A review of photovoltaic/thermal (PV/T) incorporation in the hydrogen production process

0 Introduction

Incorporating both photovoltaic (PV) and solar thermal (ST) components, PV/T efficiently harnesses solar energy, converting it into electricity and heat [1].These systems,depicted in Fig.1a and 1b,have gained increasing popularity due to their capacity to generate hot water or air while simultaneously producing electricity [2].

As a result,they contribute to energy cost reduction and participate significantly in mitigating GHGs.The installation of PV/T is relatively straightforward in residential,commercial,and industrial settings,and they demand minimal maintenance (Fig.1c).As a reliable and clean energy source,they stand out for their efficiency and reliability[3].

Fig.1.(a)Solar cell to PV array,(b)Solar Thermal,ST,(c)PV/T system.

To improve PV/T performance, various cooling strategies have been employed by manufacturers and designers[4].These strategies encompass diverse cooling methods,including air-cooling[5],water cooling[6],water-air cooling [7], nanofluid cooling [8], Bi-fluid [9], ‘‘phase change material” (PCM) cooling [10], and nanofluid and nano-PCM cooling [11] as shown in Fig.2.Different cooling agents such as water, ethylene glycol, and oil have been utilized, and nanofluids with various metallic and nonmetallic nanoparticles and their oxides have been tested[12].Advanced techniques have been employed to effectively disperse these particles within the base fluid [13].Additionally,a variety of PCMs particularly paraffins with varying melting points, have been extensively studied and employed[12].Over the past decade,numerous experimental and theoretical studies have resulted in the development of PV/T exhibiting exceptional electrical and thermal efficiencies [3].These systems consistently outperform traditional PV, maintaining superior productivity even under extreme temperature and radiation conditions[13].

Fig.2.PV and Types of PV/T conductive and liquid cooling.

In addition to atomic hydrogen, molecular hydrogen(H2), and hydrides exist as well [14].Hydrogen characteristics are discussed in terms of(i)abundance,(ii)reactivity,and (iii) energy carriers [15].However, on earth, most often, Hydrogen is found in addition to oxygen or carbon(in water or hydrocarbons) [16].Hydrogen can react with oxygen to form water,with carbon to form hydrocarbons,and with many metals to create metal hydrides [17].Also,in terms of energy carriers, the potential use of hydrogen as a clean energy carrier has attracted significant attention.A variety of sources can be used to produce it, such as water, natural gas, and biomass [18].Hydrogen is a main product when used in fuel cells(emits no greenhouse gases)or combustion processes,it generates energy without emitting greenhouse gases [19].However, hydrogen’s advantages are (i) clean energy source, (ii) versatility, and it has high energy density[20,21].Climate change can be mitigated by reducing dependence on fossil fuels through the use of renewable energy [22].There are many uses for Hydrogen, such as fuel for vehicles, feedstock for industrial processes,and an energy storage medium for intermittent renewable energy sources [23].As well as being blended with natural gas, it is also able to run through existing gas pipelines, making a path available for decarbonizing the natural gas sector[24,25].Hydrogen can store and deliver more energy per unit weight compared to conventional batteries, enabling longer-range and shorter refueling times for hydrogen-powered vehicles [26].

On the other side hydrogen disadvantages and challenges such as (i) production challenges, (ii) difficulty of storage and distribution, and (iii) safety concerns [27].The primary challenge with hydrogen lies in its production.The most common methods involve using fossil fuels,which can result in carbon emissions[28,29].While renewable methods like water electrolysis exist, they are currently more expensive and less efficient [30,31].The energy density of hydrogen is low in volume [32].The use of high-pressure systems or large storage tanks is required.Additionally, its distribution infrastructure is limited,requiring significant investment to develop a comprehensive hydrogen supply chain [33,34].In certain circumstances, hydrogen can form explosive mixtures with air due to its high flammability.Its use and storage requires careful handling, and safety measures must be in place to minimize risks [35,36].

Despite these challenges, in the transition to a sustainable energy future, hydrogen can play a crucial role [37].To address its limitations and maximize its benefits,ongoing research and development is being conducted.Fig.3 shows methods and applications of hydrogen production and consumption [38].

Hydrogen can be produced through various methods,ranging from conventional processes to emerging technologies as shown in Fig.3.There are different methods used to produce hydrogen such as:

A.Steam Methane Reforming (SMR)

Hydrogen is most commonly produced by steam methane reforming,which accounts for most of the global supply [39].A catalyst produces hydrogen gas and carbon monoxide as a result of the reaction between methane(which makes up the majority of natural gas) and hightemperature steam vapor.Afterward, hydrogen and carbon monoxide are separated from the mixed gas mixture,known as syngas [40].Hydrogen is produced through the steam methane reforming process shown in Fig.4.

B.Hydrocarbons Partial Oxidation

Partial oxidation involves reacting hydrocarbons(gasoline or natural gas for example) in a limited environment of oxygen or air [41].The process typically involves a catalyst to produce carbon monoxide and hydrogen gas.This process is similar to steam methane reforming but uses less steam.Partial oxidation can be used as a standalone method or combined with steam reforming to enhance the hydrogen production process [42].

Fig.3.Hydrogen production and consumption methods and applications[38].

Fig.4.Steps of hydrogen production using steam methane reforming process.

C.Biomass Gasification

Syngas is a gas mixture formed when organic matter is thermally transformed into a gas mixture via biomass gasification [43].Materials such as agricultural waste, forest waste, or energy crops can be included in this list.Among the components of syngas are carbon monoxide, hydrogen,carbon dioxide,and traces of other gases.By cleaning and purifying the syngas, it becomes possible to separate hydrogen and use it for a variety of purposes[44].Biomass gasification offers the advantage of utilizing renewable and carbon-neutral feedstock for hydrogen production.

D.Water Electrolysis

Using electricity, water molecules are split into hydrogen and oxygen through electrolysis.Electrolysis involves the submergence of two electrodes in an electrolyte solution, one anode and one cathode [45].At the cathode,hydrogen gas is generated when an electric current passes through it, and at the anode, oxygen gas is produced.There are various types of energy sources that can be used for water electrolysis.In terms of hydrogen production,renewable electricity is one of the best sources [46].Fig.5 depicts the historical development of water electrolysis through generations.

E.Alkaline Water Electrolysis

An alkaline electrolyte is used in alkaline water electrolysis, typically potassium hydroxide (KOH), to facilitate the splitting of water molecules[48].It operates at elevated temperatures and requires electrodes made of nickel or nickel-plated materials.In industry, hydrogen is produced on a large scale using alkaline water electrolysis due to its relative simplicity and maturity as a technology.Fig.6 illustrates the working principle of alkaline water electrolysis [45].

F.Solid Oxide Electrolysis

Water is split into hydrogen and oxygen using solid oxide electrolysis, which uses an electrolyte consisting of a solid oxide [49].A high temperature is required for it to operate(typically above 800°C)and have the advantage of high efficiency.To increase overall energy efficiency and use excess heat, concentrated solar power or waste heat can be integrated with solid oxide electrolysis cells.

G.Photoelectrochemical (PEC) Water Splitting

Fig.5.Evolution of water electrolysis through generations [47].

Fig.6.Schematic diagram of alkaline water electrolysis works [45].

PEC water splitting employs a semiconductor material that absorbs sunlight and hydrogen,and oxygen are separated from water by a photoelectrochemical reaction.It combines the principles of solar energy conversion and electrolysis[50].The PEC water-splitting technology is still in its infancy,to achieve cost-effective and efficient systems for sustainable hydrogen production.Fig.7 shows a PEC water-splitting cell schematic illustration with an anode as the central electrode (a) while Diagram (b) illustrates a step-by-step guide to PEC water splitting.

Hydrogen can be produced using solar energy through a process called water electrolysis, which uses the PV power to produce hydrogen [51].Hydrogen and oxygen are separated from water molecules (H2O) using electrical energy [23].The electricity needed for electrolysis can be generated by PV, PV/T, or ‘‘concentrated solar power”(CSP) systems.

An electrolysis process is powered by electricity from PV or PV/T [52].A CSP system, on the other hand, concentrates irradiance onto a receiver, which then converts it into heat [53].Steam turbines that generate electricity for electrolysis can be driven by this heat.By using solar energy for green hydrogen production, several environmental and sustainability benefits can be achieved.Additionally, solar-based hydrogen production does not release GHGs, making it a clean and low-carbon method of hydrogen generation.

Fig.7.(a) An anode is the central electrode of a typical PEC water splitting cell; (b) PEC’s three main steps for splitting water [50].

Various applications can be found for green hydrogen,which is produced by solar energy.As a fuel,it can be used in the transportation sector.As an energy carrier,it can be employed for energy storage, or as a feedstock for industrial processes [54].By incorporating PV/T into the green hydrogen production process, the reliance on fossil fuelbased electricity and thermal energy can be significantly reduced.This integration increases green hydrogen production process sustainability and its environmental benefits, making it more efficient and aligned to decarbonize the energy sector.

Incorporating a PV/T into the green hydrogen process can be explained by:

PV panels generate the needed electricity to supply the electrolyzers.

A ST utilizes the heat generated by the sun to produce thermal energy through collectors to absorb solar radiation and transfer the heat to a fluid medium, such as water or oil.This heated fluid can then be used for various applications, including space heating,water heating, or even powering a steam turbine for electricity generation.

To explain how these systems can be incorporated into the green hydrogen process:

Powering Electrolyzers: Using an electrolyzer, green hydrogen production is achieved from hydrogen and oxygen separation from water [55].By integrating a PV, the electricity generated can directly power the electrolyzer, replacing or reducing the need for electricity from the grid.As a result,hydrogen production has a lower carbon footprint [56].

