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Presents information on a study which developed a thermodynamic model for predicting the performance of reciprocating chillers. Types of irreversibilities; Check of the functional form of the performance equation; Comparison of predicted and measured performance.

The conventional desalination processes are not only energy intensive but also environment un-friendly. They are operating far from thermodynamic limit, 10–12%, making them un-sustainable for future water supplies. An innovative desalination processes are required to meet future sustainable desalination goal and COP21 goal. In this paper, we proposed a multi-effect desalination system operated with ocean thermocline energy, thermal energy harnessed from seawater temperature gradient. It can exploit low temperature differential between surface hot water temperature and deep-sea cold-water temperature to produce fresh water. Detailed theoretical model was developed and simulation was conducted in FORTRAN using international mathematical and statistical library (IMSL). We presented four different cases with deep-sea cold water temperature varies from 5 to 13 °C and MED stages varies from 3 to 6. It shows that the proposed cycle can achieve highest level of universal performance ratio, UPR = 158, achieving about 18.8% of the ideal limit. With the major energy input emanated from the renewable solar, the proposed cycle is truly a “green desalination” method of low global warming potential (GWP), best suited for tropical coastal shores having bathymetry depths up to 300 m or more. [ABSTRACT FROM AUTHOR]

This paper presents the evaluation of a solid desiccant dehumidifier equipped with adsorbent powder coated heat exchangers (PCHX). The main component of the solid desiccant dehumidifier includes two heat exchangers that are coated with silica gel RD type powders in order to increase water adsorption uptake by improving its heat and mass transfer. A series of experiment are conducted to evaluate two key performance indices, namely, moisture removal capacity (MRC) and thermal coefficient performance (COP th ), under various hot and humid air conditions. Conventional granular adsorbent packed heat exchangers (GPHX) are employed to benchmark the performance of the adsorbent coated heat exchanger (PCHX). Results reveal that the PCHX exhibits higher uptake performance due to better heat and mass transfer. It is found that the moisture removal capacity increases from 7.4 g/kg to 11.0 g/kg with air flow rates of 35 kg/h, resulting in the extended contact time of the water vapor. Experiments also demonstrate that the moisture removal capacity is highly affected by inlet air humidity ratio. In addition, marked improvement in COP th can be achieved by a lowered hot water regeneration temperature. [ABSTRACT FROM AUTHOR]

In an effort to accurately plan for investment on energy production and distribution, this paper proposes a long-term electricity consumption forecasting model for buildings’ cooling by employing a high energy conservative scenario. The key aspect of the high energy conservative scenario is to adopt an innovative adsorbent-based dehumidifier and an indirect evaporative cooling (AD-IEC) technology as opposed to conventional mechanical vapor compression system. Bottom-up equations were developed to identify the cooling load and electricity consumption of both residential and non-residential buildings for the period 2002–2013. Based on the time-series electricity consumption, a multiple linear regression model is developed to forecast electricity demand for the future period of 2014–2030. It is found that the electricity demands for cooling in the building sectors account for 31 ± 2% of the total electricity consumption in Singapore, This study concluded that the high conservative scenario realizes the best potential of electricity saving of 21,096 GWh until 2030. Using a CO 2 emission factor of 4.49 × 10 −4 metric tons CO 2 /kWh, the total carbon footprint saving from all power plants is estimated to be 9491,264 t of CO 2 . This work evolves a new forecasting methodology to predict buildings’ cooling energy consumption involving the use of novel cooling technologies. [ABSTRACT FROM AUTHOR]

Abstract: Desalination, other than the natural water cycle, is hailed as the panacea to alleviate the problems of fresh water shortage in many water stressed countries. However, the main drawback of conventional desalination methods is that they are energy intensive. In many instances, they consumed electricity, chemicals for pre- and post-treatment of water. For each kWh of energy consumed, there is an unavoidable emission of Carbon Dioxide (CO2) at the power stations as well as the discharge of chemically-laden brine into the environment. Thus, there is a motivation to find new direction or methods of desalination that consumed less chemicals, thermal energy and electricity. This paper describes an emerging and yet low cost method of desalination that employs only low-temperature waste heat, which is available in abundance from either the renewable energy sources or exhaust of industrial processes. With only one heat input, the Adsorption Desalination (AD) cycle produces two useful effects, i.e., high grade potable water and cooling. In this article, a brief literature review, the theoretical framework for adsorption thermodynamics, a lumped-parameter model and the experimental tests for a wide range of operational conditions on the basic and the hybrid AD cycles are discussed. Predictions from the model are validated with measured performances from two pilot plants, i.e., a basic AD and the advanced AD cycles. The energetic efficiency of AD cycles has been compared against the conventional desalination methods. Owing to the unique features of AD cycle, i.e., the simultaneous production of dual useful effects, it is proposed that the life cycle cost (LCC) of AD is evaluated against the LCC of combined machines that are needed to deliver the same quantities of useful effects using a unified unit of $/MWh. In closing, an ideal desalination system with zero emission of CO2 is presented where geo-thermal heat is employed for powering a temperature-cascaded cogeneration plant. [Copyright &y& Elsevier]

Abstract: This article presents the performance analysis of a waste heat-driven adsorption cycle. With the implementation of adsorption–desorption phenomena, the cycle simultaneously produces cooling energy and high-grade potable water. A mathematical model is developed using isotherm characteristics of the adsorbent/adsorbate pair (silica gel and water), energy and mass balances for the each component of the cycle. The cycle is analyzed using key performance parameters namely (i) specific cooling power (SCP), (ii) specific daily water production (SDWP), (iii) the coefficient of performance (COP) and (iv) the overall conversion ratio (OCR). The numerical results of the adsorption cycle are validated using experimental data. The parametric analysis using different hot and chilled water temperatures are reported. At 85 °C hot water inlet temperature, the cycle generates 3.6 m3 of potable water and 23 Rton of cooling at the produced chilled water temperature of 10 °C. [Copyright &y& Elsevier]

This research paper presents a study of boiling heat transfer from longitudinal rectangular and square pin finned surfaces immersed in saturated water at low vapor pressures of 2 and 9 kPa. Conventional boiling analysis, which is based on the nominal surface area of the heater, was compared with a boiling analysis that considers the total "wetted" surface area. [ABSTRACT FROM AUTHOR]

