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Über dieses Buch

This book focuses on solar-energy-based renewable energy systems and discusses the generation of electric power using solar photovoltaics, as well as some new techniques, such as solar towers, for both residential and commercial needs. Such systems have played an important role in the move towards low-emission and sustainable energy sources. The book covers a variety of applications, such as solar water heaters, solar air heaters, solar drying, nanoparticle-based direct absorption solar systems, solar volumetric receivers, solar-based cooling systems, solar-based food processing and cooking, efficient buildings using solar energy, and energy storage for solar thermal systems. Given its breadth of coverage, the book offers a valuable resource for researchers, students, and professionals alike.





Introduction to Applications of Solar Energy

We know that on the global scale till now the major sources of energy are fossil fuels like coal, oil, and natural gases. Because of following three reasons, it is pertinent to use the naturally available renewable energy in the form of solar energy to replace fossil fuel energy: (a) With the advent of science and technology and with ever increasing global population, the total energy consumption is increasing day by day, (b) the fossil fuel reserves world over are fast depleting, and (c) the fossil fuels emit greenhouse gas during combustion, contributing significantly to global warming. Not surprising, during the last two, three decades, hectic research has been going on in almost all developed/developing countries to develop techniques to make maximum use of solar energy through various processes like thermal processes, photovoltaic processes. In India many research groups are actively engaged in studying utilization of solar energy in an efficient way using variety of techniques. The present monograph titled “Applications of Solar Energy” is the result of collection of work done by some such research groups.
Himanshu Tyagi, Avinash Kumar Agarwal, Prodyut Ranjan Chakraborty, Satvasheel Powar

Distributed Polygeneration Using Solar Energy: A Future Sustainable Energy System for India

Energy is the key element of modern development. Fossil fuels are presently the major source of energy consumed worldwide. However, this is not sustainable. Fast depletion of limited resources and climate change problem due to emission from these fuels are of major concern. Increasing overall efficiency of energy conversion and use is one option. Moreover, exploring new systems with better utilization of renewable resources may be a possible future sustainable option. Decentralized polygeneration to meet energy and other utility demand with rational use of local resources is emerging as a suitable option. To match the varying demand with intermittent renewable resources, storage could be a good solution. However, suitable low-cost and reliable storage is not yet fully developed. Hybridization of different intermittent renewable resources is a possible option. Countries with enough solar insolation like India may develop suitable hybrid polygeneration with solar inputs. Depending on local need, both solar thermal and photovoltaic utilities may be included in this polygeneration. Efficient system integration with possible optimization of different available local resources based on local needs is the key to successful polygeneration design. In this chapter, a comprehensive review of state-of-the-art solar-based polygeneration will be presented. Multi-objective optimization of hybridization of different available resources to meet local needs will be included in this chapter.
Avishek Ray, Sudipta De

Heat Transfer Aspects of Solar Thermal Collectors


Effect of Reflector Absorptivity on Radiative Heat Exchange in Case of Solar Receiver Collection Systems

In case of solar central receiver systems, the major portion of incident solar radiation is reflected by the concentrating reflectors or heliostats towards the receiver by specular reflection and minimum portion is received through diffused radiation. In order to know this diffused component of radiation energy transfer, the absorptivity of reflectors as well as shape factors between the reflectors and the central receiver is must. The present chapter is dealing with the estimation of radiative heat/energy exchange between the hot cavity receiver and reflecting collector surface along with the diffused configuration factor computation encompassing in solar reflector-collector systems of various orientations and geometries. The configuration factors have been evaluated using contour integral technique, which has been reported as one of the accurate and faster tools for configuration factor estimation. The integral cum analytical expressions are also demonstrated for configuration factor, and the methodology adopted for exchange of radiative heat between the hot cavity receiver and the reflecting surface of parabolic dish collector is also discussed.
Santosh B. Bopche

Numerical Investigation of the Temperature Distribution of a Solar Cavity Receiver Wall Using Finite Element Method