Thermal Energy for Electrolysis: It is possible to provide the electrolysis process with heat using Solar Thermal (ST) collectors.Preheating the water before electrolysis is possible with the help of this heat,reducing the energy input required for the electrolysis reaction.By utilizing ST energy, the overall energy consumption and associated GHGs can be reduced,making the hydrogen production process greener [57].

PV/T Systems: Both electricity and heat can be generated by a PV/T system.The electricity generated can be used to power the electrolyzer, while during hydrogen production, the excess heat can be used for water heating or other thermal applications.This integrated approach maximizes the utilization of solar energy and improves overall system efficiency [58].

In this study, PV/T technology is being revised about green hydrogen production.Based on a careful analysis of the research works over the past five years, it has been found that most authors who have reviewed articles on green hydrogen production have explained in brief the possibilities and benefits of using PV/T systems [59-63].

Hybrid solar PV/T systems can reduce the levelized cost of hydrogen (LCOH) by generating electricity and heat from a single system, rather than relying on two separate systems.This approach offers economic sustainability opportunities and encourages innovation in the design and application of solar PV/T systems for green hydrogen production.

Integrated PV/T systems also serve as effective energy storage solutions, addressing some of the existing knowledge gaps in energy capture and storage development.This study serves as a critical review of PV/T system integration for green hydrogen production, playing a vital role in bridging knowledge gaps,stimulating innovation,and supporting the transition to a new energy system.

Despite significant advancements in solar PV/T systems and their role in hydrogen production, no comprehensive review has been published that consolidates research findings, technological developments, and performance enhancements in this field.Herein, we address this gap by presenting a systematic and in-depth review of PV/T technologies, emphasizing their design, operation, and integration for sustainable hydrogen production.Unlike previous reviews, this study:

Provides the first comprehensive review that systematically consolidates research and development efforts related to PV/T systems for green hydrogen production.

Analyses the key principles and mechanisms governing PV/T system performance, identifying critical factors influencingefficiency,cost-effectiveness,and sustainability.

Evaluates advanced and emerging PV/T technologies,including material innovations,heat transfer improvements, and hybrid system configurations.

Investigates the techno-economic feasibility of PV/Tintegrated hydrogen production, assessing costbenefit analysis, energy payback time, and commercialization potential.

Identifies existing challenges and future research directions, offering practical recommendations to enhance the design, operation, and implementation of PV/T systems in the hydrogen production sector.

1 Methodology

The procedures used in this review paper (A review of photovoltaic/thermal (PV/T) incorporation in the hydrogen production process)include the important steps shown in Fig.8.The review steps were carefully selected to ensure that the approach taken is both systematic and comprehensive:

Formulating the research problem:The review process begins with defining the research question and scope of the review and then developing it to be more comprehensive.This step is essential because it provides the rationale for the review and guides the rest of the other procedures such as selecting the literature and evaluating the data.

Search strategy: A search strategy was conducted and formulated to obtain relevant literature.Researchers referred to academic databases, search engines, and libraries using the keywords and Boolean operators:occurrence,prevalence,programmer,occupation,profession, and occupation.Researchers specified the quality of studies to be reviewed as being published in Scopus and Glarivate Database and issued by reputable publishing houses.

Study selection criteria: Selection criteria were then determined, which included assessing the applicability and quality of the source by applying the previous criteria.Only a specific group of these distinguished publications were isolated and entered into the review process.

Fig.8.Review process block diagram.

Data extraction:After identifying appropriate studies,data were extracted from these studies.This data collection process included extracting the unique results of each study;methods,results and arguments applicable to hydrogen production through solar/thermal energy systems.

Quality assessment: As a systematic approach to data collection, the quality and objectivity of the studies were first assessed, and then the methodological quality of the included studies was verified.This step typically requires each co-author to review a specific list of studies for a specific section.In order to make the process as objective as possible, the remaining co-authors objectively review their colleagues’work and verify the data used in the reviewed studies.An article is not considered complete unless everyone agrees and endorses it.

Data synthesis and analysis: The final step involved analyzing the collected data.This process entails sorting the extracted data and compiling them into a composite format.Several methods adopted in scientific review studies were used to shed light on the results showing the extent of differences between studies or identifying trends or shortcomings in literature.

Finally,a conclusion section is developed to explain and present the collected results.This section focuses on drawing the main conclusions from the review, directions for future research, and general recommendations for hydrogen production by PV/T systems.The researchers expect that this approach will help provide a rigorous and systematic evaluation of the available literature,and provide new insights into hydrogen production technologies to date.

Literature has also been examined for gaps, controversies, and trends.To identify the similarities, patterns, and relationships between the sources, researchers identified the common themes, patterns, and relationships.Literature is also emphasized for its differences and conflicts.On the basis of the review and understanding of the selected topic, ideas and interpretations were formulated.

2 Integration of PV/T systems in green hydrogen production

2.1 Photovoltaic effect

The ‘‘photovoltaic effect” allows sunlight to be directly converted into electricity by PV devices.Clean and renewable energy can be generated using these building blocks in PV systems.An electric current is created when photons from sunlight are absorbed by semiconductor materials,such as silicon[64].A solar cell converts sunlight’s photons into electrons in the semiconductor material, enabling the electrons to break free from their atoms and flow through the cell.Direct current(DC)electricity is generated by this flow of electrons [65].A solar panel or module consists of multiple solar cells connected.To achieve the desired voltage and power output, they can be connected in series or parallel.

PV systems consist of solar panels, which contain an array of interconnected solar cells, along with other components such as inverters,batteries,and wiring[66].These systems can be installed on rooftops,in open fields,or integrated into building materials.Continuous advancements in solar cell technology, such as the development of thinfilm solar cells and higher-efficiency designs, contribute to making PV systems more efficient and affordable [67].

The I-V ‘‘current-voltage” and power curves of a PV system provide valuable insights into its performance characteristics as shown in Fig.9.These curves illustrate the relationship between the I, V, and P output of the PV module or system under different operating conditions[68].PV system current output at various voltage levels is represented by the I-V curve.Changing the voltage across the PV module changes the current across the module.Typically, the I-V curve exhibits a nonlinear shape,where the current initially increases with voltage until it reaches a peak,after which it starts to decrease.The power curve, however, illustrates the PV system’s power output as a function of voltage.Current and voltage are combined to form it (P = I V).The power curve shows the ‘‘maximum power point” (MPP), which represents the V and I combination that results in the highest power output from the PV [69].For optimal performance, MPP is a critical component of determining a photovoltaic system’s operating point.The shape of both the I-V and power curves can be influenced by various factors,including solar irradiance[70],temperature[71],shading[72],and the characteristics of the PV module itself [73].These curves provide important information for system design, performance evaluation, and troubleshooting.By analyzing the I-V and power curves of a PV,researchers and engineers can assess the system’s efficiency, identify any deviations from expected performance,and optimize its operation for maximum power output.This information is vital for accurately estimating energy production, determining the appropriate sizing and configuration of PV systems, and evaluating the economic viability of solar energy projects[74].

The ‘‘fill factor” (FF) indicates PV module efficiency and performance.In other words, it is the value obtained by dividing the maximum power of a PV device by the product of‘‘open-circuit voltage”(Voc)and‘‘short-circuit current” (Isc).The fill factor essentially quantifies how effectively the PV device can convert incident sunlight into usable electrical power [75].A higher FF indicates better performance, as it signifies a smaller loss in power due to internal resistances within the device.FF depends on many factors, including operating conditions, dust accumulation, irradiance, PV materials, and manufacturing processes [66].It is commonly determined experimentally by plotting the I-V curve of the device and calculating the FF from the curve.A high FF is desirable as it indicates a more efficient PV that can deliver a greater amount of power for a given amount of irradiance.Improving the FF is an important goal in PV research and development,as it contributes to enhancing the system’s total efficiency and the economic viability of solar energy systems.

Fig.9.Photovoltaic I-V curve.

2.2 Solar thermal

ST collectors are devices that capture and harness solar energy to generate heat.A PV/T system converts sunlight into thermal energy that can be used for many purposes,including heating water, generating steam, or providing space heating in residential, commercial, and industrial settings[76].ST collectors are typically made up of a selective absorber surface that absorbs sunlight and a heat transfer fluid such as ‘‘water or a heat-transfer oil” that circulates through the collector to carry the captured heat to a storage or utilization system [77].These collectors come in different types, including ‘‘flat-plate collectors”,‘‘evacuated tube collectors”,and‘‘parabolic trough collectors”, each with its advantages and applications as shown in Fig.10.Flat-plate collectors are cost-effective for lowtemperature, small-scale applications.While evacuated tube collectors offer better insulation and performance in diverse climates.Parabolic trough collectors are ideal for high-temperature, large-scale applications but come with higher costs and complexity.

The use of ST collectors reduces dependence on fossil fuels and increases the efficiency of renewable energy sources [78].

2.3 Photovoltaic/thermal systems

Fig.10.(a)Flat Plate Collector,FPC,(b)Evacuated Tube Collector,TC,and (c) Power Thermal Collector, PTC.

PV/T, also known as hybrid solar systems, combines the functionalities of both PV and ST technologies.These integrated systems are designed to simultaneously generate electricity and capture thermal energy from the sun, providing a dual output of electrical power and heat.In addition to generating electricity, PV/T systems also incorporate a ST component [79].This part of the system utilizes STCs as shown in Fig.11,to absorb solar radiation and transfer the heat to a fluid medium,such as water,air,nanofluid,etc.The heated fluid can then be used for applications like space heating, water heating, or even driving thermal processes like desalination or absorption cooling[80].There are several advantages to integrating PV and ST technologies in PV/T systems:

PV/T can achieve higher overall efficiency compared to standalone PV or ST systems.The captured solar energy is effectively utilized for both electricity generation and heat production, maximizing the system’s energy conversion efficiency [81].

