Despite its highest efficiency, concentrated photovoltaic (CPV) technology is still finding its way into the current photovoltaic market which is saturated with conventional flat-plate photovoltaic systems. CPV systems have a great performance potential as they utilize third-generation multi-junction solar cells. In the CPV system, the main aspect is its concentrating assembly design which affects not only its overall performance but also its operation and fabrication. Conventional CPV design targets to use individual solar concentrator for each solar cell. The main motivation of this chapter is to propose a novel concentrating assembly design for CPV that is able to handle multiple solar cells, without affecting their size, using single solar concentrator. Such proposed design, named as multicell concentrating assembly (MCA), will not only reduce the assembly efforts during CPV module fabrication, but it will also lower the overall system cost with simplified design. In this chapter, a detailed design methodology of multicell concentrating assembly (MCA) for CPV module is presented and developed with complete verification through ray tracing simulation and field experimentation.
Part of the book: Solar Panels and Photovoltaic Materials
To compete with the fossil fuel, there is a need for steady power supply from renewable energy systems. Solar energy, being highest potential energy source, is only available during diurnal period. Therefore, for steady power supply, an energy storage system is needed to be coupled with the primary solar energy system. For such application, hydrogen production is proved to provide long term and sustainable energy storage. However, firstly, there is a need to capture solar energy with higher efficiency for minimum energy storage and reduced system size. Concentrated photovoltaic (CPV) system, utilizing multi-junction solar cell (MJC), provides highest energy conversion efficiency among all photovoltaic systems. Despite, there is no model reported in the literature regarding its performance simulation and stand-alone operation optimization. None of the commercial software is capable of handling CPV performance simulation. In this chapter, a detailed performance model and an optimization strategy are proposed for stand-alone operation of CPV with hydrogen production as energy storage. A multi-objective optimization technique is developed using micro-GA for its techno-economic analysis. The performance model of MJC is developed based upon the cell characteristics of InGaP/InGaAs/Ge triple-junction solar cell. The system design is presented for uninterrupted power supply with minimum system cost.
Part of the book: Advances In Hydrogen Generation Technologies
Owing to diverse photovoltaic technology and dynamic nature of meteorological data, a number of factors affect the performance of photovoltaic systems. The highly efficient concentrated photovoltaic (CPV) system can only respond to beam radiations of solar energy, unlike stationary silicon-based conventional photovoltaic (PV) panels. The availability of solar energy, and share of beam/diffuse radiations, varies from region to region, depending upon weather conditions. However, the rated performance as instantaneous maximum efficiency at STC (standard testing conditions) or NOCT (nominal operating cell temperature) in the laboratory, does not depict the true system performance under changing field conditions. The energy planners are interested in actual field performance, in terms of total delivered energy. Therefore, despite highest efficiency, CPV installations seem to be limited to desert regions, with high beam radiations availability and favorable working conditions. In this chapter, the performance potential and feasibility of CPV system is reported for long term operation in tropical weather conditions, in terms of proposed electrical rating parameter, giving total energy delivered as kWh/m2.year. From 1-year field operation of two in-house built CPV units, electrical rating of 240.2 kWh/m2.year is recorded for CPV operation in Singapore, the first ever reported CPV performance in this region, which is two folds higher than the stationary PV.
Part of the book: Energy Conversion
The high performance evaporators are important for process industries such as food, desalination and refineries. The falling film evaporators have many advantages over flooded and vertical tubes that make them best candidate for processes industries application. The heat transfer area is the key parameter in designing of an evaporator and many correlations are available to estimate the size of tube bundle. Unfortunately, most of the correlation is available only for pure water and above 322 K saturation temperatures. Out of these conditions, the areas are designed by the extrapolation of existing correlations. We demonstrated that the actual heat transfer values are 2–3-fold higher at lower temperature and hence simple extrapolated estimation leads to inefficient and high capital cost design. We proposed an accurate heat transfer correlation for falling film evaporators that can capture both, low temperature evaporation and salt concentration effectively. It is also embedded with unique bubble-assisted evaporation parameter that can be only observed at low temperature and it enhances the heat transfer. The proposed correlation is applicable from 280 to 305 K saturation temperatures and feed water concentration ranges from 35,000 to 95,000 ppm. The uncertainty of measured data is less than 5% and RMS of regressed data is 3.5%. In this chapter, first part summarized the all available correlations and their limitations. In second part, falling film evaporation heat transfer coefficient (FFHTC) is proposed and model is developed. In the last part, experimentation is conducted and FFHTC developed and compared with conventional correlations.
