Feedwater Preheating Research Articles

Enabling CCS via Low-temperature Geothermal Energy Integration for Fossil-fired Power Generation

Among the key barriers to commercial scale deployment is the cost associated with CO2 capture. This is particularly true for existing large, fossil-fired assets that account for a large fraction of the electricity generation fleet in developed nations, including the U.S. Fitting conventional combustion technologies with CO2 capture systems can carry an energy penalty of thirty percent or more, resulting in an increased price of power to the grid, as well as an overall decrease in net plant output. Taken together with the positive growth in demand for electricity, this implies a need for accelerated capital build-out in the power generation markets to accommodate both demand growth and decreased output at retrofitted plants. In this paper, the authors present the results of a study to assess the potential to use geothermal energy to provide boiler feedwater preheating, capturing efficiency improvements designed to offset the losses associated with CO2 capture. Based on NETL benchmark cases and subsequent analysis of the application using site-specific data from the North Valmy power plant, several cases for CO2 capture were evaluated. These included geothermally assisted MEA capture, CO2BOLs capture, and stand-alone hybrid power generation, compared with a baseline, no-geothermal case. Based on Case 10, and assuming 2.7 MMlb/h of geothermally sourced 150°C water, the parasitic power load associated with MEA capture could be offset by roughly seven percent, resulting in a small (∼1 percent) overall loss to net power generation, but at levelized costs of electricity similar to the no-geothermal CCS case. For the CO2BOLs case, the availability of 150 ˚C geothermal fluid could allow the facility to not only offset the net power decrease associated with CO2BOLs capture alone, but could increase nameplate capacity by two percent. The geothermally coupled CO2BOLs case also decreases LCOE by 0.75 ¢/kWh relative to the non-hybrid CO2BOLs case, with the improved performance over the MEA case driven by the lower regeneration temperature and associated duty for CO2BOLs relative to MEA.

Application of Solar Energy Heating System in Some Oil Industry Units and its Economy

Energy is one of the building blocks of modern society. Once an exporter of oil and gas, Egypt is now struggling to meet its own energy needs. In oil industry there is an energy problem due to fuel and electricity consumption and refinery losses in a way that reduces the net profit of the industry. There are also environmental problems due to carbon dioxide emissions which is a major source of the global warming problem. As Egypt is blessed with geographic location in the Sun Belt area with 325 days of sun in a year, solar energy can be used as a source of energy that reduces fuel consumption and CO2 emissions. The current study presents solar energy heating system that can be used for heating applications in some oil industry units. The study has been divided in two parts, the first one concerned with choosing the most appropriate solar system that can be used in such applications. Four different mathematical models for prediction of optical efficiency and thermal losses for the chosen system have been analyzed and then computerized using excel sheet program. Numerical comparison and also practical validation of the selected model have been done. For that paper under title of “Evaluation of Mathematical Models for Solar Thermal System” was published in October, 2016, American Journal of Energy Science. Visual basic program is then done for the validated model for good and friendly user interface. For the second part of the study, this paper concerned with performing an economic evaluation for providing feasibility and reliability conception about using the proposed system in some oil industry applications in number of Egyptian companies as preheating of crude oil for desalting in oil production (Khalda petroleum company), preheating of viscous oil for transportation enhancing and preheating of boiler feed water (Cairo oil refining company). The results shows that payback period for crude preheating before desalting is 20 years and for fuel oil and boiler feed water preheating are 7 years.

Multi-objective superstructure-free synthesis and optimization of thermal power plants

The merits of superstructure-free synthesis are demonstrated for bi-objective design of thermal power plants. The design of thermal power plants is complex and thus best solved by optimization. Common optimization methods require specification of a superstructure which becomes a tedious and error-prone task for complex systems. Superstructure specification is avoided by the presented superstructure-free approach, which is shown to successfully solve the design task yielding a high-quality Pareto front of promising structural alternatives. The economic objective function avoids introducing infinite numbers of units (e.g., turbine, reheater and feedwater preheater) as favored by pure thermodynamic optimization. The number of feasible solutions found per number of mutation tries is still high even after many generations but declines after introducing highly-nonlinear cost functions leading to challenging MINLP problems. The identified Pareto-optimal solutions tend to employ more units than found in modern power plants indicating the need for cost functions to reflect current industrial practice. In summary, the multi-objective superstructure-free synthesis framework is a robust approach for very complex problems in the synthesis of thermal power plants.