PV/T enables the utilization of available space more efficiently by combining both solar energy conversion technologies in a single system.This is particularly beneficial in scenarios where space is limited or expensive [82].

Fig.11.ST collectors(a)Direct(b)Serpentine(c)Spiral,(d)Parallel,(e)Web, (f) Oscillatory, (g) Split.

The simultaneous generation of electricity and thermal energy allows for energy synergy.PV cells can be improved by using excess heat from the ST component, which reduces their operating temperatures and increases their output, for instance [83].

PV/T can offer economic advantages by reducing the overall cost of separate PV and ST installations.Additionally, the dual output of power and heat increases the system’s overall value proposition and potential return on investment [84].

In addition to residential and commercial buildings,PV/T devices can be applied to industrial facilities,agricultural operations, and commercial establishments [85].They provide a sustainable and versatile solution for harnessing solar energy, maximizing energy efficiency,and meeting both electrical and thermal energy requirements.

2.4 Green hydrogen process and PV/T

Green hydrogen can be produced more sustainably and efficiently with PV/T integration [86].Utilizing renewable energy sources, such as solar power, to electrolyze water produces green hydrogen,which is produced by separating hydrogen and oxygen as shown in Fig.12a[51].As a result of this integration,the green hydrogen production process is more energy-efficient, cost-effective, and environmentally sustainable, contributing to a future in which energy is cleaner and more sustainable [87].

Solar or wind energy is used as the primary energy source for the production of hydrogen gas (H2) [53].It is considered an environmentally friendly and sustainable method for producing hydrogen since it does not release CO2 emissions or use fossil fuels.The key steps in the green hydrogen process are as follows [88]:

Renewable Electricity Generation: Solar and wind power are two renewable sources of electricity.A photovoltaic system, a PV/T system, a CSP system, or a wind turbine captures the sun’s or wind’s energy and converts it to electricity as shown in Fig.12b.

Water Electrolysis: The generated electricity is then directed to an electrolyzer,which is a device that splits water (H2O) into its constituent elements: H2 and O2.The electrolyzer consists of two electrodes, a cathode and an anode, immersed in water.A current passing through water causes hydrogen ions (H+) to migrate to the cathode and gain electrons, forming hydrogen gas, while oxygen ions (O2 ) migrate to the anode and form oxygen gas.

Hydrogen Purification: The produced hydrogen gas may undergo purification to remove impurities, such as moisture, trace gases, and carbon monoxide (CO),to meet the required purity standards for various applications.Fuel cells require a high level of purity,the supplied H2 fuel quality becomes of paramount importance.Fuel cells can be irreversibly damaged by even the tiniest amount of some impurities.An evaluation of current standards for H2-related fuel cell vehicles in China and abroad was conducted by Du et al.[89].Also, the changing causes and trends of these standards were analyzed in detail.The‘‘Pressure Swing Adsorption” (PSA) process was used to generate high-purity hydrogen from several gaseous mixtures.A review of the Polybed H2 PSA process and the latest findings from R&D was conducted by Luberti and Ahn [90].High-purity hydrogen is produced as well as CO2 through the Polybed PSA process.

Storage and Distribution: Once the hydrogen gas is purified, it can be stored and distributed to various end-users or applications.Hydrogen can be compressed,liquefied,or stored in other forms, depending on the specific storage and transportation requirements [91].Several geological formations were explored by Tarkowski [92] for the storage of hydrogen underground, including aquifers, depleted oil and gas reserves, and salt caves.Hydrogen can be stored underground in a similar way to natural gas.Only electrolysis makes this method economically feasible as a result of its low price.According to Hassan et al.[93], hydrogen storage systems are essential for achieving economical and efficient hydrogen use.Many storage systems have been examined in terms of density and density, as well as parameters associated with storage and release processes.For smallscale storage, pressure vessels can be used, while salt caverns can be used for large-scale storage.Hydrogen is also stored very densely in material-based storage,which is safe and compact.Metal hydrides can also store hydrogen and thermal energy.There is a high hydrogen storage capacity of up to 18.5% in materials containing complex metal hydrates, such as lithium borohydride and sodium alanate.However, as the number of plug-ins increases, the storage density falls sharply.Hydrogen storage systems in vehicles can also use Ammonia Borane.

Fig.12.Green hydrogen process (a) schematic [51], (b) block diagram [95].

Hydrogen liquefaction is one of the main technologies used in hydrogen storage as it can be stored in a liquid state at ultra-low temperatures.This process offers several benefits,including the energy density is higher than that of gaseous storage, which means it is easier to transport and store in relatively small volumes.The downside of this method is that liquid hydrogen can only be stored in specialized cryogenic tanks that store hydrogen at temperatures below 253 °C to keep it in its liquid state.Hydrogen liquefaction involves exposing hydrogen gas to high pressure and cooling it to its liquid phase.This process requires intensive energy and the application of the latest technologies to enhance safe and efficient results.The main disadvantage of hydrogen liquefaction is the energy density required when cooling the gas to ultralow temperatures.The efficiency of liquefaction systems depends largely on parameters such as the technology used and the conditions in which the system operates.Furthermore, although liquid hydrogen has a higher storage density, it has higher flammability and hazard factors for refrigerants.For this reason,specialized studies are underway to investigate ways to make liquefaction processes more energy-efficient, less expensive, and safer.As hydrogen becomes more important as a fuel in the transition to sustainable energy systems, new liquefaction methods will be essential for storing and distributing hydrogen in larger quantities.

Hydrogen Utilization: There are a variety of uses for green hydrogen as an energy carrier.It is possible to generate electricity from hydrogen using a fuel cell that is highly efficient and emits no emissions.Hydrogen fuel cells can power vehicles, provide electricity for buildings, and be used in industrial processes.Additionally, hydrogen can be further processed and converted into other valuable chemicals or fuels [94].

Transport, industry, and energy production can all be decarbonized with green hydrogen.By leveraging renewable energy resources, the green hydrogen process contributes to reducing GHGs and promoting a more sustainable energy future [56].

Green hydrogen can be produced using several renewable energy technologies.The most common ones include:

PV: directly converts irradiance into electricity, which can be used directly in powering electrolyzers to produce hydrogen.

PV/T: utilized irradiance to produce electricity and heat to be incorporated into green hydrogen production process.

Concentrated Solar Power Stations(CSP):The process of CSP involves concentrating sunlight onto a receiver,heat is generated by this process,which can be used to produce hydrogen through thermal electrolysis.

Wind Turbines: Using wind turbines, electricity can be generated, which can then be used to produce hydrogen by electrolysis.

Hydroelectric Power: By converting the energy of falling or flowing water into electricity, hydrogen can be produced.

Biomass Conversion: Biogas or biofuels can be obtained by anaerobic digestion or gasification of organic waste or energy crops.Utilizing biogas as a fuel requires the conversion of biogas to hydrogen.

Geothermal Energy: Electrolyzers powered by this technology can produce hydrogen by using the heat of the Earth.

Tidal and Wave Energy:Green electricity can be generated by harnessing the tides and waves to generate hydrogen.

Electrolysis of water can generate green hydrogen without releasing carbon dioxide as a result of these renewable energy technologies.In the next section an intensive literature review was conducted to clarify the use of PV/T technology to supply the energy needed to produce green hydrogen.

3 Literature review and discussion

Although PV usage as a green hydrogen production source has been recognized for quite some time, there has been a lack of comprehensive research on integrating PV/T systems into the green hydrogen production process.Gado et al.[58]evaluated the viability of an integrated system combining an adsorption cooling system and an electrolyzer operated by PV/T technology.This system was tested in the climate conditions of Egypt and aimed to simultaneously produce green hydrogen, cooling, and hot water.The electricity generated by the PV/T system powered the electrolyzer for hydrogen production.A daily‘‘Coefficient of Performance” (COP) of 0.47 was found for the adsorption cooling system with a cooling capacity of approximately 7 kW during the summer season,according to the research.Based on the results, the system produced 8,282 kWh of cooling, 1,723 kWh of heating, and 626 kg of hydrogen per year.Also, the system was reported to have an energetic efficiency of 12.3% and an exergetic efficiency of 10.6%.Considering the costeffectiveness of the system, the payback period was remarkably short.Furthermore, the system achieved a reduction of 52.2 tons of carbon dioxide emissions.

According to Shen et al.[96], nanofluids have a significant impact on PV/T systems.Zinc oxide nanoparticles(ZnO) were used with a 0.25% weight concentration in water-based nanofluids.There were three different mass flow rates tested between 9:00 A.M.to 4:00 P.M.These mass flow rates, ZnO nanofluid was pumped through PV/T panels at 0.008 kg/second, 0.010 kg/second, and 0.012 kg/second.An array of parameters was measured,including output power, surface temperature, fluid outlet temperature, thermal efficiency, and electrical efficiency.Additionally,hydrogen was produced via electrolysis using the PV/T system.By controlling nanofluid mass flow rates at the optimal level,the panel was able to increase its electrical output,as well as produce hydrogen more efficiently.The maximum thermal efficiency achieved was 33.4%,when the nanofluid flow rate was 0.012 kg/s while the hydrogen production rate reached 17.4 mL/min.Electrolysis of hydrogen can be achieved through the PV/T system based on extensive observations and results.A system with nanofluids can be significantly improved in terms of its electrical output,thermal efficiency,and hydrogen generation capabilities by incorporating them at the optimal mass flow rate.Anderson et al.[97]tested a new PV/T system for hydrogen production.Through electrolysis, the PV/T produces hydrogen.To maximize electric output while minimizing energy losses, the research investigated the use of nanofluids, namely water-MWCNT and water-nano Fe2O3, as passive cooling agents.Hybrid systems circulated Fe2O3 and MWCNT nanofluids at flow rates of 0.0075 kg/s and 0.01 kg/s, respectively.As of 12.30 P.M., the system performed optimally in terms of peak electrical output and thermal efficiency.From 12.15 P.M.onwards, hydrogen production reached its highest level.The energy losses are effectively compensated for,while the electrical output is superior to conventional methods as a result.Both electricity production and hydrogen generation were found to be efficient at 0.01 kg/s based on the results obtained.Through the integration of an electrolyzer, hybrid systems are capable of producing hydrogen, which can be stored for future use.As compared to traditional energy solutions, this approach provides a more efficient and sustainable solutionforgeneratingelectricityandhydrogen simultaneously.