Abstract: There has been increasing interest in clean energy over past few years. Ocean Thermal Energy Conversion (OTEC) power plants have been examined as a viable option for supplying clean energy. This paper evaluated the thermodynamic performance of the OTEC power system. Computer simulation programs were developed under the same conditions but with various working fluids for a closed system, a regeneration system, an open system, a Kalina system, and a hybrid system. The results showed that the regeneration system using R125 showed a 0.17 to 1.56% increase in system efficiency. Moreover, the system can generate electricity when the difference in temperature between the warm and cold seawater inlet temperatures is greater than 15°C. In addition, the system efficiency of OTEC power plants using the condenser effluent from a nuclear power plant instead of surface water was increased by approximately 2%. [Copyright &y& Elsevier]

This paper investigates the performance of a solar-assisted adsorption (AD) cycle which produces two useful effects, namely cooling and desalination, with only a low-temperature heat input such as thermal energy from solar collectors. Heat sources varying from 65 to 80°C can be obtained from 215-m2 flat plate-type solar collectors to regenerate the proposed silica gel–water-based AD cycle. In this paper, both mathematical modelling and experimental results from the AD cycle operation are discussed, in terms of two key parameters, namely specific daily water production (SDWP) and specific cooling capacity (SCC). The experimental results show that the AD cycle is capable of producing chilled water at 7 to 10°C with varying SCC range of 25–35 Rton/tonne of silica gel. Simultaneously, the AD cycle produces a SDWP of 3–5 m3 per tonne of silica gel per day, rendering it as a dual-effect machine that has an overall conversion or performance ratio of 0.8–1.1. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the performances of an adsorption desalination (AD) system in two-bed and four-bed operational modes. The tested results are calculated in terms of key performance parameters namely, (i) specific daily water production (SDWP), (ii) cycle time, and (iii) performance ratio (PR) for various heat source temperatures, mass flow rates, cycle times along with a fixed heat sink temperature. The optimum input parameters such as driving heat source and cycle time of the AD cycle are also evaluated. It is found from the present experimental data that the maximum potable water production per tonne of adsorbent (silica gel) per day is about 10m3 whilst the corresponding performance ratio is 0.61, and a longer cycle time is required to achieve maximum water production at lower heat source temperatures. This paper also provides a useful guideline for the operational strategy of the AD cycle. [Copyright &y& Elsevier]

Abstract: The efficacy of a four-bed adsorption chiller has been studied experimentally with respect to a simple but yet effective passive heat and mass recovery schemes. It substantially improves the adsorption chiller COP by as much as 30% over a broad range of cycle time with a wide heat source, coolant and chilled water temperatures. Two schemes have been considered here: Firstly, only the mass recovery is achieved by pressure equalization between the concomitantly cooled adsorber and heated desorber, exploiting the intrinsic vapor-uptake potential by pressure swing that remains in the adsorbent at the end of a half-cycle. Secondly, when both the heat and mass recovery schemes are employed at a rating point of maximum cooling capacity, the chiller COP could increase further to as much as 48%. These improvements are performed without additional hardware changes to the adsorption chiller. [Copyright &y& Elsevier]

Abstract: A general thermodynamic formulation for the operation of a pulsed thermoelectric cooler is presented using the Gibbs law and simple energy balance method. An expression for the entropy flux (W/m2 K) is expressed in terms of the key parameters employed for the thermoelectric operation. Following the classical temperature–entropy (T–s) methodology, which has all the virtues of energy flow identification, the processes along the p–n legs of thermoelectrics, contributing to both useful and dissipative losses, are clearly mapped for the transient operation. [Copyright &y& Elsevier]

Provides information on a study which examined how efficiently can solar radiation realistically be converted into cooling power. Types of large commercial solar-driven cooling systems; Description of the thermodynamic flow diagrams for cooling systems; Brief review of solar fiber-optic mini-dish systems.

Nuclear desalination is one of the ideal options to achieve net-zero emissions. However, most nuclear desalination plants extract steam from the power cycle to drive desalination, leading to a reduction of electricity output. To avoid the parasitic effects of desalination on the power cycle, this study considers recovering waste heat from the power plants' condensers to drive low-temperature desalination systems, including spray-assisted low-temperature desalination system (SLTD), multi-effect distillation system (MED) and spray-assisted multi-effect distillation system (SMED). Thermodynamic and economic models of the three desalination systems are firstly established and validated with experimental data. Then, the impacts of key design, operation and economic parameters are evaluated using the validated models. Results reveal that the productivity and thermodynamic efficiency are promoted by increasing the cooling water flowrate of desalination condenser, enlarging the heat exchanger area and lifting the heat source temperature, while the number of effects has an optimal value of 3. Under the optimal configuration, the gained-output ratio and Second Law efficiency of a 20 m3/day SLTD plant are 0.71 and 1.25 % respectively. In terms of economic performance, the levelized-cost of desalinated water (LCOW) for three plants can be reduced substantially under a larger plant capacity and longer lifespan. When the plant capacity exceeds 20,000 m3/day, the LCOW of SLTD can be reduced to 0.757 $/m3, which is lower than all other desalination systems coupled with power plants or renewable energy sources. [Display omitted] • Low-temperature desalination system driven by waste heat from the condenser nuclear power plants are proposed. • Thermo-economic analyses are conducted to evaluate energetic and economic performances of proposed systems. • Spray-assisted low-temperature desalination demonstrates lowest cost as compared to other technologies. • The levelized cost of desalination can be lowered to $0.757/m3 by expanding plant capacity. [ABSTRACT FROM AUTHOR]

Editorial. Discusses the developments in heat-driven silica gel-water adsorption chillers. Categories of the advent of adsorption chillers; Effectiveness of sorption potential driven by a low-temperature heat source; Characteristic plot of coefficient of performance versus cooling or heating capacity.

