FUSION POWER ECONOMY OF SCALE

In the next 50 yr, the world will need to develop hundreds of gigawatt s of non-fossil-fuel energy sources for production of electricity and fuels. Nuclear fusion can probably pro vide much of the required energ y economically, if large single-unit power plants are acceptable. Larg e power plants are more common than most people realize: There are alr eady many multiple-unit power plants producing 2 to 5 GW(electric) at a single site. The cost of electricity (COE) from fusion energy is pre dicted to scale as COE almost-equal-to COE0(P/P0)-n, where P is the el ectrical power, the subscript zero denotes reference values, and the e xponent n almost-equal-to 0. 36 to 0. 7 in various designs. The validi ty ranges of these scalings are limited and need to be extended by fut ure work. The fusion power economy of scale derives from four interrel ated effects: improved operations and maintenance costs, scaling of eq uipment unit costs; a geometric effect that increases the mass power d ensity; and reduction of the recirculating power fraction. Increased p lasma size also relaxes the required confinement parameters: For the s ame neutron wall loading, larger tokamaks can use lower magnetic field s. Fossil-fuel power plants have a weaker economy of scale than fusion because the fuel costs constitute much of their COE. Solar and wind p ower plants consist of many small units, so they have little economy o f scale. Fission power plants have a strong economy of scale but are u nable to exploit it because the maximum unit size is limited by safety concerns. Large, steady-state fusion reactors generating 3 to 6 GW(el ectric) may be able to produce electricity for 4 to 5 cent/k W.h, whic h would be competitive with other future energy sources.