A method for generating electricity and liquid hydrogen using PV/T technology was presented by Sharifi et al.[97].The study compared the system benefits with conventional liquefaction systems and their associated power and cooling systems.Various factors influencing effectiveness, cost efficiency, liquid hydrogen production, and environmental impact were examined,and an optimization approach was employed to achieve multiple objectives simultaneously.According to the findings, 54301 kJ/kg H2 are consumed during the liquefaction cycle.Furthermore, increasing the size of the solar panels resulted in a 37.5% increase in liquid hydrogen production.At the maximum area of the panels, the system produced the maximum power(4550 kW).In this study, the system produced liquid hydrogen at a rate of 13 kg/s and cost 15.1 dollars/GJ with an efficiency of 56.3%.

In their study,Zheng et al.[98]combined a solar-driven electrolysis cell, a solid oxide fuel cell, PV/T system, and thermal energy storage into an innovative multigeneration system.At night, surplus solar electricity is stored as green hydrogen and used to power a hydrogenfuelled solid-oxide fuel cell.The study includes a comprehensive analysis of the system’s thermodynamic and economic performance using multicriteria evaluation.Under different operating conditions, the system’s characteristics are examined,and its feasibility is evaluated.The proposed PV/T system is highly energetic efficient and exegetic effective, reaching 80.7% and 33.8% respectively, based on the study results.The PV/T system can continuously supply solar electricity to the user for 14 h in cooling mode and 9 h in heating mode.The economic analysis reveals a net present value of 45.78 M$, a simple PBP period of 9.11 years, with a dynamic PBP of 11.55 years.This project has 9.96% internal rate of return, which exceeds the interest rate by 4.96% points.Hybrid systems achieve an economic superiority of 0.0540 $/kWh, demonstrating excellent economics.

In the above-mentioned work, the integration of PV/T systems in green hydrogen production has been explained,but comparisons in aspects of efficiency and advantages are quite unclear.Gado et al.[58] showed an integrated system of absorption cooling and PV/T electrolyzers with EE of 12.3%and generating massive cooling,heating,and hydrogen per year.However, Shen et al.[96] employed nanofluids to increase thermal efficiency by getting to 33.4%and increase hydrogen generation rates via the control of the mass flow.Anderson et al.[97] examined various other hybrid systems using different nanofluids in the same reactors, and the authors also observed enhanced performance of the system for electricity generation as well as hydrogen production.However, such differences can suggest that efficiencies as documented differ due to experiment conditions like climate,the material used,and or the system design.For instance,Sharifi et al.[98]concentrated on the production of liquid hydrogen and pointed out that the size of the solar panels greatly enhanced production but there was no direct comparison with other techniques.A literature review reveals that green hydrogen production is discussed from a variety of perspectives, including technical, economic, environmental, and social factors as shown in Table 1.

Several technical aspects are investigated for producing renewable hydrogen as illustrated in Fig.13a.The key areas of investigation include the following:

Different electrolysis technologies, such as ‘‘alkaline”electrolysis, ‘‘proton exchange membrane” (PEM)electrolysis, and ‘‘solid oxide electrolysis cells”(SOEC),are explored to identify their efficiency,durability, scalability, and cost-effectiveness for hydrogen production [109].

Research focuses on developing and optimizing catalysts and electrodes used in electrolyzers to enhance their performance, improve efficiency, conserve energy,and enhances the electrolysis system’s lifespan.

Research is conducted to understand the impact of renewable energy sources on the efficiency of electrolysis systems, intermittency management, and overall system performance.This includes investigating strategies for optimal matching of renewable energy availability with hydrogen production demand.

Table 1 Comparative of green hydrogen criteria in literature.

ReferenceEconomicTechnicalEnvironmentSocial[99][100][101][102][103][104][105][106][107][108]

Fig.13.Green hydrogen production (a) technical, (b) economic, (c)social, and (d) environmental aspects.

Hydrogen production systems’ overall efficiency of is assessed,considering factors such as energy losses during electrolysis, thermal management, heat recovery,system integration, and utilization of waste heat.The goal is to convert electrical or thermal energy into hydrogen with the greatest efficiency possible.

Studies examine the scalability of green hydrogen production technologies,analyzing their performance and production rates at different scales to determine their commercial viability and potential for large-scale deployment.

Investigations focus on the development and optimization of storage and distribution systems for green hydrogen, this includes methods for safely storing,transporting,and utilizing hydrogen in several sectors,such as the industrial sector and power generation.

In order to determine the environmental impact and sustainability of green hydrogen production, life cycle assessments are conducted, taking into consideration several factors such as raw material extraction, manufacturing, operation, and end-of-life management of the hydrogen production systems.

Green hydrogen production requires consideration of economic factors as illustrated in Fig.13(b).The key economic aspects investigated include:

Researchers evaluate the cost components involved in green hydrogen production, including capital costs,operating costs,maintenance costs,and lifecycle costs.This analysis helps identify areas for cost reduction and optimization, enabling more economically viable hydrogen production processes.

Techno-economic analysis involves assessing the economic feasibility and competitiveness of different green hydrogen production technologies.It considers factors such as the‘‘levelized cost of hydrogen”(LCOH),cost per kilogram of hydrogen produced,and cost comparisons with other energy sources like fossil fuels.

Green hydrogen cost per unit can be reduced through economies of scale when producing this hydrogen.Researchers explore the cost reduction potential as production capacity increases, determining the optimal scale for achieving cost competitiveness.

For green hydrogen production processes to be economically feasible, infrastructure development is crucial, such as electrolysis plants, storage facilities, and transportation networks.Research investigates the costs associated with infrastructure development,including the necessary investments and potential cost-sharing models.

Evaluating market demand for green hydrogen and understanding its pricing dynamics are crucial economic aspects.Researchers analyze factors influencing hydrogen demand, including government policies,industry adoption, and market trends.They also examine price competitiveness compared to other energy sources and track the dynamics of hydrogen pricing in different regions.

Economic aspects encompass the analysis of policy frameworks, government incentives, and financial mechanisms that can support the growth and adoption of green hydrogen production.Researchers assess the impact of policy measures on reducing costs, attracting investments, and creating a favorable business environment for hydrogen production.Table 2 lists some of the most recent studies in green hydrogen production by PV/T field.

By addressing these economic aspects, the goal of research is to identify strategies for reducing the cost of producing green hydrogen, enhance its competitiveness over conventional fuels, and develop a sustainable hydrogen energy market.

Green hydrogen production has several social aspects that can have a substantial impact on communities and societies as a whole as illustrated in Fig.13c.In terms of social aspects,green hydrogen production presents several challenges:

Table 2 Most recent articles dealt with hydrogen production by PV/T systems.

Ref.No.Year Location PV typePV/T system typeEfficiency increase rate Produced hydrogen increase rate Critical findings[58]2023 EgyptPolycrystalline Water cooled PV/T10%138%This system produces cooling, heating, and hydrogen of 8282 kWh, 1723 kWh, and 626 kg annually.In addition, annual energetic and exergetic efficiencies of 12.3% and 10.6%,respectively, have been demonstrated for the present system.A payback period of 0.8 years and a carbon dioxide reduction of 52.2 tons were demonstrated by the proposed system.[86]2023 ChinaConcentrated PV/T34.66%22.7%With the liquid sphere, the system has greater electrical efficiency and is more sensitive to fixation tolerances in the optical axis direction.Therminol® VP-1 and Tetradecane, but not Dimethylsilicone, are better working fluids for spherical lenses.Constant production is demonstrated by the results.The system has an average STH efficiency of 22.1% and a peak efficiency of 22.7%.[97]2022 IndiaMonocrystalline 8.5%50%12:30 p.m.was the time when the highest electrical output and thermal efficiency were recorded.In terms of hydrogen production,the highest amount was recorded at 12:15 noon.Based on the results,the nanofluid produces electricity and hydrogen at 0.01 kg/s mass flow rate.Hydrogen can also be stored and used as an energy source in the future using the electrolyser as an accessory to the hybrid system.[110]2020 IndiaPolycrystalline MWCNT and Fe2O3 Nanofluid cooled PV/T Water cooled PV/T11.8%111.13%With an increase in air and water mass flow rates,energy production increases.For the water-cooled PV/T system,the highest power enhancement was 11.8% when compared with the standalone PV module.Flow rate increases reduce PV panel surface temperature, resulting in greater thermal and electrical efficiency.In order to increase the hydrogen production rate, the PV/T solar collector must have a higher power output.In addition to reducing pollution, hybrid solar collectors can produce hydrogen from various fluids.[111]2020 TurkeyMonocrystalline Water cooled PV/T15%10%Based on the proposed system, the photovoltaic system will produce 3.96 kg of hydrogen per year,whereas the PV/T system will produce 4.49 kg per year.As the current and temperature of the electrolysis circuit were changed, the electrolysis voltage changed from 200-1600 mA/cm2 and 30-60°C to 400-2350 mA/cm2 and 28.1-45.8°C.This meant a range of energy efficiency between 57.85%-69.45% and 71.1%-79.7%.[112]2021 EgyptPolycrystalline Water cooled PV/T16.43%43.65%For the water-based PV/TC-EHP system, the hybrid system produced 1.66 kW/day of PV output power and 3.60 kg/day of hydrogen production, while for the air-based PV/TC-EHP system, the daily PV output power and hydrogen production yields were 1.22 kW/day and 4.41 kg/day, respectively.

