Photovoltaic Thermal Collector System Research Articles

Two novel dual-tube photovoltaic-thermal collector designs with improved performance for liquid-cooled photovoltaic-thermal systems

Photovoltaic-thermal (PVT) collectors developed over the years have achieved reduced photovoltaic (PV) panel temperature and improved electrical efficiency mostly based on single-tube spiral and serpentine configurations of the cooling pipes. However, the design and analysis of PVT collector configurations incorporating multiple serpentine tubes, capable of simultaneously reducing both the average PV panel temperature and temperature non-uniformity within the panel, are rare. The present work introduces two novel designs PVT collector systems by incorporating dual-tube arrangements, namely, the Dual-Tube Uni-Directional (DTUD) and the Dual-Tube Opposite-Directional (DTOD) systems. The new collectors' performance is numerically analysed through three-dimensional (3D) simulations. The highest net powers are obtained with 32 cooling loops in both the DTUD and DTOD designs for the given flow rate and panel area. The DTUD-based PVT system yields up to 10.39 % and 10.36 % gains in electrical efficiency and net power, respectively. On the contrary, the DTOD system also results in gains of these parameters, albeit marginally less than the DTUD arrangement. However, the DTOD arrangement results in reduced maximum PV panel temperature, which can positively impact the panel's life span.

Identification of a different design of a photovoltaic thermal collector based on fuzzy logic control and the ARMAX model

This study investigates the effects of absorber design on the performance of a water-based photovoltaic thermal collector (PVT). In this regard, three different absorber designs with the same pipe diameter and length were tested and compared experimentally in Cairo, Egypt, during summer 2021. Furthermore, artificial intelligence techniques were used to create a model to identify the PVT system and define the input–output relationship in state space representation. This is to get a more thorough understanding and deeper evaluation of the PVT performance with various absorber designs to achieve the best possible system performance under varied operating situations and weather. The fuzzy logic control is examined by Autoregression Moving Average using an external input model (ARMAX), which relies on the autoregression moving average to achieve system performance. According to the study's findings, at a maximum water flow rate of 3 L/min, the proposed PVT system can convert solar energy with an overall efficiency of 69.6 %, 64.6 %, and 63.5 %, respectively, with a pressure loss of about 29.5 kPa, 29.33 kPa, and 24.79 kPa for absorbers A, B, and C. Furthermore, the challenging suggested fuzzy control system for the PVT system provides knowledge to comprehend the system complexity since the connection is formed by connecting 5 inputs with 3 outputs through its representation in the state space representation.

Design and performance optimization of a novel zigzag channeled solar photovoltaic thermal system: Numerical investigation and parametric analysis

In order to overcome the drawbacks of traditional photovoltaic thermal systems, including their limited thermal power, low thermal exergy, and heat transfer fluid outlet temperature, it becomes essential to explore the optimal design configuration of the system for maximization both electricity and domestic hot water generation. Therefore, a detailed numerical modeling and comparative performance analysis on a solar photovoltaic thermal collector (PVT) are conducted under two novel structures of the cooling channels. The first system is a reference PVT collector with a classical straight zigzag-plated tube cooling channel (Case A), while the second PVT system proposes an innovative design of flow cooling channel which is divided into three equal zigzag-plated tube sections (Case B). Each section is also split into three double pass tubes and has a separate inlet and outlet in a staggered manner corresponding to the section that precedes and follows it. The two proposed PVT structures are investigated through computational fluid dynamic simulation under solar radiation values ranging from 200 to 1000 W/m2 and coolant flow rates varying between 0.001 and 0.005 kg/s using both water and air as coolant. The obtained results confirm the significant potential of the modified configuration (Case B) that yielded an improvement in the thermal efficiency by 7.23% and 15.75% for water-PVT and air-PVT system, respectively, over the reference PVT system (Case A). Also, the modified configuration (Case B) yielded an enhancement in the electrical efficiency by 4.0% and 4.6% for water-PVT and air-PVT systems, respectively. It can be concluded that dividing the cooling channel area into equally mini zigzag plate tube-shaped sections with multiple reciprocal entrances is regarded a feasible configuration for augmenting the performance of PVT collectors and maintaining a uniform coolant flow and reduced temperature distribution over the entire panel.

