In this paper, a multi-objective optimization approach is introduced to define a hybrid power supply system for a large scale RO- desalination plant. The target is to integrate a number of locally available energy resources to generate the electricity demand of the RO- desalination plant with minimizing both the electricity generation cost and the greenhouse gas emissions whereby carbon dioxide sequestration may be an option. The considered energy resources and technologies are wind turbines, solar PV, combined cycles with natural gas turbines, combined cycles with coal gasification, pulverized coal with flue gas desulfurization, and biomass combined heat and power CHP. These variable energy resources are investigated under different constraints on the renewable energy contribution. Likewise, the effect of carbon dioxide sequestration is included. Accordingly, five scenarios have been analyzed. Trade- offs between the minimum electricity generation cost and the minimum greenhouse gas emissions have been determined and represented in Pareto curves using the constraint method (epsilon). The results highlight that among the studied fossil fuel technologies, the integrated combined cycle natural gas turbines can provide considerable fraction of the needed power supply. Likewise, wind turbines are the most effective technology among renewable energy options. When CO2 sequestration applied, the costs increase and significant changes in the optimum combination of renewable energy resources have been monitored. In that case, solar PV starts to appreciably compete. The optimum mix of energy resources extends to include biomass CHP as well.

A kinetic study of three Egyptian agricultural wastes has been conducted at a heating rate of 5 o C/min using thermogravimetric analysis TGA. The kinetic parameters (order of reaction, activation energy, and frequency factor) have been determined from the TGA experiment measurements. The kinetic results indicate that the thermal degradation is a first order reaction. The activation energies (25.7 26.2 26.1) kJ/mol and the pre-exponential factors (5.86E-3, 6.95E-3, and 6.95E-3) were attained for cotton stalks, corn stalks, and rice straw, respectively. These activation energy values are considered low, which specify the ease of gasification of these three types of the agricultural wastes.

Internal mass and heat distribution within a combustor is a key factor of successful combustion process as it influences the contact between the reacting materials and helps reduce formation of undesired products such as dioxins via diminishing emerged hot or cold spots. Nevertheless in case of circulated fluidized bed combustor CFBC, it is difficult to keep a homogeneous heat and mass distribution due to the usage of combusting materials with variable and in some situations unpredictable compositions such as municipal and agricultural wastes. Thus this work investigates CFD Ansys – Fluent simulation as a tool to help the plant operator attain uniform heat and mass transfer via enabling the plant operator to adjust the operating conditions to fit well the used fuel. That is through: (a) visualizing the internal mass and heat distribution within a combustor, (b) manipulating the operating conditions of pressure, velocity, and bed particulates flow rate to determine the correct values considering the inevitable feature of the used fuels, (c) exploring operation deficits and sorting out the problems and (d) studying the feasibility of proposed modifications or changes. An illustrative case study is given as a methodology to demonstrate how likely reasons beyond combustor operation deficits can be defined and tackled. The case study is designed to exemplify the tool to achieve the objective of internal uniform heat and mass transfer within a combustor for given fuel composition and the operating conditions.

This paper presents a statistical technique to characterize the biodiesel production process from Jatropha seeds and predict the conversion efficiency of the oil into biodiesel. A multivariate regression model is proposed herein to simultaneously capture the joint effect of the variable operating conditions. It is a general technique and can be used with different production methods, but this paper uses experimental results of the in-situ heterogeneous extraction and transesterification process. The results imply the success of the introduced technique to assess how much the operating variables affect the conversion. Also, the joint effect of the time, catalyst dose, methanol to oil ratio, and hexane to oil ratio has been defined. Experimental measurements have been used to perform this analysis. A linear multiple regression model with coefficient of determination (R-2) of 0.999 has been developed whereby the four investigated operation variables are related with the conversion into biodiesel has been developed. Hence, utilizing the coefficients of the developed model have been used to rank their significance, which is the most important variable and to what extent. Accordingly the most important factors are the time and the hexane ratio.

The association of concentrated solar energy and biomass gasification has often been suggested as an interesting alternative to conventional autothermal processes where a significant portion of the biomass has to be used for heat generation to drive endothermic reactions. It is a clean process able to produce high quality synthesis gas with a higher output per unit of feedstock and that allows for the chemical storage of solar energy in the form of a readily transportable fuel, among other advantages. The present paper describes the latest advances in solar thermochemical reactors for gasification of carbonaceous feedstocks. This work is categorized in this paper into patents and research/journal papers. (C) 2013 Elsevier Ltd. All rights reserved.

This work is aimed at the development of a systematic procedure for energy conservation through the integrated design of trigeneration systems (combined cooling, heating, and power – “CCHP”) while incorporating solar energy as a renewable form of energy with low GHG emissions. The focus is on developing preliminary screening and targets that guide the conceptual design of a trigeneration system. Absorption refrigeration is used to utilize excess process heat and external energy in the form of fossil and solar energy. To account for the seasonal fluctuation in collected solar energy, the decision-making horizon is discretized into multiple periods. An extended transshipment representation is developed to embed design configurations. Next, a nonlinear programming formulation is developed. The solution of the optimization formulation determines the optimal levels of power, external heating, external cooling, heat integration, mix of fossil/solar energy forms to be supplied to the process, and the scheduling of the system operation.