Dehumidification is one of the key challenges facing the air conditioning (AC) industry in the treatment of moist air. Over many decades, the dual role of heat exchangers of AC chillers for the sensible and latent cooling of space has hindered the thermal-lift reduction in the refrigeration cycle due to the requirements of water vapor removal at dew-point and heat rejection to the ambient air. These practical constraints of AC chillers have resulted in the leveling of energy efficiency of mechanical vapor compressors (MVC) for many decades. One promising approach to energy efficiency improvement is the decoupling of dehumidification from sensible processes so that innovative but separate processes can be applied. In this paper, an advanced microwave dehumidification method is investigated in the laboratory, where the microwave (2.45 GHz) energy can be irradiated onto the dipole structure of water vapor molecules, desorbing rapidly from the pores of adsorbent. Results show a significant improvement in performance for microwave dehumidification, up to fourfold, as compared to data available in the literature. [ABSTRACT FROM AUTHOR]

Adsorption heat transformers (AHTs) are considered as promising systems for upgrading waste heat to a higher temperature. The cycle operates among three temperature reservoirs: (i) heat sink at the low temperature (TL), (ii) heat source at the medium temperature (TM), and (iii) heat supply at the high temperature (TH). In the present study, the performance the AHT cycle was analyzed for possible applications in the waste heat upgrade and thermal desalination. An equilibrium model was developed using adsorption characteristics and isotherm data. Five types of commercially available silica gels and three types of zeolites were investigated as adsorbents. Nonlinear optimization technique was utilized for the determination of the intermediate pressure and uptake for preheating and precooling phase of the AHT cycle. The performance parameters in terms of useful heat ratio and condensation heat ratio were determined and compared for the reservoir temperatures at 30 °C (TL)—60 °C (TM)—80 °C (TH). Parametric evaluation of the performance parameters was carried out based on the variation in gross temperature lift, as well as the heat exchanger mass ratio. It was found out that reduction in the gross temperature lift had a positive impact on the useful heat ratio and a negative influence on the condensation heat ratio of the AHT cycle. Significant variations in the maximum adsorption capacity and slope of the isosteric heat of adsorption across various adsorption pairs containing zeolites were observed. As a result, AQSOA-Z01 zeolite exhibited the highest heat exchange values of the AHT cycle in the range of ~ 320–370 kJ per kg of adsorbent. On the contrary, type AQSOA-Z02 zeolite displayed the lowest corresponding values in the range of ~ 60–90 kJ kg-1 of adsorbent. On the other hand, variation across the different silica gel adsorbents was comparatively smaller because of similar isotherm and isosteric heat of adsorption characteristics. This study will assist the research on the theoretical development of the AHT cycle via material selection and system design optimization. [ABSTRACT FROM AUTHOR]

The desiccant dehumidification system can separate the latent heat and sensible heat in the air-conditioning system and achieve energy savings by removing latent heat. Industrial waste heat and renewable energy could be utilized in desiccant dehumidification systems, where the desorption process can be performed below 70 °C. The vapor pressure and temperature of the regenerating air dictate the desorption process corresponding to the isotherm properties. This study has focused on the effects of various temperatures and humidity ratios of regeneration air on the performance of a desiccant dehumidifier using a polymer as an adsorbent. Experiments were performed using the regeneration air with the humidity ratios of 0.005 kg kg−1, 0.010 kg kg−1, 0.015 kg kg−1, and 0.020 kg kg−1, while the air temperatures were varied from 40 °C to 70 °C. The evaluation of this study employs the adsorption/desorption amount, average moisture removal capacity, and latent energy ratio (LER) of the regeneration process as key performance indexes. At the regeneration temperature of 68 °C, the peak desorption amount at the humidity ratio of 0.005 kg kg−1 and 0.010 kg kg−1 both reached 0.011 kg kg−1. The results indicated that the higher desorption temperature led to a higher desorption amount. Besides, with the increased desorption temperature, the average moisture removal capacity increases. In contrast, the high humidity ratio of regeneration air resulted in a weak dehumidification ability. Lower regeneration temperature was difficult to apply to regenerate the polymer-based desiccant under a high-humidity-ratio atmosphere. To attain a high LER, a lower humidity ratio of dry air and regeneration temperature was preferred. The regeneration air with a humidity ratio of 0.020 kg kg−1 is not suitable to apply in the dehumidification system in the temperature range of 40–70 °C. [ABSTRACT FROM AUTHOR]

Despite highest energy potential, solar energy is only available during diurnal period with varying intensity. Therefore, owing to solar intermittency, solar energy systems need to operate in standalone configuration for steady power supply which requires reliable and sustainable energy storage. Hydrogen production has proved to be the most reliable and sustainable energy storage option for medium and long term operation. However, at the first priority, solar energy must be captured with high efficiency, in order to reduce the overall size of the system and energy storage. Multi-junction solar cells (MJCs) provide highest energy efficiency among all of the photovoltaic technologies and the concentrated photovoltaic (CPV) system concept makes their use cost effective. However, literature is lacking the performance model and optimization strategy for standalone operation of the CPV-hydrogen system. In addition, there is no commercial tool available that can analyze CPV performance, utilizing multi-junction solar cell. This paper proposes the performance model for the CPV-hydrogen systems and the multi-objective optimization strategy for its standalone operation and techno-economic analysis, using micro genetic algorithm (micro-GA). The electrolytic hydrogen production with compression storage and fuel cell, is used as energy storage system. The CPV model is verified for the experimental data of InGaP/InGaAs/Ge triple junction solar cell. An optimal CPV system design is provided for uninterrupted power supply, even under seasonal weather variations. Such approach can be easily integrated with commercial tools and the presented performance data can be used for the design of individual components of the system. [ABSTRACT FROM AUTHOR]

Owing to the diverse photovoltaic (PV) systems’ design and technology, as well as the dynamic nature of insolation data received on the aperture surfaces, the instantaneous output from a PV system fluctuates greatly. For accurate performance estimation of a large PV field, the long term performance as electrical output is a more rational approach over the conventional testing methods, such as at Standard Testing Conditions (STC) and at the Nominal Operating Cell Temperature (NOCT) available hitherto. In this paper, the long-term performances of concentrated PVs (Cassegrain reflectors and Fresnel lens) with 2-axes tracking and a variety of PV systems, namely the stationary flat-plate PV (mono-crystalline, poly-crystalline and thin-films CIS types), is presented over a period of one year for the merit comparison of system design, under the tropical weather conditions of Singapore. From the measured field performances, the total energy output of 240.2 kW h/m 2 /year is recorded for CPV operation in Singapore, which is nearly two folds higher than the stationary PV panels. [ABSTRACT FROM AUTHOR]