Simultaneous synthesis of utility system and heat exchanger network incorporating steam condensate and boiler feedwater

A heat exchanger network (HEN) is an important part in processing plants used to recover heat from process streams. A utility system supplies heating and cooling utilities and introduces additional hot and cold streams for the processes. The HEN and utility system (e.g., Rankine cycle-based cogeneration system) are closely interconnected primarily through steam, steam condensate leaving the turbines, and process surplus heat. The recovery of the sensible heat from the steam condensate and process surplus heat through an integration technique may contribute significantly to the reduction of the heating and cooling utility consumption in the heat exchanger network as well as in the primary energy consumption in the utility system. In this paper, a systematic methodology for the simultaneous synthesis and design of a utility system and HEN is proposed. The heat recovery from the steam condensate and boiler feedwater preheating are integrated into the HEN synthesis together with the design optimization of a Rankine cycle-based utility system. In addition to the simultaneous design of the utility and heat-recovery systems, the optimization variables include the steam condensate target temperature, the steam level for process heating, the energy demand for the utility system, the returning temperature of the steam condensate, and the final temperature of the boiler feed water. The total site HEN is composed of several interlinked sub-HENs. A model for the new hot utility-process cold stream HEN is formulated together with the hot -cold process streams of the HEN. The linking constraints between sub-HENs and the utility system are formulated. Several case studies are elaborated to demonstrate the effectiveness and applicability of the proposed methodology. Compared with the former design methods without integrating steam condensate sensible heat and boiler feedwater preheating, meaningful economic benefits can be achieved by applying the proposed framework.

Thermodynamic and economic evaluation of a solar aided sugarcane bagasse cogeneration power plant

This work evaluated the integration of Concentrated Solar Power (CSP) with a sugarcane bagasse cogeneration plant located in Campo Grande (Brazil). The plant is equipped with two 170 t/h capacity steam generators that provide steam at 67 bar/525 °C. Superheated steam is expanded in a backpressure and in a condensing-extraction turbine. The evaluated hybridization layouts were: (layout 1) solar feedwater pre-heating; (layout 2) saturated steam generation with solar energy and post superheating in biomass steam generators and (layout 3) superheated steam generation in parallel with biomass boilers. Linear Fresnel and parabolic trough were implemented in layouts 1 and 2, while solar tower in layout 3. The exportation of electricity to the grid was increased between 1.3% (layout 1/linear Fresnel) and 19.8% (layout 3) in comparison with base case. The levelized cost of additional electricity was accounted between 220 US$/MWh (layout 3) and 628 US$/MWh (layout 1/linear Fresnel). The key factor related to layout 3 was the improvement of solar field capacity factor due to the solar-only operation of this approach. These aspects demonstrate that the combination of solar and bagasse resources might be the key to turn CSP economically feasible in Brazil.

Optimization of Solar Integration in Biomass Fuelled Steam Plants

This paper is focused on solar-biomass integration and presents a thermodynamic analysis of solar power utilization replacing the steam bleeds of a regenerative Hirn cycle plant, biomass fuelled, in feedwater pre heating process. In solar-biomass integrated configuration an energy conversion efficiency of solar energy has been evaluated in order to compare the use of solar energy in solo and hybrid configurations. Such efficiency has been adopted as optimization parameter for the best hybrid plant configuration, varying steam pressure and regeneration parameters.

Performance analyses of a hybrid geothermal–fossil power generation system using low-enthalpy geothermal resources

Low-enthalpy geothermal heat can be efficiently utilized for feedwater preheating in coal-fired power plants by replacing some of the high-grade steam that can then be used to generate more power. This study analyzes a hybrid geothermal–fossil power generation system including a supercritical 1000MW power unit and a geothermal feedwater preheating system. This study models for parallel and serial geothermal preheating schemes and analyzes the thermodynamic performance of the hybrid geothermal–fossil power generation system for various geothermal resource temperatures. The models are used to analyze the effects of the temperature matching between the geothermal water and the feedwater, the heat losses and pumping power during the geothermal water transport and the resource distance and temperature on the power increase to improve the power generation. The serial geothermal preheating (SGP) scheme generally generates more additional power than the parallel geothermal preheating (PGP) scheme for geothermal resource temperatures of 100–130°C, but the SGP scheme generates slightly less additional power than the PGP scheme when the feedwater is preheated to as high a temperature as possible before entering the deaerator for geothermal resource temperatures higher than 140°C. The additional power decreases as the geothermal source distance increases since the pipeline pumping power increases and the geothermal water temperature decreases due to heat losses. More than 50% of the power decrease is due to geothermal water temperature decreases along the pipeline since less higher pressure extracted steam is replaced by the geothermal water. For geothermal resource temperatures of 140–160°C, the additional power generated by the hybrid geothermal–coal power generation system is about 90% (at a geothermal source distance of 0km) or 39–49% (at a distance of 20km) greater than the power generated by an optimized organic Rankine cycle system using isopentane (R601a), the hybrid power generation system has little benefit over the ORC system when the distance increases to 40km. However, the additional power generated by the hybrid power generation system is less than the power generated by the ORC system at distances over 20km for geothermal resource temperatures of 100°C.