Table 2 (continued)

Ref.No.Year Location PV typePV/T system typeEfficiency increase rate Produced hydrogen increase rate Critical findings[113]2021 IndiaMonocrystalline Compared to water-cooled PV/T systems,nanofluid-cooled PV/T systems produce more hydrogen.A thermal reduction of 48%, 37%, and 36% was achieved using nanofluids MWCNT,Al2O3, and TiO2.[114]2021 Saudi Arabia Cooled by nanofluids(MWCNT, Al2O3&TiO2)47%, 36% &25%respectively 17.5%,16.2% &15.5%respectively 30%19%MgO can be used to store hydrogen and electricity for long-term energy storage in the CPV/T system proposed by the study.30% and 70% efficiencies were obtained for the studied system in terms of electricity and high thermal energy.A 19%increase in hydrogen production was achieved using the system.However, concentration of thermal energy density of 400 °C increases MgObased hydrogen storage by 80%.[115]2022 IndiaPolycrystalline Monocrystalline Concentrated PV/T system Air cooled PV/T33%73%An air duct with half-length fins was used in this study to introduce a new photovoltaic thermal air(PV/Ta) system.Hydrogen generation performance of the system was measured.Downstream, longitudinal and corrugated fins increase the current supply to the electrolyzer module by cooling the PV panel.Based on the results of the PV/T (with wavy ends), the PV/T with longitudinal ends, the PV/T and the PV, the hydrogen generation rate was 13.5 mL/min, 12.1,9.5 mL/min, and 7.8 mL/min, respectively.[116]2022 ChinaMonocrystalline Water cooled PV/T20.58%18.49%Solar energy offers great potential for producing hydrogen.Using the hybrid hydrogen production method, 18.49% of hydrogen was produced efficiently.Photovoltaic energy generated increases when the photovoltaic module’s temperature is lowered, increasing the system’s efficiency and increasing electrolysis hydrogen production.[117]2022 IranWater cooled PV/T&PV/T-PCM water cooled 6.6%66.6%An analysis is conducted of the performance of the PEMEC, powered by a PV/T system.In addition to providing electrical power to the PEMEC, the PV/T system also preheats the feed water.PV/T-TEG-PEMEC produces hydrogen at a higher rate than other systems based on the results obtained.Hydrogen production from the PV/T-PEMEC system is negligibly affected by its integration with PCM.[118]2023 TurkeyWater cooled PV/T139.7%128.9%PV/T systems generate more electricity when they flow more cooling water, thereby producing more electricity.The payback time of PV-T was reduced from 8,093 to 7,734 years by increasing the cooling water mass flow rate.Because the system takes advantage of heat, electricity and hydrogen are generated more during the summer months.A higher ambient temperature also results in a decrease in electricity and hydrogen production by the system.Increasing the wind speed from 1 m/s to 5 m/s produced more electricity and hydrogen on the PV-T roof.[119]2023 EgyptPolycrystalline Air and water cooled PV/T 5%42%By using water and air as coolants at a flow rate of 40 L/h, the average daily PV surface temperature was reduced by 16.60% and 8.50%, respectively.When cooled by water instead of air, hydrogen production also increased daily.

Table 2 (continued)

Ref.No.Year Location PV typePV/T system typeEfficiency increase rate Produced hydrogen increase rate Critical findings[120]2023 ChinaMonocrystalline 16%8.3%Because nanofluids have a lower module temperature, the electrical and thermal efficiency of PVs increases.The use of nanofluids also increases hydrogen production rates.Using a nanofluid flow rate of 0.012 kg/s with hydrogen production at 17.4 mL/min, a maximum thermal efficiency of 33.4% was achieved.[121]2023 IndiaPolycrystalline ZnO Nanofluid cooled PV/T Nanofluid cooled PV/T8.6%24.2%An air and water PV/T system is compared with one using nanofluids as coolants.Nanofluids at optimal concentrations are shown to greatly enhance system performance compared to water and air.Electrical and thermal efficiency were higher with a nanofluid concentration of 1.2 g/s than with water(8.6%and 33.3%,respectively).At the same concentration, hydrogen mass flow rate also was increased.[122]2023 IranWater cooled PV/T70.19%61.9%Based on weather conditions and consumption patterns in Dubai and Barcelona, the proposed system reduced total electricity consumption by 72.3% and 64.6%, respectively.With this system,Dubai’s environmental damage was reduced by 29.2%, while Barcelona’s was reduced by 8.1%.[123]2023 ChinaGaInP/Water cooled PV/T65.7%14%With spectral beam splitting of TiO2 suspension,the CPV/T hydrogen system produces hydrogen as well as decreasing cell temperature by 32.8%,increasing electric power by 65.7%, and reducing cell area to at most 49%.Increasing photoelectric performance was achieved by reducing heat loss.With 150 ppm TiO2 loading,the proposed system is capable of producing hydrogen at a solar to hydrogen conversion efficiency of 14%.[124]2023 IranVariable fluids (R141b,R23,and Isobutane)PV/T GaAs/Ge triplejunction PV cell 40%37.5%Liquid hydrogen and electricity were generated using solar energy technology.According to the results, the work consumed in the fluidization cycle is 54,301 kJ/kg H2.The maximum power is achieved with the highest surface of the panels,i.e.4550 kW, as the size of the solar panels grows.Aside from 56.3% efficiency, 13 kg/s of liquid hydrogen and $15.1/GJ cost, the system also has 56.3% efficiency.[125]2024 ChinaPolycrystalline Cooled by nano-PCM8%22%Adding nanoparticles to PCM caused a significant decrease in the PV panel temperature, and using nanofluids can reduce the cell temperature by at least 8°C.The panel temperature decreased as the mass flow rate increased.As different mass flow rates were increased, hydrogen flow rates increased with increasing cooling of the photovoltaic module.

Employment opportunities can be created by developing renewable hydrogen production facilities and supply chains.This includes jobs in manufacturing,construction,installation,operation,and maintenance of hydrogen production infrastructure.Green hydrogen production can contribute to local economic development by generating new jobs and fostering skill development in the renewable energy sector.

The production of green hydrogen can lead to increased energy independence by reducing the use of fossil fuels and imported energy.As a result, national security enhances and vulnerability to geopolitical tensions related to energy supply will be reduced.Diversifying energy mixes and reducing finite resource dependency are possible with hydrogen produced from renewable sources.

Green hydrogen is produced using renewable energy sources such as solar, wind, or hydroelectric power,resulting in minimal greenhouse gas emissions.Its production can contribute to reducing GHGs and combating climate change.As a clean energy carrierw,using green hydrogen can help mitigate air pollution and improve overall air quality, benefiting public health and well-being.

The establishment of green hydrogen production facilities often involves community engagement and collaboration.Companies and governments need to work closely with local communities to address any concerns,provide information,and ensure transparency throughout the process.Engaging stakeholders in the decisionmaking process provides assistance in building public acceptance that support green hydrogen proposals.

In order to produce green hydrogen,new technologies need to be developed and deployed.This presents opportunities for research and development, fostering technological advancements and creating a skilled workforce.It is possible to develop efficient and costeffective green hydrogen production methods by collaborating with industry, academia, and research institutions.

Renewable hydrogen production can contribute to social equity by providing access to clean and affordable energy.It has the potential to bridge energy access gaps, particularly in remote or underserved communities.By enabling decentralized energy production and distribution, green hydrogen can empower communities to meet their energy needs sustainably and reduce energy poverty.

Green hydrogen production has gained global attention, leading to increased international collaboration and partnerships.This cooperation can foster knowledge exchange, capacity building, and mutual support in developing green hydrogen infrastructure.The green hydrogen production has the potential to bring numerous social benefits, including job creation,energy independence, environmental sustainability,community engagement, technological advancements,social equity, and international collaboration.Green hydrogen production offers several environmental benefits compared to conventional hydrogen production methods as illustrated in Fig.13d.The key environmental aspects of renewable hydrogen production:

Hydroelectric power,solar power,and wind power can all be used to produce green hydrogen.The green hydrogen production process emits very little to no greenhouse gases, unlike conventional hydrogen production, which relies on fossil fuels.This significantly reduces CO2 emissions and helps combat climate change.

Green hydrogen production does not produce hazardous air pollutants, such as ‘‘sulphur dioxide”, ‘‘nitrogen oxides”, or ‘‘particulate matter”.By using renewable energy sources,the harmful effects that conventional energy production has on human health and the environment are reduced.

The electrolysis process used in green hydrogen production typically requires water as an input.However,when renewable energy sources are used, water consumption can be significantly lower compared to other hydrogen production methods.This is important as water scarcity is a growing concern in many regions worldwide.

Green hydrogen production can contribute to resource efficiency by utilizing renewable energy sources more effectively.The system allows surplus renewable energy to be converted and stored instead of being wasted.Capturing and converting excess energy into green hydrogen, it enables the use of renewable resources efficiently and helps balance the intermittent nature of renewable energy generation.

Unlike some conventional energy production methods, green hydrogen production does not require extensive mining or drilling operations that can cause land degradation and habitat destruction.The production facilities for green hydrogen can often be built on existing infrastructure or repurposed industrial sites,minimizing the need for additional land use.

Green hydrogen production can be integrated into a circular economy approach, promoting resource recovery and reuse.For example,by capturing and utilizing waste heat from industrial processes or power generation.There are several steps that can be taken to increase the energy efficiency of hydrogen production.Furthermore, hydrogen production can reduce carbon emissions further by utilizing carbon capture and utilization (CCU) technologies.

