Solar Thermal Systems: Thermal Analysis and its Application

This chapter covers the basics of thermodynamics and heat transfer, which helps in understanding the heat transfer mechanism and thermal modeling of various solar thermal systems covered in further chapters. The laws of thermodynamics and heat transfer are also covered in the chapter. The general terms related to thermodynamics and heat transfer are also defined in this chapter, as these terms will be used frequently in upcoming chapters.

This chapter discusses the causes and effects of solar energy incidents on Earth's spectral, skyward angular, intensity, and luminous characteristics. A particular perspective is how these characteristics influence and determine how particular practical devices, systems, and applications harness available solar energy. The uses of solar energy to produce heat, generate electricity via photovoltaics, and provide daylight are considered. Moreover, diverse factors limiting the applicability of specific solar energy conversion devices or approaches are also discussed.

The thermal applications of solar energy have gained momentum after the revolution in the field of PV technology in recent decades. The worldwide quest to harness the thermal component of solar energy, which constitutes the major part of the incident, solar radiation incident globally, has led to the development of numerous thermal devices and applications that harness and store or utilize the same with never before seen efficiency. A few applications and devices are discussed here in this chapter. The first part of the chapter presents a brief discussion of the solar pond and its features along with thermal modeling of the system, followed by the thermal modeling and discussions about solar cooling systems. The later part of the chapter describes solar refrigerators and solar concentrators. The application and devices discussed here are of prime importance in developing basic and advanced solar thermal devices to harness solar thermal energy efficiently for human needs.

The design, analysis and modeling of solar energy-based water purifiers, commonly known as a solar still, which is based on the greenhouse effect, is the requirement of time as there is a scarcity of freshwater throughout the globe. The technology of purifying dirty water using solar energy is a promising solution for simplifying contemporary water scarcity as this technology does not create any bad effect on the surroundings, unlike conventional water purification technology, which creates a lot of polluting elements and ultimately has become problematic for the environment. Most solar energy-based water purifiers are self-sustainable, and they can be installed in remote locations where sunlight and source of impure water are available in abundance. This solar energy-based technology of water purification should perform better in hilly locations as the intensity of light is higher than the intensity of light in fields. The current chapter deals with the thermal modeling of different types of passive and active solar stills, including solar stills loaded with water-based nanofluids, followed by their energy and exergy analyses.

One-third of the Earth is covered by seawater, yet there is a constant lack of water in many places. A total of 97% of the water is present in the sea as salt water, and only 3% of water is potable, out of which only 1% of clean water reaches the people. Therefore, a device is needed that can convert salt water into clean water. Solar still is a sustainable device through which dirty and salt water can be converted into clear water. Due to the low productivity of conventional solar still; it is not popular in the market. Increasing the productivity of conventional solar still is a major challenge for researchers. Researchers are continuously working on the performance of solar still to increase its productivity. The modifications and designs made by researchers in solar still over the last ten years are encapsulated in this chapter. Solar still with PCM, nanoparticles, reflectors, collectors, external condenser, wick materials, and different angles are studied, and applications of distilled water have also been covered in this chapter.

With the rising population and continuous depletion of our natural resources, it has become very tough for everyone to meet their basic needs of food and water. Also, at the rate with which the water-stressed area continues to rise, we soon will be facing a huge water crisis. This chapter specifically talks about India and its potential to make a switch from conventional methods of water usage and switch to a renewable energy-based water desalination unit. This chapter presents an elaborate analysis of the Indian peninsular region and talks about the major cities’ comparative performance in the basic design of the solar humidificationdehumidification desalination unit. It can be concluded that the southern-most area has a very large potential for setting up an economically feasible desalination unit. Various parameters are discussed, like humidity ratio, outgoing airstream temperature, and mass rate of evaporated water. As Chennai has the best performance for the particular unit for most of the year, with productivity reaching 44 kg/day, the least favorable site seems to be Puri in Odisha, where productivity remains less and constant at a maximum of 34 kg/day during summers.

Solar energy technologies are upgrading day by day in every sunshine-rich region around the globe. These technologies provide a strong platform for humans for high-demand activities like cooking, air heating, power generation, etc. Among these activities, solar cooking is much popular due to daily cooking needs. Different designs of solar cookers are available in the market according to the family size. In the present work, the designs of some commonly used solar cookers and their thermal performance evaluation have been discussed. Heat transfer analysis shows that cookers with some potential heat storage materials are better than conventional solar cookers. The design of such cookers is feasible to cook efficiently for long hours, even during off sunshine hours (for a limited period).

The consumption of conventional energy has increased exponentially due to the ever-increasing population of the world. Studies revealed that cooking activities contribute majorly to the overall energy consumption throughout the globe, further accounting for an increasing global warming potential. Being an enormous, virtually unlimited, and expandable source, solar energy turns out to be a favorable solution to the situation. Solar energy's widespread availability and processing technologies make the thermal energy conversion process easily accessible. Hence, solar energy has emerged as a ‘natural solution’ to the energy crisis and the adverse environmental impact, such as the greenhouse effect. This chapter outlines the various solar cooker fundamentals and development in different types of solar cookers, namely box type, panel, funnel type, parabolic type, and indirect type, along with the application of different solar cookers.

In this review, an attempt has been made for various applications of semitransparent photovoltaic thermal (SPVT) modules used for PVT-CPC water air collector, drying, space heating/cooling of the building, greenhouse integration for agricultural production of vegetables, and power generation. It has been observed that semi-transparent photovoltaic thermal (SPVT) modules are more efficient and economical for many sectors and have more advantages than opaque photovoltaic thermal modules. The brief details of each case have been discussed. Furthermore, a greenhouse integrated semi-transparent photovoltaic thermal (GiSPVT) system has been elaborated for vegetable growth with different packing factors.