Superstructure-free synthesis and optimization of thermal power plants

The optimal synthesis and design of thermal power plants is best addressed using mathematical optimization techniques. However, conventional optimization methods require the user to manually define a priori the potential solution space through the modeling of a superstructure, which is a time-consuming, complex, and error-prone task. More importantly, the final superstructure model can not guarantee to contain all good alternatives (in particular, the optimal solution), while it might consider a huge number of meaningless or even infeasible alternatives. To circumvent the use of superstructures, recently, a generic superstructure-free optimization approach has been proposed by the authors to synthesize distributed energy supply systems. The approach employs hybrid optimization integrating evolutionary and deterministic optimization to enable simultaneous alternatives generation and optimization. In this paper, the approach is extended by a new mutation rule to enable the synthesis of thermal power plants. The features of the extended superstructure-free approach are illustrated by a case study. The optimization is initialized with the simplest plant cycle consisting of one turbine, one pump, one steam generator, and one condenser. The superstructure-free approach automatically identifies highly efficient and complex structures featuring multi-stage reheating and feedwater preheating.

Impacts of solar multiples on the performance of integrated solar combined cycle systems with two direct steam generation fields

Integrated solar combined cycle (ISCC) systems coupled with direct steam generation (DSG) are more promising in terms of system efficiency and electricity cost than current solar-only power generation systems, as ISCC–DSG offers the advantages of higher net thermal efficiency and lower cost. However, the ISCC systems usually have to be operated at part-load conditions with low system efficiency when no or lower insolation than that at design point is available as most of state-of-the-art such systems have no thermal storage equipped. In order to improve system performance and prolong the system full-load operation hours, a proper solar field size represented as the solar multiple is a prime parameter to be determined during the design stage of the ISCC system. A too large solar multiple might cause the collected solar thermal energy to become partially useless without thermal storage and high investment cost, while a smaller one might worsen the part-load performance of the system.This paper presents the thermodynamic and economic analysis for an ISCC system with two pressure level DSG solar fields (ISCC–2DSG), aiming to study the impacts of solar multiples on system performance with or without consideration of thermal storage. In the ISCC–2DSG system, the solar thermal energy produced from two solar fields is only used to supply latent heat for low- and high-pressure water vaporization, respectively. Feedwater preheating and steam superheating are achieved in a HRSG. The annual thermodynamic performance of several such ISCC–2DSG systems, with different solar multiple values but with identical design parameters in the power subsystem, is characterized. Based on these features, the LEC for each system is calculated and compared. An optimum solar field size (solar multiple), which gives the minimum LEC, for the ISCC–2DSG system can be finally obtained.

Solar repowering of PCC-retrofitted power plants; solar thermal plant dynamic modelling and control strategies

Solar repowering of high pressure side feed water preheaters of post combustion carbon capture (PCC) retrofitted power plants offers a promising capability to offset the power plant output penalty due to capture plant reboiler duty. In this work, a model based approach is used to investigate the technical, operational and control aspects of the solar thermal installation of the super structure (power plant+PCC+solar thermal plant). The base case is a 660MWe PCC-retrofitted power plant operating at 100% capacity and 90% capture rate in Australia. This is repowered by a solar thermal plant consisting of (a) a parabolic trough solar collector field with 806,520m2 aperture area, (b) a thermal storage system with 8 full load hours of thermal storage and (c) an auxiliary gas heating unit, ensuring the solar thermal plant provides the high pressure side feed water preheating duty at all times without requirement to withdraw any steam from the power plant turbine circuit. A total of 230MWth is provided from the solar thermal plant installation, being 100% supply for high pressure and intermediate feed water preheaters duty plus a surplus of 30% for maintaining the deaerator operation. A key feature here is trying to eliminate the frequent changes to the steam flow rate in the turbine circuit for solar feed water preheating and thus promoting ease of retrofit of repowering technology to PCC-retrofitted power plants. Details of the component sizing and modelling of solar thermal installation are provided and control and operating schemes are identified and analysed. A comprehensive dynamic model in TRNSYS dynamic modelling software is developed and used to analyse the solar thermal plant dynamic responses to external disturbances including climatic changes (Typical Meteorological data for Sydney is used). The analysis limitations and capabilities are highlighted. The model performance for month December is assessed showing its full capability to track the changes from power plant duty requirement and meteorological data within the time lapse of 0.01s.

