Solar thermal propulsion systems in space will require very high temperatures to generate necessary levels of thrust by the direct solar heating and resulting expansion and expulsion of the propellant material. The generation of such temperatures, in the range 1400-2200 °C, will in turn require very high levels of solar flux concentration. In practice, to […]

In the lunar environment, solar energy is almost half again as intense as typical terrestrial levels (1350 W/m2 versus about 900 W/m2) and nearly constant during the 2-week-long “lunar day.” Of course, accommodation of the lunar night will preclude long-term, continuous solar-driven produc­tion and, lacking some kind of long-term thermal storage, will require some kind […]

The techniques of nonimaging optics are particularly valuable in space or lunar environments in which the use of solar thermal energy has obvious advantages. Earlier preliminary studies have ex­plored this concept for the production of cement from lunar regolith and for solar thermal propulsion in space. For example, extremely high temperatures, in the range of […]

From the earliest development of these nonimaging devices, when it became apparent that the thermodynamic limit on concentration could be approached, it was appealing to consider how one might practically develop very high levels of concentrated solar flux, in principle approaching even those found on the surface of the sun. However, pursuit of such objectives […]

It must be emphasized that this is a preliminary study. The assumptions on which it is based are very idealized. For instance, the treatment of the incident angular distribution as a pillbox and the requirement that the secondary and target be sized so as to achieve 100% intercept are somewhat extreme. In practice, the optical […]

A preliminary analysis of various performance trade-offs involved in designing a two-stage central receiver plant secondary to achieve ultrahigh concentrations using a nonimaging CPC type has been carried out. The approach was based on simple geometry and the optical characteristics of CPCs. We find that the highest possible concentrations can only be achieved with an […]

The approach is based on simple geometry and the optical characteristics of CPCs. The goals are (1) to fill the field of view of the CPC as much as possible and (2) to identify those design factors (a)   (b)   FIGURE 9.1: (a) The simplest geometry for a two-stage central receiver is a central […]

9.1 CONCENTRATION LIMITS FOR NONIMAGING TERMINAL CONCENTRATORS IN Central RECEIVER APPLICATIONS 9.1.1 Introduction In this chapter, a preliminary analysis that carries out various performance trade-offs involved in the design of a two-stage central receiver plant that could achieve ultrahigh concentrations with a nonimaging CPC type secondary is presented. It should be noted that the study […]