Category Progress in Sustainable Energy Technologies: Generating Renewable Energy

Operation and Maintenance Costs

A comparison of the non-fuel variable operation and maintenance (O & M) costs distribution for one year operation of the water desalination side are shown in Fig. 45.7. The potential cost savings (i. e. actual—reference) are also shown in Fig. 45.7. Figure 45.7 does not include fixed operation and maintenance costs. The potential savings represent the potential improvements in operating efficiencies by

Fig. 45.7 Comparison and distribution of variable operation and maintenance costs for water desalination

Fig. 45.8 Comparison and distribution of variable operation and maintenance costs for power production

continuously positioning operational practice towards best practice. The total po­tential savings in variable costs for 1 year operation amounts to $ 1,002,291/year.

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Fuel Utilization

A comparison of the fuel utilization distribution in power generation for 1 year op­eration for the reference and actual plant data are shown in Fig. 45.5.

The potential fuel savings (i. e. reference—actual) is also shown in Fig. 45.5. This potential savings represent non-capital-intensive potential improvements in operating efficiencies by continuously positioning operational practice towards best practice. The represented potential savings can be gained through effective repair­ing of leaks (natural gas and compressed air); maintaining optimum combustion efficiency, appropriate maintenance practices and optimal strategies for utilizing key equipment, pipes and equipment insulation.

Fig. 45.6 Distribution and comparison of fuel utilization in water desalination for 1 year operation

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Results and Discussions Plant Operating Performance

Case study plant performances are summarized in Figs. 45.3 and 45.4. The energy generated ranges from 240,000 to 460,000 MWH. Water production varied between 3,000,000 and 4,800,000 m3 per month. The power to water ratio ranged between 51.6 and 151.3 kWh/m3.

Plant capabilities and availabilities are characteristics of the cogeneration power and water production plant. Plant availability statistics are usually a func­tion of maintenance planning and implemented strategies. In this study, the only aspect of capability discussed is the flexibility of the cogeneration power and water production plant in terms of possible power to water ratios and in terms of

Fig. 45.3 Variations of energy generated in the case study plant for a one year operation

Fig. 45...

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Data Collection

Design parameter data were collected from reference plant operation manuals for comparison with actual plant data in the case study. Actual performance of the case study were analyzed using operational data for 1 year operation period for maxi­mum continuous rating (MCR). MCR is defined as the maximum output that a plant is capable of producing continuously under normal conditions over a year. Under ideal conditions, the actual output could be higher than the MCR [15]. Data col­lected included; mass flow rates, pressures and temperatures of system components, gross power generated, net power generated, power consumed, desalinated water production, and seawater consumption.

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Plant Operating Efficiency

The operating efficiency of an organization can be measured in many ways. A num­ber of aspects can be considered in evaluating the operating efficiency. Common categories of operating efficiency that are related to operational practices include; fuel acquisition efficiency, plant operating efficiency and capital efficiency.

Fuel acquisition is a significant aspect in determining the marginal and vari­able costs of power/water cogeneration plants. Since fuel acquisition practices are fully under the control of utility management changes, fuel procurement practices affect plant operating efficiencies. Fuel is the largest component of variable pow­er production costs. The generating company uses natural gas as the primary fuel that drives the gas turbine cycle...

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Method of Analysis

Case Study

A case study of a power/water cogeneration plant was used to compare plant design characteristics with actual plant performance data. The gas turbine cycle used in the generating company is a constant flow cycle with a constant addition of heat energy. The Brayton power cycle is the ideal thermodynamic cycle that approximates the operation of a gas turbine cycle in the case study. Figure 45.1 depicts the open, or simple cycle, characteristic of a typical gas turbine installed in the case study plant. The gas cycle is composed of a compact set formed by a compressor, a combustion chamber and a gas turbine connected to an electric generator.

In Fig. 45.1, air is compressed from point 1 to point 2 via an axial flow com­pressor...

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Energy Consumption

In cogeneration power/water production using the multi-stage flash (MSF) desali­nation process, the MSF is energy intensive [13]. The value and the cost of the thermal energy supplied to the MSF process depends on the method of supplying this energy. Steam can be supplied directly from fuel operated auxiliary boilers (FOABs) or from waste heat recovery boilers (WHRBs) associated with gas turbine power generation. In the case study plant, both FOABs and WHRBs are used. The use of FOABs to produce relatively low-pressure and temperature steam to drive the MSF process is, thermodynamically, wasteful. The thermal energy supplied to operate an MSF unit is in the form of relatively low-pressure steam to the brine heater (heat input section)...

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Energy Conservation

In the public literature, energy conservation methods and techniques have been discussed by many authors including [11]. Energy use issues discussed in this pa­per include; energy in installed capacity, operations and general plant utility man­agement practices. Good plant management practices include: effective repairing of leaks (natural gas and compressed air); maintaining optimum combustion ef­ficiency, as well as maintenance of pipe and equipment insulation. Best operational practices include: retrofits and/or replacement of production or auxiliary equip­ment, upgrades of process-specific equipment such as; new boilers, heat exchang­ers, economizers, and process control instrumentation...

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