allows the cost to be expressed as a function of system size. The three network sizes considered were fields of 512, 4608 and 41472 collectors. A computer code was written which designs the pipe network from the basic inputs previously discussed. The effective cost of each energy transport network is the sum of the direct construction cost plus the estimated value of the thermal power lost due to heat loss and pumping power requirements. The losses from the transport system reduce the heat available to the power plant for electrical conversion and consume some of the gross power produced. In the analysis both of these losses were costed at the rate of 325$/kWt. With this assumption it is possible to vary pipe diameter and insulation thickness to obtain the piping configuration leading to minimum total system cost. The heat leak during energy transport causes an increase only in the collector and transport subsystems while the electric pumping power causes an increase in the total plant cost. Since the collector and transport subsystems made up over 80% of the total system cost, the overall cost of 325$/kWt can be used for both the thermal heat leaks as well as electrical pumping power with little error in selection of the optimum point. The direct construction costs for the minimum cost combination of pipe sizes and insulation thickness are presented in Figure 12. This figure illustrates the transport and system direct cost versus delivered thermal power. The chemical transport subsystem is the least expensive at $30/kWt. The water and steam transport subsystems are nearly the same cost at approximately $40/kWt (400 MWt). The NaK and helium systems appear to have unacceptably high costs (150 to 175$/kWt). It is unlikely that improvements can be made in the costs of the liquid metal transport network. Due to safety hazards not considered, the NaK approach would have to show a significant economic advantage before being considered. Some improvement is perhaps possible with helium transport, depending upon the
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