vary with the fluid chosen due to the widely varying heat transfer characteristics and the different tubing materials and wall thickness required. The cavity receiver approach as suggested in Section 2.1.2 is considered an appropriate design. 2.2.2 Energy Transport A solar thermal power plant with a field of collectors which locally heat some transport fluid requires a pipe network system for eventual delivery of energy to the power generation equipment. The pipe network will transport cool fluid from the feedwater heaters of the central power station and distribute it to all of the dish collectors. The heated fluid then transports energy to the power plant for electrical conversion. Since the transport network is only one component of the solar power plant, its design and cost must be compatible with the rest of the system. Nevertheless, useful information can be generated by isolating a proposed fluid-energy transport system from all other components of the power plant and estimating its technical and economic performance. In this section five types of candidate energy transport fluids and their associated transport systems are considered. The installed cost of each subsystem has been calculated, the primary factor for comparison being installed cost per delivered thermal kilowatt ($/kWt). Heat exchanger equipment at the collector and at the Rankine plant are included elsewhere, and fluid pumps and other equipment perpherial to the transport subsystem are not considered in this economic analysis as these components add little to the total cost. The transport and system costs include expenses for pipes, insulation (when required), fluid to fill the pipes, pipe supports and installation labor costs. Correction is also made for pumping power requirements (expressed in kWt) during transport and heat loss through insulation when appropriate. The five systems considered are listed in Table 2. The temperature level considered most appropriate for each heat transfer fluid is specified in this table.
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