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The world population and consequently the global need for food continue to grow. At the same time, areas will be used to generate clean electricity to cope with climate change and global warming. The combination of crop production and solar photovoltaics in the form of ""agrivoltaic technology"" offers advantages for both sides that provide an adequate, resource-efficient solution to the persistent problem of competition for arable lands. The implementation of agrivoltaic systems has been exponentially increased in recent years and reached the global installed capacity of 2.8 GW in 2020 from the initial capacity of 5 MW in 2012. The agrivoltaic systems installed worldwide mostly employ conventional opaque photovoltaic (PV) modules, causing a change in the microclimate under the panels that become critical when shading ratios are high. Semi-transparent PV (STPV) modules have been recently employed to mitigate this issue which is profoundly studied in this research by considering the use of semi-transparent technologies based on crystalline silicon (c-Si), thin-film photovoltaics, organic PVs (OPVs), dye-sensitized solar cells (DSSCs), concentrating PVs (CPVs), and luminescent solar concentrators (LSCs) in open (arable farming lands) and closed (cultivation greenhouses) agrivoltaic systems. The results indicated that c-Si STPV modules have the highest share of employment in agrivoltaic systems due to their extreme benefits of low costs, high stability, and high efficiency in comparison with other technologies, while in contrast, the use of thin-film STPV modules have been rarely reported in the literature. Additionally, STPV modules using OPVs and DSSCs offer the capability to achieve wavelength-selective transparency, causing the photosynthetic active radiation to pass through while the remained spectrum is utilized to generate electricity. Other potential solutions come from CPVs and LSCs, in which, diffuse light is available for the growth of cultivated plants, while direct concentrated sunlight can generate electricity. Although STPV modules are proven as a feasible solution for use in agrivoltaic systems, still more developments are required in terms of the modules' efficiency enhancement and costs reduction, while more detailed research is required to observe the response of cultivated plants to make this technology a viable sustainable solution in the future.

International audience; As the world’s population grows, current agricultural activities are putting enormous strain on the climate, including deforestation, excessive water use, and pesticide runoffs. These stresses are expected to increase in the coming future as more food products are needed. One promising method to reduce the adverse impact on the environment is greenhouse-based farming, which can enhance land-use efficiency and water consumption. The major limitation of the greenhouse is the high energy demand in a constrained space. Solar energy has shown a promising approach for integration with agricultural greenhouses in recent years. The developments of greenhouses integrated with various solar energy technologies including photovoltaic (PV), photovoltaic-thermal (PVT), and solar thermal collectors are discussed in this chapter. The results indicated that PV modules installed on greenhouse roofs or walls cause shading and, in some cases, have affected the growth trend of cultivated crops inside. The PVT modules are more efficient at producing both heat and electricity, while higher performance values are reported for greenhouses integrated with solar thermal collectors especially in moderate climate conditions. Additionally, storing thermal energy has shown an improvement in the profitability of solar greenhouses by extending the period of solar heat availability. Also, the most commonly used mathematical models describing the thermal behavior of solar greenhouses as well as their economics are explored and discussed. In the end, various commercial solar greenhouse implemented around the world are introduced.

Phase change materials (PCM) are promising technology to store thermal energy at a constant temperature. A large amount of energy can be stored or released in latent heat form during the transition of material from one phase to another. Despite the great benefits, most PCMs have their own limitations i.e., low phase change enthalpy, poor specific heat and thermal conductivity, supercooling, volume change, phase segregation, etc. Consequently, efficient thermal energy storage requires improving the thermophysical properties of PCMs. The present study is a comprehensive review of existing techniques for PCMs thermophysical properties enhancement. The research progresses on adding zero, one, two, and three-dimensionally structured additives to PCM is assessed to improve the thermal transport by enhancing the PCM effective thermal conductivity. The enhancement of latent heat of fusion and specific heat using various additives is also discussed. Further, the latest techniques on supercooling and phase segregation reduction are also presented. Last, the modelling of the novel composite materials formed by combining a PCM with other materials is presented. Despite the fact that the majority of these methods are still in the research and development stage, some of them have the potential to be commercialized in the near future. Reliable and efficient PCMs are exceptionally useful for storing solar energy and industrial waste heat, especially for constant temperature applications.

