Operating logic of thermal energy storage systems

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Thermal energy storage systems are integrated with concentrated solar thermal power plants to extend their operation beyond sunshine hours. They can also be used to boost their output during cloudy conditions. There are many types of thermal energy storage systems, but this article seeks to develop a broad operating logic that is applicable to most schemes. The article will describe how heat is moved into and out of thermal energy storage systems during operation, namely their charging and discharging processes.dc201

Performance model of Shams I solar power plant

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.A study of Shams I solar power plant in Abu Dhabi has been conducted to generate a performance model via a spreadsheet. The plant consists of 192 loops containing single-axis parabolic trough collectors. These collectors track the sun and focus sunlight onto a Heat Transfer Fluid (HTF) flowing in an absorber running in their focal line. That causes the temperature of the HTF to rise, which then heats the water flowing in a separate loop. This results in the formulation of vapor that is sent to a turbine. A generator is connected to the shaft of the turbine and it generates electricity due to the rotation of the shaft (caused by the expanding steam) [1]. The spreadsheet computes the annual output of the plant in1-hour increments. Input data columns include: solar radiation, ambient temperature, humidity, wind speed, time of day, day of year, and other geographical and optical constants.dc201

Ultrasonication and RSM-based optimization of antioxidant activity, saccharide composition and fatty acids from Phoenix dactylifera L. Medjool date seeds influenced by ethanol

In response with the demand in date industry finding on sustainable solution for date seeds management and its bioactive rich constituent, current study envisaged the optimum condition for the ultrasound extraction of Phoenix dactylifera L. Medjool date seeds and its antioxidative activity by employing a three-level three-factor Box–Behnken design via response surface methodology (RSM). Ethanol (EtOH) concentration (50-80%), time (30-90 min) and temperature (40-70 °C) were the independent variables investigated for ABTS•+ scavenging antioxidant activity and subjected to analysis of variance (ANOVA). The optimum conditions for maximum antioxidant activity (60.93% ± 0.021) were achieved at 80% EtOH, 44 min and at 57 °C, where the effect of EtOH concentration were notably significant. The observed agreement between the experimental (60.93% ± 0.021) and predicted (60.35%) values indicated the employed model suitability while substantiates the successful implementation of RSM for optimizing extraction parameters. The optimized extract characterized through UPLC-QTOF/MS and GC-MS/MS, detailed the presence of saccharides (isomaltose, mannotriose and stachyose) and volatile compounds, namely 5 saturated fatty acids that encompassed within the 8.42% (w/w) of total fat obtained. This verifies the ability of the solvent mixture extracting fatty acids and saccharides even under high EtOH concentration

Theoretical and Experimental Simulation of Passive Vacuum Solar Flash Desalination

Experimental and theoretical simulations of a novel sustainable desalination process have been carried out. The simulated process consists of pumping seawater through a solar heater before flashing it under vacuum in an elevated chamber. The vacuum is passively created and then maintained by the hydrostatic balance between pressure inside the elevated flash chamber and outdoor atmospheric pressure. The experimental simulations were carried out using a pilot unit built to depict the proposed desalination system. Theoretical simulations were performed using a detailed computer code employing fundamental physical and thermodynamic laws to describe the separation process, complimented by experimentally based correlations to estimate physical properties of the involved species and operational parameters of the proposed system setting it apart from previous empirical desalination models. Experimental and theoretical simulation results matched well with one another, validating the developed model. Feasibility of the proposed system rapidly increased with flash temperature due to increased fresh water production and improved heat recovery. In addition, the proposed desalination system is naturally sustainable by solar radiation and gravity, making it very energy efficient

Thermodynamic Model and the Controlling Variables of Phosphate Lattice Loss

A thermodynamic model was developed based upon five equilibrium reactions to predict the limits of distribution of phosphates between the liquid and the solid phases in a reactor used to extract phosphoric acid from phosphate rock. A computer code was generated to carry out different simulations of the model using several inputs of temperatures and liquid phase sulfuric acid contents. Ideal Solution, Debye-Hückel, and Robinson-Guggenheim-Bates electrolyte activity coefficient models were employed alternately in each simulation to complete the thermodynamic model and the outputs were compared to one another. Experimental data of equilibrium constants were regressed to adjust the values of ΔCp° and ΔH° used in the simulations to obtain a more accurate representation of the thermodynamic equilibrium. Results for ionic strength, liquid phase pH, and phosphate lattice loss were used to analyze temperature and liquid phase sulfuric acid content effects on the reacting system. Completing the thermodynamic model with Ideal Solution and Debye- Hückel electrolyte activity coefficient models was found to bind all predictions of phosphate lattice loss. The model prediction of phosphate losses was found to give a lower bound to the real phosphate losses. Furthermore, decreasing temperature and increasing liquid phase sulfuric acid content was found to minimize phosphate lattice loss

The Effect of Storing Produced PV Power on the National Grid

The dramatic increase in renewable sources employment and the new trend to eliminate carbon emissions are the main reasons for using energy storage to overcome the fluctuation of Photovoltaic (PV) output. This paper aims to study the ability of PV solar system, to provide a significant fraction of utility systems energy demand in Jordan. MATLAB software was used to simulate algorithms in order to estimate the storage properties of Energy Capacity (EC), Power Capacity (PC), and Capacity Ratio (CR). These properties are mainly affected by the size of the PV system and the flexibility (ff) of the grid. The hourly generation data from the National Electric Power Company (NEPCO) were investigated to determine the most efficient way to feed PV-generated power into the grid. It was found that for flexibilities (ff) values of 0.7, 0.8, and 1, the No-Dump (ND) PV system, which is the largest PV system that could deliver all its annual production to the grid without any need of spillage of the PV system size were 566.3MW, 998.4MW and 1.6 GW respectively. Also, the relation between Energy Capacity of storage (EC) and Power Capacity (PC) was investigated, it was found that if storage installed with EC and PC equal to 24 GWh (almost 45% of average daily demand) and 3 GW (which is less than the peak hour demand) at ff=0.8, the penetration of PV energy will increase by 42% of annual demand compared with almost 10% without storage. Furthermore, if ff is increased to 1 in parallel to installing storage with energy capacity and power capacity equal to 52.7 GWh and 4.7GW, respectively, the PV penetration will increase to reach 68% of the annual demand compared to 16% without storage