Green hydrogen production preserves ecosystems and biodiversity by reducing greenhouse gas emissions and air pollution.Despite the significant environmental benefits of green hydrogen production, it is crucial to consider the life cycle impacts of the entire hydrogen value chain,including resource extraction,transportation, and end-use.Ensuring sustainable practices throughout the entire process is key to maximizing the environmental benefits of green hydrogen production.

Table 3 Some research dealt with the Life Cycle Assessment of hydrogen production using PV/T.

Ref.No.LocationYearUsed systemSystem’s LCACritical findings[138]Canada2007PV electrolyzing; Wind electricity electrolyzing Wind energy for hydrogen production is expensive compared to natural gas.Hydrogen production via natural gas is significantly cheaper than wind and solar energies, with wind and solar electricity costs 2.25-5.25 times higher than natural gas.[143]Germany2019PEM water electrolyzer systemThe proposed system is a promising technique compared to steam methane reforming Hydrogen production by the proposed technology can reduce carbon dioxide emissions by 75% compared to its production by the technology of steam methane reforming if the system is powered exclusively by electricity produced from a renewable energy source.[144]Iran2020Solar-based hydrogen production(solar thermal electrolysis).The results show that the GHG abatement costs are $0.786/kg CO2 and $1.37/kg CO2 for PV and solar thermal electrolysis, respectively.The greenhouse gas emissions associated with building solar power plants are much higher than those produced by current hydrogen production units.However, solar hydrogen production technologies cannot compete economically with fossil fuel methods.[145]Canada2021- Green hydrogen (produced by renewable energy)- blue hydrogen (hydrogen from fossil fuels with CO2 emissions reduced by the use of Carbon Capture Use and Storage)- Aqua hydrogen (Hydrogen is extracted from oil sands (natural bitumen) in Canadian oil fields at very low cost and without carbon emissions)Aqua hydrogen has lower hydrogen production cost than renewable energy production techniques but higher than steam methane reforming Low-carbon hydrogen technologies remain immature, requiring increased R&D, infrastructure, and production.Long-term policies are vital to support decarbonization and establish robust distribution systems.[146]Turkey2023Organic Rankine cycle (ORC) and hydrogen production system integrated into medium temperature solar collector The system’s exergoenviroeconomic and exergoenvironmental analyses are 71.48 kgCO2/kWh and $0.139/kgCO2,respectively,with a sustainability index of 1.21.[147]India2024solar PV-PEM electrolysis and alkaline water electrolysis The energy and exergy efficiency of the whole system is calculated as 39.01%and 17.37%, respectively For hydrogen production, the energy payback time (EPBT) and energy return on investment (EROI) are 7.7 years and 3.0 for solar PV-PEM,and 7.45 years and 3.11 for solar PValkaline electrolysis.[148]China2024Hydrogen utilization in the transportation section Using Indian grid electricity for hydrogen production emits 12 times more greenhouse gases than using solar PV electricity.To achieve the goal of deep decarbonization, a life cycle analysis model with a profit and equity optimization model in the industrial chain is proposed, which can determine the viability of any part of the industrial chain.[149]Australia2024Hydrogen production by water electrolysis Hydrogen Fuel Cell Vehicles(HFCVs)are less developed, with higher life cycle costs, emissions, and energy use.Commercial HFCVs cost nearly four times more than commercial EVs.Clean hydrogen production by water electrolysis can be considered the best available method, especially if it is based on renewable energy.Current hydrogen production technologies(including carbon capture and storage) are expected to continue to play a critical role in the transition to a low-carbon economy.

Table 3 (continued)

Ref.No.LocationYearUsed systemSystem’s LCACritical findings[150]India2024Solar PV electrolysis system with PEM and alkaline electrolyzers[151]Iran2025A trigeneration or combined cooling,heat, and power (CCHP) system incorporating solar collectors and hydrogen generation subsystems The life cycle embodied specific energy and GHG emissions are calculated as 47.7 MJ/kg H2 and 46 MJ/kg H2,3.45 kg CO2 eq.and 3.33 kg CO2 eq.respectively.The study considered the improvement in Life Cycle Assessment to depend on the solar collector area and fuel cell capacity as numerical factors, and the type of solar collector and type of cooling system as categorical factors.For India, the Energy Payback Time(EPBT)was calculated to be 1.84 years and the Energy Return on Investment(EROI) was 12.56 for solar power generation.In case of Solar PV-PEM and Solar PV-alkaline electrolysis, the EPBT and EROI for hydrogen production were 7.7 years, 3.0 years,7.45 years and 3.11 years,respectively.The proposed system reduced net electricity consumption by 58%(7,581.6 kWh) compared to the baseline system (18,051.6 kWh).Natural gas consumption was reduced by 38.2%, and life cycle cost was reduced by 39.5%.

4 Challenges and prospects of hydrogen production using PV/T technology

Hydrogen production using PV/T technology presents a unique intersection of opportunities and challenges.This section discusses the key challenges faced in the integration of PV/T systems for hydrogen production, as well as the promising prospects that arise from this innovative approach.

4.1 Challenges

A.Efficiency Constraints

The efficiency of PV/T systems is a crucial factor influencing hydrogen production.While PV/T technology can achieve higher overall efficiency than traditional PV systems as it utilizes both electrical and thermal outputs,the conversion efficiencies for solar-to-hydrogen processes remain relatively low.Typical solar-to-hydrogen conversion efficiencies are around 10%-15%, which can limit the economic viability of large-scale applications [126].

B.High Initial Investment

The capital costs associated with installing PV/T systems can be significant.These costs include not only the PV/T panels themselves but also the necessary infrastructure for hydrogen production, such as electrolyzers and storage systems.Although operational costs may decrease over time,the upfront investment can be a barrier to entry for many potential users, particularly in developing regions [127].

C.Storage and Distribution Issues

Hydrogen’s low volumetric energy density necessitates high-pressure storage or liquefaction techniques, which adds complexity and cost to the hydrogen supply chain.The current hydrogen storage and distribution infrastructures are limited, requiring substantial investment in new facilities and technologies to support widespread adoption[128].

D.Safety Concerns

Hydrogen is highly flammable and can form explosive mixtures with air, raising safety concerns during production, storage, and transportation.Implementing stringent safety protocols is essential but may increase operational costs and complicate logistics [129].

E.Dependence on Solar Irradiance

The performance of PV/T systems is inherently tied to solar irradiance levels, which can fluctuate due to weather conditions and geographic location.This variability can lead to inconsistent hydrogen production rates, making it challenging to ensure a reliable supply of hydrogen for end-users [130].

4.2 Prospects

A.Environmental Sustainability

One of the most compelling advantages of using PV/T technology for hydrogen production is its potential to reduce greenhouse gas emissions significantly.By harnessing solar energy, PV/T systems can produce green hydrogen with minimal environmental impact compared to traditional fossil fuel-based methods, thus contributing to global climate goals [131].

B.Technological Advancements

Ongoing research into improving the efficiency of PV/T systems and their integration with electrolyzers is promising.Innovations such as advanced cooling techniques(e.g., nanofluids and phase change materials) are being explored to enhance thermal management and overall system performance.These advancements could lead to higher efficiencies in both electricity generation and hydrogen production [132].

C.Policy Support and Market Growth

Governments worldwide are increasingly recognizing the importance of hydrogen as a clean energy carrier and are implementing policies to support its development.Financial incentives, subsidies, and research funding are being directed toward renewable hydrogen technologies,including PV/T systems.This supportive environment could accelerate market adoption [133].

D.Diverse Applications

Green hydrogen produced via PV/T technology has numerous applications across various sectors, including transportation(fuel cells),industrial processes(feedstock),and energy storage solutions for intermittent renewable sources.As industries seek cleaner alternatives to fossil fuels, the demand for green hydrogen is expected to grow[134].

E.Integration with Other Renewable Technologies

The potential for hybrid systems that combine PV/T with other renewable energy sources (e.g., wind or biomass) could enhance reliability and efficiency in hydrogen production.Such integrations could mitigate some challenges associated with intermittent solar energy supply while maximizing resource utilization [135].

F.PV/T Systems Conversion Efficiency for Hydrogen Production

PV/T system integrates PV technology with thermal energy, which facilitates hydrogen generation through water electrolysis.Its conversion efficiency depends on the design parameters and operation conditions of these systems.Caglar et al.[136] showed that current levels of attainable efficiency for the production of hydrogen in systems with concentrated PV/T are at 66.7% while the efficiency of standard PV/T is proclaimed to be at about 70.6% of attainability depending on the solar irradiation.

Lazaroiu et al.[137] focused on a PV/T system connected to an ethanol PEM electrolyzer-rated hydrogen production system energy efficiency of 27.8% and an exergy efficiency of 3.1%.Of note, the author mentions that system optimization could improve these parameters.Additionally, Solar Tracking systems are understood to yield,better overall system co-efficiency by 12%-20%over fixed PV systems while incurring higher fixed costs [138].