The economics of seawater desalination processes has been continuously improving as a result of desalination market expansion. Presently, reverse osmosis (RO) processes are leading in global desalination with 53% share followed by thermally driven technologies 33%, but in Gulf Cooperation Council (GCC) countries their shares are 42% and 56% respectively due to severe feed water quality. In RO processes, intake, pretreatment and brine disposal cost 25% of total desalination cost at 30–35% recovery. We proposed a tri-hybrid system to enhance overall recovery up to 81%. The conditioned brine leaving from RO processes supplied to proposed multi-evaporator adsorption cycle driven by low temperature industrial waste heat sources or solar energy. RO membrane simulation has been performed using WinFlow and IMSDesign commercial softwares developed by GE and Nitto. Detailed mathematical model of overall system is developed and simulation has been conducted in FORTRAN. The final brine reject concentration from tri-hybrid cycle can vary from 166,000 ppm to 222,000 ppm if RO retentate concentration varies from 45,000 ppm to 60,000 ppm. We also conducted economic analysis and showed that the proposed tri-hybrid cycle can achieve highest recovery, 81%, and lowest energy consumption, 1.76 kWh elec /m 3 , for desalination reported in the literature up till now. [ABSTRACT FROM AUTHOR]

An investigation of a sea water reverse osmosis desalination facility located in western Saudi Arabia has shown that aquifer treatment of the raw sea water provides a high degree of removal of natural organic matter (NOM) that causes membrane biofouling. The aquifer is a carbonate system that has a good hydraulic connection to the sea and 14 wells are used to induce sea water movement 400 to 450 m from the sea to the wells. During aquifer transport virtually all of the algae, over 90% of the bacteria, over 90% of the biopolymer fraction of NOM, and high percentages of the humic substance, building blocks, and some of the low molecular weight fractions of NOM are removed. Between 44 and over 90% of the transparent exopolymer particles ( TEP) are removed with a corresponding significant reduction in concentration of the colloidal fraction of TEP. The removal rate for TEP appears to be greater in carbonate aquifers compared to siliciclastic systems. Although the production wells range in age from 4 months to 14 years, no significant difference in the degree of water treatment provided by the aquifer was found. [ABSTRACT FROM AUTHOR]

Concentrated photovoltaic (CPV) system provides highest solar energy conversion efficiency among all the photovoltaic technologies and provides the most suitable option to convert solar energy into hydrogen, as future sustainable energy carrier. So far, only conventional flat plate PV systems are being used for almost all of the commercial applications. However, most of the studies have only shown the maximum efficiency of hydrogen production using CPV. In actual field conditions, the performance of CPV-Hydrogen system is affected by many parameter and it changes continuously during whole day operation. In this paper, the daily average and long term performances are proposed to analyze the real field potential of the CPV-Hydrogen system, which is of main interest for designers and consumers. An experimental setup is developed and a performance model is proposed to investigate the average and long term production potential of CPV-Hydrogen system. The study is carried out in tropical weather of Singapore. The maximum CPV efficiency of 27–28% and solar to hydrogen (STH) efficiency of 18%, were recorded. In addition, the CPV-Hydrogen system showed the long term average efficiency of 15.5%, for period of one year (12-months), with electrolyser rating of 47 kWh/kg and STH production potential of 218 kWh/kg. Based upon the DNI availability, the system showed hydrogen production potential of 0.153–0.553 kg/m 2 /month, with average production of 0.43 kg/m 2 /month. However, CPV-Hydrogen system has shown annual hydrogen production potential of 5.162 kg/m 2 /year in tropical weather of Singapore. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid desalination system consisting of vacuum membrane distillation (VMD) and adsorption desalination (AD) units, designated as VMD-AD cycle, is proposed. The synergetic integration of the VMD and AD is demonstrated where a useful effect of the AD cycle is channelled to boost the operation of the VMD process, namely the low vacuum environment to maintain the high pressure gradient across the microporous hydrophobic membrane. A solar-assisted multi-stage VMD-AD hybrid desalination system with temperature modulating unit is first designed, and its performance is then examined with a mathematical model of each component in the system and compared with the VMD-only system with temperature modulating and heat recovery units. The total water production and water recovery ratio of a solar-assisted 24-stage VMD-AD hybrid system are found to be about 21% and 23% higher, respectively, as compared to the VMD-only system. For the solar-assisted 24-stage VMD-AD desalination system having 150 m 2 of evacuated-tube collectors and 10 m 3 seawater storage tanks, both annual collector efficiency and solar fraction are close to 60%. [ABSTRACT FROM AUTHOR]

The hybrid indirect evaporative cooling-mechanical vapor compression (IEC-MVC) process is deemed a promising cooling system for hot and humid areas. It possesses the merits of high energy efficiency and strong capability of temperature and humidity control. Herein, we provide an overview of the state-of-the-art investigations over different aspects of the hybrid IEC-MVC process. Firstly, we evaluate the potential of IEC as a pre-cooler and heat-recovery device. Then, we compare the energy efficiency of IEC-MVC with standalone MVC and summarize its long-term energy-saving potential under specific weather conditions. Subsequently, we discuss the economic viability and water consumption of the hybrid process. These studies form a solid foundation for the future installation of the IEC-MVC system. [ABSTRACT FROM AUTHOR]

Concentrated photovoltaic (CPV) system utilizing multi-junction solar cells, is the main focus for current research, offering highest efficiency among all photovoltaic systems. The main aspect of CPV system is the design and performance of concentrating assembly, as it determines the performance of whole CPV system. However, the conventional design of CPV concentrating assembly dedicates one concentrator for each solar cell, in which single concentrator is capable to concentrate solar radiation onto single solar cell. This paper proposes a novel concentrating assembly for CPV system, which is designed to concentrate solar radiation onto four multi-junction solar cells with a single set of concentrators. The proposed design not only can reduce the number of concentrators and assembly efforts for CPV systems, but also achieved an acceptance angle of 1°. In this paper, the proposed multi-leg homogeniser CPV concentrating assembly is designed, developed, experimentally tested and verified through ray tracing simulation. The paper also discuss the development of mini, precise and accurate but cost effective two axis solar tracker for CPV system, which can be installed at any location even at rooftop of residential buildings, unlike conventional large scale CPV systems. Moreover, through the electrical rating analysis of the developed CPV system, its performance can be accurately estimated in any region. [ABSTRACT FROM AUTHOR]