Building integrated photovoltaics (BIPV) coupled with phase change materials (PCM) (BIPV/PCM) provide opportunities for reducing the photovoltaic (PV) panel temperature to increase the overall efficiency of the BIPV, while also transferring the extracted heat for building energy load management. A comprehensive numerical study is conducted to simulate the effects of different BIPV design parameters namely, BIPV height ( H ), air gap between BIPV/PCM and wall ( δ Air ), PCM thickness ( δ PCM ), and air mass flow rate ( m ) on the maximum PV panel temperature, the power production by the PV, and the energy extracted by the air. Optimum BIPV/PCM designs are derived from the studies for three different phase change materials, with the goal of maximizing the total energy from photovoltaics (EPV) and extracted heat (Eair), subject to the constraint of keeping the maximum PV panel temperature to within acceptable values. From the obtained results it is concluded that for the selected range of parameters, the optimum values of δ PCM , H , δ Air and m are, respectively, 0.04 m, 3 m, 0.02 m and 0.18 kg/s for maximizing EPV and 0 m, 3 m, 0.08 m and 0.091 kg/s for maximizing Eair without any constraints.

International audience; Phase change materials have been overwhelmingly used for thermal energy storage applications. Among organics, fatty acids are an important constituent of latent heat storage. Most of the saturated fatty acid PCMs so far studied are either unary or binary constituents of pure fatty acids. In the present study, ternary blends of saturated fatty acids i.e., capric, lauric, myristic, stearic, and palmitic acids have been developed with different weight proportions. A series of 28 ternary blends viz. CA-LA-MA, CA-LA-PA, CA-LA-SA, CA-MA-PA, CA-MA-SA, and CA-PA-SA were prepared and analyzed with differential scanning calorimetry, thermal gravimetric analysis, and Fourier transform infrared spectroscopy. DSC analysis revealed that the prepared materials lie in the 15–30 °C temperature range. Also, 300 thermal melt/freeze cycles were conducted which showed ±10% variation in terms of the melting peak for most of the PCMs, with the average latent heat of fusion between 130 and 170 kJ/kg. The TGA analysis showed that most of the PCMs are thermally stable up to 100 °C and useful for medium-low storage applications, and FTIR analysis showed that the materials are chemically stable after repeated thermal cycles. Based on cycle test performances, the developed materials were found to be reliable for long-term use in building and photovoltaic applications.

The application of thermal energy storage using thermochemical heat storage materials is a promising approach to enhance solar energy utilization in the built environment. Potassium carbonate ( K 2 C O 3 ) is one of the potential candidate materials to efficiently store thermal energy due to its high heat storage capacity and cost-effectiveness. In the present study, a 3-dimensional numerical model is developed for the exothermic hydration reaction of K 2 C O 3 . The heat produced from the reaction is transferred indirectly from the thermochemical material (TCM) bed through the walls of the honeycomb heat exchanger to a Heat Transfer Fluid (HTF). A parametric study is conducted for varying geometrical parameters of the honeycomb heat exchanger. The obtained results indicate that the reaction rate and heat transport in the TCM bed strongly depends on the geometrical parameters of the heat exchanger. Reducing the cell size of the honeycomb heat exchanger up to a certain level provides better thermal transport as well as improved reaction rate of the TCM bed. The results of this study provide detailed insight into the heat release processes occurring in a fixed bed of K 2 C O 3 . The study is useful for designing and optimizing thermo-chemical energy storage modules for the built environment.

International audience; Thermal energy storage devices are vital for reducing the inconsistency between energy supply and demand as well as for enhancing the performance of solar thermal systems. The present study investigates the melting process in metallic honeycombed heat exchangers filled with n-octadacane as phase change material (PCM). Further, a parametric study is conducted for four different honeycomb cell sizes, fin thicknesses, and angles of inclinations of the computational domain. The findings are described in the form of heated surface average temperature variation, melt fraction of the PCM, and thermal energy stored. Results show that the honeycomb fin structure considerably improves the heat transfer in the PCM. Further, it was observed that the honeycomb cell size and fin thickness greatly influence the variation of the average front surface temperature, melt fraction, and energy storage rate, whereas the inclination angle doesn’t have a significant effect when cell size is less than 0.01 m. From the study, it was also observed that when the computational domain is horizontal without honeycomb cells, the pure conduction in the PCM results in much higher front surface temperature, which is greatly reduced in presence of the honeycomb cells.