Improving energy efficiency of existing recovery boilers

Due to the increased global energy demand, increased electricity price, and incentives for renewable energy, it is in many cases profitable to maximize electricity output both from power boilers and from recovery boilers. Another motive for maximizing electricity output from recovery boilers is to decrease fuel input to power boilers. In cases where the saved fuel is fossil fuel, the carbon footprint of the mill can be decreased as well. In recent years, many different electricity efficiency increasing features have been installed on new and existing recovery boilers. In this paper, these recovery boiler-related, so-called high power features are applied to existing recovery boilers. The goal is to show how different kinds of mills with existing recovery boilers benefit from high power features. Some of these features can have certain limitations due to constraints set by the existing boilers, and these limiting factors are also discussed. In this study, electricity generation of two example cases are calculated with the following high power features: high black liquor dry solids, air preheating, fully pressurized feedwater tank, feedwater preheating, heat recovery from vent gases, heat recovery from flue gases, and high main steam parameters.

Repowering of existing AL-Hartha gas-fuelled conventional steam power plant with molten salt cavity tubular solar central receiver

This paper introduces a new method to repower the existing equipment of the AL-Hartha steam plant located in Basra, Iraq, using a molten salt cavity tubular solar central receiver (SCR). Cycle Tempo is used to simulate the existing natural gas-fuelled conventional steam power cycle with consideration of the heat and pressure losses. The heliostat field and the central receiver subsystems are coded using MATLAB. The model couples the heat balance with the temperature computation of the receiver walls for calculation and analysis of the thermal losses. The proposed modified codes are capable of calculating heat losses, evaluating the integrated power plant and satisfying a wide range of SCRs. The results are verified against plant data and previous works in the literature and good agreement is obtained. The results show the potential of using a molten salt cavity tubular SCR for low-range temperature feedwater preheating, as well as the optimum scheme for the integration of the existing plant with an SCR. It is observed that the maximum improvement for the existing AL-Hartha steam plant and the integrated molten salt cavity tubular SCR is obtained by substituting the bleed steam in all the high-pressure feedwater heaters. For this scheme, the obtained receiver energy efficiency reaches up to 94.1 % and the maximum reduction in instantaneous gas fuel consumption is about 10.1 % with a solar-electricity improvement of about 21.6 % over the design case.

Parametric optimization of supercritical coal-fired power plants by MINLP and differential evolution

The design trade-offs between thermodynamics and economics of energy conversion systems can be more effective by combining a superstructure and mixed-integer non-linear programming (MINLP) techniques. The front of decision space showing the optimal sets of economic behavior and system efficiency with different corresponding optimal system structures and process variables can provide additional and useful information on cost-effective design of thermal systems. In this paper, this idea was successfully applied to supercritical coal-fired power plants to investigate the economically-optimal designs at each efficiency level. The superstructure involving up to ten feedwater preheaters, up to two reheatings and a secondary turbine with steam extractions (ET) was built. An improved differential evolution algorithm was used to simultaneously solve the parametric and structural optimization problem. The differences among the fronts of various types of plants, the front changes with plant efficiency and the effects of introducing an ET were discussed in detail. For a single reheating unit, a decrease of 2% in cost of electricity can be achieved. The optimal pressure ratios of reheatings are 0.15–0.25 (for single reheating), 0.2–0.3 and 0.15–0.3 (for double reheatings).