Owing to the intermittent solar irradiance from cloud cover in the diurnal period and unavailability at night time, the practical design of a solar system requires energy backup storage for an uninterrupted supply or for off-grid operation. However, for highly efficient CPV (concentrated photovoltaic) system, the literature is lacking for energy management and optimization algorithm and tool for standalone operation. In this paper, a system with CPV and electrolyser is presented where beam irradiance of sunlight is harnessed to convert the instantaneously generated electricity into useful Hydrogen/Oxygen gas, where they can be stored and re-used for downstream applications such as the fuel cells, etc. The multi-variable design and multi-objective optimization strategies are proposed and presented for a standalone operation of the CPV-Hydrogen system as well as their system performances, particularly electrical rating of CPV based upon the real weather data of Singapore. [ABSTRACT FROM AUTHOR]

Thin and robust composite membranes comprising stainless steel scaffold, fine and porous TiO 2 and polyvinyl alcohol/lithium chloride were fabricated and studied for air dehumidification application. Higher hydrophilicity, sorption and permeation were observed for membranes with increased lithium chloride content up to 50%. The permeation and sorption properties of the membranes were investigated under different temperatures. The results provided a deeper insight into the membrane water vapor permeation process. It was specifically noted that lithium chloride significantly reduces water diffusion energy barrier, resulting in the change of permeation energy from positive to negative values. Higher water vapor permeance was observed for the membrane with higher LiCl content at lower temperature. The isothermal air dehumidification tests show that the membrane is suitable for dehumidifying air in high humid condition. Additionally, results also indicate a trade-off between the humidity ratio drop with the water vapor removal rate when varying air flowrate. [ABSTRACT FROM AUTHOR]

Adsorption heat transformer (AHT) cycle is capable of upgrading the low-grade waste heat to a higher temperature. The maximum temperature lift of the AHT cycle can represent its theoretical performance limit. However, such a metric is currently absent from the literature due to the scarcity of fundamental studies on the heat upgrading sorption cycles. Therefore, in the present study, three models are proposed to derive the 'maximum temperature lift' of a typical AHT cycle: (i) heat engine heat pump representation, (ii) the 2 n d law of thermodynamic formulation, and (iii) complete preheating. The first two models are developed based on the reversible cycle approach, whereas the 3 r d model incorporates adsorbed phase properties. Thus, the first two models might be considered as the formulations for the thermodynamic temperature limit (lift) of an AHT cycle while the 3 r d model is specific to the nature of a particular adsorbent + adsorbate pair which might be close to practical applications. The reversible models predict a maximum temperature lift of 22 ∘C to 58 ∘C for heat source temperatures between 50 ∘C to 80 ∘C. The 3 r d model exhibits lower values of maximum temperature lift compared to the reversible models, owing to the inclusion of material properties in its formulation. The performance of the models is demonstrated by determining the maximum temperature lift of four water-based adsorption working pairs, each featuring distinct IUPAC (International Union of Pure and Applied Chemistry) isotherm types. This study will help propel the working pair selection and the thermodynamic modeling of sorption cycles to achieve its near maximum capability. • Developed three models for the thermodynamic temperature limit (lift) of AHT cycles. • Maximum temperature lift denotes heat upgrading capability of the AHT cycle. • Investigated the effect of material properties on maximum temperature lift. • Demonstrated the applicability of the models for AHT using IUPAC isotherms. [ABSTRACT FROM AUTHOR]

This study presents a two-axis solar tracking system equipped with a small concentrator module for electricity generation through a multijunction solar cell. The system can accurately track the sun without the need of calibration for an extended period and operate as a stand-alone system. High-precision solar tracking was achieved by a combination of open-loop and closed-loop controls. A camera tracking sensor was introduced as a feedback device in closed-loop control. Two different types of solar concentrator modules were designed and fabricated. Their concentration ratios were analyzed against solar tracking errors by means of ray tracing software. One is made up of a paraboloidal primary concentrator and a paraboloidal secondary reflector, whereas the other has a paraboloidal primary concentrator and a hyperboloidal secondary reflector. Both modules showed an almost identical concentration ratio of 610 provided that the solar tracker is pointing perfectly at the sun. However, their performance differs considerably when tracking error is present. The maximum power output was obtained near solar noon with multijunction cells, whose average solar conversion efficiency was 21%, much higher than that of conventional photovoltaic systems. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The adsorption characteristics of microporous ferroaluminophosphate adsorbent (FAM-Z01, Mitsubishi Plastics) are evaluated for possible application in adsorption desalination and cooling (AD) cycles. A particular interest is its water vapor uptake behavior at assorted adsorption temperatures and pressures whilst comparing them to the commercial silica gels of AD plants. The surface characteristics are first carried out using N2 gas adsorption followed by the water vapor uptake analysis for temperature ranging from 20°C to 80°C. We propose a hybrid isotherm model, composing of the Henry and the Sips isotherms, which can be integrated to satisfactorily fit the experimental data of water adsorption on the FAM-Z01. The hybrid model is selected to fit the unusual isotherm shapes, that is, a low adsorption in the initial section and followed by a rapid vapor uptake leading to a likely micropore volume filling by hydrogen bonding and cooperative interaction in micropores. It is shown that the equilibrium adsorption capacity of FAM-Z01 can be up to 5 folds higher than that of conventional silica gels. Owing to the quantum increase in the adsorbate uptake, the FAM-Z01 has the potential to significantly reduce the footprint of an existing AD plant for the same output capacity. [ABSTRACT FROM AUTHOR]

The heat of adsorption of methane, ethane, carbon dioxide, R-507a and R-134a on several specimens of microporous activated carbons is derived from experimental adsorption data fitted to the Dubinin-Astakhov equation. These adsorption results are compared with literature data obtained from calorimetric measurements and from the pressure-temperature relation during isosteric heating/cooling. Because the adsorbed phase volume plays an important role, its dependence on temperature and pressure needs to be correctly assessed. In addition, for super-critical gas adsorption, the evaluation of the pseudo-saturation pressure also needs a judicious treatment. Based on the evaluation of carbon dioxide adsorption, it can be seen that sub-critical and super-critical adsorption show different temperature dependences of the isosteric heat of adsorption. The temperature and loading dependence of this property needs to be taken into account while designing practical systems. Some practical implications of these findings are enumerated. [ABSTRACT FROM AUTHOR]