The finite element method has been proved to be the effective numerical tool for finding approximate solutions of two or even up to three-dimensional governing differential equations. It has an ability to handle irregular geometries and any number of complicated boundary conditions with ease. The cavity receiver of a solar thermal system operates at a very high temperature. It may also cause larger energy losses from the cavity by radiation as well as convection as dominant modes of heat transfer. The collection efficiency depends on the useful heat gained by the working fluids, which is influenced by the receiver-energy losses. The energy losses from the cavity receiver depend on the cavity wall surface temperature. The temperature variation depends on the boundary conditions as well as geometrical orientation of the receiver. The knowledge of temperature distribution is one of the important factors needed for evolving an ideal design of a cavity receiver. The present chapter focuses on the design aspects as well as approximate estimation of wall temperature distribution of a cavity receiver of cylindrical shape. The step by step formulation of the problem using finite element method is also presented in the present chapter. The computational domain of a receiver wall is discretised into number of triangular elements and the simultaneous equations are solved using MATLAB.
Suneet Kumar, Santosh B. Bopche

Volumetric Solar Thermal Collectors


Direct Absorption Solar Thermal Technologies

Solar collectors that can directly absorb radiation represent an emerging realm of solar thermal systems wherein the collection as well its subsequent conversion to the useful thermal energy happens within the working fluid. Nanofluids (stable dispersions of nanoparticles in the basefluid) have been found to be promising working fluids for realizing such direct solar to thermal energy conversion owing to their enhanced (and the ease of tuning) thermo-physical and optical properties. Seeding trace amounts of carefully chosen nanoparticles into the basefluid has been shown to significantly enhance the solar weighted absorptivity of the basefluid—hence rendering them is suitable for solar thermal applications. Firstly, a brief description relevant to the incumbent surface absorption-based solar thermal technologies has been presented. A critical analysis of the fundamental limits of performance that can be achieved in the incumbent solar thermal systems reveals that solar selectivity could only be beneficial up to a certain temperature and solar concentration ratios, beyond which we cannot further improve the efficiency. Subsequently, the candidature of direct absorption solar thermal systems has been assessed to ascertain if these could be deployed under conditions which are not so amenable for the conventional surface absorption-based solar thermal technologies. Finally, a representative experimental study is presented that points out that even for low solar concentration ratios (conditions which are more suitable for the conventional surface-based absorbers), the two classes of solar thermal technologies can have comparable thermal efficiencies. It is envisaged that the benefits of the direct absorption-based solar thermal systems over the conventional ones shall be more pronounced for high-flux conditions, i.e. high solar concentration ratios.
Vikrant Khullar, Harjit Singh, Himanshu Tyagi

Solar Thermal Energy: Use of Volumetric Absorption in Domestic Applications

Solar thermal systems are one of the renewable energy systems used in the residential buildings for the heating purpose, and with these systems, the usage of non-renewable energy resources decreases. To improve the performance of solar collectors, engineers and scientists are regularly working on it. Direct absorption-based solar thermal collectors (DASTC) are kind of solar collectors in which the fluid can be heated directly (without any absorption surface). The present study deals with numerical model of direct absorption-based solar collector which can be used for residential purposes. The absorbed energy fraction, effect of the height, length of collector, and mass flow rate on the collector efficiency have been determined. The analysis shows that collector efficiency increases with the increase of mass flow rate when the height of the fluid in the collector is same and the efficiency of the collector deceases with the increase of channel length. Further, it has been observed that it is beneficial to use an optimum volume fraction of the nanoparticles in DASTC because at an optimum volume fraction, the collector achieved maximum efficiency.
Vishal Bhalla, Vikrant Khullar, Harjit Singh, Himanshu Tyagi

Thermal and Materials Perspective on the Design of Open Volumetric Air Receiver for Process Heat Applications

The concentrated solar thermal technologies (CST) are versatile in view of their multi-faceted applications, such as, process heat, cooling, and electricity generation. These are of line and point-focusing types with the later having much higher flux concentration (in Suns). This allows achieving a temperature in excess of 1200 K using, for instance, the open volumetric air receiver (OVAR). Such a high temperature is useful for applications, like the one which is developed at IIT Jodhpur, namely the solar convective furnace for heat treatment of aluminum. This requires a temperature of up to 750 K in the first phase of development. Thus, a suitable solar selective coating withstanding such a high temperature and having a thermal conductivity close to the base material for operating in an open atmosphere is desirable. Because of its atmospheric exposure, air and dust-induced degradation is inevitable, which may lead to its failure. These challenges are to be addressed for adapting such high-temperature CST technologies in arid deserts of India, the Middle-East, and Africa. In view of such challenges, the following details and foreseen developments are discussed in the paper:
design of OVAR including various sub-components;
flow-stability and the effect of heat-flux distribution on an absorber pore;
the developed coating and its characterization for OVAR.
Gurveer Singh, Rajesh Kumar, Ambesh Dixit, Laltu Chandra