H.Environment Effect

PV/T technology reduces carbon emissions from hydrogen production by utilizing clean energy sources and improving electrical and thermal efficiency.The global warming potential of PV-based hydrogen production without PV/T technology is 3.82 to 4.83 kg CO2e/kg[139].The global warming potential of modern PV/T systems operating in contemporary supply chains using advanced PV modules is 1.75 kg CO2e/kg under suitable conditions such[139].PV/T systems combine PV electricity generation with thermal energy collection to achieve an overall system performance level of 21% according to reference [140].The output of this system requires less energy for electrolysis leading to a direct reduction in emissions.The thermal output from PV/T systems allows the electrolysis water to be preheated and thus reduces electricity requirements by 10-20 percent compared to standard PV technology[140,141].Modern solar PV modules generate 82% of the total greenhouse gas emissions in PV-based hydrogen systems,yet their current efficiency level(16.8%for polysilicon panels) reduces emissions by 30% over previous model standards[139].Combining solar/thermal with solid oxide electrolysis (SOEC) instead of proton vaporization membrane electrolysis creates hydrogen production with CO2 emissions reductions of 2.69-3.02 kg/kWh [139].Solar/thermal systems in areas with high solar irradiance levels generate 20%-30% greater yields than fixed-tilt solar arrays, resulting in improved emission reductions.Hybrid solar/thermal systems outperform stand-alone solar/thermal or wind systems, with emission reductions of 15%-25%in combined configurations[140].Grey hydrogen production by steam-methanation generates CO2 emissions of 9-12 kg/kWh of hydrogen [142].Integrated solar/thermal technology enables the production of green hydrogen with 80%-85% lower emissions than grey hydrogen on the way to net-zero hydrogen production levels [139,142].Thermal performance of solar/thermal systems reaches a 10%-15%improvement in efficiency when using nanofluids such as graphene-enhanced fluids, which simultaneously reduce emission levels [141].Solar/thermal systems can be linked to industrial applications by utilizing waste heat creating circular energy systems that reduce emissions by about 5%-10% [141].

The PV/T production method cuts hydrogen carbon emissions by 60% when using legacy PV technology and reaches 80%-85% reductions beyond fossil fuel approaches.Improved PV efficiency together with thermal energy utilization and hybrid system designs operate as vital drivers in this system.The integration of nanofluid systems with electrolyzers promotes PV/T technology to become a vital factor for developing net-zero hydrogen economies.

I.Life Cycle Assessment

This means that the environmental consequences of PV/T hydrogen production systems must be assessed using life cycle assessments (LCA).These include greenhouse gas emissions, energy used in the manufacturing process, use during operation, and final disposal.Research has also proved that the production of hydrogen from renewable electricity sources such as wind, solar, and hydroelectric power greatly minimizes emissions compared to hydrogen production from fossil fuels.

A review of PV/T systems also pointed out that while initial costs of the incorporated system can be relatively high, the gains accrued over time in the form of operational cost and emissions reduction give a better breakeven [4].Besides, new technology has improved the generation of hydrogen from the current LCOH at around 40 USD/kg in 2008 to between 1.8 and 3.4 USD/kg in the current generation systems [1374].Table 3 lists some of the up-to-date works in this regard from the literature.

The contrastive analysis of the paragraphs given and Table 3 to be included can be made based on the key points concerning the benefits of integrating PV/T systems into hydrogen production focusing on the LCA.

J.Summary of content of the descriptive paragraphs

Environmental assessment:The overall impacts of PV/T hydrogen production systems on the environment are evaluated by conducting life cycle assessments,which consider greenhouse gas emissions, energy consumption during and throughout the manufacturing process, operational stage, and disposal phase of the systems.

Emission reduction: Renewable-based hydrogen production from wind, solar, and hydropower systems also shows much less emissions than hydrogen production from fossil fuels.

Economic viability:Because the initial costs of a PV/T system may at first be high, the long-term savings in terms of operation costs and low emissions the break-even is favorable.

Cost reduction over time:There is a tremendous scope to bring down the LCOH further: it has shrunk from about US$ 40 per kg in 2008 to a range of US$ 1.8-3.4 per kg for today’s systems.

K.Insights from Table 3

Although Table 3 contains data or results from various studies focusing on the life cycle analysis of hydrogen production using a variety of renewable and nonrenewable energy systems, evidence supporting the advantages of using PV/T systems for hydrogen production includes:

1) Life cycle assessments: In both paragraphs and Table 3, the LCA has been emphasized as a method of evaluating the environmental effects of various hydrogen production processes.They can also be regarded as autothermal which supports the view that autothermal systems are more sustainable.

2) Technological advances: This continuously reducing LCOH shows PV/T systems are economically improving and should be adopted even more because of the further impact of emissions.

3) Long-term savings: The tautology that initial cost is recovered by operational cost saving is likely to be reflected in measures of cost benefits as shown in Table 3 displaying different such studies.

In conclusion, the above gives clear background evidence to support that PV/T systems present environmental and economic benefits in hydrogen production than fossil fuel-based methods.

L.Technical and Economic Feasibility

Technical feasibility and project costs are the most important aspects of any business proposal.The technical feasibility of solar PV/T systems is evident from the fact that they provide electrical and thermal energy for processes such as electrolysis.To enhance energy recovery and its use to enhance hydrogen generation, the integration of ORC with solar PV systems has been proposed[136].

Economically, feasibility is influenced by several factors:

1) Capital costs:Costs can be high,especially for larger systems such as those of concentrated solar PV systems, in the early stages of implementation [152].

2) Operating costs:The cost associated with the maintenance and operation of solar PV systems is generally lower than that of conventional means of operation.

3) Government incentives: It is unequivocal that subsidies and incentives provided to renewable energy sources make their operation and development more economically feasible [153].

According to evaluations, the high rates of hydrogen production using hybrid PV systems show that they combine low dependence on grid electricity,making them suitable for off-grid applications.

5 Critical review

Recent years have seen a significant increase in the use of PV/T in green hydrogen production.While there are potential benefits to this approach, it is important to critically review its feasibility and effectiveness.Green hydrogen production with PV/T systems is characterized by their ability to produce electricity and heat at the same time.Photovoltaic modules generate electricity from solar energy, which is used to power hydrogen electrolyzers.Meanwhile, PV modules generate waste heat that can be used for a variety of thermal applications such as water heating and space heating.However, there are several challenges and limitations that need to be addressed.

One major concern is the relatively low efficiency of PV or ST separately compared PV/T.The combination of PV and ST components in a single PV/T may lead to compromises in both electricity generation and thermal collection.In this way,overall system effi-ciency can be increased, and optimal performance can be achieved.

Another critical aspect is the cost-effectiveness of PV/T systems.The incorporation of additional ST components in PV modules adds complexity and cost to the system.The balance between the added cost and the benefits gained from simultaneous electricity and heat generation needs to be carefully evaluated.

For the green hydrogen market to be viable,hydrogen production through electrolysis must be competitive with other energy sources.

Furthermore, it is challenging to produce continuous hydrogen from solar energy due to its intermittent nature.Solar availability varies with weather conditions and diurnal cycles,which affects the overall production capacity and requires efficient energy storage or grid integration solutions.Because sunlight is intermittent,the PV/T system may not be fully utilized during low solar radiation periods.

Integration and system optimization are crucial aspects to consider.The sizing, design, and control strategies of the PV/T system need to be carefully planned to maximize energy production, storage, and utilization.Efficient management of excess electricity and heat during peak production periods is essential for system reliability and performance.

While the concept of incorporating PV/T systems into the green hydrogen production process is promising,it is important to address technical,economic,and operational challenges.

PV/T systems for green hydrogen production need to be improved in terms of efficiency, cost-effectiveness,and overall performance.Critical evaluation and optimization of system design, control strategies, and energy management are crucial for maximizing the benefits of PV/T integration in the green hydrogen sector.

There are several innovative technologies being worked on to produce hydrogen using solar/thermal systems, but high costs remain a barrier to efficiency.Key developments in this area include the incorporation of novel cooling technologies into systems such as liquid nano-cooling and phase change materials that enhance the thermal and electrical efficiency of solar/thermal systems.These technologies can control heat evenly in a way that improves energy production and the overall efficiency of hydrogen production methods.Furthermore, the storage and distribution system also increase costs and adds another layer that limits the applicability of these systems.However,there are still other challenges to finding ways to improve the designs and efficiency of solar PV systems through technology and scale.Eliminating these high costs is crucial to improving the performance of solar PV systems in producing green hydrogen sustainably.

5.1 Technology readiness levels

Technology Readiness Levels is a hierarchical scale used to measure the preparedness of the technology from the basic research phase to the ready products phase.The TRL scale consists of nine levels:

TRL 1: The following basic principles were observed and reported:

TRL 2: Creation of a concept or an application of a particular type of technology.

TRL 3: Both, analytical and experimental validation of the proof of concept done.

TRL 4: Technology that has undergone the test at a laboratory setting and proved worthy.

TRL 5: Reliability through credibility of a validated technology in a relevant setting.

TRL 6:Field observations such as model or prototype demonstration.

TRL 7: Simulation of prototypes in actual working conditions.

TRL 8:Technology at its final physical and technological stage of testing and demonstration.

TRL 9: Real technology as defined by the successful performance of space missions.Actual technology of existing space industry.

Emphasizing and summarizing TRLs in a manuscript serves several purposes:

Clarity on Maturity: The author helps the readers to grasp how developed the technology is so they can decide on aspects such as its practicality or the level of impact it will possibly have.

Funding and Development Decisions: Some funding agencies use TRLs to evaluate the applicant’s qualifications for funding, and therefore, authors need to report it correctly.

Guidance for Future Research:The TRLs can be summarized to identify gaps where future technology development efforts are needed and what efforts should not be pursued.

Therefore, the provision of an understandable TRL table relevant to the discussed technologies forms an integral component of the manuscript aimed at presenting the current status and application readiness of such innovations.

5.2 TRL technologies of PV/T incorporation in the hydrogen production process

A.Photovoltaic/thermal systems

TRL level: PV/T systems are at a higher level of technology readinessprobably a TRL level between 6 and 8 as such systems have been proven in the laboratory as well as in practical use.What distinguishes these systems is that they provide power generation through solar photovoltaics and heat generation.Due to their solar energy effi-ciency, they are praised for reducing energy costs and are also known to have significantly reduced greenhouse gas emissions.