This paper presents the adsorption isotherm experiment of Methane and Maxsorb III activated carbon that was conducted and analyzed at temperatures from 5 to 55 °C and pressures up to 2.2 MPa in a volumetric apparatus. It is a complementary to the previous efforts by ways of analyzing the importance between charging and discharging rate, temperature increase and reduce of the bed, the heat transfer process, and the cylinder cooling and heating requirements during the charging and discharging of adsorbed natural gas. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the modeling, design, and testing of a high flux and yet compact two-phase CPU cooler, with excellent attributes of low thermal resistance that are derived from the intrinsic design features of phase change phenomena and minimal vapor pressure drop of the device. For the same footprint of a conventional cooler, the prototype rejects more than twice the capacity of CPUs of today. The unique design minimizes its overall size and yet provides adequate area for forced convection cooling. Testing was conducted over an assorted heat loads and air flow rates flowing through the fins, achieving a best performance of 0.206K/W of device thermal resistance at a rating of 203W under an air flow rate of 0.98m3/min. The prototype device is orientation free where a 90° tilt could perform at the same rating conditions. [Copyright &y& Elsevier]

Abstract: We experimentally show that for the same heat exchanger inventory allocation, a four-bed adsorption chiller delivers a 12% higher ultimate cooling capacity than its two-bed counterpart. In addition it delivers a significantly improved quality of instantaneous cooling than a two-bed chiller at the same cooling capacity. The COP-enhancing feature of a passive heat recovery scheme that does not involve additional pumping action or valves is experimentally proven. It improves the COPs of a two-bed chiller and a four-bed chiller by as much as 38 and 25%, respectively, without any effect on their cooling capacities. The highest COPs achieved with a two-bed and four-bed chillers are 0.46±0.02 and 0.45±0.02, respectively. These are measured at a hot-water inlet temperature of 85°C, cooling-water inlet temperature of 29.4°C and chilled-water inlet temperature of 12.2°C. [Copyright &y& Elsevier]

Integration of energy recovery section with thermal desalination systems improves their performance from thermodynamics, economics, and environmental viewpoints. This is because it significantly reduces input energy, heat transfer area, and capital cost requirements. Above all, the system outlet streams can achieve thermal equilibrium with the environment by supplying heat for useful preheating purposes thus reducing the environmental impacts. The plate heat exchangers are generally employed for this purpose as preheaters. The current paper presents a comprehensive investigation and optimization of these heat exchangers for thermal desalination systems applications. An experimentally validated numerical model employing Normalized Sensitivity Analysis and Genetic Algorithm based cost optimization is developed to investigate their performance at assorted operating conditions. The analysis showed that the heat transfer coefficient, pressure drop, and outlet water cost were improved by an increase in feed flow rate. However, with an increased flow rate, the comprehensive output parameter (h/ΔP) decreased due to the high degree increase in pressure drop. Moreover, an increase in the chevron angle reduced the heat transfer coefficient, pressure drop, and water cost. Finally, the optimization lowered the heat transfer area by ~79.5%, capital investment by ~62%, and the outlet cost of the cold stream by ~15.7%. The operational cost is increased due to the increased pressure drop but the overall impact is beneficial as C total of equipment is reduced by ~52.7%. [ABSTRACT FROM AUTHOR]

The intermittency of renewable energy resources which only have localized availability with low energy density, is the main reasons for our reliance on conventional fossil fuels. If steady supply and high energy quality can be achieved then solar energy potential is enough to meet the global energy demand. Heat and electricity both are equally important forms of derived energies. In this paper, an innovative configuration of solar energy system for simultaneous need of electricity and high grade thermal energy, is presented and discussed along with the long term energy storage solution. The proposed CPV/T system, with hydrogen based electrical and MgO based thermal storage, can produce electricity and high-temperature thermal energies at efficiency of 30% and 70% respectively. The CPV-Hydrogen configuration achieved Solar to Hydrogen efficiency of 19%. On the other hand, the MgO based TES system obtained 80% material storage efficiency at 400 °C which can be easily achieved with the concentrated thermal energy density of 240 Suns. • Novel CPV/T system for electricity and high grade heat production from single unit. • Innovative optical design with multiple outlets of concentrated radiations. • Solar electricity was converted as Hydrogen with 19% efficiency. • Heat of 240 Suns density was stored in MgO based TES with 80% conversion ratio. [ABSTRACT FROM AUTHOR]

Summary: This paper deals with the development and operation of a mechanical vapor recompression (MVR) desalination system with improved energy efficiency in harnessing wind energy, which is non‐dispatchable. Its design, construction, and operation details are presented in this paper. Especially, the main focus of developing the system was on the operation of the system in conjunction with variable loads of new and renewable power sources, in particular, varying wind power. That is, the present work has been carried out to assess the feasibility of its operation in light of capacity modulation to match the power generated under various wind speeds. Optimal operation modes of the system were studied, in which single‐ and double‐effect operations were analyzed for their improvement in energy efficiency. The compression ratio of the proposed MVR system was 1.55 at an inverter speed of 55 Hz, which agreed well with its design value. Operation of the main heat exchanger remained stable within the limits of its operable range, although the temperature differences in the main heat exchanger did not remain constant because of the pressure variations in the evaporator. The daily freshwater yield was between 28 and 51 tons. The power consumption per ton of freshwater produced was about 43 kW for a single effect and about 23 kW for a double effect, which is about twice as efficient. [ABSTRACT FROM AUTHOR]