This paper analyzes a novel, cost-effective planar waveguide solar concentrator design that is inspired by cellular hexagonal structures in nature with the benefits of facile installation and low operation and maintenance cost. A coupled thermal and optical analysis of solar irradiation through an ideal hexagonal waveguide concentrator integrated with a linear receiver is presented, along with a cost analysis methodology, to establish the upper limit of performance. The techno-economic model, coupled with numerical optimization, is used to determine designs that maximized power density and minimized the cost of heat in the temperature range of 100–250 °C, which constitutes more than half of the industrial process heat demand. Depending on the incident solar irradiation and the application temperature, the cost of heat for the optimal design configuration ranged between 0.1–0.27 $/W and 0.075–0.18 $/W for waveguide made of ZK7 glass and polycarbonate, respectively. A techno-economic analysis showed the potential of the technology to achieve cost as low as 80 $/m2 and 61 $/m2 for waveguide made of ZK7 glass and polycarbonate material, respectively, which is less than half the cost of state-of-the-art parabolic trough concentrators. Overall, the hexagonal waveguide solar concentrator technology shows immense potential for decarbonizing the industrial process heat and thermal desalination sectors. Published version

Liquid infused surfaces (LIS) achieve non-wetting properties through asperity structures containing pockets of a lubricating liquid rather than air. Although studies have demonstrated several potential applications of LIS, the effect of liquid infused texture on the flow of liquid in microchannels has not been systematically addressed. The present work focuses on the effect of liquid-infused texture geometry and the infused liquid properties on the flow characteristics of a bulk fluid in rectangular and round microchannel geometries. Considering four different textured geometries of transverse ridges, longitudinal ridges, in-lined square posts and staggered squares, a detailed parametric study is presented to assess the resulting drag reduction and friction factor, expressed in terms of the Poiseuille number, on the flow in microchannels. The effect of geometrical parameters is investigated for different asperity solid fraction ( ϕ s ), asperity height ( h s ) and channel thickness ( H ) or tube diameter ( D ), while the effect of the infused fluid is studied in terms of a ratio of its viscosity relative to the viscosity of the flowing bulk fluid. Based on the results of the parametric study an extension of the conventional Moody diagram for non-wetting surfaces is developed. Further, a design of experiments study is conducted to relate the drag reduction and Poiseuille number to the various governing parameters, using which conditions that maximize drag reduction are identified.

Floating Photovoltaic (FPV) is an emerging technology that has experienced significant growth in the renewable energy market since 2016. It is estimated that technical improvements along with governmental initiatives will promote the growth rate of this technology over 31% in 2024. This study comprehensively reviews the floating photovoltaic (FPV) solar energy conversion technology by deep investigating the technical advancements and presenting a deliberate discussion on the comparison between floating and ground-mounted photovoltaic (PV) systems. Also, the economics and environmental impacts of FPV plants are presented by introducing the main challenges and prospects. The FPV plants can be conventionally installed on water bodies/dam reservoirs or be implemented as multipurpose systems to produce simultaneous food and power. Installing FPV modules over water reservoirs can prevent evaporation but penetration of solar radiation still remains an issue that can be eliminated by employing bifacial PV modules. The salt deposition in off-shore plants and algae-bloom growth are other important issues that can degrade modules over time and adversely affect the aquatic ecosystem. The capital expenditure (CAPEX) for FPV systems is about 25% higher than ground-mounted plants, mainly due to the existence of floats, moorings, and anchors. It has been stated that the capacity increase of FPV plants (ranges from 52 kW to 2 MW) can intensely decrease the levelized cost of energy (LCOE) up to 85%. It is estimated that FPV technology can become more affordable in the future by further research, developments, and progress in both technology and materials.