This paper presents a new methodology for the energy integration of systems that require refrigeration. It considers the integration between process streams as well as that between the heat from process stream excess, solar energy, fossil fuels, and biofuels to run the stripper required by the absorption refrigeration (AR) needed. The proposed methodology consists of two stages: the first one identifies the energy targets, while the second one uses a new mathematical programming model to solve a multiobjective optimization mixed-integer linear programming (MILP) problem, allowing one to determine the minimum cost as well as the minimum greenhouse gas emissions (GHGE) to satisfy the utility requirements identified in the first stage. The proposed model considers the optimal selection of different types of solar collectors, and since the solar radiation depends on the season of the year, the model also accounts for the best combination of fossil and biofuels to complement the energy required for the AR The proposed methodology is very useful to identify the scenario required to implement the use of clean energies in the refrigeration process. Three problems are presented to show the applicability of the proposed methodology, which does not exhibit numerical complications; these results show that process integration helps to get a given reduction in the GHGE economically attractive involving the use of clean energies, besides identifying the required tax credit to get economic and environmentally efficient cooling systems. In addition, because of the availability of the solar radiation, the solar collectors must be integrated with different types of energy, depending on the season of the year.

This paper describes a preliminary in-depth analysis of the techno-economic criteria for solvent selection for the supercritical fluids Fischer–Tropsch synthesis (FTS). Both conventional media (i.e. gas phase FTS and liquid phase FTS) as well as non-conventional media (near-critical and supercritical phase FTS) were examined, with an emphasis on non-conventional media FTS for the design and commercialization purposes of a novel FTS reactor technology. A wide array of hydrocarbon solvents were reviewed, ranging from propane to decane, with numerous blends of two or more of the mentioned paraffins; several fuel cuts were studied as well, such as light and heavy naphtha and diesel. Also, the interaction of the solvents with in situ reaction mixture and products were studied to further insure single phase operation and process feasibility. A concurrent examination of the techno-economic analysis for solvent selection was carried out; this is of utmost importance since the economic incentives as well as the technical conquest (i.e. overcoming design limitations) are the basis for the novel approach to the reactors design and commercialization of this novel technology.

Absorption refrigeration is gaining increasing attention in industrial facilities to use process heat for partially or completely driving a cooling cycle. This paper introduces a systematic approach to the design of absorption refrigeration systems for industrial processes. Three sources of energy are considered to drive absorption refrigerators: excess process heat, solar energy, and fossil fuels. To handle the dynamic nature of solar energy, hot water tanks are used for energy storage and dispatch. Thermal pinch analysis is performed to determine the amount of available excess heat and the required refrigeration duty. Next, a multiperiod optimization formulation is developed for the entire system. The procedure determines the optimal mix of energy forms (solar versus fossil) and the dynamic operation of the system. Three case studies are solved to demonstrate the effectiveness and applicability of the devised procedure.

This paper comprises of a preliminary in-depth analysis of the techno-economic criteria for the Fischer-Tropsch synthesis (FTS) solvent selection. Both conventional media (i.e. gas phase FTS and liquid phase FTS) as well as non-conventional media (near-critical and supercritical phase FTS) were examined, with an emphasis on non-conventional media FTS for the design and commercialization of a novel FTS reactor technology. Supercritical and near critical fluids (SCFs) are attractive for several reasons, highlighted by their ability to overcome some of the major limitations of current commercial technologies (e.g. transport limitations in the slurry reactor, and thermal limitations in multi-tubular reactors). Due to single phase operation of SCFs, these solvents are unique media for chemical reactions as they operate with densities that are sufficient to afford substantial dissolution power, while also providing diffusivities that are higher than normal liquids and viscosities that are lower than their liquid counterparts. High temperature Fischer-Tropsch (HTFT) was the center of examinations, but LTFT was considered as well. A wide array of hydrocarbon solvents was reviewed, ranging from propane to decane, with numerous blends of two or more of the mentioned paraffins. Several fuel cuts were studied as well, such as light and heavy naphtha and diesel. Understanding the transport and thermodynamic behavior as well as economic benefit of these said solvents is essential to the success of an advanced FTS reactor model. Also, the interaction of the solvents with in-situ reaction mixture and products further insures single-phase operation and feasibility.

The escalating energy prices and the increasing environmental impact posed by the industrial usage of energy have spurred industry to adopt various approaches to conserving energy and mitigating negative environmental impact. This work is aimed at the development of a systematic procedure for energy conservation and incorporation of two renewable sources of energy into industrial usage: biofuels and solar energy. First, heat integration is carried out to minimize industrial heating and cooling utilities. Next, different types of biomass are processed to produce thermal energy and biofuels (such as biodiesel) to be used in supplying an appropriate portion of the needed utilities. Additionally, the solar system is included as a candidate source of energy. To optimize the cost and to overcome the dynamic fluctuation of the solar energy and biofuel production systems, fossil fuel is used to supplement the renewable forms of energy. An optimization approach is adopted to determine the optimal mix of energy forms (fossil, biofuels, and solar) to be supplied to the process, the system specifications, and the scheduling of the system operation. A case study is solved to demonstrate the effectiveness and applicability of the devised procedure.

Widespread industrial utilization of solar energy is an important goal that requires overcoming several technical challenges. One of the key hurdles is the need to address the temporal fluctuations in incident solar power (e.g., on an hourly basis or seasonally) which lead to variations in the outlet power. This work is aimed at the development of a systematic design procedure providing a stable power outlet while using solar systems. First, the dynamic performance of solar collectors is parametrically modeled. Next, an optimization formulation is developed as the basis for the design procedure which accounts for the integration of solar and fossil energy sources in a power system. The procedure determines the optimal mix of energy forms (solar vs. fossil) to be supplied to the process, the system specifications, and the dynamic operation of the system. The developed procedure includes gathering and generation of relevant solar and climatic data, modeling of the various components of the solar, fossil, and power generation systems, and optimization of several aspects of the hybrid system. A case study is solved to demonstrate the effectiveness and applicability of the devised procedure.