• A novel indirect evaporative cooler is proposed and tested experimentally. • A temperature drop and heat transfer coefficient are achieved up to 20 °C, and 30 W/m2 K. • A novel heat transfer coefficient correlation is proposed with ±5% accuracy. • The proposed correlation can be used for commercial-scale system design. A remarkable surge in cooling demand is observed in the last decades. Currently, the cooling market is dominated by mechanical vapor compression chillers which are energy intensive and use harmful chemical refrigerants. Therefore, the current focus of the current research in cooling is the development of unconventional, sustainable cooling systems. In this regard, indirect evaporative coolers have shown significant potential (particularly under hot-dry climates) with high energy efficiency, low cost, water-based sustainable operation, and benign emissions. However, these systems are in the development stage and have not yet been fully commercialized because of certain design challenges. An innovative indirect evaporative cooler is proposed, fabricated, and experimentally tested in this study. Particularly, the study is focused on the development of heat transfer coefficient correlation for the system for commercial-scale design and expansion. This is because the earlier available correlation is based on simple airflow between parallel plates assumption and does not incorporate the effect of the evaporative potential of the system resulting in under/over-estimation of the heat transfer characteristics. The results showed that the proposed system achieved a temperature drop of 20 °C, a cooling capacity of around 180 W, and an overall heat transfer coefficient of up to 30 W/m2K. Moreover, the study presents an experiment-regression-based heat transfer coefficient correlation that satisfactorily captures the effect of outdoor air temperature and airflow rate ratio which are critical in the design of evaporative coolers. The proposed correlation showed a high (±5%) with experimental data thus making it suitable for the future design of IEC systems over assorted operating scenarios. [ABSTRACT FROM AUTHOR]

Due to the fast thermal response and high solar energy efficiency, the passive interfacial solar still has become a reliable scheme for distributed water supply. In this paper, the thermodynamic performance of the interfacial solar still under different structures and operating conditions is studied experimentally, which provides an optimization direction for strengthening the distillation process. Firstly, based on the different Ra numbers, the calculation correlations for diffusion and convective mass transfer in the air interlayer were established to accurately predict the thermodynamic model of the interfacial distillation process. Then, the temperature distribution of the condenser and the growth process of condensate droplets were analyzed with the constant evaporation temperature. Simultaneously, the influence of different condensing structures and external variables on the heat transfer performance was compared. The results show that the interfacial still could obtain maximum evaporation heat under the vertical operation condition. When the evaporation temperature is 70 °C, the temperature difference between the wick evaporator and condenser can be increased by 49.5 %, after coupling a finned condenser with the aspect ratio of 7.2. In addition, a narrower interlayer spacing and a larger evaporation temperature could bring a higher equivalent heat transfer rate and evaporation efficiency. In a sunny weather, the interfacial solar still coupled with an extended condenser can reach a 4.81 kg/m2/day water yield and a 0.486 daily gained output ratio under 1 cm interlayer spacing. • The optimum operating parameters of the interfacial still were determined. • Finned condenser improves temperature difference and water yield. • Reducing interlayer spacing could enhance evaporation efficiency. • The optimized interfacial still could generate 4.81 kg/m2/day yield. [ABSTRACT FROM AUTHOR]

The distinct interaction of adsorbate-adsorbent pair is attributed to the characteristics of heterogeneous surface and structure of porous materials. In material science, the porous structure is modified in response to certain applications. Backed by the chemical recipes, such conventional approach rely on the material characterization techniques to verify the resultant porous structure and its interaction with the adsorbate molecules. Such a practice is best assisted by a theoretical approach that can pre-define the required heterogeneous structure of porous surfaces and its role in selective adsorbate-adsorbent interaction, to facilitate material scientists for the synthesis of only those energy sites which can enhance or tailor its responses for a certain application or target. It has been reported here that the understanding of porous structure in terms of energy sites and their distribution, which controls the adsorbate-adsorbent interaction, is the key for porous surface engineering. Understanding of such porous surface characteristics empower the scientists to alter kinetics and thermodynamics of material according to the 'sweet spots' of an application. Therefore, a theoretical framework, to express the energy sites and their distribution over the porous heterogeneous surface, is demonstrated here as a prerequisite criterion for porous material development and characterization. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a mathematical model to enable a more in-depth understanding of the combined heat and mass transfer processes of a counter-flow indirect evaporative cooler operating in semi-arid regions. A series of simulation was conducted to compare the performances between a single-purge and four-purge configurations. Furthermore, the effect of several parameters on the performance of the single-purge configuration was investigated under the baseline condition. The developed model was validated against experimental data from literature to within 2% discrepancy. Key results revealed that the single-purge configuration produced higher cooling capacity (around 20% higher), as well as higher dew-point effectiveness under the same operating conditions. A parametric study was also made on the single-purge configuration. The results revealed that lower product air temperature and higher dew-point effectiveness were achieved with longer channel length and larger purge ratio. However, the maximum cooling capacity approached its maximum with longer channel length and 35% purge ratio. [ABSTRACT FROM AUTHOR]

Adsorption heat transformer (AHT) cycles, unlike adsorption cooling cycles, upgrade the heat source to a higher temperature. Despite the renewed interest in the AHT cycles, its performance enhancement schemes along with their impacts are yet to be explored extensively. Heat and mass recovery schemes on the adsorption cooling/heating cycles have been extensively studied. However, AHT cycles are fundamentally different from those cycles since the AHT cycles employ isothermal-adiabtic processes. Thus, similar impacts of the heat and mass recovery scheme as in the cooling/heating cycles cannot be expected in AHT cycles. Therefore, the impacts and limitations of the internal heat recovery scheme on the AHT cycle are investigated in the current study. The heat recovery scheme aims to minimize the requisite uptake consumption for preheating the adsorber bed by recovering the sensible heat between two adsorber beds having different temperatures. This sensible heat exchange is modeled using modified energy-balance equations to capture the non-linearity of the adsorption process. The preheating uptake loss decreases from 0.014 kg/kg to 0.007 kg/kg at the heat source-heat supply temperature combination of 60 °C–80 °C due to the maximum possible heat recovery in the AHT cycle. As a result of the reduced preheating uptake loss, approximately 5% and 10% increase in the useful heat ratio and exergy efficiency of the AHT cycle, respectively are obtained. This modified AHT cycle further improves the performance ratio of the hybrid AHT-MED (multi-effect distillation) system from 4.6 to 4.9 at the heat source temperature of 58 °C. Furthermore, a parametric analysis of the cycle's performance metrics has been conducted for various degrees of heat recovery, representing the effect of realistic heat exchanger effectiveness during the recovery process. This study will help propel the theoretical development of the adsorption-based thermodynamic systems. [Display omitted] • Internal heat recovery scheme evaluated in adsorption heat transformer cycle. • Reduced preheating uptake loss via isosteric heating of the bed. • Increased UHR and exergy efficiency caused by the heat recovery in the AHT cycle. • Parametric analysis was carried out based on amount of heat recovery. • Improved performance ratio of AHT + MED system with internal heat recovery [ABSTRACT FROM AUTHOR]