Sorption heat storage attracts considerable attention because its relatively high theoretical energy density compared to other heat storage methods offers various opportunities in the design of renewable and sustainable energy systems. However, limited heat transfer in the material bed remains one of the main limitations of a successful introduction to the market. In the present study, a mathematical model of the heat and mass transfer processes inside an adsorption bed of silica gel embedded with cylindrical and rectangular fins has been developed. A systematic analysis has been conducted to augment thermal transport in the adsorption bed with rectangular and pin fin configurations. A parametric study has been conducted for both fin configurations at different bed heights (δb), fin diameters/thicknesses (ϕfin/δfin) and fin spacings (δs). Further, a design-of-experiments study is conducted to relate the energy discharge (Edis) and peak power (Wpeak) to the various governing parameters, as such identifying which parameters maximize energy discharge (Edis) and peak power (Wpeak). The design-of-experiment study reveals that the rectangular fin configuration shows better performance compared to the cylindrical fin configuration.

The electrical conversion efficiency of building integrated photovoltaic (BIPV) decreases with an increase in the operating temperature. To overcome this drawback, it required to maintain the operating temperature at standard test conditions. The working temperature of the BIPV can be kept at a higher efficiency end by the usage of phase change materials (PCM). However, the heat transfer rate of conventional PCM is very poor and can be enhanced by using thermal conductive nanoparticles. The present study has been effectuated to show the effect of various nanoparticles on the operating temperature of the BIPV. A computational fluid dynamics (CFD) analysis taking into cognizance the heat and mass transfers in a system made of a nano-enhanced PCM attached to the back of a BIPV has been conducted. The n-octadecane has been considered as base PCM material which is mixed with four different nanoparticles at three different concentrations. Aluminum oxide (Al2O3), Copper (Cu), Copper oxide (CuO), and Titanium dioxide (TiO2), have been used as the nanoparticle to augment the thermal conductivity of PCM. The result showed that the addition of nanoparticle in an appropriate amount considerably reduced the operating temperature of BIPV for a longer duration of time. The maximum temperature reduction is obtained with Cu nanoparticle and minimum with TiO2. The panel temperature can be maintained below 40°C for about 60 min. with Cu nanoparticles at 5 % concentration. At the same concentration, Cu will take maximum time i.e. 56 min. to melt completely. The three days numerical simulation at the actual weather conditions of Raebareli (26.2345° N, 81.2409° E) has also been conducted with the Cu nanoparticle and it was noticed that the insertion of nanoparticle in the PCM reduced the operating temperature of the PV panel as compared to the pure PCM. The maximum operating temperature difference of 1.65 °C, 1.19 °C, and 1.15 °C was obtained at first, second, and third day at around 12.50 PM.

The present study deals with the development of ternary mixtures of fatty acids for low temperature thermal energy storage applications. The commercial grade fatty acids such as Capric Acid (CA), Lauric Acid (LA), Palmitic Acid (PA) and Stearic Acid (SA), have been used to prepare stable, solid–liquid phase change material (PCM) for the same. In this regard, a series of ternary mixture i.e. CA–LA–SA (CLS) and CA–PA–SA (CPS) have been developed with different weight percentages. Thermal characteristics of these developed ternary mixture i.e. melting temperature and latent heat of fusion have been measured by using Differential Scanning Calorimeter (DSC) technique. The synthesized materials are found to have melting temperature in the range of 14–21 °C (along with adequate amount of latent heat of fusion), which may be quite useful for several low temperature thermal energy storage applications.

The renewable energy resources have high impending to offer the way out to the long-standing energy shortage difficulties being confronted through the emerging countries like India. The solar energy obtained from the sun can be an imperative part of India’s plan not only to add new capability but also to upsurge energy security, address ecological concerns, and lead to the huge market for renewable energy. The electricity generated by solar thermal which is also known as concentrating solar power is emerging renewable energy technologies and can be developed as a future potential option for electricity generation in India. In this chapter, authors have been summarizing the accessibility, present status, promotion policies, strategies, viewpoints, major achievements barriers and future perspective of solar energy opportunities in India.