System Integration and Flowsheet Optimization of 1000 MW Coal-fired Supercritical Power Generation Units

For traditional power generation process, energy losses are often caused by heat-and-mass transfer between the boiler and turbine subsystems, especially the heat transfer process with fairly high temperature difference in boiler. Generally, such energy losses are often unavoidable, if heat-and-mass transfer processes occur only in an independent way within certain subsystem or equipment but not in a cascade-integrated way. In this paper, new integration approach was proposed in order to reasonably utilize the heat at different temperature levels from the overall system perspective. Compared with isolated designs of the boiler and turbine subsystems, this approach comprehensively considers the match of heat transfer processes in air preheater and feedwater regeneration subsystem, and takes the principle of feedwater availability in the feedwater preheating process into account. The heat utilization process is reconstructed among the streams of flue gas, air, steam, feedwater and condensate water in a more coupling way. As a consequence, the thermodynamic irreversibility within air-preheating process and feedwater-regenerating system is sharply reduced. The heat-transfer characteristics and energy-saving effect of the integrated system was quantitatively analyzed. The results show that the power output of the novel integrated system is 21.74 MW higher than that of the conventional system. Moreover, the cost of electricity (COE) and the coal consumption rate can be decreased by 1.2% and 5.09g/kWh, respectively. This paper provides useful information for the energy-saving effects and design optimization of heat transfer process in thermal power generation.

Total Site Heat Integration incorporating the water sensible heat

Analysis of steam and water losses in the Total Site (TS) utility system is critical in process industry. Makeup water plays an important role in maintaining the water balance in the steam and condensate systems. Total Site Heat Integration (TSHI) offers a solution to increase energy savings as well as energy efficiency and consequently, to promote sustainability. However, so far most studies on TSHI have not considered the water sensible heat in TS targeting; e.g. for Boiler Feed Water (BFW) preheating and steam superheating during steam generation. In this work, an extended methodology is developed to target the minimum utility requirements in a steam system that considers the water sensible heat. The Extended Total Site Problem Table Algorithm (TS-PTA) is proposed as a systematic numerical tool to consider the sensible heat while targeting the Total Site utility requirements. The Extended Site Composite Curves (ESCC) are developed as a visualisation tool for the Extended TS-PTA. Illustrative and industrial case studies are used to verify the methodology. The results demonstrate the significance of considering the sensible heat of water on the TS utility targets.

Exergoeconomic Evaluation of a Modern Ultra-Supercritical Power Plant

In this paper, the exergoeconomic analysis was conducted to an existing ultra-supercritical coal-fired power plant in China to understand the cost-formation process, to evaluate the economic performance of each component and to find possible solutions for more cost-effective designs. The total revenue requirement (TRR) and the specific exergy costing (SPECO) methods were applied for economic analysis and exergy costing, respectively. Quantitative balances of exergy and exergetic costs as well as necessary auxiliary equations for both individual component and the overall system were established. The results show that the exergoeconomic factors of the furnace and heat exchangers at low temperature levels, including air preheater and low-pressure feedwater preheaters, are rather small; while those of other components are relatively large. Moving more heat absorption into furnace to use the effective radiation heat transfer, increasing the air preheating temperature and adding more low pressure feedwater preheaters can be promising solutions for future design.

Thermodynamic analysis of feed water pre-heaters in multiple effect distillation systems

The purpose of this article is to investigate the influence of using feed water pre-heaters in multiple effect distillation systems with thermal vapor compression (MED-TVC). By using these heat exchangers, temperature difference between feed water and steam in each effect would be constant. In this way, the required energy for preheating the feed water will decrease and the feed water evaporates as soon as it enters the effect. In this article, it is shown preheating the feed water has a great influence on decreasing the energy consumption of MED-TVC distillation systems. The influence of different configurations of feed water preheating on energy consumption of MED-TVC process is investigated as well. Results show that the energy consumption will be minimum if the pre-heaters increase the feed water temperature in such a way that their temperature difference is equal to that of effects.

Advanced Thermodynamic Analysis and Evaluation of a Supercritical Power Plant

A conventional exergy analysis can highlight the main components having high thermodynamic inefficiencies, but cannot consider the interactions among components or the true potential for the improvement of each component. By splitting the exergy destruction into endogenous/exogenous and avoidable/unavoidable parts, the advanced exergy analysis is capable of providing additional information to conventional exergy analysis for improving the design and operation of energy conversion systems. This paper presents the application of both a conventional and an advanced exergy analysis to a supercritical coal-fired power plant. The results show that the ratio of exogenous exergy destruction differs quite a lot from component to component. In general, almost 90% of the total exergy destruction within turbines comes from their endogenous parts, while that of feedwater preheaters contributes more or less 70% to their total exergy destruction. Moreover, the boiler subsystem is proven to have a large amount of exergy destruction caused by the irreversibilities within the remaining components of the overall system. It is also found that the boiler subsystem still has the largest avoidable exergy destruction; however, the enhancement efforts should focus not only on its inherent irreversibilities but also on the inefficiencies within the remaining components. A large part of the avoidable exergy destruction within feedwater preheaters is exogenous; while that of the remaining components is mostly endogenous indicating that the improvements mainly depend on advances in design and operation of the component itself.

