Plant design power costs

In a chemical plant the capital investment in process piping is in the range of 25-40% of the total plant investment, and the power consumption for pumping, which depends on the line size, is a substantial fraction of the total cost of utilities. Accordingly, economic optimization of pipe size is a necessary aspect of plant design. As the diameter of a line increases, its cost goes up but is accompanied by decreases in consumption of utilities and costs of pumps and drivers because of reduced friction. Somewhere there is an optimum balance between operating cost and annual capital cost. 

A number of new solar power plants are under construction. In 2007, First Solar signed a contract to produce 685 mW of solar collectors over 5 years for 1.28 billion, or at a unit cost of 1.87/W. This might correspond to a 3/W installed cost. Southern California Edison is erecting a 500 mW plant designed by Solel Solar Systems of Beit Shemesh, Israel. It is scheduled to start up in 2009. 

It can be easily seen that the equipment size, pressure drop, and hence cost have a direct bearing upon the air compressor power. It is important to obtain the correct optimization between equipment costs and power consumption. The values used in the example are for illustration purposes. An actual plant design would vary based upon the cost vs. power analysis. This is covered in more detail in Section 3.2.3. 

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