Improvement of the photovoltaic panel cooling by natural air ventilation

AbstractThe operating temperature increase in solar photovoltaic modules is a major problem, which affects their performance negatively. This numerical study introduces the effect of natural convection air‐cooling on the performance a novel hybrid photovoltaic/thermal collector. The standard k‐ε turbulence model is implemented for describing the turbulent natural convection. For improving the heat transfer rate of a novel photovoltaic/thermal collector system (PV/T), a sloped entrance channel (SEC) and an aluminum flat plate (AFP) were installed. The effects of SEC geometry parameters, the number of AFP and their distance to the photovoltaic module (PV) on the average Nusselt number are investigated. In addition, the effect of the PV/T system tilt angle and Rayleigh number on the thermo‐hydrodynamic flow behavior has been discussed. The results indicated that the heat transfer rate of the new hybrid PV/T system was improved by up to 20%, compared to the reference case without an aluminum flat plate. In addition, increasing the tilt angle of the PV/T system boosts airflow velocity, particularly for high Rayleigh number values (with and without AFP). Furthermore, several correlations, as functions of Rayleigh numbers and inlet channel dimensions, have been developed to predict the average Nusselt number.

Experimental analysis of photovoltaic thermal collector (PVT) with nano PCM and micro-fins tube counterclockwise twisted tape nanofluid

A hybrid PVT (photovoltaic thermal system) nanofluid circulation system was tested, which included a micro-fin tube (inner grooved) and twisted tape with nano PCM (phase change material). The use of nanoparticles allowed the nano PCM and nanofluid to have higher thermal conductivities, improving their performance. Experiments were carried out within a controlled environment by utilizing an indoor solar simulator with a solar irradiance level of 800W/m2. The PVT system used water/SiC (0.6, 0.3) vol% nanofluid as a working fluid. The nanoPCM comprises 1% SiC nanoparticles, which enhance thermal, electrical (photovoltaic), and photovoltaic thermal efficiency (total efficiency). The mass flow rate range is 0.008–0.058 kg/s. The energy analysis showed that the PVT had an electrical efficiency of 10.8%. The system's maximum thermal efficacy was 83.3% for the PVT with the T (twisted tape), MF (micro-fins), NF (nanofluids), and NPCM (Nano PCM). The percentage of improved electrical power compared between the bare PV and the PVT NF T NF NPCM was 44.5%. The micro fin tube with twisted tape improved the heat transfer properties for enhanced thermal performance.

Experimental analysis for the photovoltaic thermal collector (PVT) with nano PCM and micro-fins tube nanofluid

The efficiency of the photovoltaic cell ultimately decreases as its temperature rises. A hybrid PVT (photovoltaic thermal system) is one of the innovative techniques employed to increase that efficiency. This study utilized a cooling nanofluid circulation system with a micro fin tube (inner grooved) encapsulated with nano PCM (Phase Change Material). The utilization of nanoparticles allowed nano PCM and Nanofluid to have higher thermal conductivities increasing efficiencies. Experiments were conducted in a controlled environment using an indoor solar simulator. Water and nanofluid with 0.6 vol% SiC were used as working fluids in the PVT system. The nano PCM contains 1% SiC nanoparticles, which improves electrical (photovoltaic), thermal, and photovoltaic thermal efficiencies (total efficiencies). The mass flow rate ranges from (0.008–0.058 kg/s. The energy analysis indicated that the PVT had an electrical efficiency of 9.6%. The system’s highest thermal efficiency was 77.5% for the PVT M.F.N.F.N.PCM where the M.F (micro-fins), N.F (nanofluids), and N.PCM (nanoPCM).