Transient and dynamic performance of solar driven multiple effect distillation

Transient and dynamic performance of solar driven multiple-effect distillation (MED) system without thermal energy storage (storing of water rather than energy) are studied and presented. A typical 25,900 m3/day operational multiple effect distillation with thermal vapor compression (MED-TVC) is used for the transient and dynamic simulation. Two scenarios are studied for the transient performance to; i) pump the feed water flow and ii) spray feed water onto the horizontal tubes bundle in each effect. The first scenario uses a constant flow rate of feed water along most of operating hours. The second scenario assumes a sinusoidal trend for the feed water flow rate during the operating hours (simulating direct PV electrical generation with no electric energy storage). The dynamic performance is due to a disturbance of a rectangular pulse forcing function on the seawater flow for duration of 50 s, which increased 25% for 5 s. The response of that disturbance on the behavior of the MED process parameters, such as the distributions of the temperatures, mass flow rates, and physical properties is presented. The physical model of each effect is divided into seven compartments including brine pool, vapor space, tubes bundles and feed water pre-heater. Transient and dynamic equations for each compartment and other system components are formulated mathematically. Mass, salt and energy balance equations are solved dynamically taking into consideration the inter-related effect of each compartment onto the other. The transient resultant flow rates of each stream (vapor production, TVC, brine disposal, etc) are presented in details and compared to conventional steady operation. When using the feed water scenario of sinusoidal feed to operate the solar MED unit, the results indicates that the salt precipitation can increase above the designed value. The results show also that the dynamic behavior of feeding water coming into the effects is flows the same trend the disturbance that took place in the main source of seawater supply. The flow rates of feed water are affected by the applied disturbance and increases gradually from normal operation to a peak value then decreases again to the normal operation state value. The system undergoes this disturbance shows to be still stable in operation as the change in its behavior is just bounded around the disturbance time, and regain, in a very short time, to the initial (normal operation) value of starting point. Key words: Solar energy, desalination, dynamic behavior, MED-TVC.

Transient and dynamic performance of solar driven multiple effect distillation

Transient and dynamic performance of solar driven multiple-effect distillation (MED) system without thermal energy storage (storing of water rather than energy) are studied and presented. A typical 25,900 m3/day operational multiple effect distillation with thermal vapor compression (MED-TVC) is used for the transient and dynamic simulation. Two scenarios are studied for the transient performance to; i) pump the feed water flow and ii) spray feed water onto the horizontal tubes bundle in each effect. The first scenario uses a constant flow rate of feed water along most of operating hours. The second scenario assumes a sinusoidal trend for the feed water flow rate during the operating hours (simulating direct PV electrical generation with no electric energy storage). The dynamic performance is due to a disturbance of a rectangular pulse forcing function on the seawater flow for duration of 50 s, which increased 25% for 5 s. The response of that disturbance on the behavior of the MED process parameters, such as the distributions of the temperatures, mass flow rates, and physical properties is presented. The physical model of each effect is divided into seven compartments including brine pool, vapor space, tubes bundles and feed water pre-heater. Transient and dynamic equations for each compartment and other system components are formulated mathematically. Mass, salt and energy balance equations are solved dynamically taking into consideration the inter-related effect of each compartment onto the other. The transient resultant flow rates of each stream (vapor production, TVC, brine disposal, etc) are presented in details and compared to conventional steady operation. When using the feed water scenario of sinusoidal feed to operate the solar MED unit, the results indicates that the salt precipitation can increase above the designed value. The results show also that the dynamic behavior of feeding water coming into the effects is flows the same trend the disturbance that took place in the main source of seawater supply. The flow rates of feed water are affected by the applied disturbance and increases gradually from normal operation to a peak value then decreases again to the normal operation state value. The system undergoes this disturbance shows to be still stable in operation as the change in its behavior is just bounded around the disturbance time, and regain, in a very short time, to the initial (normal operation) value of starting point. Key words: Solar energy, desalination, dynamic behavior, MED-TVC.