New Research Directions in Solar Energy Technologies

The overall theme of this book is related to the topics of solar energy. This book has been divided into four parts. The first part relates to the general issues of clean and sustainable energy. The second part of this book deals with the topic of power generation using solar energy.

Solar power is clean, green, renewable and reliable energy source. The chapter revisits initiatives and commitments of Indian state toward clean and secure energy and brings into discussion how this commitment is shaped in the context of global awareness and local economic and energy compulsions. The chapter discusses how recognition of global warming and climate change paved way for international cooperation leading to conventions and targeted mitigation of anthropogenic environmental hazards, which also shapes India’s efforts for switching toward renewable and clean energy sources. India began its journey toward renewable energy in the early 1980s, which galvanized with the foundation of new Ministry to look for alternative sources of energy. In 2008, as a part of global commitment and efforts to harness available renewable energy for its economic growth, India devised National Action Plan for Climate Change (NAPCC) in which Jawaharlal Nehru National Solar Mission (JNNSM) is one of the essential mission plans. The chapter looks at policy guidelines of JNNSM and discusses why such mission programs are important for India. In doing so, we discuss targets, goals, achievements of JNNSM and critically look at methods, available technologies for harnessing solar energy and challenges of solar waste disposal. The available technologies for harnessing solar potential restricts realization of production, distribution, consumption of solar energy leading to unsolved energy insecurity. The paper also analyzes methods of decentralized production and distribution and assesses the challenges of employing small-scale solar power plant. India is marching toward achieving several milestones; therefore, the availability of “energy for all” is cardinal not only for inclusive development but also for bringing energy justice to marginalized communities, particularly in rural India.

This chapter presents a comprehensive review of the impacts of cyber attacks on the smart distribution grid and discusses the potential methods in the literature to mitigate them. The review considers different real-world case studies of successful cyber attacks on multiple grid assets, including networks with high-penetration of distributed energy resources (DERs). A specific use-case of a false data injection (FDI) attack on a photovoltaic (PV) production meter data used for 15-minute ahead forecasting is presented. The false data from the production meter causes the command and control center to give incorrect operational settings to the grid. The various impacts of this incorrect operational settings on the dynamics on the grid is theoretically analyzed, followed by simulation studies of this scenario on an IEEE 34 bus system with three PVs, one synchronous generator, and one energy storage. The impact of FDI on the system is analyzed by measuring the nodal voltages, the current flowing through the lines, and the systems’ active and reactive power losses. The results show that the FDI could potentially cause cascading failures due to possible over current and voltage collapse. This monograph also proposes an adaptive protection system based on a neural network model. This allows the network protection scheme to learn (based on the historical data) the dynamics of the system over time and adequately adapt the protection settings of the relays autonomously despite an FDI attack on the PV production meter. This study will be of particular importance to the utility and DER installers to proactively mitigate FDI attacks, thereby improving the overall situation awareness.

The emergence of the new class of organic–inorganic hybrid perovskite materials has found numerous applications in a plethora of next-generation optoelectronic devices like solar cells, light-emitting diodes, photodetectors, and lasers. Synthetic controls of perovskite materials through composition engineering, solvent chemistry, morphology and surface controlling, surface passivation, and band engineering have made the perovskite solar cells the fasted growing technology in the history of solar cells evolution. The perovskite semiconductors possess a number of unique functionalities like easily tunable band-gap energy, solution processability, form long-range crystals at low temperatures (<150 °C), excellent charge transport properties, and self-resistance toward electronic impurity. However, ionic nature and relaxed structural arrangement of the perovskite crystals makes them vulnerable to degradation by moisture and temperature. The stability of perovskite-based solar cells is one of the major roadblocks for their commercialization, though the power conversion efficiency (25.1%) is comparable to monocrystalline silicon solar cells. In this chapter, we will discuss the recent progress in synthesis strategy, structural stability, optical and electronic properties, and evolution in device engineering of the highly efficient perovskite solar cells. We will also elaborate on the future directions to improve stability of the perovskite solar cells.