Thermal Storage of Solar Energy


Solar Thermal Energy Storage

Over the past few decades, considerable research efforts have been devoted to improve the usage of renewable energy resources. Till date, major energy demands have been addressed by fossil fuels, and the limited resource of these precious fuels is continuously depleting at an alarming rate. Increase in the energy demands, deficiency of fossil fuels, and influence of pollution on the environment have forced us to opt for renewable energy resources. Solar energy is a natural source of energy that is not depleted by its use. It is a promising option for replacing conventional energy resources partially or totally, but it is transient, intermittent, and unpredictable in nature. Because of this sporadic nature of solar energy across a given interval of hours, days, and season, various practical problems arise. Variable DNI causes power plants to shut down for few hours of the day or to run at part load most of the time. This creates a demand for an effective subsystem which is capable of storing energy when available solar energy overshoots the demand during the interval of radiant sunshine, and to make it accessible during night or season. A similar problem arises for waste heat recovery systems where accessibility of waste heat and usage period are not the same, and thus creates a need for thermal energy storage (TES) for energy conservation. TES has tempted a lot of researchers to improve its high energy storage capacity and efficiency. If solar energy system is not run with TES, a considerable section of energy demand has to depend on conventional resources which in result reduce the annual solar fraction. TES helps to reduce dependency over conventional resource by minimizing energy waste. TES is mainly described by the parameters like capacity, power, efficiency, storage period, charge and discharge time, and cost. There are different storage mechanisms by which energy can be stored: sensible, latent, and chemical reactions. In sensible-type storage, energy is stored by increasing the temperature of solid or liquid storage media (e.g., sand-rock minerals, concrete, oils, and liquid sodium). These materials have excellent thermal conductivity and are cheaper, but due to low heat capacity, it increases system size. In latent-type storage, energy is stored/released during phase change; thus, it has higher storage capacity than sensible, but suffers from the issue of low thermal conductivity. As the solid–liquid phase change process of pure or eutectic substances is isothermal in nature, it is beneficial for the application having limitations with working temperature. In chemical-type TES, heat is absorbed/released due to breakdown or formation of chemical bonds. The technology is not much developed and has limited application due to possibility of degradation over time and chemical instability. TES can also be classified as active and passive depending upon the solid or liquid energy storage medium. Active TES is further classified as direct active and indirect active depending on whether the storage fluid and the heat transfer fluid (HTF) are same or some other HTF is required to extract heat from solar field. The discussion in this chapter includes basic heat transfer models, along with experimental studies by different research groups on various TES. Finally, methods and design criteria that can improve the system performance are discussed.
Aniket D. Monde, Amit Shrivastava, Prodyut R. Chakraborty

Review on Integration of Solar Air Heaters with Thermal Energy Storage

Solar radiation on the earth’s surface is abundant and truly a zero-carbon energy source. The solar energy needs to be harnessed using various efficient equipments, which has a very low carbon footprint. Various solar thermal energy harvesting techniques have been used which employ solar radiation incident on the optimal area with the help of concentrators.
Prashant Saini, Dhiraj V. Patil, Satvasheel Powar

Solar Thermal Energy Storage Using Graphene Nanoplatelets-Added Phase Change Materials

Thermal energy storage (TES) is a key system to reduce the gap between energy supply and energy demands. Energy storage materials play a very important role in the design of TES. Energy storage materials store energy in form of sensible heat, latent heat and thermochemical energy storage. Compared to the various forms of energy storage, latent heat-based energy storage system can store a lot of energy at isothermal temperature during melting and can release the stored heat during solidification. Phase change material (PCM) includes organic, inorganic and eutectic materials. One of the primary disadvantages of PCMs is their very low thermal conductivity. This challenge could be overcome by the addition of high thermal conductive additives to form a composite. Thermo-physical property determination of these composites is very important to determine the feasibility of using such composites as energy storage materials. Characterisation techniques like differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR), thermo-gravimetric analysis (TGA) and laser flash apparatus (LFA) are very effective and useful methods to determine the potential use of PCM in TES applications. This work offers the characteristics of pentaerythritol (PE) and D-Mannitol (DM) and the effect of adding high conductive graphene nanoplatelets (GnPs) to form a phase change composites. Thermal cycling is done to evaluate the thermal reliability of the composite after repeated melt/freeze cycles. Finally, the composite will be evaluated for its suitability of being used as a PCM in LHES systems.
S. Suresh, Srikanth Salyan