Part of the book: Heat and Mass Transfer
Due to the emerging water crisis, the global desalination capacity has been expanding exponentially in the past few decades, leading to substantial amount of primary energy consumption. Therefore, the exploration of energy-efficient desalination processes and alternative energy sources has been the subject of great research interests. The spray-assisted low-temperature desalination (SLTD) system is a novel method for desalination that enables efficient renewable energy utilization. It works on the direct-contact spray evaporation/condensation mechanism and uses only hollow chambers. The merits include enhanced heat and mass transfer, lower initial and operational costs, and reduced scaling and fouling issues. This chapter presents a study on the SLTD system driven by sensible heat sources. The working principle of the system will be introduced first. Then a thermodynamic analysis will be presented to obtain the freshwater productivity under different design and operational conditions. Additionally, the energy utilization level will be quantified to highlight the energy wastage when operating with sensible heat sources. Afterward, the system configuration will be modified to maximize the utilization of sensible heat sources and promote productivity. Finally economic viability of the modified design will be evaluated.
Part of the book: Desalination
A direct-contact heat and mass exchanger (DCHME) has many advantages over a traditional surface-type heat exchanger, including a high heat transfer coefficient, simplicity of design, and low OPEX and CAPEX. DCHME has a capability to exchange of both heat and mass between the two fluids in the same process. Hence, DCHMEs are widely used in numerous applications in various industries, including the air conditioning industry for cooling and dehumidification and heating and humidification. Based on their structure, DCHME can be categorized into two groups; two fluids direct contact (TFDC) exchanger and two direct contacts with one non-contact fluid (TDCONF) exchanger. This study developed a mathematical model for these two types of exchangers by using a discretized volume with distributed lumped-parameters method instead of using the conventional log mean enthalpy difference (LMHD) and NTU-effectiveness method. Thus, this model can reflect both heat and mass transfer behavior in every spatially distributed physical system. The objective of this study is to develop a mathematical model to be used as a tool for designing DCHME and to be applied as a sub-function of the model predictive control system to predict the effectiveness and dependent parameters of DCHME under the different load conditions and its various input parameters.
Part of the book: Heat Exchangers
A major fraction of secondary energy consumed for our daily activities, such as electricity and low-grade heat sources, emanates from the conversion of fossil fuels in power plants. In the seawater desalination processes, the energy efficiency is usually expressed in kWh electricity or kWh of low-grade heat per unit volume of water produced. Although kWh energy unit provides a quantitative measure of input energy, it has subtly omitted the embedded quality of supplied energy to desalination plants. In assuming the equivalency across dissimilar energy forms, it results in a thermodynamic misconception that has eluded the desalination industry hitherto, i.e., not all units of derived energy are created equal. An incomplete energy efficacy approach may result in the inferior selection of desalination processes to be deployed;—a phenomenon observed in the trend of installed desalination capacity globally. Operating a less efficient desalination plant over its lifespan would create much economic burdens including a higher unit cost of water, higher CO2 emissions and greater brine discharge to the environment. This book chapter clarifies the key concept and a thermodynamic framework to rectify the misconception in energy consumption, permitting energy planners and designers to optimize deployment of future desalination plants for energy sustainability. We have derived conversion factors to convert assorted derived energies into standard primary energy for fair comparison.
Part of the book: Alternative Energies and Efficiency Evaluation