HVAC systems are comprised of the heating, ventilation, and air-conditioning systems in domestic and commercial buildings. These mechanical systems provide thermal comfort and air quality in indoor spaces. Types of HVAC systems include air conditioners, heat pumps, furnaces, boilers, rooftop units, chillers, and packaged systems. The HVAC system plays an important role in the energy efficiency of buildings. HVAC systems account for 39% of the energy used in commercial buildings in the United States. Consequently, almost any business or government agency can realize significant savings by improving its control of HVAC operations and improving the efficiency of the HVAC system. The uses of high-performance HVAC equipment can result in considerable energy, emissions, and cost savings (10%–40%). Whole building design coupled with an “extended comfort zone” can produce greater savings (40%–70%). Extended comfort includes employing concepts, such as providing warmer, drier air using desiccant dehumidification in summer, or cooler air with warmer windows and walls in winter. In addition, high-performance HVAC can provide increased thermal comfort, and contribute to improved indoor environmental quality (IEQ). This chapter describes different types of air conditioning systems that are the important component of efficient HVAC systems. The chapter also focuses on the technology overview, energy consumption, energy saving strategies, and the role of HVAC system in energy-efficient buildings.

Solar photovoltaic (PV) technologies installed on building rooftops and facades are common in some parts of the world. The majority of these systems are composed of modules that are attached to the surfaces of roofs and facade by means of different types of racking hardware. The photovoltaic panels are integrated into the building fabric replacing conventional building covering materials, but with the added benefit of producing renewable electricity. PV performance considerations mostly influence systems designs with aesthetics often coming secondary. But growing consumer interest in distributed PV technologies and industry competition to reduce installation costs are enhancing the development of multifunctional PV products that are incorporated into building materials. This chapter describes the methods, development, and application of building integrated photovoltaic in various types of buildings. The chapter also focuses on the benefits of the application of building integrated photovoltaic in green buildings, which cover building as well as producing electricity.

International audience

International audience; The present study deals with the investigation of melting behaviour of phase change materials (PCMs) during the cyclic heating. For this work, a computational fluid dynamic (CFD) study of heat and mass transfer during melting and solidification of PCM is carried out for the constant and variable (sinusoidal) heat supply. For the constant heat flux a step function ranging from 500 W/m2 to −500W/m2 and for variable heat flux, a sine function having a similar area as step function was considered at one wall of the container to provide heating and cooling of the PCMs. The results are reported in terms of melting interface, melt fraction during melting and solidification, temperature variation, the variation of melted PCM velocity, and rate of energy storage and release. From the results, it is observed that the melting time is reduced with variable heat flux as compared to constant heat flux and it is also pointed out that the melting time of PCM is lower as compared to solidification time

In recent years the thermal energy storage applications with phase change materials have attracted wide interest. This has motivated a number of R&D efforts to develop novel materials and design new applications based on PCM. The efficient design of the new applications majorly depends on the quality of PCM employed. Numbers of reviews, reports have been written to compile the wide range of PCMs made available for different applications. This paper focuses on the development of next generation PCMs through the enhancement of thermophysical properties namely thermal conductivity, latent heat of fusion and sensible heat. The paper presents a detailed review of the research updates in this direction so as to produce PCMs with enhanced efficiency in terms of thermal energy storage and efficient heat transfer.

The present study deals with the thermal analysis of building bricks containing phase change materials (PCM) when subjected to ambient weather conditions such as solar radiation and ambient temperature. Thermal modelling of building bricks containing PCM has been carried out to utilise the high latent heat of fusion for indoor comfort in buildings. In the thermal model presented in this paper, the PCM is filled in the cylindrical cavity of the bricks. The two-dimensional numerical study has been carried out using finite element analysis method considering heat and mass transfer in the PCM. The effectiveness of PCM in the building bricks has been evaluated by comparing the three different cases - the normal bricks, bricks with air filled in the cylindrical cavity and bricks with PCM filled in the cylindrical cavity. Additionally, the study has also been carried out considering different PCMs, with a varying quantity of single PCM as well as multiple PCM. The obtained results indicate that the Capric acid is more effective PCM in comparison to the Paraffin and RT-25. The maximum heat flux reduction is found to be 8.31% with Capric acid filled in three cylindrical cavities. From the present study, it is also evident that the application of PCM in building brick could be an effective technique for passive thermal control of buildings.

This chapter mainly describes the various numerical methods that can be used for performance evaluation of the solar drying system. The numerical techniques help to develop solar dryers to increase drying effectiveness and analyses, and they forecast the performance of dissimilar types of solar dryers. The numerical analysis is essential for forecasting the relevant parameters, which are highly required in a solar drying system. Computational fluid dynamics (CFD) can be used to analyze and investigate the heat and mass transfer inside the solar dryer. An adaptive-network-based "fuzzy" inference system (ANFIS) is able to predict the performance of the solar drying system. The artificial neural network can be applied to estimate the quantity of the dehydrated product. Fuzzy logic is an essential tool for precisely forecasting the results with the least inaccuracy.