With the advancement in technology and manufacturing techniques, various solar cell materials evolved, and their practical implementation led to modification in the design and installation of photovoltaic panels. Different solar cells are compared in this chapter considering their efficiency, performance, temperature coefficient, etc. Developments in PV panel and photovoltaic thermal (PVT) systems are outlined with their respective applications and advantages. It was found that the cost and efficiency of any solar cell are crucial parameters for deciding its implementation in PV panels. Additionally, the solar panel's temperature deflates its efficiency and lowers the thermal conversion. In order to overcome this problem, a PV system was incorporated with different thermal storage materials and cooling mediums, such as air, water, oil, fluids, etc., lowering the temperature of solar panels and making them able to store the excess solar thermal energy to use it during the sunoff period. It was concluded that thin solar cells, such as perovskite and DSSC solar cells, are widely used where flexibility is important and thermal storage materials are utilized with nanoparticles for better thermal efficiency.

In agricultural applications, the preservation of crops is essential. The most suitable method of preserving the crop is drying. The traditional methods used for drying include mechanical drying, where hydrocarbon fuel or burnable materials are used as a source of heat. The other method is open sun drying, where crops are placed in an open space. Both methods affect the quality and vital nutritious properties of the crops. The mechanical drying processes are costly, whereas the latter is dependent on the weather condition. To overcome these limitations, solar dryers are developed. Mathematical modeling is highly important for the perfect design and improvement of solar dryers. The performance of the drying system depends upon the different parameters that can be optimized using thermal modeling. This chapter covers the thermal modeling of greenhouse solar dryers for active and passive modes.

Solar drying is one of the oldest and most popular food preservation methods that involve moisture removal by a complex heat and mass transfer phenomenon. The process of the drying system is dependent on a number of operating parameters. In the present chapter determination of thermal and drying performance parameters is discussed. A hybrid solar drying system with the integration of an evacuated water tube solar water heater is installed and tested for drying hygroscopic leaf crops. The drying performance of the hybrid system is evaluated in terms of mass reduction and its derived influence on moisture content and drying rate. The derived parameters are compared with the corresponding evaluations under open sun drying. The rise in greenhouse environment temperature and crop surface temperature at hourly intervals as compared to the ambient condition were used as parameters for the thermal performance of dryer. The average values of SMER were 60% lesser than that of the simple PVT-hybrid system (without ETSC), but the drying performance parameters of mass reduction, drying rate and mass shrinkage ratio provide favourable results. The drying time was reduced by 3.5 and 2.5 hours, respectively, for the present sample size of two crops as compared to the open sun drying.

This chapter provides the description and analysis of a photovoltaic thermal (PVT) air heater, including a thermoelectric module (TEM). A PVT air heater offers several advantages over a PVT water heater. The problems such as corrosion and freezing do not exist when air is used as a working fluid. Also, the system design is less complex, incurs lower operation costs and can be easily integrated into buildings. Furthermore, it is not a cause of any major concern in case of air leaks from the duct. A PVT air heater poses some drawbacks as well, such as uneven cooling of PV panels and lower overall efficiency compared to a PVT water heater resulting from lower specific heat capacity of air. Nevertheless, the choice of the type of working fluid is subject to a variety of factors like efficiency, cost including capital investment, installation, operation and maintenance costs and the particular application.

Many harmful effects on the environment can be observed over the past decades due to the extensive usage of non-renewable energy. Most discussed and harmful are the ever-changing global climate change scenarios and their aftermath. As a point of fact, a major part of the world’s energy consumption is dependent on non-renewable energy sources, such as petroleum, oil, coal, and gas. Unquestionably, these fossil fuels contribute a great deal to greenhouse gas emissions, carbon dioxide, methane, etc., which further leads to global health issues, global warming, and climate change. With the emergence of sustainable development as a holistic concept since the late 1980s, the issue of global warming has been given prominent attention. It is evident that failure to curb global warming has led to slower progress in achieving sustainable development. About 30% of energy demand is from the built environment sector, which is also responsible for contributing 28% of carbon emissions and continues to add an estimated 1% every year, according to reports by UN Environment [1]. Therefore, the fossil fuel-based energy systems are antagonistic with the goals of sustainable development agendas. Hence, using renewable sources in harnessing clean energy for the built environment has not remained a choice but a fundamental need. Solar energy is one of the cleanest renewable energy sources that provide solutions to climate change and global warming. Often termed as the alternative energy source against oil and coal-based energy sources, solar energy has the potential for abundant availability and is an economical way with a lower ecological and environmental footprint, leading to a better quality of life. Thus, there is a massive amount of global interest in harnessing solar energy for its application and development in building systems.

It is to be noted that biogas production is drastically reduced in cold climatic conditions, especially in winter, due to a drop in ambient air temperature, which is much below an optimum temperature of about 37℃ for fermentation of slurry. Many methods, such as hot charging, passive/active for slurry heating, have been tested, and it has been found that the passive heating method is neither practical nor self-sustained. In order to make bio-gas heating self-sustained, economical, and friendly to ecology and the environment, a new approach of Bi-iSPVT has been adopted. Based on the finding, we have made an attempt to analyze the system in terms of CO2 mitigation, energy matrices, and environ- and exergo-economics to have a clean environment and sustainable climate. An analysis has been performed by using embodied energy, the annual overall thermal exergy of the system for ecological balance for the good health of human beings. It has been found that an energy payback time (EPBT) for a sustainable Bi-iSPVT system is about 1.67years, along with an exergo-economic parameter (Rex) of 0.1016 kWh/