Solar energy being intermittent in nature, can provide a sustainable, steady and high density energy source when converted into electrolytic hydrogen. However, in current photovoltaic market trend with 99% conventional single junction PV panels, this cannot be achieved efficiently and economically. The advent of the multi-junction solar cells (MJCs), with cell-efficiency exceeding 46%, has yet to receive wide spread acceptance in the current PV market in form of concentrated photovoltaic (CPV) system, because of its system design complexity, limiting its application scope and customers. The objective of this paper is to develop a low cost compact CPV system that will not only eliminate its application and installation related restrictions but it is also introducing a highly efficient and sustainable photovoltaic system for common consumer, to convert intermittent sunlight into green hydrogen. The developed CPV system negates the common conviction by showing two times more power output than the flat plate PV, in tropical region. In addition, sunlight to hydrogen conversion efficiency of 18% is recorded for CPV, which is two times higher than alone electricity production efficiency of flat plate PV. [ABSTRACT FROM AUTHOR]

In humid environments, decoupling the latent and sensible cooling loads - dehumidifying - can significantly improve chiller efficiency. Here, a basic limit for dehumidification efficiency is established from fundamental thermodynamics. This is followed by the derivation of how this limit is modified when the pragmatic constraint of a finite flux must be accommodated. These limits allow one to identify promising system modifications, and to quantify their impact. The focus is on vacuum-based membrane dehumidification. New high-efficiency configurations are formulated, most notably, by coupling pumping with condensation. More than an order-of-magnitude improvement in efficiency is achievable. It is contingent on water vapor exiting at its saturation pressure rather than at ambient pressure. Sensitivity studies to recovery ratio, temperature, relative humidity and membrane selectivity are also presented. [ABSTRACT FROM AUTHOR]

Energy-water-environment nexus is very important to attain COP21 goal, maintaining environment temperature increase below 2 °C, but unfortunately two third share of CO 2 emission has already been used and the remaining will be exhausted by 2050. A number of technological developments in power and desalination sectors improved their efficiencies to save energy and carbon emission but still they are operating at 35% and 10% of their thermodynamic limits. Research in desalination processes contributing to fuel World population for their improved living standard and to reduce specific energy consumption and to protect environment. Recently developed highly efficient nature-inspired membranes (aquaporin & graphene) and trend in thermally driven cycle's hybridization could potentially lower then energy requirement for water purification. This paper presents a state of art review on energy, water and environment interconnection and future energy efficient desalination possibilities to save energy and protect environment. [ABSTRACT FROM AUTHOR]

This paper presents an underwater solar concentrating photovoltaic-membrane distillation (CPV-MD) integrated system for regions of coastal cities and islands where land resources are insufficient and suffer from critical shortages in electricity and freshwater. A deformable solar concentrator that works underwater is innovatively designed and matched with the photovoltaic-membrane distillation module. Given its application scenario, the integrated system is designed without metallic components to prevent seawater corrosion. The concentrator's optical characteristics are revealed via optical simulations. The results illustrate that the concentrator bears optimal optical performance when its elastic membrane's deformation ratio α is 0.25 and height ratio γ is 0.35. An experimental setup with a solar cell radius of 50 mm is developed and tested in actual weather to reveal its electricity and freshwater yield performance. It is found that the integrated system exhibits similar performance under the light incident angle of 0°and 10°. Additionally, for the experiment with average solar radiation of 514 W/m2, the integrated system's output power varies between 1.53 W and 1.0 W, with an average electrical efficiency of 3.16 %. The accumulated freshwater yield is 67.8 g, with an average water yield efficiency of 28.5 %. This work may provide a new perspective on underwater solar energy utilization. • An underwater concentrating photovoltaic-membrane distillation system is proposed. • An underwater solar concentrator with wide range of light reception angle is designed. • Test results reveal that it exhibits similar performance at incident angle of 0° and 10°. • Its electrical and freshwater yield efficiency can reach 3.1 % and 28.5 %, respectively. [ABSTRACT FROM AUTHOR]

Current commercial CPV systems are designed as large units which are targeted to be installed in open desert fields with high DNI availability. It appeared that the CPV is among some of those technologies which gained very little attention of people, with less customers and market. For conventional PV systems, the installations at the rooftop of commercial and residential buildings have a significant share in the total installed capacity of PV systems. That is why for most of the countries, the PV installations at the rooftop of commercial and residential buildings are aimed to be increased to half of total installed PV. On the other hand, there is no commercial CPV system available to be suitable for rooftop operation, giving motivation for the development of CPV field of compact systems. This paper discusses the development of a CPV field for the rooftop operation, comprising of compact CPV system with cost effective but highly accurate solar tracking sensor and wireless master slave control. In addition, the performance of the developed CPV systems is evaluated for production of hydrogen, which can be used as energy carrier or energy storage and a maximum solar to hydrogen efficiency of 18% is obtained. However, due to dynamic nature of the weather data and throughout the day variations in the performance of CPV and electrolyser, the solar to hydrogen performance is proposed to be reported as daily and long term average efficiency. The CPV-Hydrogen system showed daily average conversion efficiency of 15%, with solar to hydrogen production rate of 218 kW h/kg. [ABSTRACT FROM AUTHOR]

Multi-bed adsorption cycle with the internal heat recovery between the condenser and the evaporator is investigated for desalination application. A numerical model is developed for a 4-bed adsorption cycle implemented with the master-and-slave configuration and the aforementioned internal heat recovery scheme. The present model captures the reversed adsorption/desorption phenomena frequently associated with the unmatched switching periods. Mesoporous silica gel and water vapor emanated from the evaporation of the seawater are employed as the adsorbent and adsorbate pair. The experimental data and investigation for such configurations are reported for the first time at heat source temperatures from 50 °C to 70 °C. The numerical model is validated rigorously and the parametric study is conducted for the performance of the cycle at assorted operation conditions such as hot and cooling water inlet temperatures and the cycle times. The specific daily water production ( SDWP ) of the present cycle is found to be about 10 m 3 /day per tonne of silica gel for the heat source temperature at 70 °C. Performance comparison is conducted for various types of adsorption desalination cycles. It is observed that the AD cycle with the current configuration provides superior performance whilst is operational at unprecedentedly low heat source temperature as low as 50 °C. [ABSTRACT FROM AUTHOR]