The requirement of fresh water is growing exponentially in industrial as well as domestic sector, resulting in more pollution of natural water resources and creating a scarcity of drinking water. Additionally, the number of arid and desert regions on the world map which already face the shortage of rainfalls and ground water. The problem is substantially increased as most of the water bodies like rivers, lakes are saline and brackish which are not suitable for drinking purpose. In recent past, solar desalination has been found to be a sustainable and economical way of generating the fresh water to cater the need of drinking water at large. Much technological advancement in the field of solar stills has been made which can ably produce a large quantity of fresh water depending on the availability of solar radiation. Various desalination schemes have been utilized to utilise water from such available resources to convert the available water in to the drinkable water. Additionally, attention has also been put on developing efficient solar still with latent heat based thermal energy storage systems which can work in the absence of sunlight as well. In the present paper, a short review on solar stills utilizing latent heat storage has been presented. The present study covers the design specifications, efficiency, along with the comparative analysis of solar stills with latent heat storage system, investigated in the last decade. A discussion on the future research outlook in the area of solar stills with latent heat storage has also been given, so as to make it more economically viable for generating sustainable potable water.

International audience; The thermal conductivity of commonly used phase change materials (PCM) for thermal energy storage (TES), such as, fatty acids, paraffin etc., is relatively poor, which is one of the main drawbacks for limiting their utility. In the recent past, few attempts have been made to enhance the thermal conductivity of PCM by mixing different additives in the appropriate amount. Graphene nanoparticles, having higher thermal conductivity may be a potential candidate for the same, when mixed appropriately with different PCM. In present study authors have carried out the numerical investigation for the melting of graphene nano-particles dispersed PCM filled in an aluminum square cavity heated from one side. In this work, the graphene nanoparticles are mixed in three different volumetric ratios (1%, 3%, and 5%), with three different commonly used categories of organic, inorganic and paraffin PCM (namely, Capric Acid, CaCl2·6H2O, and n-octadecane) to see the effect on melting of composite PCM developed. The resulting transient isotherms, velocity fields, and melting front and melt fractions thus have been deliberated in detail. These results clearly indicate that the addition of graphene nanoparticles increases melting rate but can also hamper the convection heat transfer within large cavities. The study also shows that such enhanced PCM can be effectively used for different TES applications in different fields. The prediction of temperature variation and rate of melting or solidification may be found useful especially for designing such TES devices.

International audience; Solar Photovoltaic (PV) cells can absorb up to 80% of the incident solar radiation obtained from the solar band, however, only a small amount of this absorbed incident energy is transformed into electricity depending on the conversion efficiency of the PV cells and part of remainder energy increases the temperature of PV cell. High solar radiation and ambient temperature lead to an elevated photovoltaic cell operating temperature, which affects its lifespan and power output adversely. Number of techniques have been attempted to maintain the temperature of photovoltaic cells close to their nominal operating value. In the present review various cooling techniques such as natural and forced air cooling, hydraulic cooling, heat pipe cooling, cooling with phase change materials and thermoelectric cooling of PV panels are discussed at length. It is important to note that, though cooling techniques are highly needed to regulate the PV module temperature, especially for mega installations, these should be economically viable too.

International audience; The higher operating temperature of photovoltaic panels (above the standard operating temperature, usually 25 °C) adversely affects the panel’s efficiency. PV panel coupled with phase change materials (PCM) could be a feasible solution due to the higher energy storage density of such materials. However, heat transfer studies of PCM combined with PV panel are quite intricate due to variable ambient conditions and changing thermo-physical property of the material with phase change. In the present study, detailed heat transfer study of the PV panel coupled with PCM has been performed. The computational fluid dynamic study of the PV module coupled with PCM is carried out in which essential heat transfer mechanisms between PV module to PCM and environment have been accounted for. Additionally, its effect on power output has been investigated to see the variation of PV module operating temperature. This study clearly suggests that for realistic simulation of heat and mass transfer studies of PV panel attached with PCM, it is very important to consider following effects into account: convection effect within melted PCM, the velocity of wind, and angle of inclination of PV panel. The results from the study demonstrate the ability and importance of such model to reasonably simulate the thermal characteristics of PV panels coupled with PCM. The maximum panel operating temperature with conduction and convection effect is found to be 54.90 °C and 58.5 °C when convection mode in melted PCM (only conduction mode) is not considered. It has also been shown that the higher wind velocity and tilt angle leads to lower operating temperature of PV panels.