The application of TiO2 nanofluids in photovoltaic thermal collector systems

Solar energy may be transformed into several types of energy, including electrical energy. Solar cell efficiency is low because some of the thermal energy that solar panels collect is not used. A solar panel’s relative efficiency and heat transmission decrease as it heats up. By collecting thermal energy and cooling it, photovoltaic systems may operate more efficiently. In this study, a thermal photovoltaic collector (PVT) system with a working fluid is used to cool PV panels. Laboratory-scale testing and simulation using the ANSYS Software were applied in the analysis. The simulation outcomes confirm the experimental values. Nanofluid serves as the working fluid because it has strong heat transmission qualities and has the characteristics of titanium dioxide (TiO 2). Average PV operating temperatures may be reduced by using TiO 2-based PVT systems. This can be explained by the fact that the fluid makes it easier for heat to be transferred. In comparison to PV-ground cells, photovoltaic solar cells now have a 2.11% higher efficiency. When utilizing TiO 2-based PVT systems, an average photovoltaic temperature of 58.5 °C is generated, with a 13.04% photovoltaic efficiency.

Developing an Advanced PVT System for Sustainable Domestic Hot Water Supply

Energy consumption is steadily increasing with the ever-growing population, leading to a rise in global warming. Building energy consumption is one of the major sources of global warming, which can be controlled with renewable energy installations. This paper deals with an advanced evacuated hybrid solar photovoltaic–thermal collector (PVT) for simultaneous production of electricity and domestic hot water (DHW) with lower carbon emissions. Most PVT projects focus on increasing electricity production by cooling the photovoltaic (PV). However, in this research, increasing thermal efficiency is investigated through vacuum glass tube encapsulation. The required area for conventional unglazed PVT systems varies between 1.6–2 times of solar thermal collectors for similar thermal output. In the case of encapsulation, the required area can decrease by minimizing convective losses from the system. Surprisingly, the electrical efficiency was not decreased by encapsulating the PVT system. The performance of evacuated PVT is compared to glazed and unglazed PVTs, and the result shows a 40% increase in thermal performance with the proposed system. All three systems are simulated in ANSYS 18.1 (Canonsburg, PA, USA) at different mass flow rates and solar irradiance.

Analysis of energy, exergy, environmental and economics (4E) on photovoltaic-thermal collector system

In this paper, a novel thermal absorber based photovoltaic-thermal system is presented. The thermal absorber is attached at the rear surface of photovoltaic, and water is re-circulated to extract heat. The outdoor experimentations are performed at Pune, India (18.7611? N, 73.5572?) on clear sky day, and water temperatures, surface temperature, radiation and flow rate are measured to analyse techno-economical performance at different operating conditions. The surface temperature of the photovoltaic module plummeted from 54.65?C to 47.9?C with the incorporation of a thermal absorber with flipside water cooling at a ranging flow rate of 0.03 to 0.06 kg per seconds. The result shows an average enhancement of 4.2 % in the electrical power output of the photovoltaic-thermal system. The maximum thermal and electrical efficiencies were 47.82 % and 9.88 %, respectively, at 0.06 kg per seconds. The exergy efficiency was found in the range of 9.85-14.30%. Based on the experimental evaluation, uncertainty analysis was performed. The results revealed that the annual CO2 mitigation for photovoltaic and photovoltaic-thermal system was 225.46 kg annual and 464.8 kg annual, while simple payback periods were 4.53 years 3.03 years, respectively. The analysis offers an efficient estimate of experimental features of photovoltaic and photovoltaic-thermal systems from an energy-exergy, environmental and cost-benefit standpoint.