Various Applications of Solar Energy: Cooling, Cooking, Efficient Buildings


Water–Lithium Bromide Absorption Chillers for Solar Cooling

Solar thermal resources can be effectively utilized to meet the refrigeration and air-conditioning demands for both household and industrial purposes. Considerable fraction of total available electricity is consumed by the conventional vapor compression refrigeration systems (VCRS) during the summer season in countries with tropical climate. The leakage of VCRS refrigerants in the atmosphere has also been identified as one of the major contributors toward ozone layer depletion and hence global warming. The utilization of solar thermal energy for obtaining refrigeration and air-conditioning is the key to address these issues concerning high electricity demand as well as the environmental pollution. Solar thermal energy, being one of the leading resources of green energy, can reduce the carbon footprint considerably, when used for sorption cooling process. The advantages of using sorption cooling systems powered by solar thermal energy over VCRS are twofold when we consider environmental issues. Sorption-based solar thermal cooling reduces the electricity demand for cooling to a large extent, which in turn reduces usage of fossil fuels to produce this electricity, and thus leads to low-carbon footprint. Also, the refrigerants used for sorption cooling are less prone to cause ozone layer depletion. Although sorption-based refrigeration systems driven by solar thermal energy are mature technologies, wide acceptability of such cooling system is yet to be achieved. Two major limitations of sorption-based solar thermal cooling are relatively low coefficient of performance (COP), and large volume requirement. Other than these two limitations, the intermittent nature of solar thermal resource and heat exchanger and control mechanism design complicacies also pose considerable challenge. Sorption cooling technology can be broadly classified base on absorption and adsorption processes. Absorption is a volumetric phenomenon where a substance of one state gets absorbed in another substance in a different state with or without having chemical reaction, such as liquid being absorbed by solid or gas being absorbed by liquid. On the other hand, adsorption is a surface phenomenon due to physical bonding forces such as Van der walls forces between a solid surface and adjacent fluid or due to chemical bonding between the two. The discussion in this chapter is attributed to Water–Lithium Bromide-based absorption cooling systems. The discussion emphasizes on fundamental concepts of absorption refrigeration cycle, starting with simplest intermittent vapor absorption refrigeration system and gradually elaborating toward the operating principles of commercially used chillers at the end. Cycle analysis of most commonly used single-effect absorption chillers is discussed in a detailed manner along with the background knowledge of how to determine pertinent thermodynamic properties at the inlet and outlet of individual components. Finally, methods and design criteria that can improve the system performance are discussed.
Ashok Verma, Satish, Prodyut R. Chakraborty

Solar Assisted Solid Desiccant—Vapor Compression Hybrid Air-Conditioning System

Solar assisted solid desiccant—vapor compression based hybrid space cooling system for building thermal comfort is made by integrating desiccant based dehumidification system as well as by use of solar heating system along with conventional VCR system. This is because in humid climates, excessive humidity during summer leading to inefficiencies of conventional cooling devices. Humidity increment in ambient air as well as ventilation requirement suddenly rises the latent load of the space to be cooled. Conventional VCR systems are not effective in handling both temperature and relative humidity of cooling air independently. The application of solid desiccant based hybrid cooling systems significantly ameliorates the humidity control irrespective of temperature of supply air. The application of renewable free energy like as use of solar energy for regenerating the desiccant used in desiccant wheel helps us to alleviate the major requirement of electric energy needed by conventional VCR air-conditioning system for hot sunny days. So, it ameliorates overall energy efficiency and reduces energy costs. Performance of solid desiccant—vapor compression based hybrid building space comfort cooling system has been evaluated during hot and humid period from April to September for the ambient conditions of the Roorkee for various important parameters such as temperatures of supply air, room air and regeneration air etc. Regeneration temperature is one of the most important parameters having the key role in changing the performance of desiccant based cooling system.
D. B. Jani, Manish Mishra, P. K. Sahoo

Solar Food Processing and Cooking Methodologies

In this study, a theoretical analysis of food processing (e.g., solar drying), worldwide cooking pattern, and cooking methods by using the solar energy has been reviewed. Solar food processing method is applied as direct absorption, air heater, and a combination of direct and indirect drying by solar radiation. Therefore, this process is one of the most accessible and hence the most widespread processing technologies. Traditional solar drying involves keeping products in the direct sunlight. Solar drying and cooking processes take place at different temperatures and timescales, and it depends on the nature of the food or substance. The amount of solar energy that reaches to the system and design parameters determines the performance of food processing and cooking systems. The time duration of drying and cooking depends on the temperature of heated air and environment. The temperature distributions, mass, and ingredient of food have an important role in the performance of dryers and cooker boxes. For a better understanding of the system parameters, the concept of solar food processing has been discussed thermodynamically. Energy saving by using solar systems has also been discussed.
Abhishek Saxena, Varun Goel, Mehmet Karakilcik

Visual Comfort Based Algorithmic Control for Roller Shade and Assessment of Potential Energy Savings

Offices which are mostly operated during day-lit hours are fascinated toward incorporation of solar daylighting systems so as to get benefitted of energy savings along with intangible benefits like good health, well-being, and productivity of their occupants. But discomfort glare is usually ignored in front of rigorous energy load optimization practices and researches, or even if considered, is not properly quantified, which leads to a false evaluation of the performance of daylighting in the context of lighting energy savings. Blinds when operated with optimum visual comfort prevention measures, then only can create a functional day-lit environment. The present study includes modeling and analysis of an east facing office building located in New Delhi, India. It utilizes drafting tool Rhinoceros 3D 5.0 and simulation tool DIVA 4.0 to mathematically analyze the utilization of natural lighting for the office. The analysis includes properly arranged viewpoints similar to that experienced by any occupant, being placed in simulation environment so as to visualize and evaluate realistic glare scenario. The study further deals with the observation and analysis of the illuminance patterns inside the test space and glare values for different blind positions modeled. An algorithm has been developed to analyze the required visual comfort level of the space and suggests an appropriate blind position for every occupancy hour that eventually leads to estimate the potential energy savings through the utilization of daylight. It was observed that even after providing visual comfort to the occupants, the reduction in savings was marginal, measured to be 1% as compared to the case when visual discomfort is overlooked in daylighting utilization.
Lakshya Sharma, Dibakar Rakshit

Power Generation Using Solar Energy


Solar Updraft Tower—A Potential for Future Renewable Power Generation: A Computational Analysis

The full-scale three-dimensional analysis of solar updraft tower power plant in Manzanares, Spain has been performed using commercially available CFD tool ANSYS Fluent. The two-equation k-\(\varepsilon \) turbulent model with standard wall function has been utilized for the fluid flow. The soil has been modeled with the consideration of the fact that temperature at 20 m depth remains constant throughout the year. The surface-to-surface radiation model is also included in the heat transfer model. The simulation has been performed for the steady state without/with radiation, the transient state with/without thermal storage on 8th of June. In the present simulation, water has been taken as thermal storage. It has been found that results improve considerably by including radiation effect, closely match with the results published from the plant. There is a reduction in the maximum velocity with the thermal storage; however, sufficient energy is available in thermal storage to overcome intermittency of insolation. The strong dependency of the plant on insolation can be reduced with the thermal storage.
Ankit Agarwal, Pradeep Kumar, Balkrishna Mehta

Manufacturing Techniques of Perovskite Solar Cells

Perovskite solar cells (PSCs) are in focus of the solar cell development research for the last few years due to their high efficiency, cost-effective fabrication, and band gap tunability. Perovskite solar cell efficiency sharply increased from its initial reported efficiency of 3.8% in 2009 to 22.1% in 2016. This makes PSCs as the technology with the fastest growth rate in terms of the efficiency. Different device architectures have also been developed in an attempt to improve the PSC efficiency. At laboratory scale, a spin-coating process is employed to deposit different layers of PSCs. Though spin-coating process helps to achieve high efficiency, for large-scale production viability, researchers are developing different deposition techniques. A broad range of manufacturing techniques for perovskite-based solar cells have been tested and reported comprising drop casting, spray coating, ultrasonic spray coating, slot die coating, electrodeposition, CVD, thermal vapor deposition, vacuum deposition, screen printing, ink-jet printing, etc., with different device architectures. This chapter summarizes different PSC structures along with the corresponding manufacturing techniques.
Priyanka Kajal, Kunal Ghosh, Satvasheel Powar
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