Various heating systems are used to meet the heating requirements of the greenhouses. The conventional solution for this problem is the burning of some fossil fuel inside the greenhouse during cold days. The use of latent heat energy for greenhouse heating in winter days is a significant development. The storage of the excess heat in greenhouses for sunny days in a cold season is advantageous, in view of increasing concerns over usage of fossil fuel. Thermal storage plays a vital role in solar devices particularly in greenhouses to improve its performance because of the intermittent nature of solar energy. Therefore, a storage system constitutes an important component of the solar energy utilisation system. Thermal energy can be stored as sensible heat, latent heat or chemical energy. The present study is carried out to present a review of the solar greenhouse based on latent and sensible heat energy storage. The various designs and application methods are reviewed considering different thermal energy storage materials employed for building a solar greenhouse and future prospects of the same have been discussed.

International audience

International audience; Photovoltaic (PV) panels, depending on the PV cell technology used, convert only a small amount of incident energy into electricity (about 5–25% for commercial systems), and the rest is converted into heat. The produced heat is partly transferred back to the environment while the remaining part causes the enhancement of the PV panel temperature itself. This increase in the PV panel temperature further affects power production adversely, if the PV panel temperature rises above the standard operating temperature (usually 25 °C). The present study deals with the thermal analysis of PV panel involving (i) numerical study based on finite element heat transfer, (ii) the outdoor experimental validation of the thermal model developed. The thermal model is based on the energy balance of the PV module in which all essential heat transfer mechanisms between the module to the environment and related power output are modeled to observe the net change in PV module temperature. The results clearly demonstrate the need and ability of the model to realistically simulate the thermal behavior of PV panels. Additionally, using the same model, numerical simulations have been also carried out for two different cities, namely Allahabad and Jodhpur, for Indian climate, to predict the hourly average module temperature of PV panels for different months. The results show that normal module temperature is raised much above the standard test conditions for the months of April, May and June.

Thermal energy storage (TES) systems using Phase Change Materials (PCM) are very attractive due to high storage density and economic viability. Use of fatty acids as phase change material for various TES applications: buildings, solar heating systems, air-conditioning systems have been widely accepted. It is highly desired to study the performance of PCMs for a particular application, in terms of heat transfer mechanism and geometry/structure of the container, as it helps in optimizing the cost and quality of TES systems. In the present work, authors studied the performance of five different fatty acids (Capric acid, Lauric acid, Myristic acid, Palmitic acid and Stearic acid) when used with aluminum containers. The numerical simulation of heating and cooling of PCMs has been conducted using finite element analysis (FEM). The results are reported in term of melt fraction, temperature variation, the transition of solid-liquid interface and the quantity of thermal energy stored in different fatty acids with time for melting and solidification. Based on the simulated results it can be concluded that the Capric takes minimum time for melting and solidification with the same boundary conditions, among the studied PCMs in this work. Such studies could be quite helpful in developing fatty acid based TES applications.

Solar dryer based on thermal energy storage materials is quite effective for continuously drying agriculture and food products at steady state in the temperature range (40 °C–60 °C). Such dryers have globally become a potential viable substitute to the solar dryers based on fossil fuel, due to the utilization of clean energy resources and cost-effectiveness. Storage materials utilized in these dryers can store energy during the sunshine hour and deliver the stored energy during off-sunshine. It reduces the existing load on the gap between energy demand and supply, hence plays a vital role in energy sustainability. A number of studies have been done in last few decades for drying agriculture and food products with a solar dryer based on thermal energy storage concept. This paper mainly presents a review on the important contributions made so far in the field of solar drying systems based on the thermal energy storage medium, with a focus on recent updates in thermal energy storage technology available in terms of materials capable of storing heat as sensible and latent heat.

International audience

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International audience

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