Adsorption (AD) cycle is recently pioneered for cooling and desalination applications. For water treatment, the cycle can be used to treat highly concentrated feed water, ranging from seawater, ground water, and chemically laden waste water. This chapter presents a review of the recent development of AD cycle and its hybridization with known conventional cycles such as the MED and MSF. We begin by looking at the basic sorption theory for different adsorbent–adsorbate pairs, namely the silica gel–water and the zeolite–water pairs. Under the IUPAC categorization, there are six types of isotherm behavior that capture almost all types of adsorbent–adsorbate behaviors and many isotherm correlations have been developed to described their uptake patterns, namely the Henry, Langmuir, Toth, etc. We have recently developed a correlation that can universally capture all six types of isotherms of IUPAC and it requires only four regression coefficients.
Part of the book: Desalination Updates
In falling film evaporators, the overall heat transfer coefficient is controlled by film thickness, velocity, liquid properties and the temperature differential across the film layer. This chapter presents the heat transfer behaviour for evaporative film boiling on horizontal tubes, but working at low pressures of 0.93–3.60 kPa as well as seawater salinity of 15,000–90,000 mg/l or ppm. Owing to a dearth of literature on film-boiling at these conditions, the chapter is motivated by the importance of evaporative film-boiling in the process industries. It is observed that in addition to the above-mentioned parameters, evaporative heat transfer of seawater is affected by the emergence of micro-bubbles within the thin film layer, particularly when the liquid saturation temperatures drop below 25°C (3.1 kPa). Such micro-bubbles are generated near to the tube wall surfaces, and they enhanced the heat transfer by two or more folds when compared with the predictions of conventional evaporative film-boiling. The appearance of micro-bubbles is attributed to the rapid increase in the specific volume of vapour, i.e. dv/dT, at low saturation temperature conditions. A new correlation is thus proposed in this chapter and it shows good agreement to the measured data with an experimental uncertainty less than ±8%.
The expansion trend of current desalination processes is expected to boost brine rejection to 240 km3 and CO2 emission to 400 million tons per year by 2050. This high brine rejection and CO2 emission rates are copping COP21 goal, maintaining temperature rise below 2°C. An innovative and energy-efficient process/material is required to achieve Paris Agreement targets. Highly efficient adsorbent cycle integration is proposed with well-proven conventional desalination processes to improve energy efficiency and to reduce environmental and marine pollution. The adsorbent cycle is operated with solar or low-grade industrial waste heat, available in abundance in water stress regions. The proposed integration with membrane processes will save 99% energy and over 150% chemical rejection to sea. In case of thermally driven cycles, the proposed hybridization will improve energy efficiency to 39% and will reduce over 80% chemical rejection. This can be one solution to achieve Paris Agreement (COP21) targets for climate control that can be implemented in near future.
Part of the book: Desalination and Water Treatment
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 inevitable escalation in economic development has serious implications on energy and environment nexus. The International Energy Outlook 2016 (IEO2016) predicted that the Non Organization for Economic Cooperation and Development (non-OECD) countries will lead with 71% rise in energy demand in contrast with only 18% in developed countries from 2012 to 2040. In Gulf Cooperation Council countries (GCC) countries, about 50% of primary energy is consumed for cogeneration based power and desalination plants. The desalination capacities are expected to increase fivefold by 2050 and renewable energy application can be one of the solution for sustainable water production. The major bottleneck in commercialization of renewable energy sources is its intermittent nature of supplies specially wind and solar. We proposed solar thermal energy storage to operate desalination system around the clock. Magnesium oxide (MgO) can be utilized as an efficient energy storage system to store solar thermal energy for off period operation. The heat generated by regeneration processes at day time and exothermic adsorption at night can operate desalination cycle 24 h. The operational temperature ranges from 120 to 140°C and energy storage 41–81 kJ/mol. It was successfully demonstrated by experimentation that MgO operated hybrid desalination cycle can achieve highest performance and lowest carbon emission. The proposed cycle can achieve sustainable water production goals.
Part of the book: Water and Wastewater Treatment
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