B.Hydrogen production methods

The current manuscript described different methods for hydrogen production, each with its own TRL status:

Steam Methane Reforming (SMR)

Level: TRL 9.This is a mature technology that is commonly used in hydrogen production.This process involves the use of a catalyst to convert methane and steam into hydrogen and carbon monoxide respectively.

Electrolysis of Water

TRL level:TRL 6 to TRL 8 depending on the type of electrolysis technology.This method involves water separation into hydrogen and oxygen by electrical means.The different types include:

Alkaline water electrolysis:A sophisticated technology used by industries.

Solid oxide electrolysis: High efficiency, however, its use requires high temperatures.

Photoelectric water splitting (PEC): This work is still in progress and, therefore, is tentatively described as having a lower TRL due to its developmental nature.

Biomass gasification

TRL level: TRL 6 to TRL 7,because the subject is still under research, but it has an active and practical application.It selects materials such as coal and other organic materials and converts them into synthetic gas from which other processes can be used to extract hydrogen.

C.Integration of PV/T systems with hydrogen production

Continuously integrating PV/T systems into hydrogen production processes improves the efficiency and sustainability of the entire process and reduces the levelized cost of hydrogen (LCOH).This integration has a higher levelized cost due to the different applications, which have revealed operational efficiency.This work usefully emphasizes the need to assess the level of technical maturity of advanced technologies when discussing such technologies as,for example,integrated solar PV systems and hydrogen generation.Through these brief levels, readers can appreciate the level of maturity and potential of these technologies in promoting sustainable energy solutions.The configuration of solar PV systems has been confirmed as one of the most effective ways to improve green hydrogen production by reducing the negative environmental impacts caused by conventional fossil fuel-based methods.

5.3 Case studies in hydrogen generation through PV/T systems

During the previous period,there were several pilot and commercial projects related to the subject of the review,including:

A.Hydrogen Economy Pilot Project in Rugao City,China

This project aims to develop Rugao City,China,into a‘‘hydrogen city”,where hydrogen production technologies are adopted and used in the manufacturing and automotive industries.The project is entirely based on introducing new ideas and inventions involving innovation in hydrogen production from renewable energy.The project will also inform and educate the public about the technical specifications required for the use of hydrogen [154].

The Rugao Hydrogen Economy Pilot Project(aimed at developing a ‘‘hydrogen city” in Rugao) has produced many results since 2009.The following are the initial results:

Roadmap for the development of the hydrogen economy: Through the experiences accumulated in the course of the project, key strategies and objectives for the development of the hydrogen economy in Rugao have been proposed.A detailed plan for the deployment of hydrogen technologies has also been developed [154].

Proof of feasibility: The project has achieved its main purpose of demonstrating the feasibility of producing hydrogen in various and multiple ways, which has given credibility to the large-scale production of hydrogen in urban centers [155,156].

Deployment of fuel cell vehicles (FCVs): The project included a special part in which an energy demonstration was conducted by operating five fuel cell buses and two fuel cell cars to demonstrate the success of hydrogen applications in transportation.These two objectives were designed to enhance and improve public transportation while reducing the use of petroleum products and maintaining a cleaner environment[156].

Cogeneration systems using fuel cells:One of the most important achievements of this project is the application of cogeneration systems using fuel cells for buildings.This work demonstrated that hydrogen can work not only in transportation but also in heating and electricity applications in buildings in urban structures[155,156].

Technical standards and policy framework: The project supported the development of relevant technical standards as well as a policy framework for hydrogen production, storage and transportation.These legislations precisely define the methods, technologies and safety of hydrogen production and use inside and outside the city [155,157].

Public awareness and stakeholder engagement:One of the objectives of this project was to raise the knowledge and awareness of the city’s residents and key stakeholders about various hydrogen technologies, in order to create favorable conditions for further growth of the hydrogen market [155,156].

B.National Green Hydrogen Project in India

India’s National Green Hydrogen Mission was recently unveiled on January 4, 2023.The Indian government has approved three large-scale pilot projects to date,including a 3,200-tonne per day plant led by SAIL.The main objective of these initiatives is to demonstrate the technical and economic feasibility of using green hydrogen in the mentioned sectors.The project also aims to establish logistics services related to its application in some of the most sensitive sectors [158,159].The key deliverables of the project since its inception are as follows:

Production capacity targets: The main mission of this project was to establish a green hydrogen production capacity of at least 5 million metric tons per annum by 2030 with the potential to expand up to 10 million metric tons.This increase is dependent on market development [160,161].

Financial investment: This mission involves a huge capital investment of Rs.19,744 crore (US$2,280,000,000).The plan is based on hydrogen production linked to multiple schemes and the development of a green hydrogen ecosystem [160,161].Thus, the mission is expected to help reduce global greenhouse gas emissions by about 50 million metric tons per annum by 2030, thereby supporting India’s major climate goals [161].

Sectoral applications:One of the most important tasks of this mission is to market green hydrogen in sectors such as ammonia manufacturing, petroleum refining,and steel manufacturing in order to reduce dependence on fossil resources [160,161].

C.HyDSerbia Project

The Republic of Serbia is implementing a pilot project for green hydrogen, the first of its kind in the Balkans,called HyDSerbia.The German government has also funded the project to include feasibility studies for production, transportation, and logistics services related to the export of green hydrogen [162].Since the launch of the HyDSerbia project it has achieved a lot in a short time.Here are the main results:

Financing and support: Germany has financed the project with 3.5 million euros.This funding is intended to promote and support hydrogen production technologies in Serbia, highlighting these efforts and promoting them to become international and global[163,164].

Integrated approach to hydrogen production: The develop a final vision for the implementation of an integrated project for the production of green hydrogen that ensures the efficient and safe use of renewable energy.

Technological progress: This project can position Serbia as a candidate to be a Balkan leader in green hydrogen technology [163].

Development of a pilot plant:This facility will also be used to test different technologies in hydrogen production, storage, and marketing before the full deployment of such facilities on a larger scale across the country [164].

Economic and environmental impact:This project will also inevitably impact the environmental conditions resulting from burning fossil fuels for energy generation [165].

Public awareness and participation: The government seeks to educate decision-makers in the local community and the public about the need to embrace green hydrogen as a key to supporting citizens in the project[163].

D.Development of Electrolysis Technology in South Africa

The South African government has begun to promote the shift towards electrolysis technologies for green hydrogen production[165].The following are the key outcomes:

Implementation of the Hydrogen Society Roadmap:In October 2020,the South African government developed a Hydrogen Society Roadmap.This roadmap provides a long-term vision for the adoption of hydrogen in the country’s energy sector.The project also aims to create, localize, manufacture, and establish a hydrogen supply infrastructure [166].

Production capacity targets: The South African government aims to to generate 500,000 tons of green hydrogen per year by the end of 2030.This plan includes the installation of electrolysis facilities and the government’s target of achieving 10 GW of capacity in the Northern Cape by 2030 and 15 MW by 2040.Achieving these ambitious goals would make South Africa a world leader in green hydrogen production[166].

Job Creation: The South African government expects that the implementation of this Green Hydrogen Society Roadmap will create around 20,000 direct jobs within a few years.This number could increase to around 30,000 jobs annually by 2040.This will boost the South African economy and reduce unemployment[166].

Cost Competitiveness: The South African Roadmap aims for the country to be able to produce green hydrogen at a competitive cost of $1.60 per kilogram by 2030, making it among the cheapest in the world.Reducing this cost of production is important for raising capital and creating an efficient hydrogen economy in this country [166].

International Cooperation and Financing:This project received external support from the German Development Bank.The bank financed this program with€200 million [166].

Focus on decarbonization: This roadmap vision focuses on using hydrogen in important areas such as energy,mobility,and manufacturing instead of fossil fuels by strategies to address climate change [166].

6 Conclusion

The adoption of combined systems of electricity generation such as PV/T in green hydrogen offers a prospect for future energy systems.This approach not only contributes to the improvement of reactions that produce hydrogen in parallel with electricity and heat but also cuts down greenhouse gas emissions.Consequently, the integration of an additional system of utilizing solar energy PV/T systems makes efficient use of the resource, therefore reducing the dependence on fossil fuels and decreasing the carbon footprint of the energy sector.

Studies suggest that incorporating PV/T systems has the potential to increase the efficiency of the energy conversion procedure with regards to the electrical as well as the thermal performance that is important in hydrogen production.The availability of time for pre-heating water for electrolysis using thermal energy from PV/T system decreases the energy input needed for the process hence minimizing the impacts borne by the environment.In addition, these hybrid systems can assist in reducing the Levelized Cost of Hydrogen(LCOH)and;thus,bringing about economic sustainability.

However, there are problems with adapting these systems for industrial use at large and also to meet specific requirements.It is also clear that there is need to carry out further research and innovations as it relates to the PV/T systems designed for hydrogen production since there are some issues that may arise as it is being implemented.Finally, using PV/T technology to develop green hydrogen production contributes not only to progress in renewable energy technologies but also to the global effort to combat climate change and move toward a sustainable economy.

CRediT authorship contribution statement

Hussein A.Kazem:Writing-original draft.Miqdam T.Chaichan: Writing - original draft.Ali H.A.Al-Waeli:Writing - original draft.K.Sopian: Writing - original draft.Waheeb E.Alnaser: Writing - review & editing.Lawrence Kazmerski: Writing - original draft.Naser W.Alnaser: Writing - original draft.

Declaration of competing interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: W.E.Alnaser reports article publishing charges is provided by Arabian Gulf University.W.E.Alnaser reports a relationship with Arabian Gulf University that includes:employment.There is no conflict of interest

Acknowledgments

Thanks for partial funding support from Arabian Gulf University to cover any necessary publication fees.