Category Progress in Sustainable Energy Technologies: Generating Renewable Energy

Concluding Remarks

A lot of research has been done to improve, upgrade and advance the thermody­namic efficiencies of the various technologies used in dual purpose power and water production plants. This study has contributed to the perpetual goal of reducing the per unit cost of power and water produced from dual purpose power and water pro­duction plants by investigating ways, methods, and mechanisms of improving the operating efficiency of installed capacities. Although major upgrades would require at least retrofits or plant redesign, the major issues tackled in this paper are more to do with improving operational practice by observing and using data and informa­tion from simulations...

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Results and Discussion

Production—Demand Ratios

Numerical simulation was used to determine the relationship between total water or power demand and total water or power produced. To minimize the per unit cost of electricity production and water desalination, two important selections must be ac­counted for at a certain time interval: namely, electricity and water demands. In or­der to satisfy electricity generation and freshwater production demands, the optimal

Fig. 46.3 Arena simulation model for experimenting with various electricity production operation strategies in the case study plant

unit configuration and operating conditions are solved as implied in the mathemati­cal model...

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Simulation Experiments

In the power and water production simulation experiments, a quasi-experimental design was used [10]. This approach focuses on comparing the results of the cur­rent situation (control experiment) with “what-if ’ scenarios. In the case study plant, power generation is driven by gas turbines and thermal energy from their exhaust is used to generate low-to-medium pressure steam through the waste heat recovery boilers. In this set-up, steam is routed directly to the brine heater of the distillation plant. Auxiliary boilers are usually used for higher yields. Although it is flexible (within the plant design parameters), the power to water ratio produced depends on operational practice. However, fuel savings increase with decrease in the power to water ratio...

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Case Study

A case study of an existing DPPW production plant in Qatar was used in the analy­sis. The basic configuration of the case study plant is shown in Fig. 46.1. The power production side consists of a compressor (CP), combustion chamber (CC) and a gas turbine (GT), while the water production side is based on the multistage flash (MSF) distillation process.

The compressor compresses incoming air to a high pressure which is then mixed with natural gas and burnt in the combustion chamber to produce high pressure and high velocity gas which in turn is used as mechanical energy to drive the compres­sor and the electrical generator...

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Simulation Modeling

Simulation modeling is a common method for analyzing complex systems. It cre­ates a simplified representation of a system under study. Then one can start experi­menting with the system, keeping in mind prescribed set of goals, such as improved system design, cost-benefit analysis, and sensitivity to design parameters. Experi­mentation consists of generating system scenarios and observing system behavior over time [8].

Fig. 46.1 Simplified configuration of the case study plant proposed by Ferreira et. al [3]

The working simulation tool for the models in this study is ARENA. ARENA is a simulation environment consisting of module templates, built around SIMAN language...

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Methodology

Modeling is the creation of a simplified representation of a complex system with the goal of providing predictions of the system’s performance measures. Plant models were designed to capture materials flow.

Numerical Simulation

Numerical simulation modeling for water balance analysis was based on the follow­ing equation, after [7]:

SCk = SCk-1 + Y, h DK + WBk – WK, where K = 1, 2, …. K (46.1)

where:

SCk Total contents of reservoir at period k, m3—similarly this is denoted as total water consumption (m3/month) giving us the annual total RC Reservoir capacity, m3—this is found by flow rate (m3/hr) * 24 h/day * 30 days/month

DiK Output of distillation unit i during interval k—for the case study we have

distillate flow rate + flow rate of number of high purity distillates Wbk Brackish...

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Simulation, Modeling and Analysis of Water/ Power Ratios for a Dual Purpose Water and Power Production Plant

Luma M. Diab and Farayi Musharavati

Abstract In dual purpose power and water (DPPW) production plants two chal­lenges are often encountered; (a) maintaining operations that meet a desired water production/demand ratio or power production/demand ratio, and (b) meeting the desired water to power ratio. Although these problems are usually implied in the implemented plant design and technology, operational issues play an important role in fine tuning operations towards optimal performance. In addition, operational practices have a bearing on energy consumption and operating efficiencies. In this study, a simulation based approach is used to provide data for handling the fine tun­ing of operations towards desired targets...

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Concluding Remarks

In this study, the importance of power/water cogeneration plants as alternative and cost effective means of providing both water and power simultaneously has been discussed. It is generally believed that power/water cogeneration plants have the potential to drastically reduce the unit costs of freshwater and power. Consequently, a number of thermodynamic and thermo-economic investigations on power/water cogeneration plants have been discussed by many authors. While progress has been made in terms of thermodynamic design and efficiencies, the contribution of this study was to explore, investigate analyze and identify other substantial benefits that can be accrued by critically examining the operating performances and practices in installed capacity of power/water cogeneration plants...

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