic efficiency have been improved considerably. The results also showed that the performance of this PV/T-SAHP system was strongly influenced by the evaporator area, tube pitch and tilt angle of the PV/T evaporator, which are the key factors in PV/T-SAHP system optimization and PV/T evaporator design.

Performance Evaluation and Optimization of a Novel System Combining a Photovoltaic/Thermal Subsystem&an Organic Rankine Cycle Driven by Solar Parabolic Trough Collector

A novel coupling system that combines a photovoltaic/thermal(PV/T)subsystem and an Organic Rankine Cycle(ORC)driven by solar parabolic trough collector(PTC)is presented in this paper.The mathematical model is initially built.On the basis,the influence of area ratio of two collectors(PV/T and PTC)on the performance of system is discussed.The results show that the optimal area ratio of PV/T to PTC is 8:2,which can achieve the maximum energy output.Moreover,the performance of the coupling system and two independent systems(PV/T and ORC system)are compared and analyzed.The results show that the coupling system is more reliable and its total output energy(heat and electricity)is the highest,compared with the other two independent systems.The solar energy utilization efficiency of the coupling system is 40%higher than that of the other two independent systems in the steady-state simulation.Moreover,the annual output energy per unit area collector of the coupling system is 13%higher than that of the other two independent systems in the dynamic simulation.Furthermore,in the dynamic simulation of a typical day,the PV panels’temperature of the coupling system is 5℃–7℃ lower than that of the independent PV/T system.It means that the power generation efficiency of PV panels can be increased by 1.5%–3.5%.This study aims to explore the operation characteristics of the novel solar energy utilization coupling system and promote the development of renewable energy utilization models,which provides a reference for the design and optimization of related energy systems.

Electrical and thermal performances of photovoltaic/thermal systems with magnetic nanofluids:A review

Enhancing solar photovoltaic and thermal conversion performances may help develop more environmentally friendly hybrid photovoltaic/thermal(PV/T)systems that can be used in applications ranging from household to industrial scales.Owing to their enhanced thermal and optical properties,nanofluids have proven to be good candidates for designing PV/T systems with superior performances.As smart nanofluids,magnetic nanofluids(MNFs)can further enhance the performances of PV/T systems under external magnetic fields.This paper reviews recent developments in enhancing the electrical and thermal performances of PV/T systems using magnetic nanofluids.Various parameters affecting the performances are highlighted,and some areas for further investigations are discussed.The reviewed literature shows that PV/T systems with MNFs are promising.However,their performances need further investigation before they can be used in applications.

EFFICIENT HEATING AND COOLING SYSTEMS FOR LOW-ENERGY HOUSES

Buildings account for a large amount of land use, energy and water consumption, and atmospheric pollution. For example, in the United States, they use 40% of the total national energy consumption (56% by residential dwellings), produce 38% of the total carbon dioxide emissions, and account for 12.2% of the total quantity of water consumed (2006). In this context, buildings with considerably reduced energy consumption are a key strategy to achieving energy savings and climate protection targets in both the residential and commercial/institutional sectors [1]. This article reviews a number of heating and cooling systems-existing and/or under development- available for residential buildings and briefly outlines some research projects and initiatives, as well as technical achievements in Canada and other developed countries over the last few years.

Numerical study on optical and electric-thermal performance for solar concentrating PV/T air system

Hybrid photovoltaic/thermal(PV/T)system with solar concentrator is an effective way to improve solar energy conversion efficiency.In this work,a single-pass PV/T air system with a three-trough compound parabolic concentrator(CPC)of concentration ratio 2.0 is designed and the solar incident distributions at the solar cell surface are calculated by ray tracing method.Based on energy balance,the heat transfer models of all main components in this system are developed.The effects of some main designing and operational parameters on the electric-thermal performance of the system are analyzed. The results show that the solar radiation intensity can be higher than 1200 W/m 2 at most area of the cell surface.The temperature of the air and cell surface increases along the length of the system.Thus the system efficiency of the CPC is higher than that of the system without the CPC.The thermal efficiency, exergy and electrical efficiency of this CPC system increase with increasing of the air mass flow rate and the length of the system.With increasing packing fraction the electrical efficiency increases,but the thermal efficiency decreases.The exergy efficiency increases slightly with the packing fraction rising.The data obtained in this work are valuable for the design and operation for this kind of solar concentrating PV/T systems.

Comprehensive evaluation and analysis of a nearly zero-energy building heating system using a multi-source heat pump in severe cold region

The integrated application of multi-energy coupled technology in nearly zero-energy building(NZEB)is promising from the perspective of low-carbon development to achieve the goal of net zero energy.PVT(photovoltaic/thermal),air,and ground sources were combined organically to establish an experimental platform of a multi-source heat pump(MSHP)system,which can realize flexible switching of multi-energy sources.The paper presents the analytical hierarchy process and fuzzy comprehensive evaluation method to comprehensively evaluate the five modes of the MSHP system with regard to energy,economic and environmental benefits.The results indicate that the waste heat of the PVT cavity can improve the coefficient of performance of the heat pump unit(COP)by approximately 8.0%.The initial investment in air source heat pump(ASHP)modes is lower than that of a coal-powered system.The ground source heat pump(GSHP)modes have high stability and their payback period is 8.81–10.66 years.The photovoltaic/thermal-dual source heat pump(PVT-DSHP)mode presents the most appropriate system applied in the NZEB in severe cold region,followed by the DSHP,GSHP,ASHP,and PVT-ASHP mode.When compared with other modes,COP,annual saving cost,carbon dioxide emission reduction,and comprehensive value of the PVT-DSHP mode have improved by 7.07%–29.57%,2.21%–23.88%,3.38%–14.83%,and 27.91%–52.62%,respectively.The study provides important insights into the practical application and sustainable development of multi-energy coupled systems in the NZEB in severe cold region.

Performance analysis of solar cell arrays in concentrating light intensity

Performance of concentrating photovoltaic/thermal system is researched by experiment and simulation calculation. The results show that the I-V curve of the GaAs cell array is better than that of crystal silicon solar cell arrays and the exergy produced by 9.51% electrical efficiency of the GaAs solar cell array can reach 68.93% of the photovoltaic/thermal system. So improving the efficiency of solar cell arrays can introduce more exergy and the system value can be upgraded. At the same time, affecting factors of solar cell arrays such as series resistance, temperature and solar irradiance also have been analyzed. The output performance of a solar cell array with lower series resistance is better and the working temperature has a negative impact on the voltage in concentrating light intensity. The output power has a -20 W/V coefficient and so cooling fluid must be used. Both heat energy and electrical power are then obtained with a solar trough concentrating photovoltaic/thermal system.