Comparing the thermodynamic performance of organic Rankine and Kalina cycles in solar energy systems

This paper reports on a comparative study of the thermodynamic performance of the organic Rankine cycle (ORC) and Kalina cycle 11 (KCS11) using solar energy for application in residential or commercial sectors. The objective was to determine the amount of power that can be produced by solar energy systems using low-quality energy sources (hot water at temperatures above 60 $$^o$$ C), from the viewpoints of the first and second laws of thermodynamics. Moreover, the performance impact of coupling these cycles to hybrid solar photovoltaic-thermal collector systems (PV/T) to increase the total power generation for the same surface area was analyzed. In particular, the PV/T systems were employed to increase the production of solar energy systems, as the efficiency of photovoltaic cells reduces under hot climates, such as the climate in Brazil. The results indicated that the exergy efficiency of the KCS11 is higher than that for the ORC. Nevertheless, both cycles as the bottoming cycles to PV/T collector configurations increased the total theoretical electric power generation, for the design study, in approximately 0.4 kW per unit of area.

Theoretical approach model of building integrated photovoltaic thermal air collector

Over recent years the photovoltaic technology has obtained significant development, especially in building integrated photovoltaic thermal (BIPVT) system. Photovoltaic thermal (PVT) air collectors are advantageous because of their efficiency. Various studies have been conducted to determine the ideal parameters of PVT air collectors. Few theoretical approach models of PVT air collector systems were used to help detect occurrences in a PVT collector system and calculate the optimal parameters. The heat transfer and energy balance of PVT air collectors were analysed and reviewed based on the model, quantity of cover, channels and forms of the collector. A mathematical model was developed to describe actual working situations and to examine new shut PVT collectors. The first law of thermodynamics is the principal equation in the model. Different analysis methods were utilised to evaluate PVT performances, which are generally based on energy and exergy analyses. This review focuses on theoretical approach model of single-pass PVT air collector.

Photovoltaic-thermal hybrid collector performance for direct trigeneration in a European building retrofit case study

This article compares the annual energetic, exergetic and economic performance of a combined (hybrid) photovoltaic-thermal collector system (PVT) to that of a system with separate solar thermal and photovoltaic collectors. Furthermore, energy saving potentials through refurbishment of the building envelope are investigated. The analysis is based on simulations with an experimentally validated PVT model. The major novelty of the study is that the water based PVT collectors are also used for long wave radiative cooling. Three different residential case study buildings from Central to Southern European climate zones are investigated. Their heat, cooling and electricity demand, as well as their renewable supply, are determined along with savings through the envelope measures. In general, the performance of the PVT system varies strongly with the boundary conditions of the demand profile, climate situation and energy price levels. The results demonstrate that PVT collectors used for heat (primary DHW) and electricity offer approximately 6–7 percentage points higher exergetic efficiency than thermal and PV collectors equally sharing the available surface area. Raising the temperature level for cooling by 4K increases the amount of renewable cooling by a factor 2–4. The analysis shows that the economic performance of the trigeneration PVT system is only better than separate generation if the additional electricity and cooling generate enough benefit to compensate the loss of heat gains. Especially in the Portuguese location of Almada, with high electricity price levels and high enough cooling demand, the application of PVT in a trigeneration system is recommendable from an exergetic and economic point of view.

Performance evaluation of photovoltaic–thermosyphon system for subtropical climate application

The rapid development and sales volume of photovoltaic (PV) modules has created a promising business environment in the foreseeable future. However, the current electricity cost from PV is still several times higher than from the conventional power generation. One way to shorten the payback period is to bring in the hybrid photovoltaic–thermal (PVT) technology, which multiplies the energy outputs from the same collector surface area. In this paper, the performance evaluation of a new water-type PVT collector system is presented. The thermal collection making use of the thermosyphon principle eliminates the expense of pumping power. Experimental rigs were successfully built. A dynamic simulation model of the PVT collector system was developed and validated by the experimental measurements, together with two other similar models developed for PV module and solar hot-water collector. These were then used to predict the energy outputs and the payback periods for their applications in the subtropical climate, with Hong Kong as an example. The numerical results show that a payback period of 12 year for the PVT collector system is comparable to the side-by-side system, and is much shorter than the plain PV application. This is a great encouragement in marketing the PVT technology.