Dye-sensitized solar cells (DSSC) developed from natural plant-based dyes gained prominence due to low manufacturing costs and environmental friendliness. There is a strong demand for wearable solar cells utilizing natural plant-based dyes. Currently, a significant focus is on improving the efficiency of a DSSC. Every component and step in the fabrication of a DSSC is crucial in ensuring that a stable and efficient DSSC is developed. Different coating methods were reviewed in the fabrication of both counter and working electrodes in textile-based DSSCs (TDSSC). Various types of plant dyes were used to achieve an excellent conversion efficiency in a TDSSC. A suitable coating method will also allow for proper adhesion of the TiO₂ paste, thereby improving the electron transport in the TDSSC. Various methods used in the analysis of the dye to test for the optical properties and photo-electrochemical properties of DSSCs will be studied and analyzed. In a conventional DSSC, both the working and counterelectrodes are made of fluorine-doped glass, while in a TDSSC, either the working or counterelectrodes are made from textile fabric. A DSSC that is all-textile, with an efficiency rating similar or better than that of a glass DSSC, has yet to be developed. The challenges in the fabrication of TDSSC will be reviewed. The purpose of this chapter is to review and compare various conductive coating methods reported in a TDSSC; additionally, various plant-based dyes used for that purpose will also be reviewed.

Rapid urbanization along with intensive solar radiation increases the surface temperature of buildings. The heated surfaces further lead to growth in the ambient temperature and subsequently lead to urban heat island. This leads to a higher demand for electricity, mostly in the summer, which in turn has an adverse effect on global warming. It is potentially feasible to utilize the thermal energy from the sunlight to alleviate these problems. The thermoelectric phenomenon is a viable option to convert available thermal energy to electricity for power generation in buildings. Cement, common building material, and their composites are attractive for making low-priced thermoelectric materials to convert trapped thermal energy in the building surfaces into electricity. However, the realization of this potential is limited yet due to the low thermoelectric conversion efficiency of cement composites. Improving conversion efficiency via composite engineering and incorporating thermoelectric cement at the building surfaces may generate electricity, which can be possibly achieved for powering small-scale devices. This chapter reveals a way to improve the thermoelectric properties of cement composites with the addition of graphene nanoplatelets. The different weight percentages of graphene are blended with cement and then compressed to fabricate bulk composites. On bulk samples, the thermoelectric properties are measured.

Solar energy is the most efficient and economic gateway for power generation. The development of solar research and technological innovation, and corresponding decline in the prices of solar power harnessing devices, has paved the way for low-cost energy generation in developing country, India. It is estimated that if at least 10% of the total geographical area are effectively utilized, the available solar energy would be 8 million MW, which is equivalent to ~6000 Mtoe per year (https://​www.​indiaenergyporta​l.​org/​subthemes.​php?​text=​solar). However, installed photovoltaic systems including the solar panels in desert areas and in the industrial areas are prone to the accretion of dust and dirt particles. This resultant fouling hinders the conversion of incident light into electricity, causing a decline in the energy conversion efficiency up to 50%. To maintain a steady performance of PV panels, the surfaces of which must be cleaned regularly. However, current methods of cleaning are expensive, inefficient, and potentially harmful to the surfaces. With recent progress in nanotechnology research, nanostructured coatings have become multifunctional, efficient, and smart. Particularly, self-cleaning coatings have gained considerable attraction owing to its application in a wide range of fields. In this chapter, a brief review regarding the recent progress of bio-mimic self-cleaning coatings on photovoltaic solar systems is presented. A brief introduction on the types of self-cleaning coatings and their properties, such as wettability, optical transparency, mechanical durability, and environmental durability characteristics, is discussed. A short note on the considerations and developments regarding the fabrication of durable, self-cleaning coatings for photovoltaic systems has been presented.

Food habits and cooking methods are changing in recent decades. The recipes and cooking methods for most of the popular fast foods require ingredients to be cooked in an electric oven. The sale of the oven toaster griller type oven is surging in India. Revenue generated from the sale of cookers and ovens in India is the second highest globally. These numbers indicate the expected surge in electrical consumption because of ovens in India. The available solar cooking appliances come with their own set of merits and demerits. In this chapter, a conceptual electrical and solar hybrid cooking appliance has been introduced with a similar user interface and features available in a commercially available electric oven. The conceptualized oven also has a provision of outdoor cooking using solar thermal energy. The described control mechanism and design not only shows the simplicity of the appliance, but also points out how it can replace both electric ovens and solar cooking appliances. In hybrid mode, the smart switching mechanism minimizes the electrical energy requirements by utilizing the solar energy at the maximum available extend. This hybrid mode also saves a lot of cooking time compared to solar mode. The experimental results suggest energy saving of approximately 51% and much lesser cooking time as compared to electric ovens and solar cooking appliances, respectively, when operating in hybrid mode.

Vacuum insulation panels (VIPs) are well known for their low thermal conductivity and are considered to be an effective solution for conserving energy in buildings. The performance of VIP considerably depends upon the geographical conditions, geometrical parameters, and climatic conditions. The ambient conditions such as temperature and relative humidity are the major parameters which degrade the performance of VIPs. The excessive permeation of gas through the barrier envelope disturbs the vacuum maintained inside the VIP, resulting in degradation of the core and reduction in service life. The sol–air temperature plays a key role in analyzing the performance of the VIP. In the present analysis of VIP, Van der Waals equation is used in place of the prevailing ideal gas equation for more precise results. While using Van der Waals equation for the analysis, results do deviate from the previously performed calculations using ideal gas equations. The VIP is then incorporated in the concrete wall and numerical computation of the concrete wall–VIP combination is carried out for Jodhpur city of Rajasthan in India which belongs to hot and dry geographical condition. The optimum location of the VIP is determined to achieve the minimum heat gain through the wall. The heat transfer across the concrete wall–VIP combination signifies the importance of ambient conditions and VIP analysis with the real gas equation.

A developing nation like India is quickly adopting the technologies related to electric vehicles (EVs) and slowly eliminating the fossil fuel-based vehicles as a part of their plan to battle climate change and increasing pollution in cities. In April 2017, the Government of India (GoI) planned to have all EVs by 2030 in the market. The promotion under faster adoption and manufacturing of electric vehicles (FAME) scheme is also followed. The electric charging infrastructure is an essential component of the electric mobility ecosystem. It is essential for EV charging station markets to match the pace of the EV adoption and its growth. EVs are limited by their range and speed. The availability of charging stations and its network on the road is the key to encouraging a shift from fossil fuel vehicles to EVs. Therefore, an everlasting difficulty faced by most EV manufacturers and customers is the accessibility of a plug point for charging. Definitely, there is a requirement to shift from the grid-based charging stations to stand-alone off-grid solutions for charging. The key to resolve this problem is the use of abundant renewable energy sources such as solar energy. This chapter presents a detailed review of EV charging systems and solar-based EV charging systems, infrastructure, methodology, and their implementation in India. Various challenges and social barriers to the adoption of EVs are also discussed.

A large amount of energy is being used worldwide to maintain the ambient temperature conditions inside buildings. Most of this energy is generated from the combustion of fossil fuels. Also, air conditioning units used in buildings emit harmful greenhouse gases. For these reasons, we must find some alternate passive designs that can be implemented for the conservation of energy within the premises. As phase change materials (PCM) have large energy storage capacity due to its high values of latent heats, PCMs can be efficiently used to reduce the surge in energy demands. Incorporating PCM within building components enhances their thermal heat capacity as well as improves the energy efficiency of the buildings. Numerous researchers are experimenting with PCMs for their use in energy-efficient buildings. In this study, numerical modeling has been carried out for a PCM incorporated model that can be used depending on different climatic zones in India. The dimensions and boundary conditions used in numerical modeling are kept near the realistic weather conditions in various climate zones. The PCM selection has been carried out by taking into consideration the desirable thermophysical properties, operating temperature, availability, and weather conditions in different locations. From the results, it can be concluded that this model is beneficial in reducing the cooling loads of buildings in extremely hot places as well as for decrementing the heating loads in cold weather zones.

Parabolic dish concentrator-based solar cooker is a highly promising alternative green technology capable of providing clean energy solution for wide varieties of domestic and commercial culinary requirements. Since a significantly high temperature range of 250–350 °C can be easily obtained adjacent to the focal region of the parabolic concentrator, the technology is suitable for a wide variety of cooking involving grilling, frying, simmering, and boiling. The utilization of solar energy for domestic or commercial cooking also reduces dependence on fossil fuels, resulting in lower carbon footprints. However, a major limitation of the existing forms of such solar cookers is associated with the duration and availability of solar irradiation, which renders the system active only during the on-sun period. The inaccessibility of solar radiation for cooking before sunrise and after sunset can only be addressed by incorporating effective thermal energy storage (TES) systems in conjunction with parabolic dish reflectors. The development of a compact storage cooking unit involving latent heat thermal energy storage (LHTES) might play a crucial role to overcome this severe limitation. Phase change material (PCM) with suitable melting point and large latent heat of fusion can be considered as an ideal thermal energy storage medium for household or commercial cooking applications. The usage of PCM as the thermal energy storage medium also enables the storage system to deliver heat at a narrow band of temperature during the cooking. Thermal energy is stored during the melting of PCM, and the process is defined as charging of LHTES system. The stored heat can be extracted during the cooking involving heat flow from the molten PCM to the cooking unit rendering gradual solidification of the storage medium. Although phase change materials (PCM) seem to be an ideal thermal storage medium, one of the major concerns associated with them is their low thermal conductivity (0.25–0.5 W/mK). Potential phase change materials with melting temperature close to 300 °C are mostly inorganic salts in pure or multicompositional forms, having low thermal conductivity. As a result, charging duration involving complete melting process of the PCM might end up getting extended beyond a feasible time span of solar irradiation. Low thermal conductivity of storage medium also causes undesirable steep thermal gradient within the storage unit. Therefore, thermal conductivity enhancement of the PCM is of utmost importance. Usage of PCM-CEG (CEG: compressed expanded graphite) composite to enhance the thermal conductivity of the latent heat storage medium is explored and found to be a promising solution. The present chapter is aimed at providing a detailed feasibility study of solar cookers containing LHTES integrated with parabolic concentrator. Numerical studies are performed to analyze the heat transfer phenomena in PCM-CEG composite embedded inside the thermal storage container with and without circumferentially oriented radial fins. Enthalpy updating scheme addressing the inclusion of CEG matrix embedded within PCM has been adapted for the numerical prediction of melt fraction within the LHTES.

Solar energy is a promising renewable source to support the growing energy demand. Sensible heat thermal energy storage (SHTES) is widely used, in practice, to supply the stored energy, in off-solar hours. These systems can be built using locally available and environment friendly materials. However, a good design as well as proper choice of materials is essential to construct an efficient and economical system. In this work, the secondary SHTES system of in-house solar air tower simulator (SATS) is investigated. The system uses hot air as heat transfer fluid and magnesium silicate pebbles as the storage material. The function of the secondary TES here is to store the waste energy from the hot air after it exits the solar convective furnace (SCF). The charging and discharging of the TES system are studied experimentally. It is observed that the secondary TES performance is satisfactory and serves as a proof of concept for future development.

Use of solar energy has seen significant growth in recent years. One of the key areas of direct use of solar energy is domestic water heating. A properly designed solar water heater can provide most of the hot water required for residential applications in a cost-effective and environmental-friendly manner. A major requirement of solar water heaters is the control of the water delivery temperature from the solar heater. Consistent water temperature should be maintained at the outlet of the system as required for specific applications. Also, heating of water is dependent on the availability of solar energy which naturally varies during the daytime and can be affected significantly by local weather conditions. One of the ways to overcome this difficulty is to use an intermediate phase change material (PCM)-based energy storage system which stores part of the solar energy during peak supply and releases it during lean periods. This chapter presents a study on the use of PCM-based energy storage systems for solar water heating. At first, a brief description of solar water heating process is given. This is followed by a discussion on the use of energy storage systems for solar water heating. Subsequently, a CFD model is presented to simulate the charging and discharging of a PCM-based energy storage system. The model is based on the enthalpy method and can capture the evolution of melting and solidification of PCM due to the flow of heat transfer fluid in the energy storage unit. The effect of important parameters such as flow inlet temperature and velocity, storage unit dimensions, and charging time on melting and temperature evolution is analyzed in detail.

At present, India imports around 86% of total petroleum products to cater its energy demand. However, in a single hour, the amount of power from the sun that strikes the Earth is more than the entire world consumes in a year. Despite of this, globe uses only 0.023% of the solar energy through photosynthesis that reaches the earth (https://​www.​world-builders.​org/​lessons/​less/​biomes/​SunEnergy.​html). Therefore, there is an urgent need to focus on research related to the energy storage and energy saving (through waste heat recovery) to curb the usage of natural resources. This paper presents the comprehensive review of latent heat thermal energy storage (LHTES) using phase change materials (PCMs) for solar and waste heat recovery (WHR) applications in the temperature range of 40–200 °C. The main reason to choose this temperature range is because general conventional heating and cooling applications in the domestic, commercial, and public administration sectors lie in this temperature range. The review focuses on study of different PCMs suitable for solar air and water heating, solar stills, solar absorption cooling, waste heat recovery, and solar thermal electricity generation. Energy storage for longer duration and curtailing thermal losses is quite challenging. Therefore, there is a lucrative scope of research on efficient thermal energy storage. Keeping this in cognizance, this study also lays emphasis on thermal conductivity enhancement techniques of PCMs, selection of suitable heat exchangers to store maximum thermal energy of PCM for longer duration, and effect of various heat exchange design parameters